Although Antarctica is better protected by international legislations, the Arctic usually commands most of the attention among climate watchers, especially in the case of the melting of sea ice and its subsequent impacts. However, like the Arctic Ocean, Climate Change in the Southern Ocean also deserves the attention of climate watchers.
The Importance of the Southern Ocean
Climate Change in the Southern Ocean is incredibly relevant, given that greater than 60 per cent of the Earth’s anthropogenic heat and between 40 and 50 per cent of anthropogenic carbon dioxide absorbed by the oceans for example is absorbed by the Southern Ocean (Marinov, undated). However, Climate Change in the Southern Ocean entails a great many other changes that might limit its ability to perform beneficial services in the case of the carbon cycle.
Climate Change in the Southern Ocean thus is principally relevant when the huge volume of water it possesses stores greater heat and carbon dioxide than any other stretch of latitudinal area in the world. Like in the Arctic Ocean, sea ice also forms in the Southern Ocean in areas reaching up to three times the size of Australia. The Antarctic Circumpolar Current in the Southern Ocean is Earth’s largest ocean current, and merges the waters of the Pacific, the Atlantic and the Indian Oceans. When the bottom water circulates through to the world’s oceans, it contributes majorly to regulating atmospheric temperatures globally.
The Southern Ocean has a particularly important role to play in terms of storing both the Earth’s heat and also carbon. More than half of the extra heat energy stored by the Earth reaches the oceans through the Southern Ocean and about 40 per cent of the carbon dioxide stored in the oceans reaches them through the Southern Ocean. Given that the Southern Ocean covers about one-fifths of the total area of the Earth covered by oceans, the Southern ocean comes out as about two and a half times more effective in terms of storing heat and carbon.
The Southern Ocean is able to store a huge amount of heat and carbon because it acts as a passage from surface waters to the deep ocean through its ocean currents. The Southern Ocean is the only ocean in the world where waters from the deep ocean rise up to the ocean surface. The converse is also true in that it is among the few oceans in the world where large amounts of surface water sink from the ocean’s surface down to the deep ocean. This rising and sinking of ocean water makes the storing of heat and carbon possible (The Conversation, 2011).
Changes Observed in the Southern Ocean
Given the importance of the Southern Ocean to regulating global temperatures, it should alarm us that rapid changes are afoot due to many factors including Climate Change in the Southern Ocean. Observations of the Southern Ocean indicate that over several decades the waters in the Southern Ocean are acidifying, warming, becoming less saline, and also depleting in oxygen. The Antarctic bottom water released has also halved since 1970 (ACE CRC, 2015).
Many experts believe that the flows of the Southern Ocean do play a role in moderating global warming. However, with the recent changes to the Southern Ocean as mentioned before, this could mean a reduced capacity of the Southern Ocean and the planet as a whole to control changed weather patterns, sea level rise, and it could also affect marine life, especially their ability to form skeletons, shells and reefs.
Studies point towards the fact that greater than 90 per cent of the solar heat absorbed by the Earth is utilized in warming Earth’s oceans. Any plan on combating Climate Change should therefore focus on in depth studies of the Earth’s oceans. The progress of Climate Change is slowed by the absorption of atmospheric carbon dioxide by the oceans.
When investigating Climate Change in the Southern Ocean, it becomes necessary to take into account recent studies on the changing nature of the Southern Ocean. Among the changes recently observed is the warming of the ocean coupled with an increase in the amount of carbon dioxide accumulating in the ocean. To add to this is the decrease in the salinity of the Southern Ocean and also the increase in the acidification of the Southern Ocean.
The Effects on Climate Change in the Southern Ocean
These combined symptoms can have multiple effects in terms of Climate Change in the Southern Ocean, if we are to look at observed versus anticipated effects of Climate Change in the Southern Ocean. For example, it is most likely that the continued warming of the Southern Ocean could increase the rate of melting of the ice flowing off Antarctica into the Southern Ocean (The Conversation, 2011). Also in what can be interpreted as an ominous warning, the Larsen C ice shelf broke off from the mainland in 2017, forming what was a 5,800 sq km iceberg. These can have serious implications in terms of Climate Change in the Southern Ocean if we consider sea level rise in an increasingly warming world.
Another impact of Climate Change in the Southern Ocean can be a weakening of its ability to act as a carbon sink. In what is supposed to be benign cycle whereby the Southern Ocean absorbs large amounts of carbon dioxide thereby acting to reduce or delay the effects of Climate Change, the excess accumulation of carbon dioxide in the Southern Ocean coupled with a reduction in the volumes of water circulating between the deep ocean and surface water will severely deplete its capacity to take in more and more carbon dioxide in the long run. This condition can only worsen with more and more carbon dioxide becoming available in the Earth’s atmosphere.
An offshoot of Climate Change in the Southern Ocean similarly is a change in the chemistry of the Southern Ocean, including a depletion of the oxygen available in the Southern Ocean along with a decrease in ocean salinity. Another major and much talked about change in the chemistry of the Southern Ocean is the increase in the acidification of the Southern Ocean which makes life more difficult for marine organisms in forming shells or skeletons from calcium carbonate for example. The corrosive effects of acidic water on calcium carbonate can vary depending on the temperature of the water, and the warmer the water, the more the corrosive effects of acidic water on calcium carbonate utilized by marine organisms are expected to be realized.
The marine biota in the Southern Ocean chiefly includes microbes, zooplankton, fish, salps, Antarctic krill, benthic organisms, cephalopods, marine mammals and sea-birds. The changes afoot due to Climate Change in the Southern Ocean, such as warming, reduction in ocean salinity, an increase in ocean eddy activity, ocean acidification, depletion of oxygen levels and the increase in intensity of westerly winds, with poleward movement, are all significant indicators for possible significant changes in marine ecosystems in the Southern Ocean as well. The reduction of sea ice is also expected to influence habitats.
A southwards movement in general could be expected for many marine organisms and habitats with the warming of the Southern Ocean, especially at the lower trophic levels. The tolerance of marine organisms to warming oceans could also be tested, along with significant changes in productivity. Ocean acidification might impact the corrosion of calcium carbonate as mentioned above, with warming an ominous sign of its intensification. This combination of warming and ocean acidification could bring about significant changes to benthic habitats in particular (Constable et al., 2014).
The changes of Climate Change in the Southern Ocean thus far have been minor, and the great positive has been the reduction in the ozone hole over Antarctica. However, with the Antarctic continent warming at a much higher rate than much of the rest of the world, could have severe implications not just for the ocean itself, but for the rest of the Earth. It is difficult to express the importance of the Southern Ocean when much of the effects of Climate Change in the Southern Ocean are based on the collection of scientific data and not largely visible effects such as melting sea ice in the Arctic. Tackling Climate Change in the Southern Ocean would thus require great synergy between science and policy if we are to safeguard it.