An Inverse Approach to Estimate Past Ice Sheet Conditions from the South Pole Ice Core
Abstract
Polar ice-core records provide high-resolution information about past climate and ice sheet dynamics. Quantitative interpretation of these records can be achieved by solving an inverse problem that requires multiple sources of information from the ice to solve for past conditions. In this study, we use data from SPICEcore, a new ice core from the South Pole, to constrain boundary conditions at the ice-sheet surface through the last 50,000 years. Combining information from ice-core measurements of water isotopes, annual-layer thickness, and tie points to an independent timescale, we obtain self-consistent solutions for past temperature, accumulation rate, and vertical thinning of annual layers in the ice sheet. All of these parameters are interrelated through physical processes in the ice sheet, such as firn densification. From the water-isotope data, we consider the diffusion of water vapor in the permeable firn layer that damps high-frequency variations in the water-isotope profile. Through spectral analysis, the amount of diffusion can be quantified as the "diffusion length." The diffusion length provides a valuable constraint on this ice-core inverse problem because it depends on all of the boundary conditions and processes of interest (i.e., surface temperature, snow accumulation, layer thinning). We compare our inferences against independent information from the water-isotope data interpreted in the traditional way as a linear function of temperature. The results of this inverse approach provide robust estimates of temperature and accumulation rate through the last glacial-interglacial transition at the South Pole, improving our understanding of polar climate change on long timescales.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C13B..02K
- Keywords:
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- 0724 Ice cores;
- CRYOSPHERE;
- 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE;
- 1616 Climate variability;
- GLOBAL CHANGE;
- 4994 Instruments and techniques;
- PALEOCEANOGRAPHY