Future climate-driven fires may boost ocean productivity in the iron-limited North Atlantic.

Rapid shifts in fire regimes affect the carbon cycle by releasing carbon and nutrients such as iron (Fe), potentially enhancing marine productivity and carbon export. Here we use fire emission projections and Earth system models to examine how climate-driven changes in fire emissions may alter soluble Fe (SFe) deposition and productivity. By century's end, climate change could increase Fe emissions from fires by 1.7-1.8 times beyond projections considering only direct human influences. Model projections show rising SFe deposition in Northern Hemisphere high latitudes under increasing socio-economic activity, potentially boosting the impact of SFe deposition on productivity in the Fe-limited North Atlantic by up to 20% annually (40% in summer), assuming stable macronutrient levels. However, declining macronutrient availability may shrink Fe-limited areas, where climate-driven fires could offset productivity losses by 7-8%. In the Southern Ocean, fossil fuel emissions primarily control SFe deposition, as reductions in anthropogenic fires counterbalance climate-driven increases.