Christian Rodehacke

Coupled simulations of Greenland Ice Sheet and climate change up to A.D. 2300

Recent observations indicate a high sensitivity of the Greenland Ice Sheet (GrIS) to climate change. We examine the coupling between the GrIS surface mass balance, elevation, and dynamical flow with one of the few coupled GrIS and atmosphere-ocean general circulation models. Bidirectional coupling from the early Holocene reveals a growing present-day GrIS in the absence of anthropogenic forcing. We identify atmospheric sources of biases in the simulated present-day GrIS and assess the GrIS sensitivity to future greenhouse gas forcing through three Representative Concentration Pathways and their extensions and to climate variability. The elevation-surface mass balance feedback contributes to future GrIS mass loss with 8–11% (by 2100), depending on the forcing scenario, and 24–31% (by 2300). Climate variability causes a 2.5 times spread in the magnitude of the simulated present-day GrIS mass trends in a three-member ensemble. Our results represent a first step toward more advanced higher resolution coupled modeling of GrIS and climate evolution.

On the origin of the deep CFC maximum in the Eastern Weddell Sea—Numerical model results

CFC tracer observations indicate that Prydz Bay in the Indian sector of the Southern Ocean is a region of deep and bottom water formation. Results of a circum- polar ocean circulation model which includes CFC, an age tracer, and numerical floats indicate Prydz Bay as being a convection site which contributes to the reservoir of freshly ventilated waters in the Weddell Sea. In contrast to the newly formed Weddell Sea Bottom Water, captured near bottom, water masses of Prydz Bay origin spread on hori- zons which pass the ridges confining the Weddell Sea, there- fore, contributing directly to the ventilation of the global abyss.