Oceanographic change and terrestrial human impacts in a post AD 1400 sediment record from the southwest Iceland shelf

Environmental proxies of soil erosion on Iceland, and oceanographic conditi ons on the adjacent shelf, were measured on a 50 cm box core taken from the southwest Iceland shelf in 1993 during cruise 93030 of the Canadian ship, CSS Hudson. These data, covering the last several centuries, are compared w ith the documentary record of sea-ice changes around Iceland since A.D. 160 0. The site is under the influence of The Irminger Current, which carries w arm, saline, Atlantic water northward along the shelf. Because of the relat ive warmth of this current, sea ice rarely occurs off southwest Iceland, ev en during the most severe sea-ice intervals of the historical record. In se vere sea-ice years, however, the ice drifts clockwise around Iceland from t he northeast and east and, in rare cases, reaches the southern coasts (Ogil vie, 1992). The chronology of the core was established by converting the ba sal radiocarbon date to calendar years and assuming a linear sedimentation rate from the base of the core to the year of collection, 1993. Organic car bon, stable C and O istotope ratios, planktonic foraminiferal assemblages, and sediment magnetic parameters were measured on samples from the core, pl otted against calendar years and compared to the Icelandic sea-ice index. T he environmental proxies suggest that increased soil erosion, reduced salin ity, and, possibly, decreased marine productivity prevailed during the seve re sea-ice interval lasting from the last quarter of the eighteenth century to around 1920. Such a situation could develop with climatic cooling, incr eased storminess, and toss of vegetation cover to stabilise the soil. Altho ugh the core site generally lies outside the sea-ice limits, the evidence c learly shows the influence of sea ice and fresh water, and is sensitive to the overall climatic deterioration manifested by the sea-ice record.