Abstract
A RCP4.5 simulation from the Community Earth System Model was downscaled by the Weather Research and Forecasting Model, inline coupled with chemistry, to examine how climate change may affect inversions and visibility in Glacier Bay in the presence of cruise-ship visitations. Mean downscaled climate conditions for the tourist seasons for 2006-2012 were compared with downscaled conditions for 2026-2032 with identical cruise-ship entries and operating conditions thereby isolating pollutant retention and visibility differences caused by atmospheric climate change. Notable changes in future temperature, humidity, precipitation, and wind-speed occurred for large areas of Southeast Alaska and the Gulf of Alaska, although the anticipated differences were less pronounced in Glacier Bay due to the presence of the large glaciers and ice fields. While increased sensible heat and water vapor in the atmospheric boundary layer contributed to on average 4.5 h reduced inversion duration in Glacier Bay, the on average 0.23 m·s-1 reduced wind speeds increased inversion frequency by 4% on average. The future on average wetter conditions and altered precipitation patterns in Glacier Bay affected the removal of gases and particulate matter emitted by cruise ships locally or advected from areas outside the park. Season-spatial averaged visibility in Glacier Bay remained the same. However, visibility was degraded in the future scenario later in the season and slightly improved during spring. The warmer conditions contributed to decreased visibility indirectly by tieing up less NO2 in PAN and increasing biogenic NOx emissions. The wetter conditions contributed to reduced visibility in the last third of the tourist season.
Highlights
Climate change is expected to have direct and profound impacts on the hydrological and biogeochemical cycles, species abundance and distribution, and the physical template of polar and sub-polar regions [1]
This landward increase in 2 m air temperatures in response to climate change agrees with findings of other downscaling studies performed along the Pacific Coast (e.g. [55])
While the representation of biogenic emissions [48] used in our study considers the link between increased temperature and increased volatile organic compounds (VOC) emissions, substantial uncertainty remains as ambient CO2 concentrations may affect isoprene emissions in a nonlinear way [60]
Summary
Climate change is expected to have direct and profound impacts on the hydrological and biogeochemical cycles, species abundance and distribution, and the physical template of polar and sub-polar regions [1]. In Alaska and across the northern hemisphere, climate change has resulted in rapid and unprecedented loss of ice-sheet thickness [7] These contemporary, and the anticipated future, conditions increasingly serve as a catalyst for “last chance” tourism [8] wherein people choose to visit destinations like Glacier Bay that are likely to be lost or fundamentally different in the near future. We used CESM data and WRF/Chem to downscale regional climate over Southeast Alaska to examine the near-term impacts of climate change on inversions, air quality and visibility during tourist seasons over Glacier Bay waters. To achieve our goal we determined the inversion and visibility climatologies from downscaled CSEM data for the length of seven past (2006-2012) and seven future (2026-2032) tourist seasons (May 15 to September 15), and analyzed them for changes
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