Characterizing horizontal variability and energy spectra in the A rctic O cean halocline

Energy transfer from the atmosphere into the upper Arctic Ocean is expected to become more efficient as summer sea‐ice coverage decreases and multiyear ice thins due to recent atmospheric warming. However, relatively little is known about how energy is transferred within the ocean by turbulent processes from large to small scales in the presence of ice and how these pathways might change in future. This study characterizes horizontal variability in several regions of the Eurasian Arctic Ocean under differing sea‐ice conditions. Historic along track CTD data collected by a Royal Navy submarine during summer 1996 allow a unique examination of horizontal variability and associated wavenumber spectra within the Arctic Ocean halocline. Spectral analysis indicates that potential energy variance under perennial sea‐ice in the Amundsen Basin is O (100) less than within the marginal ice zone (MIZ) of Fram Strait. Spectra from all regions show a transition in scaling at wavelengths of approximately 5–7 km. At scales greater than the transition wavelength to 50 km, energy spectra are consistent with a k −3 scaling (where k is a wavenumber) and interior quasigeostrophic dynamics. The scaling of spectra at these scales is extremely similar between regions suggesting similar dynamics and energy exchange pathways. The k −3 scaling is steeper than typically found in regions of midlatitude open ocean. At scales below the transition wavelength to 300 m, spectra are close to a k −5/3 scaling or flatter, indicating a change in dynamics, which is potentially due to internal waves dominating variability at small scales. Arctic energy spectra are steeper than those from midlatitude open oceans Energy variance is O (100) less in perennial compared to marginal sea‐ice Spectra suggest similar physical dynamics in perennial and marginal ice