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

Tottering Totten and the Coming Multi-Meter Sea Level Rise

A new scientific study has found that the Totten Glacier is fundamentally unstable and could significantly contribute to a possible multi-meter sea level rise this Century under mid-range and worst case warming scenarios.

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408 Parts per million CO2. 490 parts per million CO2e. This is the amount of heat-trapping CO2 and total CO2 equivalent for all heat-trapping gasses now in the Earth’s atmosphere. Two measures representing numerous grave potential consequences.

We’re Locking in 120-190 Feet of Sea Level Rise Long Term

Looking at the first number — 408 parts per million CO2 — we find that the last time global levels of this potent heat-trapping gas were so high was during the Middle Miocene Climate Optimum of 15-17 million years ago. During this time, the Greenland Ice Sheet did not exist. East Antarctic glacial ice was similarly scarce. And the towering glaciers of West Antarctica were greatly reduced. Overall, global sea levels were 120 to 190 feet higher than they are today. Meanwhile, atmospheric temperatures were between 3 and 5 degrees Celsius hotter than those experienced during the late 19th Century.

Antarctica Below Sea Level

(Large sections of Antarctica rest below sea level. A physical feature that renders substantial portions of Antarctica’s glaciers very vulnerable to rising ocean temperatures. Since the latent heat content of water is substantially higher than that of air, even comparatively small ocean temperature increases can cause significant melt in sea-facing glaciers and in below sea level glacial basins. Image source: Potential Antarctic Ice Sheet Retreat Driven by Hydrofracturing and Ice Cliff Failure.)

Hitting the 408 ppm CO2 threshold this year catapults the current push for global climate transitions outside of the Pliocene context of 3 to 5 million years ago (topping out at 405 parts per million CO2) and places it in the bottom to mid-range of the Middle Miocene context (300 to 500 parts per million CO2). The 490 ppm CO2e number — due to added atmospheric heating contributions from human-emitted gasses like methane, chlorofluorocarbons, NOx compounds, and others — is enough to catapult our current climate context into the upper Middle Miocene range.

If global greenhouse gasses were to stabilize in this range long-term (for a period of hundreds of years), we would expect the Earth’s climate and ocean states to become more and more like those experienced 15-17 million years ago. Unfortunately, atmospheric concentrations of heat trapping gasses are still rapidly rising due to an increasingly dangerous emission coming from global fossil fuel burning. In addition, risks are rising that the Earth System will begin to contribute its own substantial amounts of carbon — possibly enough to raise the CO2e number by around 50 to 150 ppm over the next few centuries. Two contributions — one we control and another we do not — that risk swiftly pushing the global climate context into a 550 to 650 ppm CO2e range that is enough to eventually melt all the glacial ice on the planet.

Glacial Inertia vs Lightning Rates of Warming

It’s a tough climate state. A context that many scientists are still having difficulty coming to grips with. First, the global glacier research community is still looking at the world’s potential future ice melt in Pliocene and Eemian contexts. This makes some sense given the fact that current atmospheric warming in the range of 0.9 to 1.3 C above 1880s values is more in line with those two climate epochs (the Eemian saw seas 10-20 feet higher than today and the Pliocene saw seas at 25-75 feet higher). But it doesn’t take into account the underlying heat forcing and the likely climate end-state.

Second, we don’t really have a good grasp on how fast or slow glaciers will respond to the added heat we’re putting into the Earth System. We do know that at the end of the last ice age, melting glaciers contributed as much as 10 feet of sea level rise per Century. But this was during a time of comparatively slow global temperature increase at the rate of about 0.05 C per Century — not the current rate in the range of 1.5 to 2 C per Century, which is 30 to 40 times faster.

10 Feet of Sea Level Rise South Florida

(What 10 feet of sea level rise would do to South Florida. Given the increasing vulnerability of glaciers around the world to human-forced warming, there’s a rising risk that seas could rise by 10 feet before the end of this Century. Image source: Climate Central.)

In early studies, much weight has been given to glacial inertia. And older climate models did not include dynamic ice sheet vulnerabilities — like high latent-heat ocean water coming into contact with the submerged faces of sea-fronting glaciers, the ability of surface melt water to break up glaciers by pooling into cracks and forcing them apart (hydrofracturing), or the innate rigidity and frailty of steep ice cliffs which render them susceptible to rapid toppling. But now, new studies are starting to take these physical melt-amplifying processes into account and the emerging picture is one in which glacial melt and sea level rise may end up coming on at rates far more rapid than previously feared.

Overall, when taking a look at these newly realized ice-sheet weaknesses, it’s worth noting that the total heat forcing impacting the world’s ocean, air, and glacial systems is now rising into a range that is much more in line with Middle Miocene values. And that global temperatures are now increasing at a lightning rate that appears to be unprecedented in at least the past 60 million years.

Tottering Totten

It’s in this dynamic, rapidly changing, and arguably quite dangerous climate context that new revelations about the stability of one of East Antarctica’s largest glaciers have begun to emerge. In size, the Totten Glacier is immense — covering an area the size of California in mountains of ice stretching as high as two and a half miles. If all of Totten were to melt, it would be enough to raise seas by around 11 to 13 feet — or about as much as if half of the entire Greenland Ice Sheet went down.

Edge of the Totten Glacier

(The Totten Glacier, at lower edge of frame, faces a warming Southern Ocean. How rapidly this great mass of ice melts will, along with the destabilization of numerous other glaciers around the world due to a human-forced warming, determine the fates of numerous coastal cities and island nations during this Century and on into the future. Image source: LANCE-MODIS.)

Last year, a study found that warm, deep circumpolar water was beginning to approach ice faces of the Totten Glacier plunging 1 mile below the surface of the Southern Ocean. The study observed a rapid thinning that appeared to have been driven by this new influx of warmer ocean water near the glacier base:

Totten Glacier… has the largest thinning rate in East Antarctica. Thinning may be driven by enhanced basal meltingWarm modified Circumpolar Deep Water, which has been linked to glacier retreat in West Antarctica, has been observed in summer and winter on the nearby continental shelf beneath 400 to 500 m of cool Antarctic Surface Water…We identify entrances to the ice-shelf cavity below depths of 400 to 500 m that could allow intrusions of warm water if the vertical structure of inflow is similar to nearby observations. Radar sounding reveals a previously unknown inland trough that connects the main ice-shelf cavity to the ocean. If thinning trends continue, a larger water body over the trough could potentially allow more warm water into the cavity, which may, eventually, lead to destabilization of the low-lying region between Totten Glacier and the similarly deep glacier flowing into the Reynolds Trough (emphasis added).

Observed increasing melt rates for such a huge slab of ice in Eastern Antarctica was generally seen as a pretty big deal among glacial scientists and a flurry of additional research soon followed. By last week, a model study had found that Totten alone could produce nearly a meter of sea level rise before the end of this Century if global warming forces ocean waters to heat up by 2 C or more near the Totten Glacier. The study also found that 5 C worth of local ocean warming would be enough to force nearly 3 meters worth of sea level rise from this single large glacier over a relatively short time-frame.

Donald D. Blankenship, lead principal investigator for the new ICECAP study noted:

“Totten Glacier’s catchment is covered by nearly 2½ miles of ice, filling a California-sized sub-ice basin that reaches depths of over one mile below sea level. This study shows that this system could have a large impact on sea level in a short period of time.”

Like many large glaciers around the world, a huge portion of Totten’s ice sits below sea level. This feature makes the glacier very vulnerable to ocean warming. Water carries far more latent heat than air and just a slight rise in local ocean water temperature can contribute to rapid ice loss. Totten itself rests in three large below sea level basins. And study authors found that 2 C to 5 C warming of local ocean waters with somewhat greater local air temperature increases was capable of flooding these basins in stages — forcing Totten’s glacial ice to flow out into the Southern Ocean and provide significant contributions to sea level rise.

Unfortunately, Totten is just one of many large glacial systems that are now destabilizing across Antarctica. And researchers are now beginning to identify significant potential sea level rise contributions from Antarctica alone (ranging from two feet to nearly two meters) before the end of this Century. In New Scientist, during March, Antarctic researcher Rob Deconto notes:

“Today we’re measuring global sea level rise in millimetres per year. We’re talking about the potential for centimetres per year just from [ice loss in] Antarctica.”

Centimeters per year sea level rise is about ten times faster than current rates and implies 100 year increases — once it gets going — in the range of 2 to 3 meters. Such increased melt does not include Greenland’s own potential sea level rise contribution. Nor does it include sea level rise from other glacial melt and ocean thermal expansion. As such, it appears that multi-meter sea level rise is becoming a more and more distinct possibility this Century. Furthermore, the paleoclimate context is now pointing toward catastrophic levels of overall melt and sea level rise if global greenhouse gasses aren’t somehow stabilized and then swiftly reduced.

Links:

Repeated Large-Scale Retreat and Advance of Totten Glacier Indicated by Inland Bed Erosion

The Totten Glacier

The Human-Warmed Southern Ocean Threatens Major Melt for East Antarctica

Fundamentally Unstable — Scientists Confirm Their Fears About East Antarctica’s Biggest Glacier

Potential Antarctic Ice Sheet Retreat Driven by Hydrofracturing and Ice Cliff Failure

Unstable East Antarctic Glacier Has Contributed to Sea Level Rise in the Past

Sea Levels Set to Rise Far More Rapidly Than Expected

Unexpected Antarctic Melt Could Trigger 2 Meter Sea Level Rise

Entering the Middle Miocene

The Middle Miocene

LANCE MODIS

The Human-Warmed Southern Ocean Threatens Major Melt For East Antarctica

Totten Glacier. A mountainous expanse of ice in the very heart of the greatest accumulation of frozen water on Earth. A bastion of cold containing 11.5 feet worth of sea level rise if it were to melt in total. An accumulation roughly equal to half of all the frozen water in the whole of the Greenland Ice Sheet.

According to a new scientific report out this week, Totten Glacier is under threat of melt. Warm water is swelling up through troughs in the Continental Shelf zone, approaching the ice shelf locking Totten and a vast swath of interior East Antarctic glaciers. As with West Antarctica, this warm water upwelling has the potential to rapidly destabilize an already fast-moving glacier.

Totten Glacier basin

(Totten glacier outflow zone covers a massive region of East Antarctica. An area about equivalent in size to the entire US Southeast region. Warm water is starting to encroach upon an ice shelf locking this great ice mass into its Continental Catchment Basin. Image source: Australian Antarctic Division.)

Totten already hosts one of the most rapid thinning rates in East Antarctica. And, in fact, it was a satellite detection of this very thinning that set off a recent scientific investigation of the glacier’s stability. What the new scientific report identified was a threat that enhanced warm water upwelling from a human-heated circumpolar current would collide with an ice structure that is already vulnerable to melt.

The net result would mean a destabilization and acceleration of one of the greatest ice masses on the planet. Such an event would have far-reaching implications, especially relating to the pace and end state of warming-related global sea level rise.

From the abstract of Ocean Access to A Cavity Beneath Totten Glacier:

Totten Glacier… has the largest thinning rate in East Antarctica. Thinning may be driven by enhanced basal meltingWarm modified Circumpolar Deep Water, which has been linked to glacier retreat in West Antarctica, has been observed in summer and winter on the nearby continental shelf beneath 400 to 500 m of cool Antarctic Surface Water…We identify entrances to the ice-shelf cavity below depths of 400 to 500 m that could allow intrusions of warm water if the vertical structure of inflow is similar to nearby observations. Radar sounding reveals a previously unknown inland trough that connects the main ice-shelf cavity to the ocean. If thinning trends continue, a larger water body over the trough could potentially allow more warm water into the cavity, which may, eventually, lead to destabilization of the low-lying region between Totten Glacier and the similarly deep glacier flowing into the Reynolds Trough. (emphasis added)

At issue are two pathways for this upwelling, warm, deep water to follow:

totten_glacier_labeledpaths

(Topographic map of the Totten Glacier outlet region and nearby seabed. Note the vulnerable water inlets [orange lines], the inland troughs and basins [red highlights and blue topographic signature] and the rather advanced inland extent of the grounding line [white line]. Image source: Ocean Access to a Cavity Beneath Totten Glacier.)

The pathways are identified by the orange lines in the topographic image above. The lines identify underwater valleys that run out to the deeper, warmer waters accumulating on the edge of the Antarctic Continental Shelf region. As the waters rise, scientists are concerned that these troughs will act like channels, funneling a flood of much warmer than normal water beneath the belly of the great glacier.

The result is an instance of ‘global consequence.’ The authors note:

We estimate that at least 3.5 m of eustatic sea level potential drains through Totten Glacier, so coastal processes in this area could have global consequences.

Indeed. If we add in all the other destabilized glaciers around the world to Totten, should it destabilize, you end up with about 26 feet of sea level rise locked in. And that has some pretty staggering consequences when you look at impacts to the world’s coastlines.

This is what 20 feet of sea level rise impact looks like for the US Southeast and Gulf Coasts:

NASA six meter sea level rise SE

(Six meters of sea level rise would permanently inundate many of the major cities along the US Gulf and Southeastern coasts. Areas inundated shown in red. Image source: NASA.)

But, perhaps worst of all, is the fact that some of the world’s longest lasting and most stable accumulations of frozen water are now under threat of melt.

In essence, what we are witnessing is possible initiation of the end of the greatest and oldest ice province on Earth. East Antarctica glaciated 35 million years ago, when atmospheric CO2 levels fell below a range of 500-600 parts per million, and has been mostly stable or growing ever since. Now that region of ice, the most ancient remaining in the memory of Earth, is under threat. With human greenhouse gasses in the range of 484 ppm CO2e (CO2 equivalent) and 400 ppm CO2 and rising, it appears that even the oldest glaciers are under existential threat.

To this point, Eric Rignot noted in a recent interview:

“..the stage is set. You have a submarine glacier and a deep trough. The warm water is not too far from that frontal region and we’ve seen some changes in the glaciers that suggest that something is happening at their base.”

Links:

Ocean Access to A Cavity Beneath Totten Glacier

Hidden Channels Beneath East Antarctica Could Cause Massive Melt

Australian Antarctic Division

NASA

A Glacier Area the Size of the Entire South is Melting Away

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