Came Rosemarie E.

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Rosemarie E.

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  • Preprint
    Rapid early Holocene deglaciation of the Laurentide ice sheet
    ( 2008-07-24) Carlson, Anders E. ; LeGrande, Allegra N. ; Oppo, Delia W. ; Came, Rosemarie E. ; Schmidt, Gavin A. ; Anslow, Faron S. ; Licciardi, Joseph M. ; Obbink, Elizabeth A.
    The early Holocene deglaciation of the Laurentide Ice Sheet (LIS) is the most recent and best constrained disappearance of a large Northern Hemisphere ice sheet. Its demise is a natural experiment for assessing rates of ice sheet decay and attendant contributions to sea level rise. Here we demonstrate with terrestrial and marine records that the final LIS demise occurred in two stages of rapid melting from ~9.0- 8.5 and 7.6-6.8 kyr BP with the LIS contributing ~1.3 and 0.7 cm yr-1 to sea level rise, respectively. Simulations using a fully coupled atmosphere-ocean general circulation model suggest that increased ablation from enhanced early Holocene boreal summer insolation may have been the predominant cause of the LIS contributions to sea level rise. Although the boreal summer surface radiative forcing of early Holocene LIS retreat is twice that of projections for 2100 C.E. greenhouse gas radiative forcing, the associated summer surface air temperature increase is the same. The geologic evidence for rapid LIS retreat under a comparable forcing provides a prehistoric precedent for a possible large negative mass balance response of the Greenland Ice Sheet by the end of the coming century.
  • Article
    Deglacial variability in the surface return flow of the Atlantic meridional overturning circulation
    (American Geophysical Union, 2008-03-29) Came, Rosemarie E. ; Oppo, Delia W. ; Curry, William B. ; Lynch-Stieglitz, Jean
    Benthic foraminiferal Cd/Ca from a Florida Current sediment core documents the history of the northward penetration of southern source waters within the surface return flow of the Atlantic meridional overturning circulation (AMOC). Cd seawater estimates (CdW) indicate that intermediate-depth southern source waters crossed the equator and contributed to the Florida Current during the Bølling-Allerød warm period of the last deglaciation, consistent with evidence of only a modest AMOC reduction compared to today. The CdW estimates also provide the first paleoceanographic evidence of a reduction in the influence of intermediate-depth southern source waters within the Florida Current during the Younger Dryas, a deglacial cold event characterized by a weak North Atlantic AMOC. Our results reveal a close correspondence between the northward penetration of intermediate-depth southern source waters and the influence of North Atlantic Deep Water, suggesting a possible link between intermediate-depth southern source waters and the strength of the Atlantic AMOC.
  • Article
    Atlantic Ocean circulation during the Younger Dryas : insights from a new Cd/Ca record from the western subtropical South Atlantic
    (American Geophysical Union, 2003-11-25) Came, Rosemarie E. ; Oppo, Delia W. ; Curry, William B.
    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.
  • Article
    Regional climate variability in the western subtropical North Atlantic during the past two millennia
    (American Geophysical Union, 2011-04-21) Saenger, Casey P. ; Came, Rosemarie E. ; Oppo, Delia W. ; Keigwin, Lloyd D. ; Cohen, Anne L.
    Western subtropical North Atlantic oceanic and atmospheric circulations connect tropical and subpolar climates. Variations in these circulations can generate regional climate anomalies that are not reflected in Northern Hemisphere averages. Assessing the significance of anthropogenic climate change at regional scales requires proxy records that allow recent trends to be interpreted in the context of long-term regional variability. We present reconstructions of Gulf Stream sea surface temperature (SST) and hydrographic variability during the past two millennia based on the magnesium/calcium ratio and oxygen isotopic composition of planktic foraminifera preserved in two western subtropical North Atlantic sediment cores. Reconstructed SST suggests low-frequency variability of ∼1°C during an interval that includes the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). A warm interval near 1250 A.D. is distinct from regional and hemispheric temperature, possibly reflecting regional variations in ocean-atmosphere heat flux associated with changes in atmospheric circulation (e.g., the North Atlantic Oscillation) or the Atlantic Meridional Overturning Circulation. Seawater δ 18O, which is marked by a fresher MCA and a more saline LIA, covaries with meridional migrations of the Atlantic Intertropical Convergence Zone. The northward advection of tropical salinity anomalies by mean surface currents provides a plausible mechanism linking Carolina Slope and tropical Atlantic hydrology.
  • Article
    Consistently dated Atlantic sediment cores over the last 40 thousand years
    (Nature Research, 2019-09-02) Waelbroeck, Claire ; Lougheed, Bryan C. ; Vazquez Riveiros, Natalia ; Missiaen, Lise ; Pedro, Joel ; Dokken, Trond ; Hajdas, Irka ; Wacker, Lukas ; Abbott, Peter ; Dumoulin, Jean-Pascal ; Thil, Francois ; Eynaud, Frederique ; Rossignol, Linda ; Fersi, Wiem ; Albuquerque, Ana Luiza ; Arz, Helge W. ; Austin, William E. N. ; Came, Rosemarie E. ; Carlson, Anders E. ; Collins, James A. ; Dennielou, Bernard ; Desprat, Stéphanie ; Dickson, Alex ; Elliot, Mary ; Farmer, Christa ; Giraudeau, Jacques ; Gottschalk, Julia ; Henderiks, Jorijntje ; Hughen, Konrad A. ; Jung, Simon ; Knutz, Paul ; Lebreiro, Susana ; Lund, David C. ; Lynch-Stieglitz, Jean ; Malaizé, Bruno ; Marchitto, Thomas M. ; Martínez-Méndez, Gema ; Mollenhauer, Gesine ; Naughton, Filipa ; Nave, Silvia ; Nürnberg, Dirk ; Oppo, Delia W. ; Peck, Vicky L. ; Peeters, Frank J. C. ; Penaud, Aurélie ; Portilho-Ramos, Rodrigo da Costa ; Repschläger, Janne ; Roberts, Jenny ; Ruhlemann, Carsten ; Salgueiro, Emilia ; Sanchez Goni, Maria Fernanda ; Schönfeld, Joachim ; Scussolini, Paolo ; Skinner, Luke C. ; Skonieczny, Charlotte ; Thornalley, David J. R. ; Toucanne, Samuel ; Van Rooij, David ; Vidal, Laurence ; Voelker, Antje H. L. ; Wary, Mélanie ; Weldeab, Syee ; Ziegler, Martin
    Rapid changes in ocean circulation and climate have been observed in marine-sediment and ice cores over the last glacial period and deglaciation, highlighting the non-linear character of the climate system and underlining the possibility of rapid climate shifts in response to anthropogenic greenhouse gas forcing. To date, these rapid changes in climate and ocean circulation are still not fully explained. One obstacle hindering progress in our understanding of the interactions between past ocean circulation and climate changes is the difficulty of accurately dating marine cores. Here, we present a set of 92 marine sediment cores from the Atlantic Ocean for which we have established age-depth models that are consistent with the Greenland GICC05 ice core chronology, and computed the associated dating uncertainties, using a new deposition modeling technique. This is the first set of consistently dated marine sediment cores enabling paleoclimate scientists to evaluate leads/lags between circulation and climate changes over vast regions of the Atlantic Ocean. Moreover, this data set is of direct use in paleoclimate modeling studies.
  • Thesis
    Abrupt climate change in the Atlantic Ocean during the last 20,000 years : insights from multi-element analysis of benthic and planktic foraminifera and a coupled OA-GCM
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2005-09) Came, Rosemarie E.
    Minor and trace element records from planktic and benthic foraminifera from Atlantic sediment cores, as well as outputfrom a coupled OA·GCM, were used to investigate the magnitude and distribution of the oceanic response to abrupt Climate events.of the past 20,000 years. The study addressed three major questions: 1) What is the magnitude of high-latitude sea surface temperature and salinity variability during abrupt climate events? 2) Does intermediate depth ventilation change in conjunction with high-latitude climate variability? 3) Are the paleoclimate data consistent with the response of a coupled OAGCM to a freshwater perturbation? To address these questions, analytical methods were implemented for the simultaneous measurement of Mg/Ca, Zn/Ca, Cd/Ca, Mn/Ca and All Ca in foraminiferal samples using inductively-coupled plasma mass spectrometry. Paired records of planktic foraminiferal ()IRO and Mg/Ca from the subpolar North Atlantic reveal trends of increasing temperatures (-3°C) and salinities over the course of the Holocene. The records provide the first evidence of open':'ocean cooling (nearly 2°C) and freshening during the 8.2 kyr event, and suggest similar conditions at 9.3 ka. Benthic foraminiferal Cd/Ca results from an intermediate depth, western South Atlantic core (l,268 ni) are consistent with reduced export into the South Atlantic of North Atlantic Intermediate Water during the Younger Dryas. Paired records. of benthic foraminiferal Mg/Ca and bIRO from two intermediate depth low latitude western Atlantic sites - one from the Florida Current (751 m) and one from the Little Bahama Bank (l,057 m) - provicie insights into the spatial distribution of intermediate depth temperature and sii!.inity variability during" the Younger Dryas. The intermediate depth paleoceanographic temperature and salinity data are consistent with the results of a GFDL R30 freshwater forced model simulation, suggesting that freshwater forcing is a possible driver or amplifier for B011ing-Aller0d to Younger Dryas climate variability. Benthic foraminiferal Cd/Ca results from an intermediate depth Florida Current core (751 m) are consistent with a decrease in the northward penetration of southern source waters within the return flow of the Atlantic meridional overturning circulation (MOC) and an increase in the influence of intermediate depth northern source waters during the Younger Dryas.