Coastal Zones (First session)

Discussion Leaders: Ray Najjar and Hal Walker, Notes by Jody Gibson

1. Coastal sand budget: Sediment can be good! Since colonial times, deforestation has changed SRB sediment delivery to the coasts. However, this change is fairly irrelevant for barrier islands. Might classify suspended sediment load by grain size in Chesapeake Bay, because this would have direct effects on light attenuation and SAV. Water clarity in the northern half of the Bay is stable, but it is decreasing in the southern half, perhaps because of sediment grain size dynamics and/or dissolved organic matter.

2. Sea level rise: Maps (namely GIS images) would help convey beach/property susceptibility to climate change. Regional SLR estimates must "mesh" with IPCC projections. Last month's Atlanta meeting included mention of a southeastern coastal renourishment project, costing approx. $1 million per coastal mile every third year, was mentioned. Similar projects are estimated to be essentially 10 times more costly. Maryland shores replenishments failed miserably in the midst of strong storms. The location of sewage treatment plants should be a concern, particularly because flood plains are expected to expand.

3. SAV: water turbidity is a significant problem. There is positive feedback between turbidity and SAV loss.

4. Air and water temperatures: During 1984-1995, air temperatures over the Bay increased, but water temperatures actually DECREASED in all seasons except winter. We are in a lull now with respect to hurricanes. The MAR is subject to complex climatic patterns (meridional versus zonal) that can cloud apparent trends over relatively short time scales. Droughts are likely to be much more severe, yet more punctuated, in the future. Thus although the climate is expected to get wetter in the MAR, we should PREPARE for dry conditions. The analogy for the southwest US: the worst thing that could happen would be a wetter climate, and this is what they should prepare for.

5. Accuracy in climate models. Look at the southeastern US for a safe, first-order approximation to climate change in the MAR. In a higher CO2 world, we shouldn't expect as much evapotranspiration, which will affect flow regimes. Longer- term trends are lacking in the computer models; we especially need downscaled accuracy. Fortunately, this is a hot area of research, and thus likely to improve in the next 4 years.

6. Ecosystem migration is very dependent on land development. "Smart growth" and deliberate buying of land by the government are options for protecting ecosystems.

7. More emphasis on state-by-state assessments in our draft--because of political boundaries and because of sub-regional differences in response.

8. Publications: think about sending out SEVERAL versions of the coastal manuscript, not just to Climate Research.