Holocene records of marine-terrestrial palynomorphs from the Chukchi Sea shelf sediments, western Arctic Ocean

Abstract

Palynomorphs preserved in sedimentary archives represent one of the most useful tools in reconstruction of past environmental and climatic changes. In particular, records of marine-terrestrial palynomorphs such as dinoflagellate cysts, pollen, spores and freshwater algae in the Chukchi-Alaskan sea shelf sediments are suggested to be important and under-exploited palaeoclimate archives, potentially inferring the opening of the Bering Strait and the onset of high riverine inputs to the shelf region since the last deglaciation. In this study, we present new marine-terrestrial palynomorph records from the Chukchi-Alaskan shelf sediments in order to understand flooding events over the Chukchi-Alaskan shelves and the opening of the Bering Strait since the last deglaciation, as well as major vegetational changes over the western Arctic region covering the Chukchi Peninsula and northwest Alaska. Using a radiocarbon-dated sediment core, we demonstrate changes in characteristics of the palynomorph records and discuss their possible source areas with its transportation mechanisms. We speculate that drastic changes in concentration of pollen and spores indicates considerable changes in vegetation over the catchment area including the territories of both North America (Alaska and Northern Canadian Arctic) and Northern Siberia (Chukotka peninsula and Northern East-Siberian coast) during the last 10 kyr BP. In parallel, dinoflagellate cyst records document significant changes in the marine environments, typically for a prominent increase in dinoflagellate cyst concentrations concomitant with high total organic carbon and nitrogen contents since the early Holocene suggesting increased nutrient inputs and marine productivity in the study area.