Talk by Myriam Guillevic – Niels Bohr Institute - University of Copenhagen

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Niels Bohr Institute > Calendar > 2012 > Talk by Myriam Guillevic

Talk by Myriam Guillevic

Talk by Myriam Guillevic, PhD student at Centre for Ice and Climate

Abstract
Ice cores from Greenland have revealed the occurrence of 25 rapid climatic events (Dansgaard-Oeschger events, hereafter DO events) during the last glacial period. These DO events have a very strong temperature signal in Greenland (more than 15°C temperature increase in less than a century) with an imprint of almost global extent.
Open questions exist on the regional fingerprints of DO events in Greenland. The exact reorganization of the northern hemisphere water cycle and the sequence of events between low and high latitudes remain uncertain. In this study, we combine new measurements of water stable isotopes (dD, d18O, d17O) and air isotopes (d15N of N2) every 50 years on a sequence of three DO events (8-10) on the NEEM ice core (North Greenland Eemian Ice Drilling, North West Greenland). The isotopic composition of water, through the second order parameters deuterium excess and 17O-excess, allow to document changes in sea surface temperature and humidity at the evaporative regions at low latitudes. The comparison of d18O with d-excess and 17O-excess therefore allows to quantify the time lags between changes in Greenland temperature and changes in low latitudes evaporative conditions. The magnitude of temperature changes is quantified based on gas isotopes. The isotope and temperature patterns observed during DO 8-10 at NEEM are compared with results obtained from the NorthGRIP ice core to discuss the regional signature of DO events in Greenland. Finally, the gas and water isotope signals are compared with the methane records to characterize the sequence of events between low latitude methane production and polar climate.