HR: 08:45h
AN: PP11A-04    [Abstracts]
TI: Arctic Amplification: Can the Past Constrain the Future?
AU: * Miller, G H
EM: gmiller@colorado.edu
AF: INSTAAR and Geological Sciences, University of Colorado, Boulder, CO 80309, United States
AU: Brigham-Grette, J
EM: juliebg@geo.umass.edu
AF: Geosciences, University of Massachusetts, Amherst, MA 02115, United States
AU: Alley, R B
EM: ralley@geosc.psu.edu
AF: Geosciences, Pennsylvania State University, University Park, PA 16802, United States
AB: Arctic climate is influenced by a suite of strong positive feedbacks, particularly changes in sea ice and snow cover (fast) and terrestrial ice sheets (slow). Similarly strong negative feedbacks that might stabilize Arctic climate are not known, so physical understanding indicates that climate changes should be amplified in the Arctic relative to lower latitudes. Arctic amplification in the contemporary world is nearly universal in climate model simulations forced by increasing concentrations of greenhouse gases, but its magnitude is poorly constrained. Past times when the Arctic was unusually warm or cold, due primarily to various combinations of insolation (Insol) and greenhouse gas (GHG) forcings, may inform the debate over the magnitude of Arctic amplification. Arctic summer temperature anomalies can be compared to the Northern Hemisphere average anomalies for the Holocene thermal maximum (HTM; Insol), last glacial maximum (LGM; Insol and GHG), and last interglacial (LIG; Insol and weak GHG) because of the similar forcing across the Northern Hemisphere, whereas the warmth of the Middle Pliocene (MP; mostly GHG) may be compared with hemispheric or global averages. HTM summer temperature anomalies have been summarized recently for much of the Arctic, indicating an Arctic warming of +1.7 +/- 0.8 C, compared to a Northern Hemisphere warming of +0.5 +/- 0.3 C. Similarly, the temperature anomaly for LGM Arctic cooling was -18 +/- 7 C, whereas Northern Hemisphere cooling was -5 +/- 2 C, LIG Arctic warmth was +5 +/- 1 C whereas Northern Hemisphere warmth was +1 +/- 1 C, and MP Arctic warmth was +12 +/- 3 C, whereas hemispheric and global warmth was 4 +/- 2 C. Within the stated uncertainties these paleoreconstructions are consistent with an Arctic amplification of ca. 3.5 times the hemispheric average anomaly, despite a wide range of forcings and variable contributions from slow and fast feedbacks. Because these feedbacks are still active, it is likely that future Arctic amplification will be of a similar magnitude.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2009 Joint Assembly