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How Greenland Melt Can Kick off A Warm “Ill Wind” Near Antarctica

Sixteen thousand years ago, Greenland melt set off a cascade of impacts to the world ocean and atmosphere that led to the dredging of carbon rich waters from deep below the Pacific surface. These waters then disgorged enough carbon into the atmosphere to ultimately raise CO2 levels by 40 parts per million.

(Related: Bad Climate Wind Rises.)

A recent report in Nature Communications found that:

“During this earlier period, known as Heinrich stadial 1, atmospheric CO2 increased by a total of ~40ppm, Antarctic surface atmospheric temperatures increased by around 5°C and Southern Ocean temperatures increased by 3°C.”

How did it all happen? According to the science, Greenland melt slowed down North Atlantic Deep Water formation. This, in turn, caused the North Atlantic to cool and the South Atlantic to warm. The resulting change in temperature then shoved the band of stormy weather called the Inter-Tropical-Convergence-Zone southward. Subsequently, the westerlies in the Southern Hemisphere were shifted poleward and strengthened. Stronger, more southward running winds around the southern pole dredged up carbon rich deep water near the pole and on into the Pacific. This carbon then transferred to the atmosphere.

It’s an interesting bit of science. But it has a good degree of relevance to the present day. That’s because Greenland is again melting greater volumes of water into the North Atlantic. The North Atlantic is again cooling. And the Southern Ocean winds are again being driven south as they strengthen.

(How Greenland melt pulled carbon from the Southern Ocean. A process that is being driven to repeat by present human-forced climate change. Image source: Nature Communications.)

According to lead author Dr. Laurie Menviel:

“With this in mind, the contraction and strengthening of westerly winds today could have significant implications for atmospheric CO2 concentrations and our future climate.”

This is a kind of feedback that results from the warming humans have caused that can result in more carbon being wrung from the ocean. And it’s a concern because it shortens the available time-frame in which to respond to the crisis that is climate change.

(Greenland melt, the North Atlantic cool pool, and strengthening, southward moving Southern Ocean winds. These dynamics set off a carbon feedback about 16,000 years ago. Similar dynamics are coming into play today due to human caused climate change. Image source: Earth Nullschool.)

To be clear, present rates of fossil fuel burning are dumping an amount of carbon into the atmosphere at a much higher rate than this identified Earth System response could ever match. But, as the study authors note, the Southern Ocean has already sequestered 10 percent of carbon emitted by humans. If that sequestration halts and then reverses, then the rate of atmospheric CO2 accumulation, even if emissions stay stable, will rise by about 0.2 to 0.4 ppm per year.

This report lends further urgency to global efforts by responsible institutions and individuals to reduce global carbon emissions and transition to clean energy. Bringing the more difficult outcomes of rising heat trapping gasses closer and closer to the present day.

Please read more here.

Hat tip to mlp in NC.

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It’s All About Fresh Water — Rapid Sea Level Rise Points To Massive Glacial Melt in Antarctica

It’s all about fresh water. In this case, massive freshwater outflows from the vast glaciers covering Antarctica.

This week, a new scientific report published in the Journal Nature found that from 1992 through 2012 freshwater outflow from Antarctica’s massive glaciers exceeded 400 gigatons each year. An immense flood of cold, fresh water. One that helped push sea levels rapidly higher around the Antarctic continent.

But with glacial melt on the rise and with mountains of ice now inexorably sliding seaward, these freshwater flows may just be the start of even more powerful outbursts to come. And such prospective future events have far-ranging implications for sea level rise, global weather, sea ice, human-caused climate change, and world ocean health.

Flood of Fresh Water Drives More Sea Level Rise Than Expected

The researchers discovered the tell-tale signature of this vast freshwater flood through chemical analysis of the seas surrounding Antarctica. The analysis pointed to a broad and expanding fresh water layer over-riding a warmer, saltier current issuing in from the Southern Ocean.

Since fresh water is less dense than salt water, the freshwater layer expands at the ocean surface causing sea levels to rise more rapidly. Meanwhile, the heating of the deep ocean surrounding Antarctica is thought to result in additional thermal expansion of the water column.

The researchers note:

On the basis of the model simulations, we conclude that this sea-level rise is almost entirely related to steric adjustment [changes that effect atomic spacing], rather than changes in local ocean mass, with a halosteric [salt based] rise in the upper ocean and thermosteric [heat based] contributions at depth. We estimate that an excess freshwater input of 430 ± 230 Gt yr−1 is required to explain the observed sea-level rise. We conclude that accelerating discharge from the Antarctic Ice Sheet has had a pronounced and widespread impact on the adjacent subpolar seas over the past two decades.

Antarctic Sea level Trend

(Rate of sea level rise in the seas surrounding Antarctica since 1992. Aggregate sea level rise is indicated in black. Individual seas data is broken out by color. Image source: Nature.)

Previously, increased rates of sea level rise surrounding Antarctica were thought to have been set off by increasing winds around the continent. The winds were thought to push more water up against the ice faces forming a kind of perpetual, low-grade storm surge. But the current finding provides strong evidence that the source of the sea level rise is due to less dense fresh water over-topping saltier waters flowing in from the Southern Ocean combined with increasing heat along the Antarctic sea bed. And, notably, this is not the first study to find increasing freshwater flows spilling into the Southern Ocean. Last year, a KNMI expedition uncovered similar results.

More Evidence of Large-Scale Melt

The study comes on the back of other recent findings showing that warm water invasion at Antarctic glacier bases had led to more rapid than expected melt and destabilization. In May, two NASA studies showed that a broad section of West Antarctica had destabilized and was sliding at an ever more rapid pace toward the ocean (see reports here and here). These findings held stark implications for global sea level rise as large ice regions of Greenland and West Antarctica, containing enough water to raise seas at least 15 feet, are likely already in a state of irreversible collapse.

 

Regional Anomaly Sea level Antarctic

(Sea level rise anomaly of the region surrounding Antarctica compared with the rest of the Southern Ocean. Red indicates faster than normal sea level rise. Blue indicates slower than normal sea level rise. Image source: Nature.)

This intensifying glacial melt and associated freshwater cap expanding out from the pole has implications — not just for sea level rise, but for sea ice, weather, and world ocean system health.

Impacts For Sea Ice

Large outflows of glacial fresh water may well be involved in the recent observed expansion of sea ice in the zone surrounding Antarctica (see recent related study). Fresh water serves as an insulative cap on the ocean surface preventing warm water from entering the top layer from below. The warm, salty water, in the Antarctic instead pools near the bottom or at the base of the great ice sheets.

Fresh water also freezes at a higher temperature than salt water. So sea ice in an expanding freshwater zone around Antarctica would have naturally higher resiliency even to the rising temperatures now occurring due to human-caused warming. Eventually, however, human heat forcing would overwhelm the ice, but not before a period of related, localized negative feedbacks.

The Iceberg Cooling Effect

The fresh water is a haven for sunlight-reflecting sea ice. It is interspersed with ice bergs from the glacial discharge and the large ice bergs cool the surrounding air. The fresh water layer prevents warm water upwelling from the warm, deep waters surrounding Antarctica. And the leading edge of the fresh water would drive salt-water down-welling along its advancing front. This would push warmer waters toward the ocean bottom, resulting in a kind of heat sink. And this is exactly the kind of dynamic that appears to be ongoing in the Southern Ocean now. These combined impacts are what is known as the ice berg cooling effect associated with large-scale glacial outbursts known as Heinrich Events. And we may well be in the process of setting off one of these geological scale nightmares.

20121230_iceberg_cooling_effect_Hansen_Sato

(Iceberg cooling effect under a mid-range warming scenario when global climate models were set to include the effects of large freshwater outflows from polar glaciers at a fast enough rate to raise seas by 60 cm through 2060 and 144 cm through 2080 [left frames]. Note the cooler zones in the Southern Ocean and North Atlantic adjacent to Greenland. Right frames include mid range emissions/warming scenarios and IPCC projected rates of sea level rise. It is worth noting that the amplifying effects of potential additional ghg release from the global climate system, particularly from Arctic and world ocean carbon stores, are not included in these simulations. Image source: Hansen and Sato.)

For global weather, such events have major implications. Regional cooling in the zone of freshwater outflow would juxtapose regional warming in the southern hemisphere meridional zones. This temperature differential would increase with the strength of the fresh water outflow and the rising intensity of the human-driven warming. The result would be a powerfully intensified storm track. Both the intensified storm track and increased atmospheric moisture loading due to human warming would result in much more powerful weather events than we are currently used to and the potential for catastrophic storms would drastically increase.

Amplifying Feedbacks and a Blow to World Ocean Health

Lastly, the expanding flood of fresh water would result in an increasing stratification of the world ocean system. This stratification would drive warm, salty water toward the ocean bottom and deplete already low oxygen reserves in that region. In addition, the extra heat is more likely to destabilize deep-sea clathrates — releasing methane which will speed in the oxygen depletion of the abyssal waters even as it tips the world ocean system to stop storing carbon and to begin releasing it. A combined feedback that is both an ocean killer and an amplifier to the already extraordinarily powerful human heat forcing mechanism.

Links:

Rapid Sea Level Rise Along Antarctic Margins Due to Increasing Glacial Discharge

Important Role For Ocean Warming and Enhanced Ice Shelf Melt in Sea Ice Expansion

Update on Greenland Ice Sheet Mass Loss: Exponential?

Grim News From NASA: West Antarctica’s Entire Flank is Collapsing

Nature: Human-Destabilized Antarctica Capable of Glacial Outbursts Contributing to Up to 14 Feet of Sea Level Rise Per Century

 

Big Arctic Warm-Up Predicted For This Week: Melt to Speed Up, Or Sea Ice to Show Resiliency Due to Variability, Strength of Negative Feedbacks?

Rate of Sea ice volume decline for all months

(Rate of Arctic sea ice volume decline with trend lines for all months in the PIOMAS measure. Updated through June of 2014. Image source: Wipneus.)

What it really all comes down to is heat energy balance. Beneath a warming, moistening Arctic atmosphere, sea ice loses resiliency due to slow attrition of the ice surface, due to loss of albedo as ice melts, and due to slower rates of refreeze during winter. Atop a warming Arctic Ocean, sea ice loses bottom resiliency, tends to be thinner and more broken, and shows greater vulnerability to anything that churns the ocean surface to mix it with the warming deeper layers — storms, strong winds, powerful high pressure systems.

It is this powerful set of dynamics under human caused climate change that has dragged the Arctic sea ice into what has been called a ‘Death Spiral.’ A seemingly inexorable plunge to zero or near zero ice coverage far sooner than was previously anticipated.

But in the backdrop of what are obviously massive Arctic sea ice declines and a trend line, that if followed, leads to near zero ice coverage sometime between next year and 2030, lurk a few little details throwing a bit of chaos into an otherwise clear and, rather chilling, picture of Arctic sea ice decline.

The Fresh Water Negative Feedback

One of these details involves the greatly increasing flow of fresh water into the Arctic Ocean. For as the Arctic heats, it moistens and rainfall rates over Arctic rivers increase. This results in much greater volumes of fresh river water flushing into the Arctic Ocean and freshening its surface. Another source of new fresh water flow for the Arctic is an increasing rate of Greenland melt outflow. The volumes, that in recent years, ranged from 300 to 600 cubic kilometers, can, year-on-year, add 1-2% to the total fresh water coverage in the Arctic Basin and North Atlantic. These combined flows mean that fresh water accumulates more rapidly at the surface, resulting in an overall increase in fresh water volume.

Change in salinity

(Change in Arctic Ocean Salinity between the mid 1990s and mid 2000s. Image source: Benjamin Rabe, Alfred Wegener Institute via Science Daily.)

Since 1990, we have observed just such an accumulation. For a recent study in 2011 showed that since 1992, Arctic Ocean surface fresh water content had increased by 20%. A remarkable increase due to the changing conditions that included greatly increased river outflows into the Arctic Ocean as well as a ramping ice melt from Greenland and the Canadian Archipelago Islands.

Fresh water is less dense than salt water and will tend to float at the surface. The physical properties of fresh water are such that it acts as a heat insulator, deflecting warmer, saltier ocean water toward the bottom. As such, it interrupts the heat flow from deeper, warmer Arctic Ocean waters to the sea surface and into the atmosphere.

As an added benefit to the ice, fresher water freezes at higher temperatures. So as the Arctic Ocean freshens, it creates a bit of wiggle room for the sea ice, giving it about a 0.5 to 1 C boost so it can sometimes even form during conditions that were warmer than those seen in the past.

In this manner, an expanding fresh water zone acts as a kind of last refuge for sea ice in a warming world. A zone in which sea ice may even periodically stage comebacks in the backdrop of rampant human warming. We may be seeing such a comeback in the Antarctic sea ice, which has shown anomalous growth and even contributed to an expanding cool atmospheric zone in the Southern Ocean, despite ongoing global warming. The freshwater and iceberg feeds from the vast Antarctic ice sheets have grown powerful indeed due to warm water rising up to melt the ice sheets from below, letting loose an expanding surface zone of ice and fresh water. This process will necessarily strengthen as more and more human heating hits the deep ocean and the submerged bases of ice sheets. An effect that will dramatically and dangerously reverberate through the ocean layers, setting the stage for a horrible stratification.

But today, we won’t talk about that. Today is for negative feedbacks due to fresh water flows from increasing polar precipitation and through ice sheet melt.

In the end, human warming dooms Arctic sea ice to an eventual final melt. But before that happens the increasing volume of fresh water from river flows and the potentially more powerful negative feedback coming from a growing ice and fresh water release from Greenland and the Canadian Archipelago will inevitably play their hands.

The Slower Than Terrible 2014 Melt Season

And so we arrive at the 2014 sea ice melt season for the Arctic. As with 2013, the melt got off to a relatively rapid start and then slowed through July as weather conditions grew less favorable for ice melt. Above freezing temperatures hit the ice above 80 degrees North about one week later than average, also providing some resiliency to the central ice — a condition that historically leads to higher end-season sea ice values in about 80 percent of the record.

The high pressure systems of early June gave way to weak storms and overall cloudy conditions. This shut down the cycle of strong melt, compaction, and transport of ice out of the Arctic that may have put 2014 on track for new records and another horrible slide down the Arctic sea ice death spiral. Instead, conditions set up for slower melt. Ice was retained and backed up through the Fram Strait, and the ice spread out, taking advantage of the thickened fresh water layer to slow its summer decline.

This is in marked contrast to the terrible 2007 and 2012 melt seasons which severely damaged the ice, making a total Arctic Basin ice melt all more likely in the near future. And it was also cutting against the 2010 to 2012 trend in which sea ice volume measures continued to plunge despite ambiguous numbers in sea ice area and extent (no new record lows) during 2010 and 2011. For this year, sea ice volume is now, merely, ‘only’ 4th lowest on record, according to the PIOMAS measure.

The fact that we are looking at a 4th lowest year as another bounce-back year is a clear indication of how terrible things became since 2010. And so far, this year’s melt has, like 2013, simply not been so terrible and terrifying. A wag back toward 2000s levels that is likely due to the inherent negative feedback of freshening surface water and to a swing in natural weather variability that, during any other year and in any other climate, would have pushed summer ice levels quite high indeed.

If the storms had been strong enough to draw a large enough pulse of warm water to the surface, the story might have been different. But, as it stands, this summer of weak Arctic weather hasn’t activated any major melt mechanism to push the ice into new record low territory. And so in many major monitors we are now above 2013 melt levels for this day.

Cryosphere Today shows sea ice area at 5.22 million square kilometers, above 2013 and just slightly above 2011 while ranging below 2008 for the date. Overall, the area measure is at 6th lowest on record for the date. Meanwhile, NSIDC shows sea ice extent at 7.74 million square kilometers or just above 2013 values for the same day but remaining below 2008 and 2009 by a substantial margin. Overall, also a sixth lowest value for the date:

Sea ice july 2014 v2

(NSIDC chart comparing sea ice melt years 2012 [dashed green line], 2008 [maroon line], the 1981 to 2010 average [solid line] and 2013 [pink line]. Image source NSIDC.)

So in the sea ice butcher board tally, with the negative feedback of fresh water floods and glacial melt moderately in play and with weather that is highly unfavorable for melt, we currently stand at 4th lowest in the volume record, 6th lowest in the extent record, and 6th lowest in the area record.

And now, things may just be about to get interesting…

Forecast Shows Arctic Heatwaves on the Way

GFS and ECMWF model runs show two warm ridges of high pressure developing over the Arctic this week. And the emergence of these warm and moist air flows into the Arctic may well have an impact by pushing the Arctic back toward melt-favorable conditions.

The first ridge is already expanding across the Canadian Archipelago. Yesterday it brought 80 degree temperatures to Victoria Island which still sits between wide channels clogged with sea ice. Smoke from wildfires is being entrained in this ridge and swept north and east over the remaining Archipelago sea ice and, today, the Greenland Ice Sheet.

While the smoke aerosol from fires blocks some of the incoming solar short wave radiation, it absorbs and re-radiates it as long-wave radiation. Many studies have shown this albedo-reducing darkening of the cloud layer by black and brown carbon aerosols has a net positive warming effect. In addition, the soot falls over both land and sea ice where it reduces reflectivity medium to long-term (Dark Snow).

Smoke streaming over Canadian Archipelago and Northwestern Greenland

(Smoke associated with record wildfires in the Northwest Territory streaming over the Canadian Archipelago, Northern Baffin Bay, and Northwestern Greenland beneath a dome of record heat. Image source: LANCE-MODIS.)

The ridge is expected to expand east over the next few days until it finally settles in as a moderate-strength high pressure system over Greenland. There it is predicted to juxtapose a set of low pressure systems that will slowly slide south and east over Svalbard. The conjoined counterclockwise cyclonic wind pattern of the lows and the clockwise anti-cyclone of the high over Greenland in the models runs over the Fram Strait. And so, for at least 4-5 days, the models predict a situation where sea ice transport out of the Arctic may be enhanced.

Meanwhile, on the other side of the Arctic, a series of high pressure systems are predicted to back up over the Pacific Ocean section of Irkutsk and Northeast Siberia. This ridge is expected to dominate coastal Siberia along the Laptev and East Siberian Seas. Temperatures along the coast are expected to reach 15-20 C above average, while temperatures over the waters are expected to rise to melt enhancing levels of 1 to 5 C.

Ahead of the ridge runs a warm frontal boundary that is heavily laden with moisture and storms. So a liquid and mixed precipitation band is likely to form over the East Siberian and Beaufort Sea ice as the ridge advances.

The ridge is projected to drive surface winds running from the south over the East Siberian Sea, across the polar region, and into the Greenland and Barents Seas. This cross-polar flow of warm, moist air will also enhance the potential for ice transport.

Melt Pattern

(Pattern more favorable for sea ice melt and transport emerging over the next seven days. This Climate Reanalyzer snapshot is at the 120 hour mark. Note Arctic positive temperature anomalies at +1.18 C. Will the pattern override potential negative feedbacks such as high fresh water content in the Arctic and unfavorable weather likely produced by the late emergence of temperatures above 0 C in the 80 North Latitude zone? Image source: University of Maine.)

Overall, it is a weather pattern that shows promise to increase melt, especially in the regions of the Canadian Archipelago and the East Siberia Sea, and to speed ice mobility and transport. Persistent lows near the central Arctic for the first half of this period and shifting toward Svalbard during the latter half will continue to disperse sea ice which may lend one potential ice resiliency feature to a pattern that is, otherwise, favorable for ice loss.

Negative Feedbacks and Weather Unfavorable For Melt

If the melt pattern described above comes to impact the ice and push greater rates of sea ice loss over the coming days and weeks, it’s likely that end season 2014 will end up with sea ice measures below those of 2013, but above the previous record lows seen during past years. This would likely put 2014 well within the range of the post 2007 era at 3rd to 5th lowest on record for most monitors. Not a new record year, but still well within the grips of the death spiral.

If, however, the weather predicted does not emerge or the sea ice retains resiliency through it, then 2014 stands a chance of pushing above final levels seen in 2013. In such an event, end season area and extent measures may challenge levels last seen during 2005 while sea ice volume maintains between 4th and 5th lowest.

If this happens, we may need to start asking this question:

Are negative feedbacks, in the form of greatly increased freshwater flows from rivers and glaciers, starting to pull the Arctic sea ice out of a high angle nose dive and are they beginning to soften the rate of decline? Or is this just a year when weather again wagged the dog as natural variability played a trump card for the summer of 2014 but further drives for new records will follow come 2015, 2016, or 2017?

In any case, near-term sea ice forecasts remain somewhat murky, as they should given the high instability of the current situation.

Links:

Science Daily

Now Melts the Arctic

The Arctic Ice Blog

NSIDC

LANCE-MODIS

University of Maine

PIOMAS

Cryosphere Today

Dark Snow

 

 

 

 

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