Global Ocean Currents explain why Northern Hemisphere is the soggier one - Essay Example

Global Ocean Currents and the Northern Hemisphere GLOBAL OCEAN CURRENTS AND THE NORTHERN HEMISPHERE According to the article, Global Ocean Currents Explain why the Northern Hemisphere is the Soggier One, most of the world’s rainfall is centred on the Northern Hemisphere (Hickey, 2013). This, the article contends, is evidenced by looking at a precipitation map for the world. Citing Frierson et al. (2013), the article contends that this pattern arises from global ocean currents that come from the Polar Regions that are far away.

There are intense rainfall regions in narrow bands within the deep tropics across the globe, which can be found closely located around arid regions that have scarce rainfall. This zone is referred to as the zone of inter-tropical convergence, and it is neither symmetric nor centred around the equator. Rather, it is to be found over the oceans in the northern tropical regions. Frierson et al. used observational data and model simulations to show overturning circulation in the oceans, as well as associated energy transports, and their importance in boreal disposition of rainfall (Hickey, 2013).

Hemispheric asymmetry in the ITCZ is caused by the influence of tropical landmasses and their associated cloud fields, and atmospheric circulation on ocean currents and temperatures (Frierson et al, 2013). On average, the Southern hemisphere absorbs more energy than the Northern hemisphere from the atmosphere. The energetic imbalance that results between the two hemispheres is redressed by meridional overturning circulation of the ocean, which transports heat from the Southern Hemisphere northwards towards the equator to be released as atmospheric heat.

The ITCZ is sensitive to heat redistribution through the meridional overturning circulation. Generally, in the tropics, energy at the surface is absorbed by the oceans and released into the extra-tropical regions. When these perturbations to the mean state are explored using a model, which removes the effects of continental landmasses, hemispheric asymmetry can also be induced within the ITCZ (Frierson et al, 2013). This hypothesis that ITCZ asymmetry is determined by meridional overturning circulation can also be tested by imposing, between the extra-tropics and tropics on the two hemispheres, a symmetrical flux of surface heat.

The results show that, within the extra-tropics, differences in hemispheric atmosphere-ocean flux of heat related to meridional overturning circulation are a necessity for asymmetry of ITCZ (Pike, 2013). It is still important to note that surface heat flux present in hemispheric imbalance is a result of continental geometry that has a significant influence on ocean and atmosphere circulations. However, emphasis on energetics instead of landmass location gives further insight into this process, which could dictate alterations in tropical rainfall distribution.

Inter-hemispheric contrasts in abundance of aerosols could be a modulator of rainfall in the immediate vicinity, as well as through tropics, via modulation of the radiative budget of the surface. As India, China, and other boreal economies transition to environmental standards of the first world, there will be substantial implications for aerosols, as well as for tropical rainfall patterns (Strahler, 2013). Particularly, aerosol level reductions could cause an increase in sunlight amounts reaching the Northern Hemisphere, which could reduce ITCZ asymmetry and hemispheric heat contrast.

The article shows that ocean heat redistribution via the action of meridional overturning circulation could be responsible for asymmetry in the amount of hemispheric tropical rainfall. The findings offer a challenge to the idea that asymmetry in the inter-tropical convergence zone is fixed geographically. Incremental improvements in how man comprehends these processes and their impact on future spatial alterations of rainfall could be crucial in adapting successfully to the changes in climate.

ReferencesFrierson, D. M., Hwang, Y. T., Fuckar, N. S., Seager, R., Kang, S. M., Donohoe, A., Maroon, E. A., & Battisti, D. S. (January 01, 2013). Contribution of ocean overturning circulation to tropical rainfall peak in the Northern Hemisphere. Nature Geoscience, 6, 11, 940-944. Hickey, H. (2013, October 20). Global ocean currents explain why Northern Hemisphere is the soggier one. Retrieved March 6, 2014, from Science Daily: http://www.sciencedaily.com/releases/2013/10/131020160652.htm Pike, A. C. (2013).

The inter-tropical convergence zone studied with an interacting atmosphere and ocean model. Ft. Belvoir: Defense Technical Information Center. Strahler, A. H. (2013). Introducing physical geography. Hoboken, N.J.: Wiley