Anthropogenic activities are likely to cause global warming. Global warming will affect marine productivityand thus food availability for marine organisms. Both the seawater temperature and food availability affect be...Anthropogenic activities are likely to cause global warming. Global warming will affect marine productivityand thus food availability for marine organisms. Both the seawater temperature and food availability affect benthicforaminifera, the most abundant marine calcareous microorganisms. Therefore, a laboratory culture experiment wasconducted on Cymbaloporetta plana to understand the coupled effect of temperature(25°C, 27°C, 30°C) and food(102±5,203±9, 305±14, 407±18, 508±23 diatom cells). At all temperatures, growth increased with increase in food. The specimenssubjected to 27°C temperature attained the maximum growth and those subjected to 25°C were the smallest. All specimensfed with 508±23 cells reproduced, 0 irrespective of temperature. Of all the specimens without food, 40% at 27°C and 20% at25°C reproduced, whereas specimens subjected to 30°C did not reproduce. The 100% rate of reproduction at 27°C suggeststhat it is the optimum temperature for growth and reproduction. All the specimens at 30°C and without additional food,died, whereas at 25°C and 27°C, the mortality rate was 80% and 60%, respectively. The limited growth and reproductionwith decreasing food clearly indicates that food availability also controls the growth and reproduction of shallow waterbenthic foraminifer C. plana. Therefore, warming coupled with decreasing productivity is likely to severely affect thegrowth and abundance of shallow water benthic foraminifera.展开更多
The spatio-temporal changes in sedimentation rate along the continental margin of the monsoon-dominated eastern Arabian Sea during the last 24 kyr have been estimated from a compilation of 58 radiocarbon dated cores, ...The spatio-temporal changes in sedimentation rate along the continental margin of the monsoon-dominated eastern Arabian Sea during the last 24 kyr have been estimated from a compilation of 58 radiocarbon dated cores, in order to understand the effect of glacial-interglacial variation on sedimentation. The sedimentation rate has been computed for four-time slices, viz. the last glacial maximum, glacial-interglacial transition, early Holocene and late Holocene. We report that the average sedimentation rate in the slope to the abyssal region of the entire eastern Arabian Sea, although higher during the Holocene as compared with that during the last glacial maximum and glacial-interglacial transition, does not significantly vary during all four-time intervals. The sedimentation rate during any particular time interval, however, varies from core to core, thus indicating zonal changes. We report four zones of relatively high sedimentation rate, viz. the northeastern Arabian Sea, the region off the Gulf of Khambhat, the region off Goa and Mangalore, and off the southern tip of India. We suggest that a complex interaction of land-ocean-atmospheric processes controlled sedimentation rate in the eastern Arabian Sea during the last 24 kyr in such a way that the average sedimentation rate does not vary significantly, even during highly contrasting climatic conditions.展开更多
Serpentinites from the inside corner high （6°38.5′S/68°19.34′E） from the Northern Central Indian Ridge （NCIR） are comprised mainly of high Mg-rich lizardite and chrysotile pseudomorphs with varying mor...Serpentinites from the inside corner high （6°38.5′S/68°19.34′E） from the Northern Central Indian Ridge （NCIR） are comprised mainly of high Mg-rich lizardite and chrysotile pseudomorphs with varying morphologies. ＇Mesh rim＇, ＇window＇, ＇hourglass＇ and ＇bastite＇ are the most common textures displayed by both chrysotile and lizardite. Numerous chrysotile veins in association with cross cutting magnetite veins indicate an advanced stage of serpentinisation. The relatively high abundance of chrysotile and lizardite suggest their close association and formation at a temperature below 250℃. Abundant ＇mesh rim＇ and ＇bastite＇ texture and variegated matrix reveal that the present serpentinites might have formed due to the interaction of harzburgite and seawater. Positive Eu anomaly （Eu/Eu^＊ up to ＋3.38）, higher La/Sm （up to 4.40） and Nb/La （up to 6.34） ratios suggest substantial hydrothermal influence during the formation of the serpentinites.展开更多
Mid-Ocean Ridge Basalts （MORB） from the Northern Central Indian Ridge （NCIR） were recovered between latitudes 3° and 11° S and are olivine tholeiite with higher abundances of K and Rb. They are of typica...Mid-Ocean Ridge Basalts （MORB） from the Northern Central Indian Ridge （NCIR） were recovered between latitudes 3° and 11° S and are olivine tholeiite with higher abundances of K and Rb. They are of typical transitional MORB （T-MORB） variety and appear to have been generated from an enriched-mantle peridotite source. The primitive NCIR MORBs having Mg^# 〉 0.68 are the product of partial melting at an estimated pressure of - 1 GPa. It is inferred that the magma was subsequently modified at a pressure 〉 1 GPa by crystal fractionation and spinel was the first mineral to crystallize followed by separation of relatively Fe-rich olivine with subsequent decrease in pressure. During progressive fractionation at lower pressure （between 1-0.5 GPa）, the bulk composition of the magma became systematically depleted in MgO, and enriched in ∑FeO, TiO2, P2Os and Na20. There was, however, limited gradual depletion in Al2O3 and CaO and concomitant enrichment in K20. With the progressive fractionation these basalts became gradually enriched in V, Co, Y, Zr and to some extent in Sr, and depleted in Ni and Cro In addition, the T_JtEE of the magma also increased with fractionation, without any change in （La/Yb）n value.展开更多
Aerosols are one of the important atmospheric constituents and exert indirect impact on climate through the modification of microphysical and radiative properties of clouds that in turn perturb the precipitation patte...Aerosols are one of the important atmospheric constituents and exert indirect impact on climate through the modification of microphysical and radiative properties of clouds that in turn perturb the precipitation pattern.Thus,the long term quantification of changes in aerosol and cloud characteristics and their interactions on both temporal as well as spatial scale will provide a crucial information for the better assessment of future climate change.In present study,18 years(2003-2020)MODerate Resolution Imaging Spectro-radiometer(MODIS)derived aerosol-cloud dataset over the Northern Indian Ocean(NIO)were analysed to assess climatology and trend of aerosol,cloud characteristics and their correlation.We found a strong heterogeneity in spatio-temporal variation of aerosol and cloud parameters over the NIO that are more prominent for the coastal region.The climatological mean of aerosol loading is found high(AOD≥0.5)over the outflow region along the Indian sub-continent and low(AOD≤0.2)over the northern equatorial open ocean.The climatological mean of cloud properties shows dominance of optically thicker deep convective(CTP<600 hPa and CTT<260 K)clouds over the southern Bay of Bengal(BoB)and thinner shallow(CTP>700 hPa and CTT>273 K)over the northwestern Arabian Sea(AS).Similarly,bigger effective radii(>17µm)observed along the equatorial open ocean whereas smaller CER(<17µm)were found over Indian sub-continental coastline and western AS.Further,trend analysis reveals an increasing pattern in AOD(0.002 yr^(-1)),CER(0.051µm yr^(-1)),LWP(0.033 gm^(-2) yr^(-1))and CF(0.002 yr^(-1))while COD,CTT and CTP show negative trend in order of-0.005 yr^(-1),-0.094 K yr^(-1) and-1.160 hPa yr^(-1),respectively.We also perform similar analysis for seven sub-region of interest(R1 to R7)across the NIO and results show a decreasing pattern in AOD(-0.001 yr^(-1))at R4 against maximum mean AOD(0.44±0.03).However,coastal sub-regions R1 and R5 illustrate maximum increase in aerosol loading(>0.003 yr^(-1))suggesting a significant impact of sub-continental outflow over the regions.The spatial correlation of cloud properties with respect to AOD shows a positive slope for CER(0.14)and CF(0.48)and a negative for COD(-0.19),LWP(-0.18),CTT(-0.37),CTP(-0.41).The present study provides in-depth information about the aerosol-cloud characteristics for a long term scale over NIO and could be useful in regional aerosol-cloud interaction induced climate forcing estimation.展开更多
基金the Department of Science and Technology,New Delhi,for the financial support to RS under the National Network Programme on Climate Change and Coastal Vulnerability(DST/CCP/NCC&CV/130/2017(G))SRK under the Women Scientist Scheme [SR/WOS-A/LS-145/2016(G)],This is a NIO contribution number 9341
文摘Anthropogenic activities are likely to cause global warming. Global warming will affect marine productivityand thus food availability for marine organisms. Both the seawater temperature and food availability affect benthicforaminifera, the most abundant marine calcareous microorganisms. Therefore, a laboratory culture experiment wasconducted on Cymbaloporetta plana to understand the coupled effect of temperature(25°C, 27°C, 30°C) and food(102±5,203±9, 305±14, 407±18, 508±23 diatom cells). At all temperatures, growth increased with increase in food. The specimenssubjected to 27°C temperature attained the maximum growth and those subjected to 25°C were the smallest. All specimensfed with 508±23 cells reproduced, 0 irrespective of temperature. Of all the specimens without food, 40% at 27°C and 20% at25°C reproduced, whereas specimens subjected to 30°C did not reproduce. The 100% rate of reproduction at 27°C suggeststhat it is the optimum temperature for growth and reproduction. All the specimens at 30°C and without additional food,died, whereas at 25°C and 27°C, the mortality rate was 80% and 60%, respectively. The limited growth and reproductionwith decreasing food clearly indicates that food availability also controls the growth and reproduction of shallow waterbenthic foraminifer C. plana. Therefore, warming coupled with decreasing productivity is likely to severely affect thegrowth and abundance of shallow water benthic foraminifera.
基金supported by the Department of Science and Technology through a FASTRACK project to RSthe Council of Scientific and Industrial Research,India by funding GEOSINKS project
文摘The spatio-temporal changes in sedimentation rate along the continental margin of the monsoon-dominated eastern Arabian Sea during the last 24 kyr have been estimated from a compilation of 58 radiocarbon dated cores, in order to understand the effect of glacial-interglacial variation on sedimentation. The sedimentation rate has been computed for four-time slices, viz. the last glacial maximum, glacial-interglacial transition, early Holocene and late Holocene. We report that the average sedimentation rate in the slope to the abyssal region of the entire eastern Arabian Sea, although higher during the Holocene as compared with that during the last glacial maximum and glacial-interglacial transition, does not significantly vary during all four-time intervals. The sedimentation rate during any particular time interval, however, varies from core to core, thus indicating zonal changes. We report four zones of relatively high sedimentation rate, viz. the northeastern Arabian Sea, the region off the Gulf of Khambhat, the region off Goa and Mangalore, and off the southern tip of India. We suggest that a complex interaction of land-ocean-atmospheric processes controlled sedimentation rate in the eastern Arabian Sea during the last 24 kyr in such a way that the average sedimentation rate does not vary significantly, even during highly contrasting climatic conditions.
基金funded by ONR grant No.0014-97-1-0925CSIR Network Programme(COR 0006)on Indian Ocean ridges
文摘Serpentinites from the inside corner high （6°38.5′S/68°19.34′E） from the Northern Central Indian Ridge （NCIR） are comprised mainly of high Mg-rich lizardite and chrysotile pseudomorphs with varying morphologies. ＇Mesh rim＇, ＇window＇, ＇hourglass＇ and ＇bastite＇ are the most common textures displayed by both chrysotile and lizardite. Numerous chrysotile veins in association with cross cutting magnetite veins indicate an advanced stage of serpentinisation. The relatively high abundance of chrysotile and lizardite suggest their close association and formation at a temperature below 250℃. Abundant ＇mesh rim＇ and ＇bastite＇ texture and variegated matrix reveal that the present serpentinites might have formed due to the interaction of harzburgite and seawater. Positive Eu anomaly （Eu/Eu^＊ up to ＋3.38）, higher La/Sm （up to 4.40） and Nb/La （up to 6.34） ratios suggest substantial hydrothermal influence during the formation of the serpentinites.
文摘Mid-Ocean Ridge Basalts （MORB） from the Northern Central Indian Ridge （NCIR） were recovered between latitudes 3° and 11° S and are olivine tholeiite with higher abundances of K and Rb. They are of typical transitional MORB （T-MORB） variety and appear to have been generated from an enriched-mantle peridotite source. The primitive NCIR MORBs having Mg^# 〉 0.68 are the product of partial melting at an estimated pressure of - 1 GPa. It is inferred that the magma was subsequently modified at a pressure 〉 1 GPa by crystal fractionation and spinel was the first mineral to crystallize followed by separation of relatively Fe-rich olivine with subsequent decrease in pressure. During progressive fractionation at lower pressure （between 1-0.5 GPa）, the bulk composition of the magma became systematically depleted in MgO, and enriched in ∑FeO, TiO2, P2Os and Na20. There was, however, limited gradual depletion in Al2O3 and CaO and concomitant enrichment in K20. With the progressive fractionation these basalts became gradually enriched in V, Co, Y, Zr and to some extent in Sr, and depleted in Ni and Cro In addition, the T_JtEE of the magma also increased with fractionation, without any change in （La/Yb）n value.
文摘Aerosols are one of the important atmospheric constituents and exert indirect impact on climate through the modification of microphysical and radiative properties of clouds that in turn perturb the precipitation pattern.Thus,the long term quantification of changes in aerosol and cloud characteristics and their interactions on both temporal as well as spatial scale will provide a crucial information for the better assessment of future climate change.In present study,18 years(2003-2020)MODerate Resolution Imaging Spectro-radiometer(MODIS)derived aerosol-cloud dataset over the Northern Indian Ocean(NIO)were analysed to assess climatology and trend of aerosol,cloud characteristics and their correlation.We found a strong heterogeneity in spatio-temporal variation of aerosol and cloud parameters over the NIO that are more prominent for the coastal region.The climatological mean of aerosol loading is found high(AOD≥0.5)over the outflow region along the Indian sub-continent and low(AOD≤0.2)over the northern equatorial open ocean.The climatological mean of cloud properties shows dominance of optically thicker deep convective(CTP<600 hPa and CTT<260 K)clouds over the southern Bay of Bengal(BoB)and thinner shallow(CTP>700 hPa and CTT>273 K)over the northwestern Arabian Sea(AS).Similarly,bigger effective radii(>17µm)observed along the equatorial open ocean whereas smaller CER(<17µm)were found over Indian sub-continental coastline and western AS.Further,trend analysis reveals an increasing pattern in AOD(0.002 yr^(-1)),CER(0.051µm yr^(-1)),LWP(0.033 gm^(-2) yr^(-1))and CF(0.002 yr^(-1))while COD,CTT and CTP show negative trend in order of-0.005 yr^(-1),-0.094 K yr^(-1) and-1.160 hPa yr^(-1),respectively.We also perform similar analysis for seven sub-region of interest(R1 to R7)across the NIO and results show a decreasing pattern in AOD(-0.001 yr^(-1))at R4 against maximum mean AOD(0.44±0.03).However,coastal sub-regions R1 and R5 illustrate maximum increase in aerosol loading(>0.003 yr^(-1))suggesting a significant impact of sub-continental outflow over the regions.The spatial correlation of cloud properties with respect to AOD shows a positive slope for CER(0.14)and CF(0.48)and a negative for COD(-0.19),LWP(-0.18),CTT(-0.37),CTP(-0.41).The present study provides in-depth information about the aerosol-cloud characteristics for a long term scale over NIO and could be useful in regional aerosol-cloud interaction induced climate forcing estimation.
