Eisenhauer Anton

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Eisenhauer
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Anton
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  • Article
    Salinity change in the subtropical Atlantic : secular increase and teleconnections to the North Atlantic Oscillation
    (American Geophysical Union, 2005-01-21) Rosenheim, Brad E. ; Swart, Peter K. ; Thorrold, Simon R. ; Eisenhauer, Anton ; Willenz, Philippe
    Recent studies comparing shipboard data between the 1950's and the 1990's have shown significant, heterogeneous adjustments of the temperature-salinity structure of the N. Atlantic Ocean. Here, we present proxy records of temperature and salinity from aragonite sclerosponge skeletons, extending existing records of the Salinity Maximum Waters (SMW) of the N. Atlantic back to 1890. These proxy records show secular temperature increases of 1.6–2.0°C, higher than published global averages, and salinity increases of 0.35–0.5 psu, smaller than short-term secular trends recently measured. Salinity reconstructions vary more significantly on the decadal scale, showing changes that are related to low-frequency variations of the North Atlantic Oscillation (NAO). On both secular and decadal time scales, the records indicate significant thermohaline changes in the SMW, either via forcing at the surface or increasing depths of density surfaces in the Bahamas.
  • Article
    Interlaboratory study for coral Sr/Ca and other element/Ca ratio measurements
    (John Wiley & Sons, 2013-09-23) Hathorne, Ed C. ; Gagnon, Alexander C. ; Felis, Thomas ; Adkins, Jess F. ; Asami, Ryuji ; Boer, Wim ; Caillon, Nicolas ; Case, David H. ; Cobb, Kim M. ; Douville, Eric ; deMenocal, Peter B. ; Eisenhauer, Anton ; Garbe-Schonberg, Dieter ; Geibert, Walter ; Goldstein, Steven L. ; Hughen, Konrad A. ; Inoue, Mayuri ; Kawahata, Hodaka ; Kolling, Martin ; Cornec, Florence L. ; Linsley, Braddock K. ; McGregor, Helen V. ; Montagna, Paolo ; Nurhati, Intan S. ; Quinn, Terrence M. ; Raddatz, Jacek ; Rebaubier, Helene ; Robinson, Laura F. ; Sadekov, Aleksey ; Sherrell, Robert M. ; Sinclair, Dan ; Tudhope, Alexander W. ; Wei, Gangjian ; Wong, Henri ; Wu, Henry C. ; You, Chen-Feng
    The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twenty-one laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7°C. However, most of the data fall within a narrower range and the Porites coral reference material JCp-1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5°C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is <0.5°C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1.
  • Article
    Groundwater discharge impacts marine isotope budgets of Li, Mg, Ca, Sr, and Ba
    (Nature Research, 2021-01-08) Mayfield, Kimberley K. ; Eisenhauer, Anton ; Santiago Ramos, Danielle ; Higgins, John A. ; Horner, Tristan J. ; Auro, Maureen E. ; Magna, Tomas ; Moosdorf, Nils ; Charette, Matthew A. ; Gonneea, Meagan E. ; Brady, Carolyn E. ; Komar, Nemanja ; Peucker-Ehrenbrink, Bernhard ; Paytan, Adina
    Groundwater-derived solute fluxes to the ocean have long been assumed static and subordinate to riverine fluxes, if not neglected entirely, in marine isotope budgets. Here we present concentration and isotope data for Li, Mg, Ca, Sr, and Ba in coastal groundwaters to constrain the importance of groundwater discharge in mediating the magnitude and isotopic composition of terrestrially derived solute fluxes to the ocean. Data were extrapolated globally using three independent volumetric estimates of groundwater discharge to coastal waters, from which we estimate that groundwater-derived solute fluxes represent, at a minimum, 5% of riverine fluxes for Li, Mg, Ca, Sr, and Ba. The isotopic compositions of the groundwater-derived Mg, Ca, and Sr fluxes are distinct from global riverine averages, while Li and Ba fluxes are isotopically indistinguishable from rivers. These differences reflect a strong dependence on coastal lithology that should be considered a priority for parameterization in Earth-system models.