ARCTIC VULNERABILITY TO CLIMATE VARIABILITY OVER THE PAST 3.6 MYR: A NEW VIEW FROM SEDIMENTS DRILLED AT LAKE EL'GYGYTGYN, WESTERN BERINGIA

In 2009, ICDP drilling at Lake El’gygytgyn (67^o30’ N, 172 ^o 05’ E) recovered lacustrine sediments dating to 3.58 Ma that provide the first time-continuous Pliocene-Pleistocene Arctic paleoclimate record of alternating glacial-interglacial change. The warmest and 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^o C warmer than today with nearly ~3 times the annual precipitation. Atmospheric CO₂ levels are estimated to have been 360 to 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 with abrupt changes in boreal forest composition at 2.715-2.695, 2.56 ad 2.53 Ma punctuated by an abrupt change in precipitation at 2.94-2.91 Ma. Extreme warmth in the Mid Pliocene Arctic occurs at the same time ANDRILL results suggest the West Antarctic Ice Sheet was non-existent. The Lake El’gygytgyn record includes a strong M2 cooling event in a number of proxies at ~3.3 Ma, with conditions comparable to the early Holocene Thermal Maximum, but not glacial climates. Our reconstructions do not preclude the existence of a Greenland Ice sheet during M2 but are unfavorable for the initiation of ice over parts of North America until after 3.0 Ma.

A variety of proxies show pronounced glacial episodes started ~2.6 Ma ago, but the full range of typical glacial/interglacial change wasn’t established until ~1.8 Ma ago. Numerous “super interglacials” occur during the Quaternary record, with maximum summer temperatures and annual precipitation (esp. during MIS 9,11 and 31) at Lake El’gygytgyn exceeding that documented for MIS 5e. Climate simulations show extreme conditions cannot be explained by interglacial greenhouse gas concentrations and orbital parameters alone. Many of these super-interglacials correspond with intervals of West Antarctic Ice Sheet retreat (MacKay et al. 2010). The record from “Lake E”, 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 warmth in the rest of the Arctic.