Aerosol size distributions in the north and south Indian ocean during the northeast monsoon season

2002 ◽  
Vol 65 (1-2) ◽  
pp. 51-76 ◽  
Author(s):  
C.G Deshpande ◽  
A.K Kamra
Keyword(s):  
Indian Ocean ◽  
Monsoon Season ◽  
Northeast Monsoon ◽  
Size Distributions ◽  
South Indian Ocean ◽  
The North ◽  
South Indian ◽  
North And South

The phosphate levels of the major surface currents of the Indian Ocean

1967 ◽  
Vol 18 (1) ◽  
pp. 1 ◽  
Author(s):  
DJ Rochford
Keyword(s):  
Indian Ocean ◽  
High Salinity ◽  
Average Rate ◽  
North Indian Ocean ◽  
Surface Currents ◽  
The South ◽  
South Indian Ocean ◽  
The North ◽  
South Indian ◽  
South West Monsoon

The principal surface currents of the north Indian Ocean are much richer in phosphate (greater than 0.25 �g-atom/l) than those of the south Indian Ocean (less than 0.15 �g-atom/I). In summer large areas of the surface waters of the south-east Indian Ocean have a very low phosphate content (less than 0.10 �g-atom/l). These waters are by far the lowest in phosphate of the whole Indian Ocean. Their salinity-temperature- phosphate relations show that waters from two regions, the South Equatorial Current in the north and the high salinity belt around 30-35� S., contribute to their formation. Waters of this high salinity belt are carried northward into the low phosphate region by the West Australian Current in summer. These high-salinity waters most probably form by evaporation of an upper 50-m mixed layer of waters of the south-east Atlantic drifting eastward in the south Indian Ocean at an average rate of 15 cm per sec. In the eastern Indian Ocean north of 10�S., surface phosphate levels in summer are governed by the circulation of the richer phosphate waters of the counter current. In winter the circulation of richer phosphate waters of the South-west Monsoon Current governs the phosphate level.

scholarly journals Recent emergence of CAT5 tropical cyclones in the South Indian Ocean

2018 ◽  
Vol 114 (11/12) ◽  
Author(s):  
Jennifer M. Fitchett
Keyword(s):  
Tropical Cyclone ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
Satellite Imagery ◽  
Storm Damage ◽  
The South ◽  
South Indian Ocean ◽  
The North ◽  
South Indian ◽  
Recent Emergence

The IBTrACS global best track data set endorsed by the World Meteorological Organization provides a valuable global record of tropical cyclone genesis, track and intensity, and spans 1842 to the present. The record is significantly more robust from the late 1970s onwards, as it is supported by satellite imagery. These records indicate that the first tropical cyclone in the South Indian Ocean to intensify to CAT5 status did so in 1994. This date is significantly later than the first CAT5 storms recorded in the IBTrACS database for the Atlantic Ocean (1924) and the North Pacific (1951) recorded from ship records, and half a decade later than those of the North Indian Ocean (1989) and South Pacific (1988), captured from satellite imagery. Following this late emergence, in the period 1990–2000, eight CAT5 tropical cyclones were recorded for the South Indian Ocean. A further four have been recorded for the period 2010–2015. This recent emergence of tropical cyclones attaining category five intensity in the South Indian Ocean is of significance for the forecasting of tropical cyclone landfall and the anticipation of storm damage for the developing economies that characterise the region. Although an increase in tropical cyclone intensity is frequently projected under global climate change scenarios, the dynamics for the South Indian Ocean have remained poorly understood. Notable are early results indicating an increased frequency and poleward migration of these CAT5 storms, concurrent with a poleward migration in the position of the 26.5 °C, 28 °C and 29 °C sea surface temperature isotherms in the South Indian Ocean. Significance: Category 5 tropical cyclones, the strongest category of storms, have only recently emerged in the South Indian Ocean. Since 1989, their frequency of occurrence has increased. This increase poses a heightened risk of storm damage for the South Indian Ocean Island States and the countries of the southern African subcontinent as a result of the strong winds, heavy rainfall and storm surges associated with these storms, and the large radial extent at category 5 strength.

scholarly journals On the Leeuwin Current System and Its Linkage to Zonal Flows in the South Indian Ocean as Inferred from a Gridded Hydrography

2017 ◽  
Vol 47 (3) ◽  
pp. 583-602 ◽  
Author(s):  
Ryo Furue ◽  
Kévin Guerreiro ◽  
Helen E. Phillips ◽  
Julian P. McCreary ◽  
Nathaniel L. Bindoff
Keyword(s):  
Indian Ocean ◽  
Current System ◽  
The South ◽  
South Indian Ocean ◽  
Zonal Flows ◽  
Leeuwin Current ◽  
The North ◽  
South Indian ◽  
The Tropics ◽  
First Time

AbstractThe Leeuwin Current System (LCS) along the coast of Western Australia consists of the poleward-flowing Leeuwin Current (LC), the equatorward-flowing Leeuwin Undercurrent (LUC), and neighboring flows in the south Indian Ocean (SIO). Using geostrophic currents obtained from a highly resolved (⅛°) hydrographic climatology [CSIRO Atlas of Regional Seas (CARS)], this study describes the spatial structure and annual variability of the LC, LUC, and SIO zonal currents, estimates their transports, and identifies linkages among them. In CARS, the LC is supplied partly by water from the tropics (an annual mean of 0.3 Sv; 1 Sv ≡ 106 m3 s−1) but mostly by shallow (200 m) eastward flows in the SIO (4.7 Sv), and it loses water by downwelling across the bottom of this layer (3.4 Sv). The downwelling is so strong that, despite the large SIO inflow, the horizontal transport of the LC does not much increase to the south (from 0.3 Sv at 22°S to 1.5 Sv at 34°S). This LC transport is significantly smaller than previously reported. The LUC is supplied by water from south of Australia (0.2 Sv), by eastward inflow from the SIO south of 28°S (1.6 Sv), and by the downwelling from the LC (1.6 Sv) and in response strengthens northward, reaching a maximum near 28°S (3.4 Sv). North of 28°S it loses water by outflow into subsurface westward flow (−3.6 Sv between 28° and 22°S) and despite an additional downwelling from the LC (1.9 Sv), it decreases to the north (1.7 Sv at 22°S). The seasonality of the LUC is described for the first time.

ABSTRACT

2008 ◽  
Vol 89 (7s) ◽  
pp. 10-179 ◽  
Author(s):  
D. H. Levinson ◽  
J. H. Lawrimore
Keyword(s):  
Indian Ocean ◽  
Greenland Ice Sheet ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
South Indian Ocean ◽  
Continental Scale ◽  
The North ◽  
South Indian ◽  
The Antarctic ◽  
Global Mean

The combined land and ocean surface temperature in 2007 fell within the 10 highest on record, while the average land temperature was the warmest since global records began in 1880. In the low to midtroposphere, the annual global mean temperature was among the five warmest since reliable global records began in 1958, but still cooler than the record warmest year of 1998. For the fourth consecutive year, the annual precipitation averaged over global land surfaces was above the long-term mean, although the anomaly was significantly less than in 2006 when the annual value was the eighth wettest since 1901. The globally averaged concentration of carbon dioxide (CO2) continued to increase in 2007, having risen to 382.7 ppm at the Mauna Loa Observatory in Hawaii. The average rate of rise of CO2 has been 1.6 ppm yr−1 since 1980; however, since 2000 this has increased to 1.9 ppm yr−1. In addition, both methane (CH4) and carbon monoxide (CO) concentrations were also higher in 2007. Over the oceans, global SST during 2007 showed significant departures from the 1971–2000 climatology. Annual average upper-ocean heat content anomalies declined between 2006 and 2007 in the eastern equatorial Pacific and increased in off-equatorial bands in that ocean basin. These changes were consistent with the transition from an El Niño in 2006 to a La Niña in 2007. The global mean sea level anomaly (SLA) in 2007 was I.I mm higher than in 2006, which is about one standard deviation below what would be expected from the 15-yr trend value of 3.4 mm yr−1. In the tropics, the Atlantic hurricane season was near normal in 2007, although slightly more active than in 2006. In the north and south Indian Ocean Basins, both the seasonal totals and intensity of tropical cyclones (TC) were significantly above average, and included two Saffir-Simpson category 5 TCs in the north Indian Ocean and a world record rainfall amount of 5510 mm over a 3–8-day period on the island of Reunion in the south Indian Ocean. In the polar regions 2007 was the warmest on record for the Arctic, and continued a general, Arctic-wide warming trend that began in the mid-1960s. An unusually strong high pressure region in the Beaufort Sea during summer contributed to a record minimum Arctic sea ice cover in September. Measurements of the mass balance of glaciers and ice caps indicate that in most of the world, glaciers are shrinking in mass. The Greenland ice sheet experienced records in both the duration and extent of the summer surface melt. From the continental scale, as a whole the Antarctic was warmer than average in 2007, although the Antarctic Peninsula was considerably cooler than average. The size of the ozone hole was below the record levels of 2006, and near the average of the past 15 yr, due to warmer springtime temperatures in the Antarctic stratosphere.

scholarly journals Variability in the Mozambique Channel Trough and Impacts on Southeast African Rainfall

2020 ◽  
Vol 33 (2) ◽  
pp. 749-765 ◽  
Author(s):  
Rondrotiana Barimalala ◽  
Ross C. Blamey ◽  
Fabien Desbiolles ◽  
Chris J. C. Reason
Keyword(s):  
Indian Ocean ◽  
Austral Summer ◽  
Western Indian Ocean ◽  
Strong Relationship ◽  
Ocean Basin ◽  
Moist Convection ◽  
South Indian Ocean ◽  
Mozambique Channel ◽  
Mascarene High ◽  
South Indian

AbstractThe Mozambique Channel trough (MCT) is a cyclonic region prominent in austral summer in the central and southern Mozambique Channel. It first becomes evident in December with a peak in strength in February when the Mozambique Channel is warmest and the Mascarene high (MH) is located farthest southeast in the Indian Ocean basin. The strength and the timing of the mean MCT are linked to that of the cross-equatorial northeasterly monsoon in the tropical western Indian Ocean, which curves as northwesterlies toward northern Madagascar. The interannual variability in the MCT is associated with moist convection over the Mozambique Channel and is modulated by the location of the warm sea surface temperatures in the south Indian Ocean. Variability of the MCT shows a strong relationship with the equatorial westerlies north of Madagascar and the latitudinal extension of the MH. Summers with strong MCT activity are characterized by a prominent cyclonic circulation over the Mozambique Channel, extending to the midlatitudes. These are favorable for the development of tropical–extratropical cloud bands over the southwestern Indian Ocean and trigger an increase in rainfall over the ocean but a decrease over the southern African mainland. Most years with a weak MCT are associated with strong positive south Indian Ocean subtropical dipole events, during which the subcontinent tends to receive more rainfall whereas Madagascar and northern Mozambique are anomalously dry.

scholarly journals Structure and origin of the subtropical South Indian Ocean Countercurrent

2006 ◽  
Vol 33 (24) ◽  
Author(s):  
Gerold Siedler ◽  
Mathieu Rouault ◽  
Johann R. E. Lutjeharms
Keyword(s):  
Indian Ocean ◽  
South Indian Ocean ◽  
South Indian

Sea surface temperatures, salinity and pH reconstructions over the last 1,2 Ma in South Indian Ocean using the unique combination of Mg/Ca, d18O and ∆47 in planktonic foraminifera

2021 ◽  
Author(s):  
Marion Peral ◽  
Thibaut Caley ◽  
Bruno Malaizé ◽  
Erin McClymont ◽  
Thomas Extier ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Transfer Function ◽  
Planktonic Foraminifera ◽  
The Other ◽  
Unique Combination ◽  
South Indian Ocean ◽  
Term Evolution ◽  
South Indian ◽  
Clumped Isotope

<p>The Mid-Pleistocene transition (MPT) took place between 1,200 Ma and 800 ka (still debated). During this transition, the Earth’s orbitally paced ice age cycles intensified, lengthened from ∼40 000 (∼40 ky) to ∼100 ky, and became distinctly asymmetrical while Earth’s orbital variations remained unchanged. Although orbital variations constitute the first order forcing on glacial-interglacial oscillations of the late Quaternary, they cannot explain alone the shifts in climatic periodicity and amplitude observed during the MPT. In order to explain the MPT, long-term evolution of internal mechanisms and feedbacks have been called upon, in relation with the global cooling trend initiated during the Cenozoic, the expansion of Antarctic and Greenland Ice Sheet and/or the long-term decline in greenhouse gases (particularly CO2). A key point is therefore to accurately reconstruction of oceanic temperatures to decipher the processes driving climate variations.</p><p>In the present work, we studied the marine sediment core MD96-2048 taken from south Indian Ocean (26*10’482’’ S, 34*01’148’’ E) in the region of the Agulhas current. We compared 5 paleothermometers: alkenone, TEX86, foraminiferal- transfer function, Mg/Ca and clumped isotope. Among these approaches, carbonate clumped-isotope thermometry (∆<sub>47</sub>) only depends on crystallization temperature, and the ∆<sub>47</sub> relationship with planktonic foraminifer calcification temperature is well defined. Since Mg/Ca is not only controlled by temperature but is also affected by salinity and pH. The classical d<sup>18</sup>O in planktic is dependent on SST and d<sup>18</sup>Osw, which is regionally correlated with the salinity in the present-day ocean. Assuming that the present-day d<sup>18</sup>O<sub>sw</sub>-salinity relation was the same during the MPT, we are able to separate changes in d<sup>18</sup>O<sub>sw</sub> from temperature effects and reconstruct past salinity. Combining d<sup>18</sup>O, Mg/Ca and ∆<sub>47</sub> on planktonic foraminifera allow in theory to reconstruct SST, SSS and pH.</p><p>Here, we measured d<sup>18</sup>O, Mg/Ca and ∆<sub>47</sub> on the shallow-dwelling planktonic species Globigerinioides ruber ss. at the maximal of glacial and interglacial periods over the last 1.2 Ma. Our set of data makes it possible to estimate the long-term evolution of SST, salinity and pH (and thus have an insight into the atmospheric CO<sub>2</sub> concentration) across the MPT. Frist, strong differences are observed between the 5 derived-SST: the alkenone and TEX86 recorded the higher temperatures than the other SST proxies. Alkenone derived-SST do not show glacial-interglacial variations within the MPT. The Mg/Ca and transfer function derived-SST show a good agreement each other, while the clumped-isotope derived-SST are systematically colder than the other derived-SST. Then, our ∆<sub>47</sub>-SST, salinity and pH results clearly show that amplitude of glacial-interglacial variations was insignificant between 1.2 and 0.8 Ma (within the MPT) and increased after the MPT. Finally, we also discussed the potential to use this unique combination of proxies to reconstruct changes of atmospheric CO<sub>2</sub> concentration.</p>

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