1Laboratory for Remote Sensing and Geoinformatics, University of Texas at San Antonio, Texas, 78249, USA
2Key Laboratory for Polar Science of the State Oceanic Administration, Polar Research Institute of China, Shanghai, 200136, China
3School of Geographic & Oceanographic Sciences, Nanjing University, Nanjing, 210093, China
4Department of Earth Sciences, Zhejiang University, Hangzhou, 310027, China
5State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, 116024, China
6College of Physical and Environmental Oceanography, Ocean University of China, Qindao, 266100, China
Abstract. The Chinese National Arctic Research Expedition (CHINARE) in the summer 2010, primarily from 21 July to 28 August, in the ice zone of Arctic Pacific Sector, between 150° W to 180° W to 88.5° N, conducted comprehensive scientific studies on atmosphere-ice-ocean interactions, using icebreaker R.V. Xuelong. Measurements made included underway visual observations of snow and ice conditions at half-hourly time scale and EM31-measured ice thickness at one 12-day and eight short-term (3–4 h each) ice stations. The visual observation data are compared with AMSR-E ice concentration, ice thickness measured by a hanging EM31 from the vessel, and video-recorded image-derived ice concentration and pond coverage. A grid of 8 profiles of ice thickness measurements (four repeats) was conducted at the 12-day ice station (∼86°50' N–87°20' N) in the central Arctic and an average 2 cm day−1 melt rate, primarily bottom melt, was found, after surface melting had almost ceased. The high bottom melt rate, as compared with previous results from other studies, is consistent with the high floe speed (mean 0.17 m s−1) that is also larger than that previously reported. We also found that the daily AMSR-E ice concentration data can be used to map the marginal ice zone (MIZ) and its change. There are clear differences between the MIZ and pack ice zone in terms of ice concentration, thickness, ice type, floe size, as well as pond coverage. Results indicate that, as compared with the 2005 data from the Healy/Oden Trans-Arctic Expedition for the Arctic Pacific Sector (9 August to 10 September), the 2010 was first-year ice dominant (vs. the multiyear ice dominant in 2005), 70% or less in ice concentration (vs. 90% in 2005), 94–114 cm in ice thickness (vs. 150 cm in 2005). No snow cover was observed on the ice south of 78° N and 8–10 cm mean snow depth due to new snowfall events, which melted away after 17 August (vs. no snow cover south of 84.3° N or ~10 cm snow depth further north in 2005). Those changes indicate the continuation of ice thinning, less concentration, and younger ice after the 2007 shift, when a record minimum sea ice extent was observed. Overall, the measurements provided a valuable dataset of sea ice morphological properties over the Arctic Pacific Sector in summer 2010, which confirms, by comparison with previous data, that a "new normal" of Arctic sea ice is now present and is a benchmark for measurements of possible future changes.