A pan-Arctic review of lake-based Holocene glacier and ice cap records

Abstract:

More than one third of the world’s ~200,000 glaciers and ice caps (GICs) lie in the northern high latitudes. Recent observations have confirmed that arctic GICs respond sensitively and quickly, on decadal to centennial timescales, to changes in summer temperature and to a lesser extent, accumulation season precipitation. Accordingly, knowledge of their past fluctuations offers insights into past climate conditions. Yet, relatively little is known about GIC fluctuations in the Arctic during the Holocene. The majority of evidence of past GIC variations is fragmentary because recent ice advances have destroyed geomorphic evidence (e.g., moraines) from earlier in the Holocene. However, measurements of physical and geochemical properties of glacial lake sediments serve as continuous records of GIC presence and absence in the landscape, as well as more subtle variations in their size over time.

Recent paleoclimate syntheses have highlighted spatial and temporal asymmetries in peak Holocene warmth during the insolation-driven Holocene Thermal Maximum across the Arctic. As a continuous and relatively straightforward qualitative proxy for summer temperature, records of GIC fluctuations from lake sediments reliably capture the timing of warmer than present conditions. Here we synthesize >50 published continuous, lake-based GIC records from the Arctic spanning the Holocene that capture evidence for when GICs were smaller than today or absent. Our review covers seven geographical regions above 58°N from which such records are available: GICs peripheral to the Greenland Ice Sheet, thearchipelagos of the eastern Canadian Arctic, the Russian high Arctic, Alaska, Iceland, the Scandinavian peninsula, and Svalbard. For each region, we summarize when GICs were smaller than present or absent, indicating warmer than present conditions, as well as the timing of GIC advances in the late Holocene documented in lake records. Improved understanding of the patterns of early-to-middle Holocene warming holds significance for resolving data-model discrepancies and for better anticipating the consequences of future Arctic warming.