@article {382, title = {Florida Straits density structure and transport over the last 8,000 years}, journal = {Paleoceanography}, volume = {24}, year = {2009}, note = {id: 837; YY}, pages = {3209}, issn = {0883-8305}, doi = {10.1029/2008PA001717}, author = {Lynch-Stieglitz, J. and Curry, W. B. and Lund, D. C.} } @article {260, title = {Deglacial variability in the surface return flow of the Atlantic meridional overturning circulation}, journal = {Paleoceanography}, volume = {23}, year = {2008}, note = {id: 838; 281YL Times Cited:4 Cited References Count:41; YY}, abstract = {[1] 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 (Cd-W) indicate that intermediate-depth southern source waters crossed the equator and contributed to the Florida Current during the Bolling-Allerod warm period of the last deglaciation, consistent with evidence of only a modest AMOC reduction compared to today. The Cd-W 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.}, issn = {0883-8305}, doi = {10.1029/2007pa001450}, author = {Came, R. E. and Oppo, D. W. and Curry, W. B. and Lynch-Stieglitz, J.} } @article {366, title = {Episodic reductions in bottom-water currents since the last ice age}, journal = {Nature Geoscience}, volume = {1}, year = {2008}, note = {id: 1896; ISI Document Delivery No.: 331AG Times Cited: 9 Cited Reference Count: 34 Cited References: ALLEY RB, 1997, GEOLOGY, V25, P483 BARBER DC, 1999, NATURE, V400, P344 BARD E, 1994, EARTH PLANET SC LETT, V126, P275 BIANCHI GG, 1999, NATURE, V397, P515 BIANCHI GG, 1999, SEDIMENTOLOGY, V46, P1001 BOND G, 1992, NATURE, V360, P245 BOYLE EA, 1987, NATURE, V330, P35 BROECKER WS, 1989, GEOCHIM COSMOCHIM AC, V53, P2465 BROECKER WS, 1989, NATURE, V341, P318 CAME RE, 2007, GEOLOGY, V35, P315, DOI 10.1130/G23455A.1 CURRY WB, 2005, PALEOCEANOGRAPHY, V20, ARTN PA1017 DUPLESSY JC, 1980, NATURE, V286, P479 DUPLESSY JC, 1988, PALEOCEANOGRAPHY, V3, P343 ELLISON CRW, 2006, SCIENCE, V312, P1929, DOI 10.1126/science.1127213 FIRESTONE RB, 2007, P NATL ACAD SCI USA, V104, P16016, DOI 10.1073/pnas.0706977104 GHERARDI JM, 2005, EARTH PLANET SC LETT, V240, P710, DOI 10.1016/j.epsl.2005.09.061 GROOTES PM, 1993, NATURE, V366, P552 HALL IR, 2004, QUATERNARY SCI REV, V23, P1529, DOI 10.1016/j.quascirev.2004.04.004 KENNETT JP, 2007, EOS T AGU JOINT AS S, V88, UNSP PP41A05 KROOPNICK P, 1980, EARTH PLAN, V49, P469 LEGRAND P, 1995, PALEOCEANOGRAPHY, V10, P1011 MANABE S, 1995, NATURE, V378, P165 MCCARTNEY MS, 1996, OCEANUS, V39, P19 MCCAVE IN, 1995, NATURE, V374, P149 MCCAVE IN, 1995, PALEOCEANOGRAPHY, V10, P593 MCCAVE IN, 2006, GEOCHEM GEOPHY GEOSY, V7, P37 MCMANUS JF, 2004, NATURE, V428, P824 OPPO DW, 1993, SCIENCE, V259, P1148 ROHLING EJ, 2005, NATURE, V434, P975, DOI 10.1038/nature03421 RUDDIMAN WF, 1981, PALAEOGEOGR PALAEOCL, V35, P145 SARNTHEIN M, 1994, PALEOCEANOGRAPHY, V9, P209 TARASOV L, 2005, NATURE, V435, P662, DOI 10.1038/nature03617 WORTHINGTON LV, 1976, N ATLANTIC CIRCULATI YU EF, 1996, NATURE, V379, P689 Praetorius, Summer K. McManus, Jerry F. Oppo, Delia W. Curry, William B. Nature publishing group New york; YY}, pages = {449-452}, abstract = {Past changes in the freshwater balance of the surface North Atlantic Ocean are thought to have influenced the rate of deep-water formation, and consequently climate(1,2). Although water-mass proxies are generally consistent with an impact of freshwater input on meridional overturning circulation(3), there has been little dynamic evidence to support this linkage. Here we present a 25,000 year record of variations in sediment grain size from south of Iceland, which indicates vigorous bottom-water currents during both the last glacial maximum and the Holocene period. Together with reconstructions of North Atlantic water-mass distribution, vigorous bottom currents suggest a shorter residence time of northern-source waters during the last glacial maximum, relative to the Holocene period. The most significant reductions in flow strength occur during periods that have been associated with freshening of the surface North Atlantic. The short-term deglacial oscillations in bottom current strength are closely coupled to changes in Greenland air temperature, with a minimum during the Younger Dryas cold reversal and a maximum at the time of rapid warming at the onset of the Holocene. Our results support a strong connection between ocean circulation and rapid climate change.}, issn = {1752-0894}, doi = {10.1038/ngeo227}, author = {Praetorius, S. K. and McManus, J. F. and Oppo, D. W. and Curry, W. B.} } @article {318, title = {Subtropical Atlantic salinity variability and Atlantic meridional circulation during the last deglaciation}, journal = {Geology}, volume = {36}, year = {2008}, note = {id: 862; ISI Document Delivery No.: 381WN Times Cited: 5 Cited Reference Count: 32 Cited References: *CLIMAP PROJ MEMB, 1981, GEOL SOC AM MAP CHAR ANAND P, 2003, PALEOCEANOGRAPHY, V18, ARTN 1050 BENWAY HM, 2006, PALEOCEANOGRAPHY, V21, ARTN PA3008 BEVINGTON P, 2002, DATA REDUCTION ERROR BOYLE EA, 1987, NATURE, V330, P35 BROECKER WS, 1990, PALEOCEANOGRAPHY, V5, P469 CARLSON AE, 2007, P NATL ACAD SCI USA, V104, P6556, DOI 10.1073/pnas.0611313104 CLARK PU, 2004, SCIENCE, V304, P1141 GRIMM EC, 2006, QUATERNARY SCI REV, V25, P2197, DOI 10.1016/j.quascirev.2006.04.008 GROOTES PM, 1993, NATURE, V366, P552 KASPI Y, 2004, PALEOCEANOGRAPHY, V19, ARTN PA3004 KNORR G, 2003, NATURE, V424, P532, DOI 10.1038/nature01855 LEA DW, 2003, SCIENCE, V301, P1361 LEDUC G, 2007, NATURE, V445, P908, DOI 10.1038/nature05578 LEGRANDE AN, 2006, GEOPHYS RES LETT, V33, ARTN L12604 LEGRANDE AN, 2008, PALEOCEANOGRAPHY, V23, DOI 10.1029/2008PA001610 MCMANUS JF, 2004, NATURE, V428, P834, DOI 10.1038/nature02494 OPPO DW, 2007, GEOPHYS RES LETT, V34, ARTN L13701 PEETERS FJC, 2004, NATURE, V430, P661, DOI 10.1038/nature02785 PETERSON LC, 2000, SCIENCE, V290, P1947 ROBINSON LF, 2005, SCIENCE, V310, P1469, DOI 10.1126/science.1114832 RUHLEMANN C, 1999, NATURE, V402, P511 SCHMIDT GA, 2007, J GEOPHYS RES-ATMOS, V112, ARTN D10103 SCHMIDT MW, 2004, NATURE, V428, P160, DOI 10.1038/nature02346 SCHMIDT MW, 2006, NATURE, V443, P561, DOI 10.1038/nature05121 SCHMITZ WJ, 1995, REV GEOPHYS, V33, P151 SKINNER LC, 2006, QUATERNARY SCI REV, V25, P3312, DOI 10.1016/j.quascirev.2006.07.005 STOUFFER RJ, 2006, J CLIMATE, V19, P1365 THOMAS AL, 2006, EARTH PLANET SC LETT, V241, P493, DOI 10.1016/j.epsl.2005.11.031 WANG XF, 2004, NATURE, V432, P740, DOI 10.1038/nature03067 WEAVER AJ, 2003, SCIENCE, V299, P1709 WELDEAB S, 2006, EARTH PLANET SC LETT, V241, P699, DOI 10.1016/j.epsl.2005.11.012 Carlson, Anders E. Oppo, Delia W. Came, Rosemarie E. LeGrande, Allegra N. Keigwin, Lloyd D. Curry, William B. Geological soc amer, inc Boulder; YY}, pages = {991-994}, abstract = {During the last deglaciation (ca. 21-10 ka), freshening of the North Atlantic surface likely caused reductions in Atlantic meridional overturning circulation (AMOC); the mechanisms related to AMOC recovery remain poorly understood. Here we present three new deglacial surface temperature and delta O-18(seawater) (delta O-18(sw)) reconstructions from the western subtropical North and South Atlantic. Similarities to tropical Caribbean and western Atlantic delta O-18(sw) records suggest that a salty surface water mass accumulated in the western Atlantic from 27 degrees S to 33 degrees N during periods of reduced AMOC. However, delta O-18(sw) decreases led deep AMOC resumption by hundreds of years. We suggest that the northward export of salt previously trapped in the western Atlantic resulted in the early establishment of a shallow overturning circulation that eventually culminated in deep AMOC resumption, implying that AMOC may constitute a self-limiting system.}, issn = {0091-7613}, doi = {10.1130/g25080a.1}, author = {Carlson, A. E. and Oppo, D. W. and Came, R. E. and LeGrande, A. N. and Keigwin, L. D. and Curry, W. B.} } @article {336, title = {Atlantic meridional overturning circulation during the Last Glacial Maximum}, journal = {Science}, volume = {316}, year = {2007}, note = {id: 1897; ISI Document Delivery No.: 153XD Times Cited: 46 Cited Reference Count: 61 Cited References: ADKINS JF, 1997, NATURE, V390, P154 ADKINS JF, 1999, RECONSTRUCTING OCEAN, P103 ADKINS JF, 2003, EARTH PLANET SC LETT, V216, P109, DOI 10.1016/S0012-821X(03)00502-8 BACON MP, 1982, J GEOPHYS RES, V87, P2045 BICKERT T, 2004, S ATLANTIC LATE QUAT, P671 BOYLE EA, 1982, SCIENCE, V218, P784 BROECKER W, 1988, RADIOCARBON, V30, P261 CHASE Z, 2002, EARTH PLANET SC LETT, V204, P215 CLARK PU, 2002, NATURE, V415, P863 CONKRIGHT ME, 2002, WORLD OCEAN ATLAS 20 CURRY WB, 1982, QUATERNARY RES, V18, P218 CURRY WB, 2005, PALEOCEANOGRAPHY, V20, ARTN PA1017 DUPIESSY JC, 1980, NATURE, V286, P479 DUPLESSY JC, 1988, PALEOCEANOGRAPHY, V3, P343 DUPLESSY JC, 1989, RADIOCARBON, V31, P493 ELDERFIELD H, 2006, EARTH PLANET SC LETT, V250, P633, DOI 10.1016/j.epsl.2006.07.041 EMILIANI C, 1955, J GEOL, V63, P538 GANACHAUD A, 2000, NATURE, V408, P453 GEBBIE G, 2006, GEOCHEM GEOPHY GEOSY, V7, ARTN Q11N07 GHERARDI JM, 2005, EARTH PLANET SC LETT, V240, P710, DOI 10.1016/j.epsl.2005.09.061 HALL IR, 2006, GEOPHYS RES LETT, V33, ARTN L16616 HALL MM, 1982, DEEP-SEA RES, V29, P339 HEWITT CD, 2003, CLIM DYNAM, V20, P203, DOI 10.1007/s00382-002-0272-6 HIRSCHI JJM, 2006, GEOCHEM GEOPHY GEOSY, V7, ARTN Q10N04 HUYBERS P, 2007, J PHYS OCEANOGR, V37, P394, DOI 10.1175/JPO3018.1 KEIGWIN LD, 2004, PALEOCEANOGRAPHY, V19, ARTN PA4012 KISSEL C, 1999, EARTH PLANET SC LETT, V171, P489 KITOH A, 2001, GEOPHYS RES LETT, V28, P2221 KUCERA M, 2005, QUATERNARY SCI REV, V24, P951, DOI 10.1016/j.quascirev.2004.07.014 KUMAR N, 1993, NATURE, V362, P45 LEGRAND P, 1995, PALEOCEANOGRAPHY, V10, P1011 LEGRANDE AN, 2006, P NATL ACAD SCI USA, V103, P837 LYNCHSTIEGLITZ J, 1999, PALEOCEANOGRAPHY, V14, P360 LYNCHSTIEGLITZ J, 2001, GEOCHEM GEOPHY GEOSY, V2, DOI 10.1029/2001GC000208 LYNCHSTIEGLITZ J, 2003, TREATISE GEOCHEMISTR, V6, P433 LYNCHSTIEGLITZ J, 2006, GEOCHEM GEOPHY GEOSY, V7, ARTN Q10N03 MANABE S, 1988, J CLIMATOL, V1, P841 MANGINI A, 1998, NATURE, V392, P347 MARCHAL O, 2000, PALEOCEANOGRAPHY, V15, P625 MARCHITTO TM, 2000, PALEOCEANOGRAPHY, V15, P299 MARCHITTO TM, 2006, GEOCHEM GEOPHY GEOSY, V7, ARTN Q12003 MAROTZKE J, 1999, J GEOPHYS RES-OCEANS, V104, P29529 MATSUMOTO K, 1999, PALEOCEANOGRAPHY, V14, P149 MCCAVE IN, 2006, GEOCHEM GEOPHY GEOSY, V7, ARTN Q10N05 MCMANUS JF, 2004, NATURE, V428, P834, DOI 10.1038/nature02494 MIX AC, 2001, QUATERNARY SCI REV, V20, P627 OTTOBLIESNER BL, 2006, J CLIMATE, V19, P2526 PAUL A, 2003, PALEOCEANOGRAPHY, V18, ARTN 1058 PIOTROWSKI AM, 2005, SCIENCE, V307, P1933, DOI 10.1126/science.1104883 ROBINSON LF, 2005, SCIENCE, V310, P1469, DOI 10.1126/science.1114832 ROEMMICH D, 1985, DEEP-SEA RES, V32, P619 SARNTHEIN M, 1994, PALEOCEANOGRAPHY, V9, P209 SCHMITTNER A, 2005, GLOBAL BIOGEOCHEM CY, V19, ARTN GB3004 SHACKLETON NJ, 1988, NATURE, V335, P708 SHIN SI, 2003, CLIM DYNAM, V20, P127, DOI 10.1007/s00382-002-0260-x STOMMEL H, 1961, TELLUS, V13, P224 STREETER SS, 1979, SCIENCE, V203, P168 VELLINGA M, 2002, CLIMATIC CHANGE, V54, P251 WUNSCH C, 2003, QUATERNARY SCI REV, V22, P371 YU EF, 1996, NATURE, V379, P689 ZHANG R, 2005, J CLIMATE, V18, P1853 Lynch-Stieglitz, Jean Adkins, Jess F. Curry, William B. Dokken, Trond Hall, Ian R. Herguera, Juan Carlos Hirschi, Joel J. -M. Ivanova, Elena V. Kissel, Catherine Marchal, Olivier Marchitto, Thomas M. McCave, I. Nicholas McManus, Jerry F. Mulitza, Stefan Ninnemann, Ulysses Peeters, Frank Yu, Ein-Fen Zahn, Rainer Amer assoc advancement science Washington; YY}, pages = {66-69}, abstract = {The circulation of the deep Atlantic Ocean during the height of the last ice age appears to have been quite different from today. We review observations implying that Atlantic meridional overturning circulation during the Last Glacial Maximum was neither extremely sluggish nor an enhanced version of present-day circulation. The distribution of the decay products of uranium in sediments is consistent with a residence time for deep waters in the Atlantic only slightly greater than today. However, evidence from multiple water-mass tracers supports a different distribution of deep-water properties, including density, which is dynamically linked to circulation.}, issn = {0036-8075}, doi = {10.1126/science.1137127}, author = {Lynch-Stieglitz, J. and Adkins, J. F. and Curry, W. B. and Dokken, T. and Hall, I. R. and Herguera, J. C. and Hirschi, J. J. M. and Ivanova, E. V. and Kissel, C. and Marchal, O. and Marchitto, T. M. and McCave, I. N. and McManus, J. F. and Mulitza, S. and Ninnemann, U. and Peeters, F. and Yu, E. F. and Zahn, R.} } @article {624, title = {Gulf Stream density structure and transport during the past millennium}, journal = {Nature}, volume = {444}, year = {2006}, note = {Lund, David CLynch-Stieglitz, JeanCurry, William BengResearch Support, U.S. Gov{\textquoteright}t, Non-P.H.S.England2006/12/01 09:00Nature. 2006 Nov 30;444(7119):601-4.}, month = {Nov 30}, pages = {601-4}, abstract = {The Gulf Stream transports approximately 31 Sv (1 Sv = 10(6) m(3) s(-1)) of water and 1.3 x 10(15) W of heat into the North Atlantic ocean. The possibility of abrupt changes in Gulf Stream heat transport is one of the key uncertainties in predictions of climate change for the coming centuries. Given the limited length of the instrumental record, our knowledge of Gulf Stream behaviour on long timescales must rely heavily on information from geologic archives. Here we use foraminifera from a suite of high-resolution sediment cores in the Florida Straits to show that the cross-current density gradient and vertical current shear of the Gulf Stream were systematically lower during the Little Ice Age (ad approximately 1200 to 1850). We also estimate that Little Ice Age volume transport was ten per cent weaker than today{\textquoteright}s. The timing of reduced flow is consistent with temperature minima in several palaeoclimate records, implying that diminished oceanic heat transport may have contributed to Little Ice Age cooling in the North Atlantic. The interval of low flow also coincides with anomalously high Gulf Stream surface salinity, suggesting a tight linkage between the Atlantic Ocean circulation and hydrologic cycle during the past millennium.}, issn = {0028-0836 (Linking)}, doi = {10.1038/nature05277}, author = {Lund, D. C. and Lynch-Stieglitz, J. and Curry, W. B.} } @article {1026, title = {Meridional overturning circulation in the South Atlantic at the last glacial maximum}, journal = {Geochemistry Geophysics Geosystems}, volume = {7}, year = {2006}, note = {092siTimes Cited:17Cited References Count:46}, month = {Oct 3}, abstract = {The geostrophic shear associated with the meridional overturning circulation is reflected in the difference in density between the eastern and western margins of the ocean basin. Here we examine how the density difference across 30 degrees S in the upper 2 km of the Atlantic Ocean ( and thus the magnitude of the shear associated with the overturning circulation) has changed between the last glacial maximum and the present. We use oxygen isotope measurements on benthic foraminifera to reconstruct density. Today, the density in upper and intermediate waters along the eastern margin in the South Atlantic is greater than along the western margin, reflecting the vertical shear associated with the northward flow of surface and intermediate waters and the southward flowing North Atlantic Deep Waters below. The greater density along the eastern margin is reflected in the higher delta(18)O values for surface sediment benthic foraminifera than those found on the western margin for the upper 2 km. For the last glacial maximum the available data indicate that the eastern margin foraminifera had similar delta(18)O to those on the western margin between 1 and 2 km and that the gradient was reversed relative to today with the higher delta(18)O values in the western margin benthic foraminifera above 1 km. If this reversal in benthic foraminifera delta(18)O gradient reflects a reversal in seawater density gradient, these data are not consistent with a vigorous but shallower overturning cell in which surface waters entering the Atlantic basin are balanced by the southward export of Glacial North Atlantic Intermediate Water.}, issn = {1525-2027}, doi = {10.1029/2005GC001226}, author = {Lynch-Stieglitz, J. and Curry, W. B. and Oppo, D. W. and Ninneman, U. S. and Charles, C. D. and Munson, J.} } @article {2006, title = {Glacial water mass geometry and the distribution of d 13 C of SCO 2 in the western Atlantic Ocean}, journal = {Paleoceanography}, volume = {20}, year = {2005}, note = {id: 416}, month = {2005}, author = {Curry, W. B. and Oppo, D. W.} } @article {1016, title = {Atlantic Ocean circulation during the Younger Dryas: Insights from a new Cd/Ca record from the western subtropical South Atlantic}, journal = {Paleoceanography}, volume = {18}, year = {2003}, note = {749rtTimes Cited:30Cited References Count:39}, month = {Nov 25}, abstract = {[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 ( Cd-W) for the last glacial are consistent with the production of NAIW and its export into the South Atlantic. At similar to 14.5 ka concurrently with the onset of the Bolling- Allerod 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 Cd-W 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 similar to 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.}, issn = {0883-8305}, doi = {10.1029/2003PA000888}, author = {Came, R. E. and Oppo, D. W. and Curry, W. B.} } @article {772, title = {A geostrophic transport estimate for the Florida Current from the oxygen isotope composition of benthic foraminifera}, journal = {Paleoceanography}, volume = {14}, year = {1999}, note = {198xcTimes Cited:81Cited References Count:45}, month = {Jun}, pages = {360-373}, abstract = {We present a new method for the quantitative reconstruction of upper ocean flows for during times in the past. For the warm (T>5 degrees C) surface ocean, density can be accurately reconstructed from calcite precipitated in equilibrium with seawater, as both of these properties increase with decreasing temperature and increasing salinity. Vertical density profiles can be reconstructed from the oxygen isotopic composition of benthic foraminifera. The net volume transport between two vertical density profiles can be calculated using the geostrophic method. Using benthic foraminifera from surface sediment samples from either side of the Florida Straits (Florida Keys and Little Bahama Bank), we reconstruct two vertical density profiles and calculate a volume transport of 32 Sv using this method. This agrees well with estimates from physical oceanographic methods of 30-32 Sv for the mean annual volume transport. We explore the sensitivity of this technique to various changes in the relationship between temperature and salinity as well as salinity and the oxygen isotopic composition of seawater.}, issn = {0883-8305}, doi = {10.1029/1999pa900001}, author = {Lynch-Stieglitz, J. and Curry, W. B. and Slowey, N.} } @article {2241, title = {Millennial-scale climate changes in ventilation of the thermocline, intermediate and deep waters of the glacial North Atlantic}, journal = {Geophysical Monograph series}, volume = {AGU Chapman Conference volume 112}, year = {1999}, note = {id: 207}, month = {1999}, pages = {59-76}, author = {Curry, W. B. and Marchitto, T. M. and McManus, J. F. and Oppo, D. W. and L, Laarkamp K.} } @inbook {1436, title = {The overturning circulation of the glacial Atlantic: A view from the top}, booktitle = {Reconstructing Ocean History: A Window into the Future}, year = {1999}, note = {id: 1364}, month = {1999}, pages = {7-31}, publisher = {Kluwer Academic/Plenum}, organization = {Kluwer Academic/Plenum}, address = {New York}, author = {Lynch-Stieglitz, J. and Curry, W. B. and Slowey, N. and Schmidt, G. A.}, editor = {Abrantes, F.} } @conference {1727, title = {The overturning circulation of the glacial Atlantic: A view from the top}, booktitle = {Sixth International Conference on Paleoceanography}, year = {1999}, note = {id: 1337}, month = {1999}, author = {Lynch-Stieglitz, J. and Curry, W. B. and Slowey, N. C.} } @article {2225, title = {Variability in shallow- and intermediate-water hydrography during the last climate cycle of the Quaternary}, journal = {EOS}, volume = {80}, year = {1999}, note = {id: 170}, month = {1999}, pages = {F10}, author = {McManus, J. F. and Healey, S. L. and Oppo, D. W. and Curry, W. B.} } @article {758, title = {Weaker Gulf Stream in the Florida straits during the last glacial maximum}, journal = {Nature}, volume = {402}, year = {1999}, note = {264pcTimes Cited:122Cited References Count:31}, month = {Dec 9}, pages = {644-648}, abstract = {As it passes through the Florida Straits, the Gulf Stream consists of two main components: the western boundary flow of the wind-driven subtropical gyre and the northward-flowing surface and intermediate waters which are part of the {\textquoteright}global conveyor belt{\textquoteright} compensating for the deep water that is exported from the North Atlantic Ocean(1), The mean flow through the Straits is largely in geostrophic balance and is thus reflected in the contrast in seawater density across the Straits(2). Here we use oxygen-isotope ratios of benthic foraminifera which lived along the ocean margins on the boundaries of the Florida Current during the Last Glacial Maximum to determine the density structure in the water and thereby reconstruct transport through the Straits using the geostrophic method-a technique which has been used successfully for estimating present-day flow(3). Our data suggest that during the Last Glacial Maximum, the density contrast across the Florida Straits was reduced, with the geostrophic flow, referenced to the bottom of the channel, at only about two-thirds of the modern value. If the wind-driven western boundary flow was not lower during the Last Glacial Maximum than today, these results indicate a significantly weaker conveyor-belt component of the Gulf Stream compared to present-day values. Whereas previous studies based on tracers suggested that deep waters of North Atlantic origin were not widespread during glacial times, indicating either a relatively weak or a shallow overturning cell, our results provide evidence that the overturning cell was indeed weaker during glacial times.}, issn = {0028-0836}, doi = {10.1038/45204}, author = {Lynch-Stieglitz, J. and Curry, W. B. and Slowey, N.} } @article {762, title = {Millennial-scale changes in North Atlantic circulation since the last glaciation}, journal = {Nature}, volume = {393}, year = {1998}, note = {Zt988Times Cited:106Cited References Count:30}, month = {Jun 11}, pages = {557-561}, abstract = {Ocean circulation is closely linked to climate change on glacial-interglacial and shorter timescales. Extensive reorganizations in the circulation of deep and intermediate-depth waters in the Atlantic Ocean have been hypothesized for both the last glaciation(1-6) and the subsequent Younger Dryas cold interval(3,6-10), but there has been little palaeoceanographic study of the subtropical gyres(11-13). These gyres are the dominant oceanic features of wind-driven circulation, and as such they reflect changes in climate and are a significant control on nutrient cycling and, possible, atmospheric CO2 concentrations. Here we present Cd/Ca ratios in the shells of benthic foraminifera from the Bahama banks that confirm previous suggestions(11,12) that nutrient concentrations in the North Atlantic subtropical gyre were much lower during the Last Glacial Maximum than they are today (up to 50\% lower according to our data). These contrasting nutrient burdens imply much shorter residence times for waters within the thermocline of the Last Glacial Maximum. Below the glacial thermocline, nutrient concentrations were reduced owing to the presence of Glacial North Atlantic Intermediate Water. A high-resolution Cd/Ca record from an intermediate depth indicates decreased nutrient concentrations during the Younger Dryas interval as well, mirroring opposite changes at a nearby deep site(3,9). Together, these observations suggest that the formation of deep and intermediate waters-North Atlantic Deep Water and Glacial North Atlantic Intermediate Water, respectively-wax and wane alternately on both orbital and millennial timescales.}, issn = {0028-0836}, doi = {10.1038/31197}, author = {Marchitto, T. M. and Curry, W. B. and Oppo, D. W.} } @article {2267, title = {North Atlantic gyre ventilation and intermediate water formation during the last glaciation and Younger Dryas}, journal = {Nature}, volume = {393}, year = {1998}, note = {id: 208}, month = {1998}, pages = {557-561}, author = {Marchitto, T. M. and Curry, W. B. and W, Oppo D.} } @article {779, title = {Synchronous, high-frequency oscillations in tropical sea surface temperatures and North Atlantic Deep Water production during the last glacial cycle}, journal = {Paleoceanography}, volume = {12}, year = {1997}, note = {Wd891Times Cited:109Cited References Count:63}, month = {Feb}, pages = {1-14}, abstract = {Stable isotopic measurements of G. sacculifer and C. wuellerstorfi in a core from the western equatorial Atlantic imply that there are parallel, suborbital oscillations in surface water hydrography and deep water circulation occurring during oxygen isotope stages 2 and 3. Low values of G. sacculifer delta(18)O accompany high values of C. wuellerstorfi delta(13)C, linking warmer sea surface temperatures (SSTs) in the tropics with increased production of lower North Atlantic Deep Water (NADW). The amplitude of the delta(18)O oscillations is 0.6 parts per thousand (or 2 degrees-3 degrees C), which is superimposed on a glacial/interglacial amplitude of about 2.1 parts per thousand,. Using the G. sacculifer delta(18)O data, we calculate that surface waters were colder during stage 2 than calculated by CLIMAP [1976, 1981]. The longer-period (> 2 kyr) oscillations in air temperature recorded in the Greenland and Antarctic ice cores appear to correlate with oscillations in sea surface temperature in the equatorial Atlantic. The magnitude of these oscillations in tropical SST is too large to have resulted from changes in meridional heat transport caused by the global conveyor alone. The apparent synchroneity of equatorial SST and polar air temperature changes, as well as the amplitude of the SST changes at the equator, are consistent with the climate effects expected from changes in the atmosphere{\textquoteright}s greenhouse gas content (H(2)0(vapor), CO2, and CH4).}, issn = {0883-8305}, doi = {10.1029/96pa02413}, author = {Curry, W. B. and Oppo, D. W.} } @article {751, title = {Direct U-Th dating of marine sediments from the two most recent interglacial periods}, journal = {Nature}, volume = {383}, year = {1996}, note = {Vh315Times Cited:39Cited References Count:40}, month = {Sep 19}, pages = {242-244}, abstract = {A KNOWLEDGE of the age of marine sediments is necessary to determine the timing of events and rates of processes in the marine realm, and the relationships among marine and other climatically sensitive records. The establishment of an accurate chronology for Pleistocene marine sediments beyond the range of radiocarbon dating (approximately the past 45 kyr) has therefore been a goal of palaeoceanographers for decades. Early attempts(1,2) based on measurements of the radionuclides Th-230 and Pa-231 mere beset with problems, and subsequent studies focused on tying fluctuations in marine sediment oxygen-isotope records to events such as the formation of col al reef terraces and changes in the Earth{\textquoteright}s magnetic polarity(3,4), and tuning the resultant chronologies to the Earth{\textquoteright}s orbitally driven insolation variations(5-8). But these chronologies (especially the age and duration of the last interglacial period) have been challenged by several studies(9-12), raising questions about the fundamental cause of Pleistocene climate fluctuations. Here we report the direct U-Th dating of aragonite-rich marine sediments from the Bahamas, and present an accurately dated marine oxygen-isotope record for the last two interglacials. We obtain dates of 120-127 kyr BP for the last interglacial and 189-190 kyr np for the late stage 7 interglacial. These dates are in accord with the general theory of orbitally forced climate fluctuations and demonstrate the potential of our direct-dating approach for developing an absolute chronology for the Pleistocene marine oxygen-isotope record.}, issn = {0028-0836}, doi = {10.1038/383242a0}, author = {Slowey, N. C. and Henderson, G. M. and Curry, W. B.} } @article {2314, title = {East Asian monsoon variations; linkage to northern hemisphere millenniallll-scale climate oscillations}, journal = {Supplement to EOS}, volume = {77}, year = {1996}, note = {id: 56}, month = {1996}, pages = {19}, author = {Oppo, D. W. and Deiner, L. and Curry, W. B. and Norris, R. D.} } @inbook {1394, title = {Late Quaternary deep circulation in the western equatorial Atlantic (Book Section)}, booktitle = {The South Atlantic: Present and Past Circulation}, year = {1996}, note = {id: 1336}, month = {1996}, pages = {577-598}, author = {Curry, W. B.}, editor = {Berger, W.} } @article {785, title = {Glacial-Interglacial Differences in Circulation and Carbon Cycling within the Upper Western North-Atlantic}, journal = {Paleoceanography}, volume = {10}, year = {1995}, note = {Rm032Times Cited:80Cited References Count:86}, month = {Aug}, pages = {715-732}, abstract = {We investigated glacial-interglacial changes in the circulation and carbon cycling in the western North Atlantic subtropical gyre using hydrographic data and downcore records of the stable isotopic compositions of individual shells of Bahamian benthic foraminifera. Potential temperature-salinity-depth relations show that modern thermocline (similar to 200-1000 m) and deep (similar to 1000-2000 m) waters in the Providence Channels, Bahamas, originate in the Sargasso Sea and are typical of the subtropical gyre. Gradients in the stable isotopic compositions of late Holocene Planulina and Cibicidoides species from the bank margins (similar to 400 to 1500 m depth) reflect temperature, nutrient, and isotopic gradients of modern subtropical gyre waters. The difference between the delta(18)O of glacial maximum and late Holocene foraminifera is similar to 2.1 parts per thousand for the upper 900 m of the water column and similar to 1.6 parts per thousand for deeper waters, indicating that these waters were similar to 4 degrees C and similar to 2 degrees C cooler, respectively, during glacial time. The glacial temperature gradient (dT/dz) was similar to today, while the base of the thermocline was similar to 100 m shallower. These results differ significantly from our earlier results from multiple shell delta(18)O analyses, which implied upper thermocline waters were only similar to 1 degrees C cooler and dT/dz was greater during the glacial maximum. The difference occurs because bioturbation adversely affects multiple shell analyses of glacial-aged samples from shallow water depths. At all depths above 1500 m, foraminiferal delta(13)C are greater during the glacial maximum than the late Holocene by at least 0.1 to 0.2 parts per thousand (as much as 0.6 parts per thousand in the lower thermocline), indicating that nutrient concentrations throughout the thermocline were reduced and there was no oxygen minimum zone during the glacial maximum. This suggests greater, more uniform ventilation of the thermocline. Results of single and multiple shell delta(13)C analyses of glacial age foraminifera compare favorably because samples most affected by mixing correspond to water depths where the glacial-interglacial change of delta(13)C was small. Cooler upper ocean waters during the glacial maximum reflect cooler temperatures at the ocean surface where isopycnal surfaces outcrop, including large areas of the subtropical ocean. A shallower thermocline base is consistent with southward migration of the northern edge of the subtropical gyre or increased mode water production. Enhanced thermocline ventilation is consistent with more vigorous winds and all isopycnal surfaces outcropping in the area of Ekman downwelling.}, issn = {0883-8305}, doi = {10.1029/95pa01166}, author = {Slowey, N. C. and Curry, W. B.} } @article {755, title = {The Role of the Deep-Ocean in North-Atlantic Climate-Change between 70-Kyr and 130-Kyr Ago}, journal = {Nature}, volume = {371}, year = {1994}, note = {Ph254Times Cited:159Cited References Count:32}, month = {Sep 22}, pages = {323-326}, abstract = {THE suggestion(1) that changes in North Atlantic Deep Water (NADW) production are linked through surface heat flux to the atmospheric temperature over Greenland is supported by earlier indications(2,3) that NADW production decreased during glacial times, and by the subsequent finding(4-6) that it declined during the Younger Dryas cool period at the end of the last glaciation. Changes in North Atlantic surface temperatures have been found? to mirror high-frequency temperature changes recorded in Greenland ice cores over the past 80 kyr, but the connection to abyssal circulation has yet to be established, except for one or two isolated oscillations(8,9). Here we present carbon and oxygen isotope analyses of benthic foraminifera in a high-resolution North Atlantic deepsea sediment core for the period 70-130 kyr ago. These data allow us to reconstruct the history of NADW production, which shows a close correlation with Greenland climate variability for much of this time interval, suggesting that the climate influence of NADW variability was widespread. We see no evidence, however, for changes in NADW production during substage 5e (the Eemian interglacial period), in contrast with recent ice-core data(10) which suggest severe climate instability in Greenland during this time period. Our results may support suggestions, based on data from a second ice core, that this apparent instability is am artefact caused by ice flow(11). Alternatively, the Eemian climate instability may have had a different origin from the subsequent climate events.}, issn = {0028-0836}, doi = {10.1038/371323a0}, author = {Keigwin, L. D. and Curry, W. B. and Lehman, S. J. and Johnsen, S.} }