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Cryospheric Sciences

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Image of the Week – Karthaus Summer School 2018

Beautiful and cozy Golden Rose hotel on the left; blissful and small Italian village, Karthaus, on the right [Credit: Rohi Muthyala].

Nearly every year since the late 90s, during the summer, the picturesque Karthaus has hosted 10-day glaciology course. This school is a platform for glaciologists to explore, learn and expand their knowledge base. This helps researchers become multi-faceted: to view glaciology from the perspective of those specializing in other backgrounds such as hydrology, geomorphology, oceanography, etc. which complement one another in defining glaciology. Along with the intense course work, one can wholeheartedly cherish the exotic food, cozy resort, spellbinding views and especially, more and more wine!


Time to learn

Day used to start at 8 am with a healthy breakfast and then we head out to Katharinaberg to attend the lectures. Morning session of the course composed of four lectures with coffee breaks in between to keep us alert. These lectures were on a gamut of topics including numerical and analytical modeling, continuum mechanics, glacier hydrology, mass balance of the ice sheets, thermodynamics of ice, geophysical methods, geodynamics, ice core analysis, polar oceanography and geomorphology, etc. Lectures began with basics in every topic and gradually evolved into complex concepts, enabling students understand the subject better, irrespective of their specialization. After four hours of lectures, we, surrounded by lustrous green hills, enjoyed a delicious three-course lunch.

Afternoon session was all about application of the concepts learned in the morning into numerical exercises and group projects. We were divided into 12 groups to work as a team for a group project. Each group was assigned a topic and a teacher to work with. Results from the group projects presented on the last day of the course, astonished me by the level of research we could accomplish in 10 days, showing the amount of knowledge gained through the program.

Outdoor afternoon session in Kartharinaberg [Credit: T. Blunier]

After school

School ended at 5 pm, leaving us with ample time to relax before dinner. While some students enjoyed it hiking, trail running and chilling in the sauna, I spent this time exploring Karthaus with a bunch of friends I made at the school and tried to capture the beauty of nature with my camera. Then was the best part of the evenings – a five-course dinner with lots of wine and stories from our fellow glaciologists. I have never had such an exotic five-course meal, which was so tasty that I couldn’t help but overeat. To top the delicious food, we had musical performances by Frank Pattyn and Johannes Oerlemans. I was amazed to know that most of the teachers have their own specialty with an instrument and that it’s a tradition at Karthaus to enjoy the evenings with their performances. After a two-hour long dinner, we moved to the bar next to the restaurant and continued our entertainment with games, wine and chatting. I wished there were more than 24 hours in a day to spend at Karthaus. This summer school is a complete package of education and entertainment.

Dinners at karthaus, with 5-course meal, wine and music (Frank Pattyn on Piano and Johannes Oerlemans on Bass) [Credit: Rohi Muthyala]

Entertainment after dinner with wine, games, chatting and as you can see, some map reading as well. Apparently, this year students are the most solemn group ever [Credit: Rohi Muthyala].

Adding to the fun, in the middle of the course, we had a day-off that most of us spent by going on an excursion to the Otztal Alps. A bus ride to Kuzras, a cable car to the top of Hochjochferner and hike down into the valley led us to the edge of the glacier where some stepped onto a glacier and/or entered an ice cave for the first time in their life. We stopped by Bellavista (Schonne Aussicht hut) for a hot meal and drinks before hiking higher onto the Italian Alps. Though we had been lucky with perfect clear skies throughout the course, we got a cloudy weather on our day-off to the Alps. Nonetheless, the experience of going well above the clouds in the cable car was the best start for the day.

Hiking on a cloudy day from the top of Hochjochferner gletscher to bellavista [Credit: Rohi Muthyala].

All in all

This summer school would be an intense and beneficial experience for students in all stages of education. Be it a beginner in glaciology or an experienced final year Ph.D. student, I think the course has a lot to offer to every student. Especially to the students with no glaciology background, this could be a place to learn the basics and understand how to look for answers you are trying to find. With three years of experience going to Greenland for research as an Arctic hydrologist, I was still ignorant in some concepts (such as geomorphology, geodynamics, thermodynamics, etc) that are not directly related to my dissertation. This program opened paths for understanding those concepts in a productive way. I highly recommend this summer program to every graduate student studying glaciology and especially to those who are not from Europe, with few opportunities such as this to learn the basics in wide range of topics from glaciology.

Another best outcome of this course was the opportunity to interact with fellow students and build a network for future collaborations. AGU and EGU have been mostly exclusive, and this provided an opportunity for me (from an American university) to get to know my fellow researchers from other parts of the world. I would also like to highlight the women participation in this course (roughly 50%) and appreciate the organizing committee’s effort to encourage more women in this field. Huge thanks to the organizing committee and all the teachers for their effort in making this an incredible experience. Special thanks to the convener, Johannes Oerlemans, for coordinating such a quintessential summer school.

Class photo in Katharinaberg [Credit : W.J. van de Berg]

Edited by Violaine Coulon


Rohi Muthyala is a PhD candidate from Rutgers University (New Jersey, USA), working with Asa Rennermalm. Muthyala comes from a multidisciplinary background of atmospheric, environmental sciences and geography, and currently focuses her research on Arctic hydrology and hydrological modeling. Objective of her dissertation is to model surface hydrological processes influencing the transport of meltwater over the surface of Greenland ice sheet.

Image of the Week – Promoting interdisciplinary science in the Arctic: what is IASC?

Image of the Week –  Promoting interdisciplinary science in the Arctic: what is IASC?

The Arctic is one of the fastest changing regions on the Earth, where climate change impacts are felt both earlier and more strongly than elsewhere in the world. As an integral part of the Earth system, the Arctic is shaped by global processes, and in turn, Arctic processes influence the living conditions of hundreds of millions of people at lower latitudes. No one country or community can understand the Arctic alone. Big Arctic science questions require ambitious Arctic science – but researchers sometimes need a little help bridging both national and disciplinary boundaries. That‘s a lofty mission, but how does the International Arctic Science Committee (IASC) achieve it? Read on!


How does IASC support science?

Each IASC member country appoints up to two members to each of IASC’s 5 scientific Working Groups (Atmosphere, Cryosphere, Marine, Social & Human, and Terrestrial). These groups allocate IASC‘s scientific funds for small meetings, workshops, and projects. Follow the to see the science priorities of each group, find out about upcoming Working Group activities, and explore the expertise of their members!

Understanding the future of the Arctic means we need to invest in the Arctic researchers of today. Therefore, At least 40% of IASC’s working group funds must be co-spent with another working group, to encourage interdisciplinary projects. Check out upcoming events in 2019 like the Year Of Polar Prediction Arctic Science Workshop, High Latitude Dust Workshop, Snow Science Workshop, and Network on Arctic Glaciology meeting – just to name a few!

What else does IASC do?

IASC convenes the annual Arctic Science Summit Week (ASSW), which provides the opportunity for coordination, cooperation and collaboration between the various scientific organizations involved in Arctic research and to economize on travel and time. In addition to IASC meetings, ASSW is a great opportunity to host Arctic science meetings and workshops. ASSW2019 will be in Arkhangelsk, Russia.

IASC influences international Arctic policymakers by being an observer to the Arctic Council and contributing to its work. IASC projects include contributing experts to an assessment on marine plastic pollution in the Arctic, helping coordinate reviews for the first Snow, Water, Ice, and Permafrost Assessment (SWIPA) report, and co-leading the Arctic Data Committee & Sustaining Arctic Observing Networks.

Supporting Early Career Researchers

At least one third of IASC‘s scientific funds must be spent on supporting early career researchers (see the image of the week)! In addition, the IASC Fellowship Program is meant to engage early career researchers in the Working Groups and give them experience in helping lead international and interdisciplinary Arctic science activities. Applications are now open and due by 19 November!

IASC convenes the annual Arctic Science Summit Week (ASSW), which provides the opportunity for coordination, cooperation and collaboration between the various scientific organizations involved in Arctic research and to economize on travel and time. In addition to IASC meetings, ASSW is a great opportunity to host Arctic science meetings and workshops. ASSW2019 will be in Arkhangelsk, Russia.

Get Involved!

Do you have a great idea that you think IASC might want to support? Or want to learn more about IASC? Connect with IASC on Facebook, and sign up to receive our monthly newsletter! You are also encouraged to reach out to the relevant national/disciplinary IASC Working Group experts, IASC Council member, and the IASC Secretariat.

Further reading

Edited by Adam Bateson


Allen Pope is the IASC Executive Secretary. IASC scientific funds are provided from national member contributions. The IASC Secretariat in Akureyri, Iceland is supported by Rannís, the Icelandic Centre for Research. The IASC Secretariat is responsible for the day-to-day operations and administration of IASC. Allen also maintains an affiliation as a Research Scientist at the National Snow and Ice Data Center at the University of Colorado Boulder where he continues research based on remote sensing of glacier mass balance and surface hydrology. You can find out more about Allen and his research at https://about.me/allenpope. He also enjoys sharing and discussing polar science with the public and tweets @PopePolar.

Do clouds affect melting over Antarctic ice shelves?

Schematic showing the effects of cloud microphysics on the radiative properties of clouds for shortwave solar radiation (a & b) and longwave terrestrial radiation (c & d) [Credit: Ella Gilbert].

The Antarctic Peninsula is the ‘canary in the coalmine’ of Antarctic climate change. In the last half-century it has warmed faster than most other places on Earth, and considerable change has consequently been observed in the cryosphere, with several ice shelves collapsing in part or in full. Representing this change in models is difficult because we understand comparatively little about the effect of atmospheric processes on melting in Antarctica, especially clouds, which are the main protagonists of this Image of the Week…


The Antarctic Peninsula: a part of the southern continent that is surrounded by ice shelves, but also a place that has seen rapid and dramatic changes in the last decades. Until recently, the Antarctic Peninsula was one of the most rapidly warming regions on Earth, with annual mean surface temperatures rising by as much as 2.5°C between the 1950s and early 2000s in some places (Turner et al., 2005; 2016).

That warming has been linked to the demise of the region’s ice shelves: since 1947, more than half of the peninsula’s ice shelves have thinned, lost area, or collapsed entirely (Cook & Vaughan, 2010). Most recently, that includes Larsen C, whose area was reduced by 12% in July 2017 following a calving event where an iceberg four times the size of London broke away from the ice shelf. As a result, the ice shelf has slipped down the rankings from the 4th largest ice shelf on the continent to the 5th largest.

 

What makes ice shelves melt?

Evidence suggests that ice shelves on the peninsula are being warmed mostly from the top down by the atmosphere. This is contrary to what’s happening on other Antarctic ice shelves, like those in West Antarctica that are being eroded from beneath by the warming ocean. Atmospheric processes are much more important over peninsula ice shelves than those elsewhere on the continent.

To understand the effect of the atmosphere on melting at the top of ice shelves, we need to know how much energy is entering the surface of the ice shelf, how much is leaving, and use what’s left over to determine whether there’s residual energy available to melt the ice. That’s the general principle of the surface energy balance, and it’s called a ‘balance’ because it is usually just that – the amount of energy flowing into and out of the ice shelf averages out over the course of say, a year, to produce a net zero sum of energy left for melting. However, there are times when this balance can become either negative, leading to growth of the ice shelf, or positive, leading to ice loss via melting.

 

What affects the surface energy balance?

Many different processes influence the surface energy balance, such as weather patterns and atmospheric motion. For instance, when warm, dry air blows over an ice surface, which happens during ‘foehn‘ wind events (German readers will know this means ‘hairdryer’: a descriptive name for the phenomenon!), this can produce a surplus of energy available for melting (Grosvenor et al., 2014; King et al., 2017; Kuipers Munneke et al., 2018). If the surface temperature reaches 0°C, melting occurs.

 

What do clouds have to do with it?

Clouds also greatly influence the surface energy balance by affecting the amount of radiation that reaches the surface. The amount of incoming solar (shortwave) radiation that reaches the surface, and the amount of terrestrial (longwave) radiation that escapes is affected by what stands in the way – clouds. Of course, this obstacle is important for the surface energy balance because it affects the balance between the energy flowing into and out of the surface. However, the fine-scale characteristics of clouds (aka ‘microphysics’) produce different, often interacting and sometimes competing, effects on the surface energy balance, some of which are shown in the schematic above. Examples of these properties include:

  • Water phase (how much ice and liquid there is)
  • Number concentration (how many particles)
  • Particle size
  • Ice crystal shape

The amount of ice and liquid in a cloud can affect how much energy it absorbs, reflects and emits – for instance, the more liquid a cloud contains, the more energy it emits towards the surface, because it is thicker and tends to be warmer than a cloud with lots of ice. However, clouds made up of lots of tiny liquid droplets also tend to be brighter than ice clouds containing larger crystals, which means they reflect more incoming solar radiation back into space. This example is a typical one where different microphysical properties cause competing effects, which makes them difficult to separate from each other.

 

Radiative forcing (RF, solid bars) and Effective radiative forcing (ERF, hatched bars) of climate change during the Industrial Era (1750-2011) [Credit: adapted from IPCC Fifth Assessment Report, Figure 8.15: pp. 697].

What do we know about Antarctic clouds?

The short answer is: not that much. Clouds are the largest source of uncertainty in our estimates of global climate change (check out the huge range of error in the estimates of cloud-driven radiative forcing in the figure above, from the IPCC’s most recent report), and the science of Antarctic clouds is even more unclear because we don’t have a great deal of data to base our understanding on. To measure clouds directly, we need to fly through them – a costly and potentially dangerous exercise, especially in Antarctica.

 

Flying through a gap in cloud near Jenny Island on the approach to Rothera research station, on the Antarctic Peninsula, at the end of a data collection flight in November 2017 [Credit: Ella Gilbert].

Filling the gap

In somewhere like Antarctica where we don’t have much observational data, we have to rely on other tools. That’s where computer models can be really useful – so long as we can be confident in the results they produce. Unfortunately, that’s part of the problem. Cloud properties and their effects on the surface energy balance are complex: we know that much. But modelling those properties is even more complex, because we have to simplify things to be able to turn them into computer code.

There is hope though! Recent studies (e.g. Listowski et al., 2017) have shown that models can more realistically represent Antarctic cloud microphysics if they use more sophisticated ‘double moment’ schemes, which are able to simulate more microphysical properties. With more accurate microphysics comes better representation of the surface energy balance, and improved estimates of melt over Antarctic ice shelves.

 

Further reading

  • On the effect of foehn on wintertime melting over Larsen C:

Kuipers Munneke, P., Luckman, A. J., Bevan, S. L., Gilbert, E., Smeets, C. J. P. P., Van Den Broeke, M. R., Wang, W., Zender, C., Hubbard, B., Ashmore, D., Orr, A. King, J. C. (2018). Intense winter surface melt on an Antarctic ice shelf. Geophysical Research Letters 45, 7615–7623. doi:10.1029/2018GL077899

  • On clouds in Antarctica:

Lachlan-Cope, T. (2010). Antarctic clouds. Polar Research 29 (2), 150–158. doi:10.1111/j.1751-8369.2010.00148.x

  • On modelling cloud microphysics over the Antarctic Peninsula:

Listowski, C., & Lachlan-Cope, T. (2017). The Microphysics of Clouds over the Antarctic Peninsula – Part 2: modelling aspects within Polar WRF. Atmospheric Chemistry and Physics 17, 10195-10221. doi:10.5194/acp-17-10195-2017

Edited by Clara Burgard


Ella Gilbert is a PhD student at the British Antarctic Survey, where she uses climate modelling and observational data to understand the drivers of melt on the Larsen C ice shelf. She’s a big fan of clouds, polar science, and science communication. You can find her on Twitter @Dr_Gilbz, on her website www.larsenc.com, or the old fashioned way by email.

Image of the Week – On thin [Arctic sea] ice

Thin, ponded sea ice floes in Nares Strait [Credit: Christopher Horvat and Enduring Ice]

Perhaps the most enduring and important signal of a warming climate has been that the minimum Arctic sea ice extent, occurring each year in September, has declined precipitously. Over the last 40 years, most of the Arctic sea ice has thus been transformed to first-year ice that freezes in the winter and melts in the summer.           
Concern about sea ice extent and area is valid: since sea ice is a highly reflective surface, a reduction of its area has a significant effect on the energy budget of Earth’s climate. Yet it is well-documented that, in the summertime, when sunlight is strongest, the biggest changes to sea ice volume are coming from effects not associated with changes to ice area, but with changes to sea ice thickness, like increased melt ponding. The change from thick, reflective multi-year summer sea ice to thin, ponded, less-reflective first-year ice are seen throughout the Arctic. In places like Nares Strait, the region of the Canadian Arctic that separates Canada from Greenland (seen above), commonly referred to as the “last ice area”, this is true as well.


The “Enduring Ice” Expedition

In the summer of 2016 and 2017, 4 filmmakers and a scientist (that’s me!) set out to examine Nares Strait, the area that separates Ellesmere Island in Canada from Northern Greenland (see map below). The Strait has been designated the “last ice area” by the World Wildlife Fund, a region which is expected to remain fully covered in thick sea ice even as the rest of the Arctic sea ice cover melts.

Nares Strait [Credit: Enduring Ice, LLC]

Yet when we arrived, what we found was anything but the promised land of thick, multi-year ice. Instead, all of the ice we encountered was thin, heavily ponded, and fragmented. In decades past, the presence of multi-year floes would dam Nares Strait, allowing ice-free passage for kayakers. Instead, the fractured ice poured through the strait, making passage impossible. Faced with an impassable strait, we resorted to pulling the kayaks over the land, moving a total of 100 km in 45 days.

The “Enduring Ice” Expedition [Credit: Christopher Horvat and Enduring Ice]

Most projections have the Arctic totally ice-free in September by 2050, meaning there will truly be no multi-year ice left at all. Yet as the Arctic still cools dramatically in winter, during the summer months (from May to July) when solar radiation is highest, the total area of the Arctic covered in sea ice is still high, but now covered by thin first-year ice. At the same time, the ongoing warming has thinned the Arctic sea ice by more than half (Kwok, 2008).

The albedo of first year ice can be half or less that of multi-year thicker ice (Light, 2008). Since the Arctic has thinned substantially over the last 40 years, the consequences of this thinning on the Arctic and Earth climate system are dramatic.

More and more solar radiation is absorbed by thinner ice. Excess solar absorption leads to ocean and atmospheric warming, and to more sea ice melting, a process known as the ice-albedo feedback. It was previously thought that regions covered by sea ice where inhospitable to photosynthetic life. However, thinning sea ice is likely responsible for the increase in phytoplankton blooms in the Arctic, as more light is transmitted through the thinner ice.

The Arctic sea ice cover is rapidly transitioning from thick, multi-year ice to thin, ponded, first-year sea ice.  As we can see, this thinning is resulting in a totally new Arctic climate system.

Further Reading

Edited by Violaine Coulon and Sophie Berger


Chris Horvat is a NOAA climate and global change postdoctoral fellow at Brown University in Providence, RI.  He tweets as @chhorvat and you can also reach him on his website.

Image of the Week — Cryo Connect: connecting cryosphere scientists and information seekers

Image of the Week — Cryo Connect: connecting cryosphere scientists and information seekers

Communicating scientific findings toward non-experts is a vital part of cryosphere science. However, when it comes to climate change and its impact, the gap between scientific knowledge and human action has never been so evident (see for instance, the publication of the latest IPCC special report). Today, our image of the week features an interview with Cryo Connect, a new initiative for more efficient flow of information between cryosphere scientists and information seekers.


Why have you decided to come up with an initiative like Cryo Connect?

Currently, information seekers such as journalists, policy makers, teachers and stakeholders often resort to internet search engines to find experts for answering specific questions about the cryosphere. Or they return to the same expert they have interacted with in the past. Either way, it is unlikely that they end up receiving information from the expert that knows most about the topic, or even in the preferred language. Some organizations have their own science outreach portals, but a truly global and inclusive network of cryosphere experts willing to provide insights to those seeking information has been lacking. For this reason, we established Cryo Connect.

Number of Cryo Connect experts for each cryospheric component. [Credit: Cryo connect]

How does it work exactly?

Cryo Connect is run as a non-profit organization. We are an official EGU Cryospheric Sciences partner and provide a free, online gateway through which experts and information seekers can reach out. Here, not only can information seekers find answers, but scientists can also actively promote their latest findings, pushing press releases (screened but unmodified by Cryo Connect) towards information seekers. All cryosphere scientists globally can sign up as experts allowing them to boost their visibility (especially with respect to those ranking high on internet search engines), irrespective of their career stage, ethnicity, gender or the languages that they master.

Number of Cryo Connect experts for each cryosphere region. [Credit: Cryo connect]

How has Cryo Connect been doing so far?
Although still in our first year, by October 2018 Cryo Connect has already grown to a community of 98 experts based in 22 countries across the planet. Together, they can provide information on all components of all cryospheric regions in the world – in 19 different languages! Researchers make up about two-fifths of the expert database, while PhD students, senior researchers and professors each constitute a ⅕ part. Lots of knowledge to go around.

Career stage of Cryo Connect experts. [Credit: Cryo connect]

What’s the take-home message for scientists?

That all cryosphere scientists around the globe are invited to sign up as a Cryo Connect expert to increase their visibility to the media and other information seekers. The platform works best, and attracts more information seekers with an even larger expert population from all corners of the planet. And don’t forget to tweet about your latest peer-reviewed publication using the @CryoConnect Twitter handle for increased media exposure!

Edited by Sophie Berger


Cryo-connect is an initiative run by Dirk van As, Faezeh Nick, William Colgan and Inka Koch

Image of the Week – Greenland’s fjords: critical zones for mixing

Image of the Week – Greenland’s fjords: critical zones for mixing

One of the most challenging research questions to address in the Arctic is how freshwater discharge from Greenland’s largest glaciers affects the biogeochemistry of the ocean. Just getting close to the calving fronts of these large marine-terminating glaciers is difficult. Fjords, hundreds of kilometers long and full of icebergs which shift with the wind and roll as they melt, make the commute a little difficult. Navigating these fjords to within a few kilometers of Greenland’s largest glaciers requires a combination of luck, skillful handling of small boats and a ‘fortune favors the brave’ attitude to sampling which would probably upset even the most relaxed of University Health and Safety Officers. The limited field data we have from Greenland’s fjords must therefore be combined with other data sources in order to understand what happens between glaciers and the ocean.


The Challenge

The amount of freshwater discharged from the Greenland ice sheet into the ocean increases in response to climate change. This may affect both the fisheries which support the island’s economy and the carbon sink associated with fjord systems – the largest per unit surface area in the ocean. As a consequence, we need to assess how exactly this cold freshwater will affect the ocean. To do so requires collaboration of scientists with different backgrounds:

  • glaciologists, to understand the different components of freshwater released (ice melt, surface runoff, subglacial discharge),

  • physicists, to understand the fate of freshwater within a dynamic water column,

  • chemists, to understand how the availability of resources shifts in response to increasing freshwater

  • biologists, to understand the net effects of multiple physio-chemical changes to the environment on living organisms.

In the context of climate change it is also always worth remembering that the increase in Greenland ice sheet discharge occurs alongside other changes in the Arctic, such as the disappearance of sea ice and warming of the atmosphere and ocean. Thus, we really must unleash 4-dimensional thinking in order to understand the processes that are currently at work in the whole Arctic.

Recent work around Greenland has shown that one particularly important factor in determining how a glacier affects downstream marine ecosystems is whether it terminates on land or in the ocean. When a glacier sits in the ocean and releases meltwater at depth, this cold freshwater rapidly mixes with deep nutrient-rich seawater. This buoyant mix, known as an upwelling plume, rises upwards in the water column. These buoyant plumes act as a ‘nutrient pump’ bringing macronutrients from deep seawater to the surface and thus driving quite pronounced summertime phytoplankton blooms. Around Greenland, these blooms are quite remarkable. Summertime productivity in the open Atlantic is generally quite limited, while the main time of year when phytoplankton bloom is spring. In several of Greenland’s fjords, however, phytoplankton bloom over the meltwater season (around May-September). Understanding how these upwelling-driven blooms operate, and more importantly how they will change in the future, is a formidable challenge. There is an almost complete lack of either physical or biogeochemical data within a few kilometers of most large marine-terminating glaciers and thus our ability to quantify the relationship between discharge and downstream productivity is limited.

Contrasting effects of meltwater around Greenland depending on where the glacier terminates with respect to sea-level. [Credit: Fig 3 from Hopwood et al., (2018)].

Modelling what we cannot measure

Fortunately however, the field of subglacial discharge modelling is relatively well advanced. Since the 1950s, plume models have been used to describe reasonably well the subglacial discharge downstream of glaciers. Whilst all of Greenland’s glacier fjords are unique, we can at least model the processes that underpin the ‘nutrient pump’ leading to such unusual summertime productivity around Greenland.

One thing is particularly clear from the use of these models. The depth at which a glacier sits in the water column is a major factor for the magnitude of the upwelling effect. If a glacier retreats inland, this is generally bad news for downstream marine productivity. As marine-terminating glaciers retreat, the nutrient pump rapidly collapses if the glacier moves into shallower water – irrespective of what happens to the volume of discharged meltwater. For a majority of Greenland’s glaciers for which the topography under the glacier has been characterised, this will be indeed the case under climate change: as the glaciers retreat inland, their grounding lines will get shallower and shallower. The ‘nutrient pump’ associated with each one will therefore also diminish.

Outlook

There are still many things we don’t know about environmental change around Greenland, as our almost complete lack of data outside the meltwater season and very close to marine-terminating glacier termini still hinders our understanding of some critical processes. Only by adopting more inter-disciplinary methods of working and deploying new technology will these data-deficiencies be addressed.

Further reading

 

Edited by Sophie Berger and Clara Burgard


Mark Hopwood is a postdoc at GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany. He investigates how environmental changes, such as increasing freshwater discharge in the Arctic or declining oxygen in the tropics, affect the availability of nutrients to biota in the marine environment. By using a combination of fieldwork and targeted process studies the main goal is to identify and quantify biogeochemical feedbacks that act to amplify or dampen the response of marine biota to perturbations. He tweets as @Markinthelab. Contact Email: m.hopwood@geomar.de

Image of the Week – Oh Sheet!

Image of the Week – Oh Sheet!

The Antarctic and Greenland ice sheets are major players in future sea level rise. Still, there is a lot about these ice sheets we do not understand. Under the umbrella of the World Climate Research Programme, the international scientific community is coming together to improve ice sheet modelling efforts to better grasp the implications of climate change for ice sheet evolution, and consequently, sea level rise…


What are ice sheets?

An ice sheet is a massive chunk of glacier ice that sits on land – covering an area greater than 50,000 square kilometres (or 1.6 times the size of Belgium) by the official definition. Currently, the only two ice sheets on Earth are in Antarctica and Greenland. Ice in ice sheets flows from inland toward the coast under gravity. Due to the geothermal heat flux, ice sheets are usually warmer at the base than on the surface. When basal melting occurs, the melted water lubricates the ice sheet and accelerates the ice flow, forming fast-flowing ice streams. When ice flows down a coastline into the ocean, it may float due to buoyancy. The floating slab of ice is called an ice shelf (see these previous posts for more on ice shelves). The boundary that separates the grounded ice and floating ice is called the grounding line.

 

Why do we care about ice sheets?

The most uncertain potential source of future sea level rise is the contribution from ice sheets. According to observations, the Greenland and Antarctic ice sheets have contributed approximately 7.5 and 4 mm of sea level rise respectively over the 1992-2011 period, and the contribution is accelerating. Knowing how the ice sheets will behave under future emission scenarios is crucial for risk assessment and policy-making (see this previous post for more on Antarctic ice sheets).

In addition to the direct impact on sea level rise, ice sheets interact with other components of the climate system. For example, ice discharge affects ocean circulation and marine biogeochemistry; changes in orography influence the atmosphere condition and circulation. In turn, the ice sheets gain mass primarily from snow fall, and lose mass through surface melting, surface sublimation, basal melting and ice discharge to the ocean, which are influenced by atmospheric and oceanographic processes. In Antarctica, the mass loss due to basal melting and iceberg calving is larger than snowfall accumulation. The Greenland Ice Sheet is also losing mass through iceberg calving and surface water runoff.

 

What’s CMIP?

Global coupled climate models are developed by different groups of scientists around the world to improve our understanding of the climate system. These models are highly complex, representing interactions between the ocean, atmosphere, land surface and cryosphere on global grids. The Coupled Model Intercomparison Project (CMIP) is a collaborative framework which provides a standard experimental protocol for the different models. The protocol includes a range of greenhouse gas emissions scenarios for future climate projections. Model output is made publicly available and forms the basis for assessments such as the Intergovernmental Panel on Climate Change (IPCC) reports. The latest phase (CMIP6) is underway now.

 

What’s ISMIP6?

Ice sheets were considered as passive elements of the climate system previously and were not explicitly included in the CMIP process. However, observations of the rapid mass loss associated with dynamic change in ice sheets highlight the need to couple ice sheets to climate models. New developments in ice sheet modelling allow previously-omitted key processes which affect ice sheet dynamics on decadal timescales, such as grounding-line migration and basal lubrication, to be simulated with higher confidence.

ISMIP6 is an international effort designed to ensure that projections from ice sheet models are compatible with the CMIP6 process, bringing together scientists from over twenty institutions (Fig. 2). It aims to improve sea level projections, exploring sea level contribution from the Greenland and Antarctic ice sheets in a changing climate and investigating interactions between ice sheets and the climate system.

 

ISMIP6 Experiments

As shown in Figure 1, the objectives of ISMIP6 rely on three distinct modeling efforts:

  1. CMIP atmosphere-ocean general circulation models (AOGCM) without an ice sheet component
  2. standalone dynamic ice sheet models (ISMs) that are driven by forcing provided by CMIP
  3. fully coupled atmosphere-ocean-ice sheet models (AOGCM-ISMs).

 

In the first phase, ISMIP6 will compare output from different ice sheet models run in ‘standalone’ or ‘offline coupled’ mode. This means that they receive forcings from the climate model components like the ocean and atmosphere without feeding back. These experiments will be used to explore the uncertainty associated with ice sheets physics, dynamics and numerical implementation. In particular, ISMIP6 is currently focused on gaining insight into the uncertainty in ice sheet evolution resulting from the choice of initialization methods (the initMIP efforts for the Greenland and Antarctic ice sheets) and understanding the response of the Antarctic ice sheet to a total loss of the ice shelves (ABUMIP).

The model output of the initMIP simulations for Greenland is now publicly available.

Fig. 2: Participants of ISMIP6 standalone ice sheet modeling.

 

ISMIP6 workshop

Regular meetings are organised to update and facilitate communication between the participants. The most recent workshop was hosted in the Netherlands during 11 – 13 September 2018. The topic of the workshop was “Developing process-based projections of the ice sheets’ contribution to future sea level.” Participants aimed to evaluate the output of the CMIP6 climate models and obtain forcing for standalone ice sheet model experiments. During the workshop, scientists made progress on establishing the experimental protocols for the ice sheet model simulations that will be discussed in the IPCC sixth assessment report.

Fig.3: Participants in the ISMIP6 workshop in Leiden, Netherlands [Credit: Heiko Goelzer]

Further reading

Edited by Lettie Roach and Clara Burgard


Sainan Sun does her postdoctoral research with Frank Pattyn at Université Libre de Bruxelles (ULB). She achieved her doctoral degree in 2014, majoring in ice sheet modeling at Beijing Normal University, Beijing, China. In her PhD study, she applied the BISICLES ice sheet model to Pine island glacier, Aurora drainage basin and Lambert-Amery drainage basin to describe the dynamical response of the Antarctic ice sheet to perturbations in boundary conditions. For the project at ULB, she aims to investigate the ice shelf features based on data acquired in Roi Baudouin ice shelf, Antarctica, and to estimate the potential instability of the Antarctic ice sheet using the f.ETISh ice sheet model. Contact Email: sainsun@ulb.ac.be

Image of the Week – Climbing Everest and highlighting science in the mountains

Image of the Week – Climbing Everest and highlighting science in the mountains

Dr Melanie Windridge, a physicist and mountaineer, successfully summited Mount Everest earlier this year and has been working on an outreach programme to encourage young people’s interest in science and technology. Read about her summit climb, extreme temperatures, and the science supporting high-altitude mountaineering in our Image of the Week.


It’s bigger than it looks! Experiencing the majesty of Everest

In April/May this year I climbed Mount Everest. To the top. It was two months of patient toil but in surroundings so majestic, impressive and inspiring. The Western Cwm (an amphitheatre-like valley shaped by glacial erosion) is vast, the summit ridge is steep and Khumbu Glacier was fascinating in itself. Our base camp was on the glacier and it changed daily in subtle ways – the ice melted, the rocks moved, the paths morphed. And the icefall was slightly different each time I passed through – the route changing through a collapsed area, a crevasse widening, or the rope buried by ice-block debris fallen from above. It’s a wonderful, interesting place and I am grateful to have experienced it. You can read more about the climb on my personal blog.

Fig.2: The view up the Western Cwm from Camp 1. Lhotse can be seen in the distance and the summit of Everest mid-left. [Credit: Melanie Windridge].

Everest, of course, is extreme. It is steep almost everywhere, so you barely get a let-up anywhere beyond the Western Cwm. The temperature differences are extreme too – it is extremely hot or extremely cold. I took a couple of temperature loggers with me to the summit (one in a base-layer pocket under my down suit and one in an outer pocket of my rucksack). You can see from the graph of summit night (the climb from Camp 4 to the summit of Everest) (Fig. 3) how the temperature varied by tens of degrees.  Since climbers dress for the coldest temperatures, this can be quite uncomfortable when the sun comes out.  The temperature on summit night got down to about -25°C, but during the day it rose to 10 degrees or more so that we were sweating into our down suits.

 

Fig.3: Graph showing the readings from two separate temperature loggers on summit night – one in a base-layer pocket under the down suit (Down suit temperature) and one in an outer pocket of the rucksack (Air temperature). The temperature rises quickly after sunrise, which was experienced on the summit [Credit: Melanie Windridge and Scott Watson].

Sharing the Science of the Summit

It was science that really got me interested in Everest, when I realised that the main reason the British had succeeded in 1953 but hadn’t in the 1920s and 30s was because of scientific understanding and the state of technology. But so often we don’t talk about the science that supports us in these great endeavours; instead we put it all down to the strength of the human spirit. I think we need to talk about both.

As part of my climb, I have been working on an outreach project to highlight how science and technology have improved safety and performance on Everest. I have made Science of Everest videos for the Institute of Physics YouTube channel and will be giving public talks. I wanted to show how science supports us and what has improved in recent decades to contribute to the falling death rate on Everest.

In the video series I look at changes in weather forecasting, communications, oxygen, medicine and clothing. We also consider risk and preparation – videos that went out before I left for Everest – because, as a scientist, I looked into past data to see how I could give myself the best chance of reaching the summit and returning safely.

 

 

Communication has improved not only because we have a greater variety than was available to the first ascentionists or the early commercial climbers (we have satellite phones, mobile/cell-phones and WiFi now), but also because everything is a lot smaller. Electronic components have greatly reduced in size so that radios used on the mountain now are small and handheld in comparison to the bulky sets of the 1950s (see video above).

 

 

Of course, the implication of the project is wider than just Everest. I am interested in the importance of science and exploration in general. For me, Everest is an icon of exploration – the way that human curiosity, ingenuity, determination and endurance come together to drive us forward. Reaching into the unknown is good for us, on a societal level and on a personal level. I hope to give an appreciation of the value of science in our lives, give students an insight into interesting careers that use science, and show the value of doing things that scare us!

 

Further reading

Edited by Scott Watson and Clara Burgard


Dr Melanie Windridge is a physicist, speaker, writer… with a taste for adventure. She is Communications Consultant for fusion start-up Tokamak Energy, author of “Aurora: In Search of the Northern Lights” and is currently working on a book about Mount Everest.
Website: www.melaniewindridge.co.uk (see the Science & Exploration blog to read about the Everest climb)
Twitter @m_windridge, Facebook /DrMelanieWindridge, Instagram @m_windridge
Science of Everest videos on the Institute of Physics YouTube channel http://bit.ly/EverestVids

Image of the Week – The shape of (frozen sea) water

 

Figure 1: Annual evolution of the sea ice area with two different floe shape parameters of 0.44 (red) and 0.88 (blue). The model is spun-up between 2000 – 2006 and then evaluated for a further ten years between 2007 – 2016 and the mean values over this period displayed by the thick lines. Thin lines show the results for individual years. [Credit: Adam Bateson]

Polar sea ice exists as isolated units of ice that we describe as floes. These floes do not have a constant shape (see here for instance); they can vary from almost circular to being jagged and rectangular. However, sea ice models currently assume that all floes have the same shape. Much focus has been paid to the size of floes recently, but do we also need to reconsider how floe shape is treated in models?


Why might floe shape matter?

In recent years, sea ice models have started to examine more and more how individual floes influence the overall evolution of sea ice.

A particular focus has been the size of floes (see here and here) and the parameterisation of processes which influence floe size (see here for example). However less attention has been given to the shape of the floe. The shape of the floe is important for several reasons:

  • Lateral melt rate: the lateral melt rate describes how quickly a floe melts from its sides. Two floes with the same area but different shape can have a different perimeter; the lateral melt rate  is proportional to the floe perimeter.
  • Wave propagation: a straight floe edge will impact propagating waves differently to a curved or jagged floe edge. The distance waves travel under the sea ice and hence the extent of sea ice that waves can fragment will be dependent on these wave-floe edge interactions.
  • Floe mechanics: an elongated floe (i.e. much longer in one direction than another) will be more likely to break from incoming waves if its longer edge is aligned with the direction the waves are travelling.

How do models currently treat floe shape?

One approach used within sea ice models to define floe shape is the use is the use of a parameter, α. The smaller the floe shape parameter, the longer the floe perimeter (and hence, the higher the lateral melt rate). A standard value used for the parameter is 0.66 (Steele, 1992). Figure 2 shows how this floe shape parameter varies for some common shapes.

Figure 2: The floe shape parameters for some common shapes are given for comparison to the standard value of 0.66. [Credit: Adam Bateson]

The standard value of the floe shape parameter, 0.66, was obtained from taking the mean floe shape parameter measured over all floes greater than 1 km from a singular study area of 110 km x 95 km at one snapshot in time. Despite the limited data set used to estimate this shape parameter, it is being used for all sea ice throughout the year for all floe sizes. However, this would only be a concern to the accuracy of modelling if it turns out that sea ice evolution in models is sensitive to the floe shape parameter.

 

Model sensitivity to floe shape

To investigate the model sensitivity to the floe shape parameter two simulations have been run: one uses a floe shape parameter of 0.88 and the other uses 0.44, chosen to represent likely extremes. The two simulations are run from 2000 – 2016, with 2000 – 2006 used as a spin-up period. Figure 1 displays the mean total ice area throughout the year and results of individual years for each simulation. Figure 3 is an equivalent plot to show the annual evolution of total ice volume for each simulation.

The results show that the perturbation from reducing the floe shape parameter is smaller than the variation between years within the same simulation.  However, the model does show a permanent reduction in volume throughout the year and a 10 – 20 % reduction in the September sea ice minimum. The impact of the floe shape is hence small but significant, particularly for predicting the annual minimum sea ice extent and volume.

Figure 3: Annual evolution of the sea ice volume with two different floe shape parameters of 0.44 (red) and 0.88 (blue). The model is spun-up between 2000 – 2006 and then evaluated for a further ten years between 2007 – 2016 and the mean values over this period displayed by the thick lines. Thin lines show the results for individual years.

More recent studies on floe shape

In 2015, Gherardi and Lagomarsino analysed the floe shape behaviour from four separate samples of satellite imagery from both the Arctic and Antarctic. The study found different distributions of floe shapes in different locations, however there was no correlation between floe shape and size. This property would allow models to treat floe shape and size as independent properties. More recently, in 2018, Herman et al. analysed the results of laboratory experiments of ice breaking by waves. It was found that wave break-up influenced the shape of the floes, tending to produce straight edges and sharp angles.  These features are associated with a smaller floe parameter i.e. would produce an increased lateral melt rate.

What next?

More observations are needed to identify whether the use of a constant floe shape parameter is justified. The following questions are important:

  • Do further observations support the finding that floe size and shape are uncorrelated?
  • What range of values for the floe shape parameter can be observed in reality?
  • Do we see significant variations in the floe shape parameter between locations?
  • Do these variations occur over a large enough scale that they can be represented within existing model resolutions?

Further reading

Edited by Violaine Coulon and Sophie Berger


Adam Bateson is a PhD student at the University of Reading (United Kingdom), working with Danny Feltham. His project involves investigating the fragmentation and melting of the Arctic seasonal sea-ice cover, specifically improving the representation of relevant processes within sea-ice models. In particular he is looking at lateral melting and wave induced fragmentation of sea-ice as drivers of break up, as well as the role of the ocean mixed layer as either an amplifier or dampener to the impacts of particular processes. Contact: a.w.bateson@pgr.reading.ac.uk or @a_w_bateson on twitter.

Image of the Week – Stuck in the ice: could it have been predicted?

Image of the Week –  Stuck in the ice: could it have been predicted?

Expeditions in the Southern Ocean are invaluable opportunities to learn more about this fascinating but remote region of the world. However, sending vessels to navigate the hostile Antarctic waters is an expensive endeavor, not only financially but also from a human perspective. When vessels are forced to turn back due to hazardous conditions or, even worse, become stuck in the ice (as shown in our Image of the Week), a mission full of expectations can quickly turn into a nightmare. Hence there is an increasing demand for reliable information on the navigability of the Southern Ocean a few weeks to a few months in advance. This information could support the final decision whether to start the journey or not, and would allow minimizing the associated risks.


What’s the problem?

In late February 2018, the British vessel RRS James Clark Ross was heading to the Eastern Antarctic Peninsula to investigate the consequences of the calving of a massive iceberg from the Larsen C ice shelf. Unfortunately the vessel had to turn back before reaching its goal due to the unexpected presence of thick sea ice in the region. This story is not unusual. During Christmas 2013, a Russian ship named the Akademik Shokalskiy also got stuck in several meters of Antarctic sea ice. Ironically, one of the rescuing vessels itself (the Chinese Xuě Lóng) got trapped in the ice as well. To prevent such events from happening again, we need to be able to predict the upcoming sea-ice conditions. Can sea-ice conditions be forecast at seasonal time scales? If so, how?

 

Antarctic sea ice, the Year of Polar Prediction and SIPN South

To prevent accidents and unforeseen problems, one goal of the Year Of Polar Prediction is to enhance environmental forecasting capabilities from operational (hours to days) to tactical (weeks to months) time scales in high latitude regions. Several studies support the notion that Antarctic sea ice may be predictable a few months ahead, at least in certain regions (Holland et al. 2017, Chen and Yuan 2004, Holland et al. 2013, Marchi et al. 2018).

To investigate further the predictability of Antarctic sea ice, the Sea Ice Prediction Network South (SIPN South) was launched in 2017. It is a two-year international project endorsed by the YOPP. SIPN South pursues three strategic objectives:

  • Hosting seasonal outlooks of Antarctic sea ice to better understand the sources of sea-ice predictability and the origins of systematic forecast errors in different types of models.
  • Providing news and information on the current state of Antarctic sea ice, disseminating research to a wider audience and reporting ongoing field campaigns.
  • Coordinating realistic seasonal prediction exercises to investigate the potential use of this information for users and customers, primarily ships navigating in the region.

 

February 2018 seasonal sea-ice forecasts

As a first major milestone, SIPN South provided coordinated forecasts of sea ice for February 2018. February is the month with the smallest sea-ice area in the Antarctic, and therefore most of the shipping traffic in the region happens around that time. Participants were asked to provide an estimation of sea-ice coverage (area, concentration) for each day of February 2018, and were asked to issue their predictions by mid-December 2017. 13 research groups participated in this first forecasting experiment, following different approaches: several groups used fully coupled climate dynamical models, while others applied statistical regression methods to predict future ice conditions.

As we all know, the weather is unpredictable beyond a few days. However, previous research has suggested that the statistics of weather (its mean, its variability) can potentially be predicted from months to decades, due to the coupling of the atmosphere with “slower” components of the climate system like the ocean. To reflect this and to accurately estimate the statistics of weather, groups tend to provide not just one forecast, but several of them. These “ensembles” of forecasts provided by each group therefore represent all possible states of the atmosphere, ocean and ice that may prevail in February 2018 – given the known initial conditions of December.

The results of the coordinated experiment are shown in Figure 2. The February mean sea-ice area is shown for each group (colors), along with two actual observational references (black). Bear in mind that the forecast data were issued two months before the actual target date! Here, the forecasts are expressed as anomalies with respect to a reference climatology. All forecasts tend to overestimate the February sea ice area in the Ross Sea. A reason for this wrong estimation might be a very unusual cyclone, which passed over the Ross Sea around the 20th of January 2018 (i.e., between the time the forecasts were issued and the period for verification). This cyclone brought relatively warm air into the region. Furthermore it fractured the ice, opening more areas of open water and possibly increasing the effect of the ice-albedo feedback. Events like this one are not individually predictable several weeks in advance, but a well-designed forecasting system should at least account for this possibility. Despite running ensembles of forecasts, the sea-ice reduction in the Ross Sea was not captured by most forecasts. This may point towards a common and systematic deficiency in these prediction systems.

Figure 2: February 2018 mean regional sea-ice area anomaly (compared to 1979-2014 observed climatology) by longitude, for the 13 submissions, with observed estimates given in black. Solid lines show the ensemble mean for each contribution, with transparent shading indicating the ensemble range (min-max) [Credit: F. Massonnet].

Communicating climate information

Sea-ice area, as shown in Fig. 2, is a primary parameter used by scientists to quantify ice presence in a given region. It is also a useful number to diagnose model-data mismatch. However, sea-ice area is of little use for those who actually need climate information. For someone operating a vessel, the important information is how likely that vessel is to encounter sea ice in a given region for a given day in February. Information from Fig. 2, while certainly useful to scientists, is meaningless to those willing to extract practical information for navigation.

Alongside the work to understand fundamental drivers of sea-ice predictability in order to eventually improve the predictions, it is necessary to consider how potential users will interact with the forecasts. As explained above, climate forecasts are probabilistic in nature. Communicating probabilistic information to a non-trained audience is always a challenging task: for example, how would you interpret a forecast saying that there is a 50% chance of rain for tomorrow?

To reflect the irreducible uncertainty of climate forecasts (see previous section), sea-ice forecasts are generally expressed in terms of sea-ice probability, i.e. the probability that a given region of the Southern Ocean has sea-ice concentration larger than 15%. This probability is derived for each day and each grid cell from the ensemble forecasts contributed by each group (Fig. 3). If well calibrated, this type of information can be useful to those planning operations weeks in advance. For example, all but one model had forecast a high (>80%) probability of ice presence in the Larsen C area (eastern tip of the Antarctic Peninsula) where the RRS James Clark Ross got stuck five months ago. That is, there was a high risk, according to those forecasts, that ice would be present in that area in February. Of course, this does not mean that navigation would have been impossible (ice breakers can still operate in icy waters, provided the ice is thin), but these forecasts provided a first-order warning that there was a significant risk of encountering hazardous ice conditions there.

Figure 3: Probability of sea-ice presence for 15th February 2018, as forecasted by the five groups that submitted daily sea-ice concentration information. The sea-ice edge as observed by two products is shown in white. The probability of presence for a given day corresponds to the fraction of ensemble members that simulate sea-ice concentration larger than 15% in a given grid cell for that day. A dynamic animation of the figure showing all 28 days of February is available on the SIPN South website. [Credit: F. Massonnet]

Forecasting February 2019

The core phase of the Year of Polar Prediction entails “Special Observing Periods”, that is, intensive efforts to monitor the Arctic and Antarctic regions but also to enhance modeling activities (see this previous post). The (unique) Special Observing Period in the Southern Ocean will take place between mid-November 2018 and mid-February 2019. A new call for contributions will be launched by SIPN South to collect sea-ice forecasts for austral summer 2019, hoping that the first exercise in 2018 will raise the interest of even more research groups. A key question will be to assess whether the systems will be able to forecast better the sea-ice conditions in the challenging Ross Sea area, where most forecasts failed. Better insights will hopefully be gained in tracing the origin of systematic model error and lead to an improvement of Antarctic sea ice predictions within the next decade. As reliable climate information is crucially needed in this remote but important region of the world, future efforts to predict Antarctic sea ice will be very welcome!

 

Further reading

Edited by Adam Bateson and Clara Burgard

 


François Massonnet is a F.R.S.-FNRS Post-Doctoral Researcher at the Université catholique de Louvain and scientific collaborator at the Barcelona Supercomputing Center (Spain). He is assessing climate models as tools to understand (retrospectively and prospectively) polar climate variability and beyond. He tweets as @FMassonnet. Contact Email: francois.massonnet@uclouvain.be