<P> In the South - West Atlantic a peak was reached in the mid-1980s and catches now fluctuate between 1.7 and 2.6 million tons . The most important species, the Argentine shortfin squid, which reached half a million tons in 2013 or half the peak value, is considered fully fished to overfished . Another important species was the Brazilian sardinella, with a production of 100,000 tons in 2013 it is now considered overfished . Half the stocks in this area are being fished at unsustainable levels: Whitehead's round herring has not yet reached fully fished but Cunene horse mackerel is overfished . The sea snail perlemoen abalone is targeted by illegal fishing and remain overfished . </P> <P> Endangered marine species include the manatee, seals, sea lions, turtles, and whales . Drift net fishing can kill dolphins, albatrosses and other seabirds (petrels, auks), hastening the fish stock decline and contributing to international disputes . Municipal pollution comes from the eastern United States, southern Brazil, and eastern Argentina; oil pollution in the Caribbean Sea, Gulf of Mexico, Lake Maracaibo, Mediterranean Sea, and North Sea; and industrial waste and municipal sewage pollution in the Baltic Sea, North Sea, and Mediterranean Sea . </P> <P> North Atlantic hurricane activity has increased over past decades because of increased sea surface temperature (SST) at tropical latitudes, changes that can be attributed to either the natural Atlantic Multidecadal Oscillation (AMO) or to anthropogenic climate change . A 2005 report indicated that the Atlantic meridional overturning circulation (AMOC) slowed down by 30% between 1957 and 2004 . If the AMO were responsible for SST variability, the AMOC would have increased in strength, which is apparently not the case . Furthermore, it is clear from statistical analyses of annual tropical cyclones that these changes do not display multidecadal cyclicity . Therefore, these changes in SST must be caused by human activities . </P> <P> The ocean mixed layer plays an important role heat storage over seasonal and decadal time - scales, whereas deeper layers are affected over millennia and has a heat capacity about 50 times that of the mixed layer . This heat uptake provides a time - lag for climate change but it also results in a thermal expansion of the oceans which contribute to sea - level rise . 21st century global warming will probably result in an equilibrium sea - level rise five times greater than today, whilst melting of glaciers, including that of the Greenland ice - sheet, expected to have virtually no effect during the 21st century, will probably result in a sea - level rise of 3--6 m over a millennium . </P>

Where are deep water masses formed (geographic locations) why