Autonomous platforms
We are using autonomous platforms to obtain time series data throughout all seasons from the very remote regions in the Arctic and Antarctic. Our autonomous platforms, or more generally speaking ‘ice tethered platforms’, are installed on sea ice and in general send their data through satellite communication back home. We mostly deploy them as part of our ship and airborne campaigns and leave them behind to continue monitoring the atmosphere, snow, sea ice, and upper ocean. Often, we simply call them ‘buoys’ although most of these systems are not able to float and depend on solid ice.
We are using different types of platforms (see boxes below): The simplest platforms are position buoys that only report their own position and surface temperatures. These are the basis of our drifting observational networks to observe the ice motion and deformation of the ice pack. The more complex stations include various bio-physical sensors in and under the sea ice to measure ice and water properties, often combined with radiation measurements over and under sea ice.
Autonomous platforms have been deployed since the 1990’s. More than 400 platforms have been deployed since 2012 and are listed on Meereisportal.de; about 130 of those during the drift experiment MOSAiC.
More details on our ‘buoy program’ and live data is shown on Meereisportal.de.
Surface Velocity Profilers (SVPs) are designed to observe sea ice drift through GPS position measurements. The term “SVP” is used in various ways for many similar types of sensors utilized in ocean sciences, including a drogue to make the surface unit drift with the ocean currents and less with the wind. Our main application is to place the SVPs on sea ice to track the movement of a floe, but they may continue drifting in the ocean even after the floe has melted in summer. The GPS position is sent via Iridium at hourly intervals.
Snow Buoys (or snow height beacons) measure relative changes in snow height around the platform by means of four ultra-sonic snow depth sensors. Calibrated against the initial snow depths during deployment, these relative changes translate into absolute values. In addition, standard meteorological parameters are recorded, and the MET data along with the GPS position is sent via Iridium at hourly intervals.
Thermistor string buoys (also referred to as ice mass balance buoys, IMBs) measure temperature and thermal conductivity through air, snow, sea ice and seawater. A thermistor string features e.g. 240 embedded thermistors at a spacing of e.g. 2 cm (custom length/spacing also available). The temperature measurements and the response to cyclic heating of resistors enable the determination of snow depth and sea-ice thickness. The data are transmitted via Iridium at varying intervals.
Radiation stations consist of three sensors which are placed over and underneath sea ice to capture incoming, outgoing and transmitted radiation through the sea ice.
The work with autonomous platforms is a highly international effort, because we need to share expertise and logistics for developing, funding, deploying, and analyzing our buoys. In that respect we are strongly involved in the International Arctic Buoy Program (IABP) and the International Program on Antarctic Buoys (IPAB). Maps 2 and 3 show the distribution of deployed buoys since 2012.
