The Increasingly Fragile Pine Island Glacier Just Calved Again

The point where the Pine Island and Thwaites glaciers meet the sea serve as a back-stop restraining most of the great ice flows of West Antarctica. If those backstops were to fail, ocean water would flood inland along a reverse slope and generate a massive and swift out-rush of ice that would ultimately raise the world’s oceans by about 3 meters. And, lately, the evidence is mounting that the backstops are failing.

At Thwaites, just south of the neighboring Pine Island Glacier (PIG), recent research found that the ocean was flooding inland beneath that enormous ice sheet at a rate of up to 400 meters per year. But to the north, there is indication of trouble at the ice surface.

Back to Back Calving Events

Just last September, a massive 100 square mile ice berg calved off the Pine Island Glacier. The event was significant in that it marked the first major retreat of the glacial front in the face of an advancing ocean. Pine Island had already sped up. But the calving face withdrawal inland appeared to mark a new phase for the large glacier.

(Sentinel 1 satellite observations show a rapidly moving Pine Island Glacier calving off another large ice berg. Meanwhile, considerable damage appears to have been done to the glacial front.)

Now, just 7 months later, PIG is calving again. A large, approximately 6 kilometer long, 1 kilometer wide, chunk appears to have broken off into the Southern Ocean and shattered. Meanwhile, to the north and south along the glacial front, rifts appear to have formed.

This recent calving event is significant for a number of reasons. The first is that it’s happening just months after a recent large break-off during 2017. Other recent calving events at Pine Island occurred during 2001, 2007, and 2013. The present 2017-2018 events are back-to-back. The second reason is that the splintering appears to indicate a more fragile ice face. An impression reinforced by the concordant formation of rifts spreading away from the calving zone. The third is that the satellite imagery suggests Pine Island Glacier is moving quite rapidly (Recently, this rate of motion has been 1-2 km per year. However, it’s reasonable to question whether the glacier is continuing to speed up).

Conditions in Context

Present global warming due to fossil fuel burning has now forced the world into a range of temperatures between 1.0 and 1.21 degrees Celsius above 1880s averages. This boundary is similar to that of the lower range of the Eemian 120,000 years ago when oceans where 10-20 feet higher than they are today.

(The tall ice cliffs composing the Pine Island Glacial front have become increasingly fragile and fast moving as they enter the warming Southern Ocean and as that warming water continues to invade inland. Image source: Commons, Pine Island Glacier Calving Front, NASA.)

Under present greenhouse gas forcing and planned emissions, additional warming is in store. Climate models produced by Dr. Michael E Mann indicate that we are likely to hit the 1.5 C global temperature boundary some time between 2027 and 2031 on the current emissions pathway. This predicted warming is significant because analysis of past climates appears to indicate a risk of more rapid rates of sea level rise when global temperatures rise to a range between 1.5 to 2.5 C above past base line averages (see meltwater pulse 1 A).

Since the 1990s, the global rate of sea level rise has proceeded at roughly 3.3 mm per year with an apparent acceleration to around 3.6 to 4.1 mm per year during the 2010 to present time period. Given observed ice sheet instability in West Antarctica, in East Antartica, and in Greenland, there is a serious risk that this rate of rise will continue to accelerate over the coming years and decades. The key question of concern is how much and how soon.


Gigantic Iceberg Disintegrates as Concern Grows Over Glacier Stability, Sea Level Rise

The stability of a key Antarctic glacier appears to have taken a turn for the worse as a large iceberg that broke off during September has swiftly shattered. Meanwhile, scientists are concerned that the rate of sea level rise could further accelerate in a world forced to rapidly warm by human fossil fuel burning.

(Iceberg drifting away from the Pine Island Glacier rapidly shatters. Image source: European Space Agency.)

This week, a large iceberg that recently calved from West Antarctica’s Pine Island Glacier rapidly and unexpectedly disintegrated as it drifted away from the frozen continent. The iceberg, which covers 103 square miles, was predicted to drift out into the Southern Ocean before breaking up. But just a little more than two months after calving in September, the massive chunk of ice is already falling apart.

The break-off and disintegration of this large berg has caused Pine Island Glacier’s ice front to significantly retreat. From 1947 up until about 2015, the glacier’s leading edge had remained relatively stable despite significant thinning as warmer water began to cut beneath it. But since 2015, this key West Antarctic glacier has begun to rapidly withdraw. And it now dumps 45 billion tons of ice into the world ocean each year.

(Glaciers like Pine Island balance on a geological razor’s edge. Because they sit on a reverse slope, it only takes a relatively moderate amount of ocean warming to precipitate a rapid collapse. These collapses have happened numerous times in the past when the Earth warmed. Now, human-forced climate change is driving a similar process that is threatening the world’s coastal cities. Image source: Antarctic Glaciers.)

The present rate of melt is enough to raise sea levels by around 1 millimeter per year. That’s not too alarming. But there’s concern that Pine Island Glacier will speed up, dump more ice into the ocean and lift seas by a faster and faster rate.

Pine Island Glacier and its sister glacier Thwaites together contain enough water to raise seas by around 3-7 feet. The glacier sits on a reverse slope that allows more water to flood inland, exposing higher and less stable ice cliffs as the glacier melts inland. If the glacier melts too far back and the ice cliffs grow too high, they could rapidly collapse — spilling a very large volume of ice into the ocean over a rather brief period of time. As a result, scientists are very concerned that Pine Island could swiftly destabilize and push the world’s oceans significantly higher during the coming years and decades.

No one is presently predicting an immediate catastrophe coming from the melt of glaciers like Pine Island. However, though seemingly stable and slow moving, glacial stability can change quite rapidly. Already, sea level rise due to melt from places like Greenland and Antarctica is threatening many low-lying communities and nations around the world. So the issue is one of present and growing crisis. And there is very real risk that the next few decades could see considerable further acceleration of Antarctica’s glaciers as a result of human-forced warming due to fossil fuel burning.

Dr Robert Larter, a marine geophysicist at British Antarctic Survey, who has researched Pine Island Glacier in his work with the Alfred Wegener Institute, recently noted to

“If the ice shelf continues to thin and the ice front continues to retreat, its buttressing effect on PIG will diminish, which is likely to lead to further dynamic thinning and retreat of the glacier. PIG already makes the largest contribution to  of any single Antarctic glacier and the fact that its bed increases in depth upstream for more than 200 km means there is the possibility of runway retreat that would result in an even bigger contribution to sea level.”


Hat tip to Colorado Bob

Hat tip to Erik Friedrickson

Half a Kilometer of Ice Gone in Just 7 Years — West Antarctica’s Smith Glacier Points To Nightmare Melt Scenario

The nightmare global warming melt scenario for West Antarctica goes something like this —

First, ocean waters warmed by climate change approach the vast frozen continent. Melt already running out from the continent forms a fresh water lens that pushes these warmer waters toward the ocean bottom. The waters then get caught up in currents surrounding Antarctica that draw them in toward numerous submerged glacial faces. The added ocean heat combines with falling melting points at depth to produce rapid melt along sea fronting glacier bases. Since many of these glaciers sit on below sea level beds that slope downward toward the interior of Antarctica, a small amount of initial melt sets off an inland flood of these warmer waters that then produces a cascade of melt. This glacial melt chain reaction ultimately generates a Heinrich Event in which armadas of icebergs burst out from Antarctica — forcing global sea levels to rapidly rise.

This is Why We Worry So Much About Multi-Meter Sea Level Rise

Ultimately, seas rising by multiple meters this Century are a very real possibility under current warming scenarios in which such a series of cascading melt events occurs in West Antarctica.

(NASA video narrated by Dr. Eric Rignot, a prominent glacial scientist. Concerns about the origin of melt water pulse 1A during the end of the last ice age led to investigation of large Antarctic melt pulses as a potential source. Subsequent investigation identified melt vulnerabilities at the bases of large sea fronting glaciers in West Antarctica to present and predicted levels of ocean warming. At issue was the fact that bottom waters were warming and that because many glaciers rested on sea beds that sloped inland, melt rates had the potential to very rapidly accelerate.)

Though such a nightmare melt scenario was recently theoretical, it represented a very real potential near-future event as global temperatures rose into the 1-2 degrees Celsius above 1880s range during recent years. For times in the geological past around 115,000 years ago also produced large glacial melt pulses and related sea level rises of 15-25 feet during periods of similar warmth.

However, direct evidence of such a powerful melt dynamic had not yet been directly observed in Antarctica’s glaciers. Fresh water lenses were developing, rates of glacial loss were quickening. Basal melt rates looked bad. But the kind of tremendous losses necessary to produce rapid sea level rise were not yet fully in evidence.

Smith Glacier Loses Half a Kilometer of Ice in Seven Years

That situation changed during recent weeks when two scientific papers broke the news that some of West Antarctica’s glaciers had lost upwards of a half a kilometer of ice thickness due to contact with warm ocean waters over the past decade.

The studies, entitled Rapid Submarine Ice Melting in the Grounding Zones of Ice Shelves in West Antarctica and Grounding Line Retreat of Pope, Smith and Kohler Glaciers took a comprehensive look at both surface and underside melt of three major west Antarctic glaciers near the Thwaites and Pine Island Glacier systems. These glaciers included Pope, Smith and Kohler — which have seen increasing instability and rates of seaward movement during recent years. Using multiple instruments, the scientists found evidence of massive ice losses and speeding ice flows.


(Surface velocity of Kohler, Smith and Pope Glaciers provided by NASA. More rapid seaward movement of glaciers = faster rates of sea level rise.)

The losses occurred at a time when an influx of warmer water (warming circumpolar deep water) was heating the ice shelves and grounding lines buttressing these three partially submerged glaciers. This warming was found to have produced melt along the grounding zones of these glaciers in the range of 300 to 490 meters from 2002 to 2009. In other words, about 1/3 to 1/2 a kilometer of ice thickness at the grounding line was lost in just seven years. Melted away from below by warming deep ocean conditions at the rate of up to 70 meters or around 230 feet per annum.

The studies found that the Pope and Kohler glaciers, which rested on up-sloping sea beds, produced slower rates of melt. While Smith, which sat on a retrograde (or down-sloping bed) produced very rapid rates of melt. According to the Nature study:

We attribute the different evolution of Smith Glacier to the retreat of its grounding line deeper allowing warmer waters to flood its grounding zone, and increasing ocean thermal forcing due to the lowering of the in situ melting point; as well as to the exposure of the glacier bottom to ocean water as the grounding line retreated rapidly.

A Context of Worsening Risks

Unfortunately, numerous glaciers in the Amundsen Sea region including parts of the Thwaites system and the massive Pine Island Glacier also sit on retrograde slopes. These glaciers are seeing increasing fluxes of warm, deep water. By themselves they represent multiple feet of sea level rise (4-7 feet). Furthermore, Thwaites and Pine Island Glacier currently buttress a number of massive inland glaciers that become vulnerable to melt if inland-running retrograde slopes become flooded with warming ocean waters.

The very real concern is that Smith Glacier serves as a harbinger for near future events to come. As a result, coastal regions around the world are now under a heightened risk of swiftly rising seas and rapid coastal inundation over the coming years and decades.


Rapid Submarine Ice Melting in the Grounding Zones of Ice Shelves in West Antarctica

Grounding Line Retreat of Pope, Smith and Kholer Glaciers

Heinrich Event

Dr. Eric Rignot

Studies Offer Glimpse of Melting Under Antarctic Glaciers

Thwaites Glacier

Pine Island Glacier

Hat tip to Zack Labe

Hat tip to Miles h

Doomed Pine Island Glacier Releases Guam-Sized Iceberg into Southern Ocean

Science has confirmed it. Human-caused warming is killing Antarctica’s massive Pine Island Glacier (PIG). And this week’s release of a chunk of ice larger than Guam into the southern ocean is just one of the many major losses that will occur as part of what is now an inevitable demise of one of the world’s greatest glaciers.

(CNN provides this stunning NASA imagery sequence of the break-off of B-31, a 12×24 mile iceberg from the, now doomed, Pine Island Glacier.)

Heat-Charged Blow to The Soft Underbelly of Antarctic Ice Shelves

As human greenhouse gas emissions caused the world’s oceans to warm, upwelling currents delivered a portion of that heat to the continental shelf zone surrounding Antarctica. A fortress of ice, numerous glacial ice shelves thrust out from this frozen land and drove deep into the sea floor. Ocean-fronting glaciers featured submerged sections hundreds of feet below the sea surface.

The warming currents encountered these massive ice faces, eroding their undersides and providing pathways for ocean waters to invade many miles beneath the glaciers. These invasions subjected the vulnerable ice shelves not only to the heat forcing of an ever-warming ocean, but also to wave and tidal stresses. The reduction in grounding and the constant variable stresses set the glaciers into a rapid seaward motion.

Antarctica’s most vulnerable glaciers lie along its western out-thrust. Two, Thwaites and the Pine Island Glacier, have recently seen very rapid increases in forward speed. Of these, the Pine Island Glacier, according to a recent study, is undergoing the process of an irreversible collapse. What this means is that the glacier’s speed of forward motion is now too great to be halted. Inevitably, even if the climate were to cool, the entire giant glacier will be launched into the world’s oceans where it will entirely melt out.

PIG basal melt

(Pine Island Glacier underwater melt dynamics. Image source: Nature)

Guam-Sized Chunk of Ice to be One of Many

The Pine Island Glacier is massive, covering a total area of 68,000 square miles and, in some locations, rising to over 2,000 feet in height. It represents 10% of all the ice in the West Antarctic Ice Sheet, holding enough liquid water to raise sea levels by between 1 and 2.5 feet all on its own. And the now destabilized PIG is bound to put added stresses on the adjacent Thwaites glacier together with almost the entire West Antarctic ice system.

Over recent years, PIG’s forward speed has accelerated. Increasing forward velocity by 73 percent from 1974 to 2007. Surveys made since that time show an even more rapid pace. By January of this year, studies were finding that PIG had entered a sate of irreversible collapse. So it is little wonder that enormous chunks of ice are breaking off from this massive glacier and drifting on out into the Southern Ocean.

As of early this week, the immense ice island dubbed B31 measuring 12×24 miles in size (nearly 290 square miles), slid off its temporary grounding on the sea bottom and began its journey out into the Southern Ocean. There it will remain for years, plaguing the world’s shipping lanes as it slowly disintegrates into a flotilla of icebergs. It is just the most recent event in the now ongoing decline of PIG. And we can expect many, many more major ice releases as this vast Antarctic glacier continues its dive to the sea.


Humongous Iceberg Slowly Drifts Away From Antarctica

Scientists: Warming Ocean, Upwelling Make an End to Antarctica’s Vast Pine Island Glacier


Retreat of Pine Island Glacier Controlled by Marine Ice Sheet Instability

The Pine Island Glacier

The Thwaites Glacier

Hat tip to Colorado Bob who’s been tracking PIG since 1994



With Glaciers Undergoing Collapse, Sea Level Rise to Flood More Than 1,500 of Indonesia’s Islands, Capital City Over Next 50 Years


(Satellite rendering of the vulnerable Indonesia Archipelago — a system composing 17,000 islands. Image source: Commons)

From a climate-wrecking human warming spurring the melting of glaciers and ice sheets to the thermal expansion of the world’s oceans, sea level rise, to some degree or another over the next century is a given. How rapid this expansion progresses and how much land it devours will ultimately depend upon the amount of heat trapping gas we belch into the atmosphere and how sensitive the Earth’s climate system is to our increasingly traumatic insults.

Current conservative assessments from the Intergovernmental Panel on Climate Change (IPCC) estimate a total of 90 centimeters (nearly 1 meter) additional sea level rise before the end of this century. Today’s rate of sea level rise gets us to about 30 centimeters over the same period, so the IPCC is projecting that the pace of rising seas will more than triple over the coming years and decades.

Sea level rise 1993 to 2014

(Global Sea Level Rise from 1993 to 2014. Image source: AVISO.)

Despite the fact that the rate of sea level rise and related glacial melt would have to rapidly uptick to meet the IPCC estimate, it remains a conservative case. Temperatures, over the next century under business as usual fossil fuel emissions or a moderate mitigation scenario, are likely to increase by between 5 and 9 degrees Celsius. This range of global heating is enough to eventually melt all or nearly all the glacial ice on Earth. So the heat forcing to the world’s glaciers is expected to be extreme, a blow at least equaling the temperature change between now and the last ice age. A temperature change that took 10,000 years to complete now crammed into an exceptionally brief period from 1880 to 2100.

Under such an outrageous pace of warming, a warming that could propel Earth to near Permian and PETM temperatures within 85 years, it is likely that the rate of sea level rise could be double or more that of IPCC predictions, possibly equaling or exceeding peak rates of sea level rise during the end of the last ice age at 10 feet per century. So the range of increase may well be between 1 and 3+ meters, making the IPCC case quite an underestimation if business as usual fossil fuel emissions continue.


(Survey of scientist projections of sea level rise in centimeters by 2100 under a high emissions scenario (RCP 8.5). Note that a majority of scientists project sea level rise in the range of 1 to 3 meters by 2100 with some scientists projecting as much as a 3 to 6 meter rise over the same period. Image source: Real Climate’s Excellent November Report on Sea Level Rise)

Stresses to glacial systems are already extreme even at the current human forcing of 400 ppm CO2, 1835 ppb methane, and at rising levels of a host of other greenhouse gasses. Current CO2 levels alone, during the Pliocene, were enough to establish seas as much as 75 feet higher than today. A fact that raises the question — if we already have 15-75 feet of sea level rise locked in, how swiftly will that rise occur? And the answer to that question depends on how rapidly the world’s largest glacial and ice sheet systems respond to human greenhouse gas forcing.

Very Large Glaciers Already on the Move

In a recent study one of the world’s largest ice sheets, the Pine Island Glacier, was found to be undergoing the first stages of an irreversible collapse. In other words, over the coming decades, the Pine Island Glacier (PIG) is due to complete an unstoppable slide into the Southern Ocean. And loss of the Pine Island Glacier alone commits the world to about 1 meter of additional sea level rise.

Unfortunately PIG is the first of many glacial systems from West Antarctica to Greenland that are likely to suffer the same fate. For from these vulnerable regions, mass losses from glacial melt have more than doubled over the past decade. In total, by 2008, about 90% of the world’s glaciers were in retreat. And since that time, warming has continued to advance with melt episodes becoming ever-more predominant.

Greenland melt lakes, dark snow, August 4, 2013.

Melt lakes, many larger than 5 kilometers across, form over Western Greenland, August 4, 2013. Summer of 2012 saw Greenland mass loss hit 600 cubic kilometers. Image source: Lance-Modis.

Greenland, for example, has exhibited increasingly severe melt stress over past summers with large stretches of lakes, many measuring 5-10 kilometers wide, forming over an ever-less-stable ice sheet. A towering ice sheet that boasts an average altitude of two kilometers, Greenland’s vast glacial system contains an immense volume of frozen water. But as great and mighty as this mountainous pile of ice may seem, human caused warming continues to deliver a series of ever-more damaging blows. By 2012  Greenland had experienced a record wasting with 97 percent of its surface area showing melt during July and over 600 cubic kilometers of ice lost throughout the entire year. Yet as warmth continues to advance poleward, the 2012 melt season is likely to seem tame with far greater annual losses in store.

So there are many reasons to believe the IPCC estimates for glacial melt rates and related sea level rise, as with Northern Hemisphere sea ice losses, are too conservative and that science, in general, is still coming to grips with a dramatic and geologically unprecedented pace of change. That said, even IPCC findings are becoming increasingly stark.

Indonesia to Lose 10% of its Islands by Mid-Century

For if only the very conservative IPCC estimates bear out, we are still likely to see dramatic loss of lands and displacement of human beings.

A glaring example appears in new report from Maplecroft’s Climate Change Vulnerability Index which found that more than 1,500 islands in Indonesia would disappear after just a half meter of sea level rise. The study also found that the same amount of sea level rise would flood up to half of the capital city of Jakarta. Meanwhile, the 90 centimeters of sea level rise projected by the IPCC for the end of this century would put 42 million people along the coastline at risk of losing their homes.

Ancha Srinivasan, principal climate change specialist with the Asian Development Bank (ADB) noted in an interview that:

This archipelago’s biggest threat is rising sea levels, where 42 million people living three kilometres from the coast are vulnerable if estimated sea level rise reaches up to 90 centimetres by the end of the century.

Indonesia is composed of over 17,000 islands, many of which are low lying or feature sprawling and vulnerable coast lines. It is located in a region of the world where ocean levels are among the most rapidly rising. It is among a growing number of islands and low-lying coastal regions that are under increasing threat from what would seem even a modest change in sea level.

But as we went at length to illustrate above, Indonesia and other regions may be lucky to see only a 90 centimeter rise. So these projected impacts, though seemingly stark, may be at the low end of what we are likely to experience. Add just one more meter and most of Jakarta is flooded while 42 million of Indonesia’s people are almost certain to be members of a vast global migration away from the world’s coastlines.


Indonesia Risks Losing 1,500 Islands by 2050

Indonesia: Rising Seas Threaten 1,500 Islands

Maplecroft’s Climate Change Vulnerability Index


Real Climate’s Excellent November Report on Sea Level Rise

What does a World at 400 PPM CO2 Look Like?

Pine Island Glacier Undergoing Irreversible Collapse

The Pine Island Glacier

SkS Report on Glacier Retreat

The Greenland Ice Sheet

Greenland Experiences 97 Percent Surface Melt in July of 2012

Scientists: Warming Ocean, Upwelling to Make an End to Antarctica’s Vast Pine Island Glacier

Southern Ocean Interface With Pine Island Glacier

(Southern Ocean interface with Pine Island Glacier as seen during the second week of January, 2014. Note the ocean has already invaded substantially land-ward pushing the glacial coastline back by between seven and ten miles. Image source: Lance-Modis)

Among Antarctica’s most vulnerable ice shelves, the Pine Island Glacier (PIG) is a massive feature. It rests on sloped terrain that is mostly below sea level even as it spills out into the southern ocean through a nearby bay, calving great icebergs that then slowly ride out, like floating ice faerie castles, into the stormy seas. In total, the shelf covers 160,000 square miles, an area two thirds the size of Great Britain.

The Pine Island Glacier is vulnerable for many reasons. It rests on sloped land that tilts it toward the warming seas. Much of it rests below sea level, making its underbelly open to the assaults of the upwelling currents of a rapidly warming ocean. As portions of the under-structure melt, the glacier becomes buoyant, floating on surface waters subject to waves, winds and currents which adds further stress to inland structures.

A few anchors held the great glacier in place over the millenia. The great pressure of ice pushing down shoved the glacier deep into the underlying Earth, for the most part, sticking it in place as it only slowly ground toward the sea.

But now these anchoring features are disintegrating, the warming waters rushing in from underneath, lubricating the ice bottom. The slope, the gravity, the long tongues of ice entering the ocean are all coming into play. The great ice sheet is in motion. A motion that scientists now conclude will not stop until the entire glacier collapses into the heating waters.

Rumors of Glacial Demise

That the Pine Island Glacier was one of Antarctica’s most sensitive to human warming has long been well known to scientists. The geographic features surrounding the glacier, the relatively high angle of slope tipping the glacier toward the ocean, and the large section of the ice shelf below sea level all attracted interest, questions and research.

By the mid 1990s, records of massive melt coming from the Pine Island Glacier began, with upwards of 10 cubic kilometers of ice observed to be lost each year. With ice loss rates continuing to increase, more efforts focused on determining the glacier’s ultimate fate. By the mid to late 2000s, average net ice loss rates were over 20 cubic kilometers per year.

Calving Pine Island

(The July 2013 calving of the Pine Island Glacier as shown in a Lance-Modis satellite shot.)

At about the same time, in 2001, 2007, and 2013, three great icebergs calved off of Pine Island. These were massive bergs, averaging over 2000 square kilometers in size. Though large iceberg calving from the Pine Island Glacier was historically typical, the size and frequency of these amazing events were enough to raise eyebrows and add to already rampant speculation that the Glacier may well be headed toward an inexorable collapse.

Ocean’s Impact on Basal Melt Discovered

By 2010, studies were beginning to come in showing that the Pine Island Glacier was experiencing a rapid melt from underneath. Warming deep ocean currents were upwelling from the Amundsen Sea to erode the glacier’s base. Ice loss from this basal melt was estimated to be even greater than that observed through the increasingly rapid motion of the glacier and related large ocean calving events.

PIG basal melt

(Image source: Nature)

Basal melt was also shown to be undermining the glacier, pushing deeper and deeper beneath the ice shelf and driving ocean water further into the continent. The mechanism for this increased basal melt came directly from a human warming of the deep ocean surrounding Antarctica. Accelerated deep ocean warming was coming more and more into play as human atmospheric heating transferred through the ocean surface and into the depths.

In the Antarctic, a massive pool of warm water developed in the depths surrounding the continent. The warmer water gathered beneath a fresher, colder layer that kept a lid on the warmth, forcing it toward the bottom. But near the continents, the dynamics of ocean currents and coastal mixing brought this warm water up to contact the coast and, in this case, the base of the Pine Island Glacier.

A Nature Geoscience study led by Dr. Adrian Jenkins found progressive basal melt due to the action and heat transfer of this warm, upwelling water (see image above). The evidence collected seemed grim. It appeared that the Pine Island Glacier may well be in the first stages of disintegration. But more comprehensive study was needed before conclusions could be drawn.

Prognosis: Irreversible Collapse

By 2013, enough information had been collected to start making model runs to determine the ice sheet’s ultimate fate. And, recently, three teams of scientists took up the task. The results of these model runs were stark. They showed that, no matter what, Pine Island’s Glacier was probably suffering from the early stages of an irreversible collapse.

Antarctica glacial velocity map

(Glacial velocity map of Antarctica. Note the very high velocity of the Pine Island and adjacent Thwaites glaciers. Image source: Antarctic Glaciers)

In the new Nature study entitled “Retreat of Pine Island Glacier Controlled by Marine Ice Sheet Instability” the authors applying these models found that the glacier had “been kicked and it’s just going to keep on rolling for the foreseeable future.”

Dr Hilmar Gudmundsson, one of the study’s authors in a recent interview with BBC noted:

“Even if you were to reduce melt rates, you would not stop the retreat. We did a number of model runs where we allowed PIG to retreat some distance back, and then we lowered the melt rates in our models. And despite doing that, the grounding line continued to retreat. You can talk about external forcing factors, such climate and ocean effects, and then there are internal factors which are the flow dynamics. What we find is that the internal dynamics of flow are such that the retreat is now self-sustaining.”

In other words, even if the climate somehow miraculously cooled or if the warming ocean somehow managed to melt less ice at the base of the Pine Island Glacier, the glacier would still ultimately destabilize and collapse.

This is hard news, as it has implications for the rest of West Antarctica and, ultimately, about 25 feet worth of sea level rise now locked in the ice. As noted above, the Pine Island Glacier is a massive section of West Antarctica. It is responsible for the draining of about 20% of this section of the continent’s Ice and is one of the primary barriers preventing rapid sea level rise. It is the first domino to start falling. But other dominoes sit in series behind it.

The beginning of PIG’s catastrophic collapse will also likely have major implications for Antarctica’s net ice loss. Gudmundsson’s group found that average melt rates from the Pine Island Glacier are expected to more than quadruple over the next 20 years, increasing to over 100 cubic kilometers of ice loss each year. Total sea level contribution from the Pine Island Glacier alone could be as much as 10 millimeters over the same period, according to model assessments.

This is a large contribution from just one ice sheet. A contribution that is not yet accounted for in global climate simulations for sea level rise. And we have yet to take into account potential additions from other Antarctic melt sources like the adjacent Thwaites glacier or the large glaciers that drain into the Ross Ice Shelf.

In short, if Pine Island has reached the point of no return, then the rest of West Antarctica may well be soon to follow.


Retreat of Pine Island Glacier Controlled by Marine Ice Sheet Instability

Observations Beneath Pine Island Glacier in West Antarctica and Implications for its Retreat

Pine Island Glacier Retreat “Irreversible”

Ocean Warming Shown to Melt Ice Sheets From Below


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