Dr. Ariaan Purich

Why did Antarctic sea ice increase despite global warming?

Supervisors: Ariaan Purich and Julie Arblaster

Field of study: Atmospheric science, climate modelling

Antarctic sea ice is an integral component of the global climate system, influencing the global surface albedo and the ocean overturning circulation. Antarctic sea ice variations are influenced by both atmospheric and oceanic processes, year-to-year variability in sea ice coverage is large, and there is still much that we don’t understand about the drivers of sea ice variability and change. A major challenge confronting the climate research community is that despite global warming, total Antarctic sea ice coverage increased over 1979–2015. Decadal variability in the tropical Pacific Ocean has been shown to influence regional sea ice trends but understanding the role of decadal variability is limited by the short length of sea ice observations. Coupled climate models are a useful tool to examine the influence of tropical decadal variability over longer periods. This project will use climate model output to gain a better understanding of how Pacific decadal variability has contributed to the observed Antarctic sea ice increase over recent decades. This will help us gain a better understanding of past and future changes in Antarctic sea ice and its key atmospheric drivers.

Southern Ocean freshening in coupled climate models

Supervisors: Ariaan Purich and Julie Arblaster
Field of study: Atmospheric science, oceanography, climate modelling

Over recent decades a surface freshening of the Southern Ocean has been observed. Many processes have likely contributed to this: a poleward shift in storm tracks and precipitation due to changes in the large-scale atmospheric circulation, changes in sea ice transport, and accelerated melting of the Antarctic ice sheet and shelves. Surface freshening increases the stratification of the Southern Ocean, which can have a strong influence on surface temperature and the uptake of heat and carbon. We can learn a lot about Southern Ocean surface freshening from coupled climate models. This project will use output from an ensemble of climate models to address two questions:

(1)   What processes are driving Southern Ocean surface freshening in the models?

(2)   How do the models’ mean-states affect the response to this surface freshening?

This project will improve our understanding of the expected response of the Southern Ocean to increased freshwater input over the 21st Century.

For further information contact Ariaan Purich