Dissolved silicon and its isotopes in the water column of the Bay of Bengal: internal cycling versus lateral transport
The concentration of dissolved Si and its isotope composition are measured in the Bay of Bengal (BoB) region of the northern Indian Ocean; the isotope data are the first data set from the northern Indian Ocean. The measurements are made in eight depth profiles closely along the 87°E transect (GIO1 s...
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ftindianacasci:oai:repository.ias.ac.in:106276 2023-05-15T18:26:03+02:00 Dissolved silicon and its isotopes in the water column of the Bay of Bengal: internal cycling versus lateral transport Singh, Satinder Pal Singh, Sunil Kumar Bhushan, Ravi Rai, Vinai Kumar 2015 http://repository.ias.ac.in/106276/ http://www.sciencedirect.com/science/article/pii/S0016703714007285 unknown Elsevier Science Singh, Satinder Pal Singh, Sunil Kumar Bhushan, Ravi Rai, Vinai Kumar (2015) Dissolved silicon and its isotopes in the water column of the Bay of Bengal: internal cycling versus lateral transport Geochimica et Cosmochimica Acta, 151 . pp. 172-191. ISSN 0016-7037 Q Science (General) Article PeerReviewed 2015 ftindianacasci 2018-02-16T23:11:11Z The concentration of dissolved Si and its isotope composition are measured in the Bay of Bengal (BoB) region of the northern Indian Ocean; the isotope data are the first data set from the northern Indian Ocean. The measurements are made in eight depth profiles closely along the 87°E transect (GIO1 section of the international GEOTRACES program) and in a few samples from the northern shelf of the bay. Dissolved Si in the water column varies from ∼0.6 to ∼152.5 μmol/kg, whereas the δ 30 Si data cover a range +1.2‰ to +3.6‰. The depth profiles of dissolved Si show generally lower values in the surface increasing with depth, whereas the pattern reverses in the case of δ 30 Si. These vertical distribution patterns of Si and δ 30 Si are similar to those reported in other oceanic regions and suggestive of the significant role of biological processes in governing Si biogeochemistry in the upper layers (top ∼1500 m). In contrast, dissolved Si in near surface waters of the northern shelf and the southernmost station is exceptionally high. These results indicate a continental supply of dissolved Si from the Ganga–Brahmaputra river system (G–B) and submarine groundwater discharge (SGD) to the shelf region, and an intrusion of high salinity waters from the Arabian Sea in the southern bay. The δ 30 Si values of ∼1.34 ± 0.10‰ for deep/bottom waters of the BoB (depth >1500 m) are similar to those reported for the deep Southern Ocean and indicate the dominant control of water mass mixing. The dissolved Si concentrations in the bottom waters of the BoB are generally higher than those of the water mass endmembers, which suggest the need for an additional source of Si; in situ particle dissolution and/or benthic release in the central bay seem to be the potential candidate. The annual Si budget in the top ∼100 m of the BoB seems to suggest that meso-scale eddies frequently occurring during non-monsoon periods can supply at the most ∼2.6 g Si/m 2 /year, which is about 33% of the Si requirement to support new production in the bay. The supply of dissolved Si (∼1.3 ± 0.5 × 1011 mol/year) from the G–B river system and SGD has been calculated based on the distributions of dissolved Si concentration and δ 30 Si in the northern shelf waters. A comparison of this supply with the reported Si flux upstream of the estuarine zone indicates about 40% removal of dissolved Si in the G–B estuary. The mass balance of Si isotopes in the deep waters indicates that the dissolution of diatoms is the main cause of excess Si in the bay. Article in Journal/Newspaper Southern Ocean Indian Academy of Sciences: Publication of Fellows Indian Southern Ocean |
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Indian Academy of Sciences: Publication of Fellows |
op_collection_id |
ftindianacasci |
language |
unknown |
topic |
Q Science (General) |
spellingShingle |
Q Science (General) Singh, Satinder Pal Singh, Sunil Kumar Bhushan, Ravi Rai, Vinai Kumar Dissolved silicon and its isotopes in the water column of the Bay of Bengal: internal cycling versus lateral transport |
topic_facet |
Q Science (General) |
description |
The concentration of dissolved Si and its isotope composition are measured in the Bay of Bengal (BoB) region of the northern Indian Ocean; the isotope data are the first data set from the northern Indian Ocean. The measurements are made in eight depth profiles closely along the 87°E transect (GIO1 section of the international GEOTRACES program) and in a few samples from the northern shelf of the bay. Dissolved Si in the water column varies from ∼0.6 to ∼152.5 μmol/kg, whereas the δ 30 Si data cover a range +1.2‰ to +3.6‰. The depth profiles of dissolved Si show generally lower values in the surface increasing with depth, whereas the pattern reverses in the case of δ 30 Si. These vertical distribution patterns of Si and δ 30 Si are similar to those reported in other oceanic regions and suggestive of the significant role of biological processes in governing Si biogeochemistry in the upper layers (top ∼1500 m). In contrast, dissolved Si in near surface waters of the northern shelf and the southernmost station is exceptionally high. These results indicate a continental supply of dissolved Si from the Ganga–Brahmaputra river system (G–B) and submarine groundwater discharge (SGD) to the shelf region, and an intrusion of high salinity waters from the Arabian Sea in the southern bay. The δ 30 Si values of ∼1.34 ± 0.10‰ for deep/bottom waters of the BoB (depth >1500 m) are similar to those reported for the deep Southern Ocean and indicate the dominant control of water mass mixing. The dissolved Si concentrations in the bottom waters of the BoB are generally higher than those of the water mass endmembers, which suggest the need for an additional source of Si; in situ particle dissolution and/or benthic release in the central bay seem to be the potential candidate. The annual Si budget in the top ∼100 m of the BoB seems to suggest that meso-scale eddies frequently occurring during non-monsoon periods can supply at the most ∼2.6 g Si/m 2 /year, which is about 33% of the Si requirement to support new production in the bay. The supply of dissolved Si (∼1.3 ± 0.5 × 1011 mol/year) from the G–B river system and SGD has been calculated based on the distributions of dissolved Si concentration and δ 30 Si in the northern shelf waters. A comparison of this supply with the reported Si flux upstream of the estuarine zone indicates about 40% removal of dissolved Si in the G–B estuary. The mass balance of Si isotopes in the deep waters indicates that the dissolution of diatoms is the main cause of excess Si in the bay. |
format |
Article in Journal/Newspaper |
author |
Singh, Satinder Pal Singh, Sunil Kumar Bhushan, Ravi Rai, Vinai Kumar |
author_facet |
Singh, Satinder Pal Singh, Sunil Kumar Bhushan, Ravi Rai, Vinai Kumar |
author_sort |
Singh, Satinder Pal |
title |
Dissolved silicon and its isotopes in the water column of the Bay of Bengal: internal cycling versus lateral transport |
title_short |
Dissolved silicon and its isotopes in the water column of the Bay of Bengal: internal cycling versus lateral transport |
title_full |
Dissolved silicon and its isotopes in the water column of the Bay of Bengal: internal cycling versus lateral transport |
title_fullStr |
Dissolved silicon and its isotopes in the water column of the Bay of Bengal: internal cycling versus lateral transport |
title_full_unstemmed |
Dissolved silicon and its isotopes in the water column of the Bay of Bengal: internal cycling versus lateral transport |
title_sort |
dissolved silicon and its isotopes in the water column of the bay of bengal: internal cycling versus lateral transport |
publisher |
Elsevier Science |
publishDate |
2015 |
url |
http://repository.ias.ac.in/106276/ http://www.sciencedirect.com/science/article/pii/S0016703714007285 |
geographic |
Indian Southern Ocean |
geographic_facet |
Indian Southern Ocean |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_relation |
Singh, Satinder Pal Singh, Sunil Kumar Bhushan, Ravi Rai, Vinai Kumar (2015) Dissolved silicon and its isotopes in the water column of the Bay of Bengal: internal cycling versus lateral transport Geochimica et Cosmochimica Acta, 151 . pp. 172-191. ISSN 0016-7037 |
_version_ |
1766207875096510464 |