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Edward D. Zaron and David A. Jay

level records (stations west of the date line). Table 2. Hourly Sea level records (stations east of the date line). The stations are located throughout the North and South Pacific; although, a disproportionate number are located on the Hawaiian Islands, and there are only three stations to the east of 210°E ( Fig. 1 ). The stations were selected from the UHSLC holdings based on the length of the time series at each site and on their location away from continental shelves and coasts. All of the

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Laurie Yung, Nicky Phear, Alayna DuPont, Jess Montag, and Daniel Murphy

Abstract

Agricultural producers may be particularly vulnerable to climate impacts, such as drought. To better understand how ranchers respond to ongoing drought and the relationship between climate change beliefs and drought adaptation, in-depth interviews with working ranchers were conducted. Ranchers described drought conditions as unprecedented and detailed the interacting impacts of drought and nonclimatic stressors. They viewed adaptation as critical and employed a wide range of responses to drought, but lack of financial resources, risks associated with change, local social norms, and optimism about future moisture created barriers to change. Most ranchers attributed drought to natural cycles and were skeptical about anthropogenic climate change. Many ranchers likened current drought conditions to past droughts, concluding that conditions would return to “normal.” A belief in natural cycles provided a sense of hope for some ranchers but felt immutable to others, reducing their sense of agency and efficacy. Taken together, climate skepticism, optimism about future conditions, lack of financial resources, and a limited sense of agency might be reducing investments in long-term adaptation. However, the relationship between climate change beliefs and adaptation action was not entirely clear, since the handful of ranchers adapting in anticipation of long-term drought were skeptical or uncertain about anthropogenic climate change. Further, most ranchers characterized adaptation as an individual endeavor and resisted government involvement in drought adaptation. In the context of climate skepticism and antigovernment sentiment, strategies to scale up adaptation efforts beyond the household will only succeed to the extent that they build on local norms and ideologies.

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Ruth E. Petrie, Len C. Shaffrey, and Rowan T. Sutton

Abstract

The atmospheric response to an idealized decline in Arctic sea ice is investigated in a novel fully coupled climate model experiment. In this experiment two ensembles of single-year model integrations are performed starting on 1 April, the approximate start of the ice melt season. By perturbing the initial conditions of sea ice thickness (SIT), declines in both sea ice concentration and SIT, which result in sea ice distributions that are similar to the recent sea ice minima of 2007 and 2012, are induced. In the ice loss regions there are strong (~3 K) local increases in sea surface temperature (SST); additionally, there are remote increases in SST in the central North Pacific and subpolar gyre in the North Atlantic. Over the central Arctic there are increases in surface air temperature (SAT) of ~8 K due to increases in ocean–atmosphere heat fluxes. There are increases in SAT over continental North America that are in good agreement with recent changes as seen by reanalysis data. It is estimated that up to two-thirds of the observed increase in SAT in this region could be related to Arctic sea ice loss. In early summer there is a significant but weak atmospheric circulation response that projects onto the summer North Atlantic Oscillation (NAO). In early summer and early autumn there is an equatorward shift of the eddy-driven jet over the North Atlantic as a result of a reduction in the meridional temperature gradients. In winter there is no projection onto a particular phase of the NAO.

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K. H. Brink and H. Seo

1. Introduction For a range of continental shelf locations, Kundu and Allen (1976) , along with several subsequent investigators (e.g., Winant 1983 ; Dever 1997 ; S. Lentz 2015, personal communication), have demonstrated a striking discrepancy between large correlation length scales for middepth subtidal alongshore velocity versus shorter scales for cross-shelf velocity. This order of magnitude discrepancy is far greater than can be accounted for by the natural scale differences for

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Jason D. Flanagan, Timour Radko, William J. Shaw, and Timothy P. Stanton

Abstract

This study examines the interaction of diffusive convection and shear through a series of 2D and 3D direct numerical simulations (DNS). The model employed is based on the Boussinesq equations of motion with oscillating shear represented by a forcing term in the momentum equation. This study calculates thermal diffusivities for a wide range of Froude numbers and density ratios and compares the results with those from the analysis of observational data gathered during a 2005 expedition to the eastern Weddell Sea. The patterns of layering and the strong dependence of thermal diffusivity on the density ratio described here are in agreement with observations. Additionally, the authors evaluate salinity fluxes that are inaccessible from field data and formulate a parameterization of buoyancy transport. The relative significance of double diffusion and shear is quantified through comparison of density fluxes, efficiency factor, and dissipation ratio for the regimes with/without diffusive convection. This study assesses the accuracy of the thermal production dissipation and turbulent kinetic energy balances, commonly used in microstructure-based observational studies, and quantifies the length of the averaging period required for reliable statistics and the spatial variability of heat flux.

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Peter E. D. Davis, Camille Lique, Helen L. Johnson, and John D. Guthrie

Abstract

The Arctic Ocean is undergoing a period of rapid transition. Freshwater input is projected to increase, and the decline in Arctic sea ice is likely to drive periodic increases in vertical mixing during ice-free periods. Here, a 1D model of the Arctic Ocean is used to explore how these competing processes will affect the stratification, the stability of the cold halocline, and the sea ice cover at the surface. Initially, stronger shear leads to elevated vertical mixing that causes the mixed layer to warm. The change in temperature, however, is too small to affect the sea ice cover. Most importantly, in the Eurasian Basin, the elevated shear also deepens the halocline and strengthens the stratification over the Atlantic Water thermocline, reducing the vertical heat flux. After about a decade this effect dominates, and the mixed layer begins to cool. The sea ice cover can only be significantly affected if the elevated mixing is sufficient to erode the stratification barrier associated with the cold halocline. While freshwater generally dominates in the Canadian Basin (further isolating the mixed layer from the Atlantic Water layer), in the Eurasian Basin elevated shear reduces the strength of the stratification barrier, potentially allowing Atlantic Water heat to be directly entrained into the mixed layer during episodic mixing events. Therefore, although most sea ice retreat to date has occurred in the Canadian Basin, the results here suggest that, in future decades, elevated vertical mixing may play a more significant role in sea ice melt in the Eurasian Basin.

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Andre Staalstrøm, Lars Arneborg, Bengt Liljebladh, and Göran Broström

1. Introduction Flow–topography interactions caused by stratified flow over, around, and through rough topography are important for mixing in the deep abyssal ocean (e.g., Ledwell et al. 2000 ), over the shelf (e.g., Nash and Moum 2001 ), and in fjords (e.g., Arneborg and Liljebladh 2009 ). Fjord entrances with sills are typical locations of strong flow–topography interactions due to strong barotropic and baroclinic currents caused by tides and exchange processes between the fjord and the

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K. H. Brink

), alongshore correlation scales for alongshore currents would be somewhat larger than for cross-shelf currents, but the discrepancy would be nowhere near as dramatic as that found by Kundu and Allen. Comparably complete measurements from other continental shelf locations have produced similar results for length scales, for example, for Peru near 15°S ( Brink et al. 1980 , their appendixes), off northern California ( Dever 1997 ), off southern California ( Winant 1983 ), and in the Middle Atlantic Bight (S

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H. Kontoyiannis, V. Lykousis, V. Papadopoulos, S. Stavrakakis, E. G. Anassontzis, A. Belias, S. Koutsoukos, and L. K. Resvanis

( Fig. 12 ). This grid is subsampled along the x and y axes at the locations of the current meters to get the estimates of the first and second horizontal derivatives by employing spline fits on the subsampled data. The results on the computation of the horizontal eddy diffusivities along with their errors are in Tables 2 and 3 . The details of the error analysis, along with tests of sensitivity to the temperature/salinity input values in the objective analysis procedure, are in the

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Mary-Louise Timmermans and Steven R. Jayne

each of the Arctic profiles (blue) and each of the Pacific profiles (red). (f) Close-up of the Arctic profiles in Θ– S A space. (g) Map showing locations of Arctic Ocean (AO) and Pacific Ocean (PO) profiles. 3. Water column structure: A Pacific–Arctic comparison Water column profiles from the Arctic Ocean’s central Canada Basin and from the western Pacific Ocean exemplify the stark differences in the structure of oceans that are predominantly stratified by salinity and warmer oceans that are

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