From Earth and Planetary Science Letters: “This study provides ground-truth for regional indirect GHF [Geothermal Heat Flow] estimates in the Amundsen Sea Embayment, which is part of the West Antarctic Rift System, by presenting in situ temperature measurements in continental shelf sediments. Our results show regionally elevated and heterogeneous GHF (mean of 65 mWm-2) in the Amundsen Sea Embayment.“
From Limnology and Oceanography: “Arctic waters are often enriched with terrestrial dissolved organic matter (DOM) characterized by having elevated visible wavelength fluorescence (commonly termed humic-like). Here, we have identified the sources of fluorescent DOM (FDOM) in a high Arctic fjord (Young Sound, NE Greenland) influenced by glacial meltwater.”
Read more about the dissolved organic matter here.
Modeling Dry-Snow Densification
From Geosciences: “In the accumulation areas of ice sheets, ice caps, and glaciers, snow is deposited on the surface and, with time, becomes denser until it turns into ice. This process of densification proceeds at a rate that depends on climatic conditions; slowly in the cold, desert regions in the interior of the great polar ice sheets, and more rapidly in warmer regions with higher precipitation. The question of how to calculate this rate from given climatic information is an important aspect of many areas of glaciological research.”
Read more about the microscopic processes by which snow turns into ice on glaciers here.
Of the many impacts caused by climate change, sea-level rise threatens to be one of the most devastating due to the thermal expansion of the oceans and the melting of ice and glaciers on land. These impacts, along with numerous others related to rising global temperatures, may in the future motivate a country, a group of countries, or even a very rich individual to pursue solar geoengineering, a controversial proposal for limiting the amount of solar radiation that reaches the Earth’s surface. A recent study in The Cryosphere assessed the efficacy of such a solar geoengineering attempt at limiting global sea-level rise.
Geoengineering, as it relates to climate change, falls into two categories. The first, atmospheric carbon removal, entails physically removing carbon dioxide from the air to reduce greenhouse gas concentrations and limit temperature rise. The second, solar geoengineering, involves injecting sulfur dioxide or another aerosol into the stratosphere to reflect a portion of incoming solar radiation, again limiting temperature rise.
Because of the temperature-reducing effect of solar geoengineering, research suggests that such a proposal would also reduce sea-level rise. However, just how effective solar geoengineering could be in limiting sea-level rise had not yet received sufficient research, according to Peter Irvine, the lead author of the study, who spoke with GlacierHub. Irvine and his team of scientists hoped to “shed some light on the complexities of the sea-level rise response to solar geoengineering, make an initial evaluation of its efficacy, and to bring this issue to the attention of the cryosphere research community,” Irvine told GlacierHub.
Initially, the researchers conducted a literature review on the small number of studies that explored the cryosphere’s potential response to solar geoengineering. A 2009 study that examined the Greenland Ice Sheet found that under a scenario where atmospheric concentrations were quadrupled, solar geoengineering could slow or even prevent the collapse of ice sheets. Conversely, a 2015 study determined that while solar geoengineering could slow melting, glaciers and ice sheets would not recover to past states. Lastly, a 2017 study focusing on high-mountain Asia, found that solar geoengineering would stop temperature increases; however, 30 percent of glaciated area would still be lost.
Following the literature review, the researchers evaluated the potential effect of solar geoengineering on three aspects of sea-level rise. The first aspect was thermosteric sea-level rise, or more simply, the thermal expansion of ocean waters. Because temperature is the dominant influence on thermosteric sea-level rise (warmer water is less dense than cooler water), the decrease in solar radiation reaching the Earth’s surface due to solar geoengineering would limit sea-level rise.
Secondly, the researchers examined solar geoengineering’s effect on the surface mass balances of glaciers and ice sheets. Surface mass balance is primarily affected by the surface melt rate, which is the result of the availability of energy at the surface of the ice. Thus, a change in solar radiation reaching the Earth’s surface would likely reduce surface melt. The analysis of large volcanic eruptions offers an analogous example to what might happen to surface melt if solar geoengineering were pursued because the dust and ash released during an eruption blocks some incoming solar radiation.
One study examined by the researchers showed that surface mass balances in Greenland were at their maxima in the year after the El Chicón and Pinatubo eruptions in 1982 and 1991, respectively. Similarly, another study in Greenland found that in the years following the El Chicón and Pinatubo eruptions, surface runoff was the third lowest and lowest, respectively, between the years 1958 and 2006, further reinforcing the expectation that solar geoengineering would limit surface mass balance reductions.
In addition to its effect on temperature, solar geoengineering would also affect the global hydrologic cycle and subsequently sea-level rise. Warming temperatures due to climate change will likely lead to more precipitation worldwide; however, if solar geoengineering is pursued, this increase could be offset. This precipitation change would affect both Greenland and Antarctica, according to Irvine.
In Greenland, surface melt changes, not precipitation accumulation, are the primary influence on surface mass balances; therefore, solar geoengineering would likely have a positive effect by reducing temperatures, with the decrease in precipitation unlikely to lead to mass balance decline. In Antarctica, on the other hand, increased precipitation due to climate change has had a positive effect on surface mass balance, thus a decrease in precipitation due to solar geoengineering would negatively impact mass balances.
The third and final sea-level rise aspect examined by the researchers to evaluate the efficacy of solar geoengineering was ice lost through calving and eventual ice-sheet collapse. Calving, the scientific name for icebergs breaking off a glacier at its terminus, depends on the speed at which ice flows, which itself is driven by climatic changes.
In Antarctica, warming water known as circumpolar deep water (CDW) is the primary driver of calving. CDW is pushed below and then up into glacial cavities by surface winds, where the warm water melts the ice. This melting drives calving and leads to the thinning of glaciers.
While solar geoengineering would likely lower air temperatures, it is unlikely to reduce the temperature of CDW and limit melting and subsequent calving from below. In addition, a 2015 study found that solar geoengineering is unlikely to limit the upwelling of CDW and could even increase upwelling. However, this finding has yet to be replicated, according to Irvine, and it is not clear whether the results are exclusive to the model used.
There is also no guarantee that solar geoengineering would be able to prevent glacial collapse due to marine ice sheet instability. This collapse occurs when a glacier retreats past its grounding line (where ice meets underlying bedrock) and continues to retreat inland until it reaches another stabilizing ridge. The process might already be occurring at West Antarctica’s Thwaites and Pine Island glaciers, which are extremely vulnerable due to the sloping topography upon which they rest.
Nevertheless, retreat and possible collapse might be preventable, says a 2016 study. It showed that returning water to cooler conditions reversed glacial retreat. This finding indicates solar geoengineering may be useful to prevent marine glaciers from destabilizing. While encouraging, it remains likely that certain glaciers, especially those in West Antarctica, will continue to experience significant ice loss regardless of whether solar geoengineering is pursued or greenhouse gas emissions are dramatically reduced.
Based on their study, the researchers lay out four areas in need of future research. First is the need to evaluate the sea-level rise response to solar geoengineering scenarios in conjunction with climate change scenarios so that the efficacy of solar geoengineering and greenhouse gas emissions reductions can be compared. Second is the need to employ regional models of surface mass balance in order to assess the effectiveness of solar geoengineering to limit mass balance losses. Third, the researchers recommend additional evaluation of the effect of solar geoengineering on the CDW upwelling and stability of glaciers and ice-shelves. Finally, the researchers recommend the evaluation of sea-level rise risk, alongside the numerous other risks and challenges associated with solar geoengineering.
The potential for solar geoengineering to limit sea-level rise from the cryosphere is still up for debate, but as this study shows, it may have the potential to reduce temperature and curb some aspects of sea-level rise, including surface mass balance losses and ocean thermal expansion. However, for other aspects, mainly the melting of glaciers from below by warm waters, it may be unlikely that solar geoengineering can limit sea-level rise contributions. Nonetheless, when it comes to the society-altering impact of sea-level rise, solar geoengineering could be a part of humanity’s response.
West Antarctica’s Pine Island Glacier (PIG) is the fastest melting glacier in Antarctica, making it the single biggest contributor to global sea-level rise. The main driver of this rapid loss of ice is the thinning of the PIG from below by warming ocean waters due to climate change. However, a recently published study in Nature Communications discovered a volcanic heat source beneath the PIG that is another possible driver of the PIG’s melting.
The study was a result of a larger project funded by the National Science Foundation and the U.K. National Environmental Research Council to “examine the stability of the Pine Island Glacier from the terrestrial and the ocean side,” according to the lead author Brice Loose, who spoke with GlacierHub about the research.
The West Antarctic Ice Sheet (WAIS), which includes the PIG, sits on top of the West Antarctic Rift System that includes 138 known volcanoes. It is difficult, however, for scientists to pinpoint the exact location of these volcanoes or the extent of the rift system, because most of the volcanic activity occurs below kilometers of ice.
Warming ocean temperatures due to climate change have long been identified as the primary contributor to the extensive melting of the PIG and other glaciers that transport ice from the WAIS. This melting is largely driven by Circumpolar Deep Water (CDW), which melts the PIG from below and leads to the retreat of its grounding line, the place where the ice meets the bedrock.
To trace CDW around coastal Antarctica, the scientists used helium isotopes, specifically He-3, because CDW is widely recognized as the principal source of He-3 in the waters near the continent. For this study, the scientists used historical data of helium measurements from the Weddell, Ross, and Amundsen seas around Antarctica. They looked at the 3 seas, all of which have CDW, and examined differences in He-3, which could have come from volcanic activity.
By tracing the glacial meltwater produced by the CDW, the researchers discovered a volcanic signal that stood out in their data. The helium measurements utilized were expressed by the percent deviation of the observed data from the atmospheric ratio. For the observed CDW in the Weddell Sea, this deviation was 10.2 percent. In the Ross and Amundsen Seas, it was 10.9 percent. However, HE-3 values gathered by the team during expeditions to the Pine Island Bay in 2007 and 2014 differed from the historical data.
For this data, the percent deviation was considerably higher at 12.3 percent, with the highest values being near the strongest meltwater outflow from the PIG’s front. Additionally, these high helium values coincided with raised neon concentrations, which are usually an indication of melted glacial ice. The helium was also not uniformly distributed. This suggests it originated from a distinct meltwater source and not from across the PIG’s entire front.
With this knowledge in hand, the team of scientists endeavored to identify the source of the HE-3 production. The Earth’s mantle is the largest source of HE-3, although it is also produced in the atmosphere and during past atmospheric tests of nuclear weapons through tritium decay. These two sources, however, could only account for 0.2 percent of the 2014 data.
Another potential source was a fissure in the earth’s crust directly below the PIG, where He-3 could rise from the mantle. However, this source was ruled out as it would have a strong thermal signature, something that was not discovered by mapping expeditions.
The researchers then considered another source: a volcano beneath the PIG itself, where He-3 escapes from the mantle in a process known as magma degassing. The He-3 could be transported by glacial meltwater to the PIG’s grounding line, where the ice meets the underlying bedrock. At this line, the ice shifts due to the ocean tides, allowing the meltwater and the He-3 to be discharged into the ocean. After identifying a subglacial volcano as the most likely source of the elevated He-3 levels near the PIG’s front, the scientists next calculated the heat released by the volcano in joules per kilogram of sea water at the front of the glacier. It turned out that the heat given off by the volcano constitutes a very small fraction of the overall mass loss of the PIG compared to the CDW, according to Loose. In total, the volcanic heat was 32 ± 12 joules kg-1, while the heat content of the CDW was much larger at 12 kilojoules kg-1. Nevertheless, if the volcanic heat is intermittent and/or concentrated over a small surface area, it could still have an impact on the overall stability of the PIG by changing its subsurface conditions, said Loose. There is also the possibility that the continued melting of the PIG could lessen the pressure and weight on the volcano, spurring more volcanism and subsequent melting.
The presence of an active volcanic heat source beneath the world’s fastest-melting glacier is a disturbing discovery that threatens to accelerate the PIG’s contribution to future sea-level rise. To develop a better understanding of how the volcano might impact the PIG, Loose stated that future studies should examine how the volcanic signal varies from year to year and attempt to pinpoint the likely location of the volcano itself beneath the ice.
The Pine Island Glacier (PIG) is losing ice rapidly. During the past 25 years, the ice of the PIG and its neighboring glaciers in west Antarctica’s Pine Island Bay thinned between 3.9 and 5.3 meters a year, accounting for about 5 to 10 percent of observed global mean sea-level rise. Before 2015, however, the front of the PIG had been at a relative standstill since the 1940s, not retreating as one might expect of a melting glacier. Why? To account for this unique situation, a recently published study in The Cryosphere points to ridges below the ice that likely held the PIG’s ice front in place despite its rapid melting.
In August 2015, the long steady front of the PIG changed significantly when large sections of ice broke off during a calving event when the glacier retreated upstream and its orientation shifted. This change presented an exciting opportunity in 2017 for researchers from the Alfred Wagner Institute for Polar and Marine Research to map the seafloor formerly covered by the PIG.
To complete this mapping project, the researchers employed an echo sounder mounted to the hull of the research vessel RV Polarstern, in addition to complementing remote sensing data acquired by satellite. The information acquired by the expedition through echo sounding showed the seafloor features that were present below the PIG. With this data in hand, the researchers had the idea to correlate this information with satellite data from the past to the present to better understand the role of these features for the calving behavior of PIG, according to lead author Jan Erik Arndt, who spoke with GlacierHub about the study.
These survey methods revealed a complex, underwater landscape once covered by the PIG. The discoveries included a 10-kilometer long ridge and two other high points. At its deepest point, Pine Island Bay reaches down over 1,000 meters, while the submarine ridge peaked at 375 meters below the ocean’s surface and the two downstream high points peaked at 350 and 250 meters below the surface
How did these sub-surface features impact the PIG? Satellite data from January 1973 until March 2005 showed a rumple in the PIG’s ice above the location of shallowest section of the underlying ridge. A glacial rumple is similar to a bump on a beach towel that suggests there is a beach toy or pile of sand below it. In the case of the PIG, the ridge below the ice acts as an obstacle in the the way of the ice, leading to a raised section of the glacier directly above the point of contact between it and the ridge. This rumple is not observed after March 2005 in the satellite data, indicating that the ice after this date had thinned to such a degree that it either was no longer in contact with the ridge or was too light to produce a signature on the surface.
The loss of contact with the ridge was consequential. In the time before this separation when the PIG was in contact with the underwater ridge, the ridge acted as a “pinning point,” holding it in place. However, after the ice had thinned considerably, the ridge no longer acted as a restraint on the PIG. As a result, in the time since there was evident contact between the two, four major calving events occurred.
The first of these events took place in 2007 when the PIG advanced and made contact with one of the subsurface downstream high points (A in figure 3). This impact placed what is known as “back stress” on the glacier upstream from the point of contact, causing rifts to form in the ice and ultimately leading to the calving event.
The process leading to the 2011 calving event was similar, the researchers state. In this instance, the second subsurface high point (B in figure 3) trapped a dense cluster of icebergs between it and the PIG ice shelf, placing back stress on the upstream ice leading to the calving event.
The 2015 event was different: The ice-flow velocity of the northern edge of the PIG’s ice shelf was nearly at a stand still, whereas the velocity of the ice shelf’s central and southern edges increased. Further, the direction of the northern edge’s ice flow shifted around 3 degrees clockwise, while the direction of the central and southern edges did not change (C in Figure 3). The reason? The northern edge of the ice-shelf was likely making slight contact with the submarine ridge, according to the authors.
As a result, the calving line that had not changed orientation in decades finally did change due to the loss of contact between the ice and its previous pinning points as well as from melting from below driven by warm ocean waters. The most recent calving event which occured in 2017 happened along the same orientation, which aligns with a new pinning point to the north near Evans Knoll, a small snow-covered hill that rises above sea level. The point near the knoll is likely one of the last anchors acting on the PIG, according to Arndt.
This new calving line and loss of contact with past pinning points could have grave implications for PIG. A 2017 study on the PIG and a number of other glaciers in the area found that changes to a glacier’s ice shelf propagate upstream within just a few years. For the PIG, this likely means the glacier’s flow will speed up and thinning will increase, leading to further melting.
It is unlikely the PIG’s calving line will retreat much further over the next few years thanks to the new pinning point stabilizing the glacier near Evans Knoll. However, the authors note that there is continued thinning due to melting. This thinning has the potential to destabilize the glacier and unfortunately may have already started, according to Arndt. The large icebergs produced by the recent calving events have broken up into smaller icebergs much more quickly due to the thinner ice than events in the past, when they remained stable for longer. This ongoing breakup and subsequent melting of calved icebergs will contribute to already rising global sea-levels, threatening the millions of people who live along the coast. And unlike the ridges that held the front of the PIG for decades, many coastal communities will not have anything to hold back the sea.
From Science: “Some locations on Mars are known to have water ice just below the surface, but how much has remained unclear… The ice sheets extend from just below the surface to a depth of 100 meters or more and appear to contain distinct layers, which could preserve a record of Mars’ past climate. They might even be a useful source of water for future human exploration of the red planet.”
From The Maritime Executive: “The U.S. Coast Guard’s International Ice Patrol said Thursday that 2017 was the fourth ‘extreme’ season in a row for icebergs in the North Atlantic, with 1,008 bergs tallied in the shipping lanes… The count was high due to powerful storms and to the retreat of Greenland’s glaciers, which both contributed to more calving events.”
Check out more information about the migrating icebergs here.
Ice-diving Drones on Risky Mission at Antarctic Glacier
From Scientific American: “This month a fleet of seven underwater robots developed by the University of Washington (U.W.) in Seattle is heading into this world on a risky yearlong mission. Their goal: help forecast sea level rises by observing the melting process in this hidden topsy-turvy world, where layers of warm and cool water mix at the shelf.”
Explore more about the dangers facing the drones and their mission here.
Cracks in ice shelves have appeared in disaster movies as ominous signs of global warming. One memorable instance occurs in The Day After Tomorrow when a paleoclimatologist is drilling ice cores at the Larsen Ice Shelf. The shelf breaks apart, leading to a series of cataclysmic climate events that disrupt the North Atlantic Ocean circulation. In July, a real- life crack appeared at Petermann Glacier in Greenland and has been growing steadily ever since. Two scientists, Andreas Muenchow and Keith Nicholls, are investigating the crack and hypothesize that it is caused by an increase in air and ocean temperatures.
Petermann Glacier connects the Greenland ice sheet to the Arctic Ocean at 81°N. It is approximately 43 miles long and nearly 10 miles wide. This is not the first crack or full break of ice at Petermann Glacier, according to a Washington Post article by Chris Mooney. Since 2010, entire slabs of the Petermann glacier have broken off.
In fact, during two occasions, the glacier lost an area of ice six times the size of Manhattan, according to Mooney. This loss raises enormous concern because the glacier serves to slow down the flow of ice downhill from the Greenland ice sheet into the ocean. For this reason, experts call Petermann a “floodgate.” If the glacier that sits behind Petermann melts, it could raise sea levels by about a foot.
A recent paper published in the Geophysical Research Letters describes this type of calving at Petermann as common. The authors explain that it is usually assumed that ocean-ice dynamics are not involved. However, evidence from the Pine Island Glacier in West Antarctica found that ocean forcing can play a role in the melting.
Muenchow and Nicholls expect similar dynamics are occurring with Petermann Glacier. They have been on several expeditions to the glacier in order to measure ocean temperatures underneath the shelf itself. They want to see if rising ocean temperatures are also detrimental to the glacier and causing the melting from below.
If warm ocean water were melting the base of the glacier, it would only accelerate the destruction of Petermann. While it is extremely difficult to know definitively, they hypothesize Petermann’s river and the channel beneath it are playing a role in the melting.
Data from 2015 and 2016 demonstrates that the temperatures of the warm Atlantic layer in the ocean have increased. With both air and ocean temperatures getting warmer, it is unclear how much longer Petermann Glacier will be intact, leaving frightening implications for the melting of the enormous glacier behind it. The crack in the Petermann Glacier and the possible ensuing events show that news from the ice can sometimes be just as scary as the scenes in disaster movies.
Antarctica, the world’s southernmost continent, is a hostile realm of ice and snow, fictionalized in our popular culture by the likes of H.P. Lovecraft and further romanticized by real-world scientific explorers eager to lay claim to the region.
Humans who venture to the southernmost pole do so by way of the Antarctic Peninsula, where they may visit Port Lockroy, site of a former British research station, or take in by cruise the vast terrain and wildlife of the region. Multiple countries also operate scientific camps and research programs in more remote locales of Antarctica where science teams study awe-inspiring glaciers and ice sheets throughout the year.
The largest ice sheet in the world, Antarctica is composed of around 98% continental ice and 2% barren rock. The ancient ice is incredibly thick, although it has been thinning due to the effects of climate change.
Several nations have made overlapping claims to the Antarctic continent. The Antarctic Treaty, signed in Washington in 1959, attempts to maintain peace, by neither denying or providing recognition to these territorial claims. Today, a total of 53 countries have signed the treaty, including Argentina, Australia, Chile, France, New Zealand, Norway and the United Kingdom, countries that have all made specific claims in the region. The United States and Russia, meanwhile, have maintained a “basis of claim” in the region. Scientists of these nations conduct field research from Antarctica bases to gather greater knowledge about climatic changes affecting the larger world.
Studying glaciers in Antarctica is of great impact due to the influence of melting glaciers on global sea levels. In addition, Antarctica plays a primary role in the world’s climate. According to Antarcticglaciers.org, “Cold water is formed in Antarctica. Because freshwater ice at the surface freezes onto icebergs, this water is not only cold, it is salty. This cold, dense, salty water sinks to the sea floor, and drives the global ocean currents, being replaced with warmer surface waters from the equatorial regions.”
Ice sheets in Antarctica are fragile and a number have recently collapsed, causing glacial thinning and threatening a rise in sea levels. Some scientists are concerned that the collapsing ice sheets may not be just a natural occurrence but one more closely linked to a warming planet.
The Pine Island Glacier is one of the “fastest receding glaciers in the Antarctic” and a major contributor to our rising sea levels, according to the U.S. Antarctic Program. Scientists have observed an ice shelf on the Pine Island Glacier that is rapidly thinning, pushing the glacier toward the sea.
A team of scientists constructed a field camp in 2012-2013 to study the impacts of climate change on the glacier, also known as PIG.
The PIG field camp staff learned to contend with adverse weather conditions in the area and events like windstorms, a common occurrence in this remote and hostile part of the world.
Helicopters provide support to field projects such as the one conducted in 2012-2013 at the Pine Island Glacier.
Elsewhere in Antarctica is the McMurdo Dry Valleys, the largest ice-free area in the region—approximately 15,000-square-kilometers— where science teams perform research projects on glaciers, lakes, and soils, funded by the National Science Foundation. The area is an extreme landscape, but it can also be a useful environment for scientists hoping to study the impacts of climate change.
In Antarctica, teams of scientists can extract old ice flowing from the ends of glaciers in large quantities rather than by drilling directly into the ancient ice sheet. Around 350 kilograms of ice is then melted into a vacuum-sealed container to capture around 35 liters of ancient air. The ancient air was preserved by the ice for thousands of years. Scientists hope to research the ancient air and examine the impact of methane gas on past climate change, according to the U.S. Antarctic Program.