Amplitude and Coherence of Inertial Motions in Arctic Sea-Ice for a Range of Sea-Ice States

We investigate how measuring inertial motion in Arctic sea ice can provide insight into the mechanical state of the ice pack. Inertial oscillations in sea ice have been observed and studied for several decades. In recent years, studies have emerged which attempt to use the amplitude of observed oscillation as a proxy for the degree of mechanical stress present in the ice pack. Towards this end, a parameter has been developed that measures the magnitude of inertial motion relative to forcing. Using position data with high temporal resolution from buoys deployed concurrently in sea ice in the Beaufort Sea, we examine this parameter, with a particular interest in discerning the relationship between inertial motion and sea-ice concentration. Furthermore, the coherence of inertial motion between pairs of buoys is studied over a range of separation distances. An inverse relation is observed between ice concentration and normalized amplitude of inertial motion. While in general the coherence of inertial motion is inversely correlated with separation distance, events are observed when distant buoys undergo coherent inertial oscillations. The utility of measuring inertial oscillations for inferring mechanical strength of the ice pack is discussed.