Local Variations in the 13-Suess Effect: A Global and Regional Phenomenon
Abstract
The burning of fossil fuel has lowered the δ13C of the atmosphere, a change which is visible in the δ13C of dissolved inorganic carbon in the oceans. Although atmospheric measurements of the δ13C of CO2 have only been routine since 1980, the rate of change in atmospheric δ13C since the start of the industrial revolution can be monitored by measuring the δ13C of skeletal organisms such as sclerosponges and corals. For example, by fitting a polynomial equation to the δ13C data from sclerosponges and then determining the first derivative, a rate of change in δ13C can be calculated which increases from -0.001‰/yr in 1850 to -0.009‰/yr in 1960, and -0.026‰/yr at the present day. In comparison the decrease at the present day in the Pacific is significantly lower (-0.01‰/yr). Although shallow water corals from the Atlantic also show the same overall changes in the δ13C, there are locations such as in the Florida Keys, where the rates of change over the past 50 years have been much greater than the global rate. For example, the rate of change between 1960 and 1990 in two different corals examined growing in Florida Bay was -0.045 and -0.06‰/yr respectively, significantly greater than -0.026. Since 1990 however there have been no further decreases in the δ13C of these corals with the result that the change between 1960 and 2010 agrees with the global change. The high rates of change in δ13C this coral and in fact all the corals in Florida, are punctuated by periods during which the change is considerably less than the rate calculated from the sclerosponge data. We propose that these oscillations result from varying delivery of terrestrial organic material to the coastal zone, probably brought about by variations in water delivery and hence local/regional precipitation. During times of enhanced delivery the δ13C of the coastal dissolved inorganic carbon and hence the δ13C of the corals decreases at a faster rate than the global rate. During periods of low delivery the system tends to come back into equilibrium. As patterns of precipitation are often link through climate teleconnections, deviations in the δ13C of corals from the global trends are frequently correlated in geographic disparate areas. Such as the case here where similar deviations from the 13C- Suess effect can be observed in corals from localities throughout the Caribbean.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.B12A..05S
- Keywords:
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- 0400 BIOGEOSCIENCES;
- 0428 BIOGEOSCIENCES / Carbon cycling;
- 1030 GEOCHEMISTRY / Geochemical cycles;
- 4220 OCEANOGRAPHY: GENERAL / Coral reef systems