Abstract
In Glacier Bay National Park, about 95% of the visitors come on board of cruise ships. The National Park Service has the mandate to manage park resources like air quality and visibility, while ensuring visitation. To understand the impact of cruise-ship emissions on the overall concentrations in Glacier Bay, emission-source contribution ratios (ESCR) and the interaction of pollutant from local and/or distant sources were determined using results from four WRF/Chem simulations of the 2008 tourist season (May 15 to September 15). These simulations only differed by the emissions considered: Biogenic emissions only (CLN), biogenic plus activity-based cruise-ship emissions (REF), biogenic plus all anthropogenic emissions except cruise-ship emissions (RETRO), and all aforementioned emissions (ALL). In general, ESCRs differed among pollutants. Interaction between pollutants from cruise-ship emissions and species from other sources including those advected into the bay decreased towards the top of the atmospheric boundary layer. Pollutants from different sources interacted strongest (lowest) in the west arm of the fjord where ships berthed for glacier viewing (in areas of the bay without cruise-ship travel). Pollutant interaction both enhanced/reduced NO2 concentrations by 10% (4 - 8 ppt absolute). Except for ozone, cruise-ship emissions on average governed air quality in the bay. On days with cruise-ship visits, they contributed between 60% and 80% of the bay-wide daily mean SO2 and NO2 concentrations below 1 km height. On days without visits, cruise-ship contributions still reached 40% due to previous visits. Highest cruise-ship ESCRs occurred during stagnant weather conditions. Despite the fact that all coarse particulate matter was due to anthropogenic sources, worst visibility conditions were due to meteorology. The results suggest limits as well as windows for managing air quality and visibility in Glacier Bay.
Highlights
In recent years, the phenomenon of “last chance tourism” has increased
Comparison of the REF and RETRO seasonal mean profiles of SO2 over the Glacier Bay water proper (Figure 2) reveals that transport of pollutants from other sources than cruise ships contributed to the all emission sources (ALL) concentrations in the maritime atmospheric boundary layer (ABL), and up to 700 hPa (~3 km above sea level)
The limits of managing air quality are set by the contribution of the emission sources under control to the total concentrations of the species
Summary
The phenomenon of “last chance tourism” has increased. people wish to visit places such as the Arctic, Antarctic, and tidewater glaciers, which they anticipate to be irreversibly impacted by climate change, before they are gone [1] [2] [3]. Air-quality model simulations demonstrated that along the Norwegian coast, local ship emissions increased the 15-day mean near-surface concentrations of NOx, ozone (O3), BC and particulate matter of 2.5 μm or less in diameter (PM2.5) up to 80%, 5%, 40% and 10%, respectively [17] Given these results, and the dual mandate of the NPS, we examined the limits to which the NPS can manage/control air quality successfully in Glacier Bay. While the NPS can regulate the number of cruise ships that enter the park, set entrance quota and/or speed limits, and set up competitive contracts that result in ships using low sulfur fuel [18], the NPS cannot control inversions, precipitation, biogenic emissions, or the advection of pollutants from emissions outside of the park boundaries. We compared the Southeast Alaska and bay-wide mean concentrations in the ABL as they should differ when cruise-ship emissions are the main source for pollutants in the bay
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