Examining the utility of coral Ba/Ca as a proxy for river discharge and hydroclimate variability at Coiba Island, Gulf of Chirquí, Panamá

Brenner, Logan D.; Linsley, Braddock K.; Dunbar, Robert B.

Examining the utility of coral Ba/Ca as a proxy for river discharge and hydroclimate variability at Coiba Island, Gulf of Chirquí, Panamá

2017

Brenner, Logan D. | Linsley, Braddock K. | Dunbar, Robert B.

Panamá's extreme hydroclimate seasonality is driven by Intertropical Convergence Zone rainfall and resulting runoff. River discharge (Q) carries terrestrially-derived barium to coastal waters that can be recorded in coral. We present a Ba/Ca record (1996–1917) generated from a Porites coral colony in the Gulf of Chiriquí near Coiba Island (Panamá) to understand regional hydroclimate. Here coral Ba/Ca is correlated to instrumental Q (R=0.67, p<0.001), producing a seasonally-resolved Reduced Major Axis regression of Ba/Ca (μmol/mol)=Q (m3/s)×0.006±0.001 (μmol/mol)(m3/s)−1+4.579±0.151. Our results support work in the neighboring Gulf of Panamá that determined seawater Ba/Ca, controlled by Q, is correlated to coral Ba/Ca (LaVigne et al., 2016). Additionally, the Coiba coral Ba/Ca records at least 5 El Niño events and identified 22 of the 37 wet seasons with below average precipitation. These data corroborate the Q proxy and provide insight into the use of coral Ba/Ca as an El Niño and drought indicator.

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