Increasing Warming May Inhibit Land Carbon Uptake in Northern High Latitudes

Abstract Arctic ecosystems are warming at an accelerated rate, with heatwaves becoming more frequent and intense. We examined productivity responses of Arctic ecosystems to major warming events from 2000 to 2022. Results indicated that early‐season warming generally enhances productivity, whereas prolonged high temperatures suppress productivity later in the growing season. Responses varied by region and event timing. For instance, the 2004 Northwestern North American hot year increased productivity through summer, while the 2010 Arctic warming boosted early‐season productivity that declined as heat persisted. Similar early gains followed by moisture‐driven declines during the 2015 Northwestern North American and 2020 Eastern Siberian events. Overall, early warmth stimulates growth, but sustained heat and low moisture constrain productivity, particularly in taiga and tundra ecosystems. These patterns highlight the vulnerability of Arctic carbon sinks to warming and underscore the need for improved observations and modeling to assess ecosystem resilience under increasing climate extremes.