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Ewing, RC, Eisenman I, Lamb MP, Poppick L, Maloof AC, Fischer WW.  2014.  New constraints on equatorial temperatures during a Late Neoproterozoic snowball Earth glaciation. Earth and Planetary Science Letters. 406:110-122.   10.1016/j.epsl.2014.09.017   AbstractWebsite

Intense glaciation during the end of Cryogenian time (similar to 635 million years ago) marks the coldest climate state in Earth history - a time when glacial deposits accumulated at low, tropical paleolatitudes. The leading idea to explain these deposits, the snowball Earth hypothesis, predicts globally frozen surface conditions and subfreezing temperatures, with global climate models placing surface temperatures in the tropics between -20 degrees C and -60 degrees C. However, precise paleosurface temperatures based upon geologic constraints have remained elusive and the global severity of the glaciation undetermined. Here we make new geologic observations of tropical periglacial, aeolian and fluvial sedimentary structures formed during the end-Cryogenian, Marinoan glaciation in South Australia; these observations allow us to constrain ancient surface temperatures. We find periglacial sand wedges and associated deformation suggest that ground temperatures were sufficiently warm to allow for ductile deformation of a sandy regolith. The wide range of deformation structures likely indicate the presence of a paleoactive layer that penetrated 2-4 m below the ground surface. These observations, paired with a model of ground temperature forced by solar insolation, constrain the local mean annual surface temperature to within a few degrees of freezing. This temperature constraint matches well with our observations of fluvial deposits, which require temperatures sufficiently warm for surface runoff. Although this estimate coincides with one of the coldest near sea-level tropical temperatures in Earth history, if these structures represent peak Marinaon glacial conditions, they do not support the persistent deep freeze of the snowball Earth hypothesis. Rather, surface temperatures near 0 degrees C allow for regions of seasonal surface melting, atmosphere-ocean coupling and possible tropical refugia for early metazoans. If instead these structures formed during glacial onset or deglaciation, then they have implications for the timescale and character for the transition into or out of a snowball state. (C) 2014 Elsevier B.V. All rights reserved.

Eisenman, I.  2012.  Factors controlling the bifurcation structure of sea ice retreat. Journal of Geophysical Research-Atmospheres. 117   10.1029/2011jd016164   Website
Eisenman, I, Meier WN, Norris JR.  2014.  A spurious jump in the satellite record: has Antarctic sea ice expansion been overestimated? The Cryosphere. 8:1289-1296.: Copernicus Publications   10.5194/tc-8-1289-2014   AbstractWebsite

Recent estimates indicate that the Antarctic sea ice cover is expanding at a statistically significant rate with a magnitude one-third as large as the rapid rate of sea ice retreat in the Arctic. However, during the mid-2000s, with several fewer years in the observational record, the trend in Antarctic sea ice extent was reported to be considerably smaller and statistically indistinguishable from zero. Here, we show that much of the increase in the reported trend occurred due to the previously undocumented effect of a change in the way the satellite sea ice observations are processed for the widely used Bootstrap algorithm data set, rather than a physical increase in the rate of ice advance. Specifically, we find that a change in the intercalibration across a 1991 sensor transition when the data set was reprocessed in 2007 caused a substantial change in the long-term trend. Although our analysis does not definitively identify whether this change introduced an error or removed one, the resulting difference in the trends suggests that a substantial error exists in either the current data set or the version that was used prior to the mid-2000s, and numerous studies that have relied on these observations should be reexamined to determine the sensitivity of their results to this change in the data set. Furthermore, a number of recent studies have investigated physical mechanisms for the observed expansion of the Antarctic sea ice cover. The results of this analysis raise the possibility that much of this expansion may be a spurious artifact of an error in the processing of the satellite observations.

Eisenman, I, Untersteiner N, Wettlaufer JS.  2007.  On the reliability of simulated Arctic sea ice in global climate models. Geophysical Research Letters. 34   10.1029/2007gl029914   Website
Eisenman, I.  2010.  Geographic muting of changes in the Arctic sea ice cover. Geophysical Research Letters. 37   10.1029/2010gl043741   Website
Eisenman, I, Bitz CM, Tziperman E.  2009.  Rain driven by receding ice sheets as a cause of past climate change. Paleoceanography. 24   10.1029/2009pa001778   Website
Eisenman, I.  2005.  Non-normal effects on salt finger growth. Journal of Physical Oceanography. 35:616-627.   10.1175/jpo2716.1   Website
Eisenman, I, Schneider T, Battisti DS, Bitz CM.  2011.  Consistent Changes in the Sea Ice Seasonal Cycle in Response to Global Warming. Journal of Climate. 24:5325-5335.   10.1175/2011jcli4051.1   Website
Eisenman, I, Yu LS, Tziperman E.  2005.  Westerly wind bursts: ENSO's tail rather than the dog? Journal of Climate. 18:5224-5238.   10.1175/jcli3588.1   Website
Eisenman, I, Wettlaufer JS.  2009.  Nonlinear threshold behavior during the loss of Arctic sea ice. Proceedings of the National Academy of Sciences of the United States of America. 106:28-32.   10.1073/pnas.0806887106   Website