Sample map of the ICESat-data based Arctic sea-ice thickness distribution for the period October/November 2005.
The data are available via this link.
Travel time measurements of laser pulses emitted by the GLAS instrument aboard the ICESat satellite allow the determination of the sea-ice freeboard height with centimeter accuracy. Under certain assumptions and taking additional data like the distribution of multiyear ice and the snow depth on sea ice into account (see references), the freeboard height can be converted into an ice thickness.
The data set available here comprises data from 10 ICESat measurement periods, i.e. a time series of two measurements of the Arctic sea-ice thickness distribution every winter (October/November and February/March) for winters 2003/04 until 2007/08 with a grid resolution of 25 km x 25 km.
|Sea ice thickness||cm|
Period and temporal resolution:
These are data from selected ICESat-GLAS sensor measurement periods for years
- 2003 to 2008, two measurement periods per year: fall and late winter
- quasi-monthly (about 35 days)
This data is a mean / composite over the considered ICESat measurement period. The exact duration of these period is given in Kwok et al., 2009 (see references); typically the periods comprise 35 days in February/March (2007: March/April) bzw. October/November (2003: September-November).
Coverage and spatial resolution:
- Northern hemisphere
- Spatial resolution: 25 km x 25 km, polar-stereographic grid of the NSIDC, centered at 70°N
- Geographic longitude: 0°E to 360°E
- Geographic latitude: about 60°N to 90°N
- Altitude: 0.0 m
Data are stored as 4byte floating point values. The header contains the number of grid cells with valid values (2byte integer), followed by geographic latitude and longitude, x and y, and the ice thickness; x and y are the distance (in km) of the center of each grid cell to the center of the NSIDC grid.
A routine (IDL) to read, display and store the data as an image can be downloaded here.
This data give a measure about the mean monthly Arctic sea-ice thickness distribution at two points during the seasonal cycle: October/November, i.e. about one month after freeze-up has started, and February/March, i.e. when sea ice extent is at its maximum but sea-ice thickness will continue to increase for 1-2 months.
The data set does not contain error estimates
Kwok et al. found a mean uncertainty of the sea ice thickness of about 0.7 m using an error propagation. Sea-ice draft estimated from ICESat data on the one hand and measured at mooring on the other hand agree within 0.5 m.
However, it can be expected that the uncertainty can be considerably higher than the two numbers given above, because of the used assumptions and because of gaps in our knowledge concerning snow properties as its depth and their variability.
We recommend to take a look at the references and/or get into discussion with us or Ron Kwok directly.
Jet Propulsion Laboratory, Pasadena, CA, U.S.A.
email: Ronald.Kwok (at) jpl.nasa.gov
ICDC / CEN / University of Hamburg
email: stefan.kern (at) uni-hamburg.de
- Kwok, R., G. F. Cunningham, H. J. Zwally, and D. Yi (2007), Ice, Cloud, and land Elevation Satellite (ICESat) over Arctic sea ice: Retrieval of freeboard, J. Geophys. Res., 112, C12013, doi:10.1029/2006JC003978.
- Kwok, R., and G. F. Cunningham (2008), ICESat over Arctic sea ice: Estimation of snow depth and ice thickness, J. Geophys. Res., 113, C08010, doi:10.1029/2008JC004753.
- Kwok, R., G. F. Cunningham, M. Wensnahan, I. Rigor, H. J. Zwally, and D. Yi (2009), Thinning and volume loss of the Arctic Ocean sea ice cover: 2003–2008, J. Geophys. Res., 114, C07005, doi:10.1029/2009JC005312.