A Continuous Time Series of Observations Between the North Pole and Fram Straight Since 2011 From the Ice-T (Ice Thickness) Buoy

Frederic Vivier, CNRS, LOCEAN-IPSL, UPMC, Sorbonne Université, Paris, France, Antonio Lourenco, CNRS, LOCEAN-IPSL, UPMC, Sorbonne Université, France, Denis Dausse, CNRS & University of La Rochelle, Lab LIENSs, La Rochelle, France, Theophile Lebrun, LOCEAN-IPSL, UPMC, Sorbonne Université, Paris, France, Felicien Bonnefoy, LHEEA, Ecole Centrale Nantes, Nantes, France and Alain Weill, CNRS, LATMOS-IPSL, UPMC, Sorbonne Université, Paris, France
The Arctic is a key player of the ongoing climate warming. Sea-ice extent and thickness have shrunk substantially during the past decades, and recent observations indicate that these changes outpace climate models predictions.

Models indeed need observations. These are necessary for a better determination of the background state, but also to improve the parameterization of exchanges at the ocean-ice-atmosphere boundaries. Satellite observations provide a particularly relevant information given their space-time coverage. But while sea-ice extent is routinely monitored from space, remote sensing of ice thickness, although promising, is still in its early stage and requires in-situ observations for calibration and validation.

Here we present observations from the “ Ice-T ” (Ice-Thickness) buoy deployed every spring at the North Pole since 2011, as part as the North Pole Environmental Observatory, among a cluster of complementary instruments drifting towards Fram Straight.

The Ice-T buoy provides automated measurement of the different parameters pertaining to the local sea-ice mass balance. The instrument is buoyant and thus intended for both thin and thick ice conditions. The buoy currently measures ice thickness, thermal profiles within the ice and snow layers, and allows as well to estimate the snow load. It also measures currents at the base of the ice, which, combined with salinity and temperature data, makes it possible to estimate the ocean-ice heat flux. Additional sensors provide basic meteorological parameters and all data are real-time transmitted through the Iridium communication system.

As an option, a prototype meteorological mast (“BEAR”, Budget of Energy for Arctic Research) can be mounted on the top of the buoy to estimate turbulent and radiative heat fluxes, components of the surface energy budget needed to close the sea-ice mass balance. However, frosting remains a challenging issue for radiative measurements.

Recent developments include an IMU for sea-state measurements in the presence of ice. Waves penetrating hundreds of kilometers into the ice pack have been recorded.

Ongoing developments focus in particular on direct estimates of snow thickness, embedding a millimeter-wave radar sensor, which is of substantial interest for the validation of Arctic-dedicated satellite missions.