Abstract
The seasonal mixed layer pump (MLP) is an important pathway transporting organic carbon from the upper ocean to the ocean interior. While the MLP's export role has been well-studied in high latitudes, its contribution in low latitudes remains uncertain. Here, we quantify the seasonal MLP-driven carbon export (E(MLP)) in low-latitude oceans using data from 26 biogeochemical profiling floats. Our analysis reveals that E(MLP) ranges from -0.9 to 7.6 g C m(-2) yr(-1), contributing up to 53% of carbon export in certain areas. We find the relative positions of the mixed layer depth, euphotic depth, and nitracline depth regulate E(MLP) strength in low-latitude oceans. Global extrapolation of these observations across low-latitude oceans yields a total E(MLP) of 0.07 ± 0.02 Pg C yr(-1), 75% higher than previous estimates, underscoring the previously underestimated role of the seasonal MLP in low-latitude oceans. These results reveal the controlling mechanisms of low-latitude seasonal MLP and highlight its disproportionately important role in regional ecosystems, particularly in oligotrophic oceans where carbon export pathways are limited.