Observed oceanic response to tropical cyclone Jal from a moored buoy in the south-western Bay of Bengal

Girishkumar, M. S.; Suprit, K.; Jayaram, Chiranjivi; Bhaskar, T. V. S. Udaya; Ravichandran, M.; Shesu, R. Venkat; Rao, E. Pattabhi Rama

doi:10.1007/s10236-014-0689-6

Cited by 52 publications

(22 citation statements)

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“…The surface mixed layer depth (MLD) and the Ekman pumping velocity (EPV) are used in this study to estimate the storm‐induced vertical mixing and upwelling (or downwelling) during the passage of the TC. The MLD is defined as the depth at which the potential density is 0.125 kg/m 3 higher than the surface potential density (Girishkumar et al, ; Levitus, ). The ILD, the depth of the top of the thermocline, is defined as the depth at which the water temperature is cooler by 1 °C than the SST (Rao & Sivakumar, ).…”

Section: Methodsmentioning

confidence: 99%

Examining the Impact of Tropical Cyclones on Air‐Sea CO₂ Exchanges in the Bay of Bengal Based on Satellite Data and In Situ Observations

Jiang

Tang

et al. 2019

JGR Oceans

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The impact of tropical cyclones (TCs) on the CO 2 partial pressure at the sea surface (pCO 2sea ) and air-sea CO 2 flux (F CO2 ) in the Bay of Bengal (BoB) was quantified based on satellite data and in situ observations between November 2013 and January 2017. The in situ observations were made at the BoB Ocean Acidification mooring buoy. A weak time-mean net source of 55.78 ± 11.16 mmol CO 2 m À2 year À1 at the BoB Ocean Acidification site was estimated during this period. A wide range in increases of pCO 2sea (1.0-14.8 μatm) induced by TCs occurred in postmonsoon (October-December), and large decreases of pCO 2sea (À14.0 μatm) occurred in premonsoon (March-May). Large vertical differences in the ratio of dissolved inorganic carbon (DIC) to total alkalinity (TA) in the upper layer (ΔDIC/TA) were responsible for increasing pCO 2sea in postmonsoon. Relatively small values of ΔDIC/TA were responsible for decreasing pCO 2sea in premonsoon. Five TCs (Hudhud, Five, Kyant, Vardah, and Roanu) were considered. Hudhud significantly enhanced CO 2 efflux (18.49 ± 3.70 mmol CO 2 /m 2 ) in oversaturated areas due to the wind effect during the storm and wind-pump effects after the storm. Vardah insignificantly changed F CO2 (1.22 ± 0.24 mmol CO 2 /m 2 ) in undersaturated areas because of the counteraction of these two effects. Roanu significantly enhanced CO 2 efflux (19.08 ± 3.82 mmol CO 2 /m 2 ) in highly oversaturated conditions (ΔpCO 2 > 20 μatm) since the wind effect greatly exceeded the wind-pump effects. These five TCs were estimated to account for 55 ± 23% of the annual-mean CO 2 annual efflux, suggesting that TCs have significant impacts on the carbon cycle in the BoB.Plain Language Summary We examined the impact by five tropical cyclones on the sea surface pCO 2 and air-sea CO 2 exchange using Bay of Bengal Ocean Acidification moored buoy measurements over the Bay of Bengal. To our knowledge, this is the first study on the different effects of tropical cyclones and vertical differences in the ratio of dissolved inorganic carbon to total alkalinity in the upper layer on the sea surface pCO 2 and local air-sea CO 2 flux.

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Section: Methodsmentioning

confidence: 99%

Examining the Impact of Tropical Cyclones on Air‐Sea CO₂ Exchanges in the Bay of Bengal Based on Satellite Data and In Situ Observations

Jiang

Tang

et al. 2019

JGR Oceans

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“…Earlier studies have shown that the vertical processes, such as upwelling and entrainment due to wind‐induced vertical mixing and convective overturning due to the net surface heat flux loss from the ocean are responsible for 70–80% of SST cooling along the track of TC as compared with the lesser contribution from horizontal advection and enthalpy flux (~20–30%; Girishkumar et al, ; Price, ; Vincent, Lengaigne, Madec, et al, ; Vincent, Lengaigne, Vialard, et al, ). Consistent with these earlier results, net surface heat loss from the ocean and horizontal advection played a weaker role on the observed SST cooling at C‐Float location during TC Hudhud and TC Vardah (Figure S6; see supporting information S5 for the relative role of horizontal advection and net surface heat flux on the observed SST cooling during TC period).…”

Section: Resultsmentioning

confidence: 99%

“…Earlier studies have shown the presence of strong near‐inertial oscillations of upwelling and downwelling after the passage of TCs (Park et al, ; Price, ; Sanford et al, ; Wang et al, ; Zhang et al, ). The near‐inertial oscillation of upwelling can facilitate entrainment of cold thermocline water to the surface mixed layer (Sanford et al, ; Girishkumar et al, ; Zhang et al, ). At 14°N (near to the C‐Float location in the BoB), the theoretical inertial period is around 50 hr (~2 days).…”

Section: Resultsmentioning

confidence: 99%

Quantifying Tropical Cyclone's Effect on the Biogeochemical Processes Using Profiling Float Observations in the Bay of Bengal

et al. 2019

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Physical and biogeochemical observations from an autonomous profiling Argo float in the Bay of Bengal show significant changes in upper ocean structure during the passage of tropical cyclone (TC) Hudhud (7–14 October 2014). TC Hudhud mixed water from a depth of about 50 m into the surface layers through a combination of upwelling and turbulent mixing. Mixing was extended into the depth of nutricline, the oxycline, and the subsurface‐chlorophyll‐maximum and thus had a strong impact on the biogeochemistry of the upper ocean. Before the storm, the near‐surface layer was nutrient depleted and was thus oligotrophic with the chlorophyll‐a concentration of less than 0.15 mg/m3. Storm mixing initially increased the chlorophyll by 1.4 mg/m3, increased the surface nitrate concentration to about 6.6 μM/kg, and decreased the subsurface dissolved oxygen (30–35 m) to 31% of saturation (140 μM). These conditions were favorable for phytoplankton growth resulting in an estimated increase in primary productivity averaging 1.5 g C·m−2·day−1 over 15 days. During this bloom, chlorophyll‐a increased by 3.6 mg/m3, and dissolved oxygen increased from 111% to 123% of saturation. Similar observations during TC Vardah (6–12 December 2016) showed much less mixing. Our analysis suggests that relatively small (high) translation speed and the presence of cold (warm) core eddy leads to strong (weak) oceanic response during TC Hudhud (TC Vardah). Thus, although cyclones can cause strong biogeochemical responses in the Bay of Bengal, the strength of response depends on the properties of the storm and the prevailing upper ocean structure such as the presence of mesoscale eddies.

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“…Several researchers explored TC‐induced oceanic responses through detailed case studies carried out on BoB TCs, namely, Sidr, Phailin, Nargis, Laila, Mala, and Jal, using both models (Prakash & Pant, ; Qiu et al, ; Vissa et al, ) and observations (Chaudhuri et al, ; Girishkumar et al, ; Maneesha et al, ; Vissa et al, ). The significant responses to TCs such as a decrease in sea surface temperature (SST), increase in salinity, mixed layer deepening, thermocline shoaling, enhanced heat loss to the atmosphere, and increase in chlorophyll‐a concentration are well documented (Price, ; Krishna et al, ; Sengupta et al, ; Vinayachandran & Mathew, ).…”

Section: Introductionmentioning

confidence: 99%

“…The significant responses to TCs such as a decrease in sea surface temperature (SST), increase in salinity, mixed layer deepening, thermocline shoaling, enhanced heat loss to the atmosphere, and increase in chlorophyll‐a concentration are well documented (Price, ; Krishna et al, ; Sengupta et al, ; Vinayachandran & Mathew, ). Several researchers have also analyzed the mixed layer heat budget to quantify the relative role of various processes in governing the TC‐induced thermal responses (Girishkumar et al, ; Prakash & Pant, ; Price, ). Jullien et al () reported the dominance of vertical mixing in the surface and upwelling mechanism in the subsurface to the rate of change in temperature in the ocean.…”

Section: Introductionmentioning

confidence: 99%

Surface and Sub‐surface Ocean Response to Tropical Cyclone Phailin: Role of Pre‐existing Oceanic Features

2019

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The upper oceanic thermal response induced by Tropical Cyclone Phailin (9-14 October 2013) under the influence of East India Coastal Current (EICC) and a cyclonic eddy is investigated and contrasted with the response from open ocean region using a high-resolution HYbrid Coordinate Ocean Model simulation. There is significant cooling (7 • C) inside the cold core eddy and negligible cooling (0.5 • C) within the EICC region characterized by the shallow and deeper thermocline, respectively. Our analysis of mixed layer heat budget terms showed that the horizontal advection plays a significant role in determining the temperature tendency for the location within the EICC, in contrary to the general dominance of vertical processes as reported in previous studies during the cyclone period. The analysis for the locations inside eddy and open ocean concurs with the previous studies showing the dominance of vertical processes toward the temperature tendency. Further, near the coast, the surface cooling is minimal compared to the subsurface cooling, dominantly seen between 50-and 100-m depth. This disparity indicates that the factors responsible for the surface temperature anomalies are different from those of subsurface. Our analysis of thermal signatures after the passage of cyclone showed that the EICC and cyclonic eddy contribute to the faster advection of cold wake and recovery of sea surface temperature to the prestorm state.

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Observed oceanic response to tropical cyclone Jal from a moored buoy in the south-western Bay of Bengal

Cited by 52 publications

References 58 publications

Examining the Impact of Tropical Cyclones on Air‐Sea CO₂ Exchanges in the Bay of Bengal Based on Satellite Data and In Situ Observations

Examining the Impact of Tropical Cyclones on Air‐Sea CO₂ Exchanges in the Bay of Bengal Based on Satellite Data and In Situ Observations

Quantifying Tropical Cyclone's Effect on the Biogeochemical Processes Using Profiling Float Observations in the Bay of Bengal

Surface and Sub‐surface Ocean Response to Tropical Cyclone Phailin: Role of Pre‐existing Oceanic Features

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Observed oceanic response to tropical cyclone Jal from a moored buoy in the south-western Bay of Bengal

Cited by 52 publications

References 58 publications

Examining the Impact of Tropical Cyclones on Air‐Sea CO2 Exchanges in the Bay of Bengal Based on Satellite Data and In Situ Observations

Examining the Impact of Tropical Cyclones on Air‐Sea CO2 Exchanges in the Bay of Bengal Based on Satellite Data and In Situ Observations

Quantifying Tropical Cyclone's Effect on the Biogeochemical Processes Using Profiling Float Observations in the Bay of Bengal

Surface and Sub‐surface Ocean Response to Tropical Cyclone Phailin: Role of Pre‐existing Oceanic Features

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Examining the Impact of Tropical Cyclones on Air‐Sea CO₂ Exchanges in the Bay of Bengal Based on Satellite Data and In Situ Observations

Examining the Impact of Tropical Cyclones on Air‐Sea CO₂ Exchanges in the Bay of Bengal Based on Satellite Data and In Situ Observations