Humans are abusing oceans, leading to fast deterioration of ocean health. Ocean scientists have diagnosed the symptoms of an ailing ocean. Safety precautions need to be in place before the oceans lose their resilience to a point of no return. Dr V N Sanjeevan, former Director of Centre for Marine Living Resources and Ecology, Ministry of Earth Sciences gives an in-depth analysis of the peculiar phenomenon.
Life originated in oceans. Life on planet Earth, to a large extent, is sustained by the oceans. Mother Ocean provides us with water to drink, oxygen to breathe, quality proteins for growth, and it is a storehouse of drugs for most ailments. Yet we continue abusing her to the extent that ocean health is fast deteriorating.
Ocean & Earth System
Planet Earth appear blue from space, epitomising the importance of oceans, which occupy 71% of the Earth’s surface. The Earth System components hydrosphere, atmosphere, cryosphere and biosphere are intrinsically coupled systems, and, therefore, disturbance to any one component is bound to alter the functioning of other system components. The Earth System processes are driven on solar energy, including the processes that keep the Earth warm, which, otherwise, would have been a frozen planet, all dynamical processes associated with the oceans, atmosphere and cryosphere, and production and transfer of energy through the biosphere.
Nature maintains a delicate balance over its system components and energy budget through self-adjustments. The overriding anthropogenic interventions on nature quite often upset this natural rhythm, inviting furious response from Mother Earth manifested in the form of cyclones, storm surges, tsunamis, global warming, etc, which are a gentle reminder not to trespass nature’s Laxman Rekha. Such expressions of nature are at present beyond human comprehension. The challenge is to develop robust Earth System Models that could capture and simulate earth system functions with a view to identifying the root cause of such events and develop foolproof response strategies, including reliable safety precautions.
The oceans of the world, namely, the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Southern Ocean and the Arctic Ocean are linked by a deep thermohaline circulation – or the global ocean conveyer belt – which help distribute heat energy across the world. Excess heat generated in the tropical seas is transported by the conveyer belt to the frozen Polar Regions, where the water sinks to the deep bottom to surface again in the subtropical/tropical belt, its full cycle taking about y 1,000 years to complete. Further, this circulation ventilates the world oceans, thereby ensuring the availability of dissolved oxygen at all depths, a crucial factor in maintaining the overall health of the oceans. An exception to this is the Northern Indian Ocean, which is landlocked north of the Arabian Sea and the Bay of Bengal.
The conveyer belt deviates close to the equator, making the interior of the North Indian Ocean, especially the Arabian Sea, oxygen-deficient. The Arabian Sea has the world’s largest dead zone (DO 2 < 0.2ml/ L) or Oxygen Minimum Zone (OMZ). Global warming – accelerated by humans through indiscriminate emissions of greenhouse gases to the atmosphere – is steadily heating the Earth and the ocean surface. The surplus heat from the equator is transported by the conveyer belt to the poles, where it accelerates the melting of polar icecaps, leading to further slowdown in the speed
of the thermohaline circulation.
(Read more from the September Issue of Safety Messenger Magazine 2015)