evidence: Antarctic sea ice has likely reached its maximum extent for the year, at 17.16 million square kilometers (6.63 million square miles) on September 19, according to scientists at the National Snow and Ice Data Center (NSIDC) at the University of Colorado Boulder (CU Boulder). The 2024 maximum is the second lowest in the 46-year satellite record. The record low maximum occurred in 2023. "The dramatic downward step in southern winter sea ice spanning the past two years points more than ever to effects from a record-warm ocean on Antarctic climate," said senior research scientist Ted Scambos of the Cooperative Institute for Research in Environmental Sciences (CIRES) at CU Boulder. NSIDC scientists stress that the Antarctic sea ice extent number is preliminary—weather conditions could still push the ice extent higher. NSIDC will issue a full analysis in October addressing the possible causes behind this year’s ice conditions, interesting aspects of the growth season, the setup going into the austral summer melt season, and graphics comparing this year to the long-term record. There is also some uncertainty in the estimate and date because of an outage in the input source data from September 12 to 18. However, that does not affect the ranking or the long-term trends.