From Marine Mammal Science: “Harbor seals, Phoca vitulina, use diverse haul-out substrates including ice calved by tidewater glaciers. Numbers of seals at glacial and terrestrial haul-outs on the southeastern Kenai Peninsula, Alaska, were assessed using aerial, vessel, and video surveys. Mean annual abundance at glacial and terrestrial haul-outs differed temporally. From 2004 to 2011, numbers of seals counted during the molt increased 5.4%/yr at glacial haul-outs and 9%/yr at terrestrial haul-outs while numbers of pups increased 5.0%/yr at glacial sites and 1.5%/yr at terrestrial sites.”
Learn more about how harbor seals use glacial habitats here.
River Invertebrate Biodiversity
From Nature Ecology & Evolution: “Global change threatens invertebrate biodiversity and its central role in numerous ecosystem functions and services. Functional trait analyses have been advocated to uncover global mechanisms behind biodiversity responses to environmental change, but the application of this approach for invertebrates is underdeveloped relative to other organism groups. From an evaluation of 363 records comprising >1.23 million invertebrates collected from rivers across nine biogeographic regions on three continents, consistent responses of community trait composition and diversity to replicated gradients of reduced glacier cover are demonstrated.”
Read more about the response of river invertebrates to decreasing glacier cover here.
Greenland’s Freshwater Budget
From Nature Geoscience: “Liquid freshwater fluxes from the Greenland ice sheet affect ocean water properties and circulation on local, regional and basin-wide scales, with associated biosphere effects. The exact impact, however, depends on the volume, timing, and location of freshwater releases, which are poorly known. In particular, the transformation of icebergs, which make up roughly 30–50% of the loss of the ice-sheet mass to liquid freshwater, is not well understood. Here we estimate the spatial and temporal distribution of the freshwater flux for the Helheim–Sermilik glacier–fjord system in southeast Greenland using an iceberg-melt model that resolves the subsurface iceberg melt. By estimating seasonal variations in all the freshwater sources, we confirm quantitatively that iceberg melt is the largest annual freshwater source in this system type.”
Discover more about the freshwater flux of iceberg melt from Greenland’s ice sheet here.
Beneath the glaciers of the West Antarctic Peninsula lie island-like habitats teeming with species from spiny icefish and sea squirts (like Cnemidocarpa verrucosa) to various species of starfish. According to a recent paper in Marine Ecology Progress Series, these unique habitats are formed around glacial dropstones, rocks once incorporated into glaciers. Dropstones move across the surface of Antarctica and are carried out to sea by icebergs that have calved off glaciers. As the icebergs melt, they drop these stones, which settle on the ocean floor. The fallen rocks provide a hard surface for sessile, or non-moving, species to securely attach, creating small communities surrounded by mud.
Many of the animals living on the dropstones reproduce by spawning into the water. The resulting larvae then drift with the ocean currents until they encounter suitable surfaces, like a dropstone, to settle and grow into adults. The dropstones provide a habitat, distinctly different from the surrounding seafloor, for those sessile creatures. They also attract mobile species who come to the dropstones for food and nesting sites. The researchers often saw spiny icefish, or Chaenodraco wilsoni, guarding eggs on a dropstone.
Amanda Ziegler, the lead author of the paper and a graduate student at the University of Hawai’i at Mānoa, told GlacierHub that this is the first known study of dropstone communities near the West Antarctic Peninsula. “Glacial dropstones have been studied in other habitats such as in the Arctic and in the Weddell Sea [to the east of the Antarctica Peninsula] where the heterogeneity produced by the stones was also found to increase the functional and taxonomic diversity of the megafaunal communities where dropstones were abundant,” she said. So these results are not unexpected but do provide new insight into the area, confirming that such communities are found in a wider range of areas than previously known.
The waters around Antarctica are too deep for divers, so Ziegler and her team relied on photographs taken by underwater cameras towed by United States Antarctic Program research vessels from 2008 to 2010 during the LARISSA Project. The photos came from three fjords along the West Antarctic Peninsula, all greater than 400 meters deep as well as similarly deep areas along the open continental shelf. In all, the team measured 2,972 dropstones and found that 467 were colonized by at least one megafaunal species. The researchers also found that while glacial dropstones make up less than one percent of the seafloor habitat, they are home to 20 percent of the species in the area. Ziegler noted that the team examined the relative importance of different environmental parameters in structuring the communities. “We asked, for example, does water temperature, sediment cover, or the size and abundance of dropstones affect the community composition and does this differ by site?” she said.
Interestingly, not all dropstones examined were homes to communities of animals. To the researchers’ surprise, many were simply bare. Near Antarctica, shallow hard-substrate is often scarce, and therefore the communities that arise can be extremely dense and diverse. Ziegler expected the organisms to be space-limited, meaning the number of individuals and species is capped by the available habitat. Instead, they found many uninhabited, seemingly useable dropstones. The researchers possibly attribute this to a limited supply of larvae; there might not have been as high a density of sessile species that prefer hard substrate as expected. Ziegler also hypothesized that many of the bare dropstones could have been only recently deposited from icebergs.
In addition to being objects of ecological research, dropstones can also indicate glacial and iceberg activity. Dropstones only occur where icebergs, calved from glaciers, have passed, so the distribution of dropstones can help paint a picture of their distribution and movement. During this study, the researchers were expecting a more predictable distribution of the dropstones originating from the glaciers in the area, but Ziegler said she was surprised by the abundance and size of the dropstones deposited out on the open shelf further than 100 km from the nearest active glacier. “This means that icebergs in this region move around a lot more than we expected, and we know now from our current studies in Andvord Bay that there is less melting of the icebergs and glaciers inside the fjords than expected,” she added.
It is unclear how climate change and the related change in glacial processes will affect the future of these island-like communities. Each new iceberg has the potential to carry more rocks out to sea, where they can be deposited as dropstones, but as the researchers found, there are already many unoccupied dropstones in the area. Along with glacial melt under increased warming, sediment released into the fjords might increase, quickly covering the dropstones and making them unsuitable for many sessile invertebrates.
According to Ziegler, sessile organisms, especially those that filter food from the water column, are particularly sensitive to fine-grain sediments released by melting glaciers. A new study by co-author Craig Smith hopes to better understand biological, chemical and physical oceanography of Andvord Bay, one of the fjords in this study, to better assess future changes in this ecosystem. Through this and similar research, we will learn if and how climate change will threaten these underwater communities.
If you’re waiting patiently to hear the “prancing and pawing of each little hoof,” why not take some time to learn a bit about the reindeer (and caribou) that pull the sleigh. In this week’s Photo Friday, let’s take a trip to the glaciers, mountains and tundras that Donner and Blitzen call home.
First things first, the animals commonly called reindeer in Europe and caribou in North America are the same species, Rangifer tarandus. This species has been around for about a half million years, since the Pleistocene and lives all across the circumpolar north.
Reindeer have been domesticated in Europe for thousands of years primarily for their hide and meat, but they’ve also been trained to pull sleighs, and not just for Santa.
Caribou are particularly well adapted to the cold northern environments, with an incredibly dense coat. Their entire bodies, except the tip of their nose, are covered in a thick wooly underfur and a hollow gaurdhair that keeps them nice and cozy when not delivering presents.
And I’ll leave you with this BBC Earth video on reindeer migrations.
Asia will likely lose at least one-third of its glaciers by the end of this century, according to a recent study published in Nature. The ambitious target of keeping global average temperatures from increasing more than 1.5 degrees Celsius (or 2.7 degrees Fahrenheit) above pre-industrial levels set by the Paris Climate Accords won’t even be enough to curtail this fate, with rising temperatures having an outsized effect on glaciers in the high mountains of Asia.
“Our work shows that a global temperature rise of 1.5 degrees actually means a temperature increase of 2.1 degrees on average for the glacierized area in Asia,” Philip Kraaijenbrink, the lead author on the paper told GlacierHub. “We show that even if the world meets this extreme ambitious target, thirty-six percent of the ice volume will be lost by 2100.”
The goal of 1.5 degrees is generally regarded as extremely ambitious, and Kraaijenbrink and his team found that under more realistic scenarios, ice loss will be between 49 and 64 percent. Meltwater from those glaciers supply water to 800 million people. A loss of even one-third of the glaciers in the region has the potential for serious consequences for water management, food security, and energy production. Kraaijenbrink’s study stops short of investigating the actual impact this loss may have on people, and it is difficult to predict exactly what the future will hold for communities downstream of these glaciers.
Anna Sinisalo, a glaciologist with ICIMOD, who was not associated with the study, told GlacierHub, “There is also a need to reconstruct historical variability of climate to better understand the ongoing change, as without knowing the past we cannot make reliable predictions about the future.” However, this research is still a necessary step to understand how increasing temperatures will affect the region.
In addition to showing that a warming world will lead to losses of glaciers, the researchers also found large differences in how glaciers in the region would respond to climate change. Much of this is due to the characteristics of the individual glaciers, like the amount of debris cover, or differences in local precipitation and temperature projections. Places like Hindu Kush and Pamir, for example, will experience a mean increase in temperature over 2 degrees, while other locations like the Central Himalayas will be closer to the global mean increase.
The team achieved their results by running their model across several climate scenarios and produced a map that showed the differences in glacier loss in different areas under different climate projections. In particular, their model looked at the effects of different Representative Concentration Pathways (RCPs). These pathways range from scenarios that project under 2 degrees Celsius warming (RCP2.6) up to more than 5 or 6 degrees warming (RCP 8.5). The numbers after RCP represent the amount of radiative forcing, which is the difference between the amount of heat from the sun that enters the earth’s atmosphere and the amount of radiation emitted back out into space from the earth. RCP 8.5 is often described as a “baseline” or “business-as-usual” scenario where little or nothing is done to combat climate change.
Of course, there is a fair amount of uncertainty in this research. It is unclear how much the climate will change in the coming decades. For the most part, it depends on how the world tackles carbon emissions, which is why the researchers “included the entire scope of climate projections for this very reason.” Kraaijenbrink and his team also collaborated with other glacier modelers in the Glacier Model Intercomparison Project. According to Kraaijenbrink, “The aim of this is to reduce uncertainties in glacier projections in order to provide better predictions to be used for impact studies and by policymakers.”
The researchers paid special focus to debris-covered glaciers because up until now these glaciers in Asia were not well represented in the models. As part of the study, Kraaijenbrink found that about 11 percent of Asia’s high mountain glaciers are covered with debris, with the largest relative coverage in Hindu Kush.
Debris-covered glaciers are particularly difficult to model because researchers have to take into account how the rocks and other materials covering the glacier will affect retreat. In many cases, the debris insulate or protect the glacier from some amounts of radiation and warming. According to Kraaijenbrink, incorporating the debris-covered glaciers in their model allowed them to get a better estimate of future mass loss and understand how different glaciers in different areas would behave.
While the researchers looked at the effects of all RCPs in the region, Kraaijenbrink says the team chose to spotlight the study on 1.5 degrees because “the IPCC specifically requested studies that consider the effects of limiting temperature rise to 1.5 degrees.” The IPCC is currently preparing a report on the effects of 1.5 degrees of warming, and likely this research will be included to assess the seriousness such a temperature increase.
The study pays close attention to the effects of climate mitigation on glacier shrinkage. Christian Huggel, a glaciologist at the University of Zurich, who was also not affiliated with this study, told GlacierHub that the research “shows concretely what different mitigation policies imply for the glaciers in the high mountains of Asia. And that [there’s] actually a huge difference whether we will be successful in reducing emissions (like 1.5°C warming of RCP2.6), or not (RCP8.5).”
The urgent need for mitigation becomes more evident as the body of research showing the massive effect of anthropogenic climate change, from the tropical Andes to the high mountains of Asia, grows. This urgency, in turn, may hopefully stimulate more effective action to combat climate change.
Future Acceleration of Antarctic Ice Sheet Retreat
From Nature: “Marine ice-cliff instability (MICI) processes could accelerate future retreat of the Antarctic Ice Sheet if ice shelves that buttress grounding lines more than 800 meters below sea level are lost. The present-day grounding zones of the Pine Island and Thwaites glaciers in West Antarctica need to retreat only short distances before they reach extensive retrograde slopes. When grounding zones of glaciers retreat onto such slopes, theoretical considerations and modelling results indicate that the retreat becomes unstable (marine ice-sheet instability) and thus accelerates. It is thought that MICI is triggered when this retreat produces ice cliffs above the water line with heights approaching about 90 meters.”
Discover more about how marine ice-cliff instability could accelerate future retreat of the Antarctic Ice Sheet here.
Glacier Melt Reduces Buffer Capacity
From Waters Resources Research: “Glaciers store large amounts of water in the form of ice. They grow and shrink dominantly in response to climatic conditions. In Central Asia, where rivers originate in the high mountains, glaciers are an important source for sustainable water availability. Thus, understanding the link between climate, hydrology, and glacier evolution is fundamental. Some instruments mounted on satellites are capable of monitoring glaciers. However, the potential of these sensors is limited by technical constraints that will affect the availability and precision of the products. In order to overcome these shortcomings and investigate glacier dynamics, we use a numerical model that represents the relevant processes of the hydrological cycle with a very fine spatial and temporal resolution. Our results show that glaciers buffer extreme weather conditions to provide sustainable river flow. This functionality is put in jeopardy due to the currently observed glacier retreat, in the Pamir Mountains.”
Read more about how glaciers buffer against river runnoff here.
How will Asia’s Glaciers React to Increases in Global Temperature?
From Nature: “Glaciers in the high mountains of Asia (HMA) make a substantial contribution to the water supply of millions of people, and they are retreating and losing mass as a result of anthropogenic climate change at similar rates to those seen elsewhere. In the Paris Agreement of 2015, 195 nations agreed on the aspiration to limit the level of global temperature rise to 1.5 degrees Celsius ( °C) above pre-industrial levels. However, it is not known what an increase of 1.5 °C would mean for the glaciers in HMA. Here we show that a global temperature rise of 1.5 °C will lead to a warming of 2.1 ± 0.1 °C in HMA, and that 64 ± 7 per cent of the present-day ice mass stored in the HMA glaciers will remain by the end of the century.”
Learn more about the impact of climate change and increasing temperature on Asia’s glaciers here.
The volcano, Chimborazo, in Ecuador, is home to a glacier that like many tropical glaciers is quickly receding. When Jeff La Frenierre, a geographer at Gustavus Adolphus College, headed to the Andes, his main objective was to understand how glaciers on this particular mountain had been responding to climate change. However, in the midst of his research, he realized he couldn’t reconcile precipitation data from weather stations with changes in the area of the glacier. To resolve this data-conflict, he turned to a technique too often ignored in the sciences: he talked to people.
La Frenierre published his findings which drew from these conversations last February, illustrating the importance of synthesizing empirical data with information from other sources, like the observations of local residents, to better understand the local effects of climate change.
Chimborazo, just south of the equator, is a place where you wouldn’t expect to find glaciers, but with a nearly four-mile-high peak (6,263 meters) the temperatures remain below freezing, so snow doesn’t melt, turns to ice and can eventually form glaciers. The glaciers found on Chimborazo are extremely important to the communities that live near the mountain. For example, glacier ice-melt is used to irrigate crops and to supply households for their domestic needs. Because of this reliance on glacial water, the people living around Chimborazo took notice when their water supply changed.
Across the board, locals in the area said that they noticed a change in rainfall and surface water in the last several decades. Though meteorological records indicated there was some warming between 1986 and 2011, the precipitation records did not suggest that rainfall amounts had changed, according to La Frenierre’s findings. But this didn’t match with the observable decrease in total ice on the mountain. The increase in temperature shown in the instrumental records could only account for about half of the glacier’s ice loss, while the survey results from local residents overwhelmingly supported the ice records.
“It would’ve been very easy, and the typical thing that many scientists would do, to look at an instrumental record and say: ‘There’s my data, there’s my conclusion from that data,’” La Frenierre told GlacierHub by phone. “If I’d left that alone then I would have had one perception of what was happening here, but clearly, looking at the instrumental data alone wasn’t good enough.”
Of course, it was important to make collecting survey data from local residents rigorous. La Frenierre accomplished this in several ways, aiming to get as broad a perception of environmental change as possible. He only collected information from people who had lived in the area for at least 10 years, for example. He also randomized the sample population by going to randomly generated coordinates within the sample area and speaking with the nearest person or household, using open-ended questions. He also conducted focus groups with members of one of the major irrigation systems.
“That’s why for me, it’s really convincing,”La Frenierre said. “There’s so much ubiquity in certain responses, so the fact that there’s less precipitation, that other sources are drying up, that the vast majority, 90 percent of people, are saying the same thing, and they’re saying it without having been given the leading questions.”
Changes in glacier size and ascension were established through remote sensing techniques, compositing satellite imagery and aerial photographs from different years. This process was complicated by the volcano’s location, because there is no cold or warm season this close to the equator, making it a challenge to determine how much of the glacier is actually glacial ice versus snow. Generally, when mapping glacial extent over time (particularly in temperate regions), researchers look at the end of the warm season. After summer melt there is minimal fresh snow and it is easy to see the entirety of the landscape.
At Chimborazo, because it is so close to the equator, there wasn’t a single image that had both the least amount of snow and was free of cloud cover. Because of this, La Frenierre ended up making mosaics combining several images that were at times months apart. This means the data cannot clearly say what the glacier extent was on any given day, but it still gives a reasonable sense of what the glacier extent was like in a certain year. This data, the changes in the glacial extent and collected opinions of locals, all pointed toward a decrease in overall precipitation. Or, as La Frenierre speculates, a change in the timing of precipitation: “In the tropics, a huge control on melting ice is the surface albedo [how much sunlight is reflected off] of the glacier. A lower frequency of snowfall, even if the same amount of snowfall falls, could actually accelerate the glacier melting.” In other words, a given amount of snow would increase the reflectivity, the albedo, of the glacier if spread over a longer period of time.
La Frenierre’s paper is not the first to be published that combines both physical instrumental or observed data with public observations. The authors cite others who have also successfully used a mixed-methods approach. But, according to La Frenierre, there should be more like it. “The reality is, especially when looking at things like environmental change, your instruments can only tell you so much. And if you can find that people are experiencing something that your instruments can’t rectify, then I think we have an obligation to try to understand where that disconnect is and look for information that answers it without assuming that our instruments are right and our people are wrong.”
The people living around Chimborazo are already directly experiencing the impacts of climate change. Although there are local actions that may have contributed, most of what is happening to the glacial ice on Chimborazo is due to global actions. “The glacial retreat that we’re seeing here is a function of the amount of carbon dioxide and other greenhouse gases that the developing world put into the atmosphere,” said La Frenierre, “We’re looking at a problem for people who are on the front lines of experiencing impacts, yet they were not the ones to benefit at all from the development that we got from putting these greenhouse gases [into the atmosphere].”
We’ve covered images from NASA’s Operation IceBridge on Photo Fridaybefore. But as any good project is wont to do, they continue to release spectacular images on their main site and Twitter page. The project began its 9th year with the launch of two simultaneous campaigns. This is a first for the project, launching two flights from two continents (South America and Antarctica) at the same time, but the team hopes it will allow them to expand their coverage into East Antarctica while maintaining surveys near the Antarctic Peninsula.
This Friday, enjoy some images of glaciers from a recent NASA IceBridge flight.
Baffin Island in Nunavut, Canada, has served as the backdrop for dozens of investigations into glaciation and ice-age patterns. Now a new paper takes a unique look at assigning ages to some of the oldest moraines from the most recent episode of glacier expansion in the Canadian Arctic.
Moraines, ridges of debris deposited alongside or in front of a glacier, can contain valuable data for understanding past climate. The positions of these debris are controlled by temperature and precipitation, which when combined with moraine dating can help construct a picture of past glacier margins. Ice-cored moraines fronting debris-covered glaciers, like the ones this paper investigated, are formed when glaciers with debris on them, like rocks and sediment, retreat and leave behind sections of debris-covered ice. Over time, that ice slowly melts— and its melt-rate is affected (often further slowed) by all the debris that cover and protect the ice from solar radiation. These ice-cored moraines, named because they are moraines with remnants of glacial ice, are notoriously difficult to study because there are many factors that influence how accurately they can be dated. Fully extrapolating the glaciers’ positions and age from the ice-cored moraines also depends on the long history of temperature and precipitation in the area, which contributes to glacier formation and melting. However, when all these factors are accounted for, the positions of these debris can show the location of past glacier margins, reflecting the size of glaciers in the past.
To date the moraines, the researchers examine the concentration of a beryllium isotope, 10Be, that accumulates only in some minerals (like quartz) in the uppermost layers of rocks. The rate of accumulation is well understood and based on cosmic ray interactions in the atmosphere and within the rock itself. Since only rocks on the earth’s surface accumulate 10Be, researchers can calculate how long that rock was exposed on the earth’s surface by comparing the concentrations of isolating a sample of 10Be in a rock from a moraine to other well-dated rocks. GlacierHub spoke with Sarah Crump, the lead author on this paper, who explained that with this information “we can estimate when a glacier was extended to the location of the moraine, and thereby make inferences about climate at the time.” Using this data, they reported that the moraines likely formed5,200 to 3,500 years ago during the Neoglaciation of the Late Holocene.
However, 10Be dating has some uncertainty.Crump and her team realized that because “the 10Be ages exhibited quite a bit of spread,” they needed to take a closer look at the glacial setting and mechanics of moraine formation. “We thus teamed up with co-author Leif Anderson to collect glaciological data at the field sites and model a simplified, representative debris-covered glacier,” she said. Additionally, they used field observations of the moraines to decipher if the debris had evolved since their initial formation. The researchers looked for evidence of morphological changes caused by uneven ice melting over time, or moraine degradation leading to surface boulders to roll and new boulder faces to emerge— all of which can affect 10Be dates. The results of the paper combine findings from these three methods: 10Be dating (or more formally cosmogenic radionuclide dating), numerical modeling based on field collected glaciological data, and field observations for moraine evolution.
Due to this collaboration and methodology, this study is unique. Michael Kaplan, a paleoclimatologist at Columbia University, commented on the novelty of this research: “I am not familiar with another paper that uses these three approaches (and the different respective experts as coauthors) in the manner that Crump et al. do.”
Though this combination of methods is novel, Crump stated that there are still some uncertainties in the precise formation age of the moraines. Often, 10Be dating results can deliver ages that are either older or younger than the actual age of the moraines. For example, rocks and boulders that ended up on a moraine might have arrived before glacial erosion, which would result in an age that was too old. The other two methods— field observations and numerical modeling— helped inform their final conclusions and significantly reduced uncertainty (though some uncertainty inherent to 10Be dating can never be completely eliminated).
Overall, Crump hopes that “readers will take note of the very important role of debris in glacier systems, both in terms of how they respond to climate variability and in terms of their geomorphic effect on the landscape.” These results show the importance of taking into account the glacial setting and help to clarify and identify some of the uncertainty around the moraine record, giving a deeper understanding of the relationship between glacier fluctuation and climate variability, allowing researchers to gather more detailed and accurate information about past climates and therefore better assess the future.
If you’re interested in learning more about the area, Gifford Miller, a co-author of the paper has an informative video about Baffin Island and its importance.
From Earth Systems Dynamics: “Largely depending on the meltwater from the Hindukush–Karakoram–Himalaya, withdrawals from the upper Indus Basin (UIB) contribute half of the surface water availability in Pakistan, indispensable for agricultural production systems, industrial and domestic use, and hydropower generation. Despite such importance, a comprehensive assessment of prevailing state of relevant climatic variables determining the water availability is largely missing. Against this background, this study assesses the trends in maximum, minimum and mean temperatures, diurnal temperature range and precipitation from 18 stations (1250–4500 m a.s.l.) for their overlapping period of record (1995–2012) and, separately, from six stations of their long-term record (1961–2012).”
Learn more about climate trends and runoff of the upper Indus Basin here.
Proglacial Lake Cores from Southeast Greenland
From Quaternary Science Reviews: “Accelerating ice loss during recent years has made the Greenland Ice Sheet one of the largest single contributors to global sea level rise, accounting for 0.5 of the total 3.2 mm yr−1. This loss is predicted to continue and will most likely increase in the future as a consequence of global warming. However, the sensitivity of glaciers and ice caps (GICs) in Greenland to prolonged warm periods is less well constrained and geological records documenting the long-term glacial history are needed to put recent observations into a broader perspective. Here we report the results from three proglacial lakes where fluctuations in local glaciers located at different altitudes in Kobbefjord, southwest Greenland have been recorded.”
Read more about three proglacial lake records from Kobbefjord, southeast Greenland here.
Modeling Stream Habitats and Salmon Genetic Diversity
From Journal of Fish Biology: “Measures of genetic diversity within and among populations and historical geomorphological data on stream landscapes were used in model simulations based on approximate Bayesian computation (ABC) to examine hypotheses of the relative importance of stream features (geomorphology and age) associated with colonization events and gene flow for coho salmon Oncorhynchus kisutch breeding in recently deglaciated streams (50–240 years b.p.) in Glacier Bay National Park (GBNP), Alaska. Population estimates of genetic diversity including heterozygosity and allelic richness declined significantly and monotonically from the oldest and largest to youngest and smallest GBNP streams.”
Discover more about the genetic diversity of coho salmonhere
The glaciers of southeast Greenland are not easy to research. You ride in on a small fishing boat, searching among the icebergs for the best place to stick a glorified straw into the mud. Which is just what a team of researchers did in 2011 to retrieve a sediment core that describes 9,000 years of history from the Køge Bugt glacier system. In September, the team released a paper in Nature’s Scientific Reports describing the results.
The Køge Bugt glacier system contains three of the largest glaciers of the Greenland Ice Sheet, all of which have contributed to recent ice loss. Because of the lack of previous research in the area, investigating this system promised worthwhile results. The team collected a nearly two-meter-long sediment core from the center of Køge Bugt, the body of water that also gives the glacier system its name. This area receives sediment input from the three glaciers in the system, and while the core cannot provide inference about the individual glaciers, it gives information about the system’s collective behavior, according to the report.
“We expected it to be a record that would, if we were lucky, be just a few thousand years and possibly even much less than that, so it was really quite a surprise when we got our first radiocarbon dates back,” lead researcher Laurence Dyke told Glacier Hub. A record this old, especially for a glacier system like Køge Bugt, with little previous historical research, can now provide baseline data to contrast with the changes in the system over the last two decades.
Compared to the more well-studied Jakobshavn Glacier in Western Greenland, the levels of retreat exhibited by Køge Bugt over the past 9,000 years appear minimal, the team notes. There is evidenceof Jakobshavn retreating in the order of 30 to 50 kilometers further inland than its current location during the Holocene. Køge Bugt seems to have only retreated five or six kilometers. Due to the difficulty of studying this area, it is hard to say how anomalous these results are without further investigation.
The researchers attribute this minimal retreat of Køge Bugt glaciers to their sub-ice topography. Most studied glaciers on Greenland sit in a deep fjord system several hundreds of kilometers long– essentially a long trough that runs onto the continental shelf and inland beneath the glacier. However, the glaciers in the Køge Bugt system are different. These glaciers sit on a steep bedrock slope, more like a bowl than a trough. This helped to stabilize the glacier throughout the Holocene.
While the researchers are not sure of what caused this configuration, Dyke says it’s certainly what is controlling the glaciers’ behavior. “If you want to predict the whole of Greenland,” says Dyke, “then you really need to have very good geometry of both the sub-ice and the sub-ocean.” Dyke and his team hope that their research into Køge Bugt will be used by climate modelers to further inform how models reflect glacier geometry and to interpret the Køge Bugt system’s current and future behavior.
The paper’s findings would not be so striking if not for recent activity in the system. Based on the historical record, it is surprising that these glaciers have changed so much in recent years. The loss of ice between 2003 and 2012 is about one-third of the maximum ice that could have been lost in the Holocene before these glaciers would have retreated out of tidewater, according to Dyke. “However, it is important that we can’t be sure that the glaciers didn’t change as much as they currently are at other periods during our record,” he said. “What we can say with certainty is that if the glaciers continue to retreat just a few more kilometers, and retreat onto land, this will be unprecedented within at least the last 9,000 years, and in all likelihood, the last 130,000 years.”
Rising temperatures in the ocean and atmosphere affect glaciers around the globe, and despite its unique setting, Køge Bugt is no exception. “There’s some pretty good predictions now of what will happen to Greenland in the long run,” Dyke said.“Greenland is going to get a lot smaller. These glaciers will retreat out of the water, and how quickly that happens really depends on how warm the atmosphere and the oceans get. And that’s something that ultimately we have control over.”