Coral Record of Younger Dryas Chronozone Warmth on the Great Barrier Reef

Abstract

The Great Barrier Reef (GBR) is an internationally recognized and widely studied ecosystem, yet little is known about its sea surface temperature (SST) evolution since the Last Glacial Maximum (LGM) (~20 kyr BP). Here, we present the first paleo‐application of Isopora coral‐derived SST calibrations to a suite of 25 previously published fossil Isopora from the central GBR spanning ~25–11 kyr BP. The resultant multicoral Sr/Ca‐ and δ18O‐derived SST anomaly (SSTA) histories are placed within the context of published relative sea level, reef sequence, and coralgal reef assemblage evolution. Our new calculations indicate SSTs were cooler on average by ~5–5.5°C at Noggin Pass (~17°S) and ~7–8°C at Hydrographer's Passage (~20°S) (Sr/Ca‐derived) during the LGM, in line with previous estimates (Felis et al., 2014, https://doi.org/10.1038/ncomms5102). We focus on contextualizing the Younger Dryas Chronozone (YDC, ~12.9–11.7 kyr BP), whose Southern Hemisphere expression, in particular in Australia, is elusive and poorly constrained. Our record does not indicate cooling during the YDC with near‐modern temperatures reached during this interval on the GBR, supporting an asymmetric hemispheric presentation of this climate event. Building on a previous study (Felis et al., 2014, https://doi.org10.1038/ncomms5102), these fossil Isopora SSTA data from the GBR provide new insights into the deglacial reef response, with near‐modern warming during the YDC, since the LGM.

Last Deglacial Environmental Change in the Tropical South Pacific From Tahiti Corals

“…Our results support that the Northern Hemisphere last deglacial temperature variations, such as the Younger Dryas cooling, have likely not similarly affected all regions of the South Pacific (Kiefer & Kienast, 2005). For instance, opposed to findings from this study for Tahiti and a previous study for Vanuatu (Corrège et al., 2004), coral‐based‐SST reconstructions for the Great Barrier Reef (Brenner et al., 2020; Felis et al., 2014), reconstructions of glacier retreat in the New Zealand Southern Alps (Koffman et al., 2017), and stable isotope stalagmite records from Borneo (Partin et al., 2007) revealed no evidence for the Younger Dryas cooling. The cause of these regional differences in South Pacific last deglacial climate variability is unclear.…”

Role of the Deglacial Buildup of the Great Barrier Reef for the Global Carbon Cycle

“…However, a closer match of the GBR record of coral δ 13 C values with simulations is possible by some adjustments in the chosen parameter values, for example, by assuming that land carbon density was with 60 kgC/m 2 on the shelf platform twice as high as on the slope (best-guess scenarios shown in Figure 3b). This is in line with the substantially warmer conditions (Brenner et al, 2020;Felis et al, 2014a;Figure S5 in Supporting Information S1) and developing mangrove forests (Grindrod et al, 1999) after 13.0 ka in the GBR, and with estimates of combined tree, dead wood and soil carbon density of mangrove forests today (Donato et al, 2011;Sanderman et al, 2018). Furthermore, some fine-scale adjustments in the simulated coral δ 13 C are obtained, when the variability of atmospheric δ 13 CO 2 is also taken into account (scenario "111-best-prescribed" in Figure 3b).…”

Sea surface temperatures governed the development and longevity of the Great Barrier Reef

“…2). The TEX86 H -record coincides with the 3-4°C glacial to interglacial variability seen in the foraminiferal Mg/Ca ratios [31][32][33] and the coral Sr/Ca records 21,22 from the Coral Sea (Fig. S1).…”

“…Zoom-in map showing GBR was made using Google Earth. This includes ODP site 1195 10 , Ribbon Reef 5 12 , NOG (Noggin Pass), and HYD (Hydrographer's Passage) 21,22 .…”

“…During the LGM, there is some evidence that the reef system migrated to the edge of the existing reef platform, and it can be assumed that a similar process happened during earlier glacials 19 . Glacial summer SSTs above 26°C would have allowed coral larvae to establish new reefs during the glacials, which could then repopulate the shelf when sea levels rose again, allowing the system to survive multiple glacial cycles 16,19,21,22 . In summary, our data suggest that the conditions after MIS 11 continued to be ideal for the growth of the GBR.…”