31 Dec 2001

Climate Changes & Primary Production in Danish Coastal Waters

The impact of climate changes is becoming an increasingly important issue in public awareness.

The impact of climate changes is becoming an increasingly important issue in public awareness. Up to now, the effects of climate change in coastal areas have in Denmark focused on the impacts of a rising sea level on coastal morphology and the marine infrastructure. However, preliminary evaluations of the possible effects of climate change on the productivity of the coastal waters around Denmark stresses the importance of including ecological considerations in future assessments of potential impacts.

The Farvandsmodel, which DHI Water & Environment has developed and now operates for the Danish Ministry of Environment and Energy as part of the NOVA Programme ('The Danish Aquatic Monitoring and Assessment Program 1998-2003), has at DHI's initiative recently been expanded with a eutrophication module. This gives a unique opportunity to include environmental aspects of climate change, such as algae growth and primary production. Hence, a number of scenarios were designed based on predictions of future climate changes, some of which are presented by DMI/Danish Climate Centre to test the sensitivity of the ecological parameters of Danish coastal waters.

The average percentage increase in winter concentrations (January & February) of inorganic nitrogen (left figure) and the average percentage increase in daily primary production (right figure) during the growth period (March - September) due to an increased precipitation over Denmark and, hence, an increased run-off from the Danish Catchment areas.

The effects of increased precipitation, increased temperatures and increased UVB radiation on the productivity were modelled using the Farvandsmodel. The results of this preliminary evaluation are reported in the publication ‘Impacts of climate Change’, to be published at the beginning of 2001 by the Danish Climate Centre situated at the Danish Meteorological Institute (DMI).

The effects on the primary production and, hence, on the Danish coastal environment are summarized in the diagram to the right.

These results are interesting, as it has been observed that, due to the dry years (1996 & 1997) and the wet years (1998 & 1999), the environmental aspect, such as oxygen depletion in the Danish coastal waters, is strongly affected by the precipitation over Denmark.

Summary of envisaged effects from model simulations: Carbon production during growth season March - September.

This observed relationship supports the conclusions drawn from this initial sensitivity analysis and it also emphasizes the fact that, when talking of climate changes, coastal ecology should also be included. Even though the temperature scenario is overestimated due to the model not yet having reached equilibrium with regard to the release of inorganic nutrients from the sediment to the water phase during the summer, the envisaged effects imply more eutrophicated areas in the future, especially near the shore. This may result in more frequent occurrences of oxygen depletions.

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