Search

In summer 2018, thick sea ice blocked the mouth of the Amundsen Gulf (AG), Canada, obstructing shipping through the North-west Passage. This study analysed multi-year ice motion to investigate the source of this thick ice and the reasons for its unusual movement. For this purpose, a daily multi-year ice distribution product was generated by ice tracking using gridded daily sea-ice velocities (2003–2018) derived from the AMSR-E and AMSR-2 data. From autumn 2017 to summer 2018, the area of multi-year ice extended westward to the Beaufort Sea and then migrated towards the AG mouth. The primary cause of the unusual ice cover was anomalous AG-ward wind in September 2018. It is known that multi-year ice has become increasingly moveable over the past decades, as indicated by the increasing wind factor (i.e., ratio of ice-drift speed and wind speed), but the unusual ice motion in the summer of 2018 cannot be explainable by the wind factor alone. Accurately, predicting monthly wind and monitoring old thick ice will reduce the risk posed by thick Arctic sea ice to shipping.

This paper examines the temporal and spatial change in the characteristics of sea-ice motion in the Arctic. Ice motion is generally expressed by a motion at a constant ratio (wind factor) of wind speed, with a certain angle (turning angle) from the wind direction, and ocean currents. This study aimed to reveal the recent changes of the wind factor and turning angle using satellite observation data. We first prepared a daily ice-velocity data set from data for 2003–2017 collected by the satellite microwave sensor Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) and its successor, AMSR2. Monthly values of the wind factor and turning angle were calculated by a least squares technique, based on the linear relationship between sea-ice velocity and geostrophic wind velocity. The daily variation of sea-ice motion was strongly correlated with that of the wind. The wind factor and turning angle changed regionally, seasonally and interannually. With regard to long-term trends, the wind factor has increased in almost all areas of the Arctic. However, the trend of increase stopped around 2010, especially around the central Arctic.

Summer sea-ice cover in the Arctic varies largely from year to year owing to several factors. This study examines one such factor, the relationship between interannual difference in winter ice motion and ice area in the following summer. A daily-ice velocity product on a 37.5-km resolution grid is prepared using the satellite passive microwave sensor Advanced Microwave Scanning Radiometer*Earth Observing System data for the nine years of 2003-2011. Derived daily-ice motion reveals the dynamic modification of the winter ice cover. The winter ice divergence/convergence is strongly related to the summer ice cover in some regions; the correlation coefficient between the winter ice convergence and summer ice area ranges between 0.5 and 0.9 in areas with high interannual variability. This relation implies that the winter ice redistribution controls the spring ice thickness and the summer ice cover. Keywords: Sea ice; Arctic; satellite remote-sensing; interannual variability; AMSR-E data (Published: 8 November 2013) Citation: Polar Research 2013, 32 , 20193, http://dx.doi.org/10.3402/polar.v32i0.20193