After crossing the equator we sampled a series of stations in the southern hemisphere to find out what is going on in the Southern Gyre.
A gyre is a swirling vortex, which in the ocean is created by wind or currents. There are two main gyres in the Atlantic Ocean, which are created by currents. The Northern Gyre circulates clockwise and is created by the North Equatorial and North Atlantic currents. The Southern Gyre swirls anti-clockwise and is created by the South Equatorial and Antarctic Circumpolar currents. These cyclonic gyres are like deserts on land that exist at the same latitudes – they are warm, low in nutrients and, compared to shelf seas and upwelling regions, are void of life.
VIIRS chlorophyll-a median composite 18–24 October 2017, with the ship’s track and sampling stations overlaid as a black line with diamonds. The large dark-blue area shows the Southern Ocean Gyre. chlorophyll-a scale bar is at the bottom of the image. (Satellite imagery provided by Silvia Pardo from the National Earth Observation Data Archive and Analysis Service)
These two gyres have distinct biological, chemical and physical properties. The Southern Gyre, which is larger, is more productive fixing on average 2.86 Gt ...