Regional high-resolution fast ice maps - Satellite synthetic aperture radar (SAR) data

This dataset comprises high spatial- and temporal-resolution maps of coastal landfast sea ice (fast ice) distribution in the vicinity of the Cape Darnley Polynya in East Antarctica, in the June-November (winter-spring) periods of 2008 and 2009. The maps were derived from cross-correlation of pairs of spatially-overlapping Envisat Advanced Synthetic Aperture Radar (ASAR) images, using a modified version of the IMCORR algorithm to determine vectors of sea-ice motion (as described in Giles et al., 2011). Fast ice is then distinguished from moving pack ice by the fact that it is stationary. The raw ASAR WSM data (swath width 500 km) were processed using ENVI image processing software to produce geo-referenced images with a 75m pixel size. Use of SAR data ensures coverage uninterrupted by cloud cover or polar darkness.

Image pairs were chosen with a time separation between 2 and 21 days. IMCORR processing of the image pairs for mapping fast ice follows Giles et al (2011) – using a reference tile size of 32x32 pixels and a search tile size of 64 x 64 pixels. A land mask was applied to avoid contamination from matches on stationary features over the continental ice sheet. The grid spacing was set to 16 x 16 pixels, so the images were over-sampled by a factor of 2 to provide a more dense set of results.

Stationary fast ice vectors were chosen from the IMCORR results using a combination of the cluster search technique and a variation of the z-axis threshold technique as detailed in Giles et al (2011). The cluster search technique was applied to the IMCORR results from each image pair to derive the initial set of valid vectors – this set could contain both stationary fast ice vectors and non-stationary pack ice vectors. Due to registration errors in the image pairs, the stationary vectors will not necessarily be centred around zero, so using a simple window around the zero offset mark to differentiate the fast ice vectors was not possible. To select the stationary vectors, a 2D histogram was constructed from the X-Y vector displacements, and a 2D Gaussian was fitted to this histogram. The fast ice vectors will dominate because of the large image pair time separation and small search tile size, so the Gaussian peak should correspond to the centre of the stationary fast ice vectors. All vectors that are within 5 standard deviations of the Gaussian peak are tagged as valid fast ice vectors. This is a minor modification to the method of Giles et al (2011), who used a simple threshold cut on the z-axis of the 2D histogram to define the fast ice vectors.

Data format – one fully annotated (self-describing) netCDF file per image pair containing latitude/longitude coordinates of the stationary fast ice vectors.

This technique and dataset complement a lower resolution but longer-term dataset (2000-2014) derived from satellite MODIS visible and thermal infrared data. (AAS_4116_Fraser_fastice_mawson_capedarnley).

Identification info

Alternate title: Regional high-resolution fast ice maps - Satellite synthetic aperture radar (SAR) data

Date (Publication): 2019-11-19

Edition: 1

Citation identifier

Dataset DOI

Title: Information and documentation - Digital object identifier system

Date (Publication): 2012-04-23

Citation identifier: ISO 26324:2012

Citation identifier: doi:10.26179/5dd33c1c8e55d

Originator

Hyland, G., Massom, R. and Heil, P.

Publisher

Australian Antarctic Data Centre

Principal investigator

HYLAND, GLENN

Australian Antarctic Division

203 Channel Highway

Kingston

Tasmania

7050

Australia

Principal investigator

MASSOM, ROB

Australian Antarctic Division

203 Channel Highway

Kingston

Tasmania

7050

Australia

0362323133

Principal investigator

HEIL, PETRA

Antarctic CRC

GPO Box 252 - 80

University of Tasmania

Hobart

Tasmania

7001

Australia

+61 3 6232 3124

Collaborator

HYLAND, GLENN

Australian Antarctic Division

203 Channel Highway

Kingston

Tasmania

7050

Australia

Name: CAASM Metadata

Website: https://data.aad.gov.au/metadata/records/AAS_4116_Fast-Ice-SAR

Purpose: The purpose of this dataset was to develop an algorithm to derive high spatial- and -temporal resolution maps of fast ice from time series of satellite SAR data in specific regions. Provision of the data in support of the Japanese Cape Darnley Polynya project (involving Australian collaboration).

Status: Completed

Custodian

AU/AADC > Australian Antarctic Data Centre, Australia - AADC, DATA OFFICER (DATA CENTER CONTACT)

Australian Antarctic Division

203 Channel Highway

Kingston

Tasmania

7050

Australia

+61 3 6232 3244

+61 3 6232 3351 (facsimile)

Spatial resolution

Spatial resolution: 75

Temporal resolution: P2D

Topic category

Oceans
Climatology, meteorology, atmosphere

Extent

Description: Temporal Coverage

Temporal extent

TimePeriod: 2008-05-01 2008-11-30

Extent

Description: Temporal Coverage

Temporal extent

TimePeriod: 2009-05-01 2009-11-30

Title: Semi-automated feature-tracking of East Antarctic fast ice and pack ice from Envisat ASAR imagery

Date (Publication): 2011

Citation identifier: 115