Late-Holocene diatom derived seasonal variability in hydrological conditions off Disko Bay, West Greenland

摘要

A decadally resolved diatom record from a sediment core collected from Disko Bay, central West Greenland, reveals variations in hydrological conditions for the late Holocene. The diatom flora record two clear trends in surface water temperatures: a pronounced cooling of surface waters during the Medieval Climate Anomaly (MCA) and a progressive warming in surface waters during the Little Ice Age (LIA), previously identified in North Atlantic studies. Our data support the existence of a previously identified anti-phase relationship between surface water temperatures off West Greenland and climate events recorded in the north-east Atlantic. The diatom assemblages show relatively cool surface water conditions during warmer climatic intervals, e.g. 3.6-2.7 cal. ka BP, the MCA, while relatively warm surface water conditions during colder climatic periods, e.g. the Dark Ages (DA) and the LIA. The exception to this is the Roman Warm Period (RWP), which in West Greenland shows warmer surface waters and climatic conditions. Our data also show the existence of anti-phase relationship between surface and sub-surface water temperatures in Disko Bay during the interval 3.6-2.7 cal. ka BP (cooler surface with warmer subsurface waters) and towards the end of the LIA (warmer surface and cooler sub-surface waters). These anti-phases patterns are possibly linked to: 1) the local spring-summer hydrological conditions (e.g. warmer climatic intervals), such as meltwater flux from sea ice/continental ice and water stratification, and 2) large-scale ocean-climate interactions (e.g. cooler climatic intervals) within the North Atlantic Oscillation (NAO)-type climate see-saw between West Greenland and north-west Europe associated with variability in the Atlantic Meridional Overturning Circulation (AMOC).