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  • 2005-2009  (211)
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  • 1
    Publication Date: 2017-01-04
    Description: Author Posting. © The Author, 2004. This is the author's version of the work. It is posted here by permission of Elsevier B. V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 52 (2005): 429-463, doi:10.1016/j.dsr2.2004.11.001.
    Description: Recent satellite-tracked surface drifter trajectories were analyzed to describe the mean currents and eddies in the Caribbean Sea. The structure of the Caribbean Current and its variability were determined from high-resolution ½ degree maps of the mean velocity and eddy kinetic energy. Looping drifter trajectories were used to identify discrete cyclones and anticyclones, and their characteristics were described and related to the structure of the mean flow. The translation rate of eddies in different areas was found to be similar to the mean velocity of the local background flow fields suggesting that the eddies were largely advected by the background flow. Ten energetic anticyclones translated westward at 13 cm/sec in the Venezuela and Colombia Basins. These anticyclones tended to lie in two bands, centered near 15ºN and 17ºN, coinciding with two jets of the Caribbean Current. The northern weaker jet contains water primarily from the North Atlantic, the southern stronger jet contains water from the tropical and South Atlantic. The anticyclones are thought to have formed in the eastern Caribbean from the anticyclonic vorticity derived from North Brazil Current rings. The ring vorticity enters the eastern Caribbean through island passages and is probably amplified by the anticyclonic shear on the northern side of the jets. Southwest of Cuba a cyclone-anticyclone pair was observed to slowly (~ 2 cm/sec) translate westward into the Yucatan Current. The cyclone was tracked for 10.5 months with four drifters, making it the longest-tracked of the Caribbean eddies.
    Description: Funding was provided by National Science Foundation grants OCE 97-29765 and OCE 01-36477.
    Keywords: Surface drifters ; Caribbean Current ; Caribbean eddies ; Eddies ; North Brazil Current rings ; Meridional overturning circulation ; Intra-Americas Seas ; Caribbean Sea ; Colombia Basin ; Venezuela Basin ; Yucatan Basin ; Antilles
    Repository Name: Woods Hole Open Access Server
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  • 2
    Publication Date: 2022-05-25
    Description: Neutrally buoyant SOFAR floats at nominal depths of 800 m, 1800 m, and 3300 m were tracked acoustically for 3.7 years in the vicinity of the western boundary and the equator of the Atlantic Ocean. Trajectories and summaries from the whole experiment are shown along with detailed trajectories from the second setting of the listening stations, October 1990 to September 1992. Some highlights are mentioned below. Trajectories at 1800 m revealed a swift narrow southward flowing deep western boundary current (DWBC) extending from 7°N across the equator. Two floats directly crossed the equator in the DWBC and went to 10°S. Two other floats left the DWBC near the equator and drifted eastward. Three floats entered the DWBC from the equatorial current system and drifted southward. No obvious DWBC or swift equatorial currents were observed by the 3300 m floats. The 800 m floats plus some surface drifters measured seven anticyclonic eddies as they translated northwestward along the coast of South America in a band from the equator to 12°N. One of the floats (28) entered the Caribbean where tracking stopped. This float was again tracked as it drifted across the mid-Atlantic Ridge and entered the Canary Basin near 34°N 28°W after a gap of 2.7 years. We infer that this float went westward though the Caribbean and northeastward in the Gulf Stream. Float 17 drifted northward from 10°N to 22°N in an eastern boundary current off the coast of West Africa. Floats between 6°N-6°S (roughly) drifted long distances zonally in the equatorial current system.
    Description: Funding was provided by the National Science Foundation through Grants Nos. OCE85-21082, OCE85-17375, and OCE91-14656.
    Keywords: SOFAR floats ; Sound Fixing And Ranging floats ; Equatorial currents
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 3
    Publication Date: 2022-05-25
    Description: Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Progress In Oceanography 76 (2008): 466-486, doi:10.1016/j.pocean.2008.01.005.
    Description: Recent global warming caused by humans and the prediction of a reduced Atlantic Ocean meridional overturning circulation in the future has increased interest in the role of the overturning circulation in climate change. A schematic diagram of the overturning circulation called the “Great Ocean Conveyor Belt,” published by Wallace Broecker in 1987, has become a popular image that emphasizes the inter-connected ocean circulation and the northward flux of heat in the Atlantic. This would appear to be a good time to review the development of the conveyor belt concept and summarize the history of overturning circulation schematics. In the nineteenth century it was thought that symmetric overturning circulation cells were located on either side of the equator in the Atlantic. As new hydrographic measurements were obtained in the late nineteenth century and early twentieth century, circulation schematics in the early twentieth century began to show the inter-hemispheric overturning circulation in the Atlantic. In the second half of the twentieth century schematics showed the global ocean overturning circulation including connections between the Atlantic and the Pacific and Indian Oceans. Some recent schematics of the overturning circulation show its complexities, but as more information is included these schematics have also become complex and not as easy to understand as the simple Broecker 1987 version.
    Keywords: Ocean conveyor belt ; Meridional overturning circulation ; Thermohaline circulation ; Global ocean circulation ; Schematic circulation diagrams ; History of ocean circulation
    Repository Name: Woods Hole Open Access Server
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  • 4
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 56 (2009): 1615-1632, doi:10.1016/j.dsr.2009.06.002.
    Description: A comprehensive analysis of velocity data from subsurface floats in the northwestern tropical Atlantic at two depth layers is presented: one representing the Antarctic Intermediate Water (AAIW, pressure range 600–1050 dbar), the other the upper North Atlantic Deep Water (uNADW, pressure range 1200–2050 dbar). New data from three independent research programs are combined with previously available data to achieve blanket coverage in space for the AAIW layer, while coverage in the uNADW remains more intermittent. Results from the AAIW mainly confirm previous studies on the mean flow, namely the equatorial zonal and the boundary currents, but clarify details on pathways, mostly by virtue of the spatial data coverage that sets float observations apart from e. g. shipborne or mooring observations. Mean transports in each of five zonal equatorial current bands is found to be between 2.7 and 4.5 Sv. Pathways carrying AAIW northward beyond the North Brazil Undercurrent are clearly visible in the mean velocity field, in particular a northward transport of 3.7 Sv across 16° N between the Antilles islands and the Mid- Atlantic Ridge. New maps of Lagrangian eddy kinetic energy and integral time scales are presented to quantify mesoscale activity. For the uNADW, mean flow and mesoscale properties are discussed as data availability allows. Trajectories in the uNADWeast of the Lesser Antilles reveal interactions between the Deep Western Boundary Current (DWBC) and the basin interior, which can explain recent hydrographic observations of changes in composition of DWBC water along its southward flow.
    Description: MOVE was funded by the Bundesministerium fu¨r Bildung und Forschung (grants 03F0246A and 03F0377B) as well as by the Deutsche Forschungsgemeinschaft (grant SE815/21), NBC by the National Science Foundation through grants OCE 97-29765 and OCE 01-36477, and SAMBA was fully supported by Ifremer.
    Keywords: Floats ; Tropical Atlantic ; Antarctic Intermediate Water ; North Atlantic Deep Wat ; Equatorial currents
    Repository Name: Woods Hole Open Access Server
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  • 5
    Publication Date: 2022-05-25
    Description: This is the final data report of all acoustically tracked RAFOS float data collected by the Woods Hole Oceanographic Institution in 1996-1999 during the Atlantic Climate Change Experiment (ACCE). The RAFOS float component of ACCE, entitled "Warm Water Pathways and Intergyre Exchange in the Northeastern North Atlantic," was designed to measure the warm water currents entering the northeastern North Atlantic which become the source of intermediate and deep waters in the subpolar region. The experiment was comprised of three RAFOS float deployments on the R/V Knorr: the first in fall 1996 along the continental slope seaward of Porcupine Bank, the second in spring 1997 along the mid-Atlantic Ridge, and the final deployment in fall 1997 along both the Ridge and the Bank. Seventy floats were deployed, 13 RAFOS and 2 ALFOS in fall 1996, 14 RAFOS in spring 1997, and 41 RAFOS in fall 1997. The isobaric ALFOS floats were ballasted for 800 decibars and were launched to monitor the regions' sound sources during the experiment. The RAFOS floats were isopycnal and ballasted for the 27.5 sigma-t surface to target the intermediate-depth North Atlantic and Poleward Eastern Boundary Currents. The objectives of the Lagrangian float study were (1) to provide a quantitative description of the bifurcation of the North Atlantic Current east of the Mid-Atlantic Ridge, (2) to assess the importance of meridional eddy fluxes, compared to large-scale advection, in the northward flux of heat and salt in the northeastern North Atlantic, and (3) to establish the degree of continuity of the Poleward Eastern Boundary Current as it flows to the entrance of the Norwegian Sea and the fate of the Mediterranean Outflow Water carried by this current.
    Description: Funding was provided by the National Science Foundation under Grant Number OCE-9831877.
    Keywords: North Atlantic Circulation ; Subpolar region ; Floats ; Knorr (Ship : 1970-) Cruise KN147 ; Knorr (Ship : 1970-) Cruise KN151 ; Knorr (Ship : 1970-) Cruise KN154
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 6
    Publication Date: 2022-05-25
    Description: As part of the Semaphore Experiment four Meddies (Mediterranean Water Eddies) were discovered in the Canary Basin and tracked with freely drifting RAFOS floats. An additional Meddy was discovered off Lisbon by Pingree (1995) and also tracked with RAFOS floats. One large and energetic Meddy, discovered 1700 km west of Cape St. Vincent, Portugal, set a distance and speed record as it translated another 1700 km southwestward at 3.9 cm/sec during the 1.5 years. This Meddy traveled 57% of the distance from Cape St. Vincent toward the spot McDowell and Rossby (1978) found a possible Meddy north of the Dominican Republic. Four Meddies collided with tall seamounts which seemed to disrupt the normal swirl velocity perhaps fatally in three cases. One Meddy appeared to bifurcate when it collided with seamounts. This report describes the float trajectories in the Meddies and summarizes the main results.
    Description: Funding was provided by the National Science Foundation under contract number OCE 93-01234.
    Keywords: Meddies ; RAFOS floats ; Semaphore ; Ocean currents ; Mediterranean Sea ; Charles Darwin (Ship) Cruise ; Alcyon (Ship) Cruise ; Laperouse (Ship) Cruise ; Ailette (Ship) Cruise ; D'Entrecasteaux (Ship) Cruise ; Suroit (Ship) Cruise ; Pr. Stockman (Ship) Cruise
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 7
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    Woods Hole Oceanographic Institution
    Publication Date: 2022-05-25
    Description: The transatlantic route of Columbus was simulated incorporating historical winds, currents and hypothetical magnetic variation in order to estimate where the first landfall occured. Earlier simulations using an 1899 map by Van Bemmelen and assuming zero magnetic variation in the Bahamas to produce a landfall near San Salvador (Watlings Island). New theories postulating a Geometric league of 2.67 nautical miles and a westerly magnetic variation of approximately one point (11.25°) for the western terminus result in a landfall near the Turks and Caicos Islands. A westerly variation of this magnitude in the Bahamas has been inferred from early charts - the islands are shown several degrees too far north, which would have occurred if early navigators had been set imperceptibly southward by westerly variation - by studies of directions within the islands, and by studies of early navigation books. The simulation of subsequent voyages by Columbus lend further weight to a westerly variation of about one point in the region of Bahamas. Our work shows that a Grand Turk landfall cannot be ruled out based on the transatlantic portion of the voyage as has been suggested in the past. A more accurate simulation of the voyage and first landfall still requires a more accurate representation of the field of magnetic variation.
    Description: Funding was provided by a grant from the Nova Albion Foundation and the Government of the Turks and Caicos Islands.
    Keywords: Columbus voyage ; Historical currents ; Magnetic compass navigation
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 8
    Publication Date: 2022-05-25
    Description: In October, 1984, the Woods Hole Oceanographic Institution SOFAR float group began a three and a half year field program to measure the velocity field of the Mediterranean water in the eastern North Atlantic. The principal scientific goal was to learn how the Mediterranean salt tongue is produced by the general circulation and the eddy diffusion of the Canary Basin. Thirty-two floats were launched at depths near 1100 m: 14 in a cluster centered on 32°N, 24°W, with nearest neighbors at 20 km spacing, 10 at much wider spacing to explore regional variations of first order flow statistics, and 8 in three different Meddies (Mediterranean water eddies) in collaboration with investigators from Scripps Institution of Oceanography and the University of Rhode Island. The floats were launched in 1984 and 1985, and tracked with U.S. and French ALSs (moored listening stations) from October 1984 to June 1988. This report includes a summary of the whole three and a half year experiment, the final year and a half of data processed from the third ALS setting (October 1986-June 1988), and the first deep sea test of Bobber EB014 in the eastern subtropical North Atlantic (May 1986-May 1988). Approximately 60 years of float trajectories were produced during the three and a half years of the experiment.
    Description: Funding was provided by the National Science Foundation through Grant Nos. OCE 82-14066, OCE 85-17375, OCE 86-00055, OCE 88-22826.
    Keywords: SOFAR floats ; Canary Basin ; Mediterranean outflow ; Jean Charcot (Ship) Cruise
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 9
    Publication Date: 2022-05-25
    Description: Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 54 (2007): 1361-1389, doi:10.1016/j.dsr.2007.04.010.
    Description: Surface drifters and subsurface floats drifting at depths near 800 m were used to study the pathways of warm salty Indian Ocean water leaking into the South Atlantic that is a component of the upper limb of the Atlantic meridional overturning circulation. Four drifters and 5 floats drifted from the Agulhas Current directly into the Benguela Current. Others looped for various amounts of time in Agulhas rings and cyclones, which translated westward into the Atlantic contributing a large part of Indian Ocean leakage. Agulhas rings translated into the Benguela Current where they slowly decayed. Some large blob-like Agulhas rings with irregular shapes were found in the southeastern Cape Basin. Drifter trajectories suggest these rings become more circular with time eventually evolving into the circular rings observed west of the Walvis Ridge. Agulhas cyclones, which form on the north side of the Agulhas south of Africa, translated southwestward (to 6°E) and contributed water to the southern Cape Basin. A new discovery is a westward extension from the mean Agulhas retroflection measured by westward drifting floats near 41ºS out to at least 5ºW with some floats as far west as 25ºW. The Agulhas extension appears to split the South Atlantic Current into two branches and to transport Agulhas water westward where it is mixed and blended with eastward-flowing water from the western Atlantic. The blended mixture flows northeastward in the northern branch of the South Atlantic Current and into the Benguela Current. Agulhas leakage transport was estimated from drifters and floats to be at least 15 Sv in the upper 1,000 m, which is equivalent to the transport of the upper layer meridional overturning circulation. It is suggested that the major component of the upper layer overturning circulation in the Atlantic is Agulhas leakage.
    Description: Funds for this research were provided by National Science Foundation grants OCE-0236654 to the Woods Hole Oceanographic Institution and OCE-0236527 to the Woods Hole Research Center.
    Repository Name: Woods Hole Open Access Server
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  • 10
    Publication Date: 2022-05-26
    Description: Neutrally buoyant SOFAR floats at nominal depths of 800, 1800, and 3300 m were tracked for 21 months in the vicinity of western boundary currents near 6N and at several sites in the Atlantic near 11N and along the equator. Trajectories at 1800 m show a swift (〉50 cm/sec), narrow (100 km wide) southward-flowing Deep Western Boundary Current (DWBC) extending from 7N to the equator. At times (February-March 1989) DWBC water turned eastward and flowed along the equator and at other times (August-September 1990) the DWBC crossed the equator and continued southward. The mean velocity near the equator was eastward from February 1989 to February 1990 and westward from March 1990 to November 1990. Thus the cross-equatorial flow in the DWBC appeared to be linked to the direction of equatorial currents which varied over periods of more than a year. No obvious DWBC nor swift equatorial current was observed by 3300 m floats. Eight-hundred-meter floats revealed a northwestward intermediate level western boundary current although flow patterns were complicated. Three floats that significantly contributed to the northwestward flow looped in anticyclonic eddies that translated up the coast at 8 cm/sec. Six 800 m floats drifted eastward along the equator between 5S and 6N at a mean velocity of 11 cm/sec; one reached 5W in the Gulf of Guinea, suggesting that the equatorial current extended at least 35-40° along the equator. Three of these floats reversed direction near the end of the tracking period, implying low frequency fluctuations.
    Description: Funding was provided by the National Science Foundation through Grant Nos. OCE-8521082, OCE-8517375, and OCE-9114656.
    Keywords: SOFAR floats ; Equatorial currents ; Deep Western Boundary Current ; Oceanus (Ship : 1975-) Cruise ; Columbus Iselin (Ship) Cruise
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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