Date (Creation)

2023-04-11

Date (Revision)

2023-04-11

Date (Publication)

2023-04-11

Date (released)

2023-04-11

Edition

1.0

Unique resource identifier

https://doi.org/10.5285/d56d9e3f-80d2-4076-9e70-24f662c0e362

Codespace

doi

Unique resource identifier

GB/NERC/BAS/PDC/01732

Codespace

https://data.bas.ac.uk/

Other citation details

Please cite this item as: Smith, R., & Bigg, G. (2023). Positions and dimensions of the A68 icebergs between September 2020 and April 2021 (Version 1.0) [Data set]. NERC EDS UK Polar Data Centre. https://doi.org/10.5285/d56d9e3f-80d2-4076-9e70-24f662c0e362

Credit

No credit.

Status

Completed

Point of contact

Organisation name	Individual name	Electronic mail address	Role
British Antarctic Survey	Smith, Roseanne		Author
University of Sheffield	Bigg, Grant		Author
NERC EDS UK Polar Data Centre		PDCServiceDesk@bas.ac.uk	Point of contact

Maintenance and update frequency

As needed

Maintenance note

Completed

Global Change Master Directory (GCMD) Science Keywords

• EARTH SCIENCE > Cryosphere > Glaciers/Ice Sheets > Icebergs
• EARTH SCIENCE > Cryosphere > Sea Ice > Icebergs
• EARTH SCIENCE > Oceans > Sea Ice > Icebergs

Theme

• A68

• Icebergs

• South Georgia

• satellite observations

• trajectories

Place

• Scotia Sea, South Georgia and the South Sandwich Islands, South Atlantic South Sandwich Islands

GEMET - INSPIRE themes, version 1.0

• Elevation
• Oceanographic geographical features

Access constraints

Other restrictions

Other constraints

no limitations to public access

Access constraints

Other restrictions

Other constraints

no limitations

Use constraints

License

Other constraints

Open Government Licence v3.0

Use constraints

Other restrictions

Other constraints

Data supplied under Open Government Licence v3.0

Use constraints

Other restrictions

Other constraints

No restrictions apply.

Unique resource identifier

url

Codespace

url

Association Type

Cross reference

Unique resource identifier

url

Codespace

url

Association Type

Cross reference

Unique resource identifier

url

Codespace

url

Association Type

Cross reference

Spatial representation type

Text, table

Language

English

Character set

UTF8

Topic category

• Oceans

Begin date

2020-09-01

End date

2021-04-16

Supplemental Information

It is recommended that careful attention be paid to the contents of any data, and that the author be contacted with any questions regarding appropriate use. If you find any errors or omissions, please report them to polardatacentre@bas.ac.uk.

Title

European Petroleum Survey Group (EPSG) Geodetic Parameter Registry

Date (Publication)

2008-11-12

Cited responsible party

Organisation name	Individual name	Electronic mail address	Role
European Petroleum Survey Group		EPSGadministrator@iogp.org	Publisher

Unique resource identifier

urn:ogc:def:crs:EPSG::3031

Version

6.18.3

Hierarchy level

Dataset

Statement

Methodology:

The daily centre-point positions of the A68 icebergs, recorded as decimal degrees, were tracked using MODIS Aqua and Terra optical imagery displayed through NASA's EOSDIS Worldview tool ( https://worldview.earthdata.nasa.gov/). Where cloud cover precluded accurate iceberg positioning for a single day, the coordinates were interpolated based on the positions of the preceding and subsequent days, assuming constant speed. For the parent iceberg A68A, the positions of the two ends of the iceberg's major (long) axis are also provided, to give a sense of the iceberg's evolving orientation.

Lengths of A68A's major and minor axes, and area, were obtained using Synthetic Aperture Radar (SAR) data acquired by the European Space Agency (ESA) Copernicus Sentinel 1A and 1B satellites ( https://scihub.copernicus.eu/). The dates and file codes of the 11 SAR images used are provided. The major axis is defined as two most distal points on the iceberg; the minor axis is 90 degrees perpendicular and at the widest point.

Data collection:

Positions were obtained using MODIS Aqua and Terra optical imagery displayed through NASA's EOSDIS Worldview tool ( https://worldview.earthdata.nasa.gov/).

Dimensions were obtained using 11 SAR images acquired by European Space Agency (ESA) Copernicus Sentinel 1A and 1B satellites and downloaded from https://scihub.copernicus.eu/. The SAR data were viewed and measurements performed using ArcGIS (version 10) software.

Data quality:

Where cloud cover precluded accurate iceberg positioning for a single day, the coordinates were interpolated based on the positions of the preceding and subsequent days, assuming constant speed. This occurred for less than 10 percent of the positions noted for each iceberg, and the error introduced is expected to be minimal, owing to the very large size of the tracked icebergs, and known currents, throughout the study period.

For the parent iceberg A68A, cloud cover prevented continuous daily tracking in the two final weeks of its lifetime, in April 2021. Owing to the relatively small size of this final remaining iceberg at this time, and the large (3-4 days) gaps in observations, the missing positions were not interpolated for this final period and instead are left unknown. This results in 'snapshot' positions in the final two week period, until the iceberg's final melt on 2021-04-16.

Wherever data is missing (due either to lack of interpolation as described, or more commonly due to an iceberg's non-existence on that day), a value of 9999 is provided for ease of filtering.

Metadata

File identifier

d56d9e3f-80d2-4076-9e70-24f662c0e362 XML

Metadata language

English

Character set

UTF8

Hierarchy level

Dataset

Hierarchy level name

dataset

Date stamp

2023-04-11

Metadata standard name

ISO 19115 Geographic Information - Metadata

Metadata standard version

ISO 19115:2003(E)

Metadata author

Organisation name	Individual name	Electronic mail address	Role
NERC EDS UK Polar Data Centre		polardatacentre@bas.ac.uk	Point of contact