North Pacific seasonality and the glaciation of North America 2.7 million years ago.
In the context of gradual Cenozoic cooling, the timing of the onset of significant Northern Hemisphere glaciation 2.7 million years ago is consistent with Milankovitch's orbital theory, which posited that ice sheets grow when polar summertime insolation and temperature are low. However, the role of moisture supply in the initiation of large Northern Hemisphere ice sheets has remained unclear. The subarctic Pacific Ocean represents a significant source of water vapour to boreal North America, but it has been largely overlooked in efforts to explain Northern Hemisphere glaciation. Here we present alkenone unsaturation ratios and diatom oxygen isotope ratios from a sediment core in the western subarctic Pacific Ocean, indicating that 2.7 million years ago late-summer sea surface temperatures in this ocean region rose in response to an increase in stratification. At the same time, winter sea surface temperatures cooled, winter floating ice became more abundant and global climate descended into glacial conditions. We suggest that the observed summer warming extended into the autumn, providing water vapour to northern North America, where it precipitated and accumulated as snow, and thus allowed the initiation of Northern Hemisphere glaciation.
Haug
Gerald H
GH
Geoforschungszentrum Potsdam (GFZ), 14473 Potsdam, Germany. haug@gfz-potsdam.de
Ganopolski
Andrey
A
Sigman
Daniel M
DM
Rosell-Mele
Antoni
A
Swann
George E A
GE
Tiedemann
Ralf
R
Jaccard
Samuel L
SL
Bollmann
Jörg
J
Maslin
Mark A
MA
Leng
Melanie J
MJ
Eglinton
Geoffrey
G
D001110:Arctic Regions; D003081:Cold Climate; D017377:Diatoms / Q000737:chemistry / Q000378:metabolism; D019015:Geologic Sediments / Q000737:chemistry; D049690:History, Ancient; D046448:Ice Cover; D010100:Oxygen / Q000032:analysis; D010140:Pacific Ocean; D012621:Seasons; D012623:Seawater / Q000737:chemistry; D012914:Snow; D013696:Temperature; D013997:Time Factors
D010100:Oxygen