Historical catch records of humpback whales and the assessment of early 20th century sea ice edge in climate models

Abstract Assessment of historical environmental conditions in the Southern Ocean is limited by sparse oceanographic records prior to remote-sensing data. Whale catch data, particularly from humpback whales, can help fill this gap, as these whales inhabit waters near the sea ice edge. This study combines historical whale catch data with sea-ice model simulations from CMIP6 to assess the performance in the decade 1930–1939. The models were ranked based on their ability to simulate satellite-observed sea ice seasonality. The high-ranking models locate the sea-ice edge north of historical humpback whale catch regions, indicating higher sea-ice extent at the start of the 20th century, especially in November and December. It is recommended that models be tuned towards these early 20th century conditions while running the pre-industrial simulations. This interdisciplinary approach suggests that using only satellite-era data for model calibration may lead to overestimates of historical sea-ice extent, affecting future predictions.