Dynamic simulation of stable water isotopes during the last interglacial

Wednesday, 17 December 2014
Paul Gierz1, Gerrit Lohmann2, William Brocas3 and Thomas Felis3, (1)Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Bremerhaven, Bremerhaven, Germany, (2)Alfred Wegener Institute for P, Bremerhaven, Germany, (3)University of Bremen, Bremen, Germany
Using the novel isotope module of the global fully coupled climate model COSMOS, we simulate the climate of the last interglacial for three time slices at 120, 125, and 130 kiloyears before present. The inclusion of stable water isotopes allows us to not only have a comprehensive picture of the climate state during a warm interglacial, but also allows for a direct comparison with climate proxy records. We compare our simulation with isotope data gathered from fossilized corals, which have an excellent temporal resolution and well constrained dating. A model data comparison allows us to see that there was an enhanced seasonality of both temperature and rainfall during the Eemian. While the data tends to produce a stronger winter cooling than the model, we suggest that this may be due to an incomplete climatology, as the measurements taken from the coral only encompasses a few decades. If the data happens to fall during an usually cool decade, the mismatch could be rectified. Alternatively, the data may include the cooling signal associated with centennial scale cold stadials during the Eemian. We test this by performing a freshwater perturbation experiment during the peak interglacial, which causes a pronounced cooling at the core site while the ocean circulation is depressed.