Temporal and Spatial Variations of Cross‐Shelf Nutrient Exchange in the East China Sea, as Estimated by Satellite Altimetry and In Situ Measurements

Abstract

Based on velocity and nutrient data from satellite and in situ measurements, we studied the temporal and spatial variations for 22‐year (1993–2014) cross‐shelf nutrient exchange at the 200‐m isobath section in the East China Sea. Since nitrate and phosphate concentrations were highly correlated (correlation coefficient of 0.95), only nitrate transport was investigated in detail. The cross‐shelf nutrient exchange is explored from whole to detail. The results show that the 22‐year averaged section‐integrated nitrate transport (FQ) is 22.0 ± 12.4 kmol/s (+ in the on‐shelf direction). Its interannual variation is larger than its seasonal variation, but no persistent interannual signal exists. The on‐ and off‐shelf components of FQ are about twice as large as FQ itself, and the temporal variation of FQ is mainly determined by its on‐shelf component. The depth‐integrated nitrate transport (Fq) along the 200‐m isobath shows that the largest on‐ and off‐shelf nitrate transports occur northeast of Taiwan, whereas the on‐shelf nitrate transport at the middle East China Sea is also important. Moreover, the on‐shelf component of Fq northeast of Taiwan mainly determines the temporal variation in FQ. The mean and standard deviation of the sectional nitrate flux (F) suggest that the largest variation in F occurs northeast of Taiwan, 150 m below the surface. Combining results from empirical orthogonal function analysis, the horizontal and vertical structures of F are determined by velocity and nitrate concentration, respectively, whereas the temporal variation of F is mainly determined by velocity and the geostrophic component.

Dissolved inorganic nitrogen and particulate organic nitrogen budget in the Yucatán shelf: driving mechanisms through a physical–biogeochemical coupled model

“…A4). The model does not include an explicit compartment for nitrogen in the form of DON, although it can be included as in the work of Druon et al (2010), which adds semi-labile DOC and DON as state variables to the original Fennel et al (2006) model. They comment on the difficulties of validating the model with observations and highlight open questions even in the definition of both DOC and DON pools (see also Anderson et al, 2015).…”

Distribution and off–shelf transport of dissolved manganese in the East China Sea

“…The cross-shelf transport pattern in the ECS has also been wellvalidated by observational studies and numerical models (Ding et al, 2019;Zhang et al, 2019;Wang et al, 2021).…”

“…On-shelf and off-shelf transport are crucial for marine processes, which have generated interest involving the geochemical budgets of biogenic elements (Ren et al, 2015;Ding et al, 2019;Zhang et al, 2021b). In this study, we examined the distribution and seasonal variations of dissolved Mn across the ECS from the eutrophic coastal waters to the oligotrophic KW.…”

Marine Dimethyl Sulfide Fluxes in the Yellow and East China Seas: Scenario Variation During the 1980s–2090s and Its Drivers

“…From 1987 to 2009, the nitrate flux was amplified by ∼12% in the PN section seen in Figure 1, meaning an upward trend of the transport of the Kuroshio waters (Guo et al, 2012). Ding et al (2019) calculated cross-shelf nutrient exchange, and suggested that the nitrate concentration (nitrate flux) at the 200-m isobath section in the ECS rose by up to 15% (25%) from 1993 to 2015. In the future, onshore intrusion is projected to increase (Hao et al, 2022;Seo et al, 2014), resulting in more nutrients being transported to the middle shelf of the ECS.…”