Future Climate Conditions for the Cook Inlet Watershed
Global climate change will impact local communities on different timescales and in different ways. To help Alaskans understand predicted changes at local scales, Scenarios Network for Alaska Planning (http://www.snap.uaf.edu/) is working with partners to provide regional maps and projections of future climate conditions. SNAP climate projections are based on the five best-performing Global Circulation Models (GCM's) used by the Intergovernmental Panel on Climate Change (IPCC), previously identified as a best fit for Alaska. These models are scaled down to 2 km resolution using the PRISM model. The IPCC created a range of scenarios to explore alternative development pathways, covering a wide range of demographic, economic and technological driving forces and resulting greenhouse gas emissions. The A2 scenario describes a very heterogeneous world with high population growth, slow economic development and slow technological change. The A1B scenario assumes a world of very rapid economic growth, a global population that peaks in mid-century, rapid introduction of new and more efficient technologies, and a balance between fossil fuels and other energy sources. Current trends indicate that the world may be headed somewhere between these two scenarios in terms of greenhouse gas emissions and global climate change.
In 2010, as part of the Stream Temperature Monitoring Network, Cook Inletkeeper and The Nature Conservancy of Alaska worked with Scenarios Network for Alaska Planning (SNAP) to illustrate future scenarios of air temperature and precipitation conditions in the Cook Inlet watershed. SNAP created maps for both the A2 and A1B scenarios based on a composite (mean) of all five model outputs from 2000 to 2100. Cook Inlet maps and point data for each temperature monitoring site were generated of monthly averages for air temperature (degrees C) by decade; monthly averages for precipitation (cm) by decade; seasonal averages for air temperature and for precipitation by decade, where seasons are defined as follows: Spring (March - May) Summer (June-Aug) Autumn (Sept- Nov) Winter (Dec - Feb); and mean thaw date by decade. Examples of these maps, showing average values from projections for the mid-range scenario (“A1B”), can be found below.
This animation of decadal averages of July air temperature shows a strong upward trend throughout the entire Cook Inlet watershed. Air temperatures should continue to be warmer in the Mat-Su basin than on the southern Kenai Peninsula. By 2090-2099, average July air temperatures in the Susitna River valley are predicted to be over 19oC, which would be a 5oC (9oF) increase from 2008-2009.
Increases in air temperature are predicted for all seasons, but the most dramatic change will likely be in the winter. This animation of decadal averages of winter air temperatures shows an upward trend particularly in the lower Cook Inlet. By 2090-2099, average winter temperatures on the lower Kenai Peninsula and the west side of Cook Inlet may be above freezing, which could result in significant reductions in snow accumulation.
Based on our current knowledge of the relationship between air and water temperature in Cook Inlet salmon streams, these climate conditions will likely result in increased stream temperatures in non-glacial systems. We will develop stream-specific predictions for future water temperatures, which will increase our understanding of the rate of rising stream temperatures and identify streams with the greatest potential for thermal stress.