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  • Copernicus Publications on behalf of the European Geosciences Union  (2)
  • Nature Research  (1)
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  • 1
    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in A stalagmite test of north atlantic SST and iberian hydroclimate linkages over the last two glacial cycles. Climate of the Past, 14(12), (2018); 1893-1913., doi:10.5194/cp-14-1893-2018.
    Description: Close coupling of Iberian hydroclimate and North Atlantic sea surface temperature (SST) during recent glacial periods has been identified through the analysis of marine sediment and pollen grains co-deposited on the Portuguese continental margin. While offering precisely correlatable records, these time series have lacked a directly dated, site-specific record of continental Iberian climate spanning multiple glacial cycles as a point of comparison. Here we present a high-resolution, multi-proxy (growth dynamics and δ13C, δ18O, and δ234U values) composite stalagmite record of hydroclimate from two caves in western Portugal across the majority of the last two glacial cycles (∼220 ka). At orbital and millennial scales, stalagmite-based proxies for hydroclimate proxies covaried with SST, with elevated δ13C, δ18O, and δ234U values and/or growth hiatuses indicating reduced effective moisture coincident with periods of lowered SST during major ice-rafted debris events, in agreement with changes in palynological reconstructions of continental climate. While in many cases the Portuguese stalagmite record can be scaled to SST, in some intervals the magnitudes of stalagmite isotopic shifts, and possibly hydroclimate, appear to have been somewhat decoupled from SST.
    Description: This work was supported by the Center for Global and Regional Environmental Research, Cornell College (to Rhawn F. Denniston), and the US National Science Foundation (grant BCS-1118155 to Jonathan A. Haws, BCS-1118183 to Michael M. Benedetti, and AGS-1804132 to Caroline C. Ummenhofer). Field sampling was performed under the auspices of IGESPAR (to Jonathan A. Haws) and Associação de Estudos Subterrâneos e Defesa do Ambiente. Brandon Zinsious and Stephen Rasin contributed to fieldwork at BG, and Zachary LaPointe assisted with radioisotopic analyses; Suzanne Ankerstjerne performed stable isotope measurements. This paper benefitted tremendously from discussions with Maria F. Sánchez Goñi, David Hodell, and Chronis Tzedakis. We thank five anonymous reviewers who substantially improved this paper's scope and clarity through detailed and thoughtful assessments. Stable and U-series isotope data are available at the NOAA National Centers for Environmental Information website.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
    Publication Date: 2022-05-25
    Description: © The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biogeosciences 10 (2013): 4591-4606, doi:10.5194/bg-10-4591-2013.
    Description: The shells of marine mollusks are widely used archives of past climate and ocean chemistry. Whilst the measurement of mollusk δ18O to develop records of past climate change is a commonly used approach, it has proven challenging to develop reliable independent paleothermometers that can be used to deconvolve the contributions of temperature and fluid composition on molluscan oxygen isotope compositions. Here we investigate the temperature dependence of 13C–18O bond abundance, denoted by the measured parameter Δ47, in shell carbonates of bivalve mollusks and assess its potential to be a useful paleothermometer. We report measurements on cultured specimens spanning a range in water temperatures of 5 to 25 °C, and field collected specimens spanning a range of −1 to 29 °C. In addition we investigate the potential influence of carbonate saturation state on bivalve stable isotope compositions by making measurements on both calcitic and aragonitic specimens that have been cultured in seawater that is either supersaturated or undersaturated with respect to aragonite. We find a robust relationship between Δ47 and growth temperature. We also find that the slope of a linear regression through all the Δ47 data for bivalves plotted against seawater temperature is significantly shallower than previously published inorganic and biogenic carbonate calibration studies produced in our laboratory and go on to discuss the possible sources of this difference. We find that changing seawater saturation state does not have significant effect on the Δ47 of bivalve shell carbonate in two taxa that we examined, and we do not observe significant differences between Δ47-temperature relationships between calcitic and aragonitic taxa.
    Description: This work was funded by National Science Foundation grants ARC-1215551 to R. A. Eagle and A. K. Tripati, EAR-1024929 to R. A. Eagle and J. M. Eiler, and EAR-0949191 to A. K. Tripati. A. K. Tripati is also supported by the Hellman Fellowship program. Culture of bivalves in Kiel, Germany, was funded by the German Science Foundation (DFG Ei272/21-1, to Anton Eisenhauer) and the European Science Foundation (ESF) Collaborative Research Project CASIOPEIA (04 ECLIM FP08). Determination of bivalve mineralogy by J. B. Ries was funded by National Science Foundation grant OCE-1031995.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 3
    Publication Date: 2023-02-25
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Whitney, N. M., Wanamaker, A. D., Ummenhofer, C. C., Johnson, B. J., Cresswell-Clay, N., & Kreutz, K. J. Rapid 20th century warming reverses 900-year cooling in the Gulf of Maine. Communications Earth & Environment, 3(1), (2022): 179, https://doi.org/10.1038/s43247-022-00504-8.
    Description: The Gulf of Maine, located in the western North Atlantic, has undergone recent, rapid ocean warming but the lack of long-term, instrumental records hampers the ability to put these significant hydrographic changes into context. Here we present multiple 300-year long geochemical records (oxygen, nitrogen, and previously published radiocarbon isotopes) measured in absolutely-dated Arctica islandica shells from the western Gulf of Maine. These records, in combination with climate model simulations, suggest that the Gulf of Maine underwent a long-term cooling over most of the last 1000 years, driven primarily by volcanic forcing and North Atlantic ocean dynamics. This cooling trend was reversed by warming beginning in the late 1800s, likely due to increased atmospheric greenhouse gas concentrations and changes in western North Atlantic circulation. The climate model simulations suggest that the warming over the last century was more rapid than almost any other 100-year period in the last 1000 years in the region.
    Description: Funding for this research was provided by the following sources: Bruce Bowen Fellowship (N.M.W.), Geological Society of America Graduate Student Research Grant (N.M.W.), James E. and Barbara V. Moltz Fellowship for Climate-Related Research at WHOI (C.C.U.), Maine Marine Research Fund (B.J.J.), National Oceanic and Atmospheric Administration Climate and Global Change Postdoctoral Fellowship (N.M.W.), National Science Foundation grant OCE 1003438 and MGG 2028197 (A.D.W.), National Science Foundation grant OCE 1003423 (K.J.K.), National Science Foundation grant OCE 0929900 (B.J.J.). We thank the CESM1(CAM5) Last Millennium Ensemble Community Project for providing the climate model simulations, which were performed using the supercomputing resources provided by NSF/CISL/Yellowstone.
    Keywords: Climate and Earth system modelling ; Marine chemistry ; Palaeoceanography ; Physical oceanography
    Repository Name: Woods Hole Open Access Server
    Type: Article
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