Combining paleo records, tide gauges, and process estimates to constrain 20th-century sea level rise in the South Atlantic Ocean
Abstract
Conventional observations of 20th-century sea level changes in the South Atlantic Ocean are only available from a small number of tide gauges. As a result, the 20th-century sea-level trend in this basin is more uncertain than in any other ocean basin, and this uncertainty propagates into reconstructions of global mean sea level. High-resolution paleo records and results from data archaeology are a valuable tool to fill in this knowledge gap. We combine new sea-level observations, estimates of vertical land motion, and information on spatial sampling biases to obtain a likely range of 20th-century sea-level rise in the South Atlantic. Next to existing tide-gauge data, we use rescued tide-gauge observations from Dakar and a new high-resolution sea level reconstruction based on salt marsh sediments from the Falklands. We find a 20th-century rate of sea level rise in the South Atlantic Ocean between 1.3 and 2.8 mm/year, with a central estimate of 2.0 mm/yr.
This rate higher than the global mean rate from most recent reconstructions, which is on the order of 1.4 mm/year. The next question is whether any physical process could explain this deviation from the global mean sea level trend. Steric expansion, as well as gravitation, rotation, and deformation effects related to ice mass loss and land water storage have led to an above-average sea level trend in the South Atlantic. Both effects together explain about half of the observed difference. Despite the still-remaining uncertainty in this basin, this method shows that the effects of vertical land motion and spatial sampling biases on reconstructions of regional sea level are large, and neglecting them could cause serious biases. These new records and information on spatial sampling biases, can help improve our understanding of 20th-century changes in global-mean sea level and its spatial variations.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP23A..08F
- Keywords:
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- 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions;
- GEODESY AND GRAVITY;
- 1621 Cryospheric change;
- GLOBAL CHANGE;
- 1641 Sea level change;
- GLOBAL CHANGE