@article{,

title = {Variability of water properties, heat and salt fluxes in the Arabian Sea, between the onset and wane of the 1995 southwest monsoon},

author = {Beal,L.M.,Chereskin,T.K.,Bryden,H.L.,Ffield,A.},

year  = {2003},

date = {2003-01-01},

journal = {Deep-Sea Research Part II},

volume = {50},

number = {42},

pages = {2049-2075},

abstract = {We investigate the variability of the circulation,water masses,heat and salt fluxes in the Arabian Sea over the course of the southwest monsoon. Two zonal sections taken along 8§30'N in 1995 as part of the Indian Ocean WOCE hydrographic program are used. The first was occupied in early June at the onset of the southwest monsoon winds,the second in late September,at the wane of the monsoon. The September section was found to be generally warmer (+0.32§C) and saltier (+0.04) than in June,despite a 50mm drop in mean sea level. Therefore,the common assumption that an increase in sea-surface height follows an increase in heat content (the hydrostatic response) does not hold. Instead,we conclude that the heat content increases due to the advection of Arabian Sea Surface Water and Red Sea Water onto the section from the north,and the drop in sea level is due to a loss of mass,rather than heat,from the water column. There are large uncertainties involved in diagnosing the heat-flux divergence across the Arabian Sea, because the seasonal variability of the water masses and circulation in the basin mean that our data are not representative of a steady state. We treat each section separately and find an oceanic heat export of -0.72PW in June and -0.19PW in September,implying a basin cooling rate of about -0.36PW in June and a slight heating of 0.12PW in September. In June the mass and heat balances are dominated by the Ekman transport and the Somali Current,with very flat density surfaces resulting in a small interior geostrophic transport. By September the Ekman transport has reduced,and it is primarily the interior transport that balances a strong Somali Current. There are two main overturning cells in June and September: A shallow one of approximate magnitude 15 Sv in June and 0 Sv in September, which reaches depths of no more than 500m and is driven by Ekman divergence at the surface; and a deep cell of magnitude 1 Sv representing a weak inflow and subsequent upwelling of Circumpolar Deep water. The deep cell implies a basin-averaged upwelling velocity of 3.2x10-5 cm s-1 through 2200 m.},

keywords = {Arabian Sea, density, depth, Indian Ocean, Oceanic, Red Sea, Upwelling},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {The role of seasonal and diel changes in mixed-layer depth on carbon and chlorophyll distributions in the Arabian Sea},

author = {Gardner,W.D.,Gundersen,J.S.,Richardson,M.J.,Walsh,I.D.},

year  = {1999},

date = {1999-01-01},

journal = {Deep-Sea Research Part II},

volume = {46},

number = {97},

pages = {1833-1858},

abstract = {The e!ects of changes in the mixed-layer depth on the distribution of particulate organic carbon (POC) and chlorophyll a were examined in the Arabian Sea during the Northeast Monsoon (January and December), Spring Intermonsoon (February-March), and Southwest Monsoon (July and August) of 1995. POC distributions were derived from profiles of beam attenuation calibrated with POC, and chlorophyll a distributions were derived from calibrated fluorescence profiles. Depth of the seasonal mixed layer (Då of 0.125 kg m-3  from surface density) increased with distance offshore during both monsoons, especially in the southern Arabian Sea where the range was 10-80 m nearshore to 80-120 m offshore. The deepest seasonal mixed layers occurred during the Northeast Monsoon. During the Spring Intermonsoon the seasonal mixed layer was only 10-40 m. Variations in the depth of the diel mixed layer (Då of 0.03 kg m-3  from surface density) were up to 90 m during the Northeast Monsoon, but were seldom over 20 m during the Southwest Monsoon. During the Spring Intermonsoon when mixed layers and diel variations in the mixed layer were small, nutrients became depleted, producing oligotrophic conditions plus a strong deep chlorophyll a maximum (>2 mg chl m-3) below the mixed layer. The chlorophyll a maximum was centered at ~ 50 m, which is significantly beneath the effective depth of satellite color sensing. When mixing is active throughout the diel cycle, particulate organic carbon (POC) and chlorophyll distributions are quite uniform within the mixed layer. Nighttime increases in mixed layer depths can mix POC and chlorophyll a produced during the day downward and can entrain new nutrients to enhance primary production. Although mixing from diel variations may be effective in redistributing components within the mixed layer and may be an important mechanism for removing particles from the mixed layer, regional upwelling of nutrients and diatom blooms appear to dominate over diel mixed layer dynamics in the production and export of carbon in the Arabian Sea.},

keywords = {Arabian Sea, chlorophyll, density, depth, diel, Distribution, nearshore, Oceanic, Upwelling},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {The oxygen minimum zone in the Arabian Sea during 1995},

author = {Morrison,J.M.,Codispoti,L.A.,Smith,S.L.,Wishner,K.,Flagg,C.,Gardner,W.D.,Gaurin,S.,Naqvi,S.W.A.,Manghnani,V.,Prosperie,L.,Gundersen,J.S.},

year  = {1999},

date = {1999-01-01},

journal = {Deep-Sea Research Part II},

volume = {46},

number = {174},

pages = {1903-1931},

abstract = {This paper focuses on the characteristics of the oxygen minimum zone (OMZ) as observed in the Arabian Sea over the complete monsoon cycle of 1995. Dissolved oxygen, nitrite, nitrate and density values are used to delineate the OMZ, as well as identify regions where denitrification is observed. The suboxic conditions within the northern Arabian Sea are documented, as well as biological and chemical consequences of this phenomenon. Overall, the conditions found in the suboxic portion of the water column in the Arabian Sea were not greatly different from what has been reported in the literature with respect to oxygen, nitrate and nitrite distributions. Within the main thermocline, portions of the OMZ were found that were suboxic (oxygen less than ~4.5 æM) and contained secondary nitrite maxima with concentrations that sometimes exceeded 6.0 æM, suggesting active nitrate reduction and denitrification. Although there may have been a reduction in the degree of suboxia during the Southwest monsoon, a dramatic seasonality was not observed, as has been suggested by some previous work. In particular, there was not much evidence for the occurrence of secondary nitrite maxima in waters with oxygen concentrations greater than 4.5 æM. Waters in the northern Arabian Sea appear to accumulate larger nitrate deficits due to longer residence times even though the denitrification rate might be lower, as evident in the reduced nitrite concentrations in the northern part of the basin. Organism distributions showed string relationships to the oxygen profiles, especially in locations where the OMZ was pronounced, but the biological responses to the OMZ varied with type of organism. The regional extent of intermediate nepheloid layers in our data corresponds well with the region of the secondary nitrite maximum. This is a region of denitrification, and the presence and activities of bacteria are assumed to cause the increase in particles. ADCP acoustic backscatter measurements show diel vertical migration of plankton or nekton and movement into the OMZ. Daytime acoustic returns from depth were strong, and the dawn sinking and dusk rise of the fauna were obvious. However, at night the biomass remaining in the suboxic zone was so low that no ADCP signal was detectable at these depths. There are at least two groups of organisms, one that stays in the upper mixed layer and another that makes daily excursions. A subsurface zooplankton peak in the lower OMZ (near the lower 4.5 æM oxycline) was also typically present; these animals occurred day and night and did not vertically migrate.},

keywords = {acoustic, Arabian Sea, density, depth, diel, Distribution, location, migrate, migration, occurrence, oxygen minimum, plankton, thermocline, zooplankton},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {On the ecology and feeding habits of the euphausiids (Crustacea) in the Arabian Sea (Zur Okologie und Eranhrungsbiologie der Euphausiaceen (Crustacea) im Arabischen Meer)},

author = {Weigmann,R.},

year  = {1970},

date = {1970-01-01},

journal = {Meteor Forschungsergeb.},

volume = {5},

number = {498},

pages = {11-52},

abstract = {In the present paper, the ecology and feeding habits of euphausiids are described. The samples were taken at the time of the NE-monsoon (1964/65) by R. V. 'Meteor' in the Arabian Sea and adjacent waters. 24 spp were determined. According to distribution of the spp, the following marine areas can be distinguished: Arabian Sea: 24 spp, dominant are Euphausia diomedeae, E. tenera, E. distinguenda,  Stylocheiron carinatum. Gulf of Aden: 1 0 spp, dominant are Euphausia diomedeae, E. distinguenda.  Red Sea: 6 spp, dominant are Euphausia diomedeae, E. distinguena. Gulf of Oman: 5 spp, dominant are Euphausia distinguenda, Pseudeuphausia latifrons. Persian Gulf: 1 sp- Pseudeuphausia latifrons. The total number of euphausiids indicate the biomass of this group. High densities of euphausiids (200-299 and > 300 individuals/l00 m super(3)) occur in the innermost part of  the Gulf of Aden, in the area south of the Euqator near the African east coast, near Karachi (Indian west coast) and in the Persian Gulf.   Comparison with data relating to production biology confirms that these are eutrophic zones which coincide with areas in which upwelling occurs at the time of the NE-monsoon. The central part of the Arabian Sea differs from adjacent waters by virtue of less dense euphasiid populations (>199 individuals/lOO m super(3)). Measurements relating to production biology demonstrate a relatively low concentration of primary food sources. Food material was ascertained by analysis of stomach content. The following omnivorous species were examined: Euphausia diomedeae, E. distinguenda, E. tenera, Pseudeuphausia latifronts and Thysanopoda tricuspidata. Apart from crustacean remains large numbers  of Foraminifera, Radiolaria, tintinnids, dinoflagellates were found in the stomachs. Quantitatively crustaceans form the most important item in the diet. Food selection on the basis of size an form appears to be restricted to certain genera of tintinnids. The genera Stylocheiron and Nematoscelis are predators. Only crustacean remains were found in the stomachs of Stylocheiron abbreviatum, whereas Radiolaria, Foraminifera and tintinnids occurred to some extent in Nematoscelis sp. Different euphauisiids occupy different positions in the food chain in the Arabian Sea. In omnivorous species the position is variable, since they not only feed by filtering autotrophic and heterotrophic Protista, but also by predation on zooplankton. Carnivorous spp without filtering apparatus feed exclusively on zooolankton of the size of copepods. Only these spp are well established as occupying a higher position in food chain. The parasrtlc protozoan Thalassomyces fagei was found on Euphausia diomedeae, E. tenera, E. distinguenda and E. sanzoi.},

keywords = {Arabian Sea, biology, density, diet, Distribution, ecology, Euphausiid, feeding, Gulf of Aden, Gulf of Oman, marine, Oman, population, populations, predation, Red Sea, Upwelling, zooplankton},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Remarks on the distribution and migration of whales},

author = {Slijper,E.J.,Van Utrecht,W.L.,Naaktgeboren,C.},

year  = {1964},

date = {1964-01-01},

journal = {Bijdragen tot de Dierkunde},

volume = {34},

number = {475},

pages = {4-86},

abstract = {The authors gained the cooperation of the Netherlands Association of Ship Owners and the Royal Netherlands Navy in a project to collect all whale sightings from vessels sailing around the globe between 1954 and 1957. A total of 4500 reports of 11,000 animals were received, with the majority of observations coming from the Atlantic and Indian Oceans. Vessels were given identification guides and all reported observations were scored on the perceived reliability of the identification.  All Rorqual whales were grouped together, and a further distinction was made between humpback, sperm, right whales and "little piked whales" (minke whales).  Sightings were plotted in 10 degree squares according to number of whales observed per 1000 hours steamed in daylight.  Special attention is given to the observations of Captain W.F.J. Morzer Bruins, who the authors describe as a keen naturalist whose observations hold more credibility than those of others.  His observations in the Indian Ocean include a high number of sperm whales off the southern coast of Oman and the Gulf of Aden in January-March and April-June, a scattering of stranded blue and fin whales along the W coast of India, and only 2 stranded and 2 live humpback whales (strandings both in India, and live sightings near Yemen/Oman border? and off S tip of India (near Maldives?).  The larger number of compiled sightings from vessels are presented by species.  Rorqual sightings were plentiful in the Gulf of Aden, Arabian Sea coasts of Oman and Pakistan, and in the Arabian Gulf (but not as plentiful as they were in the area between 30 and 40 degrees S.  The author concludes that the majority of the whales observed in the NIO do not belong to the Southern Hemisphere stock, but suggests that they migrate from the North Pacific through the Indonesian Archipelago and the Strait Malaya (despite very few observations here).  He briefly considers, but discards as unlikely, the hypothesis of a resident NIO stock.The total number of humpback whale sightings in the IO amounted to 500 (compared to 1618 rorqual sightings and 799 "whale" sightings).  The majority of animals were observed in coastal waters, and NIO sightings were generally concentrated in the months of Aug-Nov and Jan-April.  some of the highest recorded densities in the NIO are off of Pakistan  in the months of March, Aug, Oct, and December, but it is not clear how closely related this is to observer effort.  Observations are very few in May, June, July and September, and the authors do not link this to the monsoon -but rather conclude that the whales are not present at that time. Although few calves were observed in the NIO, those that were observed, were all observed in November, January or September (but no indication is given of calf size). The authors conclude that this is evidence that the observed whales do not belong to the S. Hem stock, but are more likely from the N.Pacific, despite the fact that there are "no sightings of humpbacks in the south China Sea or the Indonesian Archipelago that could support this assumption".  Sperm whales were observed with regularity throughout the year in the NIO, but in lower densities than Rorquals.  A low number of sightings in the NIO during summer months again leads the author to conclude that the animals either migrate South or to the N. Pacific.  This species, according to the authors is always associated with areas of high productivity.Minke whales were recorded in low densities in the Gulf of Aden and off the coast of Pakistan, but not in the central or Northern coasts of Oman.},

keywords = {Arabian Gulf, Arabian Sea, Atlantic, density, Distribution, fin whale, Gulf of Aden, Humpback Whale, humpback whales, India, Indian Ocean, Maldives, migration, minke whale, minke whales, North Pacific, Oman, Pakistan, productivity, right whale, right whales, Southern Hemisphere, sperm whale, sperm whales, Strandings, whale, whales},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Whales observed in the Indian Ocean: notes on their distribution},

author = {Brown,S.G.},

year  = {1957},

date = {1957-01-01},

journal = {The Marine Observer},

volume = {27},

number = {339},

pages = {157-165},

abstract = {The paper provides a summary of the results of a questionnaire put to merchant ships and other vessels, 80 of which provided their track data.  These vessels apparently had someone on watch during all daylight hours and reported all their cetacean sightings.  The authors feel confident that while some sightings could not be identified to species level, a distinction could be drawn between sperm, humpback and "rorqual" whales.  The "search effort" and sightings of the ships are plotted in the paper, with the majority of search effort and a high concentration of sightings occurring in the Gulf of Aden and S coast of Oman.  Only two humpback whale sightings are recorded for the Northern Arabian sea - one near the horn of Africa/Somalia, and one near Sharbitat/Likbe.  An additional string 4 of humpback whale sightings are recorded off the SW coast of India in the region of the Laccadive Islands.The author himself concludes: "There is apparently no great difference in the overall density of the large whale populations per unit area north and south of the equator. The highest concentrations of whales in the Indian Ocean occur in the Gulf of Aden and its approaches, the Arabian Sea and in the zone between South Africa and Australia. The least concentration is found in the Central Indian Ocean.  In summer the concentration of baleen whales in the Antarctic is very many times greater than in the Indian Ocean but there is much less difference in winter . The number of sperm whales in the ocean as a whole seems not to outnumber that of the different species of baleen whales combined. Humpback whales and rorquals are found unexpectedly far north, on the supposition that they all belong to the southern hemisphere populations. Rorquals have been observed right across the 30ø to 40ø S. zone between South Africa and Australia where ships might be expected to intercept them occasionally during their migrations."},

keywords = {Antarctic, Arabian Sea, Australia, baleen whales, Central Indian Ocean, cetacean, density, Distribution, Gulf of Aden, Humpback Whale, humpback whales, India, Indian Ocean, Oman, population, South Africa, Southern Hemisphere, sperm whale, sperm whales, whale, whales},

pubstate = {published},

tppubtype = {article}

}