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Investigating Millennial-Scale Climate Change With a Sea-Ice/Ocean Model and an Ice Sheet Model

EPA Grant Number: U915353
Title: Investigating Millennial-Scale Climate Change With a Sea-Ice/Ocean Model and an Ice Sheet Model
Investigators: Franco, Heather
Institution: University of Maine
EPA Project Officer: Boddie, Georgette
Project Period: January 1, 1998 through January 1, 2000
Project Amount: $26,202
RFA: STAR Graduate Fellowships (1998)
Research Category: Fellowship - Geology , Ecological Indicators/Assessment/Restoration , Academic Fellowships

Description:

Objective:

The objective of this research project is to investigate millennial-scale climate change with a sea-ice/ocean model and an ice sheet model. Two possibly related millennial scale climate oscillations are known from the geologic record during the last glacial period. Previously developed models are coupled and studied separately to investigate certain aspects of this climate change.

Approach:

The two existing, auto-oscillatory low-order models, one of which simulates an ice sheet and the other the sea-ice/ocean system, are coupled to study their physical links. Low-order models incorporate only the most essential components of a system to aid in the understanding of primary processes. The prior investigation into the sensitivity of the ice sheet model used here was less comprehensive than that for the sea-ice/ocean system. The first step in this project was to analyze this model to determine if model runs with different parameter values generated the accepted time range between dated ice rafting events. Accumulation rates and average ice sheet size were varied over values common to the last glacial period. We assume that major ice rafting events are the result of surges simulated by the model; however, other mechanisms for discharge are possible. The first asynchronous coupling was achieved through an empirical relationship between temperature and accumulation rate. Temperature at sea level is obtained from the sea-ice/ocean model, and these values are extrapolated to the elevation of the ice sheet using a constant lapse rate. Accumulation rates are then approximated. The next coupling is in the opposite direction where the ice sheet model predicts rafted ice volume. The primary outcome is the removal of latent heat needed to melt the icebergs from the surface ocean temperature component of the sea-ice/ocean model. Other time-dependent variations in accumulation rate also were used to learn the possible effects that longer time scales of change have on an ice sheet.

Supplemental Keywords:

fellowship, millennial-scale climate oscillation, geologic record, glacial period, sea-ice/ocean system, ice rafting, ice sheet. , Ecosystem Protection/Environmental Exposure & Risk, Air, Scientific Discipline, RFA, Ecosystem/Assessment/Indicators, Geology, climate change, Ecology, Air Pollution Effects, Atmosphere, computing technology, Ecological Indicators, Atmospheric Sciences, Environmental Chemistry, Ecological Effects - Environmental Exposure & Risk, Ecosystem Protection, Monitoring/Modeling, Agricultural Engineering, Global Climate Change, atmospheric temperature, environmental monitoring, low-order model, millennial scale climate variability, Heinrich events, climate variability, Dansgaard-Oeschger events, model

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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