David E. Atkinson

Overview of Bering and Chukchi Sea Wave States for Four Severe Storms following Common Synoptic Tracks

AbstractStrong storms occur regularly over the ocean west of Alaska. These systems often loiter, generating persistent winds that can result in fully developed marine states that can maximize damage and hazard potential. Detailed analyses of storm events in terms of the resultant wave states are uncommon. This analysis examines the wave states associated with four particular storm events over the Bering and Chukchi Seas: October 2004, September 2005, and November 2009, and a September 2011 event that exhibited north winds. For each event a brief synoptic overview is presented followed by consideration of the resultant wave state, including parameters such as wave steepness. Wave data come from NOAA’s WAVEWATCH III (WW3) operational global ocean wave model, implemented for scenario use at the Arctic Region Supercomputing Center at the University of Alaska Fairbanks. In situ data are available from several National Data Buoy Center buoys and a wave buoy located in the Bering Strait, funded by the U.S. Envir...

Identification and classification of storm surge events at Red Dog Dock, Alaska, 2004–2014

Powerful storms in the Bering and Chukchi Seas west of Alaska frequently bring high winds that drive positive and negative surge events (storm surges). Positive surge events can cause inundation of coastal regions, extending far inland in low-relief locations. A 10-year record (2004–2014) of water level data from Red Dog Dock located to the north of the Bering Strait on the Alaskan coast was analysed for observed severe surge events. A climatology of events was developed, in which event occurrences were grouped by temporal evolution of the event. The length of time (speed) it took for a given storm system to move over the region largely dictated the temporal evolution of the surge events. The mapped time series evolution of the measured storm surge was grouped into four distinct surge event types. The primary synoptic control on these events is the orientation of the pressure gradient caused by the passage of low-pressure systems. The orientation of the pressure gradient, and therefore dominant wind direction, determine the magnitude, duration, and positive or negative storm surge inundation. The climatology resulted in 44 observed events—21 positive, 23 negative—that tended to occur during the months of November, December, and January. It was also noted that surges also regularly occurred when sea-ice cover was present. The primary synoptic forcing mechanism for positive surges was an extra-tropical cyclone positioned over the North Bering Sea/Chukotka Peninsula area, and for negative surges, an extra-tropical cyclone positioned over the Alaska Peninsula/western Gulf of Alaska.

ENSO climate risk: predicting crop yield variability and coherence using cluster-based PCA

The El Niño–Southern Oscillation (ENSO) has, in recent years, contributed to increases in the yields of major agricultural (annual) crops like wheat and barley in Canada. How such forcing alters the pattern of yield variation across different geographic scales and across large agricultural landscapes like the Canadian Prairies is less understood. Yet, such questions are of major importance in forecasting future cereal crop production. We explore the potential impact of ENSO on wheat and barley across the Canadian Prairies/Western Canada using a multi-scale, cluster-based principal component analysis (PCA) model that integrates machine-learning (K-means clustering) to predict areas of high climate risk. These risk areas are separable clusters of subregions that show similar ENSO-yield correlation response (spatial coherency). Benchmarking this spatial model to non-spatial models indicates that spatial coherency leads to gains in prediction skill. Incorporating spatial coherency increased the skill in predicting crop yield; reducing RMSE error by up to 26–34% (spring wheat) and 2–4% (barley). We infer that accounting for spatial coherency improves the accuracy and reliability of crop yield forecasts.

Physical Climate Forces

More than 50 percent of Americans live in coastal watershed counties, a percentage that continues to increase (see section 1.3). In addition, the coast is home to the majority of major urban centers as well as major infrastructure such as seaports, airports, transportation routes, oil import and refining facilities, power plants, and military facilities. All of these human uses, which represent trillions of dollars in economic investment as well as valuable coastal ecosystems, are vulnerable in varying degrees to rising global temperature and hazards such as sea-level rise, storms, and extreme floods. Intense human activity over the past century has degraded many coastal environments and stressed natural ecosystems. Nationwide, nearshore areas and estuaries are polluted with excess nitrogen and other chemicals, toxic coastal algal blooms are increasing, fish stocks are depleted, wetland loss has been dramatic, and coral reefs are bleached and dying. Climate change exacerbates these stresses on ecosystems.