The melting news is not good. First there is the volume of the Arctic sea ice, which has hit a record low for the third year running. Knowing the powerful influence of local weather conditions on the Arctic sea ice, the steady fall is surprising. The warming-driven melt signal is overpowering the year-to-year variations.
And then there's Greenland.
|h/t Neven, via Michael Tobis|
Petermann Glacier also lost a chunk of ice twice the size of Manhattan:
|h/t Climate Denial Crock of the Week|
But all this may turn out to be the warm-up for the really stunning ice news of the week, which is the birth of a third long-term climate record, supplementing the ice cores of Antarctica and Greenland. "Lake E" is Siberia has come up big with 3 million years of sediment records.
Like most real science, the excitement of the press-release-worthy findings is somewhat mitigated by the boring necessity of having other scientists examine the findings, confirm the findings, etc. Some of the interesting stuff in the record, though, is as follows:
1. There seem to be large climate swings in the record which are far too large to be explained by orbital changes or any other known natural forcing. While this will doubtless be trumpeted by the "science knows nothing crowd," this result, if it holds up, would imply positive feedbacks in the climate system so powerful and exquisitely sensitive that they dwarf the original positive forcing. My sense of the recent literature has been that the most likely suspect for those feedbacks would be the carbon cycle (permafrost, changes in soil respiration, methyl hydrates, etc.) The authors of this study think that's not enough -- see #3, below.
2. The Arctic and Antarctic climates are linked. They tend to warm together and cool together.
3. Melting in Antarctica may turn out to trigger melting in Greenland and the rest of the Arctic:
4. The loss of ice from Greenland in Antarctica is likely to accelerate (gee, really?)First, they say, reduced glacial ice cover and loss of ice shelves in Antarctica could have limited formation of cold bottom water masses that flow into the North Pacific Ocean and upwell to the surface, resulting in warmer surface waters, higher temperatures and increased precipitation on land.Alternatively, disintegration of the West Antarctic Ice Sheet may have led to significant global sea level rise and allowed more warm surface water to reach the Arctic Ocean through the Bering Strait.Lake E's past, say the researchers, could be the key to our global climate future.
Point #3 brings to mind something from Eli's place. Fellow amateurs, gird your loins and follow me:
Shakun et al. find that at the end of the last ice age temperature increased immediately in the Arctic but only slightly, probably as a result of increased radiation during the northern hemisphere summer. As a result a small portion of the Arctic ice melted. The melt water had a lower salt concentration and thus was less dense than the surface water and sank although mostly not to great depths. The result was that the AMOC and thus the associated redistribution of heat between the Arctic and the tropics was interrupted. This meant that the temperature in the high northern latitudes no longer rose, but may, in fact, have even decreased slightly. This is exactly what was found in the data. As a result, the temperature rose in the southern tropics and then the southern temperate latitudes and finally in Antarctica. Only then did the data show an increase in CO2. So somehow warming of the southern latitudes leads to increased emissions of CO2. Simultaneous determination of the isotopic ratio (for example, according to RF Anderson, S. Ali, LI Bradtmiller, SHH Nielsen, MQ Fleisher, BE Anderson, and LH Burckle, Wind-Driven Upwelling in the Southern Ocean and the Deglacial Rise in Atmospheric CO2, Science, 323 , 1443-1448 (2009).) suggests that the CO2 source is a consequence of biological fixation of carbon residues, for example in plankton deposited on the ocean floor. This increase in CO2 concentration is more than twice as strong as expected from outgassing of CO2 from warmer sea water alone. It indicates that the exchange with the Southern Ocean deep water became more intense and carbon deposits were transferred from the depths to the surface. Only after a significant temperature increase in the south and an increase in CO2 concentration, did the temperature rise again in the northern hemisphere. This is interpreted as providing a feedback mechanism for for greenhouse gases to drive global warming.What if we put that together with the "Lake E" speculations? To wit:
So I tell myself the story: a slight change in solar forcing heats the North, which interrupts warm ocean currents, causing the South to heat. Ice sheets collapse, southern ocean currents change, and by some combination of unearthing plankton carbon, rising sea levels, and/or changing ocean currents, the North warms further, and more greenhouse gases are released.First, they say, reduced glacial ice cover and loss of ice shelves in Antarctica could have limited formation of cold bottom water masses that flow into the North Pacific Ocean and upwell to the surface, resulting in warmer surface waters, higher temperatures and increased precipitation on land.Alternatively, disintegration of the West Antarctic Ice Sheet may have led to significant global sea level rise and allowed more warm surface water to reach the Arctic Ocean through the Bering Strait.Lake E's past, say the researchers, could be the key to our global climate future.
Interesting story. Warming gets passed back and forth from North to South, until from modest beginnings you have a climate warmer than the present day. So what happens if, instead of a tiny tap on the Northern latitudes with a modest increase in insolation, you instead hammer the entire planet from stem to stern with a massive greenhouse gas forcing? We're about to find out.
UPDATE: The sharp eyes of the Hawk have spotted the Arctic Monitoring and Assessment Programme's (AMAP) 2011 report on Snow, Water, Ice and Permafrost in the Arctic (SWIPA).His summary of the summary is excellent.
Mostly this is stuff that is not news to regular readers; snow and ice are melting faster and faster. The loss of ice and snow is a positive feedback that leads to further warming. Permafrost is melting, releasing more carbon (we don't know how much yet). Greenland will melt faster and faster, but nobody knows how fast yet.
"So what happens if, instead of a tiny tap on the Northern latitudes with a modest increase in insolation, you instead hammer the entire planet from stem to stern with a massive greenhouse gas forcing?"ReplyDelete
I point to the new Pagani et al. paper pinning the Eocene hyperthermals to permafrost melt in Antartica (then still largely unglaciated). Remind me how the northern permafrost is doing?
Not very well; see the Arctic report linked to at the end (I know, rhetorical question.)ReplyDelete