Synergy between sampling strategies
While the FerryBox approach can provide good temporal resolution along a defined route, spatial extrapolation of such observations needs to be carried out with caution. One approach to enhance the information derived from FerryBox measurements is to combine with information derived from other platforms. For example, the spatial restriction of a FerryBox to the transect can be overcome for certain parameters such as chlorophyll and suspended matter by combining with results from remote sensing. For example, the spatial distribution of chlorophyll-a concentration derived from ENVISAT-MERIS (algal-2 for case-2 water) for the North Sea in May 2005 and the chlorophyll fluorescence, dissolved oxygen (DO) and pH along the track measured by the FerryBox on the same day that the satellite image was recorded. From the image the spatial extent of the algal bloom in the English Channel region (3.3°E – 4.2°E) can be clearly seen. The bloom along the Dutch coast (4.8°E – 6.5°E) began in April and was already diminishing in May as evidenced by the increased patchiness. The activity of the algal bloom is also reflected by DO concentration along the track. High over-saturation of oxygen indicates photosynthetically active blooms in the English Channel and in the Elbe estuary (8°E – 8.7°E). In contrast, along the Dutch coast the oxygen levels are lower possibly due to oxygen consumption (DO 90 – 100%) and indicative of a collapse of the bloom in this region.
Chlorophyll-a concentration derived from ENVISAT-MERIS (algal-2 for case-2 water) for the North Sea and comparison with chlorophyll-a fluorescence, oxygen saturation index and pH along the track of the ferry (black line) on 28th of May 2005.
In this example, we demonstrate the way in which combining data from different platforms, with different spatial and temporal characteristics, enables us to improve the overall picture of environmental state. Clearly, there are times when observations are not available from one platform, for example, when clouds interfere with ocean colour measurements. A further example of the synergy to be derived from multi-platform observations is the potential for using in situ observations for ground-truth purposes. These examples demonstrate that effective monitoring requires a range of observational strategies. EMECO will provide a mechanism to identify opportunities for synergy between programmes operated around the North Sea by a range of different organisations and countries.
A further example of the synergy that may be achieved between, in this case, remote sensing, in situ observations and model predictions from several sources is illustrated from multi-national work focussed on the German Bight. Phytoplankton biomass is shown for the German Bight at midday 8 November 2005 (Figure 8). A MERIS image processed by NERSC shows chlorophyll concentration (increasing from lighter to darker). Overlaid are contour lines of phytoplankton concentration and surface current (black arrows) from the operational met.no/IMR (Norwegian Meteorological Office /Institute of Marine Research [Bergen]) coupled ecosystem model (shown are 25-hour mean fields). Also shown are tide gauge observations of sea level anomaly, provided by BSH (Germany) and DMI (Denmark). All data are collated in near-real-time at the Norwegian Meteorological Office (NMO) and displayed in the visualisation tool DIANA. NERSC provides MERIS images daily for the previous day. The NMO runs the ecosystem forecast model daily, with physical lateral boundary conditions provided by the UK Met Office (FOAM N. Atlantic) and by SMHI (in the Kattegat). Near-real-time tide gauge data are also provided for UK, Norwegian, Swedish and Dutch stations. Data exchange has been facilitated through the EuroGOOS NOOS (North West Shelf Operational Oceanographic System) projects, MERSEA (EU project) and MONCOZE (Norwegian national project). Monitoring products for the northern North Sea are updated regularly for viewing at http://moncoze.met.no.
A composite image showing MERIS derived chlorophyll-A in November 2005, increasing in concentration from blue to green to yellow to red together with hourly tide gauge data.
