Climate trends, variability and extremes recorded by water isotopes during the last two millennia

Stable water isotopes are widely used to reconstruct past temperature and precipitation variations in many regions of the Earth. While the general physical processes of how isotope variations are controlled by temperature and water amounts is well understood, quantifying past isotope changes as a proxy for temperature and precipitation is much more difficult. An explicit simulation of water isotopes in current Earth system models is one possibility to approach this problem.
In this study we present new results of a transient fully-coupled simulation of the climate of the last two millennia, using the isotope-enabled model MPI-ESM-wiso. We analyze long-term trends, variability and extremes of the simulated isotope changes in precipitation, compare model results to available data compilations (e.g. PAGES Iso2k) and quantify the relations with associated temperature and hydrological changes. Our analyses show that for many regions of the Earth, the surface warming starting with the beginning of the industrialization period is clearly imprinted in the oxygen-18 isotope signal of precipitation, e.g., over Greenland, North America, and the Atlantic Ocean. However, in some regions recent temperature, precipitation and isotope changes seem to be decoupled, e.g., over West Antarctica, Oceania, and the Indian Ocean. In our presentation, we will discuss this regional varying imprint of the Anthropocene on the water isotope signal in detail. Further analyses focus on changes in isotope variability in different regions over the last two millennia, as well as the possible detection of past climate extremes in different isotope records.