DOCSLIB.ORG

Hydrography and Circulation of the Bay of Bengal During Withdrawal Phase: of the Southwest Monsoon

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Hydrography and Circulation of the Bay of Bengal During Withdrawal Phase: of the Southwest Monsoon OCEANOLOGICA ACTA ” VOL. 22 - N” 5 Hydrography and Circulation of the Bay of Bengal during withdrawal phase: of the southwest Monsoon Y.V.B. SARMA, E.P. RAMA RAO, P.K. SAJI, V.V.S.S. SARMA National Institute of Oceanography, Dona Paula, Goa 403 004, India (Received 4 June 1998, revised 23 March 1999, accepted 6 May 1999) Abstract - Hydrographic data were collected from 3 to 10 September 1996 along two transects; one at 18” N and the other at 90” E. The data w’ere used to examine the thermohaline, circulation and chemical properties of the Bay of Bengal during the withdrawal phase of the southwest monsoon. The surface salinity exhibited wide spatial variability with values as low as 25.78 at 18” N / 87” E and as high as 34.79 at 8” N / 90” E. Two high salinity cells (S > 35.2 ) were noticed around 100 m depth along the 90” E transect. The wide scatter in T-S values between 100 and 200 m depth was attributed to the pres- ence of the Arabian ;SeaHigh Salinity (ASHS) water mass. Though the warm and low salinity conditions at the sea surface were conducive to a rise in the sea surface topography at 18” N I 87” E, the dynamic height showed a reduction of 0.2 dyn.m. This fall was attributed to thermocline upwelling at this location. The geostrophic currents showed alternating flows across both the transects. Relatively stronger and mutually opposite currents were noticed around 25 m depth across the 18” N transect with velocity slightly in excess of 30 cm s-l. Similar high velocity (> 40 cm s-l) pockets were also noticed to extend up to 30 m depths in the southern region of the 90” E transect. However, the currents below 250 m were weak and in general < 5 cm SK’.The net geostrophic volume transports were found to be of the order of 1.5 x lo6 m3 s-l towards the north and of 6 x 1O6 m3 SK’ towards west across the 18” N and 90” E transects respectively. The surface cir- culation-patterns were also investigated using the trajectories of drifting buoys deployed in the eastern Indian Ocean around the same observation period. Poleward movement of the drifting buoy with the arrival of the Indian Monsoon Cur- rent (IMC) at about 12” N along the eastern rim of the Bay of Bengal has been noticed to occur around the beginning of October. The presence of an eddy off the southeast coast of India and the IMC along the southern periphery of the Bay of Bengal were also evident in the drifting buoy data. 0 1999 Ifremer / CNRS / IRD / editions scientifiques et medicales Elsevier SAS hydrography / watermass I circulation I Monsoon I Bay of Bengal RCsumC - Hydrologie et circulation dans le golfe du Bengale B la renverse de la mousson du sud-ouest. La circulation thermohaline et les proprietes chimiques du golfe du Bengale sont CtudiCes pendant la phase de renversement de la mous- son du sud-ouest ; les donnees hydrologiques ont Cte collect&es du 3 au 10 septembre 1996 sur deux radiales, l’une a 18” N, l’autre suivant 90” E. La salinite de surface prtsente une grande variabilite spatiale, de 25,78 (par 18” N / 87” E) jusqu’a 34,79 (par 8’” N / 90” E), avec deux maxima (plus de 35,2) vers 100 m de profondeur sur la radiale 90” E. La forte dispersion des temperatures et des salinites, observte entre 100 et 200 m de profondeur, est attribuee a l’eau t&s salee en provenance de lamer d’ Arabie (ASHS). Bien que les eaux superlicielles chaudes et peu salees Cl&vent la topographie de la surface par 18” N / 87” E, la hauteur dynamique presente une baisse de 0,2 m dyn, attribuee ici a la remontee de la ther- mocline. Les flux geostrophiques sont altemes a travers les deux radiales. Des courants relativement plus forts (dtpassant 30 cm s-l) et opposCs sont observes vers 25 m de profondeur a travers la radiale 118”N. Des poches similaires de fort courant (plus de 40 cm s-l) depassent 30 m de profondeur dans la partie sud de la radiale 90” E. Cependant, au-dessous de 250 m de profondeur, les courants sont faibles (moins de 5 cm s-l). Les flux geostrophiques nets sont respectivement de l’ordre de 1,5 x lo6 m3 s-l vers le nord et 6 x lo6 m3 s-l vers l’ouest a travers les radiales 18” N et 90” E. Les schemas de la Oceanologica Acta (1999) 22, 5, 453-471 453 0 1999 lfremer I CNRS I IRD / Editions scientifiques et medicales Elsevier SAS. Tous droits rbservbs circulation superficielle sont &ablis B partir des trajectoires de boukes dCrivantes dCployCes dans l’est de l’ocCan Jndien pendant la m$me p&ode. Le mouvement est dirigC vers le p6le au dCbut du mois d’octobre, B 1’arrivCe du Courant Yndien de Mousson (IMC) le long du bord oriental du golfe du Bengale, vers 12” N. La dCrive des bouCes met en evidence Paprb- sence d’un tourbillon au large de la c&e sud-est de 1’Inde et le Courant Indien de Mousson 3 la p&iphCrie du golfe du Ben- gale. 0 1999 Ifremer / CNRS / IRD / hditions scientifiques et mtdicales Elsevier SAS hydrologie / masse d’eau i circulation I mousson J golfe du Bengale 1. INTRODUCTION and September and winter monsoon (known as northeast monsoon) during November, December, January and The northern Indian Ocean as a whole is characterized by February [26]. The Bay of Bengal forms the northeastern the reversing monsoons; summer monsoon (also known part of the Indian Ocean and is characterized by complex locally as southwest monsoon) during June, July, August current systems that vary in strength and location both Figure 1. Area of study along with CTD iocations (prepared using GMT software). HYDROGRAPHY AND CIRCULATION IN THE BAY OF BENGAL seasonally and inter-annually [5, 8, 13, 21, 25, 281. It is a distribution of the Bay of Bengal [ 181. The flow pattern semi-enclosed water body extending from 6” N to 24” N becomes disorganised and breaks into a multitude of and from 80” E to 92” E. The continental shelf along the mesoscale gyres in the Bay of Bengal during the south- east coast of India is very narrow in the south and gradu- west monsoon season [4, 7, 121. During this season the ally widens towards north with an average width of about Bay of Bengal receives excessive precipitation and fresh- 40 km. The coastline: itself has interesting geomorpholog- water runoff from several major and minor rivers all ical features such as, a northeast-oriented coastline from along the east coast of India. The effect of these factors the southern end of the peninsula to 10” N which on the distribution of physical and chemical properties abruptly, turns to east-west and then orients in rather a and the circulation of the Bay is expected to be reflected north-south direction from 10” N to 13.5” N. Beyond it, by September when the withdrawal of the southwest rather abruptly, the coa.stline orientation changes to monsoon system begins from this region. The hydro- southwest-northeast direction. This feature presumably graphic observations along 90” E were planned to com- plays a critical role in the circulation along the east coast plement the WOCE hydrographic data along section I-5 of India as was evident from the selective upwelling in the eastern Indian Ocean further north. zones, northward coastal current and variable offshore The weather conditions during the cruise period were Ekman transport along the northwestern Bay during the characterized by easterlies of about 5 m s-‘north of 13” N southwest monsoon period [23]. The summer monsoon is and strong southwesterlies of about 10 m s-’ with speeds the single largest event that brings about large scale occasionally exceeding 15 m s-l in the south cfigure 2) changes in circulation [3, 16, 17, 19, 241 and heat content which is the characteristic feature of the southwest Figure 2. Distribution of wind (m s-l) vector along the cruise track. 455 V.V.B. SARMA et al. monsoon trough. In general, weather was cIear in the with 15 L Niskin samplers mounted on the CTD rosette northern Bay but cloudy towards south of 13” N. The and analysed using a calibrated salinometer (Guildline, rainfall recorded around 1 lo N / 90” E over the sea region Autosai model: 84OOA). The salinity values obtained on September 7 was as high as 57 mm. The wind patterns both by CTD and tbe Autosal were regressed to verify the indicate the beginning of southwest monsoon withdrawal drift in the CTD salinity measurements. We found that from the northern Bay of Bengal. both CTD and the Autosal salinity values correlated In this article, we present an analysis of the results of excellently (Y - 0.998) with a constant salinity difference (0.03) between these values with the CTD salinity values hydrographic observations and discuss the water masses marginally on the lower side. The geostrophic currents and circulation patterns along with associated volume and the volume transport estimates were computed rela- fransport structure in the Bay during the withdrawal phase of the southwest monsoon. tive to 1000 m depth. The heat content was computed with respect to a 13 “C isotherm which is considered as the base of the thermocline. In this process the heat con- tent changes due to vertical motions caused by diver- 2.
Load more

Recommended publications
  • Global Ocean Observing System
    The Global Ocean Observing System Dr Vladimir Ryabinin Executive Secretary of Intergovernmental Oceanographic Commission; Assistant Director-General, UNESCO ICP-18 UN, New York 17.05.2017 IOC: Global Ocean Observing System IOC: Tsunami Warning System 1965- Pacific 2005- Indian Ocean Caribbean NE Atlantic & Mediterranean - Ocean Obs’99 - initiated global ocean climate observations - Ocean Obs’09 - initiated Framework for Ocean Observing - Ocean Obs’19 will focus on strengthening the linkages between the observing systems and the societal benefit areas where the knowledge of the oceanic environment is particularly essential (Hawaii, USA, September 2019) post-OO’09 Working Group A value chain Innovation, observations, data management, forecasts / science & assessment, societal benefit Adapted from G7 Think Piece on Ocean Observations GOOS Program Structure Ocean observations for societal benefit Climate, services, ocean health IOC: Global Ocean Observing System Driven by requirements, negotiated with feasibility Essential Ocean Variables Towards sustained system: requirements, observations, data management Readiness Mature Pilot Attributes: Products of the global ocean observing system are well understood, documented, consistently available, and Concept of societal benefit. Attributes: Planning, negotiating, testing, and approval within appropriate local, regional, global arenas. Attributes: Peer review of ideas and studies at science, engineering, and data management community level. EOVs and readiness level CONCEPT PILOT MATURE *also ECV
    [Show full text]
  • Ocean Circulation and Climate: an Overview
    ocean-climate.org Bertrand Delorme Ocean Circulation and Yassir Eddebbar and Climate: an Overview Ocean circulation plays a central role in regulating climate and supporting marine life by transporting heat, carbon, oxygen, and nutrients throughout the world’s ocean. As human-emitted greenhouse gases continue to accumulate in the atmosphere, the Meridional Overturning Circulation (MOC) plays an increasingly important role in sequestering anthropogenic heat and carbon into the deep ocean, thus modulating the course of climate change. Anthropogenic warming, in turn, can influence global ocean circulation through enhancing ocean stratification by warming and freshening the high latitude upper oceans, rendering it an integral part in understanding and predicting climate over the 21st century. The interactions between the MOC and climate are poorly understood and underscore the need for enhanced observations, improved process understanding, and proper model representation of ocean circulation on several spatial and temporal scales. The ocean is in perpetual motion. Through its DRIVING MECHANISMS transport of heat, carbon, plankton, nutrients, and oxygen around the world, ocean circulation regulates Global ocean circulation can be divided into global climate and maintains primary productivity and two major components: i) the fast, wind-driven, marine ecosystems, with widespread implications upper ocean circulation, and ii) the slow, deep for global fisheries, tourism, and the shipping ocean circulation. These two components act industry. Surface and subsurface currents, upwelling, simultaneously to drive the MOC, the movement of downwelling, surface and internal waves, mixing, seawater across basins and depths. eddies, convection, and several other forms of motion act jointly to shape the observed circulation As the name suggests, the wind-driven circulation is of the world’s ocean.
    [Show full text]
  • Mid-Depth Calcareous Contourites in the Latest Cretaceous of Caravaca (Subbetic Zone, SE Spain)
    Mid-depth calcareous contourites in the latest Cretaceous of Caravaca (Subbetic Zone, SE Spain). Origin and palaeohydrological significance Javier Martin-Chivelet*, Maria Antonia Fregenal-Martinez, Beatriz Chac6n Departamento de 8stratigrajia. institute de Geologia Economica (CSiC-UCM). Facultad de Ciencias Geologicas. Universidad Complutense. 28040 Madrid, Spain Abstract Deep marine carbonates of Late Campanian to Early Maastrichtian age that crop out in the Subbetic Zone near Caravaca (SE Spain) contain a thick succession of dm-scale levels of calcareous contourites, alternating with fine-grained pelagitesl hemipelagites. These contourites, characterised by an abundance and variety of traction structures, internal erosive surfaces and inverse and nOlmal grading at various scales, were interpreted as having been deposited under the influence of relatively deep ocean CUlTents. Based on these contourites, a new facies model is proposed. The subsurface currents that generated the contourites of Caravaca were probably related to the broad circumglobal, equatorial current system, the strongest oceanic feature of Cretaceous times. These deposits were formed in the mid-depth (200-600 m), hemipelagic environments at the ancient southern margin of Iberia. This palaeogeographic setting was susceptible to the effects of these currents because of its position close to the narrowest oceanic passage, through which the broad equatorial cun'ent system flowed in the westemmost area of the Tethys Seaway. Regional uplift, related to the onset of convergence between Iberia and Africa, probably favoured the generation of the contourites during the Late Campanian to the Early Maastrichtian. Keyword\': Contourites; Palaeoceanography; Late Cretaceous; Caravaca; Betics; SE Spain 1. Introduction aI., 1996; Stow and Faugeres, 1993, 1998; Stow and Mayall, 2000a; Shanmugam, 2000).
    [Show full text]
  • Nearcoastal Circulation in the Northern Humboldt Current System From
    JOURNAL OF GEOPHYSICAL RESEARCH: OCEANS, VOL. 118, 1–16, doi:10.1002/jgrc.20328, 2013 Near-coastal circulation in the Northern Humboldt Current System from shipboard ADCP data Alexis Chaigneau,1,2 Noel Dominguez,3 Gerard Eldin,1,2 Luis Vasquez,3 Roberto Flores,3 Carmen Grados,3 and Vincent Echevin1,4 Received 20 December 2012; revised 25 July 2013; accepted 25 July 2013. [1] The near-coastal circulation of the Northern Humboldt Current System is described analyzing 8700 velocity profiles acquired by a shipboard acoustic Doppler current profiler (SADCP) during 21 surveys realized between 2008 and 2012 along the Peruvian coast. This data set permits observation of (i) part of the Peru Coastal Current and the Peru Oceanic Current that flow equatorward in near-surface layers close to the coast and farther than 150 km from the coast, respectively; (ii) the Peru-Chile Undercurrent (PCUC) flowing poleward in subsurface layers along the outer continental shelf and inner slope; (iii) the near-surfacing Equatorial Undercurrent renamed as Ecuador-Peru Coastal Current that feeds the PCUC; and (iv) a deep equatorward current, referred to as the Chile-Peru Deep Coastal Current, flowing below the PCUC. A focus in the PCUC core layer shows that this current exhibits typical velocities of 5–10 cm sÀ1. The PCUC deepens with an increasing thickness poleward, consistent with the alongshore conservation of potential vorticity. The PCUC mass transport increases from 1.8 Sv at 5S to a maximum value of 5.2 Sv at 15S, partly explained by the Sverdrup balance. The PCUC experiences relatively weak seasonal variability and the confluence of eddy-like structures and coastal currents strongly complicates the circulation.
    [Show full text]
  • The Response of the Peruvian Upwelling Ecosystem to Centennial
    The response of the Peruvian Upwelling Ecosystem to centennial-scale global change during the last two millennia Renato Salvatteci, Dimitri Gutiérrez, David Field, Abdelfettah Sifeddine, Luc Ortlieb, Ioanna Bouloubassi, Mohammed Boussafir, Hugues Boucher, Féthiyé Cetin To cite this version: Renato Salvatteci, Dimitri Gutiérrez, David Field, Abdelfettah Sifeddine, Luc Ortlieb, et al.. The re- sponse of the Peruvian Upwelling Ecosystem to centennial-scale global change during the last two millennia. Climate of the Past, European Geosciences Union (EGU), 2014, 10 (2), pp.715-731. 10.5194/cp-10-715-2014. hal-01139602 HAL Id: hal-01139602 https://hal.archives-ouvertes.fr/hal-01139602 Submitted on 9 Dec 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Distributed under a Creative Commons Attribution| 4.0 International License Clim. Past, 10, 715–731, 2014 Open Access www.clim-past.net/10/715/2014/ Climate doi:10.5194/cp-10-715-2014 © Author(s) 2014. CC Attribution 3.0 License. of the Past The response of the Peruvian Upwelling Ecosystem to centennial-scale global change during the last two millennia R. Salvatteci1,2,*, D. Gutiérrez2,3, D. Field4, A.
    [Show full text]
  • Climate Resilience Technical Fact Sheet: Contaminated Sediment Sites
    Office of Superfund Remediation and Technology Innovation EPA 542-F-19-003 October 2019 Update Climate Resilience Technical Fact Sheet: Contaminated Sediment Sites In June 2014, the U.S. Environmental Protection Agency (EPA) released the U.S. Environmental Protection Agency Climate Change Adaptation Plan.1 The plan examines how EPA programs may be vulnerable to a changing climate and how the Agency can accordingly adapt in order to continue meeting its mission of protecting human health and the environment. Under the Superfund Program, existing processes for planning and implementing site remedies provide a robust structure that allows consideration of climate change effects. Examination of the associated implications on site remedies is most effective through use of a place-based strategy due to wide variations in the hydrogeologic characteristics of sites, the nature of remediation systems operating at contaminated sites, and local or regional climate and weather regimes. Measures to increase resilience to a changing climate may be integrated throughout the Superfund process, including feasibility studies, remedy designs and remedy performance reviews. As one in a series, this fact sheet addresses Cleanup at many sites involves remediating contaminated aquatic the climate resilience of Superfund remedies sediment – the clay, silt, sand and organic matter at the bottom of or at sites with contaminated sediment. It is along the banks of rivers, lakes, estuaries, harbors or other surface water intended to serve as a site-specific planning bodies. Common sediment remediation technologies are dredging or tool by (1) describing an approach to excavation with off-site treatment or disposal, capping to isolate assessing potential vulnerability of a sediment remedy, (2) providing examples of contaminated sediment, and application of amendments that bind or 2 measures that may increase resilience of a destroy the contaminants.
    [Show full text]
  • Mediterranean Subsurface Circulation Estimated from Argo Data in 2003–2009
    Ocean Sci. Discuss., 6, 2717–2753, 2009 Ocean Science www.ocean-sci-discuss.net/6/2717/2009/ Discussions © Author(s) 2009. This work is distributed under the Creative Commons Attribution 3.0 License. This discussion paper is/has been under review for the journal Ocean Science (OS). Please refer to the corresponding final paper in OS if available. Mediterranean subsurface circulation estimated from Argo data in 2003–2009 M. Menna and P. M. Poulain Istituto Nazionale di Oceanografia e di Geofisica Sperimentale – OGS, Sgonico (TS), Italy Received: 20 October 2009 – Accepted: 5 November 2009 – Published: 18 November 2009 Correspondence to: M. Menna ([email protected]) Published by Copernicus Publications on behalf of the European Geosciences Union. 2717 Abstract Data from 38 Argo profiling floats are used to describe the subsurface Mediterranean currents for the period 2003–2009. These floats were programmed to execute 5-day cycles, to drift at a neutral parking depth of 350 m and measure temperature and salin- 5 ity profiles from either 700 or 2000 m up to the surface. At the end of each cycle the floats remained at the sea surface for about 6 h, enough time to be localised and trans- mit the data to the Argos satellite system. The Argos positions were used to determine the float surface and subsurface displacements. At the surface, the float motion was approximated by a linear displacement and inertial motion. Subsurface velocities esti- 10 mates were used to investigate the Mediterranean circulation at 350 m, to compute the pseudo-Eulerian statistics and to study the influence of bathymetry on the subsurface currents.
    [Show full text]
  • Reference List Pages on Which References Are Cited Appear in Angle Brackets
    Reference List Pages on which references are cited appear in angle brackets. Every reference to original material not in English for which the editors knew of an English trans- lation is followed by a reference to the English trans- lation; references to untranslated Russian material in- clude translations of the Russian titles immediately following the Russian titles. Aanderaa, I. R., 1964. A recording and telemetering instru- ment. Fixed Buoy Project, NATO Subcommittee on Ocean- ographic Research Technical Report No. 16, Bergen, 46 pp., 20 figures. (405) Accad, Y., and C. L. Pekeris, 1978. Solution of the tidal equa- tions for the M2 and S2 tides in the world oceans from a knowledge of the tidal potential alone. Philosophical Trans- actions of the Royal Society of London A 290:235-266. (297, 322, 323, 329, 330) Adamec, D., and J. J. O'Brien, 1978. The seasonal upwelling in the Gulf of Guinea due to remote forcing. Journal of Phys- ical Oceanography 8:1050-1060. (193) Adams, J. K., and V. T. Buchwald, 1969. The generation of continental shelf waves. Journal of Fluid Mechanics 35: 815-816. (358) African Pilot, 1967. Hydrographer of the Navy, London, 12th ed., 3, 529 pp. (185) Agee, E. M., and K. E. Dowell, 1974. Observational studies of mesoscale cellular convection. Journal of Applied Meteorol- ogy 13:46-53. (500) Agnew D., and W. Farrell, 1978. Self-consistent equilibrium ocean tides. Geophysical Journal of the Royal Astronomical Society 55:171-181. (339) Agnew, R., 1961. Estuarine currents and tidal streams. In Proceedings of the Seventh Conference on Coastal Engineer- ing, The Hague, 1960, 2, pp.
    [Show full text]
  • Ocean Currents and Wind Patterns) Affects Humans
    Pacific Marine National Monuments Pacific Remote Islands Marine National Monument – Humans and the Ocean Grade Level 7-12 Activity Summary This lesson seeks to show students how the islands of the Pacific Remote Islands Marine National Monument are integral to interactions between Timeframe the human and the natural environment. The environment provides us with resources and these resources needs have changed over time. This 2 45-minute classes need for resources is a major reason why islands of the PRIMNM are part of the United States. The historical resource use and the transportation associated with it are used to show how the natural world Key Words (i.e. ocean currents and wind patterns) affects humans. Students use the Latitude introduction of how sailors traveled to the islands to investigate global Longitude wind and currents, and then through a demonstration, understand how Ocean Circulation global currents can have local effects through processes like upwelling. Upwelling Learning Objectives Gain a basic understanding of wind patterns in the central Pacific and how that might affect travel decisions Understand how wind and temperature differences drive ocean currents Draw connections between how the physical processes of the ocean can affect biological systems, including humans Background Information Many of the islands of the Pacific Remote Islands Marine National Monument were visited by ancient Polynesian voyageurs, but none of the islands appear to have sustained long If you need assistance with this U.S. Department of Commerce | National Oceanic and Atmospheric Administration | National Marine Fisheries Service document, please contact NOAA Fisheries at (808) 725-5000. Marine National Monument Program | Pacific Remote Islands term colonization due to lack of available resources.
    [Show full text]
  • Arxiv:1906.08066V1 [Physics.Ao-Ph] 19 Jun 2019 Made for the Prediction of the Different Ocean Processes Including the Ocean Currents and Circulations
    Predicting the Ocean Currents using Deep Learning Cihan Bayındır1, ∗ 1Associate Professor, Engineering Faculty, Istanbul_ Technical University, 34469 Maslak, Istanbul,_ Turkey. Adjunct Professor, Engineering Faculty, Bo˘gazi¸ciUniversity, 34342 Bebek, Istanbul,_ Turkey. International Collaboration Board Member, CERN, CH-1211 Geneva 23, Switzerland. In this paper, we analyze the predictability of the ocean currents using deep learning. More specifically, we apply the Long Short Term Memory (LSTM) deep learning network to a data set collected by the National Oceanic and Atmospheric Administration (NOAA) in Massachusetts Bay between November 2002-February 2003. We show that the current speed in two horizontal directions, namely u and v, can be predicted using the LSTM. We discuss the effect of training data set on the prediction error and on the spectral properties of predictions. Depending on the temporal or the spatial resolution of the data, the prediction times and distances can vary, and in some cases, they can be very beneficial for the prediction of the ocean current parameters. Our results can find many important applications including but are not limited to predicting the tidal energy variation, controlling the current induced vibrations of marine structures and estimation of the wave blocking point by the chaotic oceanic current and circulation. PACS numbers: I. INTRODUCTION Ocean currents and circulations are one of the very important phenomena observed in the ocean hydrodynamics and they have attracted a lot of attention throughout the historical development of ocean science [1, 2]. These currents and circulations can be generated by many different mechanisms. These mechanisms include but are not limited to winds [3, 4], tides [5], waves [6], changes in underwater topography [7] and buoyancy fluxes [6, 8{10].
    [Show full text]
  • Ocean Currents
    Data Detectives: The Ocean Environment Unit 2 – Ocean Currents Unit 2 Ocean Currents In this unit, you will • Investigate the forces that drive surface currents in the world’s oceans. • Identify major ocean gyres and their physical properties — temperature, speed, and direction. • Correlate current direction and speed with global winds. • Examine ocean salinity and temperature patterns and their relationship to deep-water density currents. NASA NASA SEASAT satellite image showing average surface wind speed (colors) and direction (arrows) over the Pacifi c Ocean. 43 Data Detectives: The Ocean Environment Unit 2 – Ocean Currents 44 Data Detectives: The Ocean Environment Unit 2 – Ocean Currents Warm-up 2.1 A puzzle at 70° N Common sense tells us that temperatures increase closer to Earth’s equator and decrease closer to the poles. If this is true, the pictures below present a strange puzzle (Figure 1). Th ey show two coastal areas at about the same latitude but on opposite sides of the North Atlantic Ocean. Nansen Fjörd, on the left , is on Greenland’s eastern coast, while Tromsø, right, lies on the northwestern coast of Norway. Th ese places are at roughly the same latitude, but their climates could hardly be more diff erent. Arctic Ocean Greenland Norway Atlantic Ocean ©2005 L. Micaela Smith. Used with permission. ©2005 Mari Karlstad, Tromsø Univ. Museum. Used with permission. Figure 1. A summer day at Nansen Fjörd, on the eastern coast of Greenland (left) and in Tromsø, on the northwestern coast of Norway (right). Both locations are near latitude 70° N. 1. Why do you think the temperatures at the same latitude in Greenland and Norway are so diff erent? A puzzle at 70° N 45 Data Detectives: The Ocean Environment Unit 2 – Ocean Currents Since the fi rst seafarers began traveling the world’s oceans thousands of years ago, navigators have known about currents — “rivers in the ocean” — that fl ow over long distances along predictable paths.
    [Show full text]
  • Effects of Penetrative Radiation on the Upper Tropical Ocean Circulation
    470 JOURNAL OF CLIMATE VOLUME 15 Effects of Penetrative Radiation on the Upper Tropical Ocean Circulation RAGHU MURTUGUDDE AND JAMES BEAUCHAMP Earth System Science Interdisciplinary Center, University of Maryland, College Park, College Park, Maryland CHARLES R. MCCLAIN NASA Goddard Space Flight Center, SeaWiFS Project Of®ce, Greenbelt, Maryland MARLON LEWIS Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada ANTONIO J. BUSALACCHI Earth System Science Interdisciplinary Center, University of Maryland, College Park, College Park, Maryland (Manuscript received 23 February 2001, in ®nal form 3 August 2001) ABSTRACT The effects of penetrative radiation on the upper tropical ocean circulation have been investigated with an ocean general circulation model (OGCM) with attenuation depths derived from remotely sensed ocean color data. The OGCM is a reduced gravity, primitive equation, sigma coordinate model coupled to an advective atmospheric mixed layer model. These simulations use a single exponential pro®le for radiation attenuation in the water column, which is quite accurate for OGCMs with fairly coarse vertical resolution. The control runs use an attenuation depth of 17 m while the simulations use spatially variable attenuation depths. When a variable depth oceanic mixed layer is explicitly represented with interactive surface heat ¯uxes, the results can be counterintuitive. In the eastern equatorial Paci®c, a tropical ocean region with one of the strongest biological activity, the realistic attenuation depths result in increased loss of radiation to the subsurface, but result in increased sea surface temperatures (SSTs) compared to the control run. Enhanced subsurface heating leads to weaker strati®cation, deeper mixed layers, reduced surface divergence, and hence less upwelling and entrainment.
    [Show full text]