Oceans and Seas
Pp. 129-139 (11)
The surface waters of oceans and seas have been exposed long-term to
multiple anthropogenic contaminations, waste heat, and heat transfer from the warming
atmosphere. Absorption of ca. 170 GT CO2 since the beginning of industrialisation has
caused on average a reduction of pH by 0.1. Between 1871 and 2005, heat transfer
from the atmosphere has resulted in surface water warming of tropical seas by 0.5 °C.
Fluvial input of reactive N and P from urban areas and agricultural land has caused
partial deoxygenation of the sea waters. In poorly ventilated areas like the Baltic Sea
and Gulf of Bengal, hypoxic and anoxic zones developed. Anoxic zones in eddies,
observed in the eastern South Atlantic, alter microbial communities and, therefore,
primary productivity. Decrease in Atlantic Meridional Overturning Circulation
(AMOC) has occurred because of the intensified input of Arctic glacial meltwater,
resulting in less storage of atmospheric CO2 in deeper sea water layers. Average Hgconcentration
in the upper seawater layer increased from 0.75 pM to 1.45 pM between
1850 and 2008. Offshore hydrocarbon development, including havaries and oil spills
impaired sea water quality. Littering of the seas with plastic particles has occurred
since ca. 70 years ago and amounted 2010 to 8-10 MT/a. The fragments act as transport
vehicles for pathogens and organotoxins. Radioactive waste was disposed of between
1946 and 1993 at 80 sites in the Atlantic, Arctic, and Pacific Oceans. The Fukushima
nuclear havary effected aquatic discharge of minimum 2 × 1016 Bq into the Pacific.
Acidification, AMOC, Anoxia, Deoxygenation, Eutrophication, Heat
uptake, Meltwater, Oil spills, Plastic, Pollution, Primary production, Revelle
Factor, Sea water, Sea water stratification, Thermohaline circulation, Warming.
Environmental Geology, Munich, Germany.