This data set contains standardized, manual, visual ship-based sea-ice observations for the Southern Ocean, Antarctic. These are observations mainly from research ships navigating in sea-ice covered waters. These observations are carried out according to the ASPeCt protocol (http://www.aspect.aq).
The data set includes:
- date and time
- latitude, longitude
- a ship-cruise identifyer
- total sea-ice concentration
- concentration, ice type, ice thickness, ridged ice fraction, ridge height, surface type, snow depth for thickness category I (the thickest sea ice)
- concentration, ice type, ice thickness, ridged ice fraction, ridge height, surface type, snow depth for ice thickness category II (the 2nd thickest sea ice)
- concentration, ice type, ice thickness, ridged ice fraction, ridge height, surface type, snow depth for ice thickness category III (the 3rd thickest sea ice)
- sea water temperature, air temperature, wind speed, wind direction, visibility, cloud cover, weather, comment
Data are given for each ship cruise in chronological order. For temporally overlapping ship cruises data of the cruise starting first come first.
For times or geographic locations without observations and/or for cases where not all parameters listed above were observed, missing values are included.
Altitude: 0 m
(calendrical time coverage of data)
Creative Commons Attribution 4.0 International (CC BY 4.0)
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please see associated experiment and/or dataset group(s) for citation details.
This compilation of observational data has
Level 2b - Geophysical Variable - Basic Quality Control
The data set has been standardized in the sense that for all cruises the same number of columns exist and that for all parameters without a valid observation a missing value is included.
The data set has been successfully employed in the evaluation of sea-ice products (sea-ice concentration, sea-ice thickness) based on satellite observations.
Users of the data set should note the following:
1) Observations are carried out (usually) by a group of voluntary observers of varying experience and skills. It should be taken into account, therefore, that the same ice conditions might be observed differently by different observers. It is therefore recommended to NOT use this data on a point-by-point basis but, for instance, as an along-track daily average.
2) The accuracy of all parameters describing the sea-ice conditions is 5-10% for fractions, (2-)5-10 cm for snow depth, and (0.05-)0.1-0.3 m for sea-ice thickness and ridge height; the values in parenthesis denoting values for thin snow and thin sea ice.
3) Ships tend to follow easy-to-navigate sea-ice conditions. Therefore, basically all parameters can be expected to be biased towards conditions encountered in a lead and/or within level sea ice of the thinnest category encountered. Particularly, it can be expected that the snow depth and the sea-ice thickness is biased low year-round. Sea-ice concentrations are likely biased low during summer.
Approved by author, August 28, 2019
The data set comprises observations along ship-trajectories at irregular time intervals and at irregular distances between successive ship-based observations. As such this is an irregularly distributed data set in space and time. Typically, time differences between successive observations should be around one hour.
For the same date, observations from several cruises can exist.
Each single ship-based observation comprises the parameters listed in the summary. Parameters not observed, i.e. missing, are assigned a missing value. These missing values are constant for one parameter, e.g. the sea-ice thickness of ice of thickness category I, for the entire data set but they may vary between different parameters, e.g. between sea-ice thickness: -9.9 and sea-ice concentration: -9 or a missing comment: noval.
Each single ship-based observation of the sea-ice conditions likely represent different areas around the ship. The goal is to observe within a radius of one kilometer around the ship. However, ships' speed, visibility, sea-ice conditions, and experience of the observer result in an elliptically shaped observation area with a semi-minor axis close to one kilometer and a semi-major axis between an estimated 1 and 2.5 kilometers.