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The Northwest Coast of North America stretches 4000 km from Bering Strait to Washington State. Here we review the history of glaciation, sea level, oceanography, and climate along the Northwest Coast and in the subarctic Pacific Ocean during the Last Glacial Maximum and deglaciation. The period of interest is Marine Isotope Stage 2 between ca. 29,000 calendar years ago (29 ka) and 11,700 calendar years ago (11.7 ka). The glacial history of the Northwest Coast involved multiple glacial systems responding independently to latitudinal variations in climate caused by changes in the North American ice sheets and in the tropical ocean-atmosphere system. Glaciers reached their maximum extents 1–5 kyrs later along the Northwest Coast than did large sectors of the Laurentide and Fennoscandian Ice Sheets. Local, Last Glacial Maxima were reached in a time-transgressive, north to south sequence between southwestern Alaska and Puget Sound. The history of relative sea level along the Northwest Coast during Marine Isotope Stage 2 was complex because of rapid isostatic adjustments by a thin lithosphere to these time-transgressive glacial fluctuations. Multiple lines of evidence suggest Bering Strait was first flooded by the sea after 11 ka and that it probably did not assume its present-day oceanographic functions until after 9 ka. The coldest intervals occurred during Heinrich Event 2 (ca. 26–23.5 ka), again between ca. 23 and 21.5 ka, and during Heinrich Event 1 (ca. 18–15 ka). During these times, mean annual sea surface temperatures cooled by 5o to 8o C in the Gulf of Alaska, and glacial equilibrium-line altitudes fell below present sea level in southern Alaska and along the Aleutian Island chain. Sea ice episodically expanded across the subarctic Pacific in winter. Oceanographic changes in the Gulf of Alaska tracked variations in the vigor of the Asian Summer Monsoon. The deglaciation of the Northwest Coast may have served as the trigger for global climate changes during deglaciation. Starting ca. 21 ka, marine-based glaciers there were increasingly destabilized by rising eustatic sea level and influxes of freshwater and heat associated with the rejuvenation of the Asian Summer Monsoon. Rapid retreat of marine-based glaciers began ca. 19 ka and released large numbers of ice bergs and vast amounts of freshwater into the Northeast Pacific. Resultant cooling of the North Pacific may have been teleconnected to the North Atlantic through the atmosphere, where it slowed Atlantic Meridional Overturning Circulation and initiated the global effects of Heinrich Event 1, ca. 18–15 ka. During the Younger Dryas, ca. 12.8–11.7 ka, mean annual sea surface temperatures were 4o to 6o C cooler than today in the Gulf of Alaska, and sea ice again expanded across the subarctic Pacific in winter. Conditions of extreme seasonality characterized by cold, dry winters and warm, steadily ameliorating summers caused by the southward diversion of the Aleutian Low in winter may explain the previously enigmatic records of Younger Dryas climate along the Northwest Coast.
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This content will become publicly available on July 1, 2026
Spatiotemporal Trends in Winter Wind Chill Temperatures across Canada and the United States
Abstract Wind chill temperature (WCT) is a widely recognized biometeorological variable that quantifies atmospheric conditions that have consequential impacts on many aspects of society, especially human health through exposure to winter conditions that can result in hypothermia, frostbite, and cardiorespiratory mortality. The spatial and temporal variations in WCT and extreme WCT (E WCT) (coldest 1%) were examined using hourly surface measurements collected at 133 stations across Canada and the United States during 40 winters (1979/80–2018/19). Most locations experienced an overall warming in both mean and extreme WCTs. The most substantial and statistically significant warming of mean WCT occurred across Alaska and the Canadian Northwest Territories with values of +3.2° to +6.4°C during the 40-winter time period. Statistically significant warming of mean WCT also occurred along the East Coast of Canada and the United States, as well as across the southeastern United States. Extreme WCT was found to be 10°–30°C colder than the mean WCT, and generally, the extreme WCT warmed at a greater rate than the mean WCT at locations. For example, extreme WCT warmed as much as +10.4°C during the 40-winter time period across portions of Alaska and the Canadian Northwest Territories. Warming air temperatures were found to have a large relative contribution to warming of mean and extreme WCTs with a smaller contribution coming from decreasing wind speeds (WS).
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- Award ID(s):
- 1947703
- PAR ID:
- 10631286
- Publisher / Repository:
- American Meteorological Society
- Date Published:
- Journal Name:
- Journal of Applied Meteorology and Climatology
- Volume:
- 64
- Issue:
- 7
- ISSN:
- 1558-8424
- Page Range / eLocation ID:
- 813 to 829
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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