| Cold-based, non-erosive ice caps on the interior plateau of northern Baffin Island have lost more than half their area since 1958. Based on melt rates since 1958, all ice on the plateau is expected to be gone in the next 60 years. The aim of this project is to understand the history of these ice caps over the Holocene in order to gain a better perspective on the current state of rapid melt. During the Little Ice Age ice covered ∼50% of the plateau and the equilibrium line altitude (ELA) was ∼650 m above sea level, 350-300 m lower than the present ELA. Radiocarbon dates of moss preserved beneath the ice reveal that ice has existed on the plateau since at least ∼900 AD. Little ice-cap growth occurred ∼1000-1250, correlative with the Medieval Warm Period. Periods of widespread ice-cap growth associated with ELA lowering of ∼200 m occur at ∼1280 and 1440 AD, separated by a 160 year period of fluctuating ice-cap size but continued growth, corresponding to the onset of the Little Ice Age. Ice-cap growth at 1280 and 1440 AD, as well as a period of growth at 930 AD, may have been triggered by volcanic eruptions through a stratospheric sulfate aerosolinduced decrease of summer radiation and perpetuated by already cooling climate and positive feedbacks associated with increased albedo. Evidence from both in situ 14C and lake cores suggests that ice existed on the plateau for at least an additional 1000 years prior to the last 1000 years. Ice may have existed since some time after 2.8 ka, as indicated by the termination of lake production after 2.8 ka. The plateau was likely ice-free in the mid-Holocene from deglaciation at ∼6 ka until ∼2.8 ka, corresponding with higher insolation than present. The future ice-free state will be a new condition for the late-Holocene, as permanent ice has existed on the plateau for at least the last 1000 and possibly 2000 years. |
