Seasonal radiocarbon and oxygen isotopes in a Galapagos coral: Calibration with climate indices

Druffel, Ellen R. M.; Griffin, Sheila; Glynn, D. S.; Dunbar, Robert B.; Mucciarone, David A.; Toggweiler, J. R.

doi:10.1002/2014gl060504

Cited by 15 publications

(35 citation statements)

References 30 publications

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“…For instance, Druffel et al . [] found an increase in average Δ 14 C values after the mid‐1940s change in the phase of the PDO, which changed from positive to negative phase. They interpreted this observation as the result of variations in the sources of water to the EUC.…”

Section: Discussionmentioning

confidence: 75%

“…Coral 14 C is particularly useful in the upwelling regions of the STCs as a result of the large gradient in Δ 14 C values between surface and subsurface waters [ Guilderson and Schrag , ; Grottoli et al ., ; Druffel et al ., ]. For instance in the Pacific, Druffel et al .…”

Section: Introductionmentioning

confidence: 99%

“…For instance in the Pacific, Druffel et al . [] observed a shift in cool season Δ 14 C values in a coral from the Galapagos Islands that occurred after the 1940's shift in the phase of the Pacific Decadal Oscillation (PDO). They argued that the shift in Δ 14 C values was the result of an increase in the amount of Subantarctic Mode Water to the Equatorial Undercurrent (EUC) relative to water from the northern subpolar Pacific.…”

Section: Introductionmentioning

confidence: 99%

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Ventilation time scales of the North Atlantic subtropical cell revealed by coral radiocarbon from the Cape Verde Islands

et al. 2015

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We present coral-and sclerosponge-based reconstructions of the 14 C content in North Atlantic dissolved inorganic carbon (DIC) during the last~100 years from the subtropical cells (STCs). These waters are sensitive to the dynamics of the shallow overturning meridional circulation that transports heat and water masses from the subtropics to the tropics. We use these records to investigate the circulation patterns of the off-equatorial upwelling regions of the STCs, which are not well understood. Coral and sclerosponge skeletons provide long time series of ocean DIC 14 C content, a tracer of oceanic circulation, effectively extending the observational record back in time. Sclerosponge data from the Bahamas were used to extend the existing subtropical 14 C time series to the 21st century. Coral 14 C data from the Cape Verde Islands (1890-2002) captured the 14 C signature of water brought to the surface in the off-equatorial regions of the STC present near the West African coast. We observe a unique postbomb trend at Cape Verde that is similar to the upwelling regions in the Pacific, and we interpret this trend as the result of the slow penetration of bomb 14 C into the interior ocean as part of the STC circulation. Using a multibox mixing model we constrain the time history of bomb 14 C in the eastern tropical Atlantic, and we estimate a 20 year time scale for ventilation of the thermocline in this area of the ocean. The similarity between the Atlantic and Pacific 14 C-based records of upwelling suggests that both are caused by bomb 14 C penetration rather than more complex explanations that invoke changes in thermocline depth (e.g., related to El Niño-Southern Oscillation variability) or changes in the strength of the subtropical cells. Our results offer constraints for models of tropical ocean circulation and anthropogenic CO 2 uptake that attempt to reproduce the characteristics of the shallow wind-driven circulation in the Atlantic.

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Section: Discussionmentioning

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ventilation time scales of the North Atlantic subtropical cell revealed by coral radiocarbon from the Cape Verde Islands

et al. 2015

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“…High-resolution 14 C measurements of coral skeletons can be used to reconstruct continuous and seasonal/ interannual variability in ocean conditions (Guilderson et al 2000;Druffel et al 2014;Andrews et al 2016). However, post-bomb 14 C data are scarcely available for the SCS (e.g., Mitsuguchi et al 2007;Shen et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Radiocarbon variability recorded in coral skeletons from the northwest of Luzon Island, Philippines

et al. 2017

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The North Equatorial Current (NEC) bifurcates at the eastern coast of the Philippines and moves northward as the Kuroshio, a North Pacific western boundary current. The NEC bifurcation point and Kuroshio variability are known to be affected by changes in climate such as the El Niño-Southern Oscillation and the pacific decadal oscillation. However, observational data are not sufficient to examine the mechanisms of decadal fluctuation. Here, we report seasonal radiocarbon data recorded from 1968 to 1995 in coral skeletons northwest of Luzon Island. The data suggest that the East Asian winter monsoon is a dominant factor in the seasonal fluctuations in water mass northwest of Luzon Island. Compared with other coral records reported for Guam, Ishigaki, Con Dao, and Hon Tre Island, the data suggest that the area of the Kuroshio loop current through the Luzon Strait decreased from the 1970s to 1980s as a result of the change in Kuroshio transport and the migration of the NEC bifurcation latitude after a regime shift in 1976.

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“…In the Tasman Sea the relative delivery of these waters and subsurface flow of Subantarctic Mode Water (SAMW) with even lower Δ 14 C derived from the Southern Ocean can vary the surface reservoir age by ~100 14 C years on timescales of less than 100 years [ Komugabe et al ., ] (Figure b). This advective influence on surface 14 C in the southwest Pacific contrasts with the eastern Equatorial and Southeast Pacific where upwelling changes dominate surface Δ 14 C in the Galapagos [ Druffel et al ., ] and off the coast of South America [ Ortlieb et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Southwest Pacific Ocean surface reservoir ages since the last glaciation: Circulation insights from multiple‐core studies

Sikes

Guilderson

2016

Paleoceanography

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Radiocarbon (14C) in dissolved inorganic carbon in the ocean can trace the age of ocean water relative to the atmosphere and provide insight into climate‐driven changes in ocean circulation since the last glaciation. Here we estimate surface radiocarbon ages from the last glaciation through the deglaciation into the Holocene in the southwestern Pacific by using tephras, both as stratigraphic tie points and for the availability of existing radiocarbon dates from terrestrial‐ based analyses of the organic carbon associated with them, as markers of past atmospheric Δ14C. The glacial surface reservoir age of subtropical waters was ~700 14C years older than the coeval atmosphere at ~25,000 cal yr B.P. This was significantly older (more 14C depleted) by ~ 300 14C years, than modern reservoir ages. At the same time, subantarctic surface water reservoir age was ~3200 14C years, almost 5 times the modern reservoir age, making the difference in age between subtropical and subantarctic surface water masses treble the modern difference. This pattern is attributed to the upwelling and exchange of very old deep waters from the glacial abyss in the Southern Ocean. In the early deglaciation, surface reservoir ages were ~600 to 700 14C years. Recent atmospheric Δ14C calibrations project that these surface reservoir ages were older than modern by 1.2‐fold to 2‐fold. This increased reservoir effect can be attributed to shallow circulation that differed from modern, delivering waters with lower 14C content to the region. Early Holocene surface reservoir ages of ~300 to 500 14C years, similar to recent, suggest modern circulation patterns were in place by that time.

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Seasonal radiocarbon and oxygen isotopes in a Galapagos coral: Calibration with climate indices

Cited by 15 publications

References 30 publications

Ventilation time scales of the North Atlantic subtropical cell revealed by coral radiocarbon from the Cape Verde Islands

Ventilation time scales of the North Atlantic subtropical cell revealed by coral radiocarbon from the Cape Verde Islands

Radiocarbon variability recorded in coral skeletons from the northwest of Luzon Island, Philippines

Southwest Pacific Ocean surface reservoir ages since the last glaciation: Circulation insights from multiple‐core studies

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