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Cryospheric Sciences

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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

Black Carbon: the dark side of warming in the Arctic

Black Carbon: the dark side of warming in the Arctic

When it comes to global warming, greenhouse gases – and more specifically CO2 – are the most often pointed out. Fewer people know however that tiny atmospheric particles called ‘black carbon’ also contribute to the current warming. This post presents a paper my colleague and I recently published in nature communications. Our study sheds more light into the chemical make-up of black carbon, passing through the Arctic.


Black Carbon warms the climate

 Figure 1: Global radiative forcing of CO2 (green) compared to black carbon (blue). The colored bars show the mean change in radiative forcing due to the concentration of CO2 and BC in the atmosphere. The estimated range for the expected radiative forcing is everything between the white lines, which show the 90% confidence interval. (Data according to Boucher et al. 2013 (IPCC 5th AR) and Bond et al. 2013). [Credit: Patrik Winiger]

Figure 1: Global radiative forcing of CO2 (green) compared to black carbon (blue). The colored bars show the mean change in radiative forcing due to the concentration of CO2 and BC in the atmosphere. The estimated range for the expected radiative forcing is everything between the white lines, which show the 90% confidence interval. (Data according to Boucher et al. 2013 (IPCC 5th AR) and Bond et al. 2013). [Credit: Patrik Winiger]

Black Carbon (BC) originates from incomplete combustion caused by either natural (e.g., wild fires) or human (e.g., diesel car emissions) activities. As the name suggests, BC is a dark particle which absorbs sunlight very efficiently. In scientific terms we call this a strong positive radiative forcing, which means that the presence of BC in the atmosphere is helping to heat the planet. Some estimates put its radiative forcing in second place, only after CO2 (Figure 1). The significant thing about BC is that it has a short atmospheric lifetime (days to weeks), meaning we could quickly avoid some climate warming by getting rid of its emissions. Currently global emissions are increasing year by year and on snow and ice, the dark particles have a longer lasting effect due to the freeze and thaw cycle, where BC can re-surface, before it is washed away. It is important however to note, that our main focus on emission reduction should target (fossil-fuel) CO2 emissions, because they will affect the climate long after (several centuries) they have been emitted.

Arctic amplification: strongest warming in the North Pole

The Arctic is warming faster than the rest of our planet. Back in 1896, the Swede Arrhenius, (better known for his works: in chemistry), calculated, that a change in atmospheric CO2 – which at that time was a good 100 ppm lower than today – would change the temperature at higher latitudes (towards the poles) more than at lower latitudes.

Figure 2: Observation based global surface temperature anomalies for Jan-Mar (2016) in °C with respect to a 1961-1990 base year. Credit: GISTEMP Team, 2016: GISS Surface Temperature Analysis (GISTEMP). NASA Goddard Institute for Space Studies. Dataset accessed 2016-10-15 at http://data.giss.nasa.gov/gistemp/ [Hansen et al., 2010].

Figure 2: Surface temperature anomalies (in °C) for Jan-Mar (2016) with respect to a 1961-1990 baseline. [ Credit: NASA — GISTEMP (accessed 2016-10-15) and Hansen et al., 2010].

The problem with his calculations – as accurate and impressive they might have been – was, that he ignored the earth’s geography and seemed unaware of the big heat capacity of the oceans. On the southern half of our planet there is a lot more water, which can take up more heat, as compared to the northern half with more land surface. Thus, in reality the latitudes on the southern hemisphere have not heated as much as their northern counterparts and this effect came to be known as Arctic amplification.

Dark particles on bright snow and ice

Figure 3: Welcome to the Greenland Ice Sheet everybody. Probably an extreme case of ice covered in cryoconite, captured in August 2014 [Credit: Jason Box, (LINK: http://darksnow.org/)].

Figure 3: Ice covered in cryoconite, Greenland Ice Sheet, in August 2014 [Credit: Jason Box — Dark Snow project].

Greenhouse gases and BC are not the only reasons for the increase in temperature change and earlier onset of the melting season in the Arctic. Besides BC, there are other ‘light absorbing impurities’ such as dust, microorganisms, or a mixture of all of the above, better known as cryoconite. They all absorb solar radiation and thus decrease the albedo – the amount of solar energy reflected back to space – of the underlying white surface. This starts a vicious cycle by which these impurities melt the snow or ice and eventually uncover the usually much darker surface (e.g., rock or open sea water), leading to more solar absorption and the cycle continues. The effect and composition of these impurities are currently intensively studied on the Greenland ice sheet (check out the Black and Bloom, as well as the Dark Snow projects).

 Black Carbon effect on climate is highly uncertain

One of the reasons for the high uncertainty of BC’s climate effects is the big range in effects it has (see white line on Figure 1), when it interacts with snow and ice (or clouds and the atmosphere).

Another source of uncertainty is probably the big estimated range in the global, and especially in the regional emissions of BC in the Arctic. For example, the emission inventory we work with (ECLIPSE), is based on international and national statistics that indicate how much of a certain fuel (diesel, coal, gas, wood, etc.) is used, and in which way it is used (vehicle sizes, machine type and age, operating conditions, etc.). These numbers can vary a lot. If we, for example, line up different emission inventories of man-made emissions (Figure 4), by comparing the two different fractions of BC (fossil fuels vs. biomass burning) at different latitudes, then we see that the closer we get to the North pole, the more these emission inventories disagree. And this is still ignoring atmospheric transport or emissions of natural sources, such as wildfires.

Computer models, necessary to calculate global climate change, are partly based on input from these emission inventories. Models used for the calculation of the transport of these tiny particles have vastly improved in recent years, but still struggle at accurately mimicking the seasonality or extent of the observed BC concentrations. To some extent this is also due to the range of parametrization in the model, mainly the lifetime of BC, including its removal from the atmosphere by wet scavenging (e.g., rain). So to better understand black carbon effects on climate, more model calculations are necessary, for which the emission inventory estimates need to be verified by observations.

Figure 4: Fraction biomass burning of BC (fbb) at different latitudes North, estimated by three different emission inventories. The green line shows the GAINS emission inventory, which was the precursor to the ECLIPSE inventory (Klimont et al. 2016) [Credit: Patrik Winiger]

Figure 4: Fraction biomass burning of BC (fbb) at different latitudes North, from three different emission inventories. The green line shows the GAINS emission inventory, which was the precursor to the ECLIPSE inventory (Klimont et al. 2016) [Credit: Patrik Winiger]

How do we trace the origin of black carbon?

This is where the science of my colleagues and me comes in. By looking at BC’s isotopic ratio of stable-carbon (12C/13C) and its radiocarbon (14C) content we were able to deduce information about the combustion sources (Figure 5).

Plants (trees) take up contemporary radiocarbon, naturally present in the atmosphere, by photosynthesis of atmospheric CO2. All living organisms have thus more or less the same relative amount of radiocarbon atoms, we talk of a similar isotopic fingerprint. BC from biomass (wood) burning thereby has a contemporary radiocarbon fingerprint.

When they die, organisms stop incorporating contemporary carbon and the radiocarbon atoms are left to decay. Radiocarbon atoms have a relative short (at least on geological time-scales) half-life of 5730 years, which means that fossils and consequentially BC from fossil fuels are completely depleted of radiocarbon. This is how the measured radiocarbon content of a BC sample gives us information on the relative contributions of fossil fuels vs. biomass burning.

The stable carbon isotopic ratio gives information on the type of combustion sources (liquid fossil fuels, coal, gas flaring or biomass burning). Depending on how a certain material is formed (e.g., geological formation of coal), it has a specific isotopic ratio (of 12C/13C), like a fingerprint. Sometimes isotopic fingerprints can be altered during transport (because of chemical reactions or physical processes like condensation and evaporation). However, BC particles are very resistant to reactions and change only very little. Hence, we expect to see the same fingerprints at the observation site and at the source, only that the isotopic signal at the observation site will be a mixture of different source fingerprints.

Figure 5/ Carbon isotopic signatures of different BC sources, summarized by E.N. Kirillova (2013).

Figure 5: Carbon isotopic signatures of different BC sources, summarized by E.N. Kirillova (2013). To give information about the isotopic fingerprint, the delta-notation is used (small delta for 12C/13C, and big delta for 12C/14C). The isotopic values show how much a certain sample is different, on a per mil scale, from an international agreed isotopic standard value (or ratio) for carbon isotopes. [Credit: fig 1 from  Kirillova (2013)]

Where does the black carbon in European Arctic come from?

In our study (Winiger et al, 2016), we observed the concentrations and isotopic sources of tiny particles in airborne BC for over a year, in the European Arctic (Abisko, Sweden), and eventually compared these observations to model results, using the freely available atmospheric transport model FLEXPART and emission inventories for natural and man-made BC emissions.

Seeing our results we were first of all surprised at how well the model agreed with our observations. We saw a clear seasonality of the BC concentrations, like it has been reported in the literature before, and the model was able to reproduce this. Elevated concentrations were found in the winter, which is sometimes referred to as Arctic haze. The combustion sources showed a strong seasonality as well. The radiocarbon data showed, that fossil fuel combustion dominated in the winter and (wood) biomass burning during the low BC-burden periods in the summer. With a combination of the stable isotope fingerprints and Bayesian statistics we further concluded, that the major fossil fuel emissions came from liquid fossil fuels (most likely diesel). The model predicted a vast majority of all these BC emissions to be of European origin. Hence, we concluded, that the European emissions in the model had to be well constrained and the model parametrization of BC lifetime and wet-scavenging had to be fairly accurate for the observed region and period. Our hope is now that our work will be implemented in future models of BC effects and taken into account for future BC mitigation scenarios.

Figure 6: This is an example from the model calculations, showing where the (man-made) BC came from in January 2012. Abisko's position is marked as a blue star. The darker (red) spots show sources of higher BC contribution. This winter example was among the three highest observed (in terms of BC concentration) and the sources were ~50% wood burning, ~20% liquid fossil fuels (diesel) and ~30% coal. Some of the darkest spots can clearly be attributed to European cities.

Figure 6: Example from the model calculations, showing where the (man-made) BC came from in January 2012. Abisko’s position is marked as a blue star. The darker (red) spots show sources of higher BC contribution. This winter example was among the three highest observed (in terms of BC concentration) and the sources were ~50% wood burning, ~20% liquid fossil fuels (diesel) and ~30% coal. Some of the darkest spots can clearly be attributed to European cities. [Credit: fig4b from Winiger et al (2016)]

References

  • Anderson, T. R., E. Hawkins, and P. D. Jones (2016), CO2, the greenhouse effect and global warming: from the pioneering work of Arrhenius and Callendar to today’s Earth System Models, Endeavour, in press, doi:10.1016/j.endeavour.2016.07.002.
  • Arrhenius, S. (1896), On the influence of carbonic acid in the air upon the temperature of the ground., Philos. Mag. J. Sci., 41(August), 239–276, doi:10.1080/14786449608620846.
  • Hansen, J., R. Ruedy, M. Sato, and K. Lo (2010), Global surface temperature change, Rev. Geophys., 48(4), RG4004, doi:10.1029/2010RG000345.
  • Klimont, Z., Kupiainen, K., Heyes, C., Purohit, P., Cofala, J., Rafaj, P., Borken-Kleefeld, J., and Schöpp, W.: Global anthropogenic emissions of particulate matter including black carbon, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-880, in review, 2016.
  • Kirillova, Elena N. “Dual isotope (13C-14C) Studies of Water-Soluble Organic Carbon (WSOC) Aerosols in South and East Asia.” (2013). ISBN 978-91-7447-696-5 pp. 1-37
  • Winiger, P., Andersson, A., Eckhardt, S., Stohl, A., & Gustafsson, Ö. (2016). The sources of atmospheric black carbon at a European gateway to the Arctic. Nature Communications, 7.

Edited by Sophie Berger, Dasaraden Mauree and  Emma Smith
This is joint post with the Atmospheric Division , given the interdisciplinarity of the topic featured.


portraitPatrik Winiger is a PhD student at the Department of Environmental Science and Analytical Chemistry and the Bolin Centre for Climate Research, at Stockholm University. His research interest focuses on impact and mitigation of Short Lived Climate Pollutants and anthropogenic CO2 emissions. Currently he investigates the sources of black carbon aerosols in the Arctic. He tweets as @PatrikWiniger

 

Image of The Week – Plumes of water melting Greenland’s tidewater glaciers

fig1figoftheweek

Figure 1: Simulation of a plume at a tidewater glacier in a general circulation model (MITgcm). Left – water temperature and right – time-averaged submarine melt rate in metres per day. Shown are face-on views of a tidewater glacier, as if you were under the water in front of the glacier, looking towards the calving front. 250 m3/s of fresh water emerges into the ocean from a channel at the bottom of the glacier, forming a plume. As the plume rises towards the fjord surface it mixes turbulently with warm ocean water, causing the plume to warm with height. Further details of this simulation can be found here: Slater et al. 2015.

Loss of ice from The Greenland Ice Sheet currently contributes approximately 1 mm/year to global sea level (Enderlin et al., 2014). The most rapidly changing and fastest flowing parts of the ice sheet are tidewater glaciers, which transport ice from the interior of the ice sheet directly into the ocean. In order to better predict how Greenland will contribute to future sea level we need to know more about what happens in these regions.


Tidewater glaciers meet the ocean at the calving front (Fig. 2), where ice undergoes melting by the ocean (“submarine melting”) and icebergs calve off into the sea. In recent decades, tidewater glaciers around Greenland have retreated (due to increased loss of ice at the calving front) and started flowing faster. This in turn causes more ice to be released into the ocean, contributing to sea level. Understanding the cause of these changes at tidewater glaciers is an ongoing topic of research.

Figure 2: Kangiata Nunata Sermia, a large tidewater glacier in south-west Greenland. The expression of a plume originating at the base of the calving front is visible on the fjord surface as turbid sediment-rich water. [Credit: Peter Nienow]

Figure 2: Kangiata Nunata Sermia, a large tidewater glacier in south-west Greenland. The expression of a plume originating at the base of the calving front is visible on the fjord surface as turbid sediment-rich water. [Credit: Peter Nienow]

One possible cause of change is an observed warming of the ocean around Greenland (Straneo and Heimbach, 2013). A warming of the ocean is likely to lead to increased submarine melt rates, which may in turn influence iceberg calving if, for example, melting results in instability of the ice at the calving front. Submarine melt rates are thought to be increased further by upwelling of warm water at the calving front (Fig. 1 and Fig. 2).

This upwelling water, called a plume, may be initiated by submarine melting of the ice, or by fresh glacial meltwater from the ice sheet surface. This fresh glacial meltwater penetrates to the base of the glacier and flows into the ocean from beneath the glacier, which may be hundreds of metres underwater. Once in the ocean, the meltwater rises buoyantly because of a density difference between the meltwater and ocean water, forming a plume. In order to better understand the effect of plumes on submarine melting, we can model plumes using a numerical model (e.g. MITgcm). Our image of the week (Fig. 1) shows such a model, which we can use to estimate submarine melt rates. In combination with simpler analytical approaches (Jenkins et al., 2011; Slater et al., 2016), we can estimate how submarine melt rates may change over time and from glacier to glacier (Carroll et al., 2016), and begin to assess the effect of submarine melting on tidewater glaciers and ultimately on future sea level rise.

Edited by Teresa Kyrke-Smith and Emma Smith


donalds_face

Donald Slater is a PhD student in the Glaciology and Cryosphere Research Group at the University of Edinburgh. His research focusses on understanding the effect of the ocean on the Greenland Ice Sheet. For more information look up his website or follow him on twitter @donald_glacier.

Sea Level “For Dummies”

Sea Level “For Dummies”

Looking out over the sea on a quiet day with no wind, the word “flat” would certainly pop up in your mind to describe the sea surface. However, this serene view of a flat sea surface is far from accurate at the global scale.

The apparent simplicity behind the concept of sea level hides more complex science that we hope to explain in a simple manner in today’s “For Dummies” post, which will give you the keys to understand the important aspects of past sea change, and an ability to look into and understand how sea level is a key factor in the future.

Everyone will be familiar with news stories about current sea level rise, but it can be very confusing to understand what this means in real terms; how fast it is happening and why we should care about it anyway. So to begin with, let’s have a look at what we mean by sea level?


Sea Level – It’s all about gravity!

[Read More]

Image of the Week – Satellite Measurements of Arctic Sea Ice

Image of the Week – Satellite Measurements of Arctic Sea Ice

Sea ice is an important part of the Earth’s climate system. When sea ice forms, it releases heat and salt. When sea ice melts, it takes up heat and adds freshwater to the salty ocean water. It is also important for the exchange of energy between the atmosphere and the ocean surface, and for the ocean currents that transport warm and cold water from the equator to the poles and back.

The main route of sea ice moving south from the Arctic Ocean is through Fram Strait. This is the passage between  Greenland and Svalbard around 75-80°N latitude (see map). Today’s “Image of the Week” shows the amount of sea ice that flows  through this pathway each day (known as the mean observed volume flux) for October-November 2006.


What is sea ice volume flux and how is it computed?

Sea ice volume flux sounds a bit wordy – so what is it and why do we use it? Let’s start with the sea ice volume  – this simply tells us how much sea ice there is. In order to calculate the volume, you need to know not only the concentration of sea ice (i.e. the fraction of ocean covered by ice) but also its thickness. The flux parts comes in when we want to talk about the amount of sea ice moving through an area (e.g. Fram Strait). In order to calculate sea ice volume flux, you need to know both sea ice volume and drift. The latter is the displacement of sea ice over a certain period of time, typically measured in kilometres per day. So the volume flux is basically a measure of the volume of ice that moves through a certain area over a given time! Simple!?

An aerial view of the helicopter taking data of the sea ice below.

An aerial view of the helicopter taking data of the sea ice below. Photo credit: Alice O’Connor.

What does the “Image of the Week” show?

The  map was constructed by Spreen et al. (2009) from satellite data and provided one of the first estimates of  sea ice volume flux through Fram Strait exclusively using satellites.  However, it is  challenging to accurately measure sea ice thickness in the summer using satellites because of the  melt ponds (pools of open water forming on sea ice when temperatures are higher, i.e. summer) that interfere with the satellite signals. A few measurements of sea ice thickness have been collected in the summer from British and US submarines in the 1980s and 1990s but only in the region near the pole.  A recent study presents a way to compute sea ice volume fluxes through Fram Strait in the summer using a new dataset of ground-based and airborne electromagnetic ice thickness measurements (Krumpen et al., 2016).

In this new study, the concentration of sea ice is found from satellite measurements (passive microwave sensors to be specific). The sea ice drift can be found by using both satellite data and observations from buoys. Finally, the thickness of the sea ice comes from surveys using radar instruments on the ground or from an aircraft. This data was collected during 5 summers, by combining the three of these measurements, Krumpen et al., (2016) calculated the sea ice volume flux during the summer!

In the figure below, the red lines show the sea ice area flux using the concentration and drift only through Fram Strait in July and August from 1980 to 2012. Positive values mean that sea ice moves out of the Arctic Basin, while negative values represent sea ice that goes into the Arctic Basin. The figure shows that there are large variations in sea ice area flux from year to year.

The black dots are the volume fluxes (area flux times thickness) for the 5 summer seasons where the ice thickness was measured. The dots show that in some summers sea ice volume flux is negative, meaning that sea ice moves into the Arctic Basin. In other summers, for example in 2010, sea ice moves out of the Arctic Basin.

July (black, gray shading for uncertainty) and August (red, light red shading for uncertainty) sea ice area fluxes through Fram Strait (left axis). Black dots show sea ice volume flux for the 5 campaigns during which ice thickness is computed using electromagnetic measurements (right axis). Positive values mean that sea ice is moving out out of the Arctic Ocean while negative values mean that sea ice is flowing into the Arctic Ocean. [Figure 8 of Krumpen et al. (2016)]

July (black, gray shading for uncertainty) and August (red, light red shading for uncertainty) sea ice area fluxes through Fram Strait (left axis). Black dots show sea ice volume flux for the 5 campaigns during which ice thickness is computed using electromagnetic measurements (right axis). Positive values mean that sea ice is moving out out of the Arctic Ocean while negative values mean that sea ice is flowing into the Arctic Ocean. [Figure 8 of Krumpen et al. (2016)]

What comes next…

If field campaigns in the future continue to measure sea ice thickness in the summer, the calculations can be continued and we will learn more about the volume of sea ice that is transported through Fram Strait in the summer. This is important if we are to measure the balance of sea ice in the Arctic Ocean.

Edited by Nanna B. Karlsson


DavidDavid 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 – 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 — Looking for ice inside a volcano !

Image of the Week —  Looking for ice inside a volcano !

Who would think that one of the world’s most active volcano shelters the southernmost persistent ice mass in Europe!?

Yes, you can find ice inside Mount Etna!

Located at an altitude of about 2,040 m above sea level, the Ice Cave  (Grotta del Gelo) is well known among Mt Etna’s volcanic caves due to the presence of columns of ice on its walls and floor which occupy about the 30% of the cave’s volume and persist all year round.

How did the ice get there and why does it remain?

  • This cave a small lava tube of less than 100 metres long was formed during Etna’s longest eruption that occurred on its northern flank from 1614 to 1624 A.D. (Marino, 1999)
  • Once formed, the cave was subsequently filled with ice.
  • The shape of the cave enables the ice to persist because there is only one single entrance to the ice cave that insulate the air from the outside. This enables the temperature to stay below 0°C in some parts of the cave all year round. This is not the case with other lava tubes around Etna that have several entrances, which allows the air to circulate within the caves, causing warming

Exploring the Ice Cave

By studying ice inside caves, researchers can obtain very useful biological and paleo-climatological information. Although we don’t know much about the conditions of the ice mass and its evolution over the last few centuries, speleologists (Centre Speleogico Etneo) and scientists (Italian National Institutites of Geophysics and Volcanology) have studied the cave for the past 20 years.

The use of new technologies such as UAV’s (see THIS or THIS previous blog posts about other applications of UAVs in glaciology) or terrestrial laser scanners on glaciers and ice caves can give the possibility to monitor surface variations of hidden underground areas that have never been affected by human activities.

This year, researchers and speleologists from the Inside The Glaciers Project, organised a first expedition to the cave, to acquire precise measurements of the ice mass surface, with a terrestrial laser scanner.

After a long walk of about 4 hours through beautiful volcanic landscapes, the Inside The Glacier team arrived at the entrance of the cave. There they surveyed the Ice Cave for 5 hours, performing 17 scans to detect the ice mass with very high accuracy.

With these measurements it was possible to draw detailed topographic plant and sections of the cave and derive 3D models of its surfaces, obtaining first data that will be compared in future with other laser scanner surveys to help scientists to study the evolution of the ice mass inside the cave.

Topographic plant and profile of the Ice Cave derived from laser scanning data. Ice deposits are represented in cyan color.[Credit: Tommaso Santagata]

Topographic plant and profile of the Ice Cave derived from laser scanning data. Ice deposits are represented in cyan color.[Credit: Tommaso Santagata]

Acknowledgements

This expedition was organized within the “Inside The Glaciers” Project in collaboration with the Association La Venta Esplorazioni Geografiche, Etna Natural Park, Italian National Insitute of Geophysics and Volcanology (I.N.G.V.), Centro Speleologico Etneo, Federazione Speleologica Regionale Siciliana, Gruppo Servizi Topografici s.n.c.

(Edited by Sophie Berger and Emma Smith)


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 – How ocean tides affect ice flow

Image of the Week – How ocean tides affect ice flow

Ice streams discharge approximately 90% of the Antarctic ice onto ice shelves , and ultimately into the sea into the sea (Bamber et al., 2000; Rignot et al., 2011). Whilst flow-speed changes on annual timescales are frequently discussed, we consider here what happens on much shorter timescales!

Previous studies have shown that ice streams can respond to ocean tides at distances up to 100km inland (e.g. Gudmundsson, 2006 ; Murray et al., 2007; Rosier et al, 2014); new high-resolution remotely sensed data provide a synpoptic-scale view of the response of ice flow in Rutford Ice Stream (West Antarctica), to ocean tidal motion.

These are the first results to capture the flow of an entire ice stream and its proximal ice shelf in all three spatial dimensions and in time.

The ocean controls the Antarctic ice sheet

The ice-ocean interface is very important as nearly all ice-mass loss occurs directly into the ocean in Antarctica (Shepherd et al., 2012). Many areas terminate on ice shelves (the floating ice that connects with the land ice), which are fed by the flow of ice from the ice sheet. Any changes to the floating ice shelf alter the forces acting on the grounded ice upstream, therefore directly affecting the ice sheet evolution (e.g. Gudmundsson, 2013; Scambos et al, 2004).

Because ocean tides are well-understood, we can use the response of grounded ice streams to ocean tidal uplift over the ice shelf to better understand how ice sheets respond to ocean-induced changes.

An ice stream and ice shelf respond to forcing by ocean tides

Floating ice shelves are directly affected by tides, as their vertical displacement will be altered. These tidal variations are on short timescales (hourly to daily) compared to the timescales generally associated with ice flow (yearly). The question therefore is, how much can the tides affect horizontal flow speeds, and how far inland of the ice shelf are these effects felt?

The movie below, by Brent Minchew et al, shows the significant response of Rutford Ice Stream and its ice shelf to forcing by the tides. Using high-resolution synthetic aperture radar data they are able to infer the significant spatio-temporal response of Rutford Ice Stream in West Antarctica to ocean tidal forcing. The flow is modulated by the ocean tides to nearly 100km inland of the grounding line. These flow variations propagate inland at a mean rate of approximately 30 km/day and are sensitive to local ice thickness and the mechanical properties of the ice-bed interface. Variations in horizontal ice flow originate over the ice shelf, indicating a change in (restraining force) over tidal timescales, which is largely attributable to the ice shelf lifting off of shallow bathymetry near the margins. Upstream propagation of ice flow variations provides insights into the sensitivity of grounded ice streams to variations in ice shelf buttressing.

Horizontal ice flow on Rutford Ice Stream inferred from 9 months of continuous synthetic aperture radar observations. (a) Total horizontal flow. Colormap indicates horizontal speed and arrows give flow direction. (b) Detrended horizontal flow variability over a 14.77-day period. Colormap indicates the along-flow component (negative values oppose flow) while arrows indicate magnitude and direction of tidal variability. Contour lines give secular horizontal speed in 20 cm/day increments. (c) Modelled vertical tidal displacement over the ice shelf. (Credit : Brent Minchew)

Reference

B. M. Minchew, M. Simons, B. V. Riel, and P. Milillo. Tidally induced variations in vertical and horizontal motion on Rutford Ice Stream, West Antarctica, inferred from remotely sensed observations. submitted to JGR, 2016

(Edited by Sophie Berger and Emma Smith)


facepic

Teresa Kyrke-Smith is a postdoctoral researcher at the British Antarctic Survey, on the iSTAR grant. She works on using inversion methods to learn about the nature of basal control on the flow of Pine Island Glacier in West Antarctica. She completed her PhD two years ago in Oxford; her thesis focused on the feedbacks between ice streams and subglacial hydrology.

Brent Minchew is an National Science Foundation Postdoctoral Fellow also now based at the British Antarctic Survey.


 

 

Ice on fire at the Royal Society Summer Science Exhibition

Ice on fire at the Royal Society Summer Science Exhibition

The Royal Society Summer Science Exhibition (RSSSE) is a free public event 4-10th July 2016 in London. This is a yearly event that is made up of 22 exhibits, selected in a competitive process, featuring cutting edge science and research undertaken right now across the UK. The scientists will be on their stands ready to share discoveries, show you amazing technologies and with hands-on interactive activities for everyone! The Royal Society has historic origins – going back to the 1660s and today it is the UK’s national science academy working to promote, and support excellence in science and to encourage the development and use of science for the benefit of humanity. If you can get yourself down to London this week then it is definitely worth a look!

The Royal Society Summer Science Festival Exhibit Hall. Photo Credit: Thorbjörg Águstsdóttir

The Royal Society Summer Science Festival Exhibit Hall. Photo Credit: Jenny Woods


What is there to see?

This year there are a number of ice-related exhibits. The “4D science” exhibit uses X-ray computer tomography to look inside ice cream and the “Explosive Earth” exhibit showcases ice-volcano interactions in Iceland using earthquakes. The Summer Science Exhibition yearly attracts around 12,000 visitors. This is a unique opportunity to meet cutting edge scientists, discover their research and try out fun and engaging activities for yourself.

Left: The Explosive Earth presented by the Cambridge University Volcano Seismology Group. Left: 4D Science: Diamond Light Source, University of Manchester and University of Liverpool - Looking inside materials through time

Left: The Explosive Earth presented by the Cambridge University Volcano Seismology Group. Right: 4D Science: Diamond Light Source, University of Manchester and University of Liverpool – Looking inside materials through time. Photo Credit: Jenny Woods

Explosive Earth!

The Explosive Earth exhibit has been put together by the Cambridge Volcano Seismology group. They explore many applications of volcano seismology, from what we can learn about movement of molten rock (magma at more than 1000°C) in the Earth’s crust and rift zone dynamics, to the very structure of the earth itself. They currently focus their research in central Iceland where they operate an extensive seismic network in and around some very active volcanoes, many of which are under Europe’s largest ice cap Vatnajökull. The seismic network detects tiny earthquakes caused by the movement of magma beneath the surface, which often occurs under volcanoes prior to eruption. By studying these seismic events, they hope to be able to predict volcanic activity better in the future. Their exhibit at RSSSE showcases current research in this explosive field of volcano seismology.

 

Eyjafjallajökull – 2010: an explosive eruption that disrupted air traffic

The 2010 eruption at Eyjafjallajökull (image at the top of the page) occurred beneath a glacier, which caused a highly explosive eruption. When hot magma comes into contact with ice the magma cools and contracts and the ice turns to steam and rapidly expands. This shatters the solidifying magma and produces ash. The explosivity of the interaction, and the pressure of all the rising magma underground, blows the mixture of ash, volcanic gases and steam high into the air, creating an eruptive plume. The 2010 Eyjafjallajökull eruption produced an ash plume that reached up to 10 km (35,000 feet). The fine ash was then carried 1000’s of km by the wind towards Europe where it grounded over 100,000 flights.

Installing seismometers in a variety of locations around Iceland to monitor tiny earthquakes from magma movement under the surface

Installing seismometers in a variety of locations around Iceland to monitor tiny earthquakes from magma movement under the surface. Photo Credits – Left: Rob Green, Right: Ágúst Þór Gunnlaugsson

 

Bárðarbunga-Holuhraun – 2014: a gentle eruption that affected air quality

In 2014 a completely different kind of eruption happened in central Iceland, also originating from a volcano under the ice. Magma flowed underground from Bárðarbunga volcano, beneath Vatnajökull ice cap, fracturing a pathway so far from the volcano that when it erupted there was no ice at the surface. Without the magma-ice interaction, the eruption was comparatively gentle and the molten rock simply fountained out of the ground, reaching heights of over 150 m. No ash was produced, only steam and sulphur-dioxide. The amount of magma erupted was much greater than in 2010 (an order of magnitude higher), but there was no impact on air travel because there was no ash plume. The Explosive Earth team are investigating the 30,000 earthquakes that led up to this spectacular six-month eruption in Iceland, to try and find out more about what happened and why. The earthquakes tracked the progress of the molten rock as it moved underground, away from Bárðarbunga volcano to the eventual eruption site at Holuhraun, 46 km away.

The fountains of lava accompanied by clouds of steam and sulphur-dioxide. The magma flowed 46 km underground from Bárðarbunga volcano to the eventual eruption site at Holuhraun, where it erupted continuously for 6 months. Photo Credit: Tobias Löfstrand

The fountains of lava accompanied by clouds of steam and sulphur-dioxide. The magma flowed 46 km underground from Bárðarbunga volcano to the eventual eruption site at Holuhraun, where it erupted continuously for 6 months. Photo Credit: Tobias Löfstrand

Cambridge Volcano seismology group in front of the fissure eruption on the first day of the 2014-15 Bárðarbunga-Holuhraun eruption.

Cambridge Volcano seismology group in front of the fissure eruption on the first day of the 2014-15 Bárðarbunga-Holuhraun eruption. Photo Credit: Thorbjörg Águstsdóttir

What can monitoring these earthquakes tell us?

Monitoring volcanic regions in Iceland is important because eruptions are frequent and have wide-range impacts:

  • Explosive eruptions under ice can cause rapid and destructive flooding of inhabited areas downstream, and can propel huge ash clouds into the atmosphere, disrupting air travel around the globe.

  • Gentle eruptions, producing large lava flows, can release millions of tones of harmful gases, affecting the local population and in some cases the global climate.

Studying earthquakes helps to understand the physical processes that occur in volcanic systems, such as how molten rock intrudes through the Earth’s crust and how the centre of a volcano collapses. The more we understand about the behaviour of these systems, the better we can forecast eruptions.

“Explosive Earth” exhibits earthquakes and eruptions in Iceland in a fun interactive way. You can find out more details of the science behind why and how these eruptions happen and how it is possible to monitor volcanic activity in Iceland using earthquakes. As a taster of what you can see, try entering your postcode into their lava flow game to see how big the Holuhraun lava flow is and how far it travelled underground prior to erupting. Other interactive activities include making your own earthquake and testing your reaction times with an earthquake location game.

BANNER_exhibit

(Edited by Emma Smith and Sophie Berger)


tobba_headshot.jpgThorbjörg Águstsdóttir (Tobba) is a PhD student at the University of Cambridge studying volcano seismology. Her research focuses on the seismicity accompanying the 2014 Bárðarbunga-Holuhraun intrusion and the co- and post-eruptive activity. She tweets as @fencingtobba, for more information about her work see her website.

Image of The Week – A Game of Drones (Part 1: A Debris-Covered Glacier)

Image of The Week – A Game of Drones (Part 1: A Debris-Covered Glacier)

What are debris-covered glaciers?

Many alpine glaciers are covered with a layer of surface debris (rock and sediment), which is sourced primarily from glacier headwalls and valley flanks. So-called ‘debris-covered glaciers’ are found in most glacierized regions, with concentrations in the European Alps, the Caucasus, Hindu-Kush-Himalaya, Karakoram and Tien Shan, the Andes, and Alaska and the western Cordillera of North America. Debris cover is important for ice dynamics for several reasons:

  • A layer of surface debris thicker than a few centimetres suppresses ice ablation (Brock et al., 2010), as it insulates the underlying ice from atmospheric heat and insolation.
  • In contrast, a thin layer of debris serves to enhance melt rates through reduced albedo (reflectance) and enhanced heat transfer to underlying ice.
  • A continuous or near-continuous layer of debris can result in debris-covered glaciers persisting at lower elevations than, and attaining lengths which exceed those of their ‘clean ice’ counterparts (Anderson and Anderson, 2016).

Miage Glacier – the largest debris-covered glacier in the European Alps

The Ghiacciaio del Miage, or Miage Glacier, is Italy’s longest glacier and is the largest debris-covered glacier in the European Alps. It is situated in the Aosta Valley, on the southwest flank of the Mont Blanc/Monte Bianco massif. The glacier descends from ~3800 m to ~1700 m above sea level (a.s.l.) across a distance of around 10 km, and is fed by four tributary glaciers. The glacier surface is extensively debris-covered below ~2400 m a.s.l., and the average surface debris thickness is 0.25 m across the lower 5 km of the glacier (Foster et al., 2012).

 

Figure 2: Up-glacier view of Miage Glacier, in which three of the glacier’s four tributaries are visible – from upper centre-left: Tête Carée Glacier, Bionnassay Glacier, Dome Glacier.

Figure 2: Up-glacier view of Miage Glacier, in which three of the glacier’s four tributaries are visible – from upper centre-left: Tête Carée Glacier, Bionnassay Glacier, Dome Glacier.

Glacier surveying using Unmanned Aerial Vehicles

Researchers from Northumbria University, UK, acquired these images of the glacier using a lightweight unmanned aerial vehicle (UAV) during a recent field visit to Miage Glacier. During the visit the team carried out a range of activities including the installation and maintenance of a network of weather stations and temperature loggers across the glacier and geomorphological surveying of the glacier and its catchment, whilst undergraduate students collected data for their final-year research projects. The UAV imagery reveals the emergence of surface debris cover from beneath winter snow cover and the persistence of a channelized hydrological network in the snowpack, characterised as a cascade of streams and storage ponds. A recent study by Fyffe et al. (2015) found that high early-season melt rates and runoff concentration in intermoraine troughs promotes the development of a channelized subglacial hydrological system in mid-glacier areas, whilst the drainage system beneath continuously debris-covered areas down-glacier is largely inefficient due to lower melt inputs and hummocky topography.

(Edited by Emma Smith and Sophie Berger)


Matt Westoby is a postdoctoral researcher at Northumbria University, UK. He is a quantitative geomorphologist, and uses novel high-resolution surveying technologies including repeat UAV-based Structure-from-Motion to quantify surface processes and landscape evolution in glacial and ice-marginal environments. Fieldwork on the Miage Glacier in June 2016 was supported in part by an Early Career Researcher Grant from the British Society for Geomorphology. He tweets as @MattWestoby Contact e-mail: mjwestoby@gmail.com

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