Younger Dryas cooling and the Greenland climate response to CO2.
Greenland ice-core δ(18)O-temperature reconstructions suggest a dramatic cooling during the Younger Dryas (YD; 12.9-11.7 ka), with temperatures being as cold as the earlier Oldest Dryas (OD; 18.0-14.6 ka) despite an approximately 50 ppm rise in atmospheric CO(2). Such YD cooling implies a muted Greenland climate response to atmospheric CO(2), contrary to physical predictions of an enhanced high-latitude response to future increases in CO(2). Here we show that North Atlantic sea surface temperature reconstructions as well as transient climate model simulations suggest that the YD over Greenland should be substantially warmer than the OD by approximately 5 °C in response to increased atmospheric CO(2). Additional experiments with an isotope-enabled model suggest that the apparent YD temperature reconstruction derived from the ice-core δ(18)O record is likely an artifact of an altered temperature-δ(18)O relationship due to changing deglacial atmospheric circulation. Our results thus suggest that Greenland climate was warmer during the YD relative to the OD in response to rising atmospheric CO(2), consistent with sea surface temperature reconstructions and physical predictions, and has a sensitivity approximately twice that found in climate models for current climate due to an enhanced albedo feedback during the last deglaciation.
Center for Climatic Research and Department Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA. zliu3@wisc.edu
Zhengyu
Z
Liu
Anders E
AE
Carlson
Feng
F
He
Esther C
EC
Brady
Bette L
BL
Otto-Bliesner
Bruce P
BP
Briegleb
Mark
M
Wehrenberg
Peter U
PU
Clark
Shu
S
Wu
Jun
J
Cheng
Jiaxu
J
Zhang
David
D
Noone
Jiang
J
Zhu
D001110:Arctic Regions; D001272:Atmosphere; D002245:Carbon Dioxide / Q000737:chemistry*; D002980:Climate; D003080:Cold Temperature; D019015:Geologic Sediments; D057232:Global Warming; D017752:Greenhouse Effect; D006116:Greenland; D007053:Ice; D007554:Isotopes / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D012623:Seawater; D013696:Temperature
D007053:Ice; D007554:Isotopes; D002245:Carbon Dioxide; D010100:Oxygen