A reconstruction of sea surface temperature variability in the southeastern Gulf of Mexico from 1734 to 2008 C.E. using cross‐dated Sr/Ca records from the coral Siderastrea siderea

Abstract

This study uses skeletal variations in coral Sr/Ca from three Siderastrea siderea coral colonies within the Dry Tortugas National Park in the southeastern Gulf of Mexico (24°42′N, 82°48′W) to reconstruct monthly sea surface temperature (SST) variations from 1734 to 2008 Common Era (C.E.). Calibration and verification of the replicated coral Sr/Ca-SST reconstruction with local, regional, and historical temperature records reveals that this proxy-temperature relationship is stable back to 1879 C.E. The coral SST reconstruction contains robust interannual (~2.0°C) and multidecadal variability (~1.5°C) for the past 274 years, the latter of which does not covary with the Atlantic Multidecadal Oscillation. Winter SST extremes are more variable than summer SST extremes (±2.2°C versus ±1.6°C, 2σ) suggesting that Loop Current transport in the winter dominates variability on interannual and longer time scales. Summer SST maxima are increasing (+1.0°C for 274 years, σ MC = ±0.5°C, 2σ), whereas winter SST minima contain no significant trend. Colder decades (~1.5°C) during the Little Ice Age (LIA) do not coincide with decades of sunspot minima. The coral SST reconstruction contains similar variability to temperature reconstructions from the northern Gulf of Mexico (planktic foraminifer Mg/Ca) and the Caribbean Sea (coral Sr/Ca) suggesting areal reductions in the Western Hemisphere Warm Pool during the LIA. Mean summer coral SST extremes post-1985 C.E. (29.9°C) exceeds the long-term summer average (29.2°C for 1734-2008 C.E.), yet the warming trend after 1985 C.E. (0.04°C for 24 years, σ MC = ±0.5, 2σ) is not significant, whereas Caribbean coral Sr/Ca studies contain a warming trend for this interval.

Reef cores as records of Holocene water temperatures of the southern Great Barrier Reef: Geochemical analysis of traditional (Porites) and non-traditional (Acropora) reef building corals

“…However, the inconsistent occurrence of massive Porites colonies necessitates the use of additional genera for climate reconstructions. Developments in the use of alternate coral genera as paleoenvironmental indicators have seen recent advances [e.g., DeLong et al, 2014;Felis et al, 2014;, including the potential use of inter-branch skeleton in Acropora , a highly abundant coral genus in many Indo-Pacific reef cores Humblet et al, 2015;Shirai et al, 2008] with significant volumes recovered in IODP Expeditions 310, Tahiti Sea Level [Camoin et al, 2007], and 325, Great Barrier Reef Environmental Changes . recently reported that the inter-branch skeleton of corymbose Acropora colonies (i.e., colonies with branches that initiate from a central location and extend to a common level ) does not display the significant levels of secondary skeletal thickening typically associated with branches, which previously prevented the use of Acropora in high resolution geochemical climate 154 reconstructions Shirai et al, 2008].…”

Little Ice Age climate in the Western Tropical Atlantic inferred from coral geochemical proxies

“…The skeletons of long-lived, massive coral colonies have the potential to produce high-resolution records of past tropical ocean temperatures [Gagan et al, 2000;DeLong et al, 2014;Linsley et al, 2015]. The thin layer of living coral tissue continually precipitates an aragonite (CaCO 3 ) skeleton allowing the coral colony to grow upward and preserve its older skeleton below [Cohen and McConnaughey, 2003].…”

“…High latitude cooling has been constrained to 1-2 ˚C [Overpeck et al, 1997;Marcott et al, 2013] but previous Sr/Ca derived estimates of LIA cooling from this region range from 0 to 5 ˚C [Haase-Schramm et al, 2003;DeLong et al, 2014]. The cold end of these estimates implies greater climate sensitivity in the tropics than at high latitudes, conflicting with evidence from both simulations [Holland and Bitz, 2003;Landrum et al, 2013] and 20 th century observations [Pithan and Mauritsen, 2014].…”

“…The annually-banded skeletons of massive, longlived corals are a potentially valuable archive of ocean temperature conditions that can be used to extend the instrumental record across space and back in time. Sr/Ca [Smith et al, 1979;Beck et al, 1992] is currently the most widely used coral proxy thermometer [e.g., Carilli et al, 2014;DeLong et al, 2014;Wu et al, 2014;Thompson et al, 2015;Toth et al, 2015]. However, many studies…”

“…Further, Sr/Ca-based SSTs for the WTA LIA are inconsistent, and range from no cooling to as much as 4 ˚C cooler than today [Haase-Schramm et al, 2003;2009b;DeLong et al, 2014]. The colder end of these estimates is comparable to or larger than estimates for the Last Glacial Maximum (LGM) cooling [Waelbroeck et al, 2009].…”