Lagrangian Residence Time in the Bay of Gdańsk, Baltic Sea

Abstract

The impact of synoptic scale and mesoscale variability on the Lagrangian residence time (LRT) of the surface water in the Bay of Gdańsk was investigated using the results from an eddy-resolving model. The computed LRT of 53-60 days was up to four times longer than the estimated flushing time reported by Witek et al. (2003). The highest residence times were those of Puck Bay and near the coast, shallower than 50 m water depth, especially during the winter. These sites also had the highest annual mean in LRT. During the summer, when the level of biological activity is high, the LRT distribution was very heterogeneous and patchy, possibly due to the dynamics of varying eddy field and to variable wind forcing. Long-term run tracking of the inflowing water from the Vistula River (VR) showed a broad spectrum of tracer distribution. The potential impact of a much higher LRT on the near-coastal nitrogen cycle, coastal filter function and genetic differentiation is discussed, and the consequences for coastal zone management are considered. Since residence time is the most important factor regulating nutrient cycling, the incorporation of residence time into the Marine Strategy Framework Directive descriptors would result in an improved, unbiased evaluation of good environmental status.

Origin and fate of dissolved organic matter in four shallow Baltic Sea estuaries

“…The residence time of the river impacted waters significantly influences the proportion of nutrient and DOM uptake in a water body because the inorganic and organic substances entering the coastal zone are either consumed by phytoplankton and heterotrophic bacteria or undergo dilution by mixing with seawater with lower nutrient concentrations depending on load and season (Ferguson et al 2004). The longer a water mass remains within a coastal ecosystem, the higher the proportion of nutrient consumption by phytoplankton and production of autochthonous DOM (Dippner et al 2019). In a system such as the Curonian Lagoon with its particularly long residence time the high concentrations could be a result of accumulation of substances over time.…”

“…Photodegradation and flocculation may also play a role for the degradation of DOM (Gustafsson et al 2000). The longer a water mass remains within a coastal ecosystem, the higher the proportion of land-derived nutrient consumption by phytoplankton that leads to the production of autochthonous DOM (Dippner et al 2019). When a freshwater bulge is formed the water can remain for or up to 9 days near the coast as shown for the Gulf of Riga (Soosaar et al 2016) or when an eddy develops water in the Vistula estuary remains up to 1 week (Voss et al 2005).…”

Atmospherically Driven Seasonal and Interannual Variability in the Lagrangian Transport Time Scales of a Multiple‐Inlet Coastal System

“…Depending on a coastal system's particularities, the TTS's variability can be highly affected by tides, freshwater discharge, gravitational circulation, winds, and other factors. The influence of some of these forcing mechanisms on the intra‐annual and the seasonal variability of the TTS has been explored in bights (Zhang et al., 2010), bays (Dippner et al., 2019; Jiang et al., 2019) and lakes (Cimatoribus et al., 2019). However, these studies were based on just 1–2 years of data, and thus, a robust relationship of the seasonality with the local forcing cannot be expected if there is a marked interannual variability.…”

Atmospherically Driven Seasonal and Interannual Variability in the Lagrangian Transport Time Scales of a Multiple-inlet Coastal System

“…Depending on a coastal system's particularities, the TTS's variability can be highly affected by tides, freshwater discharge, gravitational circulation, winds, and other factors. The influence of some of these forcing mechanisms on the intra-annual and the seasonal variability of the TTS has been explored in bights (Zhang et al, 2010), bays (Dippner et al, 2019;Jiang et al, 2019) and lakes (Cimatoribus et al, 2019). However, these studies were based on just 1 to 2 years of data, and thus, a robust relationship of the seasonality with the local forcing cannot be expected if there is a marked interannual variability.…”