[Climate change impacts on north-western Indian Ocean and Arabian Sea circulation]

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Table of Contents

CHAPTER 2: LITERATURE REVIEW5

Scientific Background of NWIO and AS Hydrometeorology5

Monsoon Related Phenomena13

Somali Current and Upwelling15

Great Whirl Gyre and Socotra Eddie22

Arabian Sea Circulation28

REFERENCES31

Chapter 2: Literature Review

Scientific Background of NWIO and AS Hydrometeorology

There is several fold increase in the atmospheric contents of greenhouse gases (GHGs) due to rapid industrialization. For instance, CO2 content has enhanced from preindustrial value of about 280 ppm to 379 ppm in 2005 whereas concentration of CH4 has elevated from 715 ppb to 1774 ppb during the same period. The higher contents of GHGs bring a change in the radiative balance of the earth resulting into climate change in terms of increase in temperature, change in precipitation pattern and probably a rise in the frequencies of extreme events. The unprecedented warming in the past two decades of twentieth century, especially during the period spanned over 1995-2006, is believed to be due to the anthropogenic forcing of climate.

Meteorological data of the previous century also suggest a global mean temperature rise of 0.07°C per decade. Globally observed annual precipitation has reportedly increased ~ 0.98 % per decade in the twentieth century. The intensity of extreme events has also increased worldwide in this century. The global mean sea level has risen by 10 to 20 cm. There has been a 40 % decline in Artic Sea ice thickness in late summer to early autumn in the past 50 years. The frequency of severe floods in large river basins has increased during the 20th century. The average annual discharge of fresh water from six of the largest Eurasian rivers has increased by 7 % from 1936 to 1999. Hence, majority of the scientific community now believes that climate change is certain. This chapter reviews the pertinent literature, including topics like hydro climatic changes in present and future climate, developments in the evaluation of global climate models, methods to downscale GCM data and ways to use climate change scenarios in water resource impact studies (Keen, 1997, 90).

The average global surface temperature is projected to increase by 1.4-3 C from 1990 to 2100 for low emission scenarios and 2.5-5.8 C for higher emission scenarios of GHGs in the atmosphere. It is argued that warming escalates the moisture holding capacity of the atmosphere alters the hydrological cycle and changes the characteristics of precipitation. Changes in the precipitation may however have a greater impact on human well being and ecosystem dynamics than the temperature because precipitation controls the volume of runoff whereas changes in temperature mostly ...