Oceana Francis

An inverse modeling study of circulation in the Eastern Bering Sea during 2007-2010

A two-way nested 4d-variational data assimilation system is implemented in the Eastern Bering Sea (EBS) to investigate changes in circulation and thermodynamic state for a 3.8-year period. Assimilated observations include data from 19 moorings deployed on the shelf and in the Bering Strait, 1705 hydrographic stations occupied during eight surveys, and remotely sensed sea surface temperature and sea surface height (SSH) data. Validation of the presented 4dVar reanalysis against the output of two sequential data-assimilative systems (the Bering Ecosystem Study ice-ocean Modeling and Assimilation System (BESTMAS) and the Arctic Cap Nowcast-Forecast System (ACNFS)) has shown that the product is more consistent with the observed transports in the Bering Strait and in the EBS interior both in terms of their magnitude and time variability. Analysis of the data-optimized solution quantifies a sequence of wind-forced events that resulted in the anomalous heat and freshwater transports through the Bering Strait, including a 28-day long flow reversal that occurred in November of 2009 and carried Siberian Coastal Current water down to the Gulf of Anadyr. Lagrangian study of the Arctic-bound Pacific waters indicates the extreme importance of the cross-shelf exchange along the path of the Bering Slope Current and quantifies the spectrum of residence times for the waters entering EBS through Unimak Pass and through Aleutian passages. Residence times in the EBS cold pool are diagnosed to be 2-3 times longer than those in the surrounding waters. This article is protected by copyright. All rights reserved.

Learning to Build Resilience into Transportation Systems

There is increased recognition of the value of resilience thinking yet few studies have examined key experiences and lessons for the transportation industry. This paper presents eight case studies on natural and man-made disasters focusing on transportation impacts, lessons learned, and efforts to increase resilience. The cases are the Atlanta snowstorm, I-35W bridge collapse, Boston Marathon bombing, Puna lava highway closing, superstorm Sandy, Hampton Roads sea level rise study, Fukushima disaster, and the Oregon Resilience Plan. The cases are used to inform transportation agencies to better respond to and recover from disasters, as well as improve the resilience of transportation systems. In addition to integrating resilience into the management of transportation assets, new technologies and tools relevant to transportation resilience are described.

The Bering Sea Regional Data Assimilation System: From Climate Variability to Short Term Hindcasting

We present a regional Data Assimilation System (DAS), which employs the 4-dimensional variational (4dVar) DA approach based on the strong dynamical constraints of a semi-implicit primitive equation model. The developed 4dVar DAS is applied to the Bering Sea in several configurations. First, it is used for the reconstruction of seasonal and annual mean climatological states in the region, including the high resolution mean dynamical ocean topography (MDOT). The dynamically and statistically consistent climatologies are then utilized in various applications, including high-resolution analyses of the transport through the passage of the Aleutian Arc, and of the 2007–2010 circulation on the East Bering Sea shelf with the nested configuration of the DAS. Apart from new insight on the Bering Sea dynamics, the chapter illustrates the importance of developing dynamically consistent climatologies and, in particular, MDOT, for the analysis of the diverse data sets within a wide spectrum of spatial and temporal scales.