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Monday, May 26, 2014

Millennial Scale Change From Lake El’gygytgyn, NE Russia: Did We Step Or Leap Out Of The Warm Pliocene Into The Pleistocene?

43rd International Arctic Workshop, Amherst, Mass., March 11-13, 2014

Julie Brigham-Grette1Martin Melles2Pavel Minyuk3, and the El'gygytgyn Science Team4
1University of Massachusetts, Amherst
2University of Cologne
4USA, Germany, Russia
The Pliocene-Pleistocene climate evolution of the Arctic must have modulated the glacial history of Greenland and the onset of Northern Hemisphere glaciation. What is known from the terrestrial stratigraphy of Arctic climate change comes from sites that are spatially and temporally fragmented. In 2009, International Continental Deep Drilling at Lake El’gygytgyn (67o 30' N, 172o 05' E) recovered lacustrine sediments dating back to 3.58 Ma that provide the first time-continuous Pliocene-Pleistocene Arctic paleoclimate record of alternating glacial-interglacial change. The warmest/wettest Pliocene interval of the lake record occurs from ~3.58-3.34 Ma and is dominated by exceptional tree pollen implying July temperatures nearly 7-8 oC warmer than today, with nearly ~3 times the annual precipitation. Atmospheric CO2 levels are estimated to have been 360-400 ppm implying exceptionally high climate sensitivity and polar amplification. In fact, pollen spectra and modern analog analysis show an unbroken persistence of summers much warmer and wetter than the last interglacial, MIS 5e until nearly 2.2 Ma. Extreme warmth in the Mid Pliocene Arctic occurs at the same time ANDRILL results suggest the West Antarctic Ice Sheet was non-existent.
Using physical, chemical, and biological proxies we find pronounced glacial episodes commenced ~2.6 Ma ago, but the full range of typical Pleistocene glacial/interglacial change was not established until ~1.8 Ma ago. Greenland must have also responded to numerous “super interglacials” during the Quaternary record, with maximum summer temperatures and annual precipitation, especially during MIS 9, 11 and 31, at Lake El’gygytgyn exceeding that documented for MIS 5e. The correspondence of many of these super-interglacials with retreat of the West Antarctic Ice Sheet (Naish et al. 2009) could coincide with intervals when the Greenland Ice was reduced in size. The climate record from Lake El’gygytgyn, especially the history of past interglacials, provides a fresh means of testing the evolving magnitude of polar amplification over time, and the sensitivity of the Greenland Ice Sheet to extreme warmth in the rest of the Arctic.
Brigham-Grette, J., Melles, M., Minyuk, P., Andreev, A., Tarasov, P., DeConto, R., Koenig, S., Nowaczyk, N., Wennrich, V., Rosén, P., Haltia-Hovi, E., Cook, T., Gebhardt, T., Meyer-Jacob, C., Snyder, J., Herzschuh, U.  Pliocene warmth, extreme polar amplification, and stepped Pleistocene cooling recorded in NE Russia. Submitted to Science, 21 November 2012; in revision March 2013.
Melles, M., Brigham-Grette, J., Minyuk, P., and others. 2012. 2.8 Million Years of Arctic Climate Change from Lake El’gygytgyn, NE Russia. Science, 337, 315-320.
Naish, T. et al., 2009. Obliquity-paced Pliocene West Antarctic ice sheet oscillations. Nature, 458, 322-328.
See also Climate of the Past, special issue on Lake El’gygytgyn, 20+ manuscripts.

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