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  • Foraminifera  (3)
  • AMOC  (1)
  • American Geophysical Union  (4)
  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 20 (2005): PA4005, doi:10.1029/2004PA001061.
    Description: Detailed deglacial and Holocene records of planktonic δ18O and Mg/Ca–based sea surface temperature (SST) from the Okinawa Trough suggest that at ∼18 to 17 thousand years before present (kyr B.P.), late spring/early summer SSTs were approximately 3°C cooler than today, while surface waters were up to 1 practical salinity unit saltier. These conditions are consistent with a weaker influence of the summer East Asian Monsoon (EAM) than today. The timing of suborbital SST oscillations suggests a close link with abrupt changes in the EAM and North Atlantic climate. A tropical influence, however, may have resulted in subtle decoupling between the North Atlantic and the Okinawa Trough/EAM during the deglaciation. Okinawa Trough surface water trends in the Holocene are consistent with model simulations of an inland shift of intense EAM precipitation during the middle Holocene. Millennial-scale alternations between relatively warm, salty conditions and relatively cold, fresh conditions suggest varying influence of the Kuroshio during the Holocene.
    Description: Funding for this research was provided by NSFC (grants 40106006 and 40206007), SKLLQG (grant LLQG0204), and the NSF (OCE-020776 to DWO). Y.S.'s visit to WHOI was supported via a NSF START Fellowship.
    Keywords: Okinawa Trough ; Deglaciation ; Holocene ; Kuroshio Current ; East Asian monsoon ; Mg/Ca ; Oxygen isotopes ; Foraminifera
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2003. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 18 (2003): 1086, doi:10.1029/2003PA000888.
    Description: Benthic foraminiferal Cd/Ca from an intermediate depth, western South Atlantic core documents the history of southward penetration of North Atlantic Intermediate Water (NAIW). Cd seawater estimates (CdW) for the last glacial are consistent with the production of NAIW and its export into the South Atlantic. At ∼14.5 ka concurrently with the onset of the Bølling-Allerød to Younger Dryas cooling, the NAIW contribution to the South Atlantic began to decrease, marking the transition from a glacial circulation pattern to a Younger Dryas circulation. High CdW in both the deep North Atlantic and the intermediate South Atlantic imply reduced export of deep and intermediate water during the Younger Dryas and a significant decrease in northward oceanic heat transport. A modern circulation was achieved at ∼9 ka, concurrently with the establishment of Holocene warmth in the North Atlantic region, further supporting a close linkage between deepwater variability and North Atlantic climate.
    Description: This work was supported by an MIT John Lyons Fellowship, a WHOI Ocean and Climate Change Institute Fellowship, and NSF grant OCE96-33499.
    Keywords: Cd/Ca ; δ13C ; Younger Dryas ; Intermediate water ; Foraminifera
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 3
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Spooner, P. T., Thornalley, D. J. R., Oppo, D. W., Fox, A. D., Radionovskaya, S., Rose, N. L., Mallett, R., Cooper, E., & Roberts, J. M. Exceptional 20th century ocean circulation in the Northeast Atlantic. Geophysical Research Letters, 47(10), (2020): e2020GL087577, doi:10.1029/2020GL087577.
    Description: The North Atlantic subpolar gyre (SPG) connects tropical and high‐latitude waters, playing a leading role in deep‐water formation, propagation of Atlantic water into the Arctic, and as habitat for many ecosystems. Instrumental records spanning recent decades document significant decadal variability in SPG circulation, with associated hydrographic and ecological changes. Emerging longer‐term records provide circumstantial evidence that the North Atlantic also experienced centennial trends during the 20th century. Here, we use marine sediment records to show that there has been a long‐term change in SPG circulation during the industrial era, largely during the 20th century. Moreover, we show that the shift and late 20th century SPG configuration were unprecedented in the last 10,000 years. Recent SPG dynamics resulted in an expansion of subtropical ecosystems into new habitats and likely also altered the transport of heat to high latitudes.
    Description: We thank Janet Hope and UCL laboratory staff, colleagues who sailed on EN539, Kathryn Pietro‐Rose, Sean O'Keefe and Henry Abrams, Sara Chipperton, Tanya Monica, Laura Thrower and Kitty Green for sediment processing, Miles Irving for artwork assistance, James Rolfe for nitrogen isotope measurement, Maryline Vautravers and Michael Kucera for guidance, Arne Biastoch and Christian Mohn for discussion of VIKING20, and Chris Brierley, Meric Srokosz, and Jon Robson for comments. Funding was provided by National Science Foundation (NSF) grant OCE‐1304291 to D.W.O. and D.J.R.T., the Leverhulme Trust, National Environment Research Council (NERC) grant NE/S009736/1, and the ATLAS project to D.J.R.T. This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement 678760 (ATLAS). This paper reflects only the authors views and the European Union cannot be held responsible for any use that may be made of the information contained herein.
    Keywords: Foraminifera ; Subpolar gyre ; North Atlantic ; Ocean circulation ; Industrial era
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
    Publication Date: 2022-08-19
    Description: Author Posting. © American Geophysical Union, 2022. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography and Paleoclimatology 37, (2022): e2021PA004379, https://doi.org/10.1029/2021pa004379.
    Description: Atlantic Meridional Overturning Circulation (AMOC) plays a central role in the global redistribution of heat and precipitation during both abrupt and longer-term climate shifts. Over the next century, AMOC is projected to weaken due to greenhouse gas warming, though projecting its future behavior is dependent on a better understanding of how AMOC changes are forced. Seeking to resolve an apparent contradiction of AMOC trends from paleorecords of the more recent past, we reconstruct seawater cadmium, a nutrient-like tracer, in the Florida Straits over the last ∼8,000 years, with emphasis on the last millennium. The gradual reduction in seawater Cd over the last 8,000 years could be due to a reduction in AMOC, consistent with cooling Northern Hemisphere temperatures and a southward shift of the Intertropical Convergence Zone. However, it is difficult to reconcile this finding with evidence for an increase in geostrophic flow through the Florida Straits over the same time period. We combine data from intermediate water depth sediment cores to extend this record into the Common Era at sufficient resolution to address the broad scale changes of this time period. There is a small decline in the Cd concentration in the Late Little Ice Age relative to the Medieval Climate Anomaly, but this change was much smaller than the changes observed over the Holocene and on the deglaciation. This suggests that any trend in the strength of AMOC over the last millennium must have been very subtle.
    Description: This work was funded by the NSF Graduate Research Fellowship DGE-1148903 (SV) and NSF grant OCE-1459563 and OCE-1851900 (JLS).
    Keywords: AMOC ; seawater cadmium ; Florida Straits ; Holocene ; Little Ice Age
    Repository Name: Woods Hole Open Access Server
    Type: Article
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