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The article of record as published may be found at http://dx.doi.org/10.2172/1330744 This project aims to develop, apply and evaluate a regional Arctic System model (RASM) for enhanced decadal predictions. Its overarching goal is to advance understanding of the past and present states of arctic climate and to facilitate improvements in seasonal to decadal predictions. In particular, it will focus on variability and long-term change of energy and freshwater flows through the arctic climate system. The project will also address modes of natural climate variability as well as extreme and rapid climate change in a region of the Earth that is: (i) a key indicator of the state of global climate through polar amplification and (ii) which is undergoing environmental transitions not seen in instrumental records. RASM will readily allow the addition of other earth system components, such as ecosystem or biochemistry models, thus allowing it to facilitate studies of climate impacts (e.g., droughts and fires) and of ecosystem adaptations to these impacts. As such, RASM is expected to become a foundation for more complete Arctic System models and part of a model hierarchy important for improving climate modeling and predictions. USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23) Naval Postgraduate School, Monterey, CA (United States)

The article of record as published may be found at http://dx.doi.org/10.1029/2011JC007257 Six Arctic Ocean Model Intercomparison Project model simulations are compared with estimates of sea ice thickness derived from pan-Arctic satellite freeboard measurements (2004-2008); airborne electromagnetic measurements (2001-2009); ice draft data from moored instruments in Fram Strait, the Greenland Sea, and the Beaufort Sea (1992-2008) and from submarines (1975-2000); and drill hole data from the Arctic basin, Laptev, and East Siberian marginal seas (1982-1986) and coastal stations (1998-2009). Despite an assessment of six models that differ in numerical methods, resolution, domain, forcing, and boundary conditions, the models generally overestimate the thickness of measured ice thinner than approximately 2 mand underestimate the thickness of ice measured thicker than about approximately 2m. In the regions of flat immobile landfast ice (shallow Siberian Seas with depths less than 25-30 m), the models generally overestimate both the total observed sea ice thickness and rates of September and October ice growth from observations by more than 4 times and more than one standard deviation, respectively. The models do not reproduce conditions of fast ice formation and growth. Instead, the modeled fast ice is replaced with pack ice which drifts, generating ridges of increasing ice thickness, in addition to thermodynamic ice growth. Considering all observational data sets, the better correlations and smaller differences from observations are from the Estimating the Circulation and Climate of the Ocean, Phase II and Pan-Arctic Ice Ocean Modeling and Assimilation System models. ARC-0804180 (M.J.); ARC-0804010 (A.P.); ARC-0805141 (W.M.); ARC080789; ARC0908769 (J.Z.); ARC-0804010; 09-05-00266; 09-05-01231 Approved for public release; distribution is unlimited.

We compare results from six AOMIP model simulations with estimates of sea ice thickness obtained from ICESat, moored and submarine-based upward looking sensors, airborne electromagnetic measurements and drill holes. Our goal is to find patterns of model performance to guide model improvement. The satellite data is pan-arctic from 2004-2008, ice-draft data is from moored instruments in Fram Strait, the Greenland Sea and the Beaufort Sea from 1992-2008 and from submarines from 1975-2000. The drill hole data are from the Laptev and East Siberian marginal seas from 1982-1986 and from coastal stations from 1998-2009. While there are important caveats when comparing modeled results with measurements from different platforms and time periods such as these, the models agree well with moored ULS data. In general, the AOMIP models underestimate the thickness of measured ice thicker than about 2 m and overestimate thickness of ice thinner than 2 m. The simulated results are poor over the fast ice and marginal seas of the Siberian shelves. Averaging over all observational data sets, the better correlations and smaller differences from observed thickness are from the ECCO2 and UW models. NSF ARC-0804180; NSF ARC-0804010; NSF ARC-0805141; NSF ARC080789; NSF ARC0908769; NSF ARC-0804010 Approved for public release; distribution is unlimited.

A decline of the Arctic sea ice in response to a warming climate is assessed in the historical sea ice simulations from state-of-the-art global climate models participating in Phase 6 of the Coupled Model Intercomparison Project (CMIP6). Accurate simulations of sea ice are important for projections of its regional and global effects on the air-sea exchanges, weather, and climate. The timing and rate of simulated sea ice decline is compared with available observations for sea ice area and volume. Analysis indicates multi-model means and long-term trends for these common sea ice metrics are well represented, but the individual CMIP6 model ability to represent the observed accelerated rate in sea ice decline remains a challenge. Local and regional sea ice biases are identified through spatial analysis metrics, like sea ice thickness distribution pattern and sea ice edge analysis. Large model spatial errors imply limitations in or lack of representation of some key physical processes. The oceanic heat transport (OHT) and its forcing of the pan-Arctic sea ice decline are examined as possible model limitations. CMIP6 models show a strong correlation between increasing OHT and decreasing sea ice trends but likely underestimate the northward OHT over the polar cap (70°–90°N). Isolating specific model limitations and identifying possible processes affecting them will guide future model improvements critical to our understanding and projection of Arctic climate change. Commander, United States Navy Approved for public release. Distribution is unlimited.

Observational and modeling studies are conducted to explore the changing physical environment of the western Arctic Ocean and its significance to upper-ocean hydrography and acoustic energy propagation. In-situ observations of temperature and salinity were made as part of the Canada Basin Acoustic Propagation Experiment (CANAPE) pilot study in summer 2015. Sound-speed fluctuations due to internal waves and spice were analyzed to describe spatio-temporal variability. Internal-wave frequency spectra show a spectral slope lower than the Garrett-Munk (GM) model, and the energy level is 4% of the standard GM value. Frequency spectra of spice show a form similar to the internal-wave spectra but with a steeper spectral slope. Several global climate models were evaluated against historical and recent hydrographic observations and found to inadequately represent key upper-ocean hydrographic features. The Regional Arctic System Model (RASM) was used to investigate sensitivity of the simulated upper ocean to various configurations and showed that sub-grid scale brine rejection parameterization, appropriately tuned surface momentum coupling, and increased vertical and horizontal resolution improved model simulation. In both observational and model data sets, a near-surface sound channel is present, the significance and variability of which warrant further in-situ investigations and model improvements. http://archive.org/details/observationsndmo1094551680 Lieutenant Commander, United States Navy Approved for public release; distribution is unlimited.

The Regional Arctic System Model (RASM) is used to investigate the process and frequency of extreme sea ice shear deformation events resulting in pycnocline upwelling due to Ekman pumping as described in McPhee et al. (2005). RASM is a fully coupled land, atmosphere, sea ice, and ocean model with high spatial and temporal resolution. Time series analysis of the upper ocean temperature structure, basal melt rate, total deformation rate, and ice-ocean stress curl yield the identification of individual events. Shear deformation events generate an upper ocean response given a positive ice-ocean stress curl, i.e., induced by counterclockwise rotation in the ice velocity field relative to the underlying ocean. Spatial and temporal characterization of the total deformation rate indicates that fine spatial and temporal resolution, on a statistical scale, is important for the energy budget of the Arctic. Results demonstrate a power law relationship between the mean deformation rate and length scale. This is hypothesized as being due to RASMs fully coupled system allowing for naturally occurring high frequency noise and the cascade of energy among model components. Simulated events are infrequent their relative impact on large scale energy exchange remains undetermined, which warrants further research of these phenomena. http://archive.org/details/anevaluationofse1094527872 Lieutenant, United States Navy Approved for public release; distribution is unlimited.

Sea ice area and thickness have been on the decline in the Arctic over the past several decades. Understanding the role of ice motion, deformation, and export is important to determining if the Arctic will continue toward seasonal ice coverage or if natural variability is capable of reversing this trend. We have analyzed sea ice model output and satellite data to advance the understanding of potentially critical physical processes and feedbacks in the region. In particular, comparisons of RGPS data and sea ice results from ice-ocean and fully coupled regional climate models have been made to evaluate model skill in representing ice kinematics. Both sea ice model configurations maintain a 1/12o (~9km) horizontal spacing and multiple thickness categories in each grid cell. Advanced model representation of sea ice deformations, combined with high spatial resolution, allow direct comparison with satellite data for resolving small-scale linear kinematic features, which contribute to changes in sea ice thickness distribution. These results offer an improved insight into what forces determine the survivability of sea ice in the Arctic. http://archive.org/details/evaluationofseic109456838 Lieutenant Commander, United States Navy

Circulation in the western Arctic Ocean is not well understood. To address some of its outstanding questions, volume transport and property fluxes are investigated using a coupled ice-ocean model of the pan-Arctic region configured at a 1/12-degree and 45-level grid. Results for analyses are from the last 23 years of a 70-year integration forced with realistic 1979-2001 atmospheric data. Velocity at three depth intervals, mean transports and fluxes are investigated to identify the main current pathways and directions. Variability is determined by comparison of results a decade apart. Mean velocity fields describe a climatological circulation pattern that is cyclonic in nature with increased intensity during the late 1980s and early 1990s. The meander through the Chukchi Borderland Pass is the main pathway for boundary flow across the Chukchi Plateau. The northern Chukchi Plateau is modeled as a region of major volume, heat and freshwater transport into the Canada Basin interior. It also appears to be an area of net upward heat transport, which may be available for melting ice. Northward flow along the eastern side of the Northwind Ridge is identified as a mechanism for advection of freshwater from the Chukchi shelves into the interior. http://archive.org/details/thecirculationnd109456244 Lieutenant, United States Navy Approved for public release; distribution is unlimited.