Background
Much has been made of the break-up of the Antarctic Peninsula's Larsen-B ice shelf in early 2002, as it had long been claimed that the ice shelf had remained intact to that point in time throughout at least the past 10,000 years; and in Al Gore's documentary movie An Inconvenient Truth, its break-up is presented as evidence for the climate-alarmist claim that modern global warming is equally unique.

What was done
The authors investigated "the Holocene history of the northern Larsen Ice Shelf [sections A and B] to determine whether the recent retreat pattern is unique or has previously occurred on a millennial time scale." More particularly, they analyzed "the composition of ice-rafted debris to distinguish seasonally open-marine sediments from sub-ice shelf facies," and they examined "benthic foraminifera for clues to the former presence or absence of the ice shelf."

What was learned
Pudsey et al. report that the data they studied indicated "widespread ice shelf breakup in the mid-Holocene." This finding is harmonious with the earlier finding of Pudsey and Evans (2001) that the adjacent Prince Gustav Channel ice shelf also retreated in mid-Holocene time, but that subsequent colder conditions, in their words, "allowed the ice shelf to reform." It is also in harmony with the finding of Vaughan et al. (2001) that from 6000 to 1900 years ago the Prince Gustav Channel ice shelf, as they describe it, "was absent and climate was as warm as it has been recently." Consequently, and most recently, Pudsey et al. concluded that "the maximum ice shelf limit may date only from the Little Ice Age [our italics]," which they report is "widely recognized" to have held sway in that part of the world between 700 and 150 years ago.

What it means
A large body of data makes it pretty clear that the greatest extent of the Larsen ice shelf during the current interglacial likely occurred only a few hundred years ago, and that the portions of it that recently disintegrated (Larsen-A and Larsen-B) were probably created about that same time. In addition, it would appear that some 2000 years ago the Larsen-A and B ice shelves likely were altogether absent, and that temperatures of that time were likely as warm as, or even warmer than, they have been recently. Furthermore, there was approximately 100 ppm less CO2 in the air of that time than there is in the air of today; and this fact suggests that something other than anthropogenic CO2 emissions was the cause of the earlier "balmy" conditions of northeast Antarctica, which implies that that same something else, or something different yet, could well be responsible for the current warmth of the region.

References
Pudsey, C.J. and Evans, J. 2001. First survey of Antarctic sub-ice shelf sediments reveals mid-Holocene ice shelf retreat. Geology 29: 787-790.

Vaughan, D.G., Marshall, G.J., Connolley, W.M., King, J.C. and Mulvaney, R. 2001. Climate Change: Devil in the detail. Science 293: 1777-1779.