Showing papers by "Jérôme Chappellaz published in 1998"

Asynchrony of Antarctic and Greenland climate change during the last glacial period

Abstract: A central issue in climate dynamics is to understand how the Northern and Southern hemispheres are coupled during climate events. The strongest of the fast temperature changes observed in Greenland (so-called Dansgaard–Oeschger events) during the last glaciation have an analogue in the temperature record from Antarctica. A comparison of the global atmospheric concentration of methane as recorded in ice cores from Antarctica and Greenland permits a determination of the phase relationship (in leads or lags) of these temperature variations. Greenland warming events around 36 and 45 kyr before present lag their Antarctic counterpart by more than 1 kyr. On average, Antarctic climate change leads that of Greenland by 1–2.5 kyr over the period 47–23 kyr before present.

Atmospheric CO2 concentration and millennial-scale climate change during the last glacial period

Abstract: The analysis of air bubbles trapped in polar ice has permitted the reconstruction of past atmospheric concentrations of CO2 over various timescales, and revealed that large climate changes over tens of thousands of years are generally accompanied by changes in atmospheric CO2 concentrations1 But the extent to which such covariations occur for fast, millennial-scale climate shifts, such as the Dansgaard–Oeschger events recorded in Greenland ice cores during the last glacial period2, is unresolved; CO2 data from Greenland3 and Antarctic4 ice cores have been conflicting in this regard More recent work suggests that Antarctic ice should provide a more reliable CO2 record, as the higher dust5 content of Greenland ice can give rise to artefacts1,6,7 To compare the rapid climate changes recorded in the Greenland ice with the global trends in atmospheric CO2 concentrations as recorded in the Antarctic ice, an accurate common timescale is needed Here we provide such a timescale for the last glacial period using the records of global atmospheric methane concentrations from both Greenland and Antarctic ice We find that the atmospheric concentration of CO2 generally varied little with Dansgaard–Oeschger events (<10 parts per million by volume, ppmv) but varied significantly with Heinrich iceberg-discharge events (∼20 ppmv), especially those starting with a long-lasting Dansgaard–Oeschger event