DOI: 10.5285/0313090c-373e-4e2e-97f2-6cd0d4138e75
title: South Orkney Fast-Ice Series (SOFI) - Version 2.0

description: The South Orkney Fast-Ice series (SOFI) is an annual record of the timing of formation and breakout of fast-ice in Factory Cove, Signy Island, in the South Orkney Islands on the Scotia Arc in the northern Weddell Sea, Antarctica. Fast-ice formation and break-up has been studied at the South Orkeny Islands since the early 1900s, with this dataset covering the period of 1903 to 2019. This dataset is produced by personnel from the British Antarctic Survey, in efforts to study sea-ice variability in the Southern Hemisphere. Data was collected using various methods over the reporting period, namely an offset date from Laurie Island's fast-ice, direct observation, and with camera equipment. This is an updated version (2.0) of the dataset, that includes data from 2008 to 2019.
description: As the dataset covers a large temporal range, data was collected using several methods. To estimate ice formation and breakup at Signy Island prior to 1947, before observations at Factory Cove on Signy started, a mean offset from the dates of ice formation and breakup at Laurie Island, Scotia Bay, was used. The offset was determined by comparing both datasets during an overlapping observation period, from 1947 to 1975. The mean offset was then applied to determine the dates of ice formation and breakup at Signy. Cross-calibration was done using a geometric regression (Murphy et al 1995; Murphy et al 2014). Between 1947 and 1994, direct observation at the Signy Island station (Factory Cove) was used to determine ice formation and breakup. During the austral winter, ice formation was slow, and researchers estimated the official date of ice-formation as when the ice could support the weight of a 'typical scientist' (Murphy et al 1995; Murphy et al 2014). The ice strength was first tested with a threshold of blows using various physical tools, dependent on the season. The end-date for ice-break-up was determined as always equal to or later than when consolidated pack-ice around the South Orkney Islands departed. This was because the ice did not melt at Factory Cove, and thus was dependent on pack-ice departure. Ice-break up was also determined by direct observation from researchers at Factory Cove (Murphy et al 2014). From the 1994/1995 austral summer onwards, data was collected using an automatic camera system with 35mm film. The system was mounted at Observation Bluff to look over Factory Cove. It took one photo per day, where clear images of formation and breakout periods were analysed to assess the date of ice formation and breakup. Some images were not usable as there was occasionally ice on the camera during the winter. Formation and breakup were defined as the latest day Factory Cove froze over and the day when it cleared completely, respectively. Short periods of open water were ignored. Since 2013, a new camera system was installed, using two adjacent mounted trail-cameras which are currently operational. The trail cameras implement small fraction size (1/4 inch 1/3 inch) CCD sensors, which are typically found in surveillance or computer-based cameras. They utilise a 5Mp CCD with options to either reduce image with compression to 3Mp or increase with interpolation to 8Mp. The trail cameras are mounted in the same position as the previously-used cameras and collect image frames identical to those historically collected with previous camera systems, facilitating direct comparison.
description: Automatic camera system with 35mm film 2 trail cameras with small fraction size (1/4 inch 1/3 inch) CCD sensors - utilising 5Mp CCD with options to reduce image with compression to 3Mp or increase with interpolation to 8Mp
description: This dataset is [Version 2] of the previous dataset that has observations up until 2008, and includes data up to 2019. As this dataset is a long-term monitoring project, methods differed throughout the 20th and 21st century. The different methods are described in the lineage section of this publication. Data was not collected for the years 2009 and 2015 due to camera failure.