Terrigenous input to a fjord in central Norway records the environmental response to the North Atlantic Oscillation over the past 50 years

Abstract

During the last century, both earth surface temperature and moisture transport towards high latitudes have increased rapidly. The response of the sub-arctic region to these changes in terms of weathering, transport and delivery of terrigenous material towards the coastal and deep ocean is both complex and poorly understood. Sediments accumulating in fjords offer an excellent opportunity for studying such land–ocean interactions and may provide ultra-high-resolution records of environmental response to short-term climate variability. As a basis for Holocene climate change studies, modern sources, supply and distribution of particular sediment components in the Trondheimsfjord have been investigated and imply lithogenic elements as a promising proxy for terrigenous input and river discharge. To better understand the impact of atmospheric variability on central Norwegian environment, we examine instrumental time series and show that the dominant mode of the atmospheric circulation in the North Atlantic region, the North Atlantic Oscillation (NAO), has a strong impact on river discharge, temperature and precipitation in central Norway. In addition, elemental composition analysis of a short sediment core reveals that from 1959 to 2010, winter precipitation and temperature changes are recorded by changes in the inorganic geochemical composition of Trondheimsfjord sediments. Elemental ratios of Al/Zr and K/Ni in the sediment core MC99-3 show a close relation to small-scale, high frequency climate variations and large-scale changes in the Northern Hemisphere climate. This implies that terrigenous input and related erosional processes in the fjord hinterland are highly sensitive to atmospheric circulation variability in the North Atlantic region. By comparing our results with NAO records derived from ice accumulation rates of Norwegian glaciers, western Greenland ice sheets and river discharge anomalies in the Eurasian Arctic, we show that it is possible to reconstruct the NAO from sedimentary archives in central Norwegian fjords.