Rapid reduction of Arctic perennial sea ice

The extent of Arctic perennial sea ice, the year‐round ice cover, was significantly reduced between March 2005 and March 2007 by 1.08 × 10 6 km 2 , a 23% loss from 4.69 × 10 6 km 2 to 3.61 × 10 6 km 2 , as observed by the QuikSCAT/SeaWinds satellite scatterometer (QSCAT). Moreover, the buoy‐based Drift‐Age Model (DM) provided long‐term trends in Arctic sea‐ice age since the 1950s. Perennial‐ice extent loss in March within the DM domain was noticeable after the 1960s, and the loss became more rapid in the 2000s when QSCAT observations were available to verify the model results. QSCAT data also revealed mechanisms contributing to the perennial‐ice extent loss: ice compression toward the western Arctic, ice loading into the Transpolar Drift (TD) together with an acceleration of the TD carrying excessive ice out of Fram Strait, and ice export to Baffin Bay. Dynamic and thermodynamic effects appear to be combining to expedite the loss of perennial sea ice.