Last week, a reader of Arctic Sea Ice News & Analysis asked what we know about Arctic sea ice extent before the satellite records began in 1979. Those records show that Arctic sea ice has been declining at an increasing pace since 1979—enough data to see a strong signal of climate change. But scientists also want to know what sea ice was like before satellites were there to observe it. Mark Serreze, NSIDC director and research scientist, said, “The better we understand how the climate system behaved in the past, the better we can understand and place into context what is happening today.” What do we know about sea ice conditions before 1979, and how do we know that?
Historical data on sea ice
Scientists have pieced together historical ice conditions to determine that Arctic sea ice could have been much lower in summer as recently as 5,500 years ago. Before then, scientists think it possible that Arctic sea ice cover melted completely during summers about 125,000 years ago, during a warm period between ice ages. Continue reading