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Nuncio, M.
- Role of Westerlies and Thermohaline Characteristics on Sea-Ice Extent in the Indian Ocean Sector of Antarctica
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Authors
Affiliations
1 Polar Remote Sensing Division, National Centre for Antarctic and Ocean Research, Ministry of Earth Sciences, Headland Sada, Goa - 403 804, IN
1 Polar Remote Sensing Division, National Centre for Antarctic and Ocean Research, Ministry of Earth Sciences, Headland Sada, Goa - 403 804, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 78, No 3 (2011), Pagination: 211-216Abstract
Satellite-derived sea-ice extent in the Indian Ocean Sector during the period November 1978 to December 2006 was studied in relation to the atmospheric forcing and oceanic thermohaline structure. The study revealed that sea-ice extent increased when the ocean exhibited higher stability. Low sea-ice extent was observed during 1985 to 1993, when the zonal winds and latent flux was relatively weak and when the ocean exhibited strong vertical mixing facilitated by low stability thereby, deepening the mixed layer to ∼250 m. This was reflected in the ocean surface layer temperature, which was relatively warm (-0.3°C). Winds increased during 1996 to 2000, but due to higher oceanic stability mixed layer depth shallowed (< 200 m) leading to reduced vertical mixing of deep warmer layers with the surface water, leading to an enhancement in the sea-ice extent.Keywords
Sea Ice Extent, Indian Ocean Sector, Ocean Stability, Winds.
References
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- Seasonal Surface Chlorophyll a Variability in the Seychelles–Chagos Thermocline Ridge
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Authors
Affiliations
1 National Institute of Ocean Technology, Chennai 600 100, IN
2 National Centre for Antarctic and Ocean Research, Goa 403 804, IN
1 National Institute of Ocean Technology, Chennai 600 100, IN
2 National Centre for Antarctic and Ocean Research, Goa 403 804, IN
Source
Current Science, Vol 114, No 04 (2018), Pagination: 868-878Abstract
Seychelles–Chagos Thermocline Ridge (SCTR, 5°–10°S, 50°–75°E) in the southwestern tropical Indian Ocean is a unique area that experiences year-round upwelling. This is a response to the upward Ekman pumping prevalent in the region. Satellite data, model data and objectively analysed Argo temperature/salinity data have been used to study the seasonal surface chlorophyll a (chl a) variability in SCTR. Variability of surface chl a concentration in SCTR showed a weak semiannual signature. The western part of SCTR (WSCTR, 50°–62°E) is characterized by higher chl a concentration than the eastern part (ESCTR, 63°–75°E). Average chl a concentration in WSCTR/ESCTR showed a primary peak in July– August (~0.26/~0.16 mg/m3) and a secondary peak in January (~0.14/~0.12 mg/m3). Minimum chl a concentration (~0.12/~0.1 mg/m3) was observed during March– April and December–January. The high amplitude of chl a variability observed during July–August is associated with weak stratification and deep mixed layer depth (MLD). Deep MLD reaching to nutrient-rich thermocline entrains nutrients to the surface and thereby increases the surface chl a concentration. However, the low surface chl a concentration is a result of shallow MLD in the region. The deep MLD (30–40 m) observed during June–October is dominated by wind mixing and supported by buoyancy mixing. Shallow MLD (<30 m) observed during rest of the year is due to weak wind mixing and high surface buoyancy. The high surface buoyancy is a manifestation of ocean surface warming and presence of low saline surface waters in the SCTR region.Keywords
Buoyancy Flux, Chlorophyll a, Climatology, Wind Mixing.Full Text
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