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Sleeping Ice Giants Stir — East Antarctica’s Totten Glacier Accelerates Toward Southern Ocean

“Up till now, we basically had a stationary [East Antarctic] ice sheet, and now it’s started to move,” — Catherine Walker, NASA post-doctoral fellow.

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East Antarctica. Home to most of the world’s remaining land ice. Scientists previously thought that this last bastion of somewhat stable ice in the world would only slowly succumb to the slings and arrows of human-caused climate change. That its ice giants would still sleep for some time — giving the world more time to stave off or avoid worsening rates of sea level rise. Unfortunately, new evidence reveals that this is not the case. That the best time to act on sea level rise was 20+ years ago, and that the second best time to act, in cutting fossil fuel based CO2 emissions, is now.

(Warm water upwelling near East Antarctica’s Totten Glacier threatens to accelerate global sea level rise. Image source: Texas Institute for Geophysics.)

Extreme warming now periodically besets this frozen land. Massive ice bergs are breaking off from West Antarctica, rainfall is now observed, at times, all around the frozen continent’s perimeter from west to east, and the vast Pine Island glacier is being undermined by warm water currents — causing it to crack up from the inside out.

Now, according to new research, one of East Antarctica’s largest glaciers — the Totten — is accelerating toward the Southern Ocean. It’s a situation that we warned about in an earlier post as an indicator of worsening risks of speeding sea level rise due to human caused climate change. Unfortunately, new studies by scientists have now confirmed that warm waters encroaching on Totten have already had an impact.

Researchers found that combined warm winds and encroaching warmer ocean currents had caused the glacier to speed up by 5 percent during the period of 2000 to 2006. This acceleration means that the vast glacier — home to enough ice to raise seas by 11-13 feet — is melting faster. It also means that the glacier is starting to succumb to the tremendous global heat forcing provided by human fossil fuel burning around the world. We should caution that this report covers a period from more than a decade ago. And since that time, human-forced global warming has considerably advanced.

(The Totten Glacier itself contains enough ice to raise seas by 11-13 feet, which is comparable to all of West Antarctica. Its glacial catchment, however, is larger. Image source:  Australian Antarctic Division.)

The primary cause of Totten’s melt acceleration is wind-diven warm ocean currents starting to encroach upon the glacier. These warm currents dive deep and then upwell near the glacier faces and along their weak underbellies. What the new research shows is that CO2-based warming from fossil fuel emissions is increasing the heat content of the waters even as it drives the strengthening of winds that bring these waters into more frequent direct contact with glaciers like Totten.

Chad Greene, one of the study’s lead authors recently noted to Scientific American:

“Upwelling is driven not purely by the broad-scale magnitude of wind, but by the gradient in wind—how strong the wind is at one latitude versus how strong it is at a different latitude. And CO2 in the atmosphere is modeled to increase the wind gradient around Antarctica, and then therefore increase upwelling around Antarctica.”

Glaciers are very difficult to move when sitting still. But once they get moving, it’s very difficult to stop what amounts to a moving mountain of ice. Forces now encroaching upon Antarctica are now conspiring to trigger the seaward movement of various gigantic glaciers. Once that happens, a certain amount of sea level rise gets locked in. This new research indicates that Greenland and West Antarctica aren’t the only systems that are capable of seeing glaciers released in this fashion. With the new research from Totten, East Antarctica is starting to come into play as well. And that means that multi-meter sea level rise this Century is not out of the question.

Links:

Wind Causes Totten Melt Acceleration

A Flood of Warm Waters the Size of 30 Amazon Rivers is Melting One of East Antarctica’s Largest Glaciers

East Antarctica’s Biggest Glacier Lost Ice

How Wind Might Nudge a Sleeping Giant in Antarctica

Hidden Channels Beneath Antarctica Could Cause Massive Melt

Hat tip to Colorado Bob

 

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A Flood of Warm Water the Size of 30 Amazon Rivers is Melting One of East Antarctica’s Largest Glaciers

If we’ve learned anything this year, it’s that few of Antarctica’s submerged coastal glaciers are safe from the warming ocean. Places that we once thought wouldn’t be vulnerable to melt for decades or centuries are now starting to feel the heat of rising water temperatures.

The heat comes in the form of great floods of warmer than normal waters running beneath the ocean surface and then eating away at the undersides of ice shelves and sea fronting glaciers. These floods are provided by the warmth forced into the world ocean by rising global greenhouse gas concentrations. And such invasions are happening around Antarctica’s perimeter with increasing frequency. But perhaps the most disturbing such event now ongoing is the present warm water flood running in from the Southern Ocean toward East Antarctica’s Totten Glacier.

calving-front-of-the-totten-glacier

(The melting edge of the Totten Glacier. Image source: Antarctica.gov.)

Totten is a truly gigantic glacier. By itself representing an ice mass equal to that contained in all of West Antarctica’s many glaciers. If large sections of Totten and the associated Aurora Basin were to melt, seas could rise by 12 feet or more. During recent years, researchers identified a great canyon running between 2,000 and 3,600 feet below sea level and stretching six miles wide as a weak point for Totten — whose glaciers sit in an enormous, below sea level rift within East Antarctica.

Researchers recently found that the floating ice shelf buttressing Totten was melting from below. As of 2015, they hadn’t identified a mechanism for this melt. But they had a pretty short suspect list. This year, a new study led by Dr. Stephen Rich Rintoul found that a river of warm water flowing at a rate of 220,000 cubic meters per second was flooding into the vulnerable canyon entrance to Totten’s weak underbelly. The researchers determined that this volume of warm water — equaling a flow rate more than 30 times that of the Amazon River — was enough to account for the observed ice shelf losses over recent years in the range of 60 to 80 billion tons per year.

totten-glacier-basin

(The Totten Glacier of East Antarctica contains about as much ice mass as all of West Antarctica. Its catchment basin is roughly the size of the U.S. Southeast. Much of it sits below sea level. And an ice shelf buttressing the glacier’s largest outlet in a 6 mile wide and 3,600 foot deep canyon is rapidly melting. Once this ice shelf breaks apart, ocean water will flood inland along a reverse slope and the Totten Glacier will increase its rate of movement toward the ocean — significantly speeding rates of global sea level rise. Image source: Australian Antarctic Division.)

The study authors found that:

…several lines of evidence support the conclusion that rapid basal melt of the [Totten Ice Shelf] is driven by the flux of warm [modified circumpolar deep water] into the cavity: the presence of warm water at the ice front, the existence of a deep trough providing access of this warm water to the cavity, direct measurements of mass and heat transport into the cavity, the signature of glacial meltwater in the outflow, and exchange rates inferred from the heat budget and satellite-derived basal melt rates.

Presently, because the ice shelf floats, this melt is not adding to global sea level rise. But the shelf acts like a cork that’s stopping the rest of Totten from flowing into the ocean. And when the ice shelf weakens enough, it will rift and break apart — leaving the massive glaciers behind it exposed to the inrush of warm waters and removing the last major barrier preventing them from bursting out.

Links:

Ocean Heat Drives Rapid Basal Melt of Totten Ice Shelf

Scientists Confirm that Warm Ocean Water is Melting one of East Antarctica’s Biggest Glaciers

One by One, the Flood Gates of Antarctica are Breaking Open

Tottering Totten and the Coming Multi-meter Sea Level Rise

Antarctica.gov

Hat tip to Robert in New Orleans

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