News / Research Highlights / Coastal Climate

Coastal Climatology and Extreme Weather Events in Alaska and the Arctic

March 31, 2005

Coastal communities in Alaska are subjected to periodic weather events that can take on an "extreme" and dangerous nature.   Water ran through the streets of Nome, AK on October 19, 2004, when a powerful winter storm moved in from the Aleutian Islands.   Driven by heavy moisture from a typhoon east of Japan and cold air from Far East Russia, the storm lowered air pressure to 941 millibars (mb), well into hurricane strength, and pounded western Alaska with 50 to 80 mph winds.   Nome, a coastal city of 3500 people, reported gusts up to 59 mph, comparable to another powerful storm in November of 1974.   The storm surge height reached 10.45 feet, sending waves over the sea wall and into the city.   Storm surge, water that is pushed toward shore by wind force, can combine with normal tide to create extremely high tidewater and represents the most destructive aspect of coastal storms.   In comparison, the storm surge height of the 1974 storm was 10 feet. The Fairbanks National Weather Service (NWS) Storm Data and Unusual Weather Phenomena report for October, 2004 estimated overall storm damages at approximately $20 million, with Nome incurring the bulk of the damage.  

When severe storms happen in populated areas there is significant impact on residents and infrastructure.   During the October 2004 storm in Nome, forty-five people had to be evacuated and thirteen homes were damaged. Other homes near Front Street were vacated because of leaking propane tanks from nearby businesses. Many city buildings suffered structural damage, including the State building, the historic Cape Nome Road House, and the water treatment system.   Power lines were downed, roofs blown off, and rocks and driftwood were scattered over the main street and against buildings.   The seawall that protects the harbor was also damaged.

Atmospheric scientists categorize this type of weather as an "extreme event."   In general, the term "extreme event" covers a variety of weather occurrences over a range of time frames, from single events to unusual changes in climate variability, lasting days or weeks. Examples include heavy rains, dry spells, strong storms and winds, and extreme temperatures.   Normal air pressure at sea level is 1013.25 mb ("millibars", a unit of pressure measurement), but during severe storms and extreme events, air pressure can drop by 30 to 70 mb, as it did during the Nome storm (Fig. 1). Low pressure also brings strong winds, which is why meteorologists pay close attention to the "central pressure" range of storm systems of all types (Fig. 2).  

Several factors can influence the intensity of northern storms, including temperature, sea ice and wind.   Recent studies have shown a warming trend in the Arctic and decreasing summertime sea ice cover, leaving open water areas along many coastlines.   Sea ice plays a major role in determining the extent of storm impacts on a coastline.   Solid ice cover, and even floating ice, dampens wave activity, reducing its intensity. By contrast, in areas of open water, nothing limits the full development of wind-driven waves. The presence of "land-fast" sea-ice, which is sea-ice bonded to the coast, also limits the effects of coastal erosion by directly protecting the coastline from waves.   Surface air temperature projections, derived from several climate models of the Arctic, predict that the warming trend will continue (Fig. 3). Such a trend could result in increasing the frequency of extreme weather events and the coastal flooding and erosion associated with these events.

International Arctic Research Center (IARC) Chief Scientist John Walsh and Atmospheric Sciences researcher David Atkinson are leading a study, funded by the National Science Foundation (NSF), titled "Extreme Events in a Changing Arctic Climate."   Researchers are developing computer climate models that incorporate extreme weather events and are evaluating simulations of extreme temperatures and precipitation from Arctic Climate Impact Assessment (ACIA) models.   Atkinson also works with the Arctic Coastal Dynamics (ACD) Project, studying coastal dynamics and its relationship to "environmental forcing," which includes forces, like wind, that can drive extreme climate events.

A newly proposed study will focus on wind and wave activity along Alaskan coastlines, as well as the marine and coastal ecosystem. Alaska has a shoreline of over 33,000 miles (including islands), more than the rest of the combined United States, and with the effects of climate change becoming noticeable, coastal studies are a timely and important area of research.   In addition, the Alaskan shoreline is subjected to a wider range of climatic effects, including sea ice, than many other areas.  

The project will include both observation studies and computer climate modeling.   Researchers will coordinate with the Alaska Ocean Observing System (AOOS) to identify suitable locations for sea buoys and to gather data on water temperature and salinity, wave height, wind speed and direction.  

On the modeling side, IARC scientist David Atkinson will perform ongoing data analysis and computer modeling of coastal processes and erosion.   IARC researchers will work with NOAA's Cooperative Institute for Arctic Research (CIFAR) on climate databases that identify optimum coastal sites for wave-model testing .   One of the project goals is to construct wave and wind models to effectively predict future coastal erosion and flooding in Alaska.   Projected models of coastal erosion will include data on sea ice edge and sea level changes.   They will also use satellite data of surface sea temperature and wind.

Figure 1. Surface sea level pressure plot indicates the strength of the 19 Oct 2004 storm. IARC researchers classified the storm as an 'extreme event,' with a 949 mb cyclone and flooding in Nome, AK.

Figure 2. Windspeed plot of the 19 Oct 2004 'extreme event' that resulted in flooding in Nome, AK.

Figure 3. Projected temperature plot of several climate models indicates a continuing warming trend in the Arctic.

Left: Nome - looking toward airport, normal (photo by John Lingaas, WSO Fairbanks); Right: Nome - looking toward airport during flooding (photo by Jerry Steiger, WSO Nome)

Left: Nome- boat harbor, normal (photo by John Lingaas, WSO Fairbanks); Right: Nome - boat harbor during flooding (photo by Jerry Steiger, WSO Nome)

Front Street, Nome (photos by Jerry Steiger, WSO Nome)

Left: Nome - fuel tanks no longer in use and nearly empty; Right: Wales - playground with driftwood on play equipment. (photos by John Lingaas, WSO Fairbanks)

Left: Shishmaref - abandoned residence long coast; Right: Kivalina - arial view. (photos by John Lingaas, WSO Fairbanks)