North-south dipole in winter hydroclimate in the western United States during the last deglaciation

Abstract

During the termination of the last glacial period the western U.S. experienced exceptionally wet conditions, driven by changes in location and strength of the mid-latitude winter storm track. The distribution of modern winter precipitation is frequently characterized by a north-south wet/dry dipole pattern, controlled by interaction of the storm track with ocean-atmosphere conditions over the Pacific and Atlantic Oceans. Here we show that a dipole pattern of similar geographic extent persisted and switched sign during millennial-scale abrupt climate changes of the last deglaciation, based on a new lake level reconstruction for pluvial Lake Chewaucan (northwestern U.S.), and a compilation of regional paleoclimate records. This suggests the dipole pattern is robust, and one mode may be favored for centuries, thereby creating persistent contrasting wet/dry conditions across the western U.S. The TraCE-21k climate model simulation shows an equatorward enhancement of winter storm track activity in the northeastern Pacific, favoring wet conditions in southwestern U.S. during the second half of Heinrich Stadial 1 (16.1–14.6 ka) and consistent with paleoclimate evidence. During the Bølling/Allerød (14.6–12.8 ka), the northeastern Pacific storm track contracted poleward, consistent with wetter conditions concentrated poleward toward the northwest U.S.

Climate during the Last Glacial Maximum in the Northern Sawatch Range, Colorado, USA

“…More local modulations were likely idiosyncratic, having caused asynchronous glacier response within a restricted geographical area. In contrast, regional changes in hydroclimate, that are evident in a variety of climate proxies [15][16][17][18][19][20][21][22][23], arguably played a more dominant role in regional asynchrony of glacier behavior. While the exact cause and abruptness of these changes is debated [18,[24][25][26][27][28][29], all are dependent on reorganization of atmospheric circulation because of the growth and decay of the Laurentide Ice Sheet.…”

Multidecadal Climate Variability in the Southern Region of the California Current System During the Last 1,800 Years

“…The effects that changes in the pole‐equator temperature gradient have over the latitudinal position and meandering of the polar jet stream, the North Pacific High, and the westerly storm track have been broadly assessed at different time scales (An et al, ; Archer & Caldeira, ; COHMAP, ; Hudson et al, ; Ji et al, ; Oster et al, ; Routson et al, ; Rykaczewski et al, ). Cold (warm) conditions drive southward (northward) the polar vortex, the North Pacific High, and the westerlies path, which would further affect the NPC and the latitudinal position of its bifurcation when it reaches the continent.…”

Ground Penetrating Radar Investigation of Late Pleistocene Shorelines of Pluvial Lake Clover, Elko County, Nevada, USA

“…Previous work has proposed a variety of mechanisms for the increased effective moisture in the Great Basin that drove pluvial lakes to their late Pleistocene highstands. Whether this moisture was a response to southward deflection of the prevailing storm track by the Laurentide Ice Sheet [28][29][30], steering of storms inland from the Pacific [31], or even a response to northward moisture transport [32], remains a topic of debate. What is clear, however, is the synchrony of many lake highstands across the entire latitudinal sweep of the Great Basin with Heinrich Stadial I (H1) in the North Atlantic region [20,23].…”