Studying the impact of cyclones on Antarctic sea ice using a new brittle sea ice model
Sea ice plays an important role in global climate, ocean circulation and Antarctic ecosystem habitats - how do cyclones affect the behaviour of sea ice? Dr. Rafael Santana aims to find out in this Opportunity Fund project.
Background
Antarctic sea ice is a vital climate system component as it mediates heat, mass, and momentum fluxes between the Southern Ocean and atmosphere. Sea ice is also a habitat for different species and play an important role in organic carbon cycling. Yet, Antarctic sea ice extent has experienced record minima in recent years, and models for predicting future sea ice behaviour are unreliable. The variability of sea ice is also poorly represented in climate models, limiting our ability to predict future polar climate.
This project takes advantage of a new configuration of the Next Generation Sea Ice Model (neXtSIM), which has been developed for Antarctic sea ice evolution (neXtSIM-Ant). neXtSIM-Ant uses brittle rheology to better represent how sea ice fractures and interacts with the ocean and atmosphere. This Southern Hemisphere configuration has been calibrated and validated using available observational data, and the results demonstrate the effectiveness of neXtSIM in reproducing observed sea ice extent, thickness, and drift.
Cyclones are known to control the regional evolution of sea ice, and the coupled physical interaction between sea ice fracture and storms is a key missing feature in current modelling approaches to Antarctic sea ice. In this project, we will use neXtSIM-Ant to study the dynamic behaviour of sea ice (breakage, deformation and growth) in response to atmospheric cyclones.
Research overview
We will evaluate the impact of cyclones on Antarctic sea ice using a series of locally-run numerical experiments.
We will use a tracking algorithm to extract and analyse neXtSIM-Ant hindcast variables during the passage of identified storms/cyclones, which we will compare with simulations using a traditional sea ice model (EVP rheology). We will compare the sea ice response in neXtSIM-Ant to satellite observations of sea ice deformation and drift and prediction from EVP-based models. By doing so, we will examine the impact of cyclones on rapid sea ice loss/growth around Antarctica in new ways not currently available to researchers outside New Zealand.
This study will provide insights into the complex interactions between the atmosphere, ocean, and sea ice and how storms shape the Antarctic sea ice cover. In the future, neXtSIM-Ant can be used in coupled simulations with oceanic and atmospheric models within the Antarctic Science Platform (ASP) Modelling Hub to tackle scientific questions regarding the coupled interactions of these climate components, representing the first such physically realistic model of its kind, developed in Aotearoa New Zealand.
Maps of sea ice concentration from the mEVP (or just EVP, left) and BBM (neXtSIM-Ant, right) model runs at 21h 24/07/2016 UTC. The different segments of the Southern Ocean are highlighted in magenta on the left plot where AB represents the Amundsen and Bellingshausen Seas. On the right, the black contours represent surface atmospheric pressure shown at every 10 hPa and the magenta circle highlights the centre of an atmospheric cyclone. The mEVP and BBM runs used the same atmospheric forcing (ERA5). Credit: Rafa Santana.
Collaborators
Dr. Melinda Webster (University of Washington, USA) and Dr. Chris Horvat (University of Auckland, Brown University) are sea ice experts with a history of publications related to cyclone impacts on sea ice. They will provide guidance and insight into the analysis sea ice model output and variables of interest.