Guest Post by Willis Eschenbach
In the first part of this disquisition, I discussed the oddity that the warmer it gets around Antarctica, the more ice accumulates on the Antarctic ice cap. However, that’s only one part of a very large planet. So I thought I’d take a look at the situation in Greenland. To start with, here is the Greenland temperature record:
The data archive says:
Temperature interpretation based on stable isotope analysis, and ice accumulation data, from the GISP2 ice core, central Greenland. Data are smoothed from original measurements published by Cuffey and Clow (1997), as presented in Figure 1 of Alley (2000).
Greenland ice-core records provide an exceptionally clear picture of many aspects of abrupt climate changes, and particularly of those associated with the Younger Dryas event, as reviewed here. Well-preserved annual layers can be counted confidently, with only 1% errors for the age of the end of the Younger Dryas 11,500 years before present. Ice-flow corrections allow reconstruction of snow accumulation rates over tens of thousands of years with little additional uncertainty. Glaciochemical and particulate data record atmospheric-loading changes with little uncertainty introduced by changes in snow accumulation. Confident paleothermometry is provided by site-specific calibrations using ice-isotopic ratios, borehole temperatures, and gas-isotopic ratios.
I note that after being a very chilly minus 45° to minus 50°C during the last glacial period, for the last 9,000 years or so the ice cap temperature has been running along at a smoking-hot minus 28-30°C …
So how does that temperature record compare with the Greenland ice accumulation rates? Figure 2 shows how fast the ice builds up on the ice cap:
Dang. The situation is the same in Greenland as it was in Antarctica—the warmer it gets, the faster the ice accumulates.
Now, the Vostok area in Antarctica is like a frozen desert, in that there is little annual snowfall. So at Vostok, the ice accumulation rates varied from about 10 to about 20 mm/year between glacial and interglacial conditions. Greenland, on the other hand, is much wetter, with much more annual snowfall. There, the accumulation rates vary from about 60 to about 240 mm/year as the temperature change occurs.
The greater amount of snow is also responsible for the greater sensitivity of the accumulation rates to the temperature. In Antarctica, the ice accumulation rate increased by 1.2 mm/year for each additional degree. In Greenland, the ice accumulation rate goes up by 8.4 mm/year per 1°C temperature increase.
A final oddity. While overall the temperature and ice accumulation rates move in the same direction, look at the modern interglacial era. For the last 9,000 years or so, the situation is reversed. Temperatures have been steadily dropping, but the ice accumulation has been rising … go figure. During this time, for each one degree of warming, ice accumulation goes down by 3.3 mm/year, not a small amount.
OK, so the Greenland ice cap acts the same as the Antarctic ice cap, in that the warmer it is, the more snow falls, and the faster the ice accumulates … except for the last 9,000 years, when it worked the other way. Hey, I can only go where the data leads me.
But what about in the areas where people actually live? At present, do we get more ice and snow on northern lands when it is warmer?
My early researches say no, but stay tuned, I’ll assuredly get back to that piece of research as long as I don’t get distrac… oooh, shiny …
My best regards to all of you. Here, another two inches (5 cm) of rain last night, and it is pouring down now, with more storms on the horizon. The trees like it. The garden likes it. I like it. The gorgeous ex-fiancee likes it. The cat hates it.
My Usual Request: Clarity is critical in order to ensure domestic tranquility. If you disagree with me or anyone, please quote the exact words you disagree with. I can defend my own words. I cannot defend someone else’s interpretation of some unidentified words of mine.
My Other Request: If you think that e.g. I’m using the wrong method on the wrong dataset, please educate me and others by demonstrating the proper use of the right method on the right dataset. Simply claiming I’m wrong doesn’t advance the discussion.