Summer 2011 September Arctic Sea Ice Forecast

• Main Authors: Edward Blanchard-wrigglesworth, Cecilia Bitz, Jinlun Zhang, Ron Lindsay
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2005
• Subjects: Arctic; Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.364.906; http://www.arcus.org/files/search/sea-ice-outlook/2011/07/pdf/pan-arctic/blanchard_etal_panarctic_july.pdf

Our forecast uses a state-of-the-art General Circulation Model (GCM) initialized with average May 2011 sea ice area and volume anomalies obtained from the Pan-arctic Ice-Ocean Modeling and Assimilation System (PIOMAS). The GCM used is the National Center for Atmospheric Research (NCAR)’s Community Climate System Model version 4 (CCSM4) [1] at 1 ◦ resolution in all components. Our strategy is to initialize the sea ice with anomalies with respect to the model mean that are good approximations to actual Arctic sea ice anomalies. Because our predictions are several months in the future, we make no attempt to initialize the atmosphere with true conditions. Instead we create an ensemble of predictions from integrations that begin on June 1 with identical sea ice, ocean, and land conditions but with variable atmospheric initial conditions, which are drawn from consecutive days near June 1 of an arbitrary model year. In other words, an ensemble is created by shifting the dates of the initial conditions of the atmosphere component relative to the other components. We utilize one of 6 hindcast runs with CCSM4 that have been submitted for analysis to the CMIP5 dataset for IPCC AR5. The hindcast was run with observed greenhouse gas and aerosols through the year 2005. We take 2005 as the arbitrary year, which is close enough to present to be used for seasonal prediction in 2011. At this time we only apply anomalies to the sea ice and we apply no anomalies to the ocean or land. Without ocean anomalies in the initial conditions, the full ocean GCM of the model is not needed, so we carry out our integrations with a slab ocean model whose ocean heat flux convergences is specified from the CCSM4 hindcast for the years 1995-2005. We run the hindcast with slab