CR
Cryospheric Sciences

Mass balance

Image of the Week — Quantifying Antarctica’s ice loss

Fig. 1 Cumulative Antarctic Ice Sheet mass change since 1992. [Credit: Fig 2. from The IMBIE team (2018), reprinted with permission from Nature]

It is this time of the year, where any news outlet is full of tips on how to lose weight rapidly to  become beach-body ready. According to the media avalanche following the publication of the ice sheet mass balance inter-comparison exercise (IMBIE) team’s Nature paper, Antarctica is the biggest loser out there. In this Image of the Week, we explain how the international team managed to weight Antarctica’s ice sheet and what they found.


Estimating the Antarctic ice sheet’s mass change

There are many ways to quantify Antarctica’s mass and mass change and most of them rely on satellites. In fact, the IMBIE team notes that there are more than 150 papers published on the topic. Their paper that we highlight this week is remarkable in that it combines all the methods in order to produce just one, easy to follow, time series of Antarctica’s mass change. But what are these methods? The IMBIE team  used estimates from three types of methods:

  •  altimetry: tracking changes in elevation of the ice sheet, e.g. to detect a thinning;
  •  gravimetry: tracking changes in the gravitational pull caused by a change in mass;
  •  input-output: comparing changes in snow accumulation and solid ice discharge.

To simplify, let’s imagine that you’re trying to keep track of how much weight you’re losing/gaining. Then  altimetry would be like looking at yourself in a mirror, gravimetry would be stepping on a scale, and input-output would be counting all the calories you’re taking in and  burning out. None of these methods will tell you directly whether you have lost belly fat, but combining them will.

The actual details of each methods are rather complex and cover more pages than the core of the paper, so I invite you to read them by yourself (from page 5 onwards). But long story short, all estimates were turned into one unique time series of ice sheet mass balance (purple line on Fig. 1). Furthermore, to understand how each region of Antarctica contributed to the time series, the scientists also produced one time series per main  Antarctic region (Fig. 2): the West Antarctic Ice Sheet (green line), the East Antarctic Ice Sheet (yellow line), and the Antarctic Peninsula (red line) .

Antarctica overview map. [Credit: NASA]

Antarctica is losing ice

The results are clear: the Antarctic ice sheet as a whole is losing mass, and this mass loss is accelerating. Nearly 3000 Giga tonnes since 1992. That is 400 billion elephants in 25 years, or on average 500 elephants per second.

Most of this signal originates from West Antarctica, with a current trend of 159 Gt (22 billion elephants) per year. And most of this West Antarctic signal comes from the Amundsen Sea sector, host notably to the infamous  Pine Island  and Thwaites Glaciers.

The Antarctic ice sheet has lost “400 billion elephants in 25 years”

But how is the ice disappearing? Rather, is the ice really disappearing, or is there simply less ice added to Antarctica than ice naturally removed, i.e. a change in surface mass balance? The IMBIE team studied this as well. And they found that there is no Antarctic ice sheet wide trend in surface mass balance; in other words Antarctica is shrinking because more and more ice is discharged into the ocean, not because it receives less snow from the atmosphere.

Floating ice shelf in the Halley embayment, East Antarctica [Credit: Céline Heuzé]

What is happening in East Antarctica?

Yet another issue with determining Antarctica’s weight loss is Glacial Isostatic Adjustment. In a nutshell, ice is heavy, and its weight pushes the ground down. When the ice disappears, the ground goes back up, but much more slowly than the rate of ice melting . This process has been ongoing in Scandinavia notably since the end of the last ice age 21 000 years ago, but it is also happening in East Antarctica by about 5 to 7 mm per year (more information here). Except that there are very few on site GPS measurements in Antarctica to determine how much land is rising, and the many estimations of this uplifting disagree.

So as summarised by the IMBIE team, we do not know yet what the change in ice thickness is where glacial isostatic adjustment is strong, because we are unsure how strong this adjustment is there. As a result in East Antarctica, we do not know whether there is ice loss or not, because it is unclear what the ground is doing.

What do we do now?

The IMBIE team concludes their paper with a list of required actions to improve the ice loss time series: more in-situ observations using airborne radars and GPS, and uninterrupted satellite observations (which we already insisted on earlier).

What about sea level rise, you may think. Or worse, looking at our image of the week, you see the tiny +6mm trend in 10 years and think that it is not much. No, it is not. But note that the trend is far from linear and has been actually accelerating in the last decades…

 

Reference/Further reading

The IMBIE Team, 2018. Mass balance of the Antarctic Ice Sheet from 1992-2017. Nature 558, 219–222.

Edited by Sophie Berger

Image of the Week – Antarctica: A decade of dynamic change

Fig. 1 – Annual rate of change in ice sheet height attributable to ice dynamics. Zoomed regions show (a) the Amundsen Sea Embayment and West Marie Byrd Land sectors of West Antarctica, (b) the Bellingshausen Sea Sector including the Fox and Ferrigno Ice Streams and glaciers draining into the George VI ice shelf and (c) the Totten Ice Shelf. The results are overlaid on a hill shade map of ice sheet elevation from Bedmap2 (Fretwell et al. 2013) and the grounding line and ice shelves are shown in grey (Depoorter et al. 2013). [Credit: Stephen Chuter]

  

Whilst we tend to think of the ice flow in Antarctica as a very slow and steady process, the wonders of satellites have shown over the last two decades it is one of the most dynamic places on Earth! This image of the week maps this dynamical change using all the satellite tools at a scientist’s disposal with novel statistical methods to work out why the change has recently been so rapid.


Why do we care about dynamic changes in Antarctica ?!

The West Antarctic Ice Sheet has the potential to contribute an approximate 3.3 m to global sea level rise (Bamber et al. 2009). Therefore, being able to accurately quantify observed ice sheet mass losses and gains is imperative for assessing not only their current contribution to the sea level budget, but also to inform ice sheet models to help better predict future ice sheet behaviour.

An ice sheet can gain or lose mass primarily through two different processes:

  • changes in surface mass balance (variations in snowfall and surface melt driven by atmospheric processes) or
  • ice dynamics, which is where variations in the flow of the ice sheet (such as an increase in its velocity) leads to changes in the amount of solid ice discharged from the continent into the ocean. In Antarctica ice flow dynamics are typically regulated by the ice shelves that surround the ice sheet; which provide a buttressing stress to help hold back the rate of flow.

Understanding the magnitude of each of these two components is key to understanding the external forcing driving the observed ice sheet changes.

This Image of the Week shows the annual rates of ice sheet elevation change which are attributed to changes in ice dynamics between 2003 and 2013 (Fig. 1) (Martín-Español et al. 2016). This is calculated by combining observations from multiple satellites (GRACE, ENVISAT, ICESat and CryoSat-2) with in-situ GPS measurements in  a Bayesian Hierarchical Model. The challenge we face is that the observations we have of ice sheet change (whether that being total height change from altimetry or mass changes from GRACE) vary on their spatial and temporal scales and can only tell us the total mass change signal, not the magnitudes or proportions of the underlying processes driving it. The Bayesian statistical approach used here takes these observations and separates them proportionally into their most likely processes, aided by prior knowledge of the spatial and temporal characteristics for each process we want to resolve. This allows us reducing the reliance on using forward model outputs to resolve for processes we cannot observe. As a result, it is unique from other methods of determining ice sheet mass change, which rely on model outputs which in some cases have hard to quantify uncertainties.  This methodology has been applied to Antarctica and is currently being used to resolve the sea level budget and its constituent components through the ERC GlobalMass project.

What can we learn from Bayesian statistical approach?

This approach firstly allows us to quantitively assess the annual contribution that the Antarctic ice sheet is making to the global sea level budget, which is vital to better understanding the magnitude each Earth system process is playing in sea level change. Additionally, by being able to break down the total change into its component processes, we can better understand what external factors are driving this change. Ice dynamics has been the dominant component of mass loss in recent years over the West Antarctic Ice Sheet and is therefore the process being focussed on in this image.

Amundsen Sea Embayment : a rapidly thinning area

Since 2003 there have been major changes in the dynamic behaviour over the Amundsen Sea Embayment and West Marie Byrd Land region (Fig 1, inset a). This region is undergoing some of the most rapid dynamical changes across Antarctica, with a 5 m/yr ice dynamical thinning near the outlet of the Pope and Smith Glacier. Additionally the Bayesian hierarchical model results show that dynamic thinning has spread inland from the margins of Pine Island Glacier, agreeing with elevation trends measured by satellite altimetry over the last two decades (Konrad et al. 2016).

These changes are driven primarily by the rapid thinning of the floating ice shelves at the ice sheet margin in this region

The importance of ice dynamics  is also illustrated in Fig 2, which shows  surface processes and ice dynamics components of mass changes over the Amundsen Sea Embayment from the bayesian hierarchical model. Fig 2 demonstrates that ice dynamics is the primary driver of mass losses in the region. Ice dynamic mass loss increased dramatically from 2003-2011, potentially stabilising to a new steady state since 2011.

Fig. 2 – Annual mass changes due to ice dynamics (pink line) and SMB (blue line) for the period 2003-2013 from the Bayesian hierarchical model approach. Red dots represent mass change anomaly (changes from the long term mean) due to surface mass balance calculated by the RACMO2.3 model and allow for comparison with our Bayesian framework results. (calculated from observations of ice velocity and ice thickness at the grounding line and allow for comparison with our Bayesian framework results (Mouginot et al, 2014). [Credit: Fig. 9b from Martín-Español et al., 2016].

 

The onset of  dynamic thinning can also be seen in glaciers draining into the Getz Ice Shelf, which is experiencing high localised rates of ice shelf thinning up to 66.5 m per decade (Paolo et al. 2015) . This corroborates with ice speed-up recently seen in the region (Chuter et al. 2017; Gardner et al. 2018). We have limited field observations of ice characteristics in this region and therefore more extensive surveys are required to fully understand causes of this dynamic response.

Bellingshausen Sea Sector :  Not as stable as previously thought…

 The Bellingshausen Sea Sector (Fig 1, inset b) was previously considered relatively a dynamically stable section of the Antarctic coastline, however recent analysis from a forty year record of satellite imagery has shown that the majority of the grounding line in this region has retreated  (Christie et al. 2016). This is reflected in the presence of a dynamic thinning signal in the bayesian hierarchical model results near the Fox and Ferrigno Ice streams and over some glaciers draining into the George VI ice shelf, which have been observed from CryoSat-2 radar altimetry (Wouters et al. 2015). The dynamic changes in this region over the last decade highlight the importance of continually monitoring all regions of the ice sheet with satellite remote sensing in order to understand the what the long term response over multiple decades is to changes in the Earth’s climate and ocean forcing.

Outlook

Multiple  satellite missions have allowed us to measure changes occurring across the ice sheet in unprecedented detail over the last decade. The launch of the GRACE-Follow On mission earlier this week and the expected launch of ICESat-2 in September will ensure this capability continues well into the future. This will provide much needed further observations to allow us to understand ice sheet dynamics over time scales of multiple decades. The bayesian hierarchical approach being demonstrated will be developed further to encompass these new data sets and extend the results into the next decade. In addition to satellite measurements, the launch of the International Thwaites Glacier Collaboration  between NERC and NSF will provide much needed field observations for the Thwaites Glacier region of the Amundsen Sea Embayment, to better understand whether it has entered a state of irreversible instability .

Data
The  Bayesian hierarchical model mass trends shown here (Martín-Español et al. 2016) are available from the UK Polar Data Centre. In addition, the time series has been extended until 2015 and is available on request from Stephen Chuter (s.chuter@bristol.ac.uk). This work is part of the ongoing ERC GlobalMass project, which aims to attribute global sea level rise into its constituent components using a Bayesian Hierarchical Model approach. The GlobalMass project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 69418.

References

Christie, Frazer D. W. et al. 2016. “Four-Decade Record of Pervasive Grounding Line Retreat along the Bellingshausen Margin of West Antarctica.” Geophysical Research Letters 43(11): 5741–49. http://doi.wiley.com/10.1002/2016GL068972.

Chuter, S.J., A. Martín-Español, B. Wouters, and J.L. Bamber. 2017. “Mass Balance Reassessment of Glaciers Draining into the Abbot and Getz Ice Shelves of West Antarctica.” Geophysical Research Letters 44(14).

Gardner, Alex S. et al. 2018. “Increased West Antarctic and Unchanged East Antarctic Ice Discharge over the Last 7 Years.” Cryosphere 12(2): 521–47.

Martín-Español, Alba et al. 2016. “Spatial and Temporal Antarctic Ice Sheet Mass Trends, Glacio-Isostatic Adjustment, and Surface Processes from a Joint Inversion of Satellite Altimeter, Gravity, and GPS Data.” Journal of Geophysical Research: Earth Surface 121(2): 182–200. http://dx.doi.org/10.1002/2015JF003550.

Mouginot, J, E Rignot, and B Scheuchl. 2014. “Sustained Increase in Ice Discharge from the Amundsen Sea Embayment, West Antarctica, from 1973 to 2013.” Geophysical Research Letters 41(5): 1576–84.

Paolo, Fernando S, Helen A Fricker, and Laurie Padman. 2015. “Volume Loss from Antarctic Ice Shelves Is Accelerating.” Science 348(6232): 327–31. http://www.sciencemag.org/content/early/2015/03/31/science.aaa0940.abstract.

Edited by Violaine Coulon and Sophie Berger


Stephen Chuter is a post-doctoral research associate in Polar Remote Sensing and Sea Level at the University of Bristol. He combines multiple satellite and ground observations of ice sheet and glacier change with novel statistical modelling techniques to better determine their contribution to the global sea level budget. He tweets as @StephenChuter and can be found at www.stephenchuter.wordpress.com. Contact email: s.chuter@bristol.ac.uk

Image of the Week – A new way to compute ice dynamic changes

Fig. 1: Map of ice velocity from the NASA MEaSUREs Program showing the region of Enderby Land in East Antarctica [Credit: Fig. 1 from Kallenberg et al. (2017) ].

Up to now, ice sheet mass changes due to ice dynamics have been computed from satellite observations that suffer from sparse coverage in time and space. A new method allows us to compute these changes on much wider temporal and spatial scales. But how does this method work? Let us discover the different steps by having a look at Enderby Land in East Antarctica, for which ice velocities are shown in our Image of the Week…


Mass balance of ice sheets

The mass balance of an ice sheet is the difference between the mass gain of ice, primarily through snowfall, and the mass loss of ice, primarily via meltwater runoff and ice dynamic processes (e.g. iceberg calving, melting below ice shelves). When the mass gain is equal to the mass loss, the ice sheet is in balance. However, if one exceeds the other, the ice sheet either gains or loses mass.

Measuring mass balance changes of ice sheets is crucial due to their potential contribution to sea level rise (see previous post). You can have a look at this nice review for further details about the recent changes in the mass balance of the two biggest ice sheets on Earth, i.e. Antarctica and Greenland.

Ice mass changes from snowfall and meltwater runoff (what we call ‘surface mass balance’ changes) are reasonably well simulated by regional climate models, which give good agreement with observations (see this study for Antarctica and this one for Greenland). Mass changes from ice dynamics are more complex to obtain. They are commonly estimated by combining ice velocity and ice thickness. Ice velocity is measured via satellite radar interferometry, while ice thickness is obtained thanks to airborne radar. Unfortunately, these measurements have sparse temporal and spatial coverage, especially in Antarctica, which makes the computation of mass changes from ice dynamics challenging.

A new method to estimate ice dynamic changes

Kallenberg et al. (2017) conducted a study focussing on Enderby Land in East Antarctica (see our Image of the Week) in which they use a novel approach to estimate ice dynamic changes. This region of Antarctica has experienced a slightly positive mass balance in past years, meaning that the ice sheet has slightly thickened in this region.

Kallenberg et al. (2017) first used satellite observations to compute the total changes in ice sheet mass. They took advantage of two high-technology datasets. The first one, “Gravity Recovery And Climate Experiment” (GRACE), measures changes in the Earth’s gravity field, from which ice mass changes can be derived. A summary explaining how GRACE works can be found in this previous post. The second satellite dataset, “Ice, Cloud, and land Elevation Satellite” (ICESat), measures changes in ice surface elevation, from which changes in ice mass can be computed by using ice density.

However, Kallenberg et al. (2017) were not interested in the total ice mass changes, as obtained from GRACE and ICESat satellites, but rather in ice dynamic changes. They subtracted two quantities from the total mass changes in order to obtain the remaining dynamic changes:

  1. Surface mass balance changes: changes from processes happening at the surface of the ice sheet (e.g. snow accumulation, meltwater runoff). These changes were obtained from model simulations using the Regional Atmospheric Climate Model (RACMO2), for which details can be found in this previous post.
  2. Glacial Isostatic Adjustment: changes in land topography due to ice loading and unloading. These changes were computed from Glacial Isostatic Adjustment models.

What does this study tell us?

The results of this study show that it is possible to compute changes in ice mass resulting from ice dynamics with higher spatial and temporal coverage than before, using a combination of satellite observations and models.

Also, the use of two different satellite datasets (GRACE and ICESat) shows that they agree quite well with each other in the region of Enderby Land (see Fig. 2). This means that using one or the other dataset does not make a big difference.

Finally, this new method also shows that differences between GRACE and ICESat reduce when using the newer version of RACMO2 for computing surface mass balance changes. This tells us that comparing results of ice dynamics from both satellites with different models is a good way to identify which models correctly simulate surface processes and which models do not.

Fig. 2: Ice dynamic changes (dH/dt, where H is ice thickness and t is time) computed from (a) GRACE and (b) ICESat and expressed in meters per year [Credit: Fig. 5 from Kallenberg et al. (2017) ].

Further reading

Edited by Clara Burgard and Emma Smith


David Docquier is a post-doctoral researcher at the Earth and Life Institute of Université catholique de Louvain (UCL) in Belgium. He works on the development of processed-based sea-ice metrics in order to improve the evaluation of global climate models (GCMs). His study is embedded within the EU Horizon 2020 PRIMAVERA project, which aims at developing a new generation of high-resolution GCMs to better represent the climate.

Image of The Week – The Pulsating Ice Sheet!

Image of The Week – The Pulsating Ice Sheet!

During the last glacial period (~110,000-12,500 years ago) the Laurentide Ice Sheet (North America) experienced rapid, episodic, mass loss events – known as Heinrich events. These events are particularly curious as they occurred during the colder portions of the last glacial period, when we would intuitively expect large-scale mass loss during warmer times. In order to understand mass loss mechanisms from present-day ice sheets we need to understand what happened in the past. So, how can we better explain Heinrich events?


What are Heinrich Events?

During a Heinrich event large swarms of icebergs were discharged from the Laurentide Ice Sheet into the Hudson Strait and eventually into the North Atlantic Ocean. This addition of fresh water to the oceans caused a rise in sea level and a change in ocean currents and therefore climate.

We know about these events by studying glacial debris that was transported from the ice sheet into the oceans by the icebergs and eventually deposited on the ocean floor. From studying ocean-sediment records we know that Heinrich events occurred episodically during the last glacial period but not on at a regular intervals. Interestingly, when compared to temperature records from Greenland ice cores, it can be seen that the timing of Heinrich events coincides with the cold phases of Dansgaard–Oeschger (DO) cycles – rapid temperature fluctuations which occurred during the last glacial period (see our previous post).

the timing of Heinrich events coincides with the cold phases of Dansgaard–Oeschger (DO) cycles

What do we think causes them?

A new study, published last month in Nature, uses numerical modelling to show how pulses of warm ocean water could trigger Heinrich events. Our image of the week (Figure 1) illustrates the proposed mechanism for one event cycle:

  • a) Ice sheet at it’s full extent, grounded on a sill (raised portion of the bed, at the mouth of the Hudson Strait). Notice the sill is around 300m below sea level at this time.
  • b) A pulse of sub-surface water (purple) warms by a few degrees, encouraging iceberg calving at the glacier front and causing the ice begin to retreat from the sill.
  • c) As the ice retreats, it becomes unstable due to an inwards sloping bed (see our previous post on MISI). This leads to sudden rapid retreat of the ice – characteristic of Heinrich events.
  • d) Due to ice loss and thus less mass depressing the bed, the bed will slowly rise (Glacial Isostatic Adjustment), eventually the sill has risen to a level which cuts off the warmer water from the ice front and the ice can slowly advance again.

Once the ice has advanced back to it’s maximum extent (a) it will slowly depress the bed again, allowing deeper, warmer water to reach the ice front and the whole cycle repeats!

The authors of this study used this model to simulate Heinrich events over the last glacial period and were able to accurately predict the timing of Heinrich events, as known from ocean sediment records. Check out this video to see the model in action!!

Why is it important?

This study shows that the proposed mechanism probably controlled the onset of rapid mass-loss Heinrich events in the past and more generally that such mechanisms can cause the rapid retreat of marine terminating glaciers. This is important as it adds to our understanding of the stability (or instability) of present day marine terminating glaciers – such as the West Antarctic Ice Sheet! If such rapid mass loss happened regularly in the past we need to know if and how it might happen in the future!

such mechanisms can cause the rapid retreat of marine terminating glaciers.


Check out the full study and the news article summarising the findings here:

Image of the Week – Icelandic glaciers monitored from space!

Image of the Week – Icelandic glaciers monitored from space!

Located in the North Atlantic Ocean, just south of the polar circle, Iceland is a highly fascinating land. Covered by some of the largest glaciers in Europe and hosting active volcanoes, geothermal sites and subglacial lakes, it is extremely dynamic in nature and ever changing. With this Image of the Week we will tell you a bit about the changing ice caps of Iceland and how we can monitor them from space!


Icelandic ice caps since the mid-1990s

Iceland enjoys a mild and moist climate because of the relatively warm and saline Irminger current transporting heat to its southern coast, although the cold East Greenland and East Icelandic currents may cause sea ice to form to the north. Iceland’s ice caps, which receive abundant precipitation from North Atlantic cyclones, cover about 11% of the land, and contain ~3600 km2 of ice. If they completely melted they would contribute 1 cm to Sea Level Rise (SLR).

In the period 1995-2010, Icelandic glaciers shrank every year and lost mass at an average rate of 9.5±1.5 Gton a-1 – generally reflecting higher summer temperatures and longer melting seasons than in the early 1990s (Björnsson et al., 2013). Importantly, in recent decades Iceland has been the second largest source of glacier meltwater to the North Atlantic after Greenland and its peripheral glaciers. Furthermore, surge-type outlet glaciers – which have unpredictable dynamics – are present in all Icelandic ice caps and represent as much as 75% of the area of Vatnajökull (Bjornsson et al., 2003), the largest ice cap in Europe by volume. Therefore, it is important to continuously monitor Icelandic ice caps (>90% of the whole glaciated area) at high spatial resolution. Glaciological field surveys can yield accurate measurements and are routinely performed in Iceland on all ice caps and most glaciers. However, it is not always feasible to use field methods, depending on the remoteness and size of the glacier (e.g. several glaciers and ice caps in the Arctic). Continuous monitoring of such hardly accessible areas can be achieved from space at high spatial resolution.

Continuous health check from space

Since 2010, the ESA CryoSat-2 (CS2) mission has been fundamental in retrieving ice elevation data over glacial terrain characterised by complex topography and steep slopes – notoriously hard to monitor via satellite. CS2’s radar altimeter provides the elevation of the Point-Of-Closest-Approach (POCA) – the point at the surface closest to the satellite on a straight line – every ~400 m along the flight track. The main novelty of this mission is the use of a second antenna, which allows the use of interferometry across-track to accurately infer the location of a surface reflection in presence of a slope (read more about it here). Additionally, a new and exciting application of CS2 interferometric capabilities is that we can exploit the echos after the POCA, i.e. the reflections coming from the sloping surface moments after the first one. This approach generates a swath of elevations every ~400 m and provides up to two orders of magnitude more elevation data than with conventional POCA processing (Fig. 2; Gray et al., 2013, Foresta et al., 2016).

Since 2010, the ESA CryoSat-2 (CS2) mission has been fundamental in retrieving ice elevation data

Figure 2: Example of the improved elevation data using CS2 swath-processing. CS2 swath data (colors) and conventional (circles) heights over the Austfonna ice cap (Svalbard) for two satellite passes. Swath processing delivers up to two orders of magnitude more elevation data. [Credit: Dr. N. Gourmelen,University of Edinburgh, School of GeoSciences]

This rich dataset can be used to generate maps of surface elevation change rates at sub-kilometer resolution (Figs. 1 and 3). These maps show extensive thinning of up to -10 m a-1 in marginal areas of Iceland’s ice caps, while patterns of change are more variable in their interior. Fig. 3 shows the difference in spatial coverage between the POCA and Swath approaches, with the former sampling preferentially along topographic highs (see for example the Langjökull ice cap in Fig. 3). Using these high resolution maps, it is possible to independently infer the mass balance of each ice cap purely from satellite altimetry data. Based on CS2 swath-processed elevations, between glaciological years 2010/11 and 2014/15 Iceland has lost mass at an average rate of 5.8±0.7 Gton a-1 contributing 0.016±0.002 mm a-1 to SLR (Foresta et al., 2016). The rate of mass loss is ~40% less than during the preceding 15 years, partly caused by Vatnajökull (63% of the total mass loss) having had positive mass balance during the glaciological year 2014/15 due to anomalously high precipitation. Langjökull, with widespread thinning up to the ice divide (Figs. 1 and 3), is the fastest changing ice cap in terms of mass loss per unit area.

between glaciological years 2010/11 and 2014/15 Iceland has lost mass at an average rate of 5.8±0.7 Gton a-1 contributing 0.016±0.002 mm a-1 to SLR

Beside estimating mass change at the ice cap scale, the novel swath approach demonstrates the capability to observe glaciological processes at a sub-catchment scale. Different accumulation and thinning patterns over Vatnajökull and Langjökull, for example, are directly related to past surges or subglacial volcanic eruptions, some of which happened decades ago. Their long term lingering effects on the ice cap topography are now visible from space and as the satellite data record extends we will be able to gain an increased understanding of how these effects evolve over time.

Figure 3 – Comparison between swath-processed (Swath) and conventional (POCA) surface elevation change rates over the six largest ice caps in Iceland, representing 90% of the glaciated area. V (Vatnajökull), L (Langjökull),H(Hofsjökull),M(Mýrdalsjökull), D (Drangajökull), and E (Eyjafjallajökull). The inset shows the location of individual elevation measurements by using Swath and POCA approaches over Langjökull. [Credit: After Foresta et al. (2016).]

Edited by Emma Smith


Luca Foresta is a PhD student in the Glaciology and Cryosphere Research Group at the University of Edinburgh (@EdinGlaciology), and his research focuses on improving CryoSat-2 processing as well as exploiting swath-processed CryoSat-2 data to quantify surface, volume and mass changes over ice caps.

 

Image of the Week – Inside a Patagonian Glacier

Image of the Week – Inside a Patagonian Glacier

Chilean Patagonia hosts many of the most inhospitable glaciers on the planet – in areas of extreme rainfall and strong winds. These glaciers are also home to some of the most spectacular glacier caves on Earth, with dazzlingly blue ice and huge vertical shafts (moulins). These caves give us access to the heart of the glaciers and provide an opportunity to study the microbiology and water drainage in these areas; in particular how this is changing in relation to climate variations. Our image of this week shows the entrance to one of these caves on Grey Glacier in the Torres del Paine National Park.


“Glacier karstification”

Glaciers in Patagonia are “temperate”, which means that the ice temperature is close to the melting point. As glacial melt-water runs over the surface of this “warm” ice it can easily carve features into ice, which are similar to those formed by limestone dissolution in karstic landscapes. Hence, this phenomenon is called Glacier karstification. It is this process that forms many of the caves and sinkholes that are typically found on temperate glaciers.

From the morphological (structural) point of view, glaciers actually behave like karstic areas, which is rather interesting for a speleologist (scientific cave explorer). Besides caves and sinkholes one often finds other shapes similar to karstic landscapes. For example, small depressions on the ice surface formed by water gathering in puddles, whose appearance resembles small kartisic basins (depressions). Of all the features formed by glacier karstification glacier caves are the most important from a glaciological perspective.

Glacier caves can be divided in two main categories:

  • Contact caves – formed between the glacier and bed underneath; or at the contact between extremely cold and temperate ice by sublimation processes (Fig. 2a)
  • Englacial caves – form inside the glacier – as shown in our image of the week today. Most of these caves are formed by runoff, where water enters the glacier through a moulin (vertical shaft) and are the most interesting for exploration and research (Fig. 2b)
Figure 2: Two different types of caves explored on the Grey Glacier. A- Contact formed between the glacier bed and overlying ice [Credit: Tommaso Santagata]. B- Entrance to an englacial cave [Credit: Alessio Romeo/La Venta].

Figure 2: Two different types of caves explored on the Grey Glacier. A- Contact formed between the glacier bed and overlying ice [Credit: Tommaso Santagata]. B- Entrance to an englacial cave [Credit: Alessio Romeo/La Venta].

Exploring the moulins of a Patagonian glacier

Located in the Torres del Paine National Park area (see Fig. 3), the Grey glacier was first explored in 2004 by the association La Venta Esplorazioni Geografiche. In April of this year, a team of speleologists went back to the glacier to survey the evolution of the glacier.

Figure 3: Map of Grey Glacier with survey site of 2004 and 2016 indicated by red dot [Adapted from: Instituto Geografico Militar de Chile ]

Figure 3: Map of Grey Glacier with survey site of 2004 and 2016 indicated by red dot [Adapted from: Instituto Geografico Militar de Chile ]

Grey glacier begins in the Andes and flows down to it’s terminus in Grey Lake, where it has three “tongues” which float out into the water (Fig, 3). As with many other glaciers, Grey Glacier is retreating, though mass loss is less catastrophic than some of Patagonia’s other glaciers (such as the Upsala – which is glaciologically very similar to the Grey Glacier). Grey Glacier has retreated by about 6 km over the last 20 years and has thinned by an average of 40 m since 1970.

In 2004 research was concentrated on the tongue at the east of this Grey Glacier (Fig. 3 – red dot), which is characterised by a surface drainage network with small-size surface channels that run into wide moulin shafts, burying into the glacier. In this latest expedition, the same area was re-examined to see how it had changed in the last 12 years.

Several moulins were explored during the 2016 expedition, including a shaft of more than 90 m deep and some horizontal contact caves (Fig 2). The glacier has clearly retreated and the surface has lowered a lot from the 2004 expedition. The extent of the thinning in recent years can be easily measured on the wall of the mountains around the glacier. Interestingly the entrance to the caves which were explored in 2004 and in 2016 was in the same position as 12 years ago, although the reasons for this are not yet clear.

The entrance of two of the main moulins which were explored were also mapped in 3D using photogrammetry techniques (see video below). The 3D models produced help us to better understand the shape and size of these caves and to study their evolution by repeating this mapping in the future. For more information about the outcome of this expedition, please follow the Inside the Glaciers Blog.

 

 

Further Reading:

Books on the subject:

  • Caves of the Sky: A Journey in the Heart of Glaciers, 2004, Badino G., De Vivo A., Piccini L.
  • Encyclopaedia of Caves and Karst Science, 2004, Editor: Gunn J.

Edited by Emma Smith and Sophie Berger


tom_picTommaso Santagata is a survey technician and geology student at the University of Modena and Reggio Emilia. As speleologist and member of the Italian association La Venta Esplorazioni Geografiche, he carries out research projects on glaciers using UAV’s, terrestrial laser scanning and 3D photogrammetry techniques to study the ice caves of Patagonia, the in-cave glacier of the Cenote Abyss (Dolomiti Mountains, Italy), the moulins of Gorner Glacier (Switzerland) and other underground environments as the lava tunnels of Mount Etna. He tweets as @tommysgeo

Image of the Week – Hidden Beauty on a Himalayan Glacier

Image of the Week –  Hidden Beauty on a Himalayan Glacier

Today’s image of the week comes from stunning setting of Chhota Shigri Glacier in the Pir Panjal Range of northern India. The range is part of the Hindu-Kush Karakorum Himalaya region which is a notoriously challenging place to work as it is very remote and completely inaccessible during the winter months. However, when have these challenges ever stopped a hardy glaciologist?! 

Our image this week was taken during a field expedition as part of an ongoing long term monitoring program in the area and today we are going to tell you why the region is so important (other than being the source of some rather good photos!)


Why is monitoring glaciers in the Himalaya so important?

Location of Chhota Shigri Glacier taken from Wagon et al., 2007

The Hindu-Kush Karakorum Himalaya region is made up of the biggest mountain ranges on Earth which contain the largest ice mass outside of the polar regions. This region provides water to 50-60% of the world’s population (Wagon et al., 2007), some of which comes from glacial melt water, therefore it is critical to understand how the glaciers in this region may respond to ongoing climate change and predict the impact this may have for the future. As glaciers are very sensitive to changing climate they are also used to understand climate variations at annual and decadal timescales in the region.

Chhota Shigri Glacier is representative of many glaciers in this region and was chosen as the site for a long-term monitoring program in 2002. It was chosen for a number of reasons including previous field studies on the glacier in the 1980s,  glacier geometry, accessibility and its dynamic environment; with areas of partial debris cover and supraglacial lakes (as seen in the image above). The data record on this glacier now continuously spans 13 years and the program has become a benchmark for studying Himalayan glaciers.

What do we see on the picture

The beautiful shot shows a supraglacial lake, a pond of liquid water, on the top of the Chhota Shigri Glacier. This supraglacial lake is an ephemeral lake, forming immediately after winter season. Supraglacial lakes form due to the melting of snow/ice and their presence helps to determine surface melt rates. When the lake water drains it also allows the distribution of subsurface hydrological conduits to be investigated. If the lake does not drain and exists long term there may be glacial lake outburst floods. These are a natural hazard and must be monitored and better understood. This is just one of the aspects of Chhota Shigri Glacier that is being investigated by the long term monitoring program.

Chhota Shigri Glacier has the longest monitoring record

The long term monitoring program, initiated on Chhota Shigri Glacier in 2002, has recorded the evolution of mass balance, ice velocity, ice thickness, stream runoff and melt water quality. The program is a joint collaboration between India and France under the frame work of DST/CEFIPRA programme at School of Environmental Science, Jawaharlal Nehru University, New Delhi. Presently, the annual and seasonal mass balance series (13 years) of Chhota Shigri glacier since 2002 is the longest continuous record in the entire Hindu-Kush Karakorum Himalaya region and represents a benchmark for climate change studies in this region. To measure the annual and seasonal mass balance, we survey the glacier at the end of winter season (May/June) for winter balance measurements and end of summer (September end/October) for annual measurements. We monitor a network of ablation stakes distributed throughout the entire ablation zone (including debris-covered area) to estimate the glacier-wide ablation. To estimate the accumulation we drill snow cores or dig snow pits at representative locations within the accumulation zone (>5150 m) of Chhota Shigri Glacier. For more detailed information and the results of this monitoring see Azam et al. (2016) and Ramanathan (2012).

Long term monitoring on Chhota Shigri Glacier (a) accumulation zone at the end of summer (area is largely covered in dust with clearly visible medial moraine . (b) accumulation zone at the end of winter (fresh snow cover), (c) ablation stake (bamboo) installation in a partly debris covered region during the summer and, (d) drilling of snow core at top of the glacier during winter (Credit: Arindan Mandal/JNU).

Long term monitoring on Chhota Shigri Glacier (a) accumulation zone at the end of summer (area is largely covered in dust with clearly visible medial moraine . (b) accumulation zone at the end of winter (fresh snow cover). (c) ablation stake (bamboo) installation in a partly debris covered region during the summe. (d) drilling of snow core at top of the glacier during winter (Credit: Arindan Mandal).

 

Acknowledgements

Thanks to Department of Science and Technology, Govt. of India, SAC-ISRO, CEFIPRA, INDICE, GLACINDIA and CHARIS for funding our research. Special thanks to Emma and Sophie for help in putting together this post.

Edited by Emma Smith and Sophie Berger


Arindan_PhotoArindan Mandal is a PhD student at the School of Environmental Science, Jawaharlal Nehru university, New Delhi, India under the supervision of Prof. AL. Ramanathan. His current work is focused on Chhota Shigri Glacier where he is working to analyse the past and present state of mass balance in the changing climate scenario and also to understand the complex local scale meteorological processes that drive the mass balance of the glacier. He is working to develop a coupled distributed surface energy-balance model combined with various glaciological and hydrological aspect using in-situ dataset to understand the processes that govern and runoff at Chhota Shigri glacier pro-glacial stream and its sensitivity to the future climate. He tweets as @141Arindan.
Contact Email: arindan.141@gmail.com,

Image of the Week — Historical aerial imagery of Greenland

Image of the Week — Historical aerial imagery of Greenland

A few month ago, we were taking you on a trip back to Antarctic fieldwork 50 years ago, today we go back to Greenland during 1930s!

When geopolitics serves cryospheric sciences

The Permanent Court of International Justice in The Hague awarded Danish sovereignty over Greenland in 1933 and besides geopolitical interests, Denmark had a keen interest in searching for natural resources and new opportunities in this newly acquired colony. In the 1930s the Danish Government initiated three comprehensive expeditions; one of these, the systematic mapping of East Greenland, was set off by The Greenlandic Agency, The Marines’ air services, The Army’s Flight troops and Geodetic Institute. The Danish Marines provided pilots, mechanics, and three Heinkel seaplanes.

Danish expeditioner Lauge Koch, centre, along with his pilots all dressed in suits made from polar bear. (Credit: The Arctic Institute)

Danish expeditioner Lauge Koch, centre, along with his pilots all dressed in suits made from polar bear. (Credit: The Arctic Institute)

Aerial photography in the 1930s – practical constraints

The airplanes had three seats in an open cockpit. The pilot was seated in the front, the radio operator in the center and in the back the photographer – this seat was originally for the machine-gun operator.

At the outset, the idea was to take vertical images, but that was impossible at the time due to the height of the mountains and the limited capability of the aircraft to reach adequate heights. The airplanes couldn’t reach more than 4000 m – similar to the height of mountains in Greenland. Oblique images were therefore recorded. The reduced view of the terrain when photographing in oblique angles required many more flights than originally planned. The photographic films were processed immediately after each flight. 45,000 km were covered during the first season, which lasted about two and a half months. In the following years, each summer a flight covered parts of the Greenlandic coast. During the Second World War, the mapping was temporarily stopped due to safety reasons.

The aircraft had an open hole in the floor for the photographer, originally where the machine gunner would sit. (Credit: The Arctic Institute)

The aircraft had an open hole in the floor for the photographer, originally where the machine gunner would sit.(Credit: The Arctic Institute)

An unexplored treasure trove of climate data

The tremendous volume of aerial images obtained from several expeditions and hundreds of flights not only constitutes the cornerstone of mapping in Greenland, but is invaluable data for studying climate change in these remote regions. The 1930s survey, compared to modern imagery, provides crucial insight into coastal changes, ice sheet mass balances, and glacier movement. Glacier fluctuations in southeast Greenland have been identified, showing that many land-terminating glaciers underwent a more rapid retreat in the 1930s than in the 2000s, whereas marine-terminating glaciers retreat more rapidly during the recent warming (Bjørk et al, 2012).

An ongoing project between the University of Copenhagen, INSTAAR (Institute of Arctic and Alpine Research) in Boulder, Colorado, and Natural History Museum of Denmark is currently focusing on analysing deltaic changes in Central and Southern Greenland; linking shoreline development to climate changes – these historic aerial images are essential for detecting such coastal evolution. However, there are still many other links between the past and present climate to be discovered from these images. Interested in hearing more about the project or the aerial images? Please contact Mette Bendixen (mette.bendixen@ign.ku.dk)

Bibliography

Bjørk, A. A., Kjær, K. H., Korsgaard, N. J., Khan, S. A., Kjeldsen, K. K., Andresen, C. S., … & Funder, S. (2012). An aerial view of 80 years of climate-related glacier fluctuations in southeast Greenland. Nature Geoscience, 5(6), 427-432. http://dx.doi.org/DOI:10.1038/ngeo1481

Edited by Alistair McConnell, Sophie Berger and Emma Smith


Mette BendixenMette Bendixen is s a PhD student at the Center for Permafrost in Copenhagen. She investigates the changing geomorphology of Greenlandic coasts, where climate changes can have huge impact on the local environment.

European Space Agency Living Planet Symposium 2016

European Space Agency Living Planet Symposium 2016

Living Planet Symposium

Between the 9th and 13th May, Prague played host to the European Space Agency’s (ESA) fourth Living Planet Symposium. The event, the largest in its history with over 3300 attendees, brought together the earth observation community across multiple disciplines to discuss significant scientific results and the future developments of earth observation missions. Earth Observation  of the Cryosphere over the last few decades has revolutionised our understanding of these regions, allowing us to monitor and assess ice sheet dynamics at unprecedented spatial and temporal scales.

ESA & Observation of the Cryosphere

The role of Earth Observation in Cryospheric sciences is set to increase further thanks to the European Commission and ESA Copernicus program; a series of satellites called Sentinels which all feature different sensor instrumentation, allowing researchers to monitor various aspects of the Earth System. The program will consist of 6 separate sentinel missions and will allow us to measure various Ice Sheet and Glacier dynamics continuously at a high temporal resolution. In addition, the Earth Explorer mission CryoSat-2 has been transforming our knowledge of the polar regions since it’s launch in 2010.

As a result, the conference had a wide range of exciting scientific results related to the Cryosphere from these missions; ranging from data products to be used by the community to the exploitation of mission data to further our knowledge of key processes and outstanding scientific questions.

Don’t worry if you weren’t able to make the symposium, as this post will highlight a selection of interesting results and the impact they will have on Cryospheric research!

CryoSat-2: Transforming Knowledge of the Cryosphere

CryoSat-2, an ESA Earth Explorer satellite that carries onboard a radar altimeter to measure ice elevation (Credit : ESA – P. Carril)

CryoSat-2, an ESA Earth Explorer satellite that carries onboard a radar altimeter to measure ice elevation (Credit : ESA – P. Carril)

CryoSat-2 is the ESA Earth Explorer radar altimetry mission dedicated to monitoring changes in surface elevation of earth’s ice sheets, sea-ice thickness and extent; which it has been routinely monitoring since November 2010. The combination of its unique polar orbital characteristics and novel dual antenna interferometric mode of operation has allowed it to overcome  many of the issues associated with previous altimetry missions over ice sheets.

Major results from CryoSat-2 included the application of swath processing techniques to the interferometric data to dramatically increase the number of surface elevation measurements available to researchers (Gray et al, 2013). Traditionally, the radar instrumentation would record a single elevation measurement at the point of closest approach (POCA) to the satellite. However, this technique analyses the whole radar return to produce measurements across the satellite footprint. By exploiting this increased data density it allows researchers to investigate ice sheet changes at much finer spatial and temporal resolution, allowing for an increase in the range of scientific questions the satellite is able to address. Examples of this include glacier thinning as a result of surging events that have previously occurred on time scales not possible to be captured by the satellite. It will also allow us to get a more complete picture of mass balance using the altimetry method.

Ice-shelf thickness in Antarctica

Furthermore, a contemporary continental ice shelf thickness dataset (Chuter and Bamber, 2015) derived from CryoSat-2 was presented; which provides large accuracy improvements over the previous ERS-1 derived dataset (Griggs and Bamber, 2011), particularly in the grounding zone, a key region for monitoring ice sheet stability. The results from this work will allow the community to improve accuracy in mass balance estimations from the input-output method, sub-ice shelf ocean modelling and for parameterisations in ice sheet models.

Ish_thick

Antarctic ice shelf thickness Derived from CryoSat-2 radar altimetry (Credit: subset of fig S1 from Chuter and Bamber, 2015). 

Monitoring sea ice

Sea ice monitoring is also a key mission objective, with the satellite already delivering on these aims through studies of continuous monitoring of the Arctic Sea Ice over the past five years.  Work presented at the symposium by Rachel Tilling (CPOM/University College London) makes use of the Near Real Time data products from ESA to deliver knowledge of sea ice thickness and extent as quick as two days after data acquisition, providing benefits to the shipping industry in addition to aiding arctic climate predictions (see also Tilling et al, 2015).

Antarctic mass balance

For the Antarctic ice sheet, mass balance estimates obtained from altimetry, gravimetry, and mass-budget methods can yield conflicting results with error bars that do not always overlap.

Some of these techniques use models to isolate and remove the effects of glacio-isostatic adjustment and surface mass balance (SMB) processes,  introducing another source of uncertainty which is hard to quantify.

a) Estimates of mass balance for the Amundsen Sea Embayment (ASE) sector in Antarctica from different techniques, including estimates from the RATES project. b) Estimates of the mass loss due to ice dynamics (red) and SMB (blue) for the ASE, compared with modeled values from RACMO2.3 (red dots) and ice discharge (blue line) (Credit: fig 9a from Martín-Español, et al. 2016)

a) Estimates of mass balance for the Amundsen Sea Embayment sector in West Antarctica from different techniques, including estimates from the RATES project. [IOM = Input-Output Method] b) Estimates of the mass loss due to ice dynamics (red) and Surface Mass Balance (SMB — blue) for the Amundsen Sea Sector, compared with modeled values from RACMO2.3 (red dots) and ice discharge (D — blue line) (Credit: fig 9 from Martín-Español et al. 2016)

To address both these issues, the RATES project presented a statistical modelling approach to the problem (Martin-Español et al., 2016). They combined the observational data (including satellite altimetry, GRACE, GPS and InSAR), and used prior information to separate out the mass balance signal into its main components.  For instance, we know that the glacio-isostatic adjustment has a large spatial length-scale, but  changes in ice dynamics may vary from one glacier to the next. We thus can `look’ for these components within the data and attribute them to the correct process. For the period 2003-2013, they estimated a mean mass balance rate of -82±23 Gt/yr with a sustained negative mean trend of dynamic imbalance to which West Antarctica is the largest contributor, mainly triggered by high thinning rates of glaciers draining into the Amundsen Sea Embayment. The Antarctic Peninsula has experienced a dramatic increase in mass loss in the last decade following the destabilization of the Southern Antarctic Peninsula. The total mass loss is partly compensated by a significant mass gain in East Antarctica due to a positive trend of SMB anomalies.

4th Cryosat User workshop

In addition to major scientific results and products, the conference combined with the 4th CryoSat User Workshop, bringing together users from all cryospheric disciplines to discuss a variety of issues such as: Product Calibration and Validation campaigns, future data product releases and further serving the needs of the scientific community. In addition, with the satellite currently being operated beyond in it’s initial commissioning timespan, initial discussions were held regarding whether there would be the possibility of a follow up and the form it could possibly take.

Sentinel 1A/B – A New Era for Ice sheet Velocity Mapping

sentinel

Sentinel 1A/B is the Copernicus Synthetic Aperture Radar (SAR) mission, providing global radar imagery currently at a 12 day repeat period, free from the limitations posed by multispectral imagery such as cloud cover. The launch of Sentinel 1B on the 25th April this year to join in constellation with 1A will reduce this repeat period to 6 days. This will allow for continuous, long term monitoring of the Earth’s Cryosphere at a high temporal resolution.

Sentinel 1 results presented at the conference exemplified the transformative power this mission will have on Cryospheric sciences. Firstly, it will allow us to produce continental velocity maps for both Greenland and Antarctica at sub-annual resolution. This will allow for monitoring of seasonal velocity changes in outlet glaciers, better estimations of mass balance and improved parameterisations of conditions in ice sheet models.  Additionally, the mission is now providing researchers with a near real time data stream of ice velocities for key outlets of the Greenland and Antarctic ice sheets, allowing them to track changes and investigate changes in behaviour at 12-day scale (reducing to 6 days with 1B) (Hogg et al, 2016).

Ice Sheet velocity across the Antarctic peninsula derived from Sentinel 1 data from December 2014 to March 2016. Image Credit ESA and ENVEO: http://www.esa.int/spaceinimages/Images/2016/05/Antarctic_Peninsula_ice_flow

Ice Sheet velocity across the Antarctic peninsula derived from Sentinel 1 data from December 2014 to March 2016. (Credit: ESA and ENVEO)

The grounding line is a key region of the ice sheet to monitor due to it’s ability to indicate changes in the dynamics of the inland Ice Sheet and it’s potential instability. SAR missions allow us to map the grounding line with high accuracy by analysing the differences in vertical tidal displacement of the ice shelves between images via the formation of interferograms. Previously there has been discontinuous temporal coverage from various SAR missions; however with the advent of Sentinel 1 mission, it will possibly to routinely monitor grounding line flux position for an extended period of time, improving our understanding of key ice sheet processes and inland grounded ice stability.

Final Thoughts

The conference showed us the combined power offered by the new Sentinel missions and the continuation of CryoSat-2 in allowing us to monitor the Cryosphere at scales not previously possible, thus shedding more light on the dynamics of these key earth system regions. The new satellites have allowed researchers to produce new and improved datasets open for use by the scientific community, helping to accelerate and enable future discoveries. Additionally, when these datasets are used in combination, they can help us to better answer some of the subject’s biggest questions; such as the mass balance of the Ice Sheets and its changes over time. As a result, these missions promise for exciting times ahead in terms of greatly forwarding our understanding of the Cryosphere.

 With the new sentinel missions and the continuation of CryoSat-2 exciting times are ahead for remote sensers of the cryosphere

Aside from the Conference – City of Prague

Prague offered many sights and opportunities to explore during the downtime of the conference. Highlights of the City included the Charles Bridge built in 1390 and the old Town Square which hosts the famous astronomical clock. All of this is set to the backdrop of Prague Castle, the largest ancient castle in the world and residence of the President of the Czech Republic. The City also has a famous classical music and opera scene and offers some of the world’s best beer, providing the perfect opportunity to network and make contacts!


References

  • Chuter, S. J., and J. L. Bamber (2015), Antarctic ice shelf thickness from CryoSat-2 radar altimetry, Geophys. Res. Lett., 42(24), 10,721–10,729, doi:10.1002/2015GL066515.
  • Gray, L, D Burgess, L Copland, R Cullen, N Galin, R Hawley, and V Helm. 2013. “Interferometric Swath Processing of Cryosat Data for Glacial Ice Topography.” The Cryosphere 7 (6). Copernicus GmbH: 1857–67.
  • Griggs, J.A., and J.L. Bamber. 2011. “Antarctic Ice-Shelf Thickness from Satellite Radar Altimetry.” Journal of Glaciology 57 (203). International Glaciological Society: 485–98. doi:10.3189/002214311796905659.
  • Hogg, A., A. Shepherd, N. Gourmelen (2015) A first look at the performance of Sentinel-1 over the West Antarctic Ice Sheet, FRINGE 2015, Frascati, Italy, 23-27 March 2015.
  • Martín-Español, A. et al. (2016), Spatial and temporal Antarctic Ice Sheet mass trends, glacio-isostatic adjustment and surface processes from a joint inversion of satellite altimeter, gravity and GPS data, J. Geophys. Res. Earth Surf., 120, 1–18, doi:10.1002/2015JF003550.
  • Tilling, R. L., A. Ridout, A. Shepherd, and D. J. Wingham (2015), Increased Arctic sea ice volume after anomalously low melting in 2013 – supplementary Information, Nat. Geosci., 8(8), 643–646, doi:10.1038/ngeo2489.

Edited by Sophie Berger


steve

Stephen Chuter is a PhD Student at the University of Bristol, UK. He  Investigates the dynamics of the Antarctic Ice Shelves and grounding zone using the ESA CryoSat-2 satellite. The unique orbital characteristics and novel SARIn mode of operation allow us to study these areas in much greater detail than possible from previous radar altimetry missions, therefore allowing us to greater ascertain its role in ice sheet stability. He tweets as @StephenChuter.
Contact Email: s.chuter@bristol.ac.uk

 

Only extremes – Babis Charalampidis

Only extremes – Babis Charalampidis

– In fieldwork, you have no average. You just have extremes.

When Daniel spoke his mind out loud we were facing a bright sunny day coming in from the opening of our tent. We were very glad to see that and ready to engage with our glaciological tasks. Our camp site was at the immediate fore field of the A. P. Olsen ice cap in Northeast Greenland. We had arrived there the previous evening and had two days left to spend for our science up on the ice. But, on Saturday 30 August, we had to return to Tyrolerfjorden, no-matter-what. It had to happen in one-go, which means a 12-hour hike, 30 kilometers, carrying everything. Our appointment with Kenny was 00:30 hours at its narrow coast, so he can provide us a safe passage with the boat back to the ZERO station. The weather was closing in again on Sunday and with four days of supplies left, we just had to make things happen.

The author posing against a background of mountains (Credit: Daniel Binder)

Arctic fieldwork: Pose and reality. (Credit: Daniel Binder)

Daniel’s statement is very funny because it is actually very much true. Polar scientists always post their greatest photos, where they look like awesome polar explorers, implying that everything was completed like piece-of-cake. I do that too. But, there is always the other side of every story. Any fieldworker in the Arctic can verify that no matter how much experience you have or how hardened you have become through the years, every new mission is absolutely unique and different in many ways from all the previous ones. You have to prepare yourself the best way you can and when the time comes, perform your absolute best. Then, you have to also just hope for the best.

The initial plan was simple really. Two glaciers on the Northeast coast monitored by two institutes, ZAMG and GEUS, to be visited by a two-person mission, one from each institute, right? The team would be an alpine glaciologist with experience in the Austrian glaciers and an ice sheet glaciologist with experience in Greenland, both familiar with Zackenberg. End-of-summer mission implies that there is no sea ice in the fjords, so the team would have to hike everywhere. It also implies that there will be limited if any snow cover on the ice fields. Right…

When we began the first part of the mission on Freya glacier, the reality was quite different from our expectations. The biggest part of the glacier was still covered in snow. We were glad to see that, since it implied a positive mass budget year for Freya. On the other hand, since this was unexpected and we didn’t have our snow shoes with us, every step that we made was a struggle with the snow cover trying to swallow our legs while we are carrying all our equipment. Myself, I am what Daniel calls a “spoiled glaciologist”. Lightweight guy, I am definitely not as strong as he is, always riding on helicopters, twin otters and ski-doos. Seeing this genuine mountaineer also exhausted at the end of that first day on Freya made me feel a bit better about my performance. Of course, he was carrying about 10-20 kilos more on his back. Nevermind that.

figure_map

Map of the wider region of Zackenberg (Geodætisk Institut).

Sleeping on the side moraine of Freya inside bivouac sacks was also a new experience for me. We were glad not to experience fierce weather, so it was overall not too bad. But the fact is that in a bivouac, you end up quite quickly in a pool of liquefied water vapor that rains down on your face. Remedy is not too easy since as soon as you open the sack, you are exposed to the freezing glacial air. Fever in the morning was guaranteed for me.

Back at the ZERO station and before the hike to A. P. Olsen land, our preparations definitely included snow shoes. The previous days on Freya, we were able to spot the Argo glacier, the East-flowing glacier of the A. P. Olsen ice cap, on the horizon. It seemed to have an extended ablation zone with no snow cover, but since our plans included a visit in the upper GlacioBasis station, we thought that snow shoes would come in handy. As it turned out that was a really wise decision.

On Saturday 23 August we began the second part of our mission. Kenny and Lars dropped us off with the boat at the north coast of Tyrolerfjorden, west of Zackenberg and opposite of Eiger on the Clavering island. The weather was not inviting, cloudy atmosphere with small droplets falling now and then, but nothing too alarming. Our greatest concern at that time was crossing successfully the river at Store Sødal that may or may not be raging and full of water. As it turned out, crossing the river was not too challenging, since the flow at the end of the summer season is significantly reduced. But, the persistent cloud cover had gotten very thick by early evening and resulted in rain and eventually a storm.

Hard tasks and rewarding views (Credit: Babis Charalampidis).

Hard tasks and rewarding views (Credit: Babis Charalampidis).

While being in the proglacial valley of the Argo glacier, we were still closer to Store Sødal than to the ice cap when we decided to set camp and take shelter from the storm. We were definitely glad to get a bit dry, but we knew that this was a far from ideal situation. In this region, a lot of furry animals like to hang out. Snow foxes, arctic hare, but also bigger ones: muskoxen, polar bears… Any close encounter with them was far from our desires and although we were equipped with a flare gun and a rifle, one always prefers to return them unused, when one gets to return. We could only hope that our training and instinct would serve us well, should the circumstances require it.

Sleeping in the tent was frustrating. Every noise from outside – the wind, rock falls, the river – were keeping us from relaxing and enjoying our sleeps. In the morning, the storm was still going on. What we couldn’t have guessed at the time is that it would last for more than three days. Our initial awareness turned into prolonged sleeping sessions. In the interest of carrying less weight, we didn’t have with us any books or card games. Our daily routine included frequent chats during coffee times that intervened between our 2-3 hourly naps. A big moment every day, was 8 pm when we would call Kenny to let him know we’re doing fine and learn the weather forecast. Sadly, we had to hear the words: “Still stormy forecast, boys” quite a bit. The mood would catch up later in the evening when we would have our modest dinner and finish the day with cognac and cigarettes.

Good times, bad times (Credit: Babis Charamlapida).

Good times, bad times (Credit: Babis Charamlapida).

The time came when we heard good news: “Tomorrow, Wednesday 27th at noon sky clears up, boys”! And so it did. But, hiking after such a prolonged period in horizontal position was not something to derive pleasure from. By the end of that day, exhausted as we were, we managed to set camp at the very front of the glacier. Having wasted three days of supplies, we knew that we wouldn’t make it to the upper station. But, also one glimpse at the glacier predetermined that we will be slow again: The rain storm at the bottom of the valley was in fact a snow storm at the ice cap. The snow cover was everywhere at least half a meter and although we would be faster than on Freya with the snow shoes, we wouldn’t be as fast as we had hoped.

We successfully completed most of our tasks on A. P. Olsen and we definitely enjoyed this expedition. The scenery is always breathtaking and after all, this mission was more like an adventure of two friends than conventional glaciological fieldwork. But, it is also a fact that we overworked ourselves.

Last day on A. P Olsen and last hours of hike the next day before our pick-up from Tyrolerfjorden (Credit: Babis Charamlapida).

Last day on A. P Olsen and last hours of hike the next day before our pick-up from Tyrolerfjorden (Credit: Babis Charamlapida).

It is always good to remember that some moments throughout the process can be quite tough. In the end, this is probably the case with everything in life. The journey teaches you a few things. I will never forget the pain all over my body after the last hike from the ice cap to Tyrolerfjorden, racing against the clock on very challenging terrain with full backpacks. I will never forget the sense of trust that was developed between me and Daniel, how well we collaborated, coexisted and in a sense completed each other on this trip. Finally, I will never forget to have always a small book and a deck of cards with me.

Babis Charalampidis (GEUS/Uppsala University) is an Uppsala University PhD student within the SVALI project, based at the Geological Survey of Denmark and Greenland and supervised by Dirk van As. He is interested in the Greenland ice sheet’s mas budget, particularly the link between energy balance and subsurface processes such as percolation and refreezing. He studies the changes of the lower accumulation area of the southwest of the ice sheet in a warming climate, based on in situ observations.