Summertime Evolution of Net Community Production and CO₂ Flux in the Western Arctic Ocean

Abstract

The Arctic Ocean is currently experiencing rapid environmental and ecological changes in response to climate change. In recent decades, sea ice extent has drastically declined, resulting in earlier seasonal ice retreat and thinning (Onarheim et al., 2018; Stroeve et al., 2018). This change has profound and potentially cascading effects, as sea-ice state is a crucial factor to regulate light availability, water column stability and nutrient availability (Taylor et al., 2013). In addition, sea ice provides habitat for numerous autotrophs in polar regions (Fernández-Méndez et al., 2018; Selz et al., 2018). Thus, these important factors intimately associated with ice can greatly affect the timing, location, and intensity of Arctic Ocean primary production. Still, the role of sea ice distribution and melt history on the seasonal evolution of net community production (NCP) in the Arctic Ocean is under-documented, and the alteration of biological production by climate warming and sea-ice retreat is poorly understood. NCP is quantified from the difference between the oxygen produced by plankton during photosynthesis and the oxygen consumed by the entire marine community during respiration. The rapidly changing sea ice brings great variability and uncertainty regarding timing and magnitudes of NCP. In addition, a better understanding of how changing NCP might affect sea surface carbon dioxide (CO 2) distributions and sea-air CO 2 fluxes is crucially required for reliably modeling current and future Arctic Ocean carbon budgets. Several studies have assessed regional variations of Arctic Ocean sea-air CO 2 fluxes (

The Changing CO2Sink in the Western Arctic Ocean From 1994 to 2019

“…Furthermore, summer stratification strengthens its oligotrophic characteristics (Ardyna & Arrigo, 2020; Ji et al., 2019). Interestingly, a recent study further found that NCP in the Canada Basin is closely associated with ice melting stages (Ouyang et al., 2021). Therefore, instead of using monthly averaged NCP, we incorporated NCP estimation based on the relationship between ice concentration and NCP into our model.…”

“…Briefly, NCP (5.6 ± 2.0 mmol C m −2 d −1 ) was relatively high during the actively melting period (ice% from 30% to 50%), whereas NCP (1–2 mmol C m −2 d −1 ) was lower in the pre‐melt (ice% >80%) and post‐melt period (ice% <15%) (Figure S2 in Supporting Information S1). This relationship was established by examining the histories of wind and ice in a given location combined with the underway measurement of Δ(O 2 /Ar) (Ouyang et al., 2021).…”

Interannual variability in methane and nitrous oxide concentrations and sea-air fluxes across the North American Arctic Ocean (2015–2019)

“…As described in Supporting Text S1, the majority of gas transfer velocities we derived from instantaneous or monthly-averaged wind speeds were systematically biased low compared to mixed layer residence time-weighted sea-air fluxes (Wanninkhof et al, 2002(Wanninkhof et al, , 2009. In addition, sea ice decreases the effective gas transfer velocity, and it is thus necessary to incorporate ice cover variability prior to sampling to accurately calculate the timeweighted sea-air flux (Ji et al, 2019;Ouyang et al, 2021).…”

Analysis of the Seasonal and Interannual Variations of Air‐Sea CO2 Flux in the Chukchi Sea Using a Coupled Ocean‐Sea Ice‐Biogeochemical Model

“…These blooms consume dissolved inorganic carbon (DIC) in the upper water layer, resulting in a lower pCO 2 level of the sea surface (<100-350 μatm) compared to that of the atmosphere (Bates, 2006). During the ice-free period, the mean air-sea CO 2 flux over the entire Chukchi Sea typically ranges from −10 mmol m −2 d −1 to −40 mmol m −2 d −1 (Bates, 2006;Evans et al, 2015;Gao et al, 2012;Murata & Takizawa, 2003;Ouyang et al, 2021;Pipko et al, 2002Pipko et al, , 2015Semiletov et al, 2007;Wang et al, 2003), with some low extremes of less than −70 mmol m −2 d −1 around the Hanna Shoal and Barrow Canyon vicinity (Bates, 2006;Mathis & Questel, 2013). Juranek et al (2019) concluded that biological production plays an important role in maintaining an oceanic carbon sink in the eastern Chukchi Sea during October 2011 and 2012.…”