Observation of spatiotemporal variability of deep near-inertial waves in the western Arctic Ocean 

<p>A current- and pressure-recording inverted echo sounder (CPIES) placed on the sea floor observes physical ocean environment from months to years. Recently, a new technology was developed to collect high-resolution observational data remotely from CPIES using a popup-data-shuttle (PDS) through Iridium satellites. Remotely retrieved direct measurements of near-bottom currents in 30-minute intervals from an array of six PDS-CPIES deployed in the western Arctic Ocean reveal spatiotemporal variabilities of deep near-inertial waves (NIW). The deep NIW activity distinguishes energetic and calm NIW periods in July&#8211;December and in January&#8211;June, respectively. At the southernmost site in the Northwind Abyssal Plain, the NIW energy level during the energetic NIW period is around 10 times higher than during the calm NIW period. Comparison with the surface sea-ice changes suggests that the energetic deep NIW is significantly related with sea-ice reduction during the summer months. Site-dependent thickness of the near-bottom mixed layer causes rapid vertical decay of NIW activity close to the seabed, explaining notable differences in the observations between two of the sites. This study implies that investigating of the propagation and dissipation of NIW can help a better understanding of the evolving physical environmental changes of the Arctic Ocean interior caused by the recently accelerated decline of sea ice in the Arctic.</p>