Tracing the transport of colored dissolved organic matter in water masses of the Southern Beaufort Sea: relationship with hydrographic characteristics

Abstract

Abstract. Light absorption by colored dissolved organic matter (CDOM) [a CDOM (λ)] plays an important role in the heat budget of the Arctic Ocean, contributing to the recent decline in sea ice, as well as in biogeochemical processes. We investigated a CDOM (λ) in the Southern Beaufort Sea where a significant amount of CDOM is delivered by the Mackenzie River. In the surface layer, a CDOM (440) showed a strong and negative correlation with salinity, indicating strong river influence and conservative transport in the river plume. Below the mixed layer, a weak but positive correlation between a CDOM (440) and salinity was observed above the upper halocline, resulting from the effect of removal of CDOM due to brine rejection and lateral intrusion of Pacific summer waters into these layers. In contrast, the relationship was negative in the upper and the lower haloclines, suggesting these waters originated from Arctic coastal waters. DOC concentrations in the surface layer were strongly correlated with a CDOM (440) (r 2 = 0.97), suggesting that this value can be estimated in this area, using a CDOM (440) that is retrieved using satellite ocean color data. Implications for estimation of DOC concentrations in surface waters using ocean color remote sensing are discussed.

Carbon sources in suspended particles and surface sediments from the Beaufort Sea revealed by molecular lipid biomarkers and compound-specific isotope analysis

“…The water masses comprise the polar mixed layer (PML, salinity < 31, 0-50 m depth), which is influenced by fresh waters from the rivers and melting sea ice, the upper Pacific halocline (salinity: 31-33, 50-200 m depth) associated with a prominent nutrient maximum at salinities of ∼ 33, the lower Atlantic halocline (200-275 m depth) and the relatively warm (> 0 • C) and salty deep waters of Atlantic origin (salinity > 34.5, > 275 m depth). The main hydrodynamic and trophic features for the different zones are described in more detail by Codispoti et al (2005) and by Matsuoka et al (2012). A particularly important feature of the Arctic Ocean is the strong perennial cold halocline, which isolates surface waters (and sea ice) from warm and salty Atlantic waters.…”

Patterns of suspended particulate matter across the continental margin in the Canadian Beaufort Sea

“…The salinity range between 30.7 and 32.3 PSU corresponds to the Pacific Summer Water mass, which as the name suggests originates from waters flowing through Bering Strait during summer (? Matsuoka et al, 2012). Underneath, the Pacific Winter Water is characterized by salinity between 32.3 and 33.9 PSU and typically found 5 from ∼180 to 220 m depth.…”

“…2b) and high colored dissolved organic matter (CDOM) fluorescence ( Fig. 3; Matsuoka et al, 2012). The highest ship-based observation of surface-water c p (660) of ∼2.6 m −1 was observed at station 394 in 13-m deep waters at the mouth of Kugmallit Bay; however, reached 8.8 m −1 at 10 m depth and presumably higher values near the seabed.…”

“…This V ref was only marginally higher than maximum values observed during the MALINA expedition. The above method also assumes a negligible contribution by CDOM to c p at 660 nm (Bricaud et al,20 1981), which is a reasonable assumption based on data shown in Matsuoka et al (2012).…”

“…The underlying Pacific Winter Water is characterized by maxima in both nutrients and CDOM ( Fig. 3; Matsuoka et al, 2012). The nutrient maximum is typically found at the center of the Pacific Winter Water near the 33.1 PSU isohaline (Martin et al, 2010).…”