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Accessing Production Data

The data products are today accessed via local partner data portals as follows:
 
For Surface Elevation Change (SEC) enter the UCL driven CPOM data portal SEC products are provided as part of the UK CPOM Data Portal URL: http://www.cpom.org/data. The CPOM data portal provides a set of operational cryosphere earth observation data products which include Antarctic SEC products (from the ESA CCI and CPOM research output), near real time sea ice thickness and Antarctic ice sheet velocity. All CPOM portal sites provide additional user friendly functions to visualise product maps and climate variable time series. For the Antarctic SEC portal, time series and maps of SEC and related parameters can be viewed for each Antarctic drainage basin and ice sheet area. Full access to SEC CCI product downloads is available following a simple user registration step and site login. 
 
For Ice Velocity (IV) and Grounding Line Location (GLL) enter the CryoPortal URL: http://cryoportal.enveo.at/. The portal is operated by ENVEO and provides free access to cryospheric products and services from satellite data for Antarctica and Greenland, as well as various ice caps and glaciers. Products are generated by ENVEO and partners within projects funded by ESA, FFG/BMVIT, European Commission and others. The data portal can be used for browsing, distributing, downloading and simple analysis of data products (e.g. IV profile generation along glacier center lines, mass flux analysis etc.). To get full access to services and download capability of products requires registration and login. There are different user levels (anonymous, external, partner & staff) that determine the permissions for reading and accessing the data. These can be adjusted for each product individually. Currently it is possible to download a number of IV and GLL products generated for AIS CCI by ENVEO and DLR respectively.
 
For Gravimetric Mass Balance (GMB) enter the data portal hosted by TU Dresden URL: https://data1.geo.tu-dresden.de/ais_gmb. User-friendly functionalities allow to interactively browse and explore both the GMB basin and the GMB gridded product. 
Mass change time series for individual drainage basins can be displayed by selecting the basin of interest from a map. The time series plot allows to zoom to a certain period and to query values for a specific monthly solution. The plot can be saved in raster (png) and vector (svg) format.
An animation of the monthly grid series is available to visualise the GMB gridded product. By selecting a particular month from the plot of the mass change time series for the entire AIS, the corresponding monthly grid is displayed.
Before downloading one of the data sets provided, the user needs to enter his personal details. Downloading the data implies the user’s consent to cite the data set whenever results based on the GMB products are published.
 

Surface Elevation Change (SEC) 

Satellite altimetry is a key method used for assessing the sea level contribution from the polar ice sheets by measurements of their volume change. The technique is unique in  spatially resolving the detailed pattern of mass imbalance, with monthly temporal sampling, and has been applied to both the Greenland and Antarctic ice sheets. Thanks to a succession of ESA satellite missions starting with ERS-1 in 1992 and continuing with CryoSat-2, satellite altimetry provides the longest unbroken record of ice sheet mass balance from all geodetic techniques. Altimeter measurements of elevation change are extremely precise, because they require only modest adjustments to account for sensor drift, changes in the satellite attitude, atmospheric attenuation, and movements of Earth’s surface. The Antarctic_Ice_Sheet_cci project will produce a continuous monthly time series of surface elevation change measured using over 25 years of radar altimetry satellites including ERS-1/2, ENVISAT, CryoSat-2 and in the future, Sentinel-3.
 

Ice Velocity (IV)

There is ample evidence indicating large and rapid changes of the Antarctic Ice Sheet (AIS) in recent decades, including the break-up of several large ice shelves followed by glacier acceleration and retreating grounding lines, resulting in increased ice discharge and contributing to sea level rise.
Mapping glacier velocity and temporal changes in flow velocity provides key information for investigating the dynamic response of glaciers and ice sheets to changing boundary environmental conditions.
 
Remote sensing techniques that utilize SAR and optical satellite data are the only feasible manner to derive accurate surface velocities of the remote Antarctic glaciers on a regular basis. For this purpose several techniques have been developed  over the years including offset tracking and SAR interferometry. With the launch of the first satellite of the European Sentinel-1 SAR satellite series in April 2014, glaciologists are provided with a new tool to remotely measure ice flow velocity.
 
Archived and new repeat SAR data from Sentinel-1 and other sensors, including ALOS PALSAR and the ERS and TerraSAR-X mission will be used to derive ice flow velocity of several key regions in Antarctica. Combined these data sets allow for a unique assessment of ice-velocity changes in recent years.
 

Gravimetric Mass Balance (GMB)

The Gravimetric Mass Balance products are based on the GRACE (Gravity Recovery and Climate Experiment) satellite mission and respond to the high priority for mass balance parameters identified in the user survey.
 
GRACE gravity observations have the advantage of their direct sensitivity to change in the total ice sheet mass, including fluctuations in snow and ice (rather than geometry changes) on an approximately monthly time resolution, though with intrinsic limits in spatial resolution.
 
GRACE has been operating since 2002, and the GRACE-Follow-On mission scheduled for launch in 2017 will ensure continuity with enhanced accuracy and resolution.
 
Two products will be developed and produced:
time series of monthly mass changes for individual drainage basins, and
gridded mass changes over the entire ice sheet.
 
The second product will illuminate the spatial patterns of mass changes at a formal resolution of 50-100 km, although the actual physical resolution of GRACE is rather on the 200 km level.
 

Grounding Line Location (GLL)

The location of the transition where the ice resting on bedrock detaches and becomes a floating ice shelf is a critical parameter needed for calculations of the ice sheet mass budget, as well as for modelling ice ocean interactions, ice sheet dynamics, subglacial melt and oceanic tides. Due to its importance the grounding line position is one of the key parameters of the ice sheets which have been derived from satellite observations within the project.
 
The retrieval of the grounding line position is based on the influence of the ocean tides on the floating part of the ice which rests in hydrostatic equilibrium. Due to the fact that this tidal rise is absent on the grounded part of the glacier, a vertical deformation appears in the transition area.
 
The InSAR double differencing method (DInSAR) has been identified to be one of the most accurate techniques for locating the vertical tidal deformation of the ice sheet. At least two pairs of coherent repeat pass data sets must be combined in order to remove the common velocity component revealing the vertical component due to tidal motion. In practice the major limiting factor of this technique is the availability of datasets with sufficiently high InSAR coherence. Physical phenomena such as snow accumulation, drift, or melting may significantly change the surface properties between the satellite passes and thus the backscatter behaviour which can lead to loss of phase coherence in the interferograms.
 
The deformation of the grounding zone appears in the double difference interferogram as a dense fringe belt which represents height changes due to ocean tides and air pressure differences between the SAR acquisitions. In order to obtain the grounding line location (GLL), the upper flexure limit needs to be detected and mapped. The difficulty lays hereby in the recognition of the deformation region and the conversion of the classified pixel based area into a polygon. The GLL will be derived on selected key ice streams and glaciers identified by the science community.