An Investigation of the Last Interglacial's Climate Characteristics: Insights from a Stable Water Isotope Equipped Climate Model

• Main Author: Gierz, Paul
• Other Authors: Lohmann, Gerrit, Kucera, Michal
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2016
• Subjects: Climate Modelling; Last Interglacial; Paleoclimate; 500; 500 Science; ddc:500; Ice Sheet; North Atlantic
• Online Access: https://media.suub.uni-bremen.de/handle/elib/1244; https://nbn-resolving.org/urn:nbn:de:gbv:46-00105969-15

The Last Interglacial (LIG), spanning from approximately 130,000 to 115,000 years ago, is the warm period immediately preceding the last ice age, and represents one of the most recent intervals in Eartha s history that was significantly warmer than the pre-industrial. As such, it is an excellent test bed for understanding the controlling dynamics of warm climate periods. By performing simulations of this period using a fully coupled, stable water isotope enhanced climate model (COSMOS-WISO), new insights into the strength of stable water isotopes as temperature proxies could be uncovered. The utility of the isotopic composition of rainfall, I 8OP, as a paleothermometer is examined. It was found that the changes in I 18OP do not always correspond to changes in temperature, particularly when only small magnitude temperature changes are considered. A second set of studies examined the match between simulated responses to LIG climate boundary conditions to measurements from various different paleoclimate archives. Of particular interest is the ability to reconstruct the North Atlantic temperature changes during the LIG, as these are closely tied to changes in the Atlantic Meridional Overturning Circulation (AMOC), which in turn redistributes large amounts of heat from the equatorial latitudes to the mid and high latitudes. Proxy evidence points to a cooling in this region during the early LIG, which may be indicative of a relatively weaker overturning circulation. However, the extent of this weakening is difficult to gauge based solely on temperature differences. When compared to model simulations, feasible temperature differences could be simulated with AMOC possibilities ranging from only a slightly weaker overturning circulation, to a stronger collapse possibly triggered by ice sheet melting. In order to eliminate one of these possibilities, additional comparisons with simulated isotopic signature in calcite were performed. When comparing to measurements from planktic foraminifera, a strong AMOC collapse ...