David A. Hebert

Short‐term sea ice forecasting: An assessment of ice concentration and ice drift forecasts using the U.S. Navy's Arctic Cap Nowcast/Forecast System

In this study the forecast skill of the U.S. Navy operational Arctic sea ice forecast system, the Arctic Cap Nowcast/Forecast System (ACNFS), is presented for the period Feb 2014 – June 2015. ACNFS is designed to provide short term, 1-7 day forecasts of Arctic sea ice and ocean conditions. Many quantities are forecast by ACNFS; the most commonly used include ice concentration, ice thickness, ice velocity, sea surface temperature, sea surface salinity, and sea surface velocities. Ice concentration forecast skill is compared to a persistent ice state and historical sea ice climatology. Skill scores are focused on areas where ice concentration changes by ±5% or more, and are therefore limited to primarily the marginal ice zone. We demonstrate that ACNFS forecasts are skillful compared to assuming a persistent ice state, especially beyond 24 hours. ACNFS is also shown to be particularly skillful compared to a climatologic state for forecasts up to 102 hours. Modeled ice drift velocity is compared to observed buoy data from the International Arctic Buoy Programme. A seasonal bias is shown where ACNFS is slower than IABP velocity in the summer months and faster in the winter months. In February 2015 ACNFS began to assimilate a blended ice concentration derived from Advanced Microwave Scanning Radiometer 2 (AMSR2) and the Interactive Multisensor Snow and Ice Mapping System (IMS). Preliminary results show that assimilating AMSR2 blended with IMS improves the short-term forecast skill and ice edge location compared to the independently derived National Ice Center Ice Edge product. This article is protected by copyright. All rights reserved.

Real-time Data Assimilation of satellite derived ice concentration into the Arctic Cap Nowcast/Forecast System (ACNFS)

Over the last decade, ice conditions in the Arctic have changed dramatically resulting in the Arctic having a minimum in ice extent during the summers of 2007, 2008 and 2010. With this rapidly changing polar environment, the need for accurate ice forecasts is essential. The Naval Research Laboratory (NRL) has developed the Arctic Cap Nowcast/Forecast System (ACNFS), a two-way coupled ice/ocean system, to forecast ice conditions in the polar regions. This system applies the Los Alamos Community Ice CodE (CICE) coupled via the Earth System Modeling Framework (ESMF) to the HYbrid Coordinate Ocean Model (HYCOM). The Navy Coupled Ocean Data Assimilation (NCODA), a 3-Dimensional VARiational analysis (3DVAR) scheme, is used to assimilate ice and ocean observations into the forecast system. Ice concentration data from two sources: the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I) and the Advanced Microwave Scanning Radiometer for Earth Observation System (AMSR-E) are used as observations for the ice analysis. Results from the coupled system using both concentration input datasets will be discussed.