Remote Sensing of Coastal Upwelling in the South-Eastern Baltic Sea: Statistical Properties and Implications for the Coastal Environment

Abstract

A detailed study of wind-induced coastal upwelling (CU) in the south-eastern Baltic Sea is presented based on an analysis of multi-mission satellite data. Analysis of moderate resolution imaging spectroradiometer (MODIS) sea surface temperature (SST) maps acquired between April and September of 2000-2015 allowed for the identification of 69 CU events. The Ekman-based upwelling index (UI) was applied to evaluate the effectiveness of the satellite measurements for upwelling detection. It was found that satellite data enable the identification of 87% of UI-based upwelling events during May-August, hence, serving as an effective tool for CU detection in the Baltic Sea under relatively cloud-free summer conditions. It was also shown that upwelling-induced SST drops, and its spatial properties are larger than previously registered. During extreme upwelling events, an SST drop might reach 14 • C, covering a total area of nearly 16,000 km 2 . The evolution of an upwelling front during such intensive events is accompanied by the generation of transverse filaments extending up to 70 km offshore. An analysis of the satellite optical data shows a clear decline in the chlorophyll-a concentration in the coastal zone and in the shallow Curonian Lagoon, where it drops down by an order of magnitude. It was also shown that a cold upwelling front alters the stratification in the atmospheric boundary layer, leading to a sudden drop of air temperature and near-surface winds.upwelling fronts also importantly modifies the vertical stratification and turbulent regime in the marine-atmosphere boundary layer (MABL), resulting in a change in the surface wind stress and direction in the coastal zone [3,9].Nutrient-rich waters brought up from deeper layers to the surface, particularly in the summer time, and the exposure of upwelled phytoplankton to surface radiation enhances the primary production and phytoplankton biomass during upwelling events [10,11], hence influencing the coastal pelagic communities and higher trophic levels [12]. Moreover, upwelling-related coastal ocean dynamics may eventually modify the spatial patterns of background algae blooms in the coastal zone by transporting them farther offshore.During the summer-time holiday season, CU might also have a negative impact on particular tourist areas as a result of a rapid drop in water and air temperatures near the shore [2]. Furthermore, bathing tourism depends on good water quality, while post-upwelling phytoplankton blooms might significantly reduce it, making coastal waters unattractive for recreation [13].The need to study coastal upwelling in the Baltic Sea is also essential in order to assess the regional variability of water and energy exchange, salinity dynamics, and the response of marine ecosystems to extreme events-some of the "Grand Challenges" of the Baltic Earth Science Plan [14], established in 2016. Thus, the upwelling phenomenon is indeed of certain interest to researchers, fishermen, and coastal managers [15]. The availability of wide spatial and temporal co...

Wind-Driven Coastal Upwelling near Large River Deltas in the Laptev and East-Siberian Seas

“…Tidal circulation is very low in the central part of the Laptev Sea and limitedly affects mixing at the study area [62,65]. Coastal upwelling events are commonly manifested by cold and turbid zones in satellite imagery in many world regions [95][96][97][98]. Distributions of sea surface temperature observed during coastal upwelling events show significant dependence on local bathymetry.…”

Remote Sensing of Ice Phenology and Dynamics of Europe’s Largest Coastal Lagoon (The Curonian Lagoon)

“…During wintertime, the Curonian Lagoon becomes famous for ice fishing, being, however, a dangerous leisure, since strong winds can break off the ice fields and drift them away from the shore together with the fishermen. With the changing climate resulting in warmer weather and more unstable ice cover, such incidents might increase in the future and require detailed information on the ice cover to plan rapid rescue missions.In the south-eastern Baltic (SEB), where the Curonian Lagoon (CL) is located, spaceborne SAR observations have been already used before to study the coastal upwelling and its environmental implications [24,25], monitoring of cyanobacteria blooms [26], and short-term mapping of ice conditions for planning potential zebra mussel farms [27]. However, the comprehensive use of spaceborne SAR data for detailed analysis of ice conditions in the Curonian Lagoon and the SEB is still lacking.…”

“…In the south-eastern Baltic (SEB), where the Curonian Lagoon (CL) is located, spaceborne SAR observations have been already used before to study the coastal upwelling and its environmental implications [24,25], monitoring of cyanobacteria blooms [26], and short-term mapping of ice conditions for planning potential zebra mussel farms [27]. However, the comprehensive use of spaceborne SAR data for detailed analysis of ice conditions in the Curonian Lagoon and the SEB is still lacking.…”

Combining Satellite Imagery and Numerical Modelling to Study the Occurrence of Warm Upwellings in the Southern Baltic Sea in Winter

“…Studies carried out in the summer showed upwelling to be an important process affecting water mixing and coastal weather [4][5][6][7]. The upwelled water is usually nutrient-rich; therefore, upwelling affects primary production and the phytoplankton biomass [6,[8][9][10][11]. and frequency in winter.…”