PALEOENVIRONMENTAL RECORDS OF DIATOM ON NORTH ICELAND SHELF SINCE LAST DEGLACIATION

The sustaining increase in warm diatoms and the continuing reduction in cold diatoms found from the core MD99-2271 on the North Iceland shelf reveal a warming trend of climate in this area during the time of 14.6~3 cal.kaBP. The periodic counter-balance of these two types of diatoms in the diatom assemblages may indicate the temperature variation on the background of climate warming. The reconstructed paleoenvironment of the North Iceland shelf by the Rw/wc, which may indicate the temperature changes of seawater, can roughly be divided into five stages since the last deglaciation. During the warm Bølling-Allerød period, relatively high abundance of warm-water species T. nitzschioides suggested that the Atlantic water, presumably related to the strength of the Irminger Current, had an even stronger influence on the North Icelandic shelf. Increased abundance of sea-ice diatom species (F. cylindrus and T. bulbosa) indicate a significant increase in the influence of East Greenland Current during 12.8~11.5 cal.kaBP. This coincides with the coldest period since the last deglaciation (Younger Dryas event). The present-day oceanographic current system in this area was established at the transition to Holocene. Between 10.2~6 cal.kaBP, there was a significant increase in warm-water species (T. nitzschioides and T. oestrupii), and a marked decline of sea-ice species and cold water species. This suggests a period of enhanced influence of the Irminger current on the North Icelandic shelf, corresponding in time to the Holocene climatic optimum. Finally, the influence of the East Greenland Current became stronger at the end of the Holocene Climate Optimum, which led to the sea water temperature dropping.