A distinct change in the ocean circulation of the Gulf of Alaska after the 1976-77 climate shift ... more A distinct change in the ocean circulation of the Gulf of Alaska after the 1976-77 climate shift is studied in an eddy-permitting primitive equation model forced by observed windstresses from 1951-1999. After the Aleutian Low strengthens, mean velocities of the Alaskan Stream increase northeast of Kodiak Island and decrease southwest of it. Mesoscale eddy variance likewise increases to the northeast of Kodiak and weakens to the southwest. Mean and eddy flows in the eastern Gulf remain unchanged after the shift. Since mesoscale eddies provide a mechanism for transporting nutrient-rich open-ocean waters to the productive shelf region, the flow of energy through the food web may have been altered by this physical oceanographic change.
The GLOBEC program was tasked with understanding the mechanistic links between climate forcing an... more The GLOBEC program was tasked with understanding the mechanistic links between climate forcing and the ocean-ecosystem response on the northern Gulf of Alaska (GOA) shelf. To address this task, samples were collected five to six times times annually along the Seward Line between 1998 and 2004. However, interpreting Seward-Line field observations in space and time is complicated by the complex circulation on the GOA shelf. The Alaska Current/Alaskan Stream and Alaska Coastal Current produce eddies and meanders which mix the iron-limited small-cell oceanic community with the iron-rich large-cell coastal community. Thus observations at any point in space and time are the result of the degree of mixing of the oceanic and coastal water masses. The ROMS circulation model with an embedded ecosystem model was used to extend GLOBEC observations in space and time on the GOA shelf. The timing of the spring bloom in simulations was related to shallowing of the pycnocline. The spring bloom began in late March-April on the inner shelf and in May on the mid and outer shelf. The simulations suggest that the magnitude of shelf production is a balance between the amount of iron from freshwater runoff and nitrate, with iron limitation on the outer shelf and adjacent ocean and nitrate limitation on the inner shelf. Simulated shelfbreak eddies form near Yakutat, have elevated iron concentrations relative to surrounding waters, and propagate westward, influencing production and nitrate concentrations on the outer shelf and in the adjacent ocean during spring and summer. Simulated primary production in the Seward Line region was about 100-130 g cm À2 y À1 , but production of up to 300 g cm À2 y À1 is predicted for regions in Lower Cook Inlet and around Kodiak.
A primitive equation, hydrostatic, terrain-following coordinate ocean general circulation model Ž... more A primitive equation, hydrostatic, terrain-following coordinate ocean general circulation model Ž . OGCM is used to investigate the mean water mass pathways from the subtropics to the tropics in the Atlantic Ocean. The OGCM is used in a fully realistic configuration of the Atlantic, from 308S to 658N, with realistic bathymetry. Surface forcings are provided by the COADS climatology. A non-eddy-resolving numerical simulation is analyzed with 3r48 horizontal resolution and 20 terrain-following vertical levels.
... Regional terms: USA; Alaska; Northwestern coastal Gulf; 50-62 deg.N; 142-162 deg.W. ... The N... more ... Regional terms: USA; Alaska; Northwestern coastal Gulf; 50-62 deg.N; 142-162 deg.W. ... The NEP model extends from approximately 20°N to 71°N and uses a coupled ocean/sea ice version of ROMS (Budgell, 2005) for the integration from 1958 through 2004. ...
The GLOBEC program was tasked with understanding the mechanistic links between climate forcing an... more The GLOBEC program was tasked with understanding the mechanistic links between climate forcing and the ocean-ecosystem response on the northern Gulf of Alaska (GOA) shelf. To address this task, samples were collected five to six times times annually along the Seward Line between 1998 and 2004. However, interpreting Seward-Line field observations in space and time is complicated by the complex circulation on the GOA shelf. The Alaska Current/Alaskan Stream and Alaska Coastal Current produce eddies and meanders which mix the iron-limited small-cell oceanic community with the iron-rich large-cell coastal community. Thus observations at any point in space and time are the result of the degree of mixing of the oceanic and coastal water masses. The ROMS circulation model with an embedded ecosystem model was used to extend GLOBEC observations in space and time on the GOA shelf. The timing of the spring bloom in simulations was related to shallowing of the pycnocline. The spring bloom began in late March-April on the inner shelf and in May on the mid and outer shelf. The simulations suggest that the magnitude of shelf production is a balance between the amount of iron from freshwater runoff and nitrate, with iron limitation on the outer shelf and adjacent ocean and nitrate limitation on the inner shelf. Simulated shelfbreak eddies form near Yakutat, have elevated iron concentrations relative to surrounding waters, and propagate westward, influencing production and nitrate concentrations on the outer shelf and in the adjacent ocean during spring and summer. Simulated primary production in the Seward Line region was about 100-130 g cm À2 y À1 , but production of up to 300 g cm À2 y À1 is predicted for regions in Lower Cook Inlet and around Kodiak.
Deep Sea Research Part II: Topical Studies in Oceanography, 2013
Coupled physical/biological models can be used to downscale global climate change to the ecology ... more Coupled physical/biological models can be used to downscale global climate change to the ecology of subarctic regions, and to explore the bottom-up and top-down effects of that change on the spatial structure of subarctic ecosystems-for example, the relative dominance of large vs. small zooplankton in relation to ice cover. Here we utilize a multivariate statistical approach to extract the emergent properties of a coupled physical/biological hindcast of the Bering Sea for years 1970-2009, which includes multiple episodes of warming and cooling (e.g. the recent cooling of 2005-2009), and a multidecadal regional forecast of the coupled models, driven by an IPCC global model forecast of 2010-2040. Specifically, we employ multivariate empirical orthogonal function (EOF) analysis to derive the spatial covariance among physical and biological timeseries from our simulations. These are compared with EOFs derived from spatially gridded measurements of the region, collected during multiyear field programs. The model replicates observed relationships among temperature and salinity, as well as the observed inverse correlation between temperature and large crustacean zooplankton on the southeastern Bering Sea shelf. Predicted future warming of the shelf is accompanied by a northward shift in both pelagic and benthic biomass.
... Regional terms: USA; Alaska; Northwestern coastal Gulf; 50-62 deg.N; 142-162 deg.W. ... The N... more ... Regional terms: USA; Alaska; Northwestern coastal Gulf; 50-62 deg.N; 142-162 deg.W. ... The NEP model extends from approximately 20°N to 71°N and uses a coupled ocean/sea ice version of ROMS (Budgell, 2005) for the integration from 1958 through 2004. ...
A distinct change in the ocean circulation of the Gulf of Alaska after the 1976-77 climate shift ... more A distinct change in the ocean circulation of the Gulf of Alaska after the 1976-77 climate shift is studied in an eddy-permitting primitive equation model forced by observed windstresses from 1951-1999. After the Aleutian Low strengthens, mean velocities of the Alaskan Stream increase northeast of Kodiak Island and decrease southwest of it. Mesoscale eddy variance likewise increases to the northeast of Kodiak and weakens to the southwest. Mean and eddy flows in the eastern Gulf remain unchanged after the shift. Since mesoscale eddies provide a mechanism for transporting nutrient-rich open-ocean waters to the productive shelf region, the flow of energy through the food web may have been altered by this physical oceanographic change.
A distinct change in the ocean circulation of the Gulf of Alaska after the 1976-77 climate shift ... more A distinct change in the ocean circulation of the Gulf of Alaska after the 1976-77 climate shift is studied in an eddy-permitting primitive equation model forced by observed windstresses from 1951-1999. After the Aleutian Low strengthens, mean velocities of the Alaskan Stream increase northeast of Kodiak Island and decrease southwest of it. Mesoscale eddy variance likewise increases to the northeast of Kodiak and weakens to the southwest. Mean and eddy flows in the eastern Gulf remain unchanged after the shift. Since mesoscale eddies provide a mechanism for transporting nutrient-rich open-ocean waters to the productive shelf region, the flow of energy through the food web may have been altered by this physical oceanographic change.
The GLOBEC program was tasked with understanding the mechanistic links between climate forcing an... more The GLOBEC program was tasked with understanding the mechanistic links between climate forcing and the ocean-ecosystem response on the northern Gulf of Alaska (GOA) shelf. To address this task, samples were collected five to six times times annually along the Seward Line between 1998 and 2004. However, interpreting Seward-Line field observations in space and time is complicated by the complex circulation on the GOA shelf. The Alaska Current/Alaskan Stream and Alaska Coastal Current produce eddies and meanders which mix the iron-limited small-cell oceanic community with the iron-rich large-cell coastal community. Thus observations at any point in space and time are the result of the degree of mixing of the oceanic and coastal water masses. The ROMS circulation model with an embedded ecosystem model was used to extend GLOBEC observations in space and time on the GOA shelf. The timing of the spring bloom in simulations was related to shallowing of the pycnocline. The spring bloom began in late March-April on the inner shelf and in May on the mid and outer shelf. The simulations suggest that the magnitude of shelf production is a balance between the amount of iron from freshwater runoff and nitrate, with iron limitation on the outer shelf and adjacent ocean and nitrate limitation on the inner shelf. Simulated shelfbreak eddies form near Yakutat, have elevated iron concentrations relative to surrounding waters, and propagate westward, influencing production and nitrate concentrations on the outer shelf and in the adjacent ocean during spring and summer. Simulated primary production in the Seward Line region was about 100-130 g cm À2 y À1 , but production of up to 300 g cm À2 y À1 is predicted for regions in Lower Cook Inlet and around Kodiak.
A primitive equation, hydrostatic, terrain-following coordinate ocean general circulation model Ž... more A primitive equation, hydrostatic, terrain-following coordinate ocean general circulation model Ž . OGCM is used to investigate the mean water mass pathways from the subtropics to the tropics in the Atlantic Ocean. The OGCM is used in a fully realistic configuration of the Atlantic, from 308S to 658N, with realistic bathymetry. Surface forcings are provided by the COADS climatology. A non-eddy-resolving numerical simulation is analyzed with 3r48 horizontal resolution and 20 terrain-following vertical levels.
... Regional terms: USA; Alaska; Northwestern coastal Gulf; 50-62 deg.N; 142-162 deg.W. ... The N... more ... Regional terms: USA; Alaska; Northwestern coastal Gulf; 50-62 deg.N; 142-162 deg.W. ... The NEP model extends from approximately 20°N to 71°N and uses a coupled ocean/sea ice version of ROMS (Budgell, 2005) for the integration from 1958 through 2004. ...
The GLOBEC program was tasked with understanding the mechanistic links between climate forcing an... more The GLOBEC program was tasked with understanding the mechanistic links between climate forcing and the ocean-ecosystem response on the northern Gulf of Alaska (GOA) shelf. To address this task, samples were collected five to six times times annually along the Seward Line between 1998 and 2004. However, interpreting Seward-Line field observations in space and time is complicated by the complex circulation on the GOA shelf. The Alaska Current/Alaskan Stream and Alaska Coastal Current produce eddies and meanders which mix the iron-limited small-cell oceanic community with the iron-rich large-cell coastal community. Thus observations at any point in space and time are the result of the degree of mixing of the oceanic and coastal water masses. The ROMS circulation model with an embedded ecosystem model was used to extend GLOBEC observations in space and time on the GOA shelf. The timing of the spring bloom in simulations was related to shallowing of the pycnocline. The spring bloom began in late March-April on the inner shelf and in May on the mid and outer shelf. The simulations suggest that the magnitude of shelf production is a balance between the amount of iron from freshwater runoff and nitrate, with iron limitation on the outer shelf and adjacent ocean and nitrate limitation on the inner shelf. Simulated shelfbreak eddies form near Yakutat, have elevated iron concentrations relative to surrounding waters, and propagate westward, influencing production and nitrate concentrations on the outer shelf and in the adjacent ocean during spring and summer. Simulated primary production in the Seward Line region was about 100-130 g cm À2 y À1 , but production of up to 300 g cm À2 y À1 is predicted for regions in Lower Cook Inlet and around Kodiak.
Deep Sea Research Part II: Topical Studies in Oceanography, 2013
Coupled physical/biological models can be used to downscale global climate change to the ecology ... more Coupled physical/biological models can be used to downscale global climate change to the ecology of subarctic regions, and to explore the bottom-up and top-down effects of that change on the spatial structure of subarctic ecosystems-for example, the relative dominance of large vs. small zooplankton in relation to ice cover. Here we utilize a multivariate statistical approach to extract the emergent properties of a coupled physical/biological hindcast of the Bering Sea for years 1970-2009, which includes multiple episodes of warming and cooling (e.g. the recent cooling of 2005-2009), and a multidecadal regional forecast of the coupled models, driven by an IPCC global model forecast of 2010-2040. Specifically, we employ multivariate empirical orthogonal function (EOF) analysis to derive the spatial covariance among physical and biological timeseries from our simulations. These are compared with EOFs derived from spatially gridded measurements of the region, collected during multiyear field programs. The model replicates observed relationships among temperature and salinity, as well as the observed inverse correlation between temperature and large crustacean zooplankton on the southeastern Bering Sea shelf. Predicted future warming of the shelf is accompanied by a northward shift in both pelagic and benthic biomass.
... Regional terms: USA; Alaska; Northwestern coastal Gulf; 50-62 deg.N; 142-162 deg.W. ... The N... more ... Regional terms: USA; Alaska; Northwestern coastal Gulf; 50-62 deg.N; 142-162 deg.W. ... The NEP model extends from approximately 20°N to 71°N and uses a coupled ocean/sea ice version of ROMS (Budgell, 2005) for the integration from 1958 through 2004. ...
A distinct change in the ocean circulation of the Gulf of Alaska after the 1976-77 climate shift ... more A distinct change in the ocean circulation of the Gulf of Alaska after the 1976-77 climate shift is studied in an eddy-permitting primitive equation model forced by observed windstresses from 1951-1999. After the Aleutian Low strengthens, mean velocities of the Alaskan Stream increase northeast of Kodiak Island and decrease southwest of it. Mesoscale eddy variance likewise increases to the northeast of Kodiak and weakens to the southwest. Mean and eddy flows in the eastern Gulf remain unchanged after the shift. Since mesoscale eddies provide a mechanism for transporting nutrient-rich open-ocean waters to the productive shelf region, the flow of energy through the food web may have been altered by this physical oceanographic change.
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