Holocene variability in the intensity of wind-gap upwelling in the tropical eastern Pacific

Abstract

Wind-driven upwelling in Pacific Panamá is a significant source of oceanographic variability in the tropical eastern Pacific. This upwelling system provides a critical teleconnection between the Atlantic and tropical Pacific that may impact climate variability on a global scale. Despite its importance to oceanographic circulation, ecology, and climate, little is known about the long-term stability of the Panamanian upwelling system or its interaction with climatic forcing on millennial time scales. Using a combination of radiocarbon and U-series dating of fossil corals collected in cores from five sites across Pacific Panamá, we reconstructed the local radiocarbon reservoir correction, ΔR, from~6750 cal B.P. to present. Because the ΔR of shallow-water environments is elevated by upwelling, our data set represents a millennial-scale record of spatial and temporal variability of the Panamanian upwelling system. The general oceanographic gradient from relatively strong upwelling in the Gulf of Panamá to weak-to-absent upwelling in the Gulf of Chiriquí was present throughout our record; however, the intensity of upwelling in the Gulf of Panamá varied significantly through time. Our reconstructions suggest that upwelling in the Gulf of Panamá is weak at present; however, the middle Holocene was characterized by periods of enhanced upwelling, with the most intense upwelling occurring just after of a regional shutdown in the development of reefs at~4100 cal B.P. Comparisons with regional climate proxies suggest that, whereas the Intertropical Convergence Zone is the primary control on modern upwelling in Pacific Panamá, the El Niño-Southern Oscillation drove the millennial-scale variability of upwelling during the Holocene.

Fluctuations in marine radiocarbon reservoir age in the western Pacific: Evidence of reduced E-W Pacific gradient over the past 6000 years

“…Our results of reduced R and ΔR values from Lanyu Island (Fig. 2 & 3) suggest enhanced air-sea interactions during the mid-Holocene, and support the hypothesis of reduced ENSO frequency and a persistently La Niña-like state, which are inferred from both modeling and proxy-based paleoclimate studies (Clement et al, 2000;Koutavas et al, 2002;Liu et al, 2000;McGregor et al, 2008;Toth et al, 2015). The physical mechanism is detailed as bellow.…”

Upwelling buffers climate change impacts on coral reefs of the eastern tropical Pacific

“…Furthermore, although reefs in both gulfs experienced a ~2,000‐yr hiatus in reef accretion in response to enhanced ENSO variability beginning ~4,000 yr ago, the shutdown of reef development was more protracted in the Gulf of Panamá (Toth et al ). This difference was likely due to more variable conditions and cold‐water influxes from seasonal upwelling there (Toth et al a, 2015a,b). Yet, as the oceans warm and as El Niño events become more frequent and more extreme (Kim et al , Cai et al ), upwelling environments like the Gulf of Panamá could provide temporary refuges in areas where extreme thermal maxima are buffered by cooling associated with upwelling (Riegl and Piller , Karnauskas and Cohen , Riegl et al ; but see Chollett et al ).…”

“…Upwelling is the most important source of intra‐annual variability in many parts of the ETP (Poveda et al , Toth et al , , Fiedler and Lavín ). In the Gulf of Panamá, seasonal upwelling is driven by the annual migration of the Intertropical Convergence Zone (ITCZ) between 10 and 3° N (Poveda et al ).…”

“…Such wind‐driven upwelling events can reduce sea‐surface temperature (SST) in the Gulf of Panamá by 10°C within a few days to weeks (Glynn and Stewart , Glynn ). The topographic differential along the Isthmus of Panamá, with the high Central American cordillera mountain range (the Cordillera Central) to the west and a topographic low in the Cordillera Central to the east, produces a pronounced gradient in upwelling strength along Panamá's Pacific coast: orographic effects in the west inhibit trade winds, markedly reducing upwelling in the Gulf of Chiriquí compared with the Gulf of Panamá (D'Croz and O'Dea , Toth et al ).…”

An Online Application for ΔR Calculation

“…ΔR values calculated from independently dated samples, such as U-Th dated corals, have not always included the calendar age uncertainty (e.g. Toth et al 2015). In addition, in more complex cases such as contemporaneous marine and terrestrial radiocarbon samples, classical intercept methods have usually been used (c.f.…”