How might warmer oceans accelerate global warming?
http://www.guardian.co.uk/environment/2006/nov/29/climatechange.climatechangeenvironment
To understand how warmer oceans can accelerate global warming, we need to dive into the intricate linkages between the oceans and Earth's climate system.
1. Increased Greenhouse Gas Emissions: Warmer ocean temperatures can potentially lead to an increase in the release of greenhouse gases, particularly carbon dioxide (CO2) and methane (CH4), into the atmosphere. For example:
- Oceanic Carbon Cycle: A warmer ocean disrupts the delicate balance of the oceanic carbon cycle. As the water heats up, it can hold less dissolved CO2, leading to the release of this excess CO2 into the atmosphere. This can amplify the greenhouse effect, causing further warming.
- Methane Hydrates: In colder ocean waters, vast amounts of methane, a potent greenhouse gas, are locked in frozen methane hydrates on the ocean floor. If the oceans warm, these hydrates could thaw, releasing large amounts of methane into the atmosphere.
2. Reduced Oceanic Carbon Sink: Oceans act as a significant carbon sink, absorbing about 30% of the CO2 emitted by human activities. However, warmer waters can disrupt this process in multiple ways:
- Weakened Solubility: Warm water holds less dissolved CO2, reducing the oceans' capacity to absorb atmospheric CO2. This decreases the efficiency of the oceanic carbon sink, leading to the retention of more CO2 in the atmosphere and exacerbating global warming.
- Altered Circulation: Warm oceanic temperatures can modify ocean currents and circulation patterns, hampering the transportation of absorbed carbon from the surface to the deep ocean. As a result, carbon remains closer to the surface, limiting the effectiveness of the carbon sink.
3. Feedback Mechanisms: Warmer oceans can trigger various positive feedback loops, intensifying the global warming process:
- Melting of Ice: Rising ocean temperatures contribute to the accelerated melting of ice in polar regions and glaciers. As ice melts, it reduces Earth's albedo, which is a measure of its reflectivity. Decreased albedo means that more sunlight is absorbed by the Earth's surface, further increasing temperatures and warming the oceans.
- Weakening of Thermohaline Circulation: Rising temperatures can disrupt the global thermohaline circulation, a vital oceanic current system that redistributes heat around the planet. A weakened circulation could alter climate patterns, leading to more extreme weather events, including heatwaves, storms, and droughts.
Understanding these interconnections helps us comprehend how warmer oceans can contribute to the acceleration of global warming. It emphasizes the importance of taking measures to mitigate climate change and reduce greenhouse gas emissions to minimize these impacts.