Abstract ATM-9612684 deMenocal, Peter Columbia University Title: Modeling Climate and Deep Water Sensitivity to Changes in Deglacial Meltwater Flux and Location Using a Fully-Coupled Ocean- Atmosphere GCM This award supports a project that will use a synchronously-coupled ocean-atmosphere general circulation model (O-A GCM ) to examine the dynamical origins of rapid, millennial-scale climate change events which punctuate the last glacial and deglacial periods. Focus will be on deep circulation and surface climate responses to prescribed changes in the supply and input location of deglacial meltwater to the ocean. The NASA GISS O-A GCM used in this proposal is unique because: 1) it does not require flux corrections to sustain realistic Atlantic deep water circulation so the entire climatic system is free to adjust to changed boundary conditions, 2) surface runoff is organized in 41 separate river drainages allowing for point-source freshwater injection to the ocean, 3) the ocean model is truly synchronously-coupled (every hour) to a full atmospheric model, and 4) the model supports oxygen-isotopic fractionation and tracer code to monitor resulting changes in Greenland ice composition. Three research foci will be addressed: 1) characterize the ocean-atmosphere model climate signatures associated with high and low deep-water production in the control model; 2) quantify deep circulation sensitivity to changes in the flux and location of deglacial meltwater input to the ocean; and 3) Younger Dryas simulation: effects of variable deglacial runoff volumes and input locations between 12,000-9,000 years ago.
