Humpback Whale Records Reveal Insights on Historic Sea Ice Extent

Recent research indicates that historical data from humpback whale catches in the Southern Ocean may significantly enhance the accuracy of sea ice extent estimates used in contemporary climate models. The findings, published in the journal *Environmental Research: Climate* in July 2025, suggest that previous models have overestimated the historic reach of sea ice, which is crucial for understanding climate dynamics.

According to Dr. Marcello Vichi, an oceanographer at the University of Cape Town and the lead author of the study, the data collected from whaling expeditions provides a valuable proxy for understanding sea ice extent during the early 20th century. "We decimated them; now, they’re helping us to do a better job for our future projections," Vichi noted, highlighting the paradoxical role of whaling records in modern climate science.

The study utilized catch data from over 215,000 humpback whales harvested between 1900 and 1950, focusing particularly on the 1930s when whalers recorded high catch counts during the Antarctic summer months. This data set, with a remarkable accuracy rate of over 97%, allowed researchers to compare historical whaling locations with current climate models, revealing that these models consistently overestimate sea ice extent by an average of 4° latitude, with some discrepancies reaching as high as 10°.

Dr. Marilyn Raphael, a physical geographer at the University of California, Los Angeles, who was not involved in the study, emphasized the importance of accurately estimating sea ice extent. "If you can’t get it right when you know what happened, then you’ve got to worry about if you’ll get it right when you don’t know what will happen," Raphael stated. This sentiment underscores the broader implications of the findings for climate modeling, which relies heavily on historical data to predict future conditions.

The research indicates that as climate models currently stand, they may misrepresent the historical energy balance of the Earth, which could lead to flawed predictions regarding future sea ice behavior in the Southern Ocean. As Vichi explained, understanding the extent of sea ice is critical because it reflects sunlight, influencing temperature gradients and, consequently, wind patterns and overall climate.

Climatologist Dr. Ryan Fogt from Ohio University, who was not part of the study, highlighted the potential shifts in sea ice behavior since the 1960s, which may have altered how ice forms and behaves in the Southern Ocean. He noted, "We’re working with fewer than 50 years of satellite observations, so if there are large cycles that happen, we don’t know if that 50-year period is representative of the whole."

The utilization of historical records, such as whaling data, is seen as a crucial method for filling gaps in the understanding of climate systems, despite their inherent limitations. Raphael asserted, "It’s important to use all the information we have to see how it matches," reinforcing the value of these historical datasets in contemporary research.

As climate scientists continue to grapple with the complexities of the climate crisis, findings like those from Vichi and his colleagues provide essential insights that may help refine predictive models and contribute to more effective climate strategies moving forward. The study underscores the importance of revisiting historical data to enhance our understanding of current and future environmental conditions, particularly in sensitive regions like the Southern Ocean, where changes in sea ice can have far-reaching implications for global climate patterns.