Abstract
The distribution and vertical fluxes of particulate organic carbon and other key elements in the Arctic Ocean are primarily governed by the spatial and seasonal changes in primary productivity, areal extent of ice cover, and lateral exchange between the shelves and interior basins. The Arctic Ocean has undergone rapid increase in primary productivity and drastic decrease in the areal extent of seasonal sea ice in the last two decades. These changes can greatly influence the biological pump as well as associated carbon export and key element fluxes. Here, we report the export of particulate organic and inorganic carbon, particulate nitrogen and biogenic silica using 210Po and 210Pb as tracers for the seasonal vertical fluxes. Samples were collected as a part of US GEOTRACES Arctic transect from western Arctic Basin in 2015. The total activities of 210Po and 210Pb in the upper 300 m water column ranged from 0.46 to 16.6 dpm 100L–1 and 1.17 to 32.5 dpm 100L–1, respectively. The 210Pb and 210Po fluxes varied between 5.04–6.20 dpm m–2 d–1 and 8.26–21.02 dpm m–2 d–1, respectively. The corresponding particulate organic carbon (POC) and particulate nitrogen (PN) fluxes ranged between 0.75–7.43 mg C m–2 d–1 and 0.08–0.78 mg N m–2 d–1, respectively, with highest fluxes observed in the northern ice-covered stations. The particulate inorganic carbon (PIC) and biogenic silica (bSi) fluxes were extremely low ranging from 0 to 0.14 mg C m–2 d–1 and 0.14 to 2.88 mg Si m–2 d–1, respectively, at all stations suggesting absence of ballast elements in facilitating the biological pump. The variability in POC fluxes with depth suggest prominent influence of lateral transport to downward fluxes across the region. The results provide a better understanding of the spatial variability in the vertical fluxes POC, PN, bSi, and PIC in the western Arctic which is currently undergoing dramatic changes.
Highlights
The Arctic Ocean covers an area of 9.6 × 106 km2 (Serreze et al, 2006), which corresponds to 5% of the world oceans by surface area, with 1.5% by volume (Meybeck and Ragu, 1997; Guay and Falkner, 1998) indicating that it is a relatively shallow ocean with about 50% of the total Arctic Ocean surface area as continental shelf area (Jakobsson et al, 2004)
The elevated 226Ra activities observed between 100 and 200 m at station 56 is likely related to the shelf-modified Pacific inflow of water, whereas the elevated 226Ra activities observed between 100–200 m and 75–125 m at station 43 and station 48, respectively, are probably associated with Chukchi winter water (CWW), remnant winter water (RWW), and meteoric cold water (MCW) associated with ice melt that has been carried by the Transpolar Drift (TPD) (Kipp et al, 2018)
We estimated the export flux of particulate organic carbon (POC), particulate nitrogen (PN), particulate inorganic carbon (PIC), and biogenic silica (bSi) based on the 210Po and 210Pb fluxes obtained during the 2015 US Arctic GEOTRACES cruise in the western Arctic Ocean
Summary
The Arctic Ocean covers an area of 9.6 × 106 km (Serreze et al, 2006), which corresponds to 5% of the world oceans by surface area, with 1.5% by volume (Meybeck and Ragu, 1997; Guay and Falkner, 1998) indicating that it is a relatively shallow ocean with about 50% of the total Arctic Ocean surface area as continental shelf area (Jakobsson et al, 2004). The input of freshwater from Arctic rivers into the Arctic Ocean has increased significantly during recent decades (Peterson et al, 2002; Ahmed et al, 2020). This increase in freshwater discharge, coupled with increased coastal erosion, permafrost thaw and sea ice melting suggest that the riverine input of carbon, nutrients, and metals will continue to increase in the future. The highly productive shallow shelf serves as a source of organic carbon and nutrients to the central Arctic Ocean through the two major currents systems, Transpolar Drift (TPD), and Beaufort Gyre (e.g., Wheeler et al, 1997; Krishnamurthy et al, 2001; Klunder et al, 2012; Charette et al, 2020). Changes in freshwater input and extent of sea-ice melting can greatly influence the biological pump and particle scavenging in this region
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
