An industrial-era decline in Greenland ice-core methanesulfonic acid is thought to herald a collapse in North Atlantic marine phytoplankton stocks related to a weakening of the Atlantic meridional overturning circulation. By contrast, stable levels of total marine biogenic sulfur contradict this interpretation and point to changes in atmospheric oxidation as a potential cause of the methanesulfonic acid decline. However, the impact of oxidation on methanesulfonic acid production has not been quantified, nor has this hypothesis been rigorously tested. Here we present a multi-century methanesulfonic acid record from the Denali, Alaska, ice core, which shows a methanesulfonic acid decline similar in magnitude but delayed by 93 years relative to the Greenland record. Box-model results using updated dimethyl sulfide oxidation pathways indicate that oxidation by pollution-driven nitrate radicals has suppressed atmospheric methanesulfonic acid production, explaining most, if not all, of Denali’s and Greenland’s methanesulfonic acid declines without requiring a change in phytoplankton production. The delayed timing of the North Pacific methanesulfonic acid decline, relative to the North Atlantic, reflects the distinct history of industrialization in upwind regions and is consistent with the Denali and Greenland ice-core nitrate records. These results demonstrate that multidecadal trends in industrial-era Arctic ice-core methanesulfonic acid reflect rising anthropogenic pollution rather than declining marine primary production.

工业时代格陵兰冰芯甲磺酸的下降被认为预示着北大西洋海洋浮游植物种群的崩溃，这与大西洋经向翻转环流的减弱有关。相比之下，海洋生物硫总量的稳定水平与这一解释相矛盾，并表明大气氧化的变化是甲磺酸下降的潜在原因。然而，氧化对甲磺酸生产的影响尚未量化，该假设也未经过严格检验。在这里，我们展示了来自阿拉斯加德纳利冰芯的多世纪甲磺酸记录，该记录显示甲磺酸的下降幅度与格陵兰岛记录相似，但延迟了 93 年。使用更新的二甲基硫醚氧化途径的盒模型结果表明，污染驱动的硝酸根氧化抑制了大气中甲磺酸的产生，这解释了大多数（如果不是全部）麦金利峰和格陵兰岛甲磺酸的下降，而无需改变浮游植物的产量。相对于北大西洋，北太平洋甲磺酸下降的时间延迟反映了逆风地区工业化的独特历史，并且与德纳利峰和格陵兰冰芯硝酸盐记录一致。这些结果表明，工业时代北极冰芯甲磺酸的数十年趋势反映了人为污染的增加，而不是海洋初级生产力的下降。