An operational overview of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) Northeast Pacific field deployment

Abstract

The goal of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) field campaign is to develop a predictive understanding of the export, fate, and carbon cycle impacts of global ocean net primary production. To accomplish this goal, observations of export flux pathways, plankton community composition, food web processes, and optical, physical, and biogeochemical (BGC) properties are needed over a range of ecosystem states. Here we introduce the first EXPORTS field deployment to Ocean Station Papa in the Northeast Pacific Ocean during summer of 2018, providing context for other papers in this special collection. The experiment was conducted with two ships: a Process Ship, focused on ecological rates, BGC fluxes, temporal changes in food web, and BGC and optical properties, that followed an instrumented Lagrangian float; and a Survey Ship that sampled BGC and optical properties in spatial patterns around the Process Ship. An array of autonomous underwater assets provided measurements over a range of spatial and temporal scales, and partnering programs and remote sensing observations provided additional observational context. The oceanographic setting was typical of late-summer conditions at Ocean Station Papa: a shallow mixed layer, strong vertical and weak horizontal gradients in hydrographic properties, sluggish sub-inertial currents, elevated macronutrient concentrations and low phytoplankton abundances. Although nutrient concentrations were consistent with previous observations, mixed layer chlorophyll was lower than typically observed, resulting in a deeper euphotic zone. Analyses of surface layer temperature and salinity found three distinct surface water types, allowing for diagnosis of whether observed changes were spatial or temporal. The 2018 EXPORTS field deployment is among the most comprehensive biological pump studies ever conducted. A second deployment to the North Atlantic Ocean occurred in spring 2021, which will be followed by focused work on data synthesis and modeling using the entire EXPORTS data set.

Cloud shadows drive vertical migrations of deep-dwelling marine life

“…Data were collected from the R/V Revelle during the 2018 EXPORTS field campaign (34) between August 12 and September 10 near Ocean Station Papa (145°W, 50°N) (gray lines, SI Appendix, Fig. S1).…”

Concentrations, ratios, and sinking fluxes of major bioelements at Ocean Station Papa

“…Uncertainties were calculated by propagating the uncertainties from the steady-state and non-steadystate flux estimates as detailed in Buesseler et al (2020a) for POC flux. a wider range of conditions compared to the sampling conducted on the R/V Roger Revelle (Siegel et al, 2021). Moreover, lower pump POC and PN concentrations in the larger size fractions may reflect particle loss from the Nitex screens during pumping by means of disaggregation or breakage of fragile particles, and/or inefficient rinsing of the Nitex screens.…”

“…A total of 12 in situ pump casts were conducted over three time periods, spaced 8 days apart, termed "epochs" (Epoch 1 ¼ dark blue, Epoch 2 ¼ red, and Epoch 3 ¼ turquoise). Each symbol represents a specific cast with labels next to the symbols indicating station details: station number and whether it was occupied during a small scale (SS) or large scale (LS) survey (Siegel et al, 2021). DOI: https:// doi.org/10.1525/elementa.2020.00166.f1…”

“…EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) aims to develop a predictive understanding of the export and fate of global net primary production and associated bioelements and their implications for climate (Siegel et al, 2016;Siegel et al, 2021). This goal requires the use of multiple, complementary approaches to quantify the export of particles from the euphotic zone and subsequent attenuation in the twilight zone across a range of ecosystem states.…”

“…The first EXPORTS field campaign took place in the northeast Pacific near Ocean Station Papa (Station P; 50 N, 145 W) in August-September 2018. Details on the sampling strategy are found in Siegel et al (2021). Briefly, two types of ship-based sampling were employed: process-oriented (R/V Roger Revelle, RR1813) and survey-oriented (R/V Sally Ride, SR1812).…”