The Industrial Revolution has driven human advancement in technology and ease of life, albeit with detrimental environmental effects as well as the ocean surface. Burning fossil fuels and cutting down huge swaths of forests and other human activities have increased concentrations of greenhouse gases in the atmosphere.
The Fifth Assessment Report published by the Intergovernmental Panel on Climate Change (IPCC) in 2013 revealed that the ocean had absorbed more than 93 percent of the excess heat from greenhouse gas emissions since the 1970s. Additionally, the warming is speeding up and the top part of the ocean is warming up about 24 percent faster than it did a few decades ago.
Data from the US National Oceanic and Atmospheric Administration (NOAS) shows that the average global sea surface temperature has increased by approximately 0.13°C per decade over the past 100 years. A 2012 paper published in the journal Geophysical Research Letters revealed that the deep ocean is also affected, with one-third of the excess heat absorbed 700 m below the sea surface. A modeling study published in IPCC’s 2013 Report predicts that there is likely to be an increase in mean global ocean temperature of 1-4°C by 2100.
The ocean’s ability to absorb excess heat has shielded humans from even more rapid climate changes. However, the rise in ocean temperatures has had adverse effects. Deoxygenisation, which is the reduction in the amount of oxygen dissolved in the ocean signals ocean acidification; the decrease in PH of the ocean due to uptake of carbon dioxide. The rising sea levels also result from the thermal expansion of seawater and continental ice melting. The rippling effects on marine species and ecosystems consequently affect the benefits humans derive from the ocean.
The marine heatwaves have increased in frequency and strength over the past century. Marine fishes, seabirds marine mammals, and planktons living squarely in the zone where temperatures are increasing quickest face very high risks including high levels of mortalities, loss of breeding grounds, and mass movements as species search favorable environmental conditions.
For instance, corals are highly attuned to the temperature of water in which they live and a slight variation can stress them out causing them to bleach. Coral bleaching occurs when the coral becomes heat stressed and ejects the tiny marine algae, known as zooxanthellae that live in its tissue and give most of its color and energy. With zooxanthellae gone, the coral starves and its bone-white calcium skeleton becomes visible.
The Great Barrier Reef has especially raised concern after footage released by a conservation group showing damage up to 18 meters below the surface indicated that the reef may be suffering the most severe mass coral bleaching event on record. The Great Barrier Reef Marine Park Authority last week said Ariel surveys of more than 1000 individual reefs revealed more than half were rated as having high or very high levels of bleaching, and a smaller number in the south -less than 10 percent of the total- had extreme bleaching. Only about a quarter were relatively unaffected.
A 2012 report by the Food and Agriculture Organization of the United Nations estimates that marine and freshwater capture fisheries and aquaculture provide 4.3 billion people with about 15 percent of animal protein, a statistic which has more than increased. Ocean warming poses a serious risk to food security and peoples’ livelihoods globally, by altering distributions of fish stocks and increasing the vulnerability of fish species to diseases. Economic losses would likely run from tens to hundreds of millions of dollars, not to mention the related increased risk and spread of diseases in marine species.
Moreover, rising ocean temperatures cause more extreme weather events and loss of coastal protection, with cases of more severe hurricanes and the intensification of the El Nino events bringing droughts and floods, prevalent. The effects on vegetation such as mangroves which protect coastlines from erosion and sea level rise, are stark. Rising sea levels and erosion will particularly affect low-lying island countries in the Pacific Ocean, destroying housing and infrastructure and forcing people to relocate.
Therefore, it is urgent to achieve the mitigation targets set by the Paris Agreement on climate change and hold the increase in the global average temperature to well below 2°C above pre-industrial levels. Additionally, protecting marine and coastal ecosystems will regulate human activities and prevent environmental degradation. Restoration of elements of ecosystems that have already experienced damage would also boost the resilience of species. Governments also need to increase investments in scientific research to measure and monitor ocean warming and its effects.
Dr Selina Ward, a marine biologist and former academic director of the University of Queensland’s Heron Island Research station says the world can not expect to save the marine ecosystem and be opening new fossil fuel developments. “It is time to act and there are no more excuses.” She says.
