Sea Ice Temperature.
Project: Sea Ice temperature – LOMROG III
Date: August 23, 2012
Platform: Icebreaker Oden
Position: 89.66N; 130.60E
Weather: Clear sky, 6m/s, -1.8C
Persons: Gorm Dybkjær and Rasmus Tonboe
At 23:43 hours on August 22, the LOMROG III expedition reached the North Pole, on board the Swedish icebreaker Oden. The LOMROG III expedition is part of the Continental Shelf Project of the Kingdom of Denmark. The main objective is to acquire the data that are necessary to document an extension of the continental shelf beyond 200 nautical miles in the area north of Greenland.
Gorm Dybkjær and Rasmus Tonboe from the Centre of Ocean and Ice at the Danish Meteorological Institute were offered the opportunity to participate in the LOMROG III expedition with a research project. Their research project measure sea ice temperatures with different sensors at three levels: on the ice surface, from the top of the ship and from space, in order to improve satellite measurements from space. Oden provide a perfect platform for this work.
Measuring arctic sea ice temperature from satellite
Temperature of the snow surface and the snow-ice interface are vital parameters to understand the freezing and melting of sea ice. Measurements of these temperatures are not available through traditional observations, but only as proxy measurements from a scarcely distributed Arctic observation network. Information of the snow and the snow-ice temperatures from satellite observations can thus give important information about the vertical thermodynamics and thereby be essential for calculation of ice growth and melt and also assist in calibrating and validating the multilayer sea ice models in e.g. ocean and weather models.
However, it is not trivial to measure sea ice temperatures from satellite, because a number of conditions have to be accounted for. It is, for example, necessary to account for different states of snow, melt pond area and open leads in the sea ice. Further, in order to compare satellite measurements to in situ measurements one has to consider the effect from measuring at different scales. We have therefore planed a comprehensive fieldwork for the LOMROG III expedition, to investigate the influence and correlations between actual ice temperatures, satellite measurements and the terms that influence these measurements.
On the top deck of Oden, on ‘Monkey Island’, we have deployed instruments that are identical to some operating satellite instruments that cover the Arctic ocean on a daily basis. The instruments are thermal infra-red and microwave radiometers that measure the brightness temperatures of the sea ice. These two instruments in combination provide information on both the skin temperature and of the internal snow and sea ice temperatures. Along with these instruments we have also mounted an ordinary camera that continuously provides information of the fraction of water inside the field of view of the instruments. These satellite and ship borne instruments will be matched up with direct measurements directly from the ice, the so called in situ measurements.
To investigate melting and freezing processes of sea ice we have also deployed eight drifting buoys that are constructed to measure the temperature profile continuously, from the air above, through the snow and ice and into the ocean water. Via an iridium telephone connection these buoys will report bi-hourly on their position and temperature measurements.
These more or less synchronic measurements will be gathered in a data base. The subsequent analysis of the data will hopefully improve our understanding of snow and sea ice temperatures and melting/freezing processes in the Arctic. The new insight in the Arctic snow and ice conditions will help up to make better interpretation of the satellite measurements and eventually be yet another step to towards improving ocean and weather models and their prognosis skills.
This research is sponsored by a wide range of national and international R&D projects: Ocean and Sea Ice Satellite Application Facility (OSISAF, EUMETSAT), ESA SMOSice and cost action SMOS MODE (ESA, EU), Greenland Climate and Research Centre (The Danish Agency for Science, Technology and Innovation), MyOcean project (EU), NAACOS project (Danish strategic research council), GHRSST and ESA Climate Change Initiative.