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Glaciers are receding in the northern Antarctic Peninsula and exposing previously entombed soils and plants. We used 39 black (dead) mosses collected from rapidly retreating ice margins at four sites along the Antarctic Peninsula to determine the kill dates using radiocarbon measurements and to constrain the timing of past glacier advances over the last 1500 yr. We established strict new criteria for sample collection to promote robust estimates of plant death. We found distinct phases of ice advance during ca. 1300, 800, and 200 calibrated years before 1950 (cal yr B.P.). We report estimates of the rate of glacier advance at ca. 800 cal yr B.P. at Gamage and Bonaparte Points (southern Anvers Island) of 2.0 and 0.3 m/yr, respectively. Although the range of kill dates is relatively narrow within a region, suggesting multiple glaciers advanced simultaneously, the rates of local advances can vary by almost an order of magnitude and are much less than retreat rates. Our kill dates coincide with evidence for glacier advances from other studies in the northern Antarctic Peninsula at ca. 1300, 800, and 200 cal yr B.P. and for penguin colony abandonment at several sites in the region ranging from 450 to 0 cal yr B.P. The combination of our new terrestrial evidence for glacier advances with other lines of evidence shows the regional synchroneity of glacial dynamics and cryosphere-biosphere connections during rapid climate shifts and the sensitivity of terrestrial ecosystems to climate cooling.