Abstract
Abstract. In contrast to physical processes, biogeochemical processes are inherently patchy in the ocean, which affects both the observational sampling strategy and the representativeness of sparse measurements in data assimilating models. In situ observations from multiple glider deployments are analysed to characterize spatial scales of variability in both physical and biogeochemical properties, using an empirical statistical model. We find that decorrelation ranges are strongly dependent on the balance between local dynamics and mesoscale forcing. The shortest horizontal (5–10 km) and vertical (45 m) decorrelation ranges are for chlorophyll a fluorescence, whereas those variables that are a function of regional ocean and atmosphere dynamics (temperature and dissolved oxygen) result in anisotropic patterns with longer ranges along (28–37 km) than across the shelf (8–19 km). Variables affected by coastal processes (salinity and coloured dissolved organic matter) have an isotropic range similar to the baroclinic Rossby radius (10–15 km).
Highlights
At the interface between oceanic and coastal processes, continental shelf regions are characterized by complex dynamics resulting from the interaction between different water masses at smaller spatial scales than the open ocean (Yoder et al, 1987)
By way of both example and validation, we calculate the cross-shelf semivariogram obtained from daily satellite remote-sensed sea surface temperature (SST) anomalies (Fig. 2)
The sill σ 2 reflects the constant background variability of the variable. It is reached at a specific distance, here r = 24 km, which is referred to as the range or the dominant length scale
Summary
At the interface between oceanic and coastal processes, continental shelf regions are characterized by complex dynamics resulting from the interaction between different water masses at smaller spatial scales than the open ocean (Yoder et al, 1987). The dynamics on the shelf are influenced both by local coastal processes and the episodic intrusion of the large-scale East Australian Current (EAC) and its eddies (Fig. 1, Schaeffer et al, 2013, 2014a). The EAC is the western branch of the subtropical gyre in the South Pacific It is a warm and dynamic poleward flowing current, encroaching on the continental shelf of southeastern Australia between around 18◦ S (Ridgeway and Godfrey, 1994) and usually 30.7–32.4◦ S (Cetina-Heredia et al, 2014) where it bifurcates eastward, forming the Tasman Front. Eddies are shed (Everett et al, 2012), leading to high variability in the velocity field and water masses on the shelf (Schaeffer et al, 2014b; Schaeffer and Roughan, 2015)
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