Effects of Climate Change on Open Oceans




Dr. Areti Tseliou
Bioclimatologist,
Agricultural University of Athens, Greece
Email: tseliou.a@outlook.com
The Ocean Magnitude

When thinking the nowadays big issue of climate change, little things are known regarding the role of the oceans on it. If we consider that 71% of the Earth’s surface is covered by Ocean, with an average depth between 4,000 and 11,000 fdff and it can be compared with the highest world mountains (Mount Everest peaks the 8,848 meters above sea level) then it is easy for someone to realise the dominant role of the ocean on the climate system and vice versa.

How Oceans are related with the climate system
  • The deep ocean constitutes an enormous reservoir in which carbon can be stored for thousands of years. When sea water reaches the Polar Region due to the ocean circulation, it freezes, becomes heavier and sinks. Having first been in contact with the atmosphere it absorbs CO2 molecules and in that way large amounts of CO2 are removed from the atmosphere and are transferred to the deep ocean.
  • Water is characterised with high specific heat and this means that only a small rise in the water surface temperature can release large amounts of heat in the atmosphere.
  • The ocean holds about 1000 times more heat than the atmosphere and the evaporation of water from the ocean consists of an important mechanism of heat transform to the atmosphere. Consequently.
  • An increase in the air temperature leads to higher evaporation and higher heat transform to the atmosphere
  • The ocean conveyor affects climate because the flow of water to the North Atlantic involves an enormous transport of heat. This explains the reason for which the climate of northern Europe is reasonably mild despite its high latitude.
Melting Ice and sea level rise

Ice sheets are great indicators in climate change. The ice sheet melting causes sea level rise. Greenland holds seven meters of sea level equivalence which means a seven meters of sea level rise if all of it melts. And other five meters sea level rise comes if the West Antarctic ice sheet melts. In recent years, the Arctic’s frozen waters have been melting dramatically, with wide environmental effects. The melting of sea ice can exacerbate global warming.

In September 2012 ice extent was the smallest since satellite records began in 1979. The annual loss of ice has doubled in the case of Greenland and tripled in the West Antarctic compared to figures from 2009. Per year, the ice sheets dump some 500 cubic kilometers of ice into the oceans and that can be compared to an ice sheet that's 600 meters thick and covers an area as big as Singapore. Since 1880, global average sea level has increased 8 inches.

The role of the ocean albedo on climate change

Albedo is the fraction of incoming sunlight that is reflected rather than absorbed. Currently, Earth's albedo is roughly 0.3, meaning that 30% of incoming sunlight is reflected back into space. The larger the albedo it is the higher the amount of energy reflected and less the amount of heat releases by Earth to atmosphere. The large glaciers covering Greenland and Antarctica reflect as much as 75% of the insolation falling on their surfaces. The disappearing of the glaciers and the sea ice provokes an extra global warming because there is more exposed ocean to absorb and then release solar heat. By studying the effects from sea ice and glacier loss scientists predict extreme weather phenomena in the Northern Hemisphere.

The impact of Climate change in Pacific

The impact of climate change is already visible in the case of the Pacific Ocean islands. Pacific covers a third of the surface of the Earth and accommodates 25,000 islands the 10,000 of which are inhabited. The last decades land gradually sinks into the ocean due to the sea level rise. In Tuvalou, a Polynesian island nation located in the Pacific Ocean, with an average elevation of only two meters above sea level, sea water encroaches from below as well, bubbling up through the porous coral rock during high tides, regularly flooding low-lying areas. The rising saltwater table could destroy deep rooted food crops such as coconut, as saltwater contaminates the soil and freshwater resources. As bad outcomes of the climate change that Pacific islands already experience are the irregular seasons, the less predictable rainfall that contribute to droughts and water shortage, the changes in biodiversity, the changes in the ocean chemistry because of increased CO2 emissions.

Moreover, the rising sea surface temperature is affecting coral atolls reducing fish and shellfish populations. The predictions over the 21st Century according to the 2011 report of the "Pacific Climate Change Science Program" of Australian concludes, among others, that there is very high confidence the Surface air temperature and sea surface temperature to continue to increase, as well as, the intensity and frequency of days of extreme heat and rainfall. I t is also predicted that the mean sea-level rise will continue. The Marshall Islands, a Micronesian country spread across 24 coral atolls, government is working with other Pacific nations to stop importing petrochemicals and gas and become completely carbon-neutral by 2020. In Fiji, a group of more than 300 volcanic islands, governments are relocating people inland, away from eroding and less productive shorelines.

We must consider "the ocean" because:
  • More than one-half of the world's population lives within 100 km of the ocean.
  • The top 10 feet of the ocean surface contains more heat than the whole atmosphere.
  • El Niño and other climatic phenomena result from ocean temperature changes which in turn have impacts on weather events such as hurricanes, typhoons, floods and droughts.

Scientists believe that by reducing the emissions of greenhouse gases the pace of ice loss will be slowed down.

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