Marine-terrestrial interaction of climate changes in the western Arctic region over the last 10,000 years

Abstract

Marine-terrestrial palynomorph records such as dinoflagellate cysts, pollen, spores and freshwater algae in marine sedimentary archives document paleoclimate conditions, inferring the past terrestrial environment and sea surface conditions such as sea surface temperature, sea surface salinity and sea ice extent. In this study, we present marine-terrestrial palynomorph records of sediment cores from the Chukchi-Alaskan shelf sediments (core ARA01B/01A-GC and HLY0501-05) in order to understand the paleoenvironmental history of the western Arctic region in relation to the Holocene climatic changes associated with the opening of the Bering Strait and its influence over the regional environmental system. Using a radiocarbon-dated sediment core, we demonstrate changes in characteristics of the palynomorph records and discuss their possible source areas as well as its transport mechanisms from land to the ocean. Our terrestrial palynomorph records indicate a major environmental change from the early Holocene to the mid-to-late Holocene environments in the Chukchi Sea shelf regions. Considerable changes in the western Arctic vegetation are indicated by the percentage ratio between tree-herb pollen and spores, and the freshwater algae Pediastrum, notably between ~8-4 ka BP, at around 5 ka BP and 3 ka BP. In paralell, dinoflagellate cyst concentrations show a pronounced increase after ca. 8 ka BPsuggesting a major transition to a full-oceanic environment in respond to the sea-level rise and increased nutrient availability in relation with the Pacific water inflow via Bering Strait. A prominent shift in assemblage compositions from a dominance of Brigantedinium taxa to Pentapharsodinium dalei taxa at around 5 ka BP indicates a significant transition in oceanic environmental conditions in the Chukchi Sea shelf region.