Thompson
William G.
Thompson
William G.
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ArticleCoral record of younger dryas chronozone warmth on the Great Barrier Reef(American Geophysical Union, 2020-12-11) Brenner, Logan D. ; Linsley, Braddock K. ; Webster, Jody M. ; Potts, Donald C. ; Felis, Thomas ; Gagan, Michael K. ; Inoue, Mayuri ; McGregor, Helen V. ; Suzuki, Atsushi ; Tudhope, Alexander W. ; Esat, Tezer M. ; Thomas, Alexander L. ; Thompson, William G. ; Fallon, Stewart ; Humblet, Marc ; Tiwari, Manish ; Yokoyama, YusukeThe 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.
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ArticleDynamic millennial-scale climate changes in the northwestern Pacific over the past 40,000 years(American Geophysical Union, 2010-12-03) Chen, Min-Te ; Lin, Xiaopei ; Chang, Yuan-Pin ; Chen, Y.-C. ; Lo, L. ; Shen, Chuan-Chou ; Yokoyama, Yusuke ; Oppo, Delia W. ; Thompson, William G. ; Zhang, RongIce core records of polar temperatures and greenhouse gases document abrupt millennial-scale oscillations that suggest the reduction or shutdown of thermohaline Circulation (THC) in the North Atlantic Ocean may induce the abrupt cooling in the northern hemisphere. It remains unknown, however, whether the sea surface temperature (SST) is cooling or warming in the Kuroshio of the Northwestern Pacific during the cooling event. Here we present an AMS 14C-dated foraminiferal Mg/Ca SST record from the central Okinawa Trough and document that the SST variations exhibit two steps of warming since 21 ka — at 14.7 ka and 12.8 ka, and a cooling (∼1.5°C) during the interval of the Younger Dryas. By contrast, we observed no SST change or oceanic warming (∼1.5–2°C) during the episodes of Northern Hemisphere cooling between ∼21–40 ka. We therefore suggest that the “Antarctic-like” timing and amplitude of millennial-scale SST variations in the subtropical Northwestern Pacific between 20–40 ka may have been determined by rapid ocean adjustment processes in response to abrupt wind stress and meridional temperature gradient changes in the North Pacific.
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ArticleMarine isotope stage 3 sea level fluctuations : data synthesis and new outlook(American Geophysical Union, 2008-11-05) Siddall, M. ; Rohling, Eelco J. ; Thompson, William G. ; Waelbroeck, ClaireTo develop a better understanding of the abrupt Dansgaard-Oeschger mode of climate change, it is essential that we establish whether the ice sheets are actively involved, as trigger or amplifier, or whether they merely respond in a passive manner. This requires careful assessment of the fundamental issues of magnitude and phasing of global ice volume fluctuations within marine isotope stage 3 (MIS 3), which to date remain enigmatic. We review recent advances in observational studies pertaining to these key issues and discuss the implications for modeling studies. Our aim is to construct a robust stratigraphic framework for the MIS 3 period regarding sea level variability, using the most up-to-date arguments available by combining insights from both modeling and observational approaches.
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ArticleIntensification of the meridional temperature gradient in the Great Barrier Reef following the Last Glacial Maximum(Nature Publishing Group, 2014-06-17) Felis, Thomas ; McGregor, Helen V. ; Linsley, Braddock K. ; Tudhope, Alexander W. ; Gagan, Michael K. ; Suzuki, Atsushi ; Inoue, Mayuri ; Thomas, Alexander L. ; Esat, Tezer M. ; Thompson, William G. ; Tiwari, Manish ; Potts, Donald C. ; Mudelsee, Manfred ; Yokoyama, Yusuke ; Webster, Jody M.Tropical south-western Pacific temperatures are of vital importance to the Great Barrier Reef (GBR), but the role of sea surface temperatures (SSTs) in the growth of the GBR since the Last Glacial Maximum remains largely unknown. Here we present records of Sr/Ca and δ18O for Last Glacial Maximum and deglacial corals that show a considerably steeper meridional SST gradient than the present day in the central GBR. We find a 1–2 °C larger temperature decrease between 17° and 20°S about 20,000 to 13,000 years ago. The result is best explained by the northward expansion of cooler subtropical waters due to a weakening of the South Pacific gyre and East Australian Current. Our findings indicate that the GBR experienced substantial meridional temperature change during the last deglaciation, and serve to explain anomalous deglacial drying of northeastern Australia. Overall, the GBR developed through significant SST change and may be more resilient than previously thought.
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ArticleA box model test of the freshwater forcing hypothesis of abrupt climate change and the physics governing ocean stability(American Geophysical Union, 2010-12-07) Jackson, Charles S. ; Marchal, Olivier ; Liu, Yurun ; Lu, Shaoping ; Thompson, William G.Observations and an ocean box model are combined in order to test the adequacy of the freshwater forcing hypothesis to explain abrupt climate change given the uncertainties in the parameterization of vertical buoyancy transport in the ocean. The combination is carried out using Bayesian stochastic inversion, which allows us to infer changes in the mass balance of Northern Hemisphere (NH) ice sheets and in the meridional transports of mass and heat in the Atlantic Ocean that would be required to explain Dansgaard-Oeschger Interstadials (DOIs) from 30 to 39 kyr B.P. The mean sea level changes implied by changes in NH ice sheet mass balance agree in amplitude and timing with reconstructions from the geologic record, which gives some support to the freshwater forcing hypothesis. The inversion suggests that the duration of the DOIs should be directly related to the growth of land ice. Our results are unaffected by uncertainties in the representation of vertical buoyancy transport in the ocean. However, the solutions are sensitive to assumptions about physical processes at polar latitudes.
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ArticleMonsoon hydrography and productivity changes in the East China Sea during the past 100,000 years : Okinawa Trough evidence (MD012404)(American Geophysical Union, 2009-08-29) Chang, Yuan-Pin ; Chen, Min-Te ; Yokoyama, Yusuke ; Matsuzaki, Hiroyuki ; Thompson, William G. ; Kao, Shuh-Ji ; Kawahata, HodakaWe analyzed the high-resolution foraminifer isotope records, total organic carbon (TOC), and opal content from an Okinawa Trough core MD012404 in order to estimate the monsoon hydrography and productivity changes in the East China Sea (ECS) of the tropical western Pacific over the past 100,000 years. The variability shown in the records on orbital time scales indicates that high TOC intervals coincide with the increases of boreal May–September insolation driven by precession cycles (∼21 ka), implying a strong connection to the variations in monsoons. We also observed possibly nearly synchronous, millennial-scale changes of the ECS surface hydrography (mainly driven by salinity changes but also by temperature effects) and productivity coincident with monsoon events in the Hulu/Dongge stalagmite isotope records. We found that increased freshening and high productivity correlate with high monsoon intensity in interstadials. This study suggests that the millennial-scale changes in monsoon hydrography and productivity in the ECS are remarkable and persistent features over the past 100,000 years.