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Free keywords:
water isotopes; general-circulation model; ice core records; interannual changes; Greenland; Antarctica
Abstract:
[1] A simulation with the Hamburg atmospheric general circulation model ECHAM-4, forced with sea surface temperatures of the period 1950-1994 and with stable water isotopes (H2O)-O- 18 and HDO explicitly included in the water cycle, was performed to examine interannual to decadal variations of the isotopic composition of precipitation in Greenland and Antarctica. The analyses focus on the Summit region, central Greenland, and the Law Dome region, East Antarctica, respectively. Simulation results reveal that about one third of the simulated variability in (H2O)-O-18 can be explained by simultaneous changes of the surface temperature at the precipitation sites. Other climate variables influencing the isotope signal are identified by multiple linear regression, and the results show that the (H2O)-O-18 record in central Greenland integrates the climatic history of a broader region. For the Law Dome region in Antarctica the (H2O)-O-18 record appears to be mainly related to climate changes at the precipitation site only. For the deuterium excess a clear influence of climate condition at two distinct regions of the Indian Ocean on the simulated deuterium excess record of the Law Dome region is found. On the contrary, a reconstruction of the year-to-year variability of the deuterium excess signal in central Greenland, by Atlantic Ocean surface parameters only, fails. Additional correlation analyses between the ECHAM-4 isotope simulation and indices of the North Atlantic Oscillation (NAO) and the El Nino-Southern Oscillation phenomenon (ENSO) enable the detection of influenced regions in Greenland and Antarctica: While NAO and ENSO are imprinted in the simulated (H2O)-O-18 record of precipitation, they cannot be detected in the simulated deuterium excess record.
