Abstract
At Phalarope Pond, western Kodiak Island, a multidisciplinary study using pollen and spores, macrofossils, stable isotopes, and carbon accumulation provides the Holocene vegetation and climate history following the deglaciation that began over 16,000 cal years ago (yr BP) [years Before Present, as calibrated from 1950]. Following a cold and dry Younger Dryas, a warm and wet early Holocene was characterized by abundant ferns in a sedge tundra environment with maximum carbon accumulation, similar to high latitude peatlands globally. About 8,700 cal yr BP sedge and ferns declined and climate remained warm as drier conditions prevailed, limiting carbon sequestration. The abrupt shift in D/H (Deuterium/Hydrogen) isotopes of about 60 percent indicates a shift to cooler conditions or a more distal moisture source. Neoglaciation beginning about 3,700 cal yr BP is evident from increases in Artemisia, Empetrum and Betula, signifying cooler conditions, while Alnus declines, paralleling regional trends.
Highlights
Peatlands in subarctic Alaska provide a window into the history of a high latitude area that today is warming almost twice as fast as the rest of the globe (Cohen et al, 2014)
While we previously identified Kodiak Island as an area that experienced a marked Younger Dryas cooling during the late-glacial (Peteet and Mann, 1994; Hadjas et al, 1998) using pollen and macrofossils, we use these same vegetational indicators along with stable isotope to explore the vegetational, climatic, and carbon accumulation history throughout the Holocene from the same site
Alnus appears to expand its range into southwestern Kodiak Island in response to early Holocene warmth
Summary
Peatlands in subarctic Alaska provide a window into the history of a high latitude area that today is warming almost twice as fast as the rest of the globe (Cohen et al, 2014). Describing the Holocene history of this region and its impact on carbon sequestration becomes increasingly important as we experience this warming. While we previously identified Kodiak Island as an area that experienced a marked Younger Dryas cooling during the late-glacial (Peteet and Mann, 1994; Hadjas et al, 1998) using pollen and macrofossils, we use these same vegetational indicators along with stable isotope to explore the vegetational, climatic, and carbon accumulation history throughout the Holocene from the same site. Deglaciation occurred ca. 14,700 14C years BP (Mann and Peteet, 1994; Peteet and Mann, 1994)
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