Indian Ocean - Upwelling, Climate, Marine Life

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During the northeast monsoon, strong upwelling occurs along the western coast of India. Midocean upwelling takes place at that time at 5° S, where the North Equatorial Current and the Equatorial Countercurrent run alongside each other in opposite directions. 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During the southwest monsoon, upwelling occurs off the Somali and Arabian coasts and south of Java. It is most intense between 5° and 11° N, with replacement of warmer surface water by water of about 57 °F (14 °C). During the northeast monsoon, strong upwelling occurs along the western coast of India. Midocean upwelling takes place at that time at 5° S, where the North Equatorial Current and the Equatorial Countercurrent run alongside each other in opposite directions. A zonal asymmetry is noted in the surface"/> <meta property="og:type" content="ARTICLE"/> <meta property="og:title" content="Indian Ocean - Upwelling, Climate, Marine Life | Britannica"/> <meta property="og:description" content="Indian Ocean - Upwelling, Climate, Marine Life: Upwelling is a seasonal phenomenon in the Indian Ocean because of the monsoon regime. During the southwest monsoon, upwelling occurs off the Somali and Arabian coasts and south of Java. It is most intense between 5° and 11° N, with replacement of warmer surface water by water of about 57 °F (14 °C). During the northeast monsoon, strong upwelling occurs along the western coast of India. Midocean upwelling takes place at that time at 5° S, where the North Equatorial Current and the Equatorial Countercurrent run alongside each other in opposite directions. 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class="col-auto"> <div class="topic-left-rail md-article-drawer position-relative d-flex border-right-sm border-left-sm open"> <div class="drawer d-flex flex-column open"> <div class="left-rail-section-content"> <div class="topic-left-rail-header text-truncate bg-gray-50 position-relative text-right d-flex align-items-center"> <div class="tlr-title px-20 py-15 text-left"> <em class="material-icons text-gray-400 d-lg-none" data-icon="toc"></em> <a class="font-serif font-weight-bold text-black link-blue" href="https://www.britannica.com/place/Indian-Ocean">Indian Ocean</a> </div> <button aria-label="Close" class="js-sections-close-button btn-link btn-sm btn d-lg-none position-absolute top-0 p-10 right-0" > <em class="material-icons font-26" data-icon="close"></em> </button> </div> <div class="section-content pl-10 pr-20 pl-sm-50 pr-sm-60 pl-lg-5 pr-lg-10 pt-10 pt-lg-0 bg-gray-50 clear-catfish-ad"> <div class="toc mb-20"> <div class="font-serif font-14 font-weight-bold mx-15 mb-15 mt-20"> Table of Contents </div> <ul class="list-unstyled my-0" data-level="h1"><li data-target="#ref1"><div class="pl-25"><a class="link-gray-900 w-100" href="/place/Indian-Ocean">Introduction & Top Questions</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref22755"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/place/Indian-Ocean#ref22755">Physiography and geology</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref22756"><a class="w-100 link-gray-900" href="/place/Indian-Ocean#ref22756">Origin</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref22757"><a class="w-100 link-gray-900" href="/place/Indian-Ocean#ref22757">Submarine features</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref22758"><a class="w-100 link-gray-900" href="/place/Indian-Ocean#ref22758">Oceanic ridges and fracture zones</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref22759"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Seamounts">Seamounts</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref22760"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Seamounts#ref22760">Ocean basins</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref22761"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Seamounts#ref22761">Continental rise, slope, and shelf</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref22762"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Seamounts#ref22762">Trenches</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref22763"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Bottom-deposits">Bottom deposits</a></li></ul></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref22764"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Bottom-deposits#ref22764">Surface features</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref22765"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Bottom-deposits#ref22765">Coasts</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref22766"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Bottom-deposits#ref22766">Islands</a></li></ul></li></ul></div></li><li data-target="#ref22767"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Bottom-deposits#ref22767">Climate</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref22768"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Bottom-deposits#ref22768">Monsoon zone</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref22769"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Trade-winds-zone">Trade-winds zone</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref22770"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Trade-winds-zone#ref22770">Subtropical and temperate zone</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref22771"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Trade-winds-zone#ref22771">Subantarctic and Antarctic zone</a></li></ul></div></li><li data-target="#ref22772"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Trade-winds-zone#ref22772">Hydrology</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref22773"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Trade-winds-zone#ref22773">Surface currents</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref22774"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Trade-winds-zone#ref22774">Deep (thermohaline) circulation</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref22775"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Upwelling">Upwelling</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref22776"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Upwelling#ref22776">Surface temperatures</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref22777"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Upwelling#ref22777">Surface salinity</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref22778"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Upwelling#ref22778">Ice</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref22779"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Upwelling#ref22779">Tides</a></li></ul></div></li><li data-target="#ref22780"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Economic-aspects">Economic aspects</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref22781"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Economic-aspects#ref22781">Mineral resources</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref22782"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Economic-aspects#ref22782">Biological resources</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref22783"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Economic-aspects#ref22783">Fisheries</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref22784"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Trade-and-transportation">Trade and transportation</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref332035"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Trade-and-transportation#ref332035">Tourism</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref22785"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Trade-and-transportation#ref22785">Environmental impact of human activity</a></li></ul></div></li><li data-target="#ref22786"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Study-and-exploration">Study and exploration</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref22787"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Study-and-exploration#ref22787">Early exploration</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref22788"><a class="w-100 link-gray-900" href="/place/Indian-Ocean/Study-and-exploration#ref22788">Systematic investigations</a></li></ul></div></li></ul> <a class="toc-extra-link link-gray-900" href="https://www.britannica.com/place/Indian-Ocean/additional-info">References & 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Verlaan</div> <div class="editor-description font-12 font-serif mt-5 clamp-description text-black">Oceanographer and attorney. Author of <i>South Asian Seas: A Review of the Oceanography, Resources and Environment.</i></div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link gtm-byline font-12 byline-contributor text-decoration-underline"> Philomene A. Verlaan</span>, <div class="editor-popover popover p-0"> <a class="d-block p-20 qa-editor-popup gtm-byline font-12 byline-contributor" href="/contributor/Joseph-R-Morgan/3741" > <div class="editor-title font-16 font-weight-bold">Joseph R. Morgan</div> <div class="editor-description font-12 font-serif mt-5 clamp-description text-black">Associate Professor of Geography, University of Hawaii at Manoa, Honolulu. 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They write new content and verify and edit content received from contributors.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link font-12 "> The Editors of Encyclopaedia Britannica</span></div> <div class="last-updated font-12 font-serif"> <span class="text-gray-700"> Last Updated: <time datetime="2025-02-26T00:00:00CST" >Feb 26, 2025</time> •</span> <a class="byline-edit-history" href="https://www.britannica.com/place/Indian-Ocean/additional-info#history" rel="nofollow">Article History</a> </div></div> </div> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button d-none d-sm-block js-sections-inline-button module-spacing btn d-lg-none"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <div class="d-flex d-sm-none flex-row"> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button js-sections-inline-button module-spacing"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <button class="ai-ask-button btn btn-sm border-2 btn-outline-red-400 border-red-400 module-spacing js-inline-ai-ask-button p-10 ml-5"> Ask the Chatbot </button> </div> <div class="bg-gray-50 p-15 rounded module-spacing recent-news d-flex flex-column float-false"> <div> <h2 class="font-weight-bold font-14 m-0 d-inline"> News <span class="text-gray-600">•</span> </h2> <div class="recent-news-item first-recent-news-item d-inline"> <a class="font-14 gtm-ap-news-link" href="https://www.cbsnews.com/news/mh370-malaysia-airlines-flight-missing-new-search-ocean-infinity-indian-ocean/" rel="nofollow">New search underway for MH370 in Indian Ocean 11 years after Malaysia Airlines flight disappeared</a> <span class="font-14 text-gray-600"> <span>•</span> Feb. 25, 2025, 4:51 AM ET (CBS) <button class="btn btn-link d-inline p-0 font-12 js-toggle-recent-news"> <span class="text-gray-500">...</span><span>(Show more)</span> </button> </span> </div> </div> <div class="rest-of-recent-news-items"> <div class="recent-news-item mt-5"> <a class="font-14 gtm-ap-news-link" href="https://www.straitstimes.com/asia/se-asia/new-search-for-missing-malaysian-mh370-plane-begins" rel="nofollow">New search begins for missing MH370 plane</a> <span class="font-14 text-gray-600"> <span>•</span> Feb. 24, 2025, 3:06 PM ET (Straits Times) </span> </div> <div class="recent-news-item mt-5"> <a class="font-14 gtm-ap-news-link" href="https://indianexpress.com/article/india/unilateral-changes-to-status-quo-a-concern-in-indo-pacific-eam-9839826/" rel="nofollow">Unilateral changes to status quo a concern in Indo-Pacific: EAM</a> <span class="font-14 text-gray-600"> <span>•</span> Feb. 16, 2025, 9:19 PM ET (The Indian Express) </span> </div> <div class="recent-news-item mt-5"> <a class="font-14 gtm-ap-news-link" href="https://www.thedailystar.net/news/bangladesh/diplomacy/news/dhaka-committed-boosting-indian-ocean-partnership-foreign-adviser-3825741" rel="nofollow">Dhaka committed to boosting Indian Ocean partnership: foreign adviser</a> <span class="font-14 text-gray-600"> <span>•</span> Feb. 16, 2025, 4:09 AM ET (Daily Star) </span> </div> <div class="recent-news-item mt-5"> <a class="font-14 gtm-ap-news-link" href="https://indianexpress.com/article/india/modi-trump-quad-initiatives-indian-ocean-strategic-venture-9835744/" rel="nofollow">Modi-Trump meeting: India, US announce plans for fresh Quad initiatives, launch bilateral strategic venture</a> <span class="font-14 text-gray-600"> <span>•</span> Feb. 15, 2025, 3:57 AM ET (The Indian Express) </span> </div> <button class="js-toggle-recent-news d-flex btn btn-unstyled font-14 pr-10 rounded-sm mt-10" aria-label="Toggle additional news items"> Show less <em class="material-icons" data-icon="expand_less"></em> </button> </div> </div><span class="marker before-article"></span><section data-level="1"><span class="marker before-article"></span><section data-level="2" id="ref22775"> <span class="marker PREMOD1 mod-inline"></span><p class="topic-paragraph">Upwelling is a seasonal phenomenon in the Indian Ocean because of the <a href="https://www.britannica.com/science/monsoon" class="md-crosslink autoxref " data-show-preview="true">monsoon</a> regime. During the southwest monsoon, upwelling occurs off the Somali and <a href="https://www.britannica.com/place/Arabia-peninsula-Asia" class="md-crosslink " data-show-preview="true">Arabian</a> coasts and south of <a href="https://www.britannica.com/place/Java-island-Indonesia" class="md-crosslink autoxref " data-show-preview="true">Java</a>. It is most intense between 5° and 11° N, with replacement of warmer surface <a href="https://www.britannica.com/science/water" class="md-crosslink autoxref " data-show-preview="true">water</a> by water of about 57 °F (14 °C). During the northeast monsoon, strong upwelling occurs along the western coast of <a href="https://www.britannica.com/place/India" class="md-crosslink autoxref " data-show-preview="true">India</a>. Midocean upwelling takes place at that time at 5° S, where the North Equatorial Current and the Equatorial Countercurrent run alongside each other in opposite directions.</p><span class="marker MOD1 mod-inline"></span> </section> <section data-level="2" id="ref22776"> <h2 class="h2">Surface <span id="ref925368"></span><a href="https://www.britannica.com/science/temperature" class="md-crosslink " data-show-preview="true">temperatures</a></h2> <span class="marker PREMOD2 mod-inline"></span><p class="topic-paragraph">A zonal asymmetry is noted in the surface water temperature distribution in summer north of latitude 20° S. Summer surface temperatures are higher in the eastern part of that region than in the west. In the Bay of Bengal the maximum temperature is around 82 °F (28 °C). The minimum temperature is about 72 °F (22 °C) in the area of Cape Gwardafuy (Guardafui), on the <a href="https://www.britannica.com/place/Horn-of-Africa" class="md-crosslink autoxref " data-show-preview="true">Horn of Africa</a>, and is associated with the upwelling off the African coast. South of 20° S the temperature of the surface waters decreases at a uniform rate with increasing latitude, from 72 to 75 °F (22° to 24 °C) down to near freezing, 32 °F (0 °C), at 60° S. Near the Equator, northern winter surface water temperatures in excess of 82 °F (28 °C) are <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="encountered" href="https://www.britannica.com/dictionary/encountered" data-type="EB">encountered</a> in the eastern part of the <a href="https://www.britannica.com/science/ocean" class="md-crosslink autoxref " data-show-preview="true">ocean</a>. Winter surface temperatures are about 72 to 73 °F (22 to 23 °C) in the northern portion of the Arabian Sea and 77 °F (25 °C) in the Bay of Bengal. At 20° S the temperature is about 72 to 75 °F (22 to 24 °C); at the 40th parallel, 57 to 61 °F (14 to 16 °C); and at 60° S, 30 to 32 °F (−1 to 0 °C).</p><span class="marker MOD2 mod-inline"></span> </section> <section data-level="2" id="ref22777"> <h2 class="h2">Surface <span id="ref150281"></span><a href="https://www.britannica.com/science/salinity" class="md-crosslink " data-show-preview="true">salinity</a></h2> <span class="marker PREMOD3 mod-inline"></span><p class="topic-paragraph">Overall, the salinity of Indian Ocean surface waters varies between 32 and 37 parts per thousand, with large local differences. The <span id="ref150282"></span><a href="https://www.britannica.com/place/Arabian-Sea" class="md-crosslink " data-show-preview="true">Arabian Sea</a> has a dense, high-salinity layer (37 parts per thousand) to a depth of about 400 feet (120 metres) because of high evaporation rates at subtropical temperatures with <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="moderate" href="https://www.britannica.com/dictionary/moderate" data-type="EB">moderate</a> seasonal variations. Salinity in the surface layer of the <span id="ref150283"></span><a href="https://www.britannica.com/place/Bay-of-Bengal" class="md-crosslink " data-show-preview="true">Bay of Bengal</a> is considerably lower, often less than 32 parts per thousand, because of the huge drainage of fresh water from rivers. High surface salinity (greater than 35 parts per thousand) is also found in the Southern Hemisphere subtropical zone between 25° and 35° S; while a low-salinity zone stretches along the hydrological boundary of 10° S from <a href="https://www.britannica.com/place/Indonesia" class="md-crosslink autoxref " data-show-preview="true">Indonesia</a> to <a href="https://www.britannica.com/place/Madagascar" class="md-crosslink autoxref " data-show-preview="true">Madagascar</a>. Surface water salinity at 60° S is between 33 and 34 parts per thousand.</p><span class="marker MOD3 mod-inline"></span> </section> <section data-level="2" id="ref22778"> <h2 class="h2"><span id="ref150284"></span><a href="https://www.britannica.com/science/ice" class="md-crosslink " data-show-preview="true">Ice</a></h2> <span class="marker PREMOD4 mod-inline"></span><p class="topic-paragraph"><a href="https://www.britannica.com/science/ice" class="md-crosslink " data-show-preview="true">Ice</a> is formed in the extreme south during the Antarctic winter. Between January and February the melting ice along the Antarctic coast is broken up by severe storms and, in the form of large blocks and broad floes, is carried away by wind and currents to the open ocean. In some coastal areas the tongues of ice-shelf glaciers break off to form <span id="ref150285"></span><a href="https://www.britannica.com/science/iceberg" class="md-crosslink " data-show-preview="true">icebergs</a>. West of the 90° E <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="meridian" href="https://www.britannica.com/dictionary/meridian" data-type="EB">meridian</a> the northern limit for floating ice lies close to latitude 65° S. To the east of that meridian, however, floating ice is commonly encountered to 60° S; icebergs are sometimes found as far north as 40° S.</p><span class="marker MOD4 mod-inline"></span> </section> <section data-level="2" id="ref22779"> <h2 class="h2"><span id="ref150286"></span><a href="https://www.britannica.com/science/tide" class="md-crosslink " data-show-preview="true">Tides</a></h2> <span class="marker PREMOD5 mod-inline"></span><p class="topic-paragraph">Examples of all three tidal types—<span id="ref150287"></span><a href="https://www.britannica.com/science/diurnal-motion" class="md-crosslink " data-show-preview="true">diurnal</a> (daily), <span id="ref150288"></span><a href="https://www.britannica.com/science/semidiurnal-tide" class="md-crosslink ">semidiurnal</a> (twice daily), and mixed—can be found in the Indian Ocean, although semidiurnal are the most widespread. Semidiurnal tides prevail on the coast of <a href="https://www.britannica.com/place/eastern-Africa" class="md-crosslink autoxref " data-show-preview="true">eastern Africa</a> as far north as the <a href="https://www.britannica.com/place/Equator" class="md-crosslink " data-show-preview="true">Equator</a> and in the Bay of Bengal. The <a href="https://www.britannica.com/science/tide" class="md-crosslink " data-show-preview="true">tides</a> are mixed in the Arabian Sea and the inner part of the <a href="https://www.britannica.com/place/Persian-Gulf" class="md-crosslink autoxref " data-show-preview="true">Persian Gulf</a>. The southwestern coast of <a href="https://www.britannica.com/place/Australia" class="md-crosslink " data-show-preview="true">Australia</a> has a small area of diurnal tides, as do the coast of <a href="https://www.britannica.com/place/Thailand" class="md-crosslink " data-show-preview="true">Thailand</a> in the <a href="https://www.britannica.com/place/Andaman-Sea" class="md-crosslink " data-show-preview="true">Andaman Sea and</a> the south shore of the central Persian Gulf.</p><div class="module-spacing"> </div><span class="marker MOD5 mod-inline"></span> <span class="marker PREMOD6 mod-inline"></span><p class="topic-paragraph">Tidal ranges vary considerably from place to place in the Indian Ocean and its <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="adjacent" href="https://www.merriam-webster.com/dictionary/adjacent" data-type="MW">adjacent</a> seas. <a href="https://www.britannica.com/place/Port-Louis" class="md-crosslink " data-show-preview="true">Port Louis</a>, <a href="https://www.britannica.com/place/Mauritius" class="md-crosslink " data-show-preview="true">Mauritius</a>, for instance, has a spring tidal range of only 1.6 feet (0.5 metres), characteristic of islands in the open ocean. Other areas with low tidal ranges are <a href="https://www.britannica.com/place/Chennai" class="md-crosslink " data-show-preview="true">Chennai</a> (Madras), India (4.3 feet [1.3 metres]) and <a href="https://www.britannica.com/place/Colombo" class="md-crosslink " data-show-preview="true">Colombo</a>, <a href="https://www.britannica.com/place/Sri-Lanka" class="md-crosslink autoxref " data-show-preview="true">Sri Lanka</a> (2.3 feet [0.7 metres]). The greatest tidal ranges are found in the Arabian Sea, notably at Bhavanagar, India, in the <a href="https://www.britannica.com/place/Gulf-of-Khambhat" class="md-crosslink " data-show-preview="true">Gulf of Khambhat</a> (38 feet [11.6 metres]), and in the <a href="https://www.britannica.com/place/Gulf-of-Kachchh" class="md-crosslink " data-show-preview="true">Gulf of Kachchh</a> (Kutch) at Navlakhi (25.5 feet [7.8 metres]). High tidal ranges are also found in the eastern ocean; <a href="https://www.britannica.com/place/Sagar-Island" class="md-crosslink autoxref " data-show-preview="true">Sagar Island</a> in India, at the head of the Bay of Bengal, has a range of 17.4 feet (5.3 metres), and for <a href="https://www.britannica.com/place/Yangon" class="md-crosslink " data-show-preview="true">Yangon</a> (Rangoon), <a href="https://www.britannica.com/place/Myanmar" class="md-crosslink autoxref " data-show-preview="true">Myanmar</a>, at the north end of the Andaman Sea, the range is 18.4 feet (5.6 metres). Moderate ranges are found at <a href="https://www.britannica.com/place/Durban" class="md-crosslink " data-show-preview="true">Durban</a>, <a href="https://www.britannica.com/place/South-Africa" class="md-crosslink autoxref " data-show-preview="true">South Africa</a>, and <a href="https://www.britannica.com/place/Karachi" class="md-crosslink " data-show-preview="true">Karachi</a>, <a href="https://www.britannica.com/place/Pakistan" class="md-crosslink " data-show-preview="true">Pakistan</a> (both about 7.5 feet [2.3 metres]), and the <a href="https://www.britannica.com/place/Shatt-Al-Arab" class="md-crosslink " data-show-preview="true">Shatt Al-’Arab</a>, <a href="https://www.britannica.com/place/Iraq" class="md-crosslink " data-show-preview="true">Iraq</a> (11.3 feet [3.4 metres]).</p><span class="marker MOD6 mod-inline"></span> </section> </section> <span class="marker end-of-content"></span><span class="marker after-article"></span></div> <div id="chatbot-simplify-root"></div> <div id="chatbot-root"></div> </div> </div> </div> <div class="ai-dialog-placeholder"></div> </div> </div> <aside class="col-md-da-320"></aside> </div> </div> </div> </div> </article> </div> </div> </div> </div> </main> <div id="md-footer"></div> <noscript><iframe src="//www.googletagmanager.com/ns.html?id=GTM-5W6NC8" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript>  <script> window.ap3c = window.ap3c || {}; var ap3c = window.ap3c; ap3c.cmd = ap3c.cmd || []; ap3c.cmd.push(function() { ap3c.init('ZO4siT4cLwnykPnzZWJtd3Byb2Q', 'https://engage.email.britannica.com/'); ap3c.track({v: 0}); }); ap3c.activity = function(act) { ap3c.act = (ap3c.act || []); ap3c.act.push(act); }; var s, t; s = document.createElement('script'); s.type = 'text/javascript'; s.src = "https://engage.email.britannica.com/app.js"; t = document.getElementsByTagName('script')[0]; t.parentNode.insertBefore(s, t); </script> <script class="marketing-page-info" type="application/json"> {"pageType":"Topic","templateName":"DESKTOP","pageNumber":5,"pagesTotal":8,"pageId":285876,"pageLength":865,"initialLoad":true,"lastPageOfScroll":false} </script> <script class="marketing-content-info" type="application/json"> [] </script> <script src="https://cdn.britannica.com/mendel-resources/3-133/js/libs/jquery-3.5.0.min.js?v=3.133.36"></script> <script type="text/javascript" data-type="Init Mendel Code Splitting"> (function() { $.ajax({ dataType: 'script', cache: true, url: 'https://cdn.britannica.com/mendel-resources/3-133/dist/topic-page.js?v=3.133.36' }); })(); </script> <script class="analytics-metadata" type="application/json"> {"leg":"C","adLeg":"C","userType":"ANONYMOUS","pageType":"Topic","pageSubtype":null,"articleTemplateType":"PAGINATED","gisted":false,"pageNumber":5,"hasSummarizeButton":false,"hasAskButton":true} </script> <script type="text/javascript"> EBStat={accountId:-1,hostnameOverride:'webstats.eb.com',domain:'www.britannica.com', json:''}; </script> <script type="text/javascript"> ( function() { $.ajax( { dataType: 'script', cache: true, url: '//www.britannica.com/webstats/mendelstats.js?v=1' } ) .done( function() { try {writeStat(null,EBStat);} catch(err){} } ); })(); </script> <div id="bc-fixed-dialogue"></div> </body> </html>

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Indian Ocean - Upwelling, Climate, Marine Life | Britannica