High Atlantic native Shen 2

Core/Site name:

Southern Preserve

Country/Region:

Bermuda

Elevation:

-9

Archive:

corals

Species:

Diploria strigosa

Proxy measurement:

Pb/Ca

Sampling resolution:

annual

Climate sensitivity:

anthropogenic influences

Dating resolution:

yearly (growth bands)

Dating information:

radiometric 14C

Startyear:

1933 AD

Endyear:

1983 AD

All uncertainties:

Assumed Kd value of 2.3

Description:

Twentieth century environmental lead chronologies for the western North Atlantic, Pacific, and Indian Oceans have been reconstructed from annually-banded scleractinian corals. Measurements of lattice-bound Pb in sequential coral bands reveal temporal changes in surface water Pb concentrations and Pb isotopic distributions. Perturbations are observable in all specimens studied, attesting to global augmentation of environmental Pb by industrialization.In the western North Atlantic, Pb perturbations have occurred in direct response to the American industrial revolution and the subsequent introduction and phasing-out of alkyl Pb additives in gasoline. Surface ocean conditions near Bermuda may be reliably reconstructed from the coral data via a lead distribution coefficient of 2.3 for the species,Diploria strigosa. Based on210Pb measurements, a similar distribution coefficient may be characteristic of corals in general. Surface Pb concentrations in the pre-industrial Sargasso Sea were about 15–20 pM. Concentrations rose to near 90 pM by 1923 as a result of metals manufacture and fossil fuel combustion. Beginning in the late 1940's, increased utilization of leaded gasoline eventually led to a peak concentration of 240 pM in 1971, representing an approximate 15-fold increase over background. Surface ocean concentrations are presently declining rapidly (128 pM in 1984) as a result of curtailed alkyl Pb usage. Lead isotopic shifts parallel the concentration record indicating that characteristic industrial and alkyl Pb source signatures have not changed appreciably in time. Industrial releases recorded in the Florida Keys reflect a weaker source and evidence of recirculated Pb (5–6 years old) from the North Atlantic subtropical gyre. An inferred background concentration of 38 pM suggests influence of shelf and/or resuspended inputs of Pb to these coastal waters.In remote areas of the South Pacific and Indian Oceans, industrial signals are fainter and the corals studied much younger than their Atlantic counterparts. Contemporary Pb concentrations implied by coral measurements (assumingKD = 2.3) are 40–50 pM for surface waters near Tutuila and Galapagos in the South Pacific, and 25–29 pM near Mauritius in the Indian Ocean. A single coral band from Fiji (1920 ± 5yr) implies a pre-industrial surface water concentration of 16–19 pM Pb for the South Pacific. In view of reported surface water measurements and the North Atlantic coral data, the Pacific coral extrapolations may be slightly high. This could be a result of small variations inKD among different coral genera, or incorporation of diagenetic Pb by corals sampled in coastal environments.

Data entered by name:

Katherine Esswein

Data entered by email:

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Main reference(s):

Shen, G.T. and E.A. Boyle. 1987. Lead in corals: reconstruction of historical industrial fluxes to the surface ocean. Earth and Planetary Science Letters 82: 289-304.

Link to reference 1:

http://www.sciencedirect.com/science/article/pii/0012821X87902032

Data storage link 1:

ftp://ftp.ncdc.noaa.gov/pub/data/paleo/coral/atlantic/preserve1987.txt

Comments:

Other data from this study can be found in High Indian native ShenHigh Pacific native Shen 3High Pacific native Shen 2High Pacific native Shen 1High Atlantic native Shen 3High Pacific Atlantic Shen 1

Current dating method:

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Annual snow acc rate:

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Category: Ocean2k