Robin Robertson - Profile on Academia.edu (original) (raw)
Papers by Robin Robertson
Dynamical Analysis of the Enhanced Turbulent Mixing Over a Rough Ocean Bottom
AGUOS, Feb 1, 2016
Mixing in the Philippine Sea: Geography variability and parameterization
Deep-sea Research Part Ii-topical Studies in Oceanography, Aug 1, 2022
Sound propagation in Australian waters is of keen interest to the Royal Australian Navy (RAN) and... more Sound propagation in Australian waters is of keen interest to the Royal Australian Navy (RAN) and the Maritime Division of the Royal Australian Air Force (RAAF) as it affects sonar performance in one of their prime operating regions. Off eastern Australia, temperature fields are affected by the East Australian Current (EAC), eddies generated by the EAC, and internal tides. The ocean’s temperature structure off eastern Australia can be divided into three basic regimes: the strong southward EAC region (24 o -28 o S), the EAC separation region (28 o -32 o S), and the ‘river’ of eddies region (32 o -38 o S) south of the separation zone. Although the internal tides in this region are small, they modify the sound speed profile, with the potential to affect acoustic propagation on time scales of the daily and twice daily tidal cycles and the 15-day spring-neap tidal cycle. A primitive-equation model (Regional Ocean Modelling System (ROMS)) with tidal forcing provided temperature and salini...
Scientific data, Jan 30, 2016
Since 2008, 26 glider missions have been undertaken along the continental shelf of southeastern A... more Since 2008, 26 glider missions have been undertaken along the continental shelf of southeastern Australia. Typically these missions have spanned the continental shelf on the inshore edge of the East Australian Current from 29.5-33.5°S. This comprehensive dataset of over 33,600 CTD profiles from the surface to within 10 m of the bottom in water depths ranging 25-200 m provides new and unprecedented high resolution observations of the properties of the continental shelf waters adjacent to a western boundary current, straddling the region where it separates from the coast. The region is both physically and biologically significant, and is also in a hotspot of ocean warming. We present gridded mean fields for temperature, salinity and density, but also dissolved oxygen and chlorophyll-a fluorescence indicative of phytoplankton biomass. This data will be invaluable for understanding shelf stratification, circulation, biophysical and bio-geochemical interactions, as well as for the valida...
Journal of Geophysical Research: Oceans, 2018
High‐resolution measurements of the air‐ice‐ocean system during an October 2015 event in the Beau... more High‐resolution measurements of the air‐ice‐ocean system during an October 2015 event in the Beaufort Sea demonstrate how stored ocean heat can be released to temporarily reverse seasonal ice advance. Strong on‐ice winds over a vast fetch caused mixing and release of heat from the upper ocean. This heat was sufficient to melt large areas of thin, newly formed pancake ice; an average of 10 MJ/m2 was lost from the upper ocean in the study area, resulting in ∼3–5 cm pancake sea ice melt. Heat and salt budgets create a consistent picture of the evolving air‐ice‐ocean system during this event, in both a fixed and ice‐following (Lagrangian) reference frame. The heat lost from the upper ocean is large compared with prior observations of ocean heat flux under thick, multiyear Arctic sea ice. In contrast to prior studies, where almost all heat lost goes into ice melt, a significant portion of the ocean heat released in this event goes directly to the atmosphere, while the remainder (∼30–40%)...
Elementa: Science of the Anthropocene, 2015
We present the first densely-sampled hydrographic survey of the Amundsen Sea Polynya (ASP) region... more We present the first densely-sampled hydrographic survey of the Amundsen Sea Polynya (ASP) region, including a detailed characterization of its freshwater distributions. Multiple components contribute to the freshwater budget, including precipitation, sea ice melt, basal ice shelf melt, and iceberg melt, from local and non-local sources. We used stable oxygen isotope ratios in seawater (δ18O) to distinguish quantitatively the contributions from sea ice and meteoric-derived sources. Meteoric fractions were high throughout the winter mixed layer (WML), with maximum values of 2–3% (±0.5%). Because the ASP region is characterized by deep WMLs, column inventories of total meteoric water were also high, ranging from 10–13 m (±2 m) adjacent to the Dotson Ice Shelf (DIS) and in the deep trough to 7–9 m (±2 m) in shallower areas. These inventories are at least twice those reported for continental shelf waters near the western Antarctic Peninsula. Sea ice melt fractions were mostly negative, ...
Remote Sensing
Breaking internal tides and induced mixing are critical to shelf dynamics, including heat and mas... more Breaking internal tides and induced mixing are critical to shelf dynamics, including heat and mass exchanges. Spatiotemporal variability of internal tides and modulation factors for the southern East China Sea shelf were examined based on a combination of a three-month mooring velocity and satellite altimeter data. Semidiurnal and diurnal internal tides exhibited distinct temporal trends, with the semidiurnal internal tides enhanced by an order of magnitude during the latter half of the record, while the diurnal internal tides followed quasi spring-neap cycles with a generally stable intensity except for two specific periods of strengthening. These internal tides probably originated remotely over the shelf-slope area northeast of Taiwan. Time-varying stratification was the most important factor for the internal tidal magnitude. In addition, varying background currents influenced the diurnal critical latitude band, which explains the slightly enhanced diurnal internal tides during th...
Turbulent mixing in the ocean interior is mainly attributed to internal wave breaking; however, t... more Turbulent mixing in the ocean interior is mainly attributed to internal wave breaking; however, the mixing properties and the modulation effects of mesoscale environmental factors are not well known. Here, the spatially inhomogeneous and seasonally variable diapycnal diffusivities in the upper Philippine Sea were estimated from Argo float data using a strain-based, fine-scale parameterization. Based on a coordinated analysis of multi-source data, we found that the driving processes for diapycnal diffusivities mainly included the near-inertial waves and internal tides. Mesoscale features were important in intensifying the mixing and modulating of its spatial pattern. An interesting finding was that, besides near-inertial waves, internal tides also contributed significant diapycnal mixing in the upper Philippine Sea. The seasonal cycles of diapycnal diffusivities and their contributors differed zonally. In the midlatitudes, wind mixing dominated and was strongest in winter and weakest in summer. In contrast, tidal mixing was more predominant in the lower latitudes and had no apparent seasonal variability. Furthermore, we provide evidence that the mesoscale environment in the Philippine Sea played a significant role in regulating the intensity and shaping the spatial inhomogeneity of the internal tidal mixing. The magnitudes of internal tidal mixing were greatly elevated in regions of energetic mesoscale processes. Anticyclonic mesoscale features were found to enhance diapycnal mixing more significantly than cyclonic ones.
Surface Mixing and Its Implementation in Regional Ocean Models
Japan Geoscience Union, 2016
The water column structure of the ice shelf cavity outflow from under Pine Island Glacier and its... more The water column structure of the ice shelf cavity outflow from under Pine Island Glacier and its temporal variability were investigated using a hourly time series of yo-yo CTD and LADCP data collected over ~24 h at the southern end of the ice shelf front. The primary water types present over the continental shelf off Pine Island Bay were Circumpolar Deep Water (CDW), modified Circumpolar Deep Water (mCDW), Shelf Water (SW), and Ice Shelf Water (ISW). As CDW transited the shelf, it transitioned into cooler, mCDW. In the upper 200 m, ISW dominated within 100 km of the ice shelf and SW further offshore. Within Pine Island Bay, the water column was partitioned into two primary layers based on their behavior: an upper outflowing layer from 100 m to 450 m composed of ISW with a significant meltwater component, 1%–2%, over an inflowing layer from ~550 m to the sea bed composed of mCDW. Due to the small cavity extent, the outflowing water was warmer than the seawater freezing point. The up...
Geoscience Letters, 2019
Vertical mixing is important in the ocean for maintaining its stratification, redistributing temp... more Vertical mixing is important in the ocean for maintaining its stratification, redistributing temperature and salinity, distributing nutrients and pollutants, and the energy cascade. It plays a key role in ocean energy transport, climate change, and marine ecosystems. Getting the mixing right in ocean circulation and climate models is critical in reproducing ocean and climate physics. Ocean models, like the Regional Ocean Modeling System (Rutgers ROMS 3.4), provide several options for determining vertical mixing through the vertical mixing parameterization schemes. To evaluate which of these methods best reproduces realistic vertical mixing by internal tides, simulations of baroclinic tides generated by a seamount were performed using seven different vertical mixing parameterizations: Mellor-Yamada 2.5 (MY), Large-McWilliams-Doney’s Kpp (LMD), Nakanishi-Niino’s modification of Mellor-Yamada (NN), and four versions of Generic Length Scale (GLS). The GLS versions in ROMS 3.4 severely o...
Geoscience Letters, 2017
Mixing at the ocean surface is key for atmosphere-ocean interactions and the distribution of heat... more Mixing at the ocean surface is key for atmosphere-ocean interactions and the distribution of heat, energy, and gases in the upper ocean. Winds are the primary force for surface mixing. To properly simulate upper ocean dynamics and the flux of these quantities within the upper ocean, models must reproduce mixing in the upper ocean. To evaluate the performance of the Regional Ocean Modeling System (ROMS) in replicating the surface mixing, the results of four different vertical mixing parameterizations were compared against observations, using the surface mixed layer depth, the temperature fields, and observed diffusivities for comparisons. The vertical mixing parameterizations investigated were Mellor-Yamada 2.5 level turbulent closure (MY), Large-McWilliams-Doney Kpp (LMD), Nakanishi-Niino (NN), and the generic length scale (GLS) schemes. This was done for one temperate site in deep water in the Eastern Pacific and three shallow water sites in the Baltic Sea. The model reproduced the surface mixed layer depth reasonably well for all sites; however, the temperature fields were reproduced well for the deep site, but not for the shallow Baltic Sea sites. In the Baltic Sea, the models overmixed the water column after a few days. Vertical temperature diffusivities were higher than those observed and did not show the temporal fluctuations present in the observations. The best performance was by NN and MY; however, MY became unstable in two of the shallow simulations with high winds. The performance of GLS nearly as good as NN and MY. LMD had the poorest performance as it generated temperature diffusivities that were too high and induced too much mixing. Further observational comparisons are needed to evaluate the effects of different stratification and wind conditions and the limitations on the vertical mixing parameterizations.
Frontiers in Marine Science, 2019
Newman et al. The Southern Ocean Observing System time series of key variables, and delivers the ... more Newman et al. The Southern Ocean Observing System time series of key variables, and delivers the greatest impact from data to all key end-users. Although the Southern Ocean remains one of the least-observed ocean regions, enhanced international coordination and advances in autonomous platforms have resulted in progress toward sustained observations of this region. Since 2009, the Southern Ocean community has deployed over 5700 observational platforms south of 40 • S. Large-scale, multi-year or sustained, multidisciplinary efforts have been supported and are now delivering observations of essential variables at space and time scales that enable assessment of changes being observed in Southern Ocean systems. The improved observational coverage, however, is predominantly for the open ocean, encompasses the summer, consists of primarily physical oceanographic variables, and covers surface to 2000 m. Significant gaps remain in observations of the ice-impacted ocean, the sea ice, depths >2000 m, the air-ocean-ice interface, biogeochemical and biological variables, and for seasons other than summer. Addressing these data gaps in a sustained way requires parallel advances in coordination networks, cyberinfrastructure and data management tools, observational platform and sensor technology, twoway platform interrogation and data-transmission technologies, modeling frameworks, intercalibration experiments, and development of internationally agreed sampling standards and requirements of key variables. This paper presents a community statement on the major scientific and observational progress of the last decade, and importantly, an assessment of key priorities for the coming decade, toward achieving the SOOS vision and delivering essential data to all end-users.
Journal of Geophysical Research: Oceans, 2019
Critical latitudes are a significant area of tidal dissipation. Generally, critical latitudes are... more Critical latitudes are a significant area of tidal dissipation. Generally, critical latitudes are taken to be the exact latitude where the tidal frequency equals the inertial frequency. However, the key is really where the tidal frequency equals the combination of planetary vorticity and relative vorticity from background currents. Although the influence of background currents on critical latitude effects and nonlinear interactions have been noted for many years, their exact impacts are not well known. The latitude dependence of critical latitude impacts on the tides, internal tides, and internal waves in the presence of background currents was investigated using the Regional Ocean Modeling System by shifting a small domain including a seamount from 20.6°to 38.6°S and comparing simulations with and without background currents. The diurnal kinetic energy with mesoscale currents was relatively unchanged for most latitudes, except for a slight decrease 1-4°poleward of the critical latitude. However, the semidiurnal and high-frequency (≥3 cycles per day) kinetic energy increased with the presence of mesoscale currents, especially within the diurnal critical latitude range. Spectral and nonlinear analyses indicated mesoscale currents broadened the range of critical latitude effects and enhanced energy transferring from diurnal frequencies to semidiurnal and high frequencies and from low to high mode waves. Local diffusivities increased, roughly an order of magnitude, when mesoscale currents were present. The impacts of mesoscale currents on the broadening of the critical latitude range and enhancement of nonlinear interactions were attributed to the additional relative vorticity and near-inertial internal waves generated by mesoscale currents.
The Density-Driven Winter Intensification of the Ross Sea Circulation
Journal of Geophysical Research: Oceans, 2018
Characterize the internal tides in the Indonesian Seas and determine how they may vary seasonally... more Characterize the internal tides in the Indonesian Seas and determine how they may vary seasonally and interannually as the thermocline structure changes. OBJECTIVES Our primary objective is to provide reliable estimates for the barotropic and baroclinic tides in the Indonesian Seas. We intend to determine: 1) specifically where in the Indonesian Seas baroclinic tides are generated and propagated, and, if time allows, 2) the effect of the seasonally and ENSO driven North Pacific versus South Pacific thermohaline structures on internal tide generation.
Tides, the PIG, and
Iop Conference Series Earth and Environmental Science, 2010
The present rapid melting of the Pine Island Glacier (PIG) has been attributed to basal melting d... more The present rapid melting of the Pine Island Glacier (PIG) has been attributed to basal melting driven by the ocean. Specifically, this ocean melting is attributed to currents and tides pumping "warm" Circumpolar Deep Water (CDW) into the ice shelf cavity. To identify tidal activity in the region, an observational time series of yo-yo CTD (Conductivity, Temperature, and Depth) data
IOP Conference Series: Earth and Environmental Science, 2010
Recently, there has been a great interest in the tidal contribution to vertical mixing in the oce... more Recently, there has been a great interest in the tidal contribution to vertical mixing in the ocean. In models, vertical mixing is estimated using parameterization of the sub-grid scale processes. Estimates of the vertical mixing varied widely depending on which vertical mixing parameterization was used. This study investigated the performance of ten different vertical mixing parameterizations in a terrain-following ocean model when simulating internal tides. The vertical mixing parameterization was found to have minor effects on the velocity fields at the tidal frequencies, but large effects on the estimates of vertical diffusivity of temperature. Although there was no definitive best performer for the vertical mixing parameterization, several parameterizations were eliminated based on comparison of the vertical diffusivity estimates with observations. The best performers were the new generic coefficients for the generic length scale schemes and Mellor-Yamada's 2.5 level closure scheme.
Dynamical Analysis of the Enhanced Turbulent Mixing Over a Rough Ocean Bottom
AGUOS, Feb 1, 2016
Mixing in the Philippine Sea: Geography variability and parameterization
Deep-sea Research Part Ii-topical Studies in Oceanography, Aug 1, 2022
Sound propagation in Australian waters is of keen interest to the Royal Australian Navy (RAN) and... more Sound propagation in Australian waters is of keen interest to the Royal Australian Navy (RAN) and the Maritime Division of the Royal Australian Air Force (RAAF) as it affects sonar performance in one of their prime operating regions. Off eastern Australia, temperature fields are affected by the East Australian Current (EAC), eddies generated by the EAC, and internal tides. The ocean’s temperature structure off eastern Australia can be divided into three basic regimes: the strong southward EAC region (24 o -28 o S), the EAC separation region (28 o -32 o S), and the ‘river’ of eddies region (32 o -38 o S) south of the separation zone. Although the internal tides in this region are small, they modify the sound speed profile, with the potential to affect acoustic propagation on time scales of the daily and twice daily tidal cycles and the 15-day spring-neap tidal cycle. A primitive-equation model (Regional Ocean Modelling System (ROMS)) with tidal forcing provided temperature and salini...
Scientific data, Jan 30, 2016
Since 2008, 26 glider missions have been undertaken along the continental shelf of southeastern A... more Since 2008, 26 glider missions have been undertaken along the continental shelf of southeastern Australia. Typically these missions have spanned the continental shelf on the inshore edge of the East Australian Current from 29.5-33.5°S. This comprehensive dataset of over 33,600 CTD profiles from the surface to within 10 m of the bottom in water depths ranging 25-200 m provides new and unprecedented high resolution observations of the properties of the continental shelf waters adjacent to a western boundary current, straddling the region where it separates from the coast. The region is both physically and biologically significant, and is also in a hotspot of ocean warming. We present gridded mean fields for temperature, salinity and density, but also dissolved oxygen and chlorophyll-a fluorescence indicative of phytoplankton biomass. This data will be invaluable for understanding shelf stratification, circulation, biophysical and bio-geochemical interactions, as well as for the valida...
Journal of Geophysical Research: Oceans, 2018
High‐resolution measurements of the air‐ice‐ocean system during an October 2015 event in the Beau... more High‐resolution measurements of the air‐ice‐ocean system during an October 2015 event in the Beaufort Sea demonstrate how stored ocean heat can be released to temporarily reverse seasonal ice advance. Strong on‐ice winds over a vast fetch caused mixing and release of heat from the upper ocean. This heat was sufficient to melt large areas of thin, newly formed pancake ice; an average of 10 MJ/m2 was lost from the upper ocean in the study area, resulting in ∼3–5 cm pancake sea ice melt. Heat and salt budgets create a consistent picture of the evolving air‐ice‐ocean system during this event, in both a fixed and ice‐following (Lagrangian) reference frame. The heat lost from the upper ocean is large compared with prior observations of ocean heat flux under thick, multiyear Arctic sea ice. In contrast to prior studies, where almost all heat lost goes into ice melt, a significant portion of the ocean heat released in this event goes directly to the atmosphere, while the remainder (∼30–40%)...
Elementa: Science of the Anthropocene, 2015
We present the first densely-sampled hydrographic survey of the Amundsen Sea Polynya (ASP) region... more We present the first densely-sampled hydrographic survey of the Amundsen Sea Polynya (ASP) region, including a detailed characterization of its freshwater distributions. Multiple components contribute to the freshwater budget, including precipitation, sea ice melt, basal ice shelf melt, and iceberg melt, from local and non-local sources. We used stable oxygen isotope ratios in seawater (δ18O) to distinguish quantitatively the contributions from sea ice and meteoric-derived sources. Meteoric fractions were high throughout the winter mixed layer (WML), with maximum values of 2–3% (±0.5%). Because the ASP region is characterized by deep WMLs, column inventories of total meteoric water were also high, ranging from 10–13 m (±2 m) adjacent to the Dotson Ice Shelf (DIS) and in the deep trough to 7–9 m (±2 m) in shallower areas. These inventories are at least twice those reported for continental shelf waters near the western Antarctic Peninsula. Sea ice melt fractions were mostly negative, ...
Remote Sensing
Breaking internal tides and induced mixing are critical to shelf dynamics, including heat and mas... more Breaking internal tides and induced mixing are critical to shelf dynamics, including heat and mass exchanges. Spatiotemporal variability of internal tides and modulation factors for the southern East China Sea shelf were examined based on a combination of a three-month mooring velocity and satellite altimeter data. Semidiurnal and diurnal internal tides exhibited distinct temporal trends, with the semidiurnal internal tides enhanced by an order of magnitude during the latter half of the record, while the diurnal internal tides followed quasi spring-neap cycles with a generally stable intensity except for two specific periods of strengthening. These internal tides probably originated remotely over the shelf-slope area northeast of Taiwan. Time-varying stratification was the most important factor for the internal tidal magnitude. In addition, varying background currents influenced the diurnal critical latitude band, which explains the slightly enhanced diurnal internal tides during th...
Turbulent mixing in the ocean interior is mainly attributed to internal wave breaking; however, t... more Turbulent mixing in the ocean interior is mainly attributed to internal wave breaking; however, the mixing properties and the modulation effects of mesoscale environmental factors are not well known. Here, the spatially inhomogeneous and seasonally variable diapycnal diffusivities in the upper Philippine Sea were estimated from Argo float data using a strain-based, fine-scale parameterization. Based on a coordinated analysis of multi-source data, we found that the driving processes for diapycnal diffusivities mainly included the near-inertial waves and internal tides. Mesoscale features were important in intensifying the mixing and modulating of its spatial pattern. An interesting finding was that, besides near-inertial waves, internal tides also contributed significant diapycnal mixing in the upper Philippine Sea. The seasonal cycles of diapycnal diffusivities and their contributors differed zonally. In the midlatitudes, wind mixing dominated and was strongest in winter and weakest in summer. In contrast, tidal mixing was more predominant in the lower latitudes and had no apparent seasonal variability. Furthermore, we provide evidence that the mesoscale environment in the Philippine Sea played a significant role in regulating the intensity and shaping the spatial inhomogeneity of the internal tidal mixing. The magnitudes of internal tidal mixing were greatly elevated in regions of energetic mesoscale processes. Anticyclonic mesoscale features were found to enhance diapycnal mixing more significantly than cyclonic ones.
Surface Mixing and Its Implementation in Regional Ocean Models
Japan Geoscience Union, 2016
The water column structure of the ice shelf cavity outflow from under Pine Island Glacier and its... more The water column structure of the ice shelf cavity outflow from under Pine Island Glacier and its temporal variability were investigated using a hourly time series of yo-yo CTD and LADCP data collected over ~24 h at the southern end of the ice shelf front. The primary water types present over the continental shelf off Pine Island Bay were Circumpolar Deep Water (CDW), modified Circumpolar Deep Water (mCDW), Shelf Water (SW), and Ice Shelf Water (ISW). As CDW transited the shelf, it transitioned into cooler, mCDW. In the upper 200 m, ISW dominated within 100 km of the ice shelf and SW further offshore. Within Pine Island Bay, the water column was partitioned into two primary layers based on their behavior: an upper outflowing layer from 100 m to 450 m composed of ISW with a significant meltwater component, 1%–2%, over an inflowing layer from ~550 m to the sea bed composed of mCDW. Due to the small cavity extent, the outflowing water was warmer than the seawater freezing point. The up...
Geoscience Letters, 2019
Vertical mixing is important in the ocean for maintaining its stratification, redistributing temp... more Vertical mixing is important in the ocean for maintaining its stratification, redistributing temperature and salinity, distributing nutrients and pollutants, and the energy cascade. It plays a key role in ocean energy transport, climate change, and marine ecosystems. Getting the mixing right in ocean circulation and climate models is critical in reproducing ocean and climate physics. Ocean models, like the Regional Ocean Modeling System (Rutgers ROMS 3.4), provide several options for determining vertical mixing through the vertical mixing parameterization schemes. To evaluate which of these methods best reproduces realistic vertical mixing by internal tides, simulations of baroclinic tides generated by a seamount were performed using seven different vertical mixing parameterizations: Mellor-Yamada 2.5 (MY), Large-McWilliams-Doney’s Kpp (LMD), Nakanishi-Niino’s modification of Mellor-Yamada (NN), and four versions of Generic Length Scale (GLS). The GLS versions in ROMS 3.4 severely o...
Geoscience Letters, 2017
Mixing at the ocean surface is key for atmosphere-ocean interactions and the distribution of heat... more Mixing at the ocean surface is key for atmosphere-ocean interactions and the distribution of heat, energy, and gases in the upper ocean. Winds are the primary force for surface mixing. To properly simulate upper ocean dynamics and the flux of these quantities within the upper ocean, models must reproduce mixing in the upper ocean. To evaluate the performance of the Regional Ocean Modeling System (ROMS) in replicating the surface mixing, the results of four different vertical mixing parameterizations were compared against observations, using the surface mixed layer depth, the temperature fields, and observed diffusivities for comparisons. The vertical mixing parameterizations investigated were Mellor-Yamada 2.5 level turbulent closure (MY), Large-McWilliams-Doney Kpp (LMD), Nakanishi-Niino (NN), and the generic length scale (GLS) schemes. This was done for one temperate site in deep water in the Eastern Pacific and three shallow water sites in the Baltic Sea. The model reproduced the surface mixed layer depth reasonably well for all sites; however, the temperature fields were reproduced well for the deep site, but not for the shallow Baltic Sea sites. In the Baltic Sea, the models overmixed the water column after a few days. Vertical temperature diffusivities were higher than those observed and did not show the temporal fluctuations present in the observations. The best performance was by NN and MY; however, MY became unstable in two of the shallow simulations with high winds. The performance of GLS nearly as good as NN and MY. LMD had the poorest performance as it generated temperature diffusivities that were too high and induced too much mixing. Further observational comparisons are needed to evaluate the effects of different stratification and wind conditions and the limitations on the vertical mixing parameterizations.
Frontiers in Marine Science, 2019
Newman et al. The Southern Ocean Observing System time series of key variables, and delivers the ... more Newman et al. The Southern Ocean Observing System time series of key variables, and delivers the greatest impact from data to all key end-users. Although the Southern Ocean remains one of the least-observed ocean regions, enhanced international coordination and advances in autonomous platforms have resulted in progress toward sustained observations of this region. Since 2009, the Southern Ocean community has deployed over 5700 observational platforms south of 40 • S. Large-scale, multi-year or sustained, multidisciplinary efforts have been supported and are now delivering observations of essential variables at space and time scales that enable assessment of changes being observed in Southern Ocean systems. The improved observational coverage, however, is predominantly for the open ocean, encompasses the summer, consists of primarily physical oceanographic variables, and covers surface to 2000 m. Significant gaps remain in observations of the ice-impacted ocean, the sea ice, depths >2000 m, the air-ocean-ice interface, biogeochemical and biological variables, and for seasons other than summer. Addressing these data gaps in a sustained way requires parallel advances in coordination networks, cyberinfrastructure and data management tools, observational platform and sensor technology, twoway platform interrogation and data-transmission technologies, modeling frameworks, intercalibration experiments, and development of internationally agreed sampling standards and requirements of key variables. This paper presents a community statement on the major scientific and observational progress of the last decade, and importantly, an assessment of key priorities for the coming decade, toward achieving the SOOS vision and delivering essential data to all end-users.
Journal of Geophysical Research: Oceans, 2019
Critical latitudes are a significant area of tidal dissipation. Generally, critical latitudes are... more Critical latitudes are a significant area of tidal dissipation. Generally, critical latitudes are taken to be the exact latitude where the tidal frequency equals the inertial frequency. However, the key is really where the tidal frequency equals the combination of planetary vorticity and relative vorticity from background currents. Although the influence of background currents on critical latitude effects and nonlinear interactions have been noted for many years, their exact impacts are not well known. The latitude dependence of critical latitude impacts on the tides, internal tides, and internal waves in the presence of background currents was investigated using the Regional Ocean Modeling System by shifting a small domain including a seamount from 20.6°to 38.6°S and comparing simulations with and without background currents. The diurnal kinetic energy with mesoscale currents was relatively unchanged for most latitudes, except for a slight decrease 1-4°poleward of the critical latitude. However, the semidiurnal and high-frequency (≥3 cycles per day) kinetic energy increased with the presence of mesoscale currents, especially within the diurnal critical latitude range. Spectral and nonlinear analyses indicated mesoscale currents broadened the range of critical latitude effects and enhanced energy transferring from diurnal frequencies to semidiurnal and high frequencies and from low to high mode waves. Local diffusivities increased, roughly an order of magnitude, when mesoscale currents were present. The impacts of mesoscale currents on the broadening of the critical latitude range and enhancement of nonlinear interactions were attributed to the additional relative vorticity and near-inertial internal waves generated by mesoscale currents.
The Density-Driven Winter Intensification of the Ross Sea Circulation
Journal of Geophysical Research: Oceans, 2018
Characterize the internal tides in the Indonesian Seas and determine how they may vary seasonally... more Characterize the internal tides in the Indonesian Seas and determine how they may vary seasonally and interannually as the thermocline structure changes. OBJECTIVES Our primary objective is to provide reliable estimates for the barotropic and baroclinic tides in the Indonesian Seas. We intend to determine: 1) specifically where in the Indonesian Seas baroclinic tides are generated and propagated, and, if time allows, 2) the effect of the seasonally and ENSO driven North Pacific versus South Pacific thermohaline structures on internal tide generation.
Tides, the PIG, and
Iop Conference Series Earth and Environmental Science, 2010
The present rapid melting of the Pine Island Glacier (PIG) has been attributed to basal melting d... more The present rapid melting of the Pine Island Glacier (PIG) has been attributed to basal melting driven by the ocean. Specifically, this ocean melting is attributed to currents and tides pumping "warm" Circumpolar Deep Water (CDW) into the ice shelf cavity. To identify tidal activity in the region, an observational time series of yo-yo CTD (Conductivity, Temperature, and Depth) data
IOP Conference Series: Earth and Environmental Science, 2010
Recently, there has been a great interest in the tidal contribution to vertical mixing in the oce... more Recently, there has been a great interest in the tidal contribution to vertical mixing in the ocean. In models, vertical mixing is estimated using parameterization of the sub-grid scale processes. Estimates of the vertical mixing varied widely depending on which vertical mixing parameterization was used. This study investigated the performance of ten different vertical mixing parameterizations in a terrain-following ocean model when simulating internal tides. The vertical mixing parameterization was found to have minor effects on the velocity fields at the tidal frequencies, but large effects on the estimates of vertical diffusivity of temperature. Although there was no definitive best performer for the vertical mixing parameterization, several parameterizations were eliminated based on comparison of the vertical diffusivity estimates with observations. The best performers were the new generic coefficients for the generic length scale schemes and Mellor-Yamada's 2.5 level closure scheme.