[Professor Beckwith has been on a YouTube from Canada Joined Sep 16, 2011 46.4K subscribers 1,626 videos]
Hello everybody. My name is Beckwith, Paul Beckwith, and I'm going to talk about a new peer-reviewed paper which is based on many many years of ice coring data off a region of East Antarctica. And we know that, as warming is accelerating, we're getting all kinds of nonlinear, very, very fast and concerning effects on the climate system. For example, the collapse of Antarctic sea ice in the last, well, since 2015, has surprised a lot of people.
And this study actually confirms some of the feedback mechanisms that are responsible for causing tremendous amounts of Antarctic ice melt, ice on ice shelves, acceleration of onland glaciers, increased calving, which is all greatly increasing sea level rise.
So, basically what this new paper looks at is from the sediment cores of this region of Antarctica, it looks at when we've had major ice shelf collapses as we went out of the last glacial maximum about 21,000 years ago towards the present. So there's been periods of time when there's been these rapid meltwater pulses, rapid rises in sea level rise and periods of time when we've had absolutely tremendous collapses of the of the ice shelves, the ice sheets.
1.55
One of those times was about 9,000 years ago. And this study very carefully comes up with the conclusion that one of the principal causes or enablers of feedbacks, cascading feedbacks causing ice collapse and melt in Antarctica is when you get a lot of melting, you get a freshwater layer on the surface of the ocean. And that fresh water, very cold fresh water is lighter than the saltier water. So it floats on top.
Soyou get a stratification of the ocean off the coastal regions. So the water that comes to the shelf the circumpolar deep water instead of instead of having vertical movement and vertical mixing because it's constrained by the stratification, it basically finds all of the creasses and and fjords and valleys and it goes very deep under the Antarctic ice and it's very warm water and it melts the ice from below.
3.03
I mean, clearly the temperatures on the surface of Antarctica are well below zero. So with climate change, if they warm up a few degrees, it's still well below zero. Antarctica is not getting so much melt from the surface, but it's all from underneath. And it's the infiltration of this circumpolar deep water, which is enhanced by other regions around Antarctica from the additional melt.
So this is a very important feedback and that's what this new paper is all about. It's Japanese it's led by Japanese polar scientists and let's look at some of these details now. So Antarctic ice shelf collapse in the holocene driven by meltwater release feedbacks or these cascading feedbacks. So let's first look at the press.
this so this is a press article. Antarctic ancient Antarctic ice melt triggered a chain reaction 9,000 years ago. So this is Scitec Daily and this just came out a few days ago, November 7th, 2025. So this is an example of a a cing device. You put it vertically on the seafloor. It cores down and is filled with sediment and it brings up a chunk of this a cylinder of this sediment and you can date it back using isotopic dating etc. and see the changes of this material in the core tell us what happened at periods in the past.
4.44
So the discovery is that early holocene ice loss in east Antarctica was driven by oceanic feedback loops connecting distant regions. So we got meltwater discharge and that altered the ocean layers. It caused great stratification because the fresh water is lighter floats on top of the saltier water. So the warmer deep water instead of breaking the surface it kept heading inland inwards into the fjords etc around Antarctica because it couldn't go upward. So it intruded beneath the ice shelves and it hastened their collapse.
So these self-reinforcing processes mirror the dynamics now observed in West Antarctica. So modern warming is likely to trigger widespread ice retreat. So this new study found out that the East Antarctic ice sheet underwent a massive retreat about 9,000 years ago and that was driven by powerful feedback between the melting ice in other areas and the stratification and then the shifting of the ocean currents. So the circumpolar deep water could go right underneath the ice.
So it's a national institute of polar research Japanese institute and graduate university for advanced studies. So they teamed up. They discovered that warm deep water flowed toward East Antarctica's coast causing the ice shelves to melt quickly and collapse. As the shelves broke apart, then the inland ice began to flow more rapidly towards the ocean, like taking the cork off of a bottle. 6.35
The Antarctic melting that created that stratification layer of fresh water is not confined to a single region. It spreads across connected areas through ocean circulation. So, it's called a cascading positive feedback. So meltwater in one area can accelerate melting elsewhere in this cascading feedback effect. And that probably is why we've got long-term instability in the Antarctic ice. So this is 9,000 years ago. Well, 20,000 years ago, last glacial maximum sea levels were at this level.That was the peak of the cold period in the last glaciation.
And then as the ice melted, we're looking at 9, years ago sea level was about here. And what they found is that the warm deep water because of the melt water from the ice sheet there was stratification fresh water on top. So the warm deep water couldn't come up. It had to come right up underneath along the coast and it etched away at the ice causing an acceleration of the ice melt. Therefore, ice shelf collapse. When the ice shelf collapse is taking the pressure, the buffering pressure off. So, we got an acceleration of the ice discharge off the continent. Okay. So, all of these chain reaction effects in progress.
7.58
The East Antarctic ice sheet holds over half of Earth's fresh water. It's now losing ice rapidly along parts of the coast. So, so this paper and study allows us to understand better how these vast ice sheets in Antarctica reacted to earlier periods of warming so that we can figure out what they're doing now and in the near term and far-term future.
So the researchers looked at the marine sediment cores taken from this bay. and they analyzed these and the sediments were basically gathered from numerous Japanese Antarctic research expeditions from 1980 to 2023 over, well that's over a 45 year almost time period.
They had recent samples from an ice breaker and that allows us to look back into the past. Well worth watching this video. They looked at beryllium isotope ratios 10 Beryllium to 9 Beryllium. They used sediment sediment and the sediment analysis micro paleontological analysis geochemical methods to reconstruct conditions in the bay over time.
**********
If this is too dense for you, here is an EZ version of the science:
EZ vlog Beckwith climate science lecture in previous post shortened to 2 min simple video- WATCH & READ at Heating Planet blog
**********
9.12
So what they found is that around 9,000 years ago, the warm circumpolar deep water intensified in the region and that led to the collapse of the floating ice shelves. Without those shelves acting as stabilizing barriers, the inland ice surged more quickly into the sea and sea level rise rapidly rose. So all of these feedbacks are occurring and the they also did high resolution ocean model simulation and those found that melt water from other parts of Antarctica including the Ross ice shelf spread across the southern ocean near the coastlines. So it freshened the surface layer. It strengthened the vertical stratification so it kept that circumpolar deep water the warm water from breaking the surface. It stayed it stayed deep down and went underneath the fresh layer water and it impinged far into the nooks and crannies of the Antarctic coast, taking out the ice.
So stronger stratification limited the upward mixing of cold surface water, allowing warm deep water to flow more easily towards the East Antarctic's continental shell.
10.27
So it's a reinforcing cycle. It's a cascading feedback. You get more and more melt water, you get more and more stratification. So there's more warm water inflow causing further melting of the ice sheet. So this cascading mechanism implies that ice loss in one part of Antarctica can set up or speed up melting in distant regions through these interconnected ocean processes. So this is compelling evidence that the Antarctic ice sheet today is vulnerable to widespread self-reinforcing melting as the planet warms. Okay, so modern observations show that parts of West Antarctica like the Thwaites and Pine Island glaciers are already rapidly retreating as warm deep water erodes their bases.
So this can spread into other regions. So it was a very extensive study. and we can ignore it at our peril. and then this is the region, the Lutzo home bay up here where the research took place. So there's a good Wikipedia page on this whole particular region of Antarctic, sort of the history and how things have changed, the different geography of the region. And here's a map here. So, it's up in this region up here.
11.55
And this is the Hokkaida University article. There's more details about how the Antarctic ice melt triggered further melting cascading feedbacks 9,000 years ago. So, they talked about some more details that weren't in the article about the research work and what they're studying and how they're looking at it. This is a diagram I showed you already. Okay, so let's go to the peer-reviewed paper. Okay, so this is open source. It was just published online a week ago within the last week.
So the circumpolar deep water inflow onto Antarctic's continental shelves is a key driver of accelerated Antarctic ice sheet mass loss. There's no surprisethere. I mean, we're getting mass loss from Antarctica. We know it's not from surface melt, right? If we go from -40 Celsius through global warming to minus 35 Celsius, it's still not going to melt. It's still way below the melting point.
But it's the water underneath the ice shelves. It's undercutting it. And we've got this new- we've got this feedback confirmed by data by the paleo data that there's cascading feedback effects to take out the ice.
13.25
Okay. So the mechanisms driving enhanced inflow and the resultant impact on large scale ice sheet retreat events, it's still not fully understood. So this paper is key to showing what's going on the mechanisms that are causing the great increase in loss of ice from Antarctica. So they use marine sediment cores from Lutzo home bay eastAntarctica. They analyzed the burillium isotopes in the sediments and other proxies.
They so they basically showed that ice sheet collapse and the simultaneous inland ice sheet thinning speeding up of inland ice sheets and thinning and calving about 9,000 years ago were associated with enhanced circumpolar deep water inflow and there and and sea level rise. Okay.
So they combined climate modeling with high-resolution ocean data and simulations and they found that freshwater discharge from nearby Antarctic sectors into the southern ocean probably enhanced the regional inflow into the submarine troughs in the bay between 10,000 and 9,000 years ago.
The feedback loop has melt water from rapidly retreating Antarctic sector since the last glacial maximum. So we get more fresh water around the coast of Antarctica. We get increased or enhanced stratification.
Therefore, the circumpolar deep water can't go upwards and break the surface. So it stays deep and it in there's incursions onto adjacent shelves underneath the ice. So the meltwater feedback triggers further ice instability enhances dynamic inland ice discharge. So this is it all cascades and then rinse and repeat basically.
Now the Antarctic ice sheet is of course it's the Earth's largest continental ice mass, holds a freshwater volume equivalent to 58 m of global sea level rise just in Antarctic ice sheet alone.Even minor volume changes substantially affect global sea level r and climate. Okay, so recent observations and high resolution simulations reveal that warm circumpolar deep water CDW from offshore is increasing melt under the floating ice shelves. So we're getting a negative mass balance. There's less ice forming than there is calving, primarily in West Antarctica, but also in parts of East Antarctica.
16.10
So changes in the ocean temperature associated with the increased inflow of circumpolar deep water onto the Antarctic continental shelf is pivotal in enhancing basal ice sheet melting. Ice sheet melting at the bottom of the ice thinning of the ice the cork or buttress effect is reduced. So we get further retreat via enhanced flow and dynamic thinning processes of the inland ice sheet. So as the inland ice sheet speeds up flow and to the coasts and calves, it gets thinner. there's a potential for largecale ice melt and that would profoundly-
so so we our our ability to project future climate and Antarctic ice sheet mass balance shifts is problematic. We're always underestimating the speed at which things are happening. So the deglaciation of the Antarctic ice sheet since the last glacial maximum which is about 21,000 years ago, it says 20 here, provides the most recent example of consequences of ocean ice sheet interactions.
17.17
Okay, so this is Antarctica. This is the region. This box here is in this picture. Here's the home bay. you've got the circumpolar deep water here. And if you do a magnification of this region here, you can see where the warm circumpolar deep water is coming right in undercutting the ice underneath causing the greatly accelerated melt. Okay. and this is the actual core. So as you go down in thecore this is the core depth in centimeters. As you go deeper down you go back in time. This is a region here, this is this is a region where so the sediments are all the lithography the sediments are all different in the core and right here this is associated with the period when there was massive ice collapse.
18.17
So starting about 9,320 years ago with a bit of error uncertainty in that date. and then boom the we had the ice shelf collapse and ice sheet thinning inland. So all of those things kind of match up and there's data taken from ice cores inside inland and so on and they match up all the dates to try to generate a picture of what happened and so we basically saw an ice shelf collapse and that was followed by inland ice sheet thinning.
Okay. so that there was a warm circumpolar deep water inflow occurring. and so they go into all the details but I think I've told you some of the key findings of this paper. this is the coastline and modeled temperatures and so on 9,000 years ago. and basically we have a cascading positive feedback.
So the study shows that melt water along Antarctica's oceanic margin leads to increased circumpolar deep water inflow towards the Antarctic ice sheet. So melt water along the ocean margins causes the stratification of the water. So the circumpolar deep water can't move upwards through the density barrier. So it goes inland towards the Antarctic ice sheet. It causes subsequent ice shelf collapse. And when the ice shelf collapse that then leads to the ice sheet which is grounded on bedrock above sea level that flows faster calvess more and basically thins.
20.04
So it leads to a large melting of the ice. Previous studies have proposed that there may have been a southertherly shift of the of the southern hemisphere westerly winds that was enhanced by regional sea level forcing grounding line retreat and increasing ocean heat flux. So this study only looked at the one particular region and suggested that ice sheet retreat in remote regions can propagate to other regions via the formation of this large stratification zone around the continent.Okay.
Okay, so the Antarctic circumpolar current, if it's carrying fresh water, that fresh water bills around the continent of Antarctica, then the circumpolar deep water can just impinge further and greatly accelerate the melt rate.
So, so those are the key findings of this paper. So, what does that mean? The bottom line is that Antarctic ice melt will likely continue to accelerate and continue to surprise with Calving events and so on. And part of it is due to this circumpolar deep water cascading feedback effect which is one of the key factors that's taking out the Antarctic sea ice. Thank you for listening. Please go to paulbeckwith.net Thanks again and bye for now.
No comments:
Post a Comment