The winters of 1999–2002 for the North Pacific were characterized by spatial patterns in sea level pressure anomaly (SLPA) and sea surface temperature anomaly (SSTA) with little resemblance to those of the leading pattern of North Pacific climate variability, the Pacific Decadal Oscillation (PDO). In essence, the southeastern (northern) portion of the North Pacific was subject to atmospheric forcing characteristic of that before (after) the major regime shift of 1976–77. Recent major changes in the ecosystems off the west coast of the United States and continued conditions similar to those of the early 1990s in the Gulf of Alaska, Bering Sea, and Sea of Okhotsk are consistent with these SLPA and SSTA patterns. Our result illustrates that a single indicator such as the PDO is incomplete in characterizing North Pacific climate.

[1] We have developed a method to compute the total energy transmitted by tsunami waves, to the case where the earthquake source is unknown, by using deep-ocean pressure measurements and numerical models (tsunami source functions). Based on the first wave recorded at the two closest tsunameters (Deep-Ocean Assessment and Reporting of Tsunamis (DART)), our analysis suggests that the March 11, 2011 Tohoku-Oki tsunami generated off Japan originated from a 300-400 km long and 100 km wide area, and the total propagated energy is 3 Â 10 15 J (with 6% uncertainty). Measurements from 30 tsunameters and 32 coastal tide stations show excellent agreement with the forecasts obtained in real time. Our study indicates that the propagated energy and the source location are the most important source characteristics for predicting tsunami impacts. Interactions of tsunami waves with seafloor topography delay and redirect the energy flux, posing hazards from delayed and amplified waves with long duration. Seafloor topography also gives its spectral imprint to tsunami waves. Travel time forecast errors are path-specific and correlated to the major wave scatterers in the Pacific. Numerical dissipation in the propagation modeling highlights the need of high-resolution inundation models for accurate coastal predictions. On the other hand, it also can be used to account for physical dissipation to achieve efficiency. Our results provide guidelines for the earliest reliable tsunami forecast, warnings of long duration tsunami waves signals and enhancement of the experimental tsunami forecast system. We apply the method to quantify the energy of 15 past tsunamis, independently from earthquake magnitudes. The small tsunami to seismic radiation energy ratios, and their variability (0.01-0.8%), reinforce the importance of using deep-ocean tsunami data, the direct measures of tsunamis, for estimates of tsunami energy and accurate forecasting.

Historical surface air temperature (SAT) records from 59 Arctic stations north of 64°N show monthly anomalies of several degrees and large spatial teleconnectivity yet major seasonal and regional differences, based on time/longitude plots of SAT anomalies and Principal Component Analysis (PCA). Using monthly station data rather than gridded fields for this analysis highlights the importance of considering record length in calculating reliable Arctic change estimates; for example, we contrast PCA performed on 11 stations beginning in 1886, 20 stations beginning in 1912, and 45 stations beginning in 1936. While often there is a well-known interdecadal negative covariability in winter between Scandinavia and Baffin Bay in the historical SATs, long-term changes in the remainder of the Arctic are most evident in spring, with cool temperatures before 1920 and Arctic-wide warming in the 1990s. Summer anomalies are generally weaker than spring or winter but tend to mirror spring conditions before 1920 and in recent decades. Temperature advection in the trough-ridge structure in the positive phase of the Arctic Oscillation (AO) in the N. Atlantic establishes wintertime temperature anomalies in adjacent regions, while the zonal/annular nature of the AO in the remainder of the Arctic must break down in spring to promote meridional temperature advection. There are regional/decadal warm events during winter and spring in the 1930s to 1950s, but meteorological analysis suggests that these SAT anomalies are the result of intrinsic variability in region flow patterns. The mid-century events contrast with an Arctic-wide AO influence in the 1990s. We also present a conceptual model for decadal variability of the Arctic system consisting of chaotic behavior of the polar vortex. Regional feedbacks in the Arctic can act as partial multi-year memory for the vortex through amplification of ocean/sea-ice/land-vegetation changes, while the vortex in turn is often driven by north/south differences in radiational forcing from CO 2 , aerosols, solar absorption and volcanic influence. The preponderance of evidence supports the conclusion that warm SAT anomalies in spring for the decade for the 1990s had the greatest longitudinal extent in the instrumental record.

At 23:41 UTC on 15 August 2007, an offshore earthquake of magnitude 8.0 severely damaged central Peru and generated a tsunami. Severe shaking by the earthquake collapsed buildings throughout the region and caused 514 fatalities. The tsunami resulted in three casualties and a representative maximum runup height of ∼7 m in the near field. The first real‐time tsunami data available came from a deep‐ocean tsunami detection buoy within 1 hour of tsunami generation. These tsunami data were used to produce initial experimental forecasts within 2 hours of tsunami generation. The far‐field forecasts indicated that the tsunami would not flood any of the 14 U.S. communities. Comparison with real‐time tide gage data showed very accurate forecasts.