Ice Deformation and Ice Thickness Distributions Near SHEBA
R. W. Lindsay
Polar Science Center, Applied Physics Laboratory
University of Washington, Seattle, WA 98105
phone: 206-543-5409
email: lindsay@apl.washington.edu
This data set consists of daily estimates of the ice velocity, deformation, mean thickness,
the thickness distribution, thermal forcings, and the energy balance of the ice near SHEBA.
The data sources and methods are described in two accompanying papers to be published in the
Journal of Geophysical Research (in the files sheba_ice_deformation_paper.pdf and
sheba_ice_thickness_paper.pdf).
The estimates are of the 24 hour averages centered at mid day of the UTC clock and extend from
2 October 1997 to 6 October 1998, 370 days in all.
There are 5 data files. Each one begins with ascii header lines identifying the variables and
the units. The five files are
sheba_deformation,
sheba_mean_thickness,
sheba_thickness_distribution,
sheba_thermal_forcings, and
sheba_energy_balance.
Acknowledgements:
A large number of people have helped to collect and processes data used in this study. I thank
our colleagues in the SHEBA Atmospheric Surface Flux Group, Ed Andreas, Chris Fairall, Peter
Guest, and Ola Persson for help collecting and processing the flux tower data. I also thank
Don Perovich and the SHEBA Snow and Ice Studies Group for albedo, ice temperature, and pond
fraction measurements; Dick Moritz and all of the SHEBA Project Office Observers for their aid
in obtaining the SPO data; Bernie Zack and the Atmospheric Radiation Measurement Program
personnel for their radiative flux observations; M. McPhee, T. Stanton, and J. Morison for
Ocean temperature data; Mark Tschudi and the NCAR C-130 team for pond fraction data; Ron Kwok
and the Polar Remote Sensing Group at JPL for the RGPS data; and Yanling Yu and Drew Rothrock of
the Polar Science Center for the SCICEX ice draft data. This work has been funded by the
National Science Foundation Arctic System Science Program.
A brief description of each of the files follows
sheba_deformation
The velocities are relative to a grid that is aligned with the SSMI grid used by the RGPS, and
has the positive X axis pointed along 45E. The deformation is calculated for a scale of 100 km.
It is taken directly from the RGPS data set when the RGPS data are available. There are 370
days from day 275.5 to day 644.5
first 4 lines:
day year mnth dom lat lon u v shr div tot vrt uverr
deg deg km/day km/day %/day %/day %/day %/day km/day
275.5 1997 10 2 75.22 217.54 13.38 11.26 5.92 0.18 5.92 -10.48 0.20
276.5 1997 10 3 75.30 217.15 7.47 7.52 1.07 0.11 1.07 -1.77 0.20
day day from the start of 1997 (1 January 1997 is day 1)
year
mnth month
dom day of the month
lat latitude (deg N)
lon longitude (deg E)
u, v velocity components in the ssmi grid coordinate system (km/day)
shr shear (%/day)
div divergence (%/day)
tot total deformation = sqrt(shr2 + div2) (%/day)
vrt vorticity (%/day)
uberr velocity components uncertainty (km/day)
sheba_mean_thickness
The area fraction of open water, multiyear ice, new smooth ice, new ridged ice and their
thickness are given. Multiyear ice represents ice present at the beginning of the simulation.
There are 370 days.
first 4 lines:
day h_bar ow_frac my_frac sm_frac rd_frac my_thk sm_thk rd_thk
m m m m
276.5 1.543 0.000 0.943 0.056 0.001 1.629 0.094 0.647
277.5 1.549 0.000 0.933 0.063 0.004 1.647 0.142 0.798
day day from the start of 1997
h_bar mean ice thickness (m)
my_thk mean thickness of multiyear ice (m)
sm_thk mean thickness of new smooth ice (m)
rd_thk mean thickness of new ridged ice (m)
ow_frac open water fraction
my_frac multiyear fraction
sm_frac new smooth ice fraction
rd_frac new ridged ice fraction
sheba_thickness_distribution
The thickness distribution is given for 8 thickness bins and are separated into multiyear, new
smooth, and new ridged categories. There are 370 days.
h_low 0.00 0.50 1.00 2.00 3.00 4.00 6.00
h_high 0.50 1.00 2.00 3.00 4.00 6.00 20.00
day 275.5
ow 0.000
my 0.103 0.226 0.336 0.145 0.062 0.041 0.013
sm 0.067 0.000 0.000 0.000 0.000 0.000 0.000
rd 0.003 0.002 0.002 0.000 0.000 0.000 0.000
day 276.5
ow 0.000
my 0.100 0.226 0.335 0.144 0.062 0.041 0.013
sm 0.070 0.000 0.000 0.000 0.000 0.000 0.000
rd 0.006 0.000 0.003 0.000 0.000 0.000 0.000
day 277.5
h_low lower bound for each of 7 thickness bins (m)
h_high upper bound (m)
day day from the start of 1997
ow open water fraction
my fraction of multiyear ice in the first bin (0.01 to 0.38 m)
sm fraction of new smooth ice in the first bin
rd fraction of new ridged ice in the first bin
sheba_thermal_forcings
The thermal forcing values, obtained from observations at the camp, are given every 6 hours.
There are 1478 entries.
day wind_spd air_temp humidity shortwave longwave cloud_frac snow_depth pond_frac pond_depth
m/s C gm/kg W/m2 W/m2 m m
275.25 4.1 -13.6 0.0012 8.2 234.4 0.85 0.09 0.00 0.05
275.50 4.1 -14.0 0.0011 8.4 233.7 0.84 0.09 0.00 0.05
275.75 4.1 -14.3 0.0011 7.8 232.9 0.83 0.09 0.00 0.05
276.00 4.1 -14.7 0.0010 7.3 232.2 0.82 0.09 0.00 0.05
day day from the start of 1997
wind_spd 10-m wind speed (m/s)
air_temp 10-m air temperature (C)
humidity 10-m mixing ratio determined from the air temperature and a 100% relative humidity with respect to ice
shortwave downwelling shortwave radiative flux (W/m2)
longwave downwelling longwave radiative flux (W/m2)
cloud_frac cloud fraction from manual observations
snow_depth mean snow depth measured along the albedo line
pond_frac pond fraction from aerial observations
pond_depth pond depth from camp observations
sheba_energy_balance
The energy balance and ice growth rates were computed for 8 fixed ice-thickness categories.
The aggregate flux is the area-weighted average. The output is every 6 hours with 1478
entries.
first 17 lines:
h 0.00 0.25 0.50 1.00 2.00 3.00 4.00 8.00 aggregate
day 275.25
g 0.052 0.124 0.131 0.337 0.194 0.090 0.059 0.013
albedo 0.08 0.84 0.85 0.85 0.85 0.85 0.85 0.85 0.81
net_rad -67.34 -22.56 -21.37 -20.60 -20.33 -20.43 -20.42 -19.96 -23.29
sens_hf -236.54 -4.74 -1.04 1.15 1.75 1.44 1.45 2.70 -12.08
lat_hf -114.13 -1.60 -0.56 0.03 0.19 0.11 0.11 0.45 -6.15
btmflx 0.25 28.89 21.93 8.11 1.70 1.02 0.75 0.37 9.67
storage 0.00 -0.00 -1.04 -11.31 -16.69 -17.87 -18.11 -16.44 -10.07
growth 0.108 0.009 0.007 0.002 0.000 0.000 0.000 0.000 0.009
day 275.50
h thickness of each of 8 bins. These are particular ice thicknesses, not ranges
of thickness as in the thickness distribution file. The last column is
the aggregate (the average weighted by g).
day day from the start of 1997
g fraction of ice associated with each thickness
albedo albedo of each thickness'
net_rad Net radiative flux (W/m2)
sens_hf Sensitive heat flux (W/m2)
lat_hf Latent heat flux (W/m2)
btmflx Bottom heat flux (W/m2)
storage Storage heat flux (W/m2)
growth Growth rate of the ice (m/day)
Call if you have questions. Comments on the paper or data are welcome.
24 April 2002