Tools and Data
Data Source 1
The Sea Ice Index provides easy-to-access and use browse imagery and text formatted data, providing information on monthly sea ice conditions since 1978. The text data can be imported into spreadsheet software to investigate anomalies and trend. Raw data can be used to analyze daily conditions and daily/monthly regional trends and anomalies. The browse and summary data provide imagery of monthly sea ice conditions and anomalies, as well as text files with monthly total extent and area values. The raw data are 2-dimensional gridded fields with daily and monthly sea ice concentration at 25-km spatial resolution. Data are accessible via ftp through a web browser or ftp server. Data summaries can be imported into spreadsheets. Raw data can be input into image processing software (e.g., ImageJ, ENVI, etc.).
For more information on this data set see Exploring Sea Ice Data from Satellites
A detailed explanation of the remote sensing method used to gather this data can be found at the National Snow and Ice data center website.
Data Source 2
NCEP is the National Centers for Environmental Predictions. The datasets they offer are developed from weather station data, satellite data (for the period that satellites have been gathering data), and computer models. The recent data is an operational product, reporting results in near-real-time.
For historical data, NCEP completes a re-analysis of the data every few years. For this, they examine existing data and add in any new data that weren't available operationally. They also make quality control checks to delete erroneous data and make adjustments for differences in data quality to de-emphasize any biases.