Forecasting Future Sea Ice Conditions in the MIZ: a Lagrangian Approach

Monday, 15 December 2014: 2:10 PM
Bruno Tremblay1, Robert Newton2, Patricia de Repentigny1, Stephanie L Pfirman3, Walter Meier4 and G. Garrett Campbell5, (1)McGill University, Montreal, QC, Canada, (2)Columbia University of New York, Palisades, NY, United States, (3)Barnard College, Closter, NJ, United States, (4)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (5)University of Colorado at Boulder, Boulder, CO, United States
Significant changes in Arctic sea ice extent have been observed in recent years, particularly at the end of the summer. Climate models that have a reasonable late 20th century Arctic climate, forecast ice-free summers in the Arctic before the end of this century. While these models agree on the decline of sea ice extent and the likelihood of a largely seasonal Arctic sea ice cover, the pattern of the sea ice loss and marginal ice zone locations predicted by different models varies widely. Narrowing the uncertainty implicit in these model disagreements is an important contribution to the accuracy of global climate projections. To this end we track the boundary between first and multi-year ice (i.e. the minimum September sea-ice edge position) using Lagrangian back and forward trajectories in both the instrumental record and GCMs participating in the IPCC-AR5. We use the trajectories to quantify the magnitude and interannual variability in the thermodynamic and dynamic (ice export) ice loss, the amount and geographical distribution of multiyear ice melt and first year promotion to second year ice. Results clearly highlight the importance of pre-conditioning (previous winter ice export) on the following summer minimum ice extent. Assessing whether climate models reproduce the correct dynamics of the MIZ can increase our confidence in climate forecasts.