Morey, S. L., & Dukhovskoy, D. S. (2013). A downscaling method for simulating deep current interactions with topography – Application to the Sigsbee Escarpment. Ocean Modelling, 69, 50–63.
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Morrison, T., Dukhovskoy, D. S., McClean, J., Gille, S. T., & Chassignet, E. (2018). Causes of the anomalous heat flux onto the Greenland continental shelf. In American Geophysical Union (Vol. Fall Meeting).
Abstract: On the continental shelf around Greenland, warm-salty Atlantic water at depth fills the deep narrow fjords where Greenland's tidewater glaciers terminate. Changes in the quantity or properties of this water mass starting in the mid 1990s is thought to be largely responsible for increased ocean-driven melting of the Greenland Ice Sheet. Using high-resolution (nominal 0.1-degree) ocean circulation models we cannot accurately resolve small-scale processes on the shelf or within fjords. However, we can assess changes in the flux of heat via Atlantic water onto the continental shelf. To understand the causes of the anomalous heat that has reached the shelf we examine heat content of subtropical gyre water and shifts in the North Atlantic and Atlantic Multidecadal Oscillations.
We compare changes in heat transport in two eddy permitting simulations: a global 0.1 degree (5-7km around Greenland) resolution coupled hindcast (1970-2009) simulation of the Parallel Ocean Program (POP) and a regional 0.08 degree (3-5km around Greenland) resolution coupled HYbrid Coordinate Ocean Model (HYCOM) hindcast (1993-2016) simulation. Both models are coupled to the Los Alamos National Laboratory Community Ice CodE version 4 and forced by atmospheric reanalysis fluxes. In both models we look for processes that could explain the increase in heat; processes that are present in both are likely to be robust causes of warming.
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Nof, D., Jia, Y., Chassignet, E., & Bozec, A. (2011). Fast Wind-Induced Migration of Leddies in the South China Sea. J. Phys. Oceanogr., 41(9), 1683–1693.
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Perrie, W., Zhang, W., Bourassa, M., Shen, H., & Vachon, P. W. (2008). Impact of Satellite Winds on Marine Wind Simulations. Wea. Forecasting, 23(2), 290–303.
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Podestá, G., Letson, D., Messina, C., Royce, F., Ferreyra, R. A., Jones, J., et al. (2002). Use of ENSO-related climate information in agricultural decision making in Argentina: a pilot experience. Agricultural Systems, 74(3), 371–392.
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Proshutinsky, A., Krishfield, R., Toole, J. M., Timmermans, M. - L., Williams, W., Zimmermann, S., et al. (2019). Analysis of the Beaufort Gyre Freshwater Content in 2003-2018. J Geophys Res Oceans, 124(12).
Abstract: Hydrographic data collected from research cruises, bottom-anchored moorings, drifting Ice-Tethered Profilers, and satellite altimetry in the Beaufort Gyre region of the Arctic Ocean document an increase of more than 6,400 km(3) of liquid freshwater content from 2003 to 2018: a 40% growth relative to the climatology of the 1970s. This fresh water accumulation is shown to result from persistent anticyclonic atmospheric wind forcing (1997-2018) accompanied by sea ice melt, a wind-forced redirection of Mackenzie River discharge from predominantly eastward to westward flow, and a contribution of low salinity waters of Pacific Ocean origin via Bering Strait. Despite significant uncertainties in the different observations, this study has demonstrated the synergistic value of having multiple diverse datasets to obtain a more comprehensive understanding of Beaufort Gyre freshwater content variability. For example, Beaufort Gyre Observational System (BGOS) surveys clearly show the interannual increase in freshwater content, but without satellite or Ice-Tethered Profiler measurements, it is not possible to resolve the seasonal cycle of freshwater content, which in fact is larger than the year-to-year variability, or the more subtle interannual variations.
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Proshutinsky, A., Krishfield, R., Toole, J. M., Timmermans, M. - L., Williams, W., Zimmermann, S., et al. (2019). Analysis of the Beaufort Gyre Freshwater Content in 2003-2018. J Geophys Res Oceans, 124(12), 9658–9689.
Abstract: Hydrographic data collected from research cruises, bottom-anchored moorings, drifting Ice-Tethered Profilers, and satellite altimetry in the Beaufort Gyre region of the Arctic Ocean document an increase of more than 6,400 km(3) of liquid freshwater content from 2003 to 2018: a 40% growth relative to the climatology of the 1970s. This fresh water accumulation is shown to result from persistent anticyclonic atmospheric wind forcing (1997-2018) accompanied by sea ice melt, a wind-forced redirection of Mackenzie River discharge from predominantly eastward to westward flow, and a contribution of low salinity waters of Pacific Ocean origin via Bering Strait. Despite significant uncertainties in the different observations, this study has demonstrated the synergistic value of having multiple diverse datasets to obtain a more comprehensive understanding of Beaufort Gyre freshwater content variability. For example, Beaufort Gyre Observational System (BGOS) surveys clearly show the interannual increase in freshwater content, but without satellite or Ice-Tethered Profiler measurements, it is not possible to resolve the seasonal cycle of freshwater content, which in fact is larger than the year-to-year variability, or the more subtle interannual variations.
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Roads, J. (2003). International Research Institute/Applied Research Centers (IRI/ARCs) regional model intercomparison over South America. J. Geophys. Res., 108(D14).
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Samuelsen, A. (2005). Modeling the Effect of Eddies and Advection on the Lower Trophic Ecosystem in the Northeast Tropical Pacific. Ph.D. thesis, Florida State University, Tallahassee, FL.
Abstract: A medium complexity, nitrogen-based ecosystem model is developed in order to simulate the ecosystem in the northeast tropical Pacific. Several physical processes have major impact on the ecosystem in this region, most importantly intense wind jets along the coast and upwelling at the Costa Rica Dome (CRD). The ecosystem model is run “offline”, using a realistic physical ocean model hindcast as input. The physical model is a subdomain of the global Navy Coastal Ocean Model, which is a hybrid sigma-z level model. The model assimilates Modular Ocean Data Assimilation System temperature and salinity profiles derived from altimetry and sea surface temperature data. The model is forced by daily heat and momentum fluxes, and therefore captures short-term wind events such as the Tehuantepec jet. Because the model has high horizontal resolution (~1/8 degree) and assimilates sea surface height data, it has a realistic representation of eddies and mesoscale variability. The ecosystem model includes two nutrients (nitrate and ammonium), two size-classes of phytoplankton, two size-classes of zooplankton, and detritus. The model is run for 4 years from 1999 to 2002, with analyses focused on 2000-2002. The model is validated using SeaWiFS data and ship-based observations from the STAR-cruises (Stenella Abundance Research Project) of 1999 and 2000. The northernmost and most intense of the wind jets along Central America is the Tehuantepec jet. The Tehuantepec jet is responsible for upwelling large amounts of nutrient rich water south of the Gulf of Tehuantepec. The jet also occasionally produce large anti-cyclonic eddies that transport organic matter away from the coast. Because organic matter that is transported into the open ocean will eventually sink to the deep ocean, this has implications for the carbon export in this region. The model results are used to calculate cross-shelf fluxes in this region in order to estimate how much organic material is transported across the shelf break. Results show that at the Gulf of Tehuantepec there is high offshore export of organic material, particularly during eddy generation events, but also in fall. The highest export is on the order of 10 Mg C per meter of coastline per day and happens during eddy events. During these events there is a comparable onshore flux to the south of the gulf. Typically there is onshore flux to the south of the gulf during the summer. The model estimated transport away from the coast at the Gulf of Tehuantepec is 167 Tg C/year, and the onshore transport to the south of the gulf is 704 Tg C/year. The second subject of interest is the CRD. In this region, upwelling at the surface is caused by Ekman upwelling during the summer, although the dome is thought to be present at depth throughout the year. The doming of the isotherms below the thermocline is a result of vortex stretching and is decoupled from the wind-driven processes at the surface. A mass-balance budget is calculated at the CRD, and the horizontal and vertical fluxes are related to the abundance of plankton at the dome. There is upwelling (7.2X10-2 Sv ) at the dome throughout the year, but around the location of the dome (90° W), the upwelling is largest in the winter. Further west, input of nutrients from below is larger in the fall and summer. The results suggest that about 80% of the nitrate that is supplied to the dome during summer is actually brought up to the west of the dome and transported eastward by the North Equatorial Counter Current.
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Schoof, J. T., Arguez, A., Brolley, J., & O'Brien, J. J. (2005). A new weather generator based on spectral properties of surface air temperatures. Agricultural and Forest Meteorology, 135(1-4), 241–251.
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