Northern Hemisphere forcing of climatic cycles in Antarctica over the past 360,000 years

Abstract

The Milankovitch theory of climate change proposes that glacial-interglacial cycles are driven by changes in summer insolation at high northern latitudes. The timing of climate change in the Southern Hemisphere at glacial-interglacial transitions (which are known as terminations) relative to variations in summer insolation in the Northern Hemisphere is an important test of this hypothesis. So far, it has only been possible to apply this test to the most recent termination, because the dating uncertainty associated with older terminations is too large to allow phase relationships to be determined. Here we present a new chronology of Antarctic climate change over the past 360,000 years that is based on the ratio of oxygen to nitrogen molecules in air trapped in the Dome Fuji and Vostok ice cores. This ratio is a proxy for local summer insolation, and thus allows the chronology to be constructed by orbital tuning without the need to assume a lag between a climate record and an orbital parameter. The accuracy of the chronology allows us to examine the phase relationships between climate records from the ice cores and changes in insolation. Our results indicate that orbital-scale Antarctic climate change lags Northern Hemisphere insolation by a few millennia, and that the increases in Antarctic temperature and atmospheric carbon dioxide concentration during the last four terminations occurred within the rising phase of Northern Hemisphere summer insolation. These results support the Milankovitch theory that Northern Hemisphere summer insolation triggered the last four deglaciations.

Timing of massive ‘Fleuve Manche’ discharges over the last 350kyr: insights into the European ice-sheet oscillations and the European drainage network from MIS 10 to 2

“…Moreover, numerous studies show strong palaeoenvironmental and palaeoclimatic changes at time of the increasing Northern Hemisphere insolation during the mid-MIS 6 (e.g. Petit et al, 1999;Ayalon et al, 2002;Kawamura et al, 2007;Hodge et al, 2008;Wang et al, 2008), corroborating the concept of a reorganisation of the southern margin of the European ice sheet and Alpine glaciers within the ca. 160-150 ka interval.…”

“…280-260 ka and ca. 160-150 ka intervals (Kawamura et al, 2007) while glaciomarine conditions overran site ODP-980 and the Bay of Biscay despite the significant rise of the Northern Hemisphere summer insolation. Even if the discharges were not always as important as at ca.…”

On the impact of impurities on the densification of polar firn

“…Recently, it has been shown that the entrapped air in the ice is also related to local orbital insolation variations (Bender, 2002;Raynaud et al, 2007). The orbital signal in the ice would permit dating ice core records independently from other methods (Kawamura, 2009;Kawamura et al, 2007) if the complete chain of processes involved in the signal formation at the surface, in the firn column and at the firn-ice transition was understood. Presently, it is believed that local insolation affects the microstructure of the firn at the surface, which is unaltered during the densification and recrystallization process in the firn.…”

Climatology of stable isotopes in Antarctic snow and ice: Current status and prospects

“…Records of Loess [91] and marine [92] sediments also show a similar glacial-interglacial cycle, suggesting a synchronization of global climate change on orbital timescale, reflecting the periodic variations of the earth's orbital parameters. According to Milankovitch theory, the main driving factor for the glacial-interglacial cycle of climate is the amount of summer solar radiation received by the Earth at high northern latitude [93]. The signal of the summer solar radiation is conveyed through variations of greenhouse gas concentration and thermohaline circulation intensity.…”