Abstract. Investigating North Pacific climate variability during warmintervals prior to the Common Era can improve our understanding of thebehavior of ocean–atmosphere teleconnections between low latitudes and theArctic under future warming scenarios. However, most of the existing icecore records from the Alaskan and Yukon region only allow access to climateinformation covering the last few centuries. Here we present asurface-to-bedrock age scale for a 210 m long ice core recovered in 2013from the summit plateau of Begguya (Mt. Hunter; Denali National Park,Central Alaska). Combining dating by annual layer counting with absolutedates from micro-radiocarbon dating, a continuous chronology for the entireice core archive was established using an ice flow model. Calibrated14C ages from the deepest section (209.1 m, 7.7 to 9.0 ka cal BP)indicate that basal ice on Begguya is at least of early Holocene origin. Aseries of samples from a shallower depth interval (199.8 to 206.6 m) weredated with near-uniform 14C ages (3 to 5 ka cal BP). Our resultssuggest this may be related to an increase in annual net snow accumulationrates over this period following the Northern Hemisphere Holocene ClimateOptimum (around 8 to 5 kyr BP). With absolute dates constraining thetimescale for the last >8 kyr BP, this paleo-archive will allowfuture investigations of Holocene climate and the regional evolution ofspatial and temporal changes in atmospheric circulation and hydroclimate inthe North Pacific.
Arctic Alaska lies at a climatological crossroads between the Arctic and North Pacific Oceans. The modern hydroclimate of the region is responding to rapidly diminishing sea ice, driven in part by changes in heat flux from the North Pacific. Paleoclimate reconstructions have improved our knowledge of Alaska’s hydroclimate, but no studies have examined Holocene sea ice, moisture, and ocean−atmosphere circulation in Arctic Alaska, limiting our understanding of the relationship between these phenomena in the past. Here we present a sedimentary diatom assemblage and diatom isotope dataset from Schrader Pond, located ∼80 km from the Arctic Ocean, which we interpret alongside synthesized regional records of Holocene hydroclimate and sea ice reduction scenarios modeled by the Hadley Centre Coupled Model Version 3 (HadCM3). The paleodata synthesis and model simulations suggest the Early and Middle Holocene in Arctic Alaska were characterized by less sea ice, a greater contribution of isotopically heavy Arctic-derived moisture, and wetter climate. In the Late Holocene, sea ice expanded and regional climate became drier. This climatic transition is coincident with a documented shift in North Pacific circulation involving the Aleutian Low at ∼4 ka, suggesting a Holocene teleconnection between the North Pacific and Arctic. The HadCM3 simulations reveal that reduced sea ice leads to a strengthened Aleutian Low shifted west, potentially increasing transport of warm North Pacific water to the Arctic through the Bering Strait. Our findings demonstrate the interconnectedness of the Arctic and North Pacific on multimillennial timescales, and are consistent with future projections of less sea ice and more precipitation in Arctic Alaska.
more » « less- NSF-PAR ID:
- 10204816
- Publisher / Repository:
- Proceedings of the National Academy of Sciences
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 117
- Issue:
- 52
- ISSN:
- 0027-8424
- Page Range / eLocation ID:
- p. 33034-33042
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Investigation of North Pacific climate variability during warm intervals outside of the Common Era is essential for addressing questions regarding ocean-atmosphere teleconnections between low latitudes and the Arctic under future warming scenarios. However, most of existing ice cores extracted from Alaska/Yukon region archive climate information from the last few centuries. This dataset contains radiocarbon (14C) data from a 208 meter surface-to-bedrock ice core recovered from the summit plateau of Mt. Hunter in central Alaska in 2013. By applying radiocarbon dating on carbonaceous aerosols, a continuous depth-age relationship has been established in the Mt. Hunter ice core. Calibrated 14C ages from the two lowest samples (7,946-10,226 cal BP and 7,018-7,975 cal BP) indicate that basal ice on Mt. Hunter has an early Holocene (> 8 kyr) origin. We also show that samples from depth of 161.0-166.1 m weq have nearly uniform 14C ages (3,200 to 3,500 cal BP). One possible explanation is an increase in snow accumulation at Mt. Hunter during regional neoglaciation. When paired with the Mt. Logan PRCol record, the only other Holocene-length ice core from North Pacific region, the Mt. Hunter ice core provides the possibility to investigate spatial changes in high-elevation Holocene hydroclimate.more » « less
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