Seasonal temperature reconstructions on the north Icelandic shelf : evidence from stable isotope values of marine bivalves

Abstract

Recent episodes of extreme weather and the drastic consequences they can have for ecosystems, societies, and economies, emphasize the need for a better understanding of Earth’s climate. In order to gain a better understanding of modern and future climate, a more thorough knowledge of past climates at the highest resolution possible from different regions is necessary. To this end, a study of seasonal temperature variability in the waters off the northern coast of Iceland was undertaken. Twenty-six bivalves were selected from marine sediment cores recovered from the northern and northwestern coasts of Iceland. Bivalves were selected from intervals of climatic interest as determined from sedimentological characteristics. Shells were micromilled and the carbonate analysed for stable oxygen and carbon isotope values. Oxygen isotope values are driven principally by the temperature of the water from which the shell was precipitated. These data provide a time-series of discrete climate profiles of seasonal temperature variations from c. 360 cal yr BC to cal yr AD 1660, each recording 2 to 9 consecutive years of temperature variability. Several notable warm and cold periods were identified and characterized in terms of maximum and minimum temperatures. As this period overlaps the Viking Age (c. 790 to 1070) and the establishment of Norse colonies in Iceland and Greenland, the temperature record was compared with historical records and demonstrates the significant impact of variation in temperature seasonality on the establishment, development, and in some cases, collapse of societies in the North Atlantic.