AbstractIn this thesis, paleoclimate records are compared with isotope-enabled model simulations. We concentrate on the Last Interglacial (LIG), the most recent period when global temperatures were similar to the low-end 21st Century projections (1.5-2°C warmer).
A relevant outcome of the thesis focusses on explaining the LIG Greenland δ18O maximum. Chapters 3 to 6 examine how Greenland ice core δ18O responds to variations in Arctic sea ice extent, Greenland Ice Sheet (GIS) morphology and freshwater forcing from the retreating GIS. Chapter 3 demonstrates that Arctic sea ice changes need to be accounted for to ensure an optimised model-data solution. Chapter 4 highlights that, if more certain records at Camp Century and DYE3 ice core sites were available, this would be in agreement with LIG GIS morphologies with lower elevations in the south and a likely two-dome structure of the GIS. In addition, Chapter 6 shows freshwater forcing from the retreating GIS is an important player on the LIG Greenland δ18O change.
Another important contribution of the thesis concentrates on examining how Greenland ice core δ18O depends on the magnitude and sign of GIS elevation changes. Chapter 5 shows a non-linearity for δ18O changes over Greenland; δ18O changes are weaker for increases in GIS elevation than for decreases. This results in a non-linearity isotopic lapse rate. In particular, winter sea ice changes may signiﬁcantly inﬂuence isotopic-elevation gradients. This has important implications for paleoclimate studies, in which stationary lapse rates are assumed and normally based on present-day observations.
Future steps are to: obtain additional (DYE3 and Camp Century) data; consider sea ice and ice changes in a joint framework following a Gaussian Process emulation approach and take also account of isostatic change.
|Date of Award||29 Sep 2020|
|Supervisor||Dan J Lunt (Supervisor) & Paul J Valdes (Supervisor)|