Sulfate aerosols over the Southern Ocean

Sun shining on low cloud cover. Photo by Dave Allen

Improving the representation of sulfate aerosols over the Southern Ocean in the NZESM

Have you ever looked at the ocean and noticed that the sky above it appeared hazy? This is caused by the presence of tiny particles or droplets in the air.

  • Project budget: $255 710
  • Project Duration: July 2017 - June 2019

In remote, unpolluted regions such as the Southern Ocean, such “aerosols” form from natural sources, such as ocean waves breaking and releasing sea salt into the air. A particularly important type of aerosol, sulfate aerosol, forms when sea ice melts. Algae growing on the underside of sea ice produce dimethyl sulphide, which – when the ice melts – is released into the atmosphere. Dimethyl sulfide then undergoes a series of chemical reactions to form sulfate aerosol.

Aerosols over the Southern Ocean are important because they influence cloud formation and play a role in the energy budget. However, the way aerosols behave in the atmosphere is complex, and it’s currently difficult to model them accurately. This may be one reason why the NZ Earth System Model (NZESM) has difficulty simulating the energy budget over the Southern Ocean, which has flow-on implications for simulating New Zealand’s climate. In this project, we’ll upgrade and fine-tune the way the NZESM simulates sulfate aerosols, with the aim of improving climate simulations of the southern hemisphere.

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