Open AccessCoral radiocarbon records of Indian Ocean water mass mixing and wind‐induced upwelling along the coast of Sumatra, Indonesia
Author(s) -
Grumet N. S.,
Abram N. J.,
Beck J. W.,
Dunbar R. B.,
Gagan M. K.,
Guilderson T. P.,
Hantoro W. S.,
Suwargadi B. W.
Publication year - 2004
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2003jc002087
Subject(s) - upwelling , oceanography , coral , geology , radiocarbon dating , porites , sea surface temperature , water mass , seawater , aragonite , climatology , environmental science , geochemistry , calcite , paleontology
Radiocarbon ( 14 C) in the skeletal aragonite of annually banded corals track radiocarbon concentrations in dissolved inorganic carbon (DIC) in surface seawater. As a result of nuclear weapons testing in the 1950s, oceanic uptake of excess 14 C in the atmosphere has increased the contrast between surface and deep ocean 14 C concentrations. We present accelerator mass spectrometric (AMS) measurements of 14 C/ 12 C ratios (Δ 14 C) in Porites corals from the Mentawai Islands, Sumatra (0°S, 98°E) and Watamu, Kenya (3°S, 39°E) to document the temporal and spatial evolution of the 14 C zonal gradient in the tropical Indian Ocean. The rise in Δ 14 C in the Sumatra coral, in response to the maximum in nuclear weapons testing, is delayed by 2–3 years relative to the rise in coral Δ 14 C from the coast of Kenya. Kenya coral Δ 14 C values rise quickly because surface waters are in prolonged contact with the atmosphere. In contrast, wind‐induced upwelling and rapid mixing along the coast of Sumatra entrains 14 C‐depleted water from the subsurface, which dilutes the effect of the uptake of bomb‐produced 14 C by the surface ocean. Bimonthly AMS Δ 14 C measurements on the Mentawai coral reveal mainly interannual variability with minor seasonal variability. Singular spectrum analysis of the Sumatra coral Δ 14 C record reveals a significant 3‐year periodicity. These results lend support to the concept that interannual variability in Indian Ocean upwelling and sea surface temperatures is related to ENSO‐like teleconnections over the Indo‐Pacific basin.