Photo Friday: The 2020 Greenland Melt Season is Underway

Daily updates have resumed for the 2020 Greenland melt season, the National Snow and Ice Data Center (NSIDC), based in Boulder, Colorado, announced last month. The open-access information is available for those interested on the NSIDC website for the April through October melt season. The Greenland Ice Sheet Today data collection contains daily, monthly, and annual melt areas for the Greenland Ice Sheet. The data is displayed as an interactive chart where users can select years to compare back to 1979.

Source: National Snow and Ice Data Center

The green plot line below represents the 2019 melt year. According to the NSIDC, melting on the Greenland ice sheet for 2019 was the seventh-highest since 1978, behind 2012, 2010, 2016, 2002, 2007, and 2011.

Source: National Snow and Ice Data Center

The Greenland ice sheet data is derived from passive microwave sensors, which project data onto a 25-kilometer equal-area grid. Ice monitoring gained a powerful new tool with the launch of ICESat-2 in the fall of 2018. The orbiter uses a laser altimeter to produce imagery with astounding resolution. According to NASA, “With 10,000 laser pulses per second, this fast-shooting laser technology allows ATLAS to take measurements every 28 inches along the satellite’s path.”

Read More on GlacierHub:

A Personal Reflection on a Himalayan COVID Experience in Queens

Video of the Week: Quechua Artist Raps in Mountain Landscape

Q & A with Artist Activist Diane Burko

Thwaites Glacier in Antarctica is Now Causing Earthquakes

Thwaites Glacier is one of Antarctica’s largest contributors to sea level rise from Antarctica.  Its rate of loss has doubled in the past three decades, earning it the moniker “doomsday glacier.” Understanding why it’s retreating so quickly has been a challenge, but glaciologists have recently discovered that the glacier is now generating its own seismic activity when it calves (breaks off icebergs into the ocean), which could help in unlocking the physical keys to this process. The findings were published early this year in Geophysical Research Letters.  

Combing through seismograph readings collected in West Antarctica during a large calving event at Thwaites on February 8th 2014, a team of researchers found evidence of two low frequency earthquakes, each about 10-30 seconds long. Their hunch—that the quakes came from the calving—was confirmed when they matched the seismograph readings with satellite images taken on the same day. 

Thwaites Glacier
The rate of ice loss from Thwaites Glacier has doubled in the last thirty years. (Source: NASA)

They also discovered high frequency blips of seismic activity that chirped on and off in the week preceding the event. Glaciologist and lead author of the study, Paul Winberry, explained to GlacierHub that in these short bursts they were actually “hearing all these little cracks start to propagate.” It was the sound of countless cracks forming and popping apart, heralding the large break about to come. 

“Frequency” refers to the behavior of shockwaves that reverberate out from the source of the earthquake. Waves repeat their motion as they travel in a peak-valley-peak-valley pattern. Waves that do this rapidly are called high-frequency and those that do it slowly are called low frequency. High frequency waves are detectable over short distances; low frequency waves over long distances.       

Thwaites is the only known glacier in Antarctica to exhibit seismic behavior, whereas glaciers in Greenland have been recorded causing earthquakes for some time. This difference can be explained by the fact that the majority of Greenland’s icebergs capsize when they break off into the water. The result is a more boisterous form of calving that produces detectable earthquakes. Why Greenland’s icebergs capsize and Antarctica’s do not has to do with the physical makeup of each landmass’s ice sheets and where they start to float on the water.

Greenland glaciers flow down the island’s mountainous sides and break into icebergs when they hit the water. This behavior is common where a glacier’s terminus is close to where it starts to float—also known as the grounding line. Antarctic glaciers flow outwards horizontally, and continue on into the water as huge floating shelves that stretch miles out to sea. 

“Basically when [Greenland glaciers] start to go afloat, they form icebergs as opposed to Antarctica, where in most places they go afloat they don’t break off instantaneously but they form these big long ice shelves—floating extensions,” said Winberry. “It’s completely different.”

The other key component of capsizing is the physical shape. Greenland’s icebergs are top-heavy. “They’re taller than they are wide. They’re not stable, so when they break off they want to flip over,” said Winberry. 

Tim Bartholomaus, a glaciologist from the University of Idaho who has studied Greenland’s glaciers told GlacierHub that the capsizing icebergs bang into the front of the glacier as they’re flipping over and that generates the earthquake. “As they’re rotating en masse, they’re putting their shoulder against the back of the terminus and giving it an enormous push as they’re rotating.” 

Icebergs near the terminus of Thwaites Glacier. If it were to collapse it could raise global sea levels by ten feet. (Source: NASA)

These collisions don’t normally occur during calving in Antarctica because the ice sheets are far bigger, already floating on the water, and terminate far from the grounding line. “Those icebergs break off and form New England or Delaware-sized chunks. And when that happens they kind of slowly drift away,” said Winberry. That Thwaites is now generating detectable seismic earthquakes means one thing: its icebergs are likely capsizing because its terminus is now close to the grounding line. 

“The fact that Thwaites is now doing this slab capsize style of calving, that means that it is breaking off right at the point where the glacier is hitting the ocean,” said Bartholomaus. 

The capsize calving at Thwaites on February 8th 2014 sent low frequency waves traveling—and shaking—through the ice and land underneath for hundreds of miles. It generated enough energy to show up on seismometers over 900 miles away as a magnitude 3.0 earthquake.  

Over the last three decades, the Thwaites glacier has lost about 600 billion tons of ice. Some scientists fear that with an increased rate of 50 billion tons of ice lost a year in recent times, runaway instability of the glacier may already be underway. Total collapse of the glacier would raise global sea levels by 10 feet. Thwaites’ newfound seismic activity suggests that its retreat has now reached land. 

“It’s lost all of its floating ice,” Winberry told GlacierHub. “The floating extension has basically disappeared. So to understand the future retreat of the glacier, we need to understand this different style of calving behavior.” 

While that may be concerning, it also gives scientists a new tool for better understanding the process of calving at Thwaites. So far, glaciologists have relied heavily on satellite imagery for studying large scale calving events in Antarctica, but satellites usually only take one picture a day or every two days.  “A lot happens between those two days. In these calving events, the flipping of these icebergs and actual breaking apart can happen over minutes to hours,” said Winberry. Being able to “listen” to them unfold in near real time adds a whole new element. 

“That is going to help us unravel the physics of how these icebergs actually form, which is what we need to know to produce better predictions of future retreat of this glacier” said Winberry. 

Read More on GlacierHub:

Video of the Week: Animation Shows Frequency of Antarctic Calving Events

A Catastrophic Glacier Collapse and Mudflow in Salkantay, Peru

Roundup: A New Glacier Surge Study, Three Decades of Caucasus Glacier-Debris Change, and Mining Expansion in Greenland

Roundup: Pre-Columbian Land Use, Trump in Tongass, and Greenland’s Ice Sheet

The Inca’s sustainable land use practices

From Quaternary Science Reviews:

“The extent of pre-Columbian land use and its legacy on modern ecosystems, plant associations, and species distributions of the Americas is still hotly debated. To address this gap, we present a Holocene palynological record (pollen, spores, microscopic charcoal, SCP analyses) from Illimani glacier with exceptional temporal resolution and chronological control close to the center of Inca activities around Lake Titicaca in Bolivia. Our results suggest that Holocene fire activity was largely climate-driven and pre-Columbian agropastoral and agroforestry practices had moderate (large-scale) impacts on plant communities. Unprecedented human-shaped vegetation emerged after AD 1740 following the establishment of novel colonial land use practices and was reinforced in the modern era after AD 1950 with intensified coal consumption and industrial plantations of Pinus and Eucalyptus. Although agroforestry practices date back to the Incas, the recent vast afforestation with exotic monocultures together with rapid climate warming and associated fire regime changes may provoke unprecedented and possibly irreversible ecological and environmental alterations.”

Read the article here.

Lake Titicaca (Source: Wikimedia Commons)

Trump proposes logging nearby Alaskan glaciers

From the Washington Post:

“Politicians have tussled for years over the fate of the Tongass, a massive stretch of southeastern Alaska replete with old-growth spruce, hemlock and cedar, rivers running with salmon, and dramatic fjords. President Bill Clinton put more than half of it off limits to logging just days before leaving office in 2001, when he barred the construction of roads in 58.5 million acres of undeveloped national forest across the country. President George W. Bush sought to reverse that policy, holding a handful of timber sales in the Tongass before a federal judge reinstated the Clinton rule.

Read the article here.

A view of Mendenhall Glacier, which lies in Tongass National Forest (Source: Wikimedia Commons)

Greenland ice sheet mass balance

From GEUS Bulletin:

“The Programme for Monitoring of the Greenland Ice Sheet (PROMICE) has measured ice-sheet elevation and thickness via repeat airborne surveys circumscribing the ice sheet at an average elevation of 1708 ± 5 m (Sørensen et al. 2018). We refer to this 5415 km survey as the ‘PROMICE perimeter’ (Fig. 1). Here, we assess ice-sheet mass balance following the input-output approach of Andersen et al. (2015). We estimate ice-sheet output, or the ice discharge across the ice-sheet grounding line, by applying downstream corrections to the ice flux across the PROMICE perimeter.”

Read the article here.

A helicopter takes off from the Greenland Ice Sheet. (Source: Wikimedia Commons)

Read More on GlacierHub:

What the 2018 State of the Climate Report Says About Alpine Glaciers

The Funeral for Iceland’s OK Glacier Attracts International Attention

Park Officials Remove Signs Warning That Some Glaciers Will Disappear by 2020

Roundup: Pollen in Ice Cores, Melting in Greenland, and Water Usage in Switzerland

Pollen found in ice cores

From Arctic, Antarctic, and Alpine Research: “Pollen grains are commonly found in ice cores, particularly those from mountain glaciers at low to middle latitudes … We analyzed major pollen grains in an 87-m-deep ice core drilled at the top of the Grigoriev Ice Cap (4563 m.a.s.l.) in the Tien Shan Mountains, Kyrgyz Republic. Microscopy showed that mainly five pollen taxa were contained in the ice core.”

Read the full research article here.

Tien Shan Mountains (Source: Piotr Gaborek, Flickr)

Glacial meltwater’s influence on biogeochemical cycles in greenland

From Frontiers in Marine Science: “Greenland fjords receive considerable amounts of glacial meltwater discharge from the Greenland Ice Sheet due to present climate warming. This impacts the hydrography, via freshening of the fjord waters, and biological processes due to altered nutrient input and the addition of silts … Our results imply that glacially influenced parts of Greenland’s fjords can be considered as hotspots of carbon export to depth. In a warming climate, this export is likely to be enhanced during glacial melting.”

Read the full research article here.

Meltwater on the Greenland ice sheet (Source: YangTS, Flickr)

Water usage in Oberhasli, Switzerland

From Environmental Science and Policy: “Incoherent institutional regimes are among the most critical barriers to adapt water governance under climate change. However, it remains unclear how different governance processes can coordinate competing resource uses despite incoherence of institutional resource regimes. This paper examines how institutional resource regimes and polycentric governance processes are co-evolving and to what extent these processes coordinate competing resource uses in incoherent resource regimes. ”

Read more about the research here.

Oberhasli, Switzerland (Source: Rolf & Beate, Flickr)

Read More on GlacierHub:

Photo Friday: The Power of Stories by the Global Oneness Project

Kathmandu Event Highlights Deepening Interest in Hindu Kush Himalaya Region

Video of the Week: An Animated History of Glaciers

Roundup: Contaminated Arctic Spiders, Sand Abundance in Greenland, and Cryoconite on the Tibetan Plateau

Wolf spiders in West Greenland are indicators of metal pollution in mine sites

From Ecological Indicators: “In the Arctic, spiders are the most abundant group of terrestrial predators, with documented abilities to accumulate metals. In Greenland however, most contamination studies in relation to mining have targeted the marine environment, with less attention given to the terrestrial.”

“The contamination status of a terrestrial area can be estimated based on soil sampling and measurements. However, such measurements may be biased due to difficulties in collecting representative soil samples (i.e. caused by high within-site variation of soil contaminants or a lack of information on potential bioavailability of the contaminants investigated). It has therefore been hypothesized that ground dwelling wolf spiders, based on their frequent hunting activities and their active movement over their hunting habitat, would display contamination levels more representative of that area than a specific soil sample.”

Read more about the study here.

Wolf spider in the tundra (Source: Fiona Paton/Flickr)

Greenland’s melting ice sheet releases vast quantities of sand

From Henry Fountain and Ben C. Solomon of the New York Times: “The world makes a lot of concrete, more than 10 billion tons a year, and is poised to make much more for a population that is forecast to grow by more than 25 percent by 2050. That makes sand, which is about 40 percent of concrete by weight, one of the most-used commodities in the world, and one that is becoming harder to come by in some regions.”

“But because of the erosive power of ice, there is a lot of sand in Greenland. And with climate change accelerating the melting of Greenland’s mile-thick ice sheet — a recent study found that melting has increased sixfold since the 1980s — there is going to be a lot more.”

Read the full story here.

Cryoconite on the northeastern Tibetan Plateau enhances melting

From Journal of Glaciology: “Cryoconite is a dark-coloured granular sediment found in supraglacial environments, and it represents an aggregate of mineral particles, black carbon (BC) and organic matter (OM) formed by microbial communities.”

“Compared with snow and ice surfaces, cryoconite typically exhibits stronger light absorption, and its broadband albedo is <0.1 due to its effective absorption of visible and near-IR wavelengths. Thus, cryoconite can effectively influence the mass balance of glacier surfaces.”

Read more about the research here.

Debris and cryoconite at A8 glacier study site (Source: Li et al. 2019)

Roundup: Tibet’s Cryosphere, Methane Release, and Rockfall-induced GLOFs

The Tibetan Plateau’s Changing Cryosphere

From Earth-Science Reviews: “This paper comprehensively reviews the current status and recent changes of the cryosphere (e.g., glacier, snow cover, and frozen ground) in the TP from the perspectives of observations and simulations. Because of enhanced climate warming in the TP, a large portion of glaciers have experienced significant retreat since the 1960s, with obvious regional differences. The retreat is the smallest in the TP interior, and gradually increases towards the edges.”

Check out the full study here.

Tibetan Plateau mountains on GlacierHub
A view of the mountains from a green valley in the Tibetan Plateau (Source: Hans Johnson/Flickr).

 

Methane Release Under Greenland’s Ice Sheet

From Nature: “Here we find that subglacially produced methane is rapidly driven to the ice margin by the efficient drainage system of a subglacial catchment of the Greenland ice sheet…We show that subglacial hydrology is crucial for controlling methane fluxes from the ice sheet…Overall, our results indicate that ice sheets overlie extensive, biologically active methanogenic wetlands and that high rates of methane export to the atmosphere can occur via efficient subglacial drainage pathways. Our findings suggest that such environments have been previously underappreciated and should be considered in Earth’s methane budget.”

Check out the full study here.

Helheim Kangerdlugssuaq Greenland ice sheet on GlacierHub
NASA’s IceBridge flying over the Helheim/Kangerdlugssuaq region of Greenland’s ice sheet, documenting summertime melt (Source: NASA Goddard/Flickr).

 

Rockfall-induced GLOFs in Nepal

From Landslides: “On April 20, 2017, a flood from the Barun River, Makalu-Barun National Park, eastern Nepal formed a 2–3-km-long lake at its confluence with the Arun River as a result of blockage by debris. Although the lake drained spontaneously the next day, it caused nationwide concern and triggered emergency responses…This study highlights the importance of conducting integrated field studies of recent catastrophic events as soon as possible after they occur, in order to best understand the complexity of their triggering mechanisms, resultant impacts, and risk reduction management options.”

Check out the full study here.

Upper Barun Valley on GlacierHub
Upper Barun Valley, Nepal. The aftermath of the Langmale GLOF are shown on the lower left portion of the image (Source: Roger Nix/Flickr).

Roundup: Black Carbon, Dying Crustaceans, and Ice Sheet Melting

Kuwait Fires Cause Black Carbon Buildup

From Atmospheric Chemistry and Physics: “Muztagh Ata is located to the east of Pamir and in the north of the Tibetan Plateau. The ice core data provide important information for atmospheric circulation and climate change in Asia. Moreover, the climate in Muztagh Ata is very sensitive to solar warming mechanisms because it has a large snow cover in the region, resulting in important impacts on the hydrological cycle of the continent by enhancing glacier melt.”

Read more about black carbon in northern Tibet here.

Muztagh Ata Mountain, northern Tibetan Plateau (Source: Yunsheng Bai/Flickr)

 

Microscopic Crustaceans at Risk in Patagonian Fjords

From Progress in Oceanography: “Glacial retreat at high latitudes has increased significantly in recent decades associated with global warming. Along Chile’s Patagonian fjords, this has promoted increases in freshwater discharge, vertical stratification, and the input of organic and inorganic particles to fjords.”

Read more about the effects of glacial retreat on Patagonian crustaceans here.

Pia Fjord in Chile (Source: Glenn Seplak/Flickr).

 

Melting Greenland Ice Sheet Contributes to Sea Level Rise

From The Cryosphere: “Mass loss from the Greenland Ice Sheet (GrIS) has accelerated since the early 2000s, compared to the 1970s and 1980s, and could contribute 0.45–0.82m of sea level rise by the end of the 21st century. Recent mass loss has been attributed to both a negative surface mass balance and increased ice discharge from marine-terminating glaciers.”

Read more about the research here.

Massive ice island broken off from Petermann Glacier, one of the 18 glaciers observed in the study (Source: NASA Goddard Space Flight/Flickr).

 

Roundup: Remote Sensing, Arctic Civilizations, and Glacier Disaster

Greenland Iceberg Melt Variability

From Cryosphere Journal: “Iceberg discharge from the Greenland Ice Sheet accounts for up to half of the freshwater flux to surrounding fjords and ocean basins, yet the spatial distribution of iceberg meltwater fluxes is poorly understood. One of the primary limitations for mapping iceberg meltwater fluxes, and changes over time, is the dearth of iceberg submarine melt rate estimates. Using a remote sensing approach to estimate submarine melt rates during 2011–2016, we find that spatial variations in iceberg melt rates decrease with latitude and increase with iceberg draft. Overall, the results suggest that remotely sensed iceberg melt rates can be used to characterize spatial and temporal variations in oceanic forcing near often inaccessible marine-terminating glaciers.”

Discover more about the use of remote sensing for studying glacier melt rates here.

Aerial Image of Greenland Ice Sheet (Source: NOAA).

 

The History of Civilizations in the Arctic

From “Arctic Modernities: The Environmental, the Exotic and the Everyday“: “Less tangible than melting polar glaciers or the changing social conditions in northern societies, the modern Arctic represented in writings, visual images and films has to a large extent been neglected in scholarship and policy-making. However, the modern Arctic is a not only a natural environment dramatically impacted by human activities. It is also an incongruous amalgamation of exoticized indigenous tradition and a mundane every day. The chapters in this volume examine the modern Arctic from all these perspectives. They demonstrate to what extent the processes of modernization have changed the discursive signification of the Arctic. They also investigate the extent to which the traditions of heroic Arctic images – whether these traditions are affirmed, contested or repudiated – have continued to shape, influence and inform modern discourses.”

Read more about the history of the Arctic here.

Cover of Arctic Modernities Book (Source: Amazon).

The Catastrophic Eruption of Mount Kazbek

From Volcano Café: “What makes a volcano dangerous? Clearly, the severity of any eruption plays a role. So does the presence of people nearby. But it is not always the best-known volcanoes that are the most dangerous. Tseax is hardly world-renowned, but it caused a major volcanic disaster in Canada. And sometimes a volcano can be dangerous without actually erupting. Lake Nyos in Cameroon is a well-known -and feared- example. What happened in the eruption of Mount Kazbek that made it such a catastrophe?”

Explore the famous volcanic disaster that resulted from a glacier-melting event in 2002 here.

Mount Kazbek (Source: Volcano Cafe).

Roundup: Microbial Mats, Hidden Heat, and Tree Infection

Benthic Microbial Mats in Meltwater from Collins Glacier

From Polar Biology: “Most of Fildes Peninsula is ice-free during summer thereby allowing for formation of networks of creeks with meltwater from Collins Glacier and snowmelt. A variety of benthic microbial mats develop within these creeks. The composition of these microbial communities has not been studied in detail. In this report, clone libraries of bacterial and cyanobacterial 16S rRNA genes were used to describe the microbial community structure of four mats near a shoreline of Drake Passage. Samples were collected from four microbial mats, two at an early developmental stage (December) and two collected latter in late summer (April). Sequence analysis showed that filamentous Cyanobacteria, Alphaproteobacteria, and Betaproteobacteria were the most abundant ribotypes.”

Learn more about the microbial mats here.

Microbial mat on a sandy depositional surface (Source: GSA).

 

Geothermal Heat Flux Hidden Beneath Greenland Ice Sheet

From Nature: “The Greenland ice sheet (GIS) is losing mass at an increasing rate due to surface melt and flow acceleration in outlet glaciers… Recently it was suggested that there may be a hidden heat source beneath GIS caused by a higher than expected geothermal heat flux (GHF) from the Earth’s interior. Here we present the first direct measurements of GHF from beneath a deep fjord basin in Northeast Greenland. Temperature and salinity time series (2005–2015) in the deep stagnant basin water are used to quantify a GHF of 93 ± 21 mW m−2 which confirm previous indirect estimated values below GIS. A compilation of heat flux recordings from Greenland show the existence of geothermal heat sources beneath GIS and could explain high glacial ice speed areas such as the Northeast Greenland ice stream.”

Learn more about the hidden heat flux here.

Aerial Image of Greenland Ice Sheet (Source: NOAA).

 

Blister Infection on the Whitebark Pine in the Greater Yellowstone Ecosystem

From University of Wyoming National Park Service Research Center: “Whitebark pine is a keystone and foundation tree species in high elevation ecosystems of the Rocky Mountains. At alpine treelines along the eastern Rocky Mountain Front and in the Greater Yellowstone Ecosystem, whitebark pine often initiates tree islands through facilitation, thereby shaping vegetation pattern. This role will likely diminish if whitebark pine succumbs to white pine blister rust infection, climate change stress, and mountain pine beetle infestations. Here, we established baseline measurements of whitebark pine’s importance and blister infection rates at two alpine treelines in Grand Teton National Park.”

Read more about the blister infection on Whitebark pine here.

Whitebark pine on the Continental Divide of the the Greater Yellowstone Ecosystem, which includes Yellowstone and Grand Teton National Parks (Source: Taisie Design).

Photo Friday: Core Of Climate Science

Layer upon layer of snow, built up over thousands of years, ice cores are an archive of Earth’s past. Taken from ice sheets and glaciers, these cores are used for scientific discovery of the climate changes that Earth may have gone through.

This is the focus of Peggy Weil’s “88 cores,” a four-and-a-half hour video descent two miles through the Greenland Ice Sheet in one continuous pan that goes back more than 110,000 years. It aims to explore the intersections of polar ice, time and humanity. “88 cores” is being shown for the first time as the second part of The Climate Museum’s “In Human Time” exhibition from January 19 to February 11.

“The film is not a scientific document, but it is informed by science. Although much of the data gleaned from ice cores is invisible (analysis of gasses, ECM data) the ice itself is visually compelling. The work acknowledges the immensity and grandeur of the ice (and the human effort to understand it) as we contemplate its fragility,” states Weil.

Along with the video, still images of the ice cores will also be on display and accompanied by other artifacts and media that offers context on ice core science and the Arctic.

The exhibition is being presented in partnership with the Parsons School of Design’s Sheila Johnson Design Center at The Arnold and Sheila Aronson Galleries in New York on Fifth Avenue.

For more information on the exhibition and the Climate Museum, visit climatemuseum.org or inhumantime.org

For more information on Peggy Weil, visit pweilstudio.com.

Viewer observing the 88 cores film at 1 meter (Source: Peggy Weil and the US National Ice Core Lab, GISP2).

 

88 cores film test at -1855 meters (Source: Peggy Weil and the US National Ice Core Lab, GISP2).

 

Peggy Weil at the US National Ice Core Lab (Source: Peggy Weil and the US National Ice Core Lab, GISP2).

 

 

Ice core – 2129 meters below the surface (Source: Peggy Weil and the US National Ice Core Lab, GISP2).

 

Of Ice and Fish

Sea ice surrounds this terminal glacier of the Greenland Ice Sheet (Source: Lorenz Meire).

Greenland is a landscape dominated by ice. The Greenland Ice Sheet flows into terminal glaciers, which calve into icebergs, which in winter are locked in by sea ice. Ice shapes the entire food web, from ocean microbes to the fish that fuel 90 percent of Greenland’s GDP.

The relationship between glaciers and Greenlandic fisheries just became clearer with the publication of a recent paper in Global Change Biology. The study found that coastal productivity in Greenlandic fjords is determined by whether the glaciers that flow into the fjords terminate on land, or in the sea.

“Many people think that there aren’t so many things happening in the Arctic,” the paper’s lead author, Lorenz Meire, told GlacierHub. “But during the three of four months of real summer, glaciers melt really fast and the fjords are very dynamic,” he said.

Brash ice before a marine-terminating glacier shows evidence of calving (Source: Lorenz Meire).

Meire and his coauthors compared Young Sound, which receives meltwater only from land-terminating glaciers, and southwest Greenland’s Godthåbsfjord, which is fed by melt from three land-terminating and three marine-terminating glaciers. They found that both were shaped by the glacial inputs, which in summer freshen the surface water and create a stratified water column.

Despite these similarities, the researchers found that Godthåbsfjord was far more productive than Young Sound. In summer, a large “bloom” of phytoplankton grows in Godthåbsfjord, supporting a dynamic food web of krill, other zooplankton, small fish, and migrating animals like whales, seals and halibut. In Young Sound, a small bloom during spring occurs. The fjord is quite unproductive during summer, and the waters cannot support such a diversity of animals.

Bottom-feeding halibut are a mainstay of Greenland’s fishing industry (Source: NOAA).

This difference is due to the upwelling of cold, deep, nutrient-rich seawater that occurs in Godthåbsfjord. Melt enters the fjord underwater at the marine-terminating glaciers. Because it is less dense than the surrounding seawater, the freshwater rises buoyantly to the surface, bringing deep seawater up with it. This seawater delivers nutrients like nitrate, a limiting factor for growth in the ocean, to the phytoplankton who live near the water’s surface.

In contrast, there is no upwelling in Young Sound, and as a result the water is nutrient-poor and 12 times less productive than Godthåbsfjord. Walruses and eider ducks, the top predators in Young Sound, feed on shellfish that live on the bottom.

Greenland’s food web is shaped by glaciers even further. Without knowing which type of glaciers flow into a given fjord, one could guess based solely on the number of fishing boats in the area. Halibut fisherman seek the productive waters fueled by marine-terminating glaciers, but this choice comes with risk. “It’s amazing how the fisherman go fishing in regions that are quite dangerous to sail in, but they keep going because there is a lot of fish,” said Meire. Between changeable weather, cold water, dense icebergs, and sea ice in the winter, many hazards threaten the halibut fisherman, who generally work solo in small dinghies. “It’s much easier in land-terminating fjords because there are no icebergs to destroy your boat,” he added.

Greenlandic halibut fishing dinghies are small and open to the elements (Source: Lorenz Meire).

Even from land, it is clear which fjords are only supplied freshwater by land-terminating glaciers and which are home to marine-terminating glaciers. The fisheries are located close to population centers, and Greenland’s big cities are located next to marine-terminating glaciers, according to Meire. “Almost every spot in Greenland where people live or have lived in the past is close to a marine-terminating glacier. People are aware that these regions are very productive, they understand that the glacier is fueling something,” he said.

As global temperatures rise, more marine-terminating glaciers will melt into land-terminating glaciers (Source: Lorenz Meire).

The question, of course, is what will happen to ecosystems, fisheries and towns as climate change turns Greenland’s marine-terminating glaciers into land-terminating glaciers. “It’s scary to see how fast glaciers are retreating,” said Meire, such as in Godthåbsfjord, where the glaciers have moved back 5-8 km in the last five years. Currently, he added, people in Greenland tend to view global warming as a positive thing, which will make winters easier and provide opportunities for more agriculture. Because the impacts for fisheries are so far in the future, the industry has not yet started to act to mitigate the eventual changes.

“For us, climate change is just a fact,” he said. “Everyone accepts what’s happening. We can make people aware that it will have large consequences on our ecosystem and try to stimulate people to take actions against it.”

 

Life, Death and Predation on the Greenland Ice Sheet

The Greenland Ice Sheet is the world’s second-largest body of ice (Source: Krzysztof Zawierucha).
Mention the Greenland Ice Sheet, and chances are that you conjure up the image of a barren, white wilderness, dominated by ice and devoid of life. In fact, the ice sheet and its coastal outlet glaciers support thousands of small pools that teem with bacteria and animals. “A world of microbes exists in these tiny, frozen, cold pools on glaciers. There’s life, death, and predation happening,” marveled glaciologist Aurora Roth.

These little pools are called cryoconite holes, pockets in the surface of glaciers that are usually ovular or circular. Cryoconite holes can be quite small and shallow, or as wide as a meter and up to half as deep. “People first notice cryoconites because they look so odd, like honeycomb. The textures are visually striking,” says Roth. She added that they constitute such an extreme environment that scientists look to them to understand the evolution of simple life forms on Mars and other planetary bodies. A recent paper in Limnology by Krzysztof Zawierucha et al. analyzed cryoconite communities on the margin of the Greenland Ice Sheet and found that the distribution of microfauna at the edge of the sheet is random, without clear ecological determinants like water chemistry or nutrient availability.

Sediment lies at the bottom of cryoconite holes of various sizes (Source: Krzysztof Zawierucha).
Cryoconite holes (and their larger versions, puddles and lakes) are full of water, and contain debris deposited by wind, rockfall or water flow. Small debris particles can be bound together by cyanobacteria into granules, which eventually erode into mud. Both granules and mud foster communities of bacteria and animals that comprise the biotic hotspots of the ice sheet. Microorganisms are the top consumers in cryoconite food chains, a position impossible for them to occupy in most other ecosystems, where they are eaten by larger organisms. Such unusual dynamics make “this icy world more and more fascinating,” Zawierucha told GlacierHub. “Despite the fact that they are in microscopic size, they are apex consumers on the glacier surface, so they are like polar bears in the Arctic or wolves in forests,” he said.

Zawierucha conducted his fieldwork at the beginning of polar autumn and was struck by the changing colors of the tundra, the musk oxen and the impressiveness of the ice sheet, which together created a landscape that felt right out of a fairy tale. As he trekked through wind and rain to collect samples from cryoconite holes, puddles and lakes, he often felt as if he was in a science fiction movie about “icy worlds in other galaxies.”

Zawierucha poses against the dramatic landscape of the ice sheet during fieldwork (Source: Krzysztof Zawierucha).
Back in the lab, Zawierucha found rotifers and tardigrades swimming around in his samples, two hardy invertebrate groups that also live in freshwater, mosses, and for the tardigrade, extreme environments–tardigrades are the only animals that can survive outer space. The invertebrates were far more common in granules than mud. The paper suggests two reasons for this disparity: the mechanical flushing action of water that forms the mud and the food source the granules provide for the invertebrates. The samples boomed with other types of life, as well: they contained thirteen types of algae and cyanobacteria, plus different groups of heterotrophic bacteria.

The flushing process, and the way it affects the animals which it displaces, raises many questions for Zawierucha. How much wind or rain is required to remove the animals from the cryoconites? “How many of them are flushed to downstream ecosystems, and how many stay in the weathering crust on glaciers?” he wonders. And what happens once the animals are out of their holes? Zawierucha harbors what he calls a “small dream,” to find active animals in the subglacial zone (the hydraulic systems under a glacier). “If they are flushed to the icy wells, are they able to survive under ice?” he asks.

Tardigrades are found on all seven continents, in a range of extreme environments (Source: E. Schokraie et al./Wikimedia).
In the future, Zawierucha would like to continue to close what he calls the “huge knowledge gap” between the vast amount of research devoted to microbial ecology on glaciers and the dearth of information about animals. “Even if their distribution is random, they still may play an important ecological role in grazing on other organisms,” he believes.

Tardigrades, some species of which are black in color, may have an even bigger effect on glacial dynamics and global climate. Tiny though they are, populations of black tardigrades in cryoconite holes, which Zawierucha has found on alpine glaciers, can reduce albedo and increase melting of the glacier surface. This may constitute a positive feedback loop that hastens glacial melting, but more studies are required to prove this, Zawierucha says.

One positive feedback loop is clear. Higher temperatures increase the melting of glacier surfaces and spur microbial activity, which in turn speeds up the process of melting, according to Zawierucha. As the Greenland Ice Sheet continues to melt, the animals that call it home will be disturbed, though it is difficult to anticipate the end result. How tardigrades, especially species unique to glacial habitats, will respond to higher flushing rates and removal from glaciers is of particular interest. Perhaps the tardigrades will adapt, or perhaps they will go extinct, says Zawierucha.

Zawierucha prepares samples for transport off the ice sheet (Source: Krzysztof Zawierucha).
Faced with an uncertain future, glaciology projects that cross disciplines make Roth hopeful. “It’s a good example of what happens when you look at a system through an interdisciplinary lens,” she told GlacierHub. “When you bring in a biologist, you see the difference in the questions they ask and things they unearth.”

Now is the time for such interdisciplinary research: more studies of animals living on the Greenland Ice Sheet will help scientists understand how this important freshwater reservoir, and Earth’s climate, will respond to global warming.