Some key questions that remain widely debated are what initiated the last deglaciation of the global ice sheets and what was their subsequent role during deglaciation in climate change, questions may be best assessed from the record of individual ice sheets rather than the integrated record.
In a study published on 7 August 2009 in the journal Science Clark et al. compiled and analyzed more than 5000 dated ages in order to develop a record of maximum regional ice extent around the time of the Last Glacial Maximum.
There is considerable regional variability in the timing of when ice sheets (and various sectors of ice sheets) first reached their local last glacial maxima. mountain glaciers were near or at their maximum extent by around 30,000 years ago. The onset of Northern Hemisphere deglaciation 19,000 to 20,000 years ago was induced by an increase in northern summer insolation, providing the source for an abrupt rise in sea level.
The authors have shown that the duration of the LGM sea-level lowstand (26.500 to 19,000 years ago) is in excellent agreement with the duration of maximum extent of most of the global ice sheets, suggesting that most of the global ice sheets were in near-equilibrium with climate during this 7500-year interval.
Another paper published on 8 August 2009 in Palaeocanography on the Last Glacial maximum concerns the “Impact of strong deep ocean stratification on the glacial carbon cycle”. During the Last Glacial Maximum, the climate was substantially colder and the carbon cycle was clearly different from the late Holocene (the Holocene is the geological epoch after the Ice Age, which means that it began approximately 11 700 years ago).