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The melting of glacial ice and the thermal expansion of ocean water will cause sea levels to rise in future years. While this is unlikely to have a great effect on most ocean life, there are some cases where the change might be too fast for certain ecosystems to adapt. This could be a particular problem with coral reefs, which might not be able to grow fast enough to counteract the rise in sea level (Harley, 2006). The loss of these ice sheets is also expected to contribute to global warming, as it would lower the albedo of the earth, causing less solar radiation to be reflected back out into space (IPCC, 2001).
Climate change has Changes in the temperature of ocean water have the potential to cause significant changes in water chemistry, especially with regards to oxygen solubility. As seawater warms, its ability to dissolve gases decreases dramatically. One of these gases is oxygen, which of course is essential to most living things all animals for respiration (Harley, 2006). Geological records from past global warming events has shown evidence of severe, large-scale hypoxic episodes, sometimes reaching global scales (Bralower, 2002). A significant drop in dissolved oxygen levels would detrimentally influence species worldwide. Another critical area of seawater chemistry that will likely be affected by global warming is the carbonate buffering system. The ocean have an enormous capacity to take up carbon dioxide. However, as atmospheric carbon dioxide levels rise, the equilibrium of the carbonate-bicarbonate-carbonic acid cycle will be increasingly shifted toward the acidic side of the equation, lowering the pH of the water (Harley, 2006). Ocean acidification would have detrimental effects on sea life, especially important calcareous primary producers, such as coccolithophores. There is also geological data which indicates build up of toxins in the ocean during intense global warming events (Bralower, 2002).
The introduction of fresh water into the oceans from melting ice caps can also affect thermohaline circulation. Since fresh water is less dense than salt water, it floats on the surface in high latitude regions. This cap prevents the sinking of water in regions of downwelling, thus weakening or stopping the overturn of the ocean. Current models predict that a shutdown of downwelling in the North Atlantic could occur soon and lead to a shutdown of global ocean circulation (Gagosian 2007). A shutdown of global thermohaline circulation is likely to cause rapid and severe changes in climate, with similar changes in temperature to what has been recorded over the past century occurring on the scale of decades (Gagosian 2007).
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