Background
Ocean circulations (currents, waves, tides) are continuous, directed movements of ocean water. It is a key regulator of climate by storing and transporting heat, carbon, nutrients, and freshwater all around the world. Various forces acting upon this ocean circulation, such as breaking waves, wind, Coriolis force, temperature and salinity differences, tides, depth contours, shoreline configurations and interaction with other currents influence a current’s direction and strength.
The temperature of the water at the ocean surface (Sea surface temperature) an important physical attribute of the world’s oceans which varies mainly with latitude, with the warmest waters near the equator and the coldest waters in the Arctic and Antarctic regions.
Oceans have a fever- here’s why
Record Rise in global ocean temperature (Oceans fever) is hot topic for geographics and environmentalist.
As the oceans absorb more heat, sea surface temperature increases, and the ocean circulation patterns that transport warm and cold water around the globe change.
According to the Copernicus Climate Change Service (C3S) the average global sea surface temperature (SST) for February 2024 stood at 21.06 degree Celsius, the highest ever for previous this month in a dataset going back to 1979. The previous 20.98 degree Celsius SST record temperature was set in august 2023.
Based on the historical record, increases in sea surface temperature have largely occurred over two key periods: between 1910 and 1940, and from about 1970 to the present. Sea surface temperature appears to have cooled between 1880 and 1910.
Major reasons behind the oceans getting warmer –
Since the middle of the 19th century after Industrial Revolution human activities such as the increased burning of fossil fuels has released high levels of greenhouse gases (GHGs) in the atmosphere. which trap heat in the atmosphere and contribute to global warming. As a result, the average global temperature has risen at least 1.2 degree Celsius above pre-industrial times. Almost 90 per cent of the extra heat trapped by GHGs has been absorbed by the oceans, which has made oceans steadily warmer over the decades.
Some other reasons also contributing in Ocean fever-
El Niño: El Nino unusually warm ocean temperatures in the Equatorial Pacific region. But the current high global average SST However begun to rise well even developed fully before the ongoing El Nino and remains unusually high even now after as the weather pattern has peaked and begun to wane. This weather pattern, causing abnormal long-lasting warming of waters in the equatorial Pacific Ocean, contributes to both ocean and global temperature rises.
Roll of Sahara Desert dust –
According to a report the dust typically forms a giant shadow that shades the Atlantic water form sun rays and reduces ocean temperatures. But for some time now there is less dust blowing off the Sahara Desert of due to weaker than average winds leading to increased sunlight absorption and higher ocean temperatures.
Reduction in sulphur dioxide emission: –
International regulations 2020 reduced the amount of allowed sulphur in marine shipping fuels to reduce sulphur dioxide (health-damaging air pollutant). Earlier which sulphate aerosols in the atmosphere and act like a cloud, preventing solar radiation from reaching the ocean surface, sunlight absorption and higher ocean temperatures.
Consequences of such Ocean Fever-
- Increased sea surface temperature is causing the ocean stratification to increase. Increased stratification lead to, disrupting the mixing of water layers, less absorption of carbon dioxide by ocean, nutrients are not allowed to travel up to ocean surface from below, these affect collapse of marine ecosystem especially the population of phytoplankton, crucial for marine food webs.
- Warmer ocean causes marine heat waves (MHWs) such MHWs have doubled in frequency between 1982 and 2016, causing intense coral bleaching which harms coral reproduction and increases vulnerability to diseases, death of fishes and aquatic animals, change migration pattern of aquatic animals in short period of time.
- Warmer ocean can lead to more frequent and more intense storms, heavier rain fall and flooding.
To mitigate the impacts of rising sea surface temperatures, urgent action to reduce greenhouse gas emissions is vital. which exacerbating marine ecosystem damage and intensifying storms. Reducing emissions can slow these trends, as emphasized by the World Meteorological Organisation’s reports. (WMO) warned in its Global climate report-2023 that 66 % chances that at least one of the year between 2023 and 2027 would cross the threshold of 1.5-degree Celsius above pre industrial level.
