On the diurnal ranges of Sea Surface Temperature (SST) in the north Indian Ocean

Surface seawater carbon dioxide was observed from 3 &#176;S to 27 &#176;S along 67 &#176;E of the Indian Ocean in April 2018 and 2019. Partial pressure of CO2(pCO2) in the surface seawater and the atmosphere were observed every two minutes using an underway CO2 measurement system (General Oceanics Model 8050) installed on R/V Isabu. Surface water temperature and salinity were measured as well. The pCO2 was measured using Li-7000 NDIR. Standard gases were measured every 8 hours in five classes with concentrations of 0 &#181;atm, 202 &#181;atm, 350 &#181;atm, 447 &#181;atm, and 359.87 &#181;atm. The fCO2 of atmosphere remained nearly constant at 387 &#177; 2 &#181;atm, but the surface seawater fCO2 peaked at about 3 &#176;S and tended to decrease toward the north and south. The distribution of fCO2 in surface seawater according to latitude tends to be very similar to that of sea surface temperature. In order to investigate the factors that control the distribution of fCO2 in surface seawater, we analyzed the sea surface temperature, sea surface salinity, and other factors. The effects of salinity are insignificant, and the surface fCO2 distribution is mainly controlled by sea surface temperature and other factors that can be represented mainly by biological activity and mixing.

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North Indian Ocean variability during the Indian Ocean dipole

Ocean Science Discussions ◽

10.5194/osd-5-213-2008 ◽

2008 ◽

Vol 5 (2) ◽

pp. 213-253 ◽

Cited By ~ 1

Author(s):

J. Brown ◽

C. A. Clayson ◽

L. Kantha ◽

T. Rojsiraphisal

Keyword(s):

Indian Ocean ◽

Surface Temperature ◽

Sea Surface Temperature ◽

Indian Ocean Dipole ◽

Numerical Models ◽

Circulation Model ◽

North Indian Ocean ◽

Sea Surface ◽

Large Temperature ◽

The Impact

Abstract. The circulation in the North Indian Ocean (NIO henceforth) is highly seasonally variable. Periodically reversing monsoon winds (southwesterly during summer and northeasterly during winter) give rise to seasonally reversing current systems off the coast of Somalia and India. In addition to this annual monsoon cycle, the NIO circulation varies semiannually because of equatorial currents reversing four times each year. These descriptions are typical, but how does the NIO circulation behave during anomalous years, during an Indian Ocean dipole (IOD) for instance? Unfortunately, in situ observational data are rather sparse and reliance has to be placed on numerical models to understand this variability. In this paper, we estimate the surface current variability from a 12-year hindcast of the NIO for 1993–2004 using a 1/2° resolution circulation model that assimilates both altimetric sea surface height anomalies and sea surface temperature. Presented in this paper is an examination of surface currents in the NIO basin during the IOD. During the non-IOD period of 2000–2004, the typical equatorial circulation of the NIO reverses four times each year and transports water across the basin preventing a large sea surface temperature difference between the western and eastern NIO. Conversely, IOD years are noted for strong easterly and westerly wind outbursts along the equator. The impact of these outbursts on the NIO circulation is to reverse the direction of the currents – when compared to non-IOD years – during the summer for negative IOD events (1996 and 1998) and during the fall for positive IOD events (1994 and 1997). This reversal of current direction leads to large temperature differences between the western and eastern NIO.

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