Paleoproxies as Indicators of Water Mass Changes in the Caribbean
Abstract
Paleotemperature proxies derived from coral and sclerosponge skeletons collected from the Caribbean Sea and surrounding areas (Bahamas, Jamaica, Pedro Bank, Exuma Sound, Puerto Rico, and Guadeloupe) suggest temperature increases in excess of 1oC over the past century. Such increases are greater than those commonly accepted for global warming of surface oceans which is between 0.2 and 0.5oC. The question arises as to why water temperature in the sub-tropics, which were not as responsive to glacial-interglacial temperature changes, should show a greater response during the present anthropogenically induced warming. Here, we present reconstructed salinity data (using Sr/Ca and δ18O) measured in a number of sclerosponges collected from between 67 and 136 m water depth in the Bahamas. This study uses a modified temperature equation with respect to Sr/Ca for sclerosponges, which incorporates individuals which grew in colder water conditions. While this equation reduces somewhat the higher temperature change estimates calculated previously, these records still corroborate the high rates of temperature increase in the 20th century, even in at depths up to 150m, and illustrate a shoaling of high-salinity waters isopycnally transported into the Caribbean in the shallow subsurface (50-300 m). Decadal scale variability in these proxy records reflect variations in the origin of open ocean water masses, whereas long term trends are interpreted as shifts in the depths of the important subtropical and tropical halocline depths. This suggests changes in subsurface transport from subtropical cells rather than extreme warming of any singular water mass and is indicative of the heterogeneous nature of anthropogenic climate variability in the climate system's largest heat reservoir.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMPP22C..01S
- Keywords:
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- 4513 OCEANOGRAPHY: PHYSICAL / Decadal ocean variability;
- 4825 OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL / Geochemistry;
- 4870 OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL / Stable isotopes;
- 4924 PALEOCEANOGRAPHY / Geochemical tracers