A cornucopia of oscillations on the Laptev Sea shelf

Abstract

The attributes of waves in the Laptev Sea that were present during 2018–2020 across a range of periods, are reported using time series constructed from long-duration, separate-year observations of sea level fluctuations made with two types of seafloor-mounted autonomous pressure recorders together with a single year of temperature measurements. In each case the data were sampled every second. Spectral analyses of the collected time series show that long waves with periods coinciding with the main diurnal harmonics of the tidal potential O1, K1 and semidiurnal S2 predominate in the sea level fluctuations, recognizing that critical latitudes can also strongly influence the generation and propagation of internal tides. Substantial fluctuations were also found corresponding to the main lunar semidiurnal harmonic M2 close to the latitude where the instruments were installed. Sea level fluctuations at a period of about 37.3 h were also apparent, identified as shelf waves using a previously-published model. Moreover, a significant decrease in sea level, up to 1.25 m, was detected on October 28, 2018, which is believed to be a negative storm surge because of the characteristic periods present in the feature. Analysis of water temperature fluctuations over the period range 30 min–24 h revealed peaks in the spectra with periods of several hours. Whilst unverifiable in the present case, similar water movements in the Laptev Sea have been attributed to internal waves arising as a result of the interaction of long surface gravity waves and shelf waves with its islands and coastal terrain, as well as baroclinic instability. Analysis of shorter period oscillations (12 s–120 min) is also carried out, which the authors ascribe to short (high-frequency) internal waves.