DOI: 10.5281/zenodo.5593382
title: High-resolution, mixed layer NCP estimates and ancillary data from the Central and Eastern North American Arctic: 2015, 2018, 2019

description: This dataset contains compiled ship-based, high-resolution (underway) estimates of mixed layer net community production (NCP) from three summertime cruises in the Central and Eastern North American Arctic in 2015, 2018 and 2019. NCP estimates were derived from underway O2/Ar observations, obtained using ship-based membrane inlet mass spectrometry. Ancillary data - including geographic information for the underway measurements (time, location) - are also provided. Data are provided in NetCDF and Matlab (.mat) format. This dataset is a supplement to the following publication: Izett, R. W., Castro de la Guardia, L., Chanona, M., Myers, P. G., Waterman, S., and Tortell, P. D. Impact of vertical mixing on summertime net community production in Canadian Arctic and Subarctic waters: Insights from in situ measurements and numerical simulations. Publication abstract: We present ΔO<sub>2</sub>/Ar-based estimates of mixed layer net community production (NCP) from three summer cruises in the central and eastern North American Arctic and Subarctic oceans. Coupling shipboard underway and discrete observations with output from an ocean circulation model, we correct the NCP estimates for vertical mixing contributions to the surface O<sub>2</sub> budget. Large positive corrections were derived in regions of strong wind-driven mixing, such as the Labrador Sea, and the physically-dynamic Canadian Arctic Archipelago. In contrast, corrections were small in the density-stratified Baffin Bay, where vertical mixing was low, and in the well-mixed Hudson Strait, where vertical O<sub>2</sub> gradients were weak. We observed a heterogeneous distribution of corrected NCP across the study region, reflecting varying contributions of nutrient supply, freshwater input and sea ice dynamics. Elevated NCP was apparent in the Labrador Sea, Hudson Strait, and nearshore regions influenced by glacial meltwater and recent ice retreat. Low NCP and localized net heterotrophy were observed in Baffin Bay, and near strong freshwater and organic matter sources in Hudson Bay and the Queen Maud Gulf. A multiple linear regression model developed using readily-available oceanographic data explained ~73 % of the apparent NCP variability in our dataset. Our work demonstrates the influence of vertical mixing on ΔO<sub>2</sub>/Ar-based NCP calculations and presents a novel approach to account for this process. This work ultimately provides new constraints on biological productivity in under-sampled high-latitude ocean regions, and insights into potential future ecosystem responses to rapidly changing environmental conditions in Arctic and Subarctic waters. Publication summary: Marine net community production (NCP) is an important variable representing the ocean’s ability to support the marine ecosystem and remove carbon dioxide from the atmosphere. A common approach to estimating NCP involves evaluations of upper ocean oxygen (O<sub>2</sub>) concentrations. In using this approach, however, many studies typically neglect the impact of vertical mixing on O<sub>2</sub> budgets, and therefore produce inaccurate NCP estimates. In this paper, we describe a new method combining ship-based measurements and the output from a numerical ocean circulation model to refine NCP estimates for vertical mixing impacts in North American Arctic and Subarctic oceans. The resulting dataset revealed high NCP in the Labrador Sea (Inuktitut: <em>Lâbradorip Imappinga</em>), North Atlantic Ocean, Hudson Strait (<em>Ikirasarjuaq</em>) and the northern Canadian Arctic Archipelago (CAA), and low values in Baffin Bay (<em>Saknirutiak Imanga</em>) and the southern CAA. Our results also suggested that riverine freshwater input to Hudson Bay (<em>Tasiujarjuar</em>) and the Queen Maud Gulf (<em>Ugjulik</em>) can reduce local NCP, while glacial meltwater may stimulate NCP elsewhere. Overall, this work provides a new NCP dataset in an under-sampled region, and offers insights into potential future ecological responses to rapidly changing environmental conditions in Arctic and Subarctic waters.