Climate in Earth History Studies in Geophysics (1982) / Chapter Skim
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3 Climate Steps in Ocean History--Lessons from the Pleistocene
3 Climate Steps in Ocean History--Lessons from the Pleistocene
Pages 43-54
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From page 43... ...
Alternatively, the same event might be seen as an inevitable consequence of a general cooling trend with strong positive feedback setting in, from albedo increase, once a snow-cover lasts for a certain part of the year. The first approach emphasizes a cause that is external to the climate producing system, the second focuses on positive feedback mechanisms within the system.
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From page 44... ...
Likewise, instability evidentf y grows with growing ice caps. Rapid large transgressions become possible through the storage of continental ice masses; such transgressions can cause rapid changes in albedo (water is dark; land is bright; see Table 3.2)
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From page 45... ...
We must assume that before the Ice Age the lack of strong albedo feedback allowed negative feedback to hold sway in dampening climatic fluctuations. Negative feedback, of course, ultimately provides the climatic stability that allowed life to exist on E arth for billions of years.
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From page 46... ...
One important factor, probably is the removal of positive albedo feedback from falling sea level. Once the sea level falls to the shelf edge, a further drop does not result in much decrease of ocean surface; thus the albedo stabilizes.
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From page 47... ...
Incidentally, if much of the heat comes in the form of rain, the runoff will be a mixture of rain and meltwater and its oxygen isotope composition will be somewhere between that of rain and glacial ice. To get positive feedback, we must ask that the melting, once started at some minimum rate, enhance further melting.
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From page 48... ...
THE PHENOMENON OF'RESERVOIR COLLAPSE Glacial ice may he seen as a transient reservoir of water, outside the main ocean basin, which, when reunited with the ocean, suddenly raises sea level with all the attendant effects on climate through a decrease in alhedo and an increa e of supply of moisture to the atmosphere. We can view the melting of ice caps as a 'reservoir collapse" that feeds on itself once destruc tion proceeds at a minimum rate.
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From page 50... ...
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From page 51... ...
Evidently, the waxing and waning of ire caps is a sufficient but not a necessary condition for producing fluctuations in the transient carbon reservoir Any mechanism producing fluctuations in sea-level and dry-wet cycles will do. Of special interest is the possibility that the size of the transient carbon reservoir can be greatly increased if the deep ocean provides temporary carbon storage through changes in mixing time and oxygenation of the deep sea.
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From page 52... ...
Even tentative answers to such questions should lead to fruitful working hypotheses regarding climatic change over geologic time spans. The concept of interacting transient reservoirs suggests that climatic s)
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From page 53... ...
. Climate changes and lags in Pacific carbonate preservation, sea surface temperature, snd gdobal ice volume, in The Fate of Fos il Fu I CO2 in the Oceans, N
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From page 54... ...
. Origin of ice ages: An ice shelf theory for Pleistocene gdeoiation, Nature 201, 147-149.
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