AN ANNUALLY RESOLVED 3Ka RECORD OF LANDSCAPE ALTERATION, CLIMATE, AND ICE SHEET ACTIVITY FROM GLACIAL LAKE HVITARVATN, ICELAND

A major goal of current Arctic research is to understand the causes and scope of natural climate variability and associated feedbacks that lead to distinct system changes. It is widely accepted that 20th century warming has had the most profound effects in high northern latitudes, where strong positive feedbacks amplify global or hemispheric forcings. Because direct records are limited, high-resolution proxy records of past climates are necessary to place the recent warming within the context of longer-term trends and to comprehend the sensitivity of the arctic system to human impacts. The goal of this project is to use varved lake sediments from proglacial lake Hvítárvatn to produce an annually resolved record of late Holocene ice-sheet activity in Iceland. Hvítárvatn is a large, glacially dominated lake situated beneath Langjökull, the second largest icecap in Iceland. In 2003, four long cores spanning the last 10ka were recovered from the northern basin of Hvítárvatn. All of the cores exhibit beautifully preserved laminations as well as multiple diagnostic tephra layers. Using tephrochronology and cross-correlating techniques on distinctive tephra and laminae patterns, the cores have been linked across the basin and it was found that the lake contains annually laminated varves. It has been demonstrated that the varve record (sediment flux to lake) in this system is broadly controlled by the activity of Langjökull and the two outlet glaciers that drain into the lake. In this manner, cold times are reflected in the sediment record due to glacier growth and erosion to the bedrock resulting in thicker varves. Physical and biological proxies associated with these sediments (including ice-rafted debris, C:N, δ13C, and varve thickness) record local and regional climate fluctuations and environmental conditions with unprecedented resolution.

A project focus is the transition into and out of Little Ice Age (LIA) and the regional effects of explosive volcanism on the catchment environment and regional climate.