Particle Interceptor Trap Deployments Demonstrate Enhanced Export Driven by Frontal Dynamics in the Chukchi Sea

Abstract

Under‐ice phytoplankton blooms in the Chukchi Sea are among the densest observed globally, and, together with sea ice microalgal and open water phytoplankton blooms, make the region one of the most productive in the Arctic Ocean. To better understand the factors influencing export of organic material captured by these blooms, free‐drifting and ice‐tethered particle interceptor trap arrays were deployed in the northeastern Chukchi Sea during the Tale of Three Systems cruise in June‐July 2023. Export fluxes of chlorophyll a (Chl a ), particulate organic carbon (POC), and particulate nitrogen (PN) were measured alongside taxonomic composition of collected material, hydrographic data, and sediment data. A dense under‐ice phytoplankton bloom was observed in the northern portion of the study area, and the ice edge was predominantly set by a persistent zonal water mass front throughout the sampling period. Outside the front, Chl a and POC fluxes were closely related to water column biomass, with the highest export fluxes observed beneath consolidated sea ice. In contrast, within the front, subduction driven by baroclinic instability dramatically enhanced export. South of the front, open water areas exhibited low biomass and rates of export, likely due to nutrient depletion by an earlier phytoplankton bloom. These findings demonstrate that the physical subduction of dense phytoplankton blooms can result in extremely high particle export fluxes on the shallow Chukchi Sea shelf.