Circulation Oceanus REPORTS on RESEARCH at the WOODS HOLE OCEANOGRAPHIC INSTITUTION
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REPORTS ON RESEARCH AT THE WOODS HOLE OCEANOGRAPHIC INSTITUTION Volume 37, Number 1 Spring 1994 Atlantic Ocean * .,' I Circulation Oceanus REPORTS ON RESEARCH AT THE WOODS HOLE OCEANOGRAPHIC INSTITUTION Vol. 37, No. 1 Spring 1994 ISSN 0029-8182 Atlantic Ocean Circulation The Atlantic Ocean 1 Progress in Describing and Interpreting Its Circulation By Michael S. McCartney A Primer on Ocean Currents 3 Mi'i'i^iiri'ii/fi/tK <niil Lin/in nfriii/xicn/ Oceanographers Towards a Model of Atlantic Ocean Circulation 5 The Plumbing of the Cl/ii/nlr's Rnil/u/m- : By MichaelS. Mri''nrli/i // Dynamics and Modeling of Marginal Sea Outflows 9 Out They Go, Doini, and Around tin' \\brlil By James F. Price Meddies, Eddies, Floats, and Boats 12 1 How Do Mediterranean ni/d Atlantic Waters .l/ii .-' By Amy Bower Where Currents Cross 16 Interarlnni the and the Western Current t CiilfSln'am >i i nuii'< is published semi-annually by the Woods Hole of Deep Boundary Rolinl S. P/,i;iil Oceanographic Institution. Woods Hole. MA (C~i4:i By 508-457-2 i.cxi 271H Giant Eddies of South Atlantic Water Invade the North 19 iii-ciniiix and its logo are Registered Trademarks ol the Woods Hole Oceanographio Institution, All Rights Reserved Disrupted Flou- andSwiriing H'ati'n By Philip L Richardann In North America, an Oceanns Package. including<Vivj//.s magazine, Woods Hole Currents la l^-pagc tabloid-size The Deep Basin Experiment 22 1 ) .mil 1,; nu i ( neusletiei l-:.i/ilnr, an 8-page junior-high-selnm! How Does the \\'<iii-i F/<>/i in tin' l>,r/> Si</ith Mini/tie? educational publu :iin.n ) IN axailable for a sj.'i in In- Single Nelson Hogg I By ilples lit Drvr/HI/.v rust M 1)11 pills S| Illl shipping Outside \iirth America, the annual fee fur fii-fniiin, uK is S:;ii. su inagaz Wave-Induced Recirculations 26 for single copies. To receive the publications, iili'ascfall (loll Abyssal free) 1-M! s^.Vnni.l m HIate: WHOI Oceanus Package Snrvice Turnini'i This Wti/i and That Way P.O. Box NY 1:^17 Center, Wlii. Syracuse, By Michael A. Spall riirrksslinulil hcilraui a I'S hank in US dollars and mailr p,i\ahlr I" \\uinls Hole Oceaiioguplnc Institution. When .sending rhange of address, please inrludr mailing label ( 'la mis lor missing numbers from ihe I'S will be honored within Ihree months Ol publir'.il ovei -IMS, fl\e innntlis I'eriin.ssioii lo phoidciipv for mlrriial or personal use or tin- internal in use is In <>,,'uiiu\ personal of specific clients granted Editor: Vicky Cullen Designer: Jim Canavan Illi' . I In hlil. and othel llsns M-Hl,li'lril Hltll I lie '"pM'mlll Woods Hole Institution I'lralanrr Cfiiln (('('(' I, prn\ idcd that tile base fee nf S^ p,-i rMp\ Oceanographic ul I be arlicle is to CCC, 21 St i rcl, Salem, paid directly Congress Robert B. Gagosian, Director Guy W. Nichols, Chairman of the Board of Trustees M \ iilii^n Special requests should be addressed to Ckwiv//s James M. President of the Charles A. Dana, III, President of the Associates - Clark, Corporation ISSN 0029 3182 !$2.00* n.iGSTR l^s :!72 IHi7 Printed in SAor in \'iU-d paper Woods Hole Oceanographic Institution is an Equal Employment Opportunity and Affirmative Action Employer Athanasius Kircher's seventeenth The Atlantic Ocean century view of Atlantic Ocean circulation. Progress in Describing and Interpreting Its Circulation was the first physical oceanographer, world oceans' vast subtropical gyres. However, the the first to observe and ponder the cause ocean circulation was deduced from extremely sparse of ocean movements? The answer is lost data (nonexistent data in many regions). The voids in an Whoin history, of course, but the first writings were filled with considerable imagination, on the subject date to early Greek civilization. By mid imagination almost completely unconstrained by seventeenth century, expanding exploration of the New physical principals, as physicists had not yet focused on World had yielded enough geographic information to the ocean. For example, Kircher was unaware of the allow the Jesuit priest Athanasius Kircher to construct physical impossibility of two currents, like those a chart of the world as well as detailed renditions of diagrammed east of Brazil, passing through one smaller regions, such as the Atlantic sector from his another, and he was particularly fond of the notion that hand on this page. Much on this chart is recognizable subterranean passages linked maelstroms and currents, today, both in regard to principal land masses and dispersing their entrances all over the world's oceans. aspects of surface currents. The classic era of physical oceanography began These charts include the first interpretations of the about 200 years later with recognition of the central OCEANUS on role Earth's rotation plays in the We initially planned this collection of reports to focus on Atlantic circulation. physics of ocean motion and the current research deep of we ended with is an fielding of expeditions for the The diversity topics up of of the basic of explicit purpose of exploring ocean indication two aspects nonlinearity circulation. In a 1954 pamplet physical oceanography. First is the high degree of entitled "Why do our ideas about the linkage among physical phenomena: As some particu- ocean circulation have such a lar phemenon is examined, its physics often turns out linked to that of other peculiarly dream like quality," Henry to be directly phenomena. Stommel described this classic era of Second is the significant linkage among the scientists ocean is nonlinear, it is physical oceanography : themselves: Because physics a 1 a cruise, or to be a specialist using narrowly "( ) grand expedition, nearly impossible on a defined brings back many hydrographic defined technique or working narrowly but stations' worth of data; topic. We don't have to be experts in everything, need a of a broad (2) extensive plots, graphs, and we do good understanding spectrum Henry Stammel, Atlantis IL 1963 tabulations of the data are made and of phenomena that modify the physics of the ones we published for the benefit of future want to understand. has a generations; The WHOI Physical Oceanography Department with 6 (3) certain of the more striking 32-member scientific staff working postdoctoral and 34 features of the data plots are noted; associates, a 25-member technical staff, are students on Ph.D.s, all ably supported (4 ) some plausible hypotheses graduate working oceano- advanced to explain them. by 36 assistants. The staff works on physical This procedure usually exhausted graphic problems throughout the world's oceans, from millimeters to the energy of those involved, and spanning the full range of scales almost always the funds, and the megameters, and utilizing a wide range of techniques to study usually stopped at this stage." from intensive field-measurement programs equally However, the real focus of intensive theoretical and numerical modeling studies. Stommel's pamphlet was a call to the It is the largest concentration of physical oceanogra- of these scientists have research community for a fifth step: phers in the world. Seven of their indi- "All of these steps are absolutely contributed reports on one each many John Erika Dan, 1962 Swallow, a of how two necessary, of course; otherwise we vidual projects. They include study Kircher's would know nothing at all about the currents cross not through each other, as in other. deals ocean as it really is. But for the full drawing, but one beneath the One report development of the science there with the very real complexity of the currents east of the actual of the must be one additional step: Brazil, and the rest with "plumbing" Kircher's subterranean (5) the plausible hypotheses must deep circulation, not passages, of circulation be tested by specially designed but instead an intricate system abyssal observations. In this way theories pathways by which waters sink from discrete source the Atlantic Ocean. can be rejected or accepted, or may regions and move through Michael S. be modified to become acceptable." McCartney Senior Scientist Shortly thereafter Stommel provided a prototype for this modern Physical Oceanography Department era of physical oceanography by Editor's note: There are references in this volume to hypothesizing on theoretical grounds many the work of Stommel, a oceanographer the nature of the basic structure of Henry physical Val Worth ingtoii, Atlantis, 1948 extraordinaire, who died in January 1992 at 71, a loss deeply the abyssal circulation. The felt by his colleagues both at WHOI and throughout the world. validated the hypothesis was almost immediately by in A special issue oWceanus entitled A Tribi/tr H, ///// direct measurement of John Swallow (the program Sinniiiii'l was published by the Institution in 1992. The inside recipient early in 1994 of WHOl's first Henry Stommel back cover of this issue features the awarding of the first Medal in Oceanography) and Val Worthington (WHOI medal in his name. Physical Oceanography Department Chairman from 1974tol981), It is now about 37 years since Stommel published his pamphlet, and we can happily report much progress toward fulfilling his model for modern physical occanographic research. We still feel very much like explorers when we cany out our measurement programs, but we conduct and interpret them within a framework of increasingly sophisticated physical understanding. Atmospheric Pressure Oceanic Dynamic Height 70 60= 50 Note the similarity of these imagined circulation fieldsfor the atmosphere and ocean. Atmospheric pressure contours show a low over Canada and a high over southeastern United States. Arrows indicate direction offlow deducedfrom the geostrophic relation (that between horizontal pressure variations and horizontal currents), with higher speeds where the contours are closer together.