These data suggest that the recession of this ice stream was largely controlled by sea level rise, with a 55 m in sea level
rise during deglaciation resulting in 225 km of grounding - line recession26.
But there is a lag of CO2 after temperature of some 600
years during deglaciations, and several thousands of years during the onset of new ice ages.
While the
overlap during deglaciations is large (which makes it near impossible to make any estimates of relative forcings), during the start of the last ice age, there was no overlap: CO2 started to decrease (some 40 - 50 ppmv) when the temperature was already near it's minimum.
He thinks that we can look to paleoclimate as evidence for abrupt climate change — and indeed we can — but the examples he has to use are those of abrupt
change during deglaciation (YD) or during glacial climate (D - O; Heinrich; Bond).
[Response: Turns out that hydrate preservation is much more sensitive to changes in temperature than it is changes in pressure, so what we might look for is release of
methane during deglaciation.
«There is no convincing evidence that a sufficiently large reservoir of old metabolic carbon existed in some mysterious location in the glacial ocean only to be
ventilated during deglaciation,» argues paleoclimatologist Lowell Stott of the University of Southern California, who was not involved in the study.
«The WAIS Divide ice core allows us to identify each of the past 30,000 years of snowfall in individual layers of ice, thus enabling detailed examination of
conditions during deglaciation,» said Paul Cutler, NSF Polar Programs» glaciology program manager.
The magnitude and timing of this temperature shift are similar to those of nearby Lake Malawi (14), indicating that our TEX86 record captures regional temperature change in tropical southeast
Africa during deglaciation.
In a few
places during the deglaciation, local increases in temperature of 5 to 10 °C are likely to have occurred over periods as short as a few decades.
Hence there is a chance that Southern Ocean could amplify the warming trend by releasing CO2 as it
did during deglaciation.
The carbon - 13 signal is also driven by changes in organic carbon (trees and soil carbon), such that if there were more methane
degassing during deglaciation, there would have to be more terrestrial biosphere uptake.
The climatic regimes that
developed during the deglaciation period in many areas, including much of North America, have no modern analog (i.e., no regions exist with comparable seasonal regimes of temperature and moisture).
But there is a lag of CO2 after temperature of some 600
years during deglaciations, and several thousands of years during the onset of new ice ages.
While the
overlap during deglaciations is large (which makes it near impossible to make any estimates of relative forcings), during the start of the last ice age, there was no overlap: CO2 started to decrease (some 40 - 50 ppmv) when the temperature was already near it's minimum.
The sharpest methane concentration increases
occur during deglaciations, in phase with Greenland (NH) temperature and monsoon intensity increases.
During deglaciation, the melted ice - water returned to the oceans, causing sea level to rise.
However,
during deglaciation, the faults experience accelerated slip and earthquakes are triggered (see Post-glacial rebound).
And remember,
during deglaciations, outgassing from the oceans would have occurred in a context in which warming was occurring, but not an exogenous increase in atmospheric CO2 — and outgassing (or not!)
Younger Dryas - A period 12.9 to 11.6 thousand years ago,
during the deglaciation, characterized by a temporary return to colder conditions in many locations, especially around the North Atlantic.
A simulation of the Siberian continental margin after glacial sea level drop and exposure to the cold atmosphere, snapshot as sea level rises
during the deglaciation.