The ocean surface height is constantly varying under the effects of gravity, density and the Earth's rotation. Information on the Ocean surface elevation in polar regions is available from the CryoSat2 Radar instrument. We compare ocean surface elevation to a static geoid product (GOCO03s) to give the part of the ocean surface elevation accountable due to surface currents, the Dynamic Ocean Topography (DOT). This measurement is smoothed over 100 km and gives monthly surface currents.
NERC NE/R000654/1 Towards a marginal Arctic sea ice cover.
Antarctic, Arctic, Ocean, surface currents
Heorton, H. (2022). UCL CPOM CryoSat2 derived Dynamic Ocean Topography 2011-2021 (Version 1.0) [Data set]. NERC EDS UK Polar Data Centre. https://doi.org/10.5285/930b782e-dfd2-4b7a-9a88-7cd03c024080
|Use Constraints:||Data released under Open Government Licence V3.0: http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/.|
|ISO Topic Categories:||
|Organisation||British Antarctic Survey|
|Name||Dr Harold Heorton|
|Organisation||University College London|
|Reference:||Armitage,T.W.K., S.Bacon, A.L.Ridout, S.F.Thomas, Y.Aksenov and D.J.Wingham (2016), Arctic sea surface height variability and change from satellite radar altimetry and GRACE, 2003-2014, Journal of Geophysical Research:Oceans, 121, https://doi.org/10.1002/2015JC011579.
Armitage, T.W.K., S.Bacon, A.L.Ridout, A.A.Petty, S.Wolbach and M.Tsamados (2017), Arctic Ocean surface geostrophic circulation 2003-2014, The Cryosphere, 11, https://doi.org/10.5194/tc-11-1767-2017.
|Quality:||This is a level 2 gridded data product that has gone under extensive data quality filtering.
Individual elevation measurements are filtered to be for the specific surface type (see above).
When gridding the elevation measurements we first trim off the lowest and highest 20th percentiles before calculating the mean.
The gridded data product has many missing values for land points where the data is inapplicable.
When smoothing the DOT surface we ignore all grid cells in the 1st and 99th precentile and leave these masked similar to a land point. These outlying cells can occur due to satellite altimeter encountering small islands not found in the land mask.
As we apply bias correction to the different satellite modes we have to be careful that the satellite was operating in its standard configuration. For example some months have data points in LRM mode where we usually expect SAR mode. These tracks have to be removed. This was performed manually.
|Lineage:||We take UCL CPOM processed CryoSat2 altimetry measurements of sea surface elevation, from the open ocean or from cracks within the sea ice cover. These records are from 4 satellite modes, LRM, SAR Ocean, SAR lead and SARIN lead. We take the UCL13 Mean Sea Surface product to calculate Sea Level Anomaly (SLA) for all 4 modes. We then calculate a monthly mean offset between, in order, LRM to SAR ocean, SAR ocean to SAR lead, SAR lead to SARIN lead, from coincident measurements on a 100 km resolution grid to remove mode bias' compared to the LRM mode SLA. We then use the GOCO03s geoid to calculate the dynamic ocean topography, then removing the bias from the SLA calculation. The DOT is smoothed over a 100 km Guassian kernel, with gradients to this field giving the surface monthly geostrophic currents. Data quality filtering is under taken at every step of the processing.|
|Horizontal Resolution Range||10 km - < 50 km or approximately .09 degree - < .5 degree|
|Vertical Resolution Range||N/A|
|Temporal Resolution||Monthly mean|
|Temporal Resolution Range||N/A|
|Data Collection:||CryoSat2 LRM, SAR and SARIN mode radar altimeter.|
|Data Storage:||A single NetCDF file for both the Arctic and Antarctic. The files contain metadata explaining each variable and time and spatial dimensions. Grid dimensions and local rotations are supplied within the file for orientating the currents and reprojection.|