Derivation and optimization of a new Antarctic sea-ice record

The recently developed Bristol passive-microwave-satellite algorithm for de riving sea-ice concentration has possible theoretical and practical advanta ges over the widely used NASA/Team and Comiso algorithms. It was applied fo r the first time here to derive a long-term sea-ice series. The Bristol alg orithm was reparameterized by manually tuning its brightness temperature ti e-points both seasonally and interannually to systematically account for ch anging environmental conditions, satellite radiometer drift and differences in calibration and observing time between the three Special Sensor Microwa ve/Imager (SSM/I) sensors. In addition, an automatic algorithm was develope d to remove residual noise in SSM/I images. The reparameterized Bristol alg orithm performed well against the others tested in an Advanced Very High Re solution Radiometer ( AVHRR) thermal infrared case-study validation. The SS M/I sea-ice extent was compared with Geosat radar altimetry and showed good agreement in winter; reasons are proposed to explain the summer difference . The optimized Antarctic sea-ice record spans the whole of the available S SM/I period (July 1987 to December 1997) and reveals a 3 +/- 0.3% (3 +/- 1. 5%) increase in extent (area); it has been used to study Antarctic sea-ice/ atmosphere/ocean interactions and climatic couplings.