Hall, B.L., Koffman, T. and Denton, G.H. 2010. Reduced ice extent on the western Antarctic Peninsula at 700-970 cal. yr B.P. Geology 38: 635-638.
Hall et al. examined organic-rich sediments exposed by recent retreat of the Marr Ice Piedmont on western Anvers Island, where glaciers have been undergoing considerable retreat in response to the well-documented warming of the Antarctic Peninsula, obtaining moss and marine shells from natural settings within 26 meters of the present ice front, as well as both clumps of peat and shells from sediments reposing in a tunnel beneath the residual ice mass, several samples of which were radiocarbon-dated and the results converted to calendar years. This work revealed, in their words, that "peat from the overrun sediments dates between 707 ± 36 and 967 ± 47 cal. yr B.P.," which led them to conclude that "ice was at or behind its present position at ca. 700-970 cal. yr B.P," which they interpret as implying that "the present state of reduced ice on the western Antarctic Peninsula is not unprecedented," which means that this period was at least as warm as, or likely even warmer than, the peak warmth of the Current Warm Period.