[Keith_McClary]

http://www.theonion.com/blogpost/what-a ... iers-56981

[Tanada]

Pictures and videos at link below quote.

The Glaciers on Earth's 'Third Pole' Are Bursting, Causing Deadly Floods
Climate change is creating yet another dangerous new phenomenon.

Central Asia’s glaciers make up the third-largest mass of frozen fresh water on earth, the planet’s “third pole.” The region’s “thousands of glaciers and regular snow melt form the headwaters for 10 of Asia’s biggest rivers, which bring drinking water, power and irrigation directly to 210 million people, while these river basins indirectly support more than 1.3 billion people,” according to the World Wildlife Fund. That resource is now doubling as a hazard, with glaciers skipping the melting process altogether to rupture and flood in a region that has warmed at twice the global rate of climate change.

Last week, a glacier in northeastern Afghanistan burst and flooded the Panjshir River basin, killing at least ten people. The floodwater triggered landslides as it carved through the valley and damaged 56 houses, washed out two bridges, wrecked a highway, broke an irrigation canal, and swamped farmland, according to an internal report from the International Center for Integrated Mountain Development (ICIMOD) , an intergovernmental agency based in Nepal. That same week, a glacier in western China released 35 million cubic meters—or 14,000 Olympic swimming pools—of fresh water into the Yarkant River basin, prompting evacuations, Greenpeace East Asia reported. Both disasters struck in places that are not traditionally at risk for glacial outbreak floods, but catastrophes like these seemed poised to become the new normal.

As glaciers heat up, meltwater can pool into lakes at their feet. The resulting glacial lakes sit behind walls of ice and debris collected by the glacier’s downhill slide called terminal moraines. Think of these as natural dams. But those dams can break due to any number of environmental triggers, including rainfall. In the Panjshir flood, an icecap melted, reportedly triggering a small landslide, which then in turn caused a glacial flood.

Glacial lakes are more likely to form if the glaciers they are under intense heat, which is now very common amid global deglaciation. Different altitudes of the Yarkant River Basin have warmed between 2°C and 3.5°C since 1961, according to data that Greenpeace East Asia collected from the Taxkorgan and Shache meteorological stations in west China.

These kinds of floods are increasing in frequency and tend to occur at lower altitudes, where glaciers often sit closer to civilization, said Arun Shrestha, the regional program manager for river basins and cryosphere at ICIMOD.

In the Yarkant River basin, glacial outbursts have increased markedly since 1980s, research from the Chinese Academy of Sciences shows. In the Yarkant River basin, glacial outburst floods have become far more common since the 1990s. And before last week’s Panjshir flood, Shrestha told me, ICIMOD didn’t even consider glacial outbreak flooding a big issue in Afghanistan. Historically, glacial outbreak floods were normally isolated to high-altitude glaciers. But that’s no longer the case.

“In the eastern Himalayas, the glaciers are quite high up. In the western Himalayas and Karkoram [a mountain range in Northwest India and Pakistan], the glaciers are quite low and quite close to the villages. So, outbursts are very dangerous,” said Shrestha.

ICIMOD is now setting the groundwork for the tricky process of mapping and assessing Afghanistan’s glaciers for hazards. Because of the vast number and immense isolation of glaciers, most of the analysis needs to be done by locals trained in the proper methodology and assisted by remote sensing. The Hindu Kush mountain range in Afghanistan contains more than 3,000 glaciers and China has more than 40,000. To the north, climate change’s impact on the glaciers of Central Asia’s Tien Shan mountains, which stretch from Kyrgyzstan to China, also remains poorly understood. The vast size and complex landscapes of the Central Asian region defy generalization. Information on the conditions that lead to glacial outbreak floods, or even the solutions that mitigate the damage, do not easily translate from ecoregion to ecoregion.

But the stakes of understanding these landscapes are now immense. Glacial outburst floods are geomorphic events—catastrophes by definition. And as bad as the floods are, they aren’t the only consequence of climate change on the third pole. A warmer world means less snow and more rain during winter, and quicker glacial melt in spring. Earlier melts and runoff through winter and spring could cause less fresh water resources when demand is highest, in summer and fall.

“We have seen a lot of cases in the Karakorum and western Himalayas where people are already having problems getting enough fresh water to irrigate their farmlands,” said Shrestha. “In that area, the only source of water is glacial melt. Without any irrigation, they will not have any agriculture.”

In Pakistan, Shrestha said, farmers have turned to innovative means of supplying fresh water for irrigation, namely solar-powered pumps and hydraulic ram pumps, which pump without electricity or diesel by capitalizing on water pressure to convey water through the irrigation system.

That’s not enough, said Liu Junyan, a climate and energy campaigner for Greenpeace East Asia, who added in a statement that monitoring of glacial hazards should be strengthened, climate projection modeling needs to be enhanced, and hydraulic engineering that could mitigate flood damage needs to be constructed.

But the mountainous terrain of Central Asia presents a political problem as well as a glacial flooding risk. The mountain ranges themselves are often borders. Funding, innovation, communication, and policies jigsaw unevenly over the region. Shrestha works in Kathmandu, Nepal. But when we spoke, he was in Delhi, India, struggling to work his way through the various hoops of securing a visa into Afghanistan. Once there, his work will require different strategies for different communities in different places. But when asked which problem is more urgent—the flooding or the droughts, which now disturbingly come hand-in-hand—Shrestha balked at the question.

“These are different kinds of problems,” he told me. “One is a slow onset problem, but with deep impact into livelihood, economic conditions, food security, nutrition, etc. Where the other—the flood—is very rapid onset, and very visible.”

Glacier Outburst Flooding

[jedrider]

Antarctica melting: Journey to the 'doomsday glacier'
https://www.bbc.com/news/science-environment-51097309

[Subjectivist]

How long until this part of the alps is simply free of active glaciers?

Mont Blanc: Glacier collapse risk forces Italy Alps evacuation

Italian authorities have evacuated about 75 people, mostly tourists, from an Alpine valley as huge blocks of ice threaten to crash down from a glacier.

Planpincieux glacier, in the Mont Blanc massif, has weakened because of intense summer heat alternating with night-time cold. It lies above Val Ferret valley, near Courmayeur ski resort.

A local environmental risk expert said the fragile ice could fall at any time.

The threatening glacier section is about the size of Milan cathedral.

The risk manager, Valerio Segor, said "the water flowing underneath can, in fact, act as a slide" and they faced "the risk of immediate collapse".

The fragile 500,000 cubic metres (18m cu ft) of glacier is being monitored with aerial photography and radar.

Roads leading to Val Ferret, a popular area for hikers, have been closed off.

A similar alert and evacuation took place last September, because of the unusually hot Alpine summer, attributed to global warming.

The glacier is at a height of 2,600-2,800 metres (8,500-9,200 ft). The Mont Blanc massif is the highest mountain in western Europe, at over 4,800m.

A Courmayeur official, Moreno Vignolini, said the heatwave had accelerated the glacier's melting rate, pushing it as high as 50-60cm (16-23in) a day.

https://www.bbc.com/news/world-europe-53692476

Italy resort lifts alert on melting glacier threat

An Italian Alpine resort on Sunday lifted a state of alert declared last week over fears that a chunk of glacier on the Mont Blanc mountain range might crash down on them.

Around 15 people who were evacuated can now return to their homes in Courmayeur and traffic in the Cap Ferret valley is permitted again, said a statement from town officials.

Climate change has been increasingly melting the world's glaciers, creating a new danger for the town of Courmayeur, a resort community in Italy's Aosta Valley region, near the French border.

The town was put on high alert on Wednesday as a block of ice estimated at about 500,000 cubic metres—the size of the Milan cathedral, one official said—from the Planpincieux glacier risked falling and threatening homes.

But on Sunday, town officials announced that all security measures had been lifted.

Some locals were dismissive of the closure, and said it further hit a tourism season already affected by the coronavirus measures.

But the mayor's office said again on Sunday: "The evacuation was necessary and inevitable because of the glacier risk."

While regretting what it said was the alarmist tone of some news coverage, officials insisted that the threat to the town had been real.

During a recent helicopter flypast, an AFP reporter saw a gaping chasm on the lower part of the Planpincieux, from which two cascades of water flowed towards the valley, as it hung from the mountainside like a gigantic block of grey polystyrene.

In September and October last year, the Planpincieux glacier also threatened a partial collapse, after which extra surveillance measures were put in place.

A study last year by Swiss scientists found that Alpine glaciers could shrink between 65 and 90 percent this century, depending on how effectively the world can curb greenhouse gas emissions.

https://phys.org/news/2020-08-italy-res ... hreat.html

[Whitefang]

Thanks Sub, for the data on the Alps.

https://www.independent.co.uk/news/worl ... 59266.html

The last fully intact ice shelf in the Canadian Arctic has collapsed, losing more than 40 per cent of its area in just two days at the end of July, researchers said on Thursday.
The Milne Ice Shelf is at the fringe of Ellesmere Island, in the sparsely populated northern Canadian territory of Nunavut.
“Above normal air temperatures, offshore winds and open water in front of the ice shelf are all part of the recipe for ice shelf break up,” the Canadian Ice Service said on Twitter when it announced the loss on Sunday.

Abrupt CC, imagine 40% collapse in just two days. Forget gradual melting of the GIS, this is a preview of dire happenings after the arctic sea ice is gone with the wind.

“The very small ones, we're losing them dramatically,” he said, citing researchers' reviews of satellite imagery. “You feel like you're on a sinking island chasing these features, and these are large features. It's not as if it's a little tiny patch of ice you find in your garden.”

The ice shelf collapse on Ellesmere Island also meant the loss of the northern hemisphere's last known epishelf lake, a geographic feature in which a body of freshwater is dammed by the ice shelf and floats atop ocean water.
A research camp, including instruments for measuring water flow through the ice shelf, was lost when the shelf collapsed. “It is lucky we were not on the ice shelf when this happened,” said researcher Derek Mueller of Carleton University in Ottawa, in a 2 August blog post.
Ellesmere also lost its two St. Patrick Bay ice caps this summer.

“We saw them going, like someone with terminal cancer. It was only a matter of time,” said Mark Serreze, director of the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado.

[REAL Green]

“Canada's last intact ice shelf just collapsed”
https://www.msn.com/en-us/weather/topst ... r-BB17Sbaf

“Milne Ice Shelf was Canada's last intact ice shelf — and it just collapsed…Located on the northwestern coast of Ellesmere Island in Nunavut, the Milne Ice Shelf is about 4,000 years old. Signs of the impending breakup were spotted by Adrienne White, an ice analyst at the Canadian Ice Service, Environment and Climate Change Canada (ECCC), according to WIRL. On Aug. 2, the Canadian Ice Service shared satellite images in a Tweet, reporting that "above normal air temperatures, offshore winds and open water in front of the ice shelf are all part of the recipe for ice shelf breakup." The shelf's sudden collapse was a close call for scientists studying ice loss in that precarious location, said Arctic ice researcher Derek Mueller, an associate professor in Carleton University's Department of Geography and Environmental Studies…And with the region warming at approximately two to three times the global rate — not to mention several summers of record-breaking warmth — "the Milne and other ice shelves in Canada are simply not viable any longer and will disappear in the coming decades," Copland said in the university statement. Indeed, on July 30, NASA imagery revealed that two of Ellesmere Island's giant ice caps had vanished. They had dominated the landscape for hundreds of years, but were erased by climate change in just 40 years, Live Science previously reported.”

[Subjectivist]

“Canada's last intact ice shelf just collapsed”
https://www.msn.com/en-us/weather/topst ... r-BB17Sbaf

“Milne Ice Shelf was Canada's last intact ice shelf — and it just collapsed…Located on the northwestern coast of Ellesmere Island in Nunavut, the Milne Ice Shelf is about 4,000 years old. Signs of the impending breakup were spotted by Adrienne White, an ice analyst at the Canadian Ice Service, Environment and Climate Change Canada (ECCC), according to WIRL. On Aug. 2, the Canadian Ice Service shared satellite images in a Tweet, reporting that "above normal air temperatures, offshore winds and open water in front of the ice shelf are all part of the recipe for ice shelf breakup." The shelf's sudden collapse was a close call for scientists studying ice loss in that precarious location, said Arctic ice researcher Derek Mueller, an associate professor in Carleton University's Department of Geography and Environmental Studies…And with the region warming at approximately two to three times the global rate — not to mention several summers of record-breaking warmth — "the Milne and other ice shelves in Canada are simply not viable any longer and will disappear in the coming decades," Copland said in the university statement. Indeed, on July 30, NASA imagery revealed that two of Ellesmere Island's giant ice caps had vanished. They had dominated the landscape for hundreds of years, but were erased by climate change in just 40 years, Live Science previously reported.”

For as long as I have been alive the thickest and oldest part of the Arctic Se Ice has always been gathered along the north coasts of Ellesmere/Baffin/Greenland islands. In the last four years that thick dense floating sea ice has dissipated to a much weaker ice that no longer supports Milne Ice Shelf or any of the other landfast sea ice.

[JuanP]

"Warming Greenland ice sheet passes point of no return"
https://phys.org/news/2020-08-greenland-ice-sheet.html

Apparently, Greenland's glaciers are melting faster than snow can replenish them, and this trend is expected to continue regardless of any future emissions cuts. We have crossed the Rubicon as far as Greenland's glaciers are concerned.

[dissident]

"Warming Greenland ice sheet passes point of no return"
https://phys.org/news/2020-08-greenland-ice-sheet.html

Apparently, Greenland's glaciers are melting faster than snow can replenish them, and this trend is expected to continue regardless of any future emissions cuts. We have crossed the Rubicon as far as Greenland's glaciers are concerned.

This is an actual tipping point sine one of the ways the Greenland ice sheet maintains itself is by having its top over 2 km above sea level. The temperature at this altitude is much colder than ground level. So one the ice sheet height starts to drop, the melt becomes a runaway feedback effect.

There is also a contribution to the melt by the lowering of the ice sheet albedo due to the concentration of pollutants (dust, soot) deposited over centuries and to the present day to form a dark crust. So the solar shortwave radiation is effectively converted into IR and does not get bounced back into space like with a clean ice-snow surface. This melting effect which you can see in the snow mounds that municipalities in Canada accumulate over winter road cleaning, accelerates the melting.

I suspect that the Greenland ice sheet will disappear catastrophically before 2100. Some glacier pockets will be left that reach a new equilibrium with the snow accumulation and the relative cold of the polar latitudes, but most of the ice volume will be lost.

[rockdoc123]

The Greenland ice sheet has ~ 3.1 MM Gt of ice present. Maximum loss at this point is ~250 Gt/yr.
Under that rate it would take somewhere around 12.7 K years for the ice sheet to disappear.
In order for it to completely disappear by 2100 it would require a loss of on average 39.5 K Gt/yr of ice or roughly 158 times the current rate.
Good luck with that.

[aspera]

A recent study (2020) combined 26 individual estimates of mass balance derived by tracking changes in Greenland's ice sheet volume, speed and gravity as part of the Ice Sheet Mass Balance Inter-comparison Exercise. These data suggested that the Greenland ice sheet had lost a total of 3,902 gigatons (Gt) of ice between 1992 and 2018 .

But most significantly, the rate of ice loss has increased over time from ~26 Gt/year between 1992 and 1997 to ~244 Gt/year between 2012 and 2017, peaking at ~275 Gt/year during 2007 and 2012 period.

Roughly, an order-of-magnitude change over the time period studied. Wouldn't take many more of those periods to get to your 39.5 K Gt/yr, Rocky.

Source: Shepherd, Andrew; Ivins, Erik; Rignot, Eric; Smith, Ben; van den Broeke, Michiel; Velicogna, Isabella; Whitehouse, Pippa; Briggs, Kate; Joughin, Ian; Krinner, Gerhard; Nowicki, Sophie (2020-03-12). "Mass balance of the Greenland Ice Sheet from 1992 to 2018". Nature. 579 (7798): 233–239.

DOI:10.1038/s41586-019-1855-2. ISSN: 1476-4687. PMID: 31822019.

URL: http://eprints.whiterose.ac.uk/158669/

It would be foolhardy to pick a date. But, if the increasing rate of change in these data continues, then it won't take anytime close to 12.7 K years.

[dissident]

There is no evidence for any stable equilibrium of the current Greenland ice sheet. All the observations point to the formation of a clear instability which is resulting in accelerating mass loss. To fob this off as "alarmism" is pure denialist BS. The Greenland ice sheet will not melt down to 1.5 km and then stop for a few millenia. It will keep on melting faster and faster since it will be losing both albedo and surface cold temperatures to accumulate snow to maintain its now non-viable equilibrium.

There are no stability minima on the way to what amounts to full melt. If it is melting with its current height, it will keep melting and faster at lower heights. I forgot to add that this accelerating melt will also contribute to direct mass loss through down slope flow to the sea. There are no ice dams keeping it back.

[Newfie]

Thanks for the discussion guys. Very interesting, if disheartening.

[jawagord]

Thanks for the discussion guys. Very interesting, if disheartening.

The only thing disheartening is we are doing this handwringing over Greenland ice melting again. This study references the ice loss data from another study. If we use the average rate of ice loss from the referenced study (222 giga tonnes per year) how long will it take for the 2,900,000 giga tonnes of Greenland ice to disappear? It will take 13,000 years for Greenland ice to melt, crises averted, your welcome again, will post same again next year.


The ice sheet was close to a state of balance in the 1990s, but annual losses have risen since then, peaking at 345 ± 66 billion tonnes per year in 2011. In all, Greenland lost 3,902 ± 342 billion tonnes of ice between 1992 and 2018, causing the mean sea level to rise by 10.8 ± 0.9 millimetres. Using three regional climate models, we show that the reduced surface mass balance has driven 1,964 ± 565 billion tonnes (50.3 per cent) of the ice loss owing to increased meltwater runoff. The remaining 1,938 ± 541 billion tonnes (49.7 per cent) of ice loss was due to increased glacier dynamical imbalance, which rose from 46 ± 37 billion tonnes per year in the 1990s to 87 ± 25 billion tonnes per year since then. The total rate of ice loss slowed to 222 ± 30 billion tonnes per year between 2013 and 2017, on average, as atmospheric circulation favoured cooler conditions15 and ocean temperatures fell at the terminus of Jakobshavn Isbræ16. Cumulative ice losses from Greenland as a whole have been close to the rates predicted by the Intergovernmental Panel on Climate Change for their high-end climate warming scenario17, which forecast an additional 70 to 130 millimetres of global sea-level rise by 2100 compared with their central estimate.

https://www.nature.com/articles/s41586-019-1855-2


https://web.viu.ca/earle/geol305/The%20 ... 0Sheet.pdf

[rockdoc123]

Roughly, an order-of-magnitude change over the time period studied. Wouldn't take many more of those periods to get to your 39.5 K Gt/yr, Rocky.

OK, show us the math. Show us a rate of change plot and how that makes any sense whatsoever with even the ridiculously unreasonable RCP 8.5. Waving your hands and saying….well it could happen without being able to explain how is referred to as “magical thinking”.

But, if the increasing rate of change in these data continues, then it won't take anytime close to 12.7 K years.

And if the rate of change slows or reverses (which it did prior to the seventies) then what?

There are no stability minima on the way to what amounts to full melt. If it is melting with its current height, it will keep melting and faster at lower heights. I forgot to add that this accelerating melt will also contribute to direct mass loss through down slope flow to the sea. There are no ice dams keeping it back.

Do you know anything about the physiography of the Greenland ice sheet? The largest volume of ice is contained in a central bowl where gravity will not support your theory of increased mass loss due to downslope wasting. That ice will have to melt as a consequence of air temperature (or increased heat flow in certain parts of Greenland).

Here is a paper from a couple of years ago that looks at the pre-satellite era data and merges it with the eighties onward instrumental data.

Connoly, R and Soon, W, 2017. Re-calibration of Arctic sea ice extent datasets using Arctic surface air temperature records. Hydrological Sciences Journal, 62:8, 1317-1340, DOI: 10.1080/02626667.2017.1324974

A new seasonal and annual dataset describing Arctic sea ice extents for 1901–2015 was constructed by individually re-calibrating sea ice data sources from the three Arctic regions (North American, Nordic and Siberian) using the corresponding surface air temperature trends for the pre-satellite era (1901–1978), so that the strong relationship between seasonal sea ice extent and surface air temperature observed for the satellite era (1979-present) also applies to the pre-satellite era. According to this new dataset, the recent period of Arctic sea ice retreat since the 1970s followed a period of sea ice growth after the mid-1940s, which in turn followed a period of sea ice retreat after the 1910s. Arctic sea ice is a key component of the Arctic hydrological cycle, through both its freshwater storage role and its influence on oceanic and atmospheric circulation. Therefore, these new insights have significance for our understanding of Arctic hydrology.

Showing just the satellite era data does not describe what is actually happening long term with respect to Greenland.

[aspera]

OK, show us the math. Show us a rate of change plot and how that makes any sense whatsoever with even the ridiculously unreasonable RCP 8.5. Waving your hands and saying….well it could happen without being able to explain how is referred to as “magical thinking”.

I guess we could do that Rock. Meantime, you could thoroughly read the articles cited. And maybe take a math refresher by viewing Bartlett's lecture?

And I'll check out “magical thinking” if you'll review "motivated reasoning."

[sparky]

.
the polar melt should dramatically increase when the local weather switch from snow to rain
with no rain , the cold resulting from the melt remain and limit the warming
rain promote melting very much so and remove the melt water

[Whitefang]

https://youtu.be/FRs4kIthJ9k

Oldy from december 2014, Jim White on abrupt CC. AGU San Fran fall meeting.
At 21 minutes: rate of inferred warming Northern Greenland 5 to 10 degrees Celcius per year. 1000 times current rate.
The only thing causing this, that these scientists can come up with is a phase change on the arctic ocean.
The GIS cannot exist without sea ice present, SST will skyrocket, look at the Russian side this year.
Millenia for complete melt? No way.
Centuries? Unlikely but hopefully.
Decades? Possible, maybe, we'll see.....

[rockdoc123]

Oldy from december 2014, Jim White on abrupt CC. AGU San Fran fall meeting.
At 21 minutes: rate of inferred warming Northern Greenland 5 to 10 degrees Celcius per year. 1000 times current rate.

well that amount of surface warming is in someone's imagination as it isn't supported by actual data

Mikkelsen, T. B., et al, 2018. Influence of temperature fluctuations on equilibrium ice sheet volume. The Cryosphere, supplemental material, 12, pp 39-47

[Tanada]

More and pictures at link below quote.

Ghosts of Glaciers Past Hint at Future Climate Challenges
December 9, 2020

In order to predict how glaciers will respond to climate change in the future, scientists first need to understand how they’ve responded in the past. A team of scientists in the Cosmogenic Nuclide Lab at Columbia University’s Lamont-Doherty Earth Observatory have taken on the challenge by studying glacial remains all around the world, from Patagonia to the Arctic.

One of the most interesting questions that the team is investigating is whether glaciers in different latitudes and hemispheres expand and retreat at similar times, said Mike Kaplan, a Lamont research professor who works in the Cosmogenic Nuclide Lab. Prior to human influence, there are strong indications that climate patterns affecting the southern hemisphere glaciers were out of step with those in the north, said Kaplan, and understanding why could help project the effects of modern climate change.

Reconstructing the Past

Studying glacier retreat that happened more than 11,000 years ago can be tricky.

To do so, the team uses a method called cosmogenic dating. For the method to work, scientists must first identify a well-preserved mass of rocks or sediment left behind by a shrinking glacier that is called a moraine. Then, scientists chip away sections of the boulders in the moraine to take back to the lab, where they can be analyzed for the presence of beryllium-10, an isotope that is formed from cosmic rays in Earth’s atmosphere.

Counting atoms of beryllium-10 on the rocks’ surface helps scientists to determine exactly how long the rock was exposed to the atmosphere, or how long ago it was uncovered by ice. This helps to create a timeline for glaciers expanding and retreating, and ultimately, reveals how the climate changed over time. During the last 10 years, researchers with the Cosmogenic Nuclide Lab have used cosmogenic dating to document the ghosts of glaciers on more than five continents, including Europe, South America, Antarctica, Australia, and North America.

“Most of our knowledge about temperature changes on Earth come from ice cores in Antarctica and in Greenland,” said climate geoscientist Joerg Schaefer, who leads the lab. “But those are both in very extreme positions — they are both polar. In between, it’s really hard to find reliable, accurate thermometers, and mountain glaciers basically fill that gap.”

For the last several years, the group has mapped glacial remains of the Patagonia Ice Sheet near the Strait of Magellan area in southern Patagonia. There, research led by graduate student Carly Peltier turned up evidence that, during the last glacial period, the Magellan ice lobe would have reached a position more than 65 kilometers further east than previously reported, providing important new data for paleoclimatic reconstructions. Retreat from this maximum glacier position began slowly by 25,000 years ago, with the ice continuing to stabilize repeatedly until about 18,000 years ago, which was then followed by rapid, irreversible retreat. By 16,000 years ago, the Patagonia Ice Sheet had more or less disappeared in southernmost South America.

With support from the National Science Foundation, the team most recently went back to South America in November 2019, this time to study and compare historic glacier retreat more in the central Andes mountain range over the last 11,000 years. The idea is to determine whether glaciers at different latitudes experienced similar expansions and retreats over this same time period. For the latest study, Kaplan and three Chilean colleagues traveled by horse for nearly two days to sample a remote site in the central Andes. There, they collected more than 35 moraine specimens to bring back to the lab, where they will analyze their chemical makeup and compare them to specimens the lab group have taken over recent years in the southern Andes in Chile. COVID-19 delayed the analysis of the newest samples due to the closing and then phased re-opening of labs this year, but Kaplan hopes to start soon.

“With this project, we’re moving north slightly in South America to see if the same patterns and changes that we’ve seen over the last 10 or 15 years [of our group’s research] continue as you go north,” said Kaplan. “One of the things we’re trying to understand is what caused glacier variability in a natural sense before human effects on the climate system.”

Painting a Picture of the Future

Over the last few decades, the impact of human activities on climate change and ultimately, glacier retreat, is undeniable, according to Kaplan and Schaefer. Activities such as deforestation and the burning of coal and other fossil fuels led to an increase of carbon dioxide into the atmosphere, where it hugs the planet like a scarf, leading to a steady rise in global temperatures.

“From our research, the most overwhelming result—unfortunately, I wish it were different—is that whenever carbon dioxide changed naturally, glaciers all over the place in both hemispheres, did basically the same thing,” said Schaefer. “They just retreated and followed the carbon dioxide curve. That is the about the last thing you want to find out, given what the carbon dioxide curve looks like.”

Still, Schaefer and Kaplan hope that moraine sampling projects like the ones in Patagonia and the central Andes will help shed light on what to expect in terms of river and sea level rise as a result of climate change. Other scientists from the Cosmogenic Nuclide Lab are sampling moraines in Greenland, Alaska, and Antarctica. All together, they hope to paint a picture of what the planet will look like in 30 years, in order to aid in management practices.

“Glaciers have inertia, so even if we found a miracle and could stabilize temperatures tomorrow, many of the glaciers would keep retreating for at least 20 or 30 years because they already have so much warmth in them,” said Schaefer. “So now, we need to focus on how big these rivers that are glacier-fed will be, and how we will all be impacted by this change in glacial melt supply in the next 10 to 20 years.”

Linky