Chemical characteristics of Central Indian Basin waters during the southern summer (original) (raw)
Related papers
Biogeochemistry of the north Indian Ocean
2006
(Chairman). The Committee decided that a series of status reports be prepared on specific topics by leading Indian experts so that Indian work could be highlighted at various fora and general awareness be created among scientists and science students. Humanity lived in harmony with nature until the industrialization began in the middle of the nineteenth century. Rapid industrialization took place to meet the ever-growing demands to raise living standards and comforts of life. It led to the human interference with the global climate. While the levels of greenhouse gas abundances in atmosphere fluctuated, particularly between ice and non-ice ages, the rates of their increase in the last century-and-a-half are unprecedented in the Earth's history leading to Global (Climate) Change. Concerned over the consequences of 'Global Change' the humanity became curious to understand the 'Biogeochemistry of the Earth system' in its totality. The most appreciated consequence is its impact on regional climate forcing mechnaisms and the associated biogeochemical processes, which is the most relevant to South Asia. The Asian Monsoon is a unique climate force and the most significant tropical system in the world, on which the regional economy and food resources are heavily dependent. The Monsoon associated processes not only drive agriculture industry in South Asia but also biogeochemical processes on land and in the surrounding seas. Although the 'monsoon' is the primary driving force of the regional biogeochemistry, alterations in its intensity and coverage, due to global change, can cause changes on the rates of these processes and land-atmosphere-ocean feedbacks. Therefore, it is fundamental to understand the biogeochemistry of this region with a holistic view. Furthermore, it is important to recognize that not only the geographical setting of the North Indian Ocean is different from its counterparts in the Pacific and Atlantic Oceans but also the oceanic processes are distinctly different between the two of its basins, the Arabian Sea and the Bay of Bengal. The present booklet dealing with 'Ocean Biogeochemistry' is the first in the IGBP-WCRP-SCOPE series. This booklet highlights the characteristics of ocean biogeochemical processes in the North Indian Ocean, with special reference to land-atmosphere-ocean interactions. I hope this contribution will prove useful to the students, academicians, researchers, and other interested in biogeochemistry and climate of our region.
Deep Sea Research Part II: Topical Studies in Oceanography, 2001
As a part of Indian Deep Sea Environment Experiment (INDEX) aimed at assessing the environmental impact of manganese nodule mining in the Central Indian Basin (CIB), a study on baseline physical conditions of water column viz. potential temperature (y), salinity and potential density together with geostrophic circulation regime in the deeper depths of the basin was conducted. The hydrography data used in the present analysis were collected over a wide area of the western part of CIB (711-791E; 91-141S) during austral summer (January 1997) from the Indian research vessel ORV Sagar Kanya, while during the austral winter season (June-July 1997), hydrographical stations were occupied by Russian research vessel RV Yuzhmorgeologia in the central part of CIB (751-771E; 91-111S) where a benthic disturbance on experimental scale was carried out. The spatial variations in the physical parameters decreased below 3500 m, inferring a restricted basin-scale deep circulation. The dynamic topography field at 5000 m relative to 2000 db surface in the central part of CIB, representing the abyssal circulation, was generally characterized by a southwestward weak flow around 101S flanked by cyclonic and anti-cyclonic eddies on its right and left sides, respectively. This flow regime agreed with the earlier one inferred by Warren (J. Mar. Res. 40 (1982) 823) linking the source of deep water in CIB to a saddle overflow across Ninetyeast Ridge from West Australian Basin around 101S.
Biogeochemical cycling in the northwestern Indian Ocean: a brief overview
Deep Sea Research Part II: Topical Studies in Oceanography, 1993
THE northwestern Indian Ocean may be defined conveniently as the ocean basin that is bounded by the African and Asian land masses to the west and north, and the Indian subcontinent and the Maldives to the east. With a southern boundary chosen arbitrarily as the Equator, its area is about 6.2 x 106 km 2. Although it is one of the smallest ocean basins, it contains a diversity of biogeochemical provinces such as eutrophic, oligotrophic, upwelling and reduced oxygen environments. The presence of such diversity within a small ocean basin has made it an attractive location for biogeochemical studies. Many of these have been reviewed by WYRTKI (1971), ZEITZSCHEL (1973), KREY and BABENERD (1976), ANGEL (1984) and HAQ and MILLIMAN (1984). In this issue, we report the results of more recent biogeochemical studies carried out abroad R.
Journal of Geophysical Research, 2011
1] Within the Subantarctic Mode Water (SAMW) density level, we study temporal changes in salinity, nutrients, oxygen and TTD (Transit Time Distribution) ages in the western (W) and eastern (E) subtropical gyre of the Indian Ocean (IO) from 1987 to 2002. Additionally, changes in Total Alkalinity (TA) and Dissolved Inorganic Carbon (DIC) are evaluated between 1995 and 2002. The mechanisms behind the detected changes are discussed along with the results from a hindcast model run (Community Climate System Model). The increasing salinity and decreasing oxygen trends from 1960 to 1987 reversed from 1987 to 2002 along the gyre. In the W-IO a decreasing trend in TTD ages points to a faster delivery of SAMW, thus less biogenic matter remineralization, explaining the oxygen increase and noisier nutrients decrease. In the E-IO SAMW, no change in TTD ages was detected, therefore the trends in oxygen and inorganic nutrients relate to changes in the Antarctic Surface Water transported into the E-IO SAMW formation area. In the W-IO between 1995 and 2002, the DIC increase is equal or even less than the anthropogenic input as the reduction in remineralization contributes to mask the increasing trend. In the E-IO between 1995 and 2002, DIC decreases slightly despite the increase in the anthropogenic input. Differences in the preformed E-IO SAMW conditions would explain this behavior. Trends in the W and E IO SAMW are decoupled and related to different forcing mechanisms in the two main sites of SAMW formation in the IO, at 40°S-70°E and 45°S-90°E, respectively. Citation: Álvarez, M., T. Tanhua, H. Brix, C. Lo Monaco, N. Metzl, E. L. McDonagh, and H. L. Bryden (2011), Decadal biogeochemical changes in the subtropical Indian Ocean associated with Subantarctic Mode Water,
Δ 14 C, ΣCO 2 and salinity of the Western Indian Ocean Deep Waters: Spatial and temporal variations
Geophysical Research Letters, 1999
Indian Ocean Deep waters (IDW) show an increase in salinity and ZCO2 between 64øS and 16+4øN by 0.106-0.110%o and 82-104 gM kg-1 respectively with a corresponding decrease in A•4C by 42%0 as revealed by the GEOSECS data (1977-78). The A•4C-ZCO2-Salinity relationships show better correlation in the western sector. High biological productivity induced changes and corrosive deepwaters could account for ECO2 increase in the northern regions. Reoccupation of GEOSECS stations during 1985-95 do not show distinctly discernible short-term temporal changes in A•4C, ECO2 and salinity. [1976] based on GEOSECS Atlantic data observed decreasing trend in A I4c and a similar trend for salinity m the deep water masses of North Atlantic Deep Water (NADW) and Antarctic Bottom Waters (AABW) between 36øN and 60øS. GEOSECS measurements made in the Indian Ocean [Stuiver and Ostlund, 1983] provide a good database for evaluating spatial variations in this region. As a part of the present study to understand circulation and air-sea exchange of CO2 using •4C [Bhushan et al.
Hydrographic characteristics of the Indian sector of the Southern Ocean
Oceanographic studies in the Indian sector of the Southern Ocean (58-61 degrees S and 30-40 degrees E) carried out during December 1995 and March 1996 indicate a 3-layer structure typical of summer in the oceanic domain south of the Antarctic Polar Front. The upper 300 m water column consists of three distinctive thermohaline characteristics. The surface layer (50 m) of summer surface water formed by seasonal warming with temperatures (0-2 degrees C) and low salinity (less than 33.8 PSU), the intermediate layer (50-150 m) of winter reminiscent water with negative temperatures (0 to 2 degrees C) and moderate salinity (33.8-34.3 PSU) and the deeper layer below 150 m) of Circumpolar Deep Watermass (CDW) with positive temperatures (0-2 degrees C) and higher salinity (34.3-34.8 PSU). The influence of the strong Antarctic Divergence between the east and west drifts is noticed at 61 degrees S, 34 degrees E marked by phytoplankton and zooplankton patches. The dissolved oxygen (DO) shows hig...
Paleoceanography, 2007
1] A down-core 231 Pa/ 230 Th record has been measured from the southwestern Indian Ocean to reconstruct the history of deep water flow into this basin over the last glacial-interglacial cycle. The ( 231 Pa xs / 230 Th xs ) 0 ratio throughout the record is nearly constant at approximately 0.055, significantly lower than the production ratio of 0.093, indicating that the proxy is sensitive to changes in circulation and/or sediment flux at this site. The consistent value suggests that there has been no change in the inflow of Antarctic Bottom Water to the Indian Ocean during the last 140 ka, in contrast to the changes in deep circulation thought to occur in other ocean basins. The stability of the ( 231 Pa xs / 230 Th xs ) 0 value in the record contrasts with an existing sortable silt (SS) record from the same core. The observed SS variability is attributed to a local geostrophic effect amplifying small changes in circulation. A record of authigenic U from the same core suggests that there was reduced oxygen in bottom waters at the core locality during glacial periods. The consistency of the ( 231 Pa xs / 230 Th xs ) 0 record implies that this could not have arisen by local changes in productivity, thus suggesting a far-field control: either globally reduced bottom water oxygenation or increased productivity south of the Opal Belt during glacials. Citation: Thomas, A. L., G. M. Henderson, and I. N. McCave (2007), Constant bottom water flow into the Indian Ocean for the past 140 ka indicated by sediment 231 Pa/ 230 Th ratios, Paleoceanography, 22, PA4210,
Water-column remineralization in the Indian sector of the Southern Ocean during early spring
Deep Sea Research Part II: Topical Studies in Oceanography, 2002
The vertical distribution of remineralization assessed through the respiratory activity of the electron transport system (ETS) in microbial communities (o200 mm) was studied from surface to 1000 m depth, at seven stations along a latitudinal gradient extending from the Polar Front region (491S) to the ice edge (591S) at 621E, during October 1995. A net imbalance between primary production and water-column remineralization occurred in the area of influence of the Polar Front (from 491S to 531S), while near the ice edge both processes were in approximate equilibrium. In the Polar Front region, community respiration in the mixed layer (15-35 mmol C m À2 day À1 ) exceeded primary production *Corresponding : S 0 9 6 7 -0 6 4 5 ( 0 2 ) 0 0 0 0 8 -5 l'advection de mati" ere organique " a partir du plateau de Crozet o " u des efflorescences de phytoplancton se produisent tout au long de l'ann! ee, stimul! ees probablement par une enrichissement en fer. Ce transport de surface serait assur! e par des veines de courant fort r! esultant de la fragmentation du courant circumpolaire antarctique, au sud ouest de la dorsale indienne. Les vitesses de respiration relativement ! elev! ees observ! ees en dessous de 500 m confortent la pr! esence d'un transport profond de mati! ere organique. Nos r! esultats sugg! erent que le carbone organique dissous devrait # etre la source principale de mati! ere organique advect! ee dans la r! egion durant la p! eriode d'! etude. La valeur moyenne de production de carbone organique export! ee, calcul! ee " a partir des activit! es respiratoires et extrapol! ee sur une p! eriode de un an (B1.5 mol C m À2 y À1 ), repr! esente environ 25% des estimations r! ecentes de production primaire brute annuelle dans l'oc! ean Austral.
modified Antarctic Intermediate Water, the Indonesian Subsurface Water, the Indonesian
2016
Abstract. A multiparametric approach is used to analyze the seasonal properties of water masses in the eastern Indian Ocean. The data were measured during two cruises of the Java Australia Dynamic Experiment (JADE) program carried out during two opposite seasons: August 1989 (SE monsoon) and February-March 1992 (NW monsoon). These cruises took place at the end of a La Nifia event and during an E1 Nifio episode, respectively. Seven sources have been identified in the studied region for the 200-800 m layer: the Subtropical Indian Water, the Indian Central Water, the