Panamá Coral Ba/Ca Reconstruction of River Discharge from 1719-2018 CE Reveals that Central Pacific El Niño Events and Large Volcanic Eruptions are Predictors of Drought: Implications for Management of the Panamá Canal
Abstract
In Panamá, the wet season occurs when the Intertropical Convergence Zone (ITCZ) shifts north from May to November generating on average 2.5m of rainfall that fills the reservoirs utilized to operate the Panamá Canal. Droughts result in ship draft restrictions and floods can damage canal infrastructure, therefore, knowledge about past variability and climate forcing factors of Panamanian hydrology is useful for canal management. The Gulf of Chiriquí (GoC) in western Panamá offers a unique setting to monitor changes in Eastern Pacific ITCZ activity through the reconstruction of river discharge (Q) using the geochemistry of corals. Here we present a near-monthly resolution, partially replicated time-series of coral skeletal Ba/Ca extending from 1719 to 2018 CE. We show that coral Ba/Ca is highly correlated to monthly Q (R=0.91) entering the GoC. During El Niño, the ITCZ's northward migration is curtailed and drought occurs in Panamá. The opposite happens during La Niña when the ITCZ brings high rainfall. Interannual variability in coral Ba/Ca is correlated to ENSO phases; SST spatial correlation maps have global minima within the Nino3.4 area (R<-0.6 for 1890-2017 May-April annual means). Often extreme wet seasons, associated with La Niña, are followed by protracted droughts. For example, an exceptional wet season during the 1973 La Niña was followed by a 19-year drought. Another anomalously wet year, 1807, was followed by a decade-long drought ending in 1818. These decadal and some shorter droughts were coincident with volcanic forcing. Multiple droughts recorded by GoC coral Ba/Ca occur 0-3 years after large volcanic eruptions when stratospheric aerosol optical depth (SAOD) increased: 1808 "mystery", loc. unknown; 1815 Tambora; 1831 Babuyan; 1835 Cosigüina; 1877 Krakatau; 1890 Colima; 1912 Novarupta; 1963 Agung; 1968 Fernandina; 1974 Fuego; 1982 El Chichón; 1991 Pinatubo. The association of these eruptions with drought in Panamá is direct evidence of a link between volcanic events in either hemisphere that increase SAOD and interannual and decadal changes in the latitudinal position and/or intensity of the eastern Pacific ITCZ. Thus, El Niño events and large low-latitude volcanic eruptions can be used as predictors of drought in Panamá. Likewise, large amplitude La Niña events are predictors of flooding.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.A15H1331L