The Holocene Record of Alpine Glaciation in the Arctic

Abstract:

In the Arctic, the late Pleistocene mountain glacier record is limited due to expansive occupation of the high latitudes by vast ice sheets. However, certain centers of alpine glaciation, like the Brooks Range, northern Alaska, contain detailed Pleistocene moraine sequences. The Holocene record is more widespread and spans both the western and eastern sectors of the Arctic. Nevertheless, only in a few areas do we have more than a basic understanding of the Holocene moraine sequences and their general ages, usually defined by morphostratigraphy, lichenometry, and the odd indirect constraint by radiocarbon dating. Cosmogenic nuclide exposure dating has recently provided more precise absolute moraine chronologies, but well-dated sites are still few and far between. This presentation will focus on the latest view of the Holocene moraine chronology in the North American Arctic: the Brooks Range, Baffin Island and Greenland. The general pattern reveals: 1) a definitive lack of Younger Dryas moraines, at least in the Brooks Range and Baffin Island; 2) moraines deposited during the 8.2 ka event, at least on Baffin Island; 3) Neoglaciation was underway by ~5-4 ka, based on moraines in the Brooks Range and on lake sediments and ice-killed vegetation on Baffin Island and Greenland; 4) moraines deposited during the Little Ice Age mark the largest extent of glaciers during the late Holocene in most valleys, but pre-Little Ice Age moraines are common in all sectors of the Arctic; 5) moraine sequences on both Baffin Island and western Greenland surprisingly date to Medieval time. Key implications of this pattern of Holocene glaciation in the Arctic will be discussed.