- How is the data set organized?
- Do you have data to submit?
Sea ice thickness is, perhaps, the most important climate state variable that is currently poorly observed, poorly documented, and poorly archived. We as a community can do much better and a unified sea ice thickness data set is an important step forward. This new archive will be a valuable baseline and a continuously growing resource for ongoing work by many groups in understanding, predicting, and adapting to changes in the polar regions.
While ice extent is well measured by satellite, monitoring ice thickness has been and remains a challenge. However the amount of ice draft and satellite data available in the last few years from both polar regions has increased markedly, providing a large and growing resource. Existing observations of ice thickness span a variety of methods, accuracies, and temporal and spatial scales and are archived in a variety of different locations and in different formats. Each has its own strengths in terms of sampling or accuracy. The uncertainties are documented to various levels of detail for the different data sources but the documentation in general is spread throughout the literature.
This new data set is a concerted effort to collect as many observations as possible in one place, with consistent formats, and with clear and abundant documentation. It will allow the community to better utilize what is now a considerable body of observations. With a variety of data in one location and format, it will be much easier to compare the different sources with each other and with model output. The increased space and time coverage of a unified dataset will facilitate improved analyses of how and where sea-ice thickness has changed over the last three decades. This data set targets the wealth of data that are now available from moored and submarine-based upward looking sonar (ULS) instruments, airborne electromagnetic (EM) induction instruments, and satellite laser altimeters (ICESat). These instruments offer adequate sampling dating from 1975 to establish the mean ice thickness and thickness distribution for scales generally appropriate for change detection and climate model validations.
This archive includes, or points to, both point measurements as acquired from the data providers and average values. The average values provide easy access for the change detection and modeling communities and consist of one-month averages of moored ULS data or 50-km averages of submarine, airborne, or satellite data. (Roughly 50 km of ice passes over a typical mooring site in a month and monthly output is commonly saved in model runs.)
The following is a partial list of data sources that are or will be included in the new unified data set:
Submarine ULS data: Over 120,000 km of tracks of ice draft have been processed for the Arctic Ocean since 1975 from both US and UK submarines.
North Pole Environmental Observatory (NPEO): An oceanographic mooring has been continuously deployed at the North Pole in more than 4000 m of water since the spring of 2001.
Institute of Ocean Sciences (IOS): IOS has deployed a series of ULS instruments in and around the Mackenzie Delta, in Nares Strait and in the eastern Beaufort Sea under the direction of Dr. Melling. Also, NOAA supported IOS in the deployment of a ULS-equipped mooring on the Chukchi Shelf in 2004—2005.
Woods Hole Oceanographic Institute (WHOI): The Beaufort Gyre Exploration Project, under the leadership of Dr. Proshutinsky, has deployed 3 to 4 moored ULS instruments in the deep water of the Beaufort Sea since 2003.
Alfred Wegener Instititute (AWI): AWI has deployed moored ULS instruments in both the Arctic, primarily in Fram Strait, and in the Antarctic, primarily in or near the Weddell Sea (starting in 1990).
University of Alberta: Dr. Christian Haas has made a number of helicopter-borne surveys of the ice thickness with an electromagnetic induction (EM) instrument in both the Arctic and in the Antarctic.
ICESat Satellite data: (not yet included) ICESat laser-altimeter freeboard measurements and ice thickness estimates are available sporadically from 2003 to 2009.
As seen above, the ice thickness data comes from many different sources, each with its own measurement and processing methods. Each source has its own page in this web site which can be found under the "sources" button at the top. Each source typically has data from multiple moorings, submarine cruises, or field campaigns, but all are closely related by methodology and processing.
The data from each platform or cruise is averaged into one-month or 50-km samples. Two separate files are made for all the samples from each source, one with a summary of the measurement time and location and the mean, minimum, maximum, and standard deviation of the basic measurement, be it draft, thickness, or freeboard. Additional statistics are included for the meaurement depth or height and the water temperature. A second file includes the full ice draft or thickness distribution (the probability distribution function, or pdf) of the measurement in 300 bins, each 10 cm wide. Both of these files can be accessed from the source web pages or through the Data Table page.
Finally there are metadata files that list various information about each platform. These are given in an Excel spread sheet in which each source has a worksheet and each mooring or cruise a column. It can be accessed either through the source page or the Data Table page.
We are looking for any ice thickness observations that provide an estimate of the ice thickness distribution. Please contact us if you have some data you would like to have included here.
If you use data from this data set please cite both this data set and the individual data providers, as indicated on each source page. For this data set use:
Lindsay, R. W., 2010: Unified Sea Ice Thickness Climate Data Record, Polar Science Center, Applied Physics Laboratory, University of Washington, psc.apl.washington.edu/sea_ice_cdr, digital media.
Ron Lindsay, email: lindsay at apl.washington.edu
Comments and suggestions are welcome.
This project is supported by the NOAA Climate Program Office, Climate Change Data and Detection Program .