I don’t often get to write about oceanography in my day job as a policy officer, but as today is World Oceans Day I jumped at the chance to write a short piece about why physics is so important in the discipline of oceanography.
Physical oceanography is the study of physics and marine systems. It includes the distribution of temperature and salinity in the oceans, water mass formation and movement, ocean currents, interior and surface mixing, energy inputs, waves and tides. It’s a hugely important area as the oceans make up a vast amount of our planet, as well as being home to marine life and being vital for our livelihood.
The oceans also play a big role in controlling our weather and climate. Physical oceanography is a wide-ranging discipline, but I’ve picked two important areas to highlight here, where physics is crucial in understanding how the planet is responding to a changing climate.
Understanding ocean circulation
Ocean circulation has a strong influence on the regulation of Earth’s climate by transporting heat throughout the oceans, along with carbon, oxygen and nutrients, which means it plays a central role in supporting marine life.
A number of processes form ocean circulation, such as heat from the sun, tides, winds, the Coriolis Effect and water density changes – due to variations of temperature and salinity. In the top 100m of the ocean winds drive ocean currents, but there are also currents thousands of metres below the surface that are controlled by temperature and salinity.
The effects of climate change on ocean circulation are complex: the latest IPCC report had low confidence in separating long term trends from decadal changes, which was put down to a lack of direct measurements of ocean circulation. However, recent observation efforts, as well as new satellite measurements are improving this understanding. This brings me on nicely to my second area of physical oceanography: satellites.
The use of satellites
Satellites have transformed the way in which ocean properties are measured. They provide views of the ocean surface on a near global scale and provide rapid data collection, including in regions where it would be difficult to gather reliable data in situ (such as from ships or ocean buoys). These measurements include sea surface temperature, sea surface chlorophyll and wind speed.
Rising sea levels are one consequence of climate change that is projected to have large impacts – caused predominantly by the thermal expansion of the oceans and melting glaciers as temperatures rose in the 20th century. Satellites form a big part of determining this by measuring global average sea level over time.
This data can be used to test climate models’ predictions of global warming and to explore the role of the oceans in the Earth system. Of course, these satellites are also used to forecast the weather.
As well as being a crucial discipline for understanding weather and climate, physical oceanography is an exciting and growing area of research, and is just one exciting example of applying physics to the world!
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