Diatom evidence of hydrographic changes and ice conditions in Igaliku Fjord, South Greenland, during the past 1500 years

Biostratigraphic diatom analyses were carried out on two sediment cores from Igaliku Fjord, South Greenland, in order to reconstruct hydrographic and climatic fluctuations during the late Holocene (AD 550 to present). Pronounced differences in hydrographic setting of the coring sites provide palaeoenvironmental information of both local and more regional character. Five diatom zones were identified from the subfossil diatom records, each describing a hydrographic setting. Two major climate periods, the 'Mediaeval Warm Period' (AD 800-1250) and the 'Little Ice Age' (AD 1580-1850), that were separated by a variable transitional period, were recognized. Prior to these periods, a cold and presumably moist climate regime prevailed between AD 500 and 700. Cooling events were identified during the 'Mediaeval Warm Period' in the period AD 960 to 1140. The diatom data demonstrate that marked hydrographic changes occurred in the course of a relatively short timespan beginning at about AD 1300 and culminating around AD 1500. These changes occur during a crucial period in which the Norse are believed to have disappeared from South Greenland. Thus, our results support the hypothesis proposing that one of the main reasons for the loss of the Norse settlements was climatic deterioration.