Size‐Fractionated Compositions of Marine Suspended Particles in the Western Arctic Ocean: Lateral and Vertical Sources

Abstract

We present full water depth sections of size‐fractionated (1–51 μm; >51 μm) concentrations of suspended particulate matter and major particle phase composition (particulate organic matter [POM], including its carbon isotopic composition [POC‐δ13C] and C:N ratio, calcium carbonate [CaCO3], opal, lithogenic particles, and iron and manganese [oxyhydr]oxides) from the U.S. GEOTRACES Arctic Cruise (GN01) in the western Arctic in 2015. Whereas biogenic particles (POM and opal) dominate the upper 1,000 m, lithogenic particles are the most abundant particle type at depth. Minor phases such as manganese (Mn) oxides are higher in GN01 than in any other U.S. GEOTRACES cruises so far. Extremely depleted POC‐δ13C, as low as ~ −32‰, is ubiquitous at the surface of the western Arctic Ocean as a result of different growth rates of phytoplankton. Moderate penetration of depleted POC‐δ13C to depth indicates active sinking of large particles in the central basin. Lateral transport from the Chukchi shelf is also of significance in the western Arctic, as is evident from increases in biogenic silica to POC ratios and Mn oxide concentrations in the halocline, as well as lithogenic element contents in the deep waters. Our study supports previous suggestions of the near absence of CaCO3 in the Arctic Basin. This study presents the first data set of concentration and composition of suspended particles in the western Arctic Ocean and sheds new light on the vertical and lateral processes that govern particle distribution in this enclosed ocean basin.

Open-Ocean Minima in δ13C Values of Particulate Organic Carbon in the Lower Euphotic Zone

“…We excluded some published studies from our numerical analysis due to a scarcity of depths sampled in the upper water column or due to likelihood of terrigenous inputs, low-oxygen metabolisms, or experimental manipulations (Williams and Gordon, 1970;Eadie and Jeffrey, 1973;Druffel et al, 1996;Benner et al, 1997;Trull and Armand, 2001;Hernes and Benner, 2006;Close et al, 2014;Krishna et al, 2018;Liu et al, 2018). We also did not include data from the Arctic region due to the prevalence of terrigenous or advected POC in these areas (e.g., Griffith et al, 2012;Xiang and Lam, 2020).…”

“…The local minimum in δ 13 C POC values observed in the lower euphotic zone did not correlate with the proportional contribution of lignin to total POC at that depth. Advection of POC from adjacent waters often cannot explain the range of δ 13 C POC values observed in a single water column (e.g., Lourey et al, 2004), although this is more commonly cited in the Arctic (Griffith et al, 2012;Xiang and Lam, 2020).…”

Turbulent Mixing and the Formation of an Intermediate Nepheloid Layer Above the Siberian Continental Shelf Break

“…Anticipated changes in the near coastal areas, like increased anthropogenic use or thawing permafrost​ — therefore have the potential to impact the entire Arctic Ocean. Resolving the transport mechanisms connecting the Arctic shelf and interior basin is hence a key issue to understand organic carbon cycling and particle transport pathways (Forest et al., 2015), especially in the light of a rapidly changing Arctic system, which will likely impact particle sources and transport (Xiang & Lam, 2020).…”

“…Fahl and Nöthig (2007) found high vertical fluxes of mostly lithogenic material at intermediate depths above the southern Lomonosov Ridge, presumably caused by lateral advection from the Laptev Sea continental margin. Xiang and Lam (2020) report intermediate lithogenic particle maxima in the Arctic basins, with elevated concentrations on the Eurasian side of the Lomonosov Ridge, and suspect dense‐water cascading in winter as the major lateral transport process. Evidence of a turbid INL was observed over the Laptev Sea inner shelf (water depths < 60 m), probably caused by a displacement of the bottom nepheloid layer in the vicinity of a shallow bank (Wegner et al., 2003).…”

Multiscale Superposition and Decomposition of Field‐Measured Suspended Sediment Concentrations: Implications for Extending 1DV Models to Coastal Oceans With Advected Fine Sediments

“…However, synchronous observations from at least three sites with limited distances are necessary to apply the “box model,” which is technologically complex and introduces other assumptions, such as a uniform C ( t ) distribution along the box boundaries. Recently, unique chemical compositions of the suspended particles have been used as chemical fingerprints for tracing horizontal vs. vertical transport in the water column (i.e., particle composition tracing) (Xiang & Lam, 2020); however, this method depends on field water sampling and laboratory geochemical analysis and therefore cannot be used for continuous quantification.…”