WAS THE ARCTIC EOCENE 'RAINFOREST' MONSOONAL? ESTIMATES OF SEASONAL PRECIPITATION FROM EARLY EOCENE MACROFLORAS FROM ELLESMERE ISLAND, NUNAVUT

The Eocene hydrological cycle was a significant component in maintaining high latitude warm climates. The early Eocene featured 3 hyperthermals: the PETM/ETM1; ETM2; and EECO. Warm climates extended into the Arctic with substantive paleobotanical evidence for high Arctic precipitation (MAP > 150cm/yr) – an Arctic rainforest, contradicting climate models that show low Arctic precipitation. Arctic early Eocene wood stable isotope chemistry, however, showed a summer peak in precipitation, with modern analogs best sought on the summer-wet east coasts (e.g., China, Japan, South Korea) not the winter-wet west coasts of present-day northern temperate continents (e.g., Pacific northwest of North America). Highly seasonal ‘monsoon-type’ summer-wet precipitation regimes (i.e., summer precip./winter precip. > 3.0) seem to characterize early to mid-Eocene hyperthermal conditions in several regions of the earth, including the Arctic and Antarctic, based on both climate model sensitivity experiments and the paleoclimate proxy evidence. Presented here is a new analysis using leaf physiognomy of 3 leaf macrofloras from the Margaret Formation (Split Lake, Stenkul Fiord and Strathcona Fiord) from Ellesmere Island, placed stratigraphically as early Eocene, and likely between ETM1 and ETM2. High summer precipitation is estimated in the Arctic during the early Eocene, including ETM1, partialy corroborating the results from Eocene wood chemistry. Monsoonal conditions, however, are not indicated by our analysis with winter precipitation estimated as being high also. High year-round precipitation in the Eocene Arctic during hyperthermals would have contributed to regional warmth.