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• 1. [Article] Variability in the location of the Antarctic Polar Front (90°-20°W) from satellite sea surface temperature data

  Copyrighted by American Geophysical Union.

  Citation × Citation Citation Abstract Copy Title: Variability in the location of the Antarctic Polar Front (90°-20°W) from satellite sea surface temperature data Author: Moore, J. Keith, Abbott, Mark R., Richman, James Copyrighted by American Geophysical Union. Title: Variability in the location of the Antarctic Polar Front (90°-20°W) from satellite sea surface temperature data Author: Moore, J. Keith, Abbott, Mark R., Richman, James Copyrighted by American Geophysical Union. Close

• 2. [Article] Location and dynamics of the Antarctic Polar Front from satellite sea surface temperature data

  copyrighted by American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: Location and dynamics of the Antarctic Polar Front from satellite sea surface temperature data Author: Abbott, Mark R., Richman, James G., Moore, J. Keith copyrighted by American Geophysical Union Title: Location and dynamics of the Antarctic Polar Front from satellite sea surface temperature data Author: Abbott, Mark R., Richman, James G., Moore, J. Keith copyrighted by American Geophysical Union Close

• 3. [Article] Tidal and atmospheric forcing of the upper ocean in the Gulf of California, Part 1: Sea surface temperature variability

  Two years of satellite infrared imagery (1984–1986) are used to examine the sea surface temperature (SST) variability in the northern Gulf of California. Empirical orthogonal functions (EOFs) of the temporal ...

  Citation × Citation Citation Abstract Copy Title: Tidal and atmospheric forcing of the upper ocean in the Gulf of California, Part 1: Sea surface temperature variability Author: Winant, C. D., Abbott, Mark R., Paden, Cynthia A. Two years of satellite infrared imagery (1984–1986) are used to examine the sea surface temperature (SST) variability in the northern Gulf of California. Empirical orthogonal functions (EOFs) of the temporal and spatial SST variance for 20 monthly mean images show that the dominant SST patterns are generated by spatially varying tidal mixing in the presence of seasonal heating and cooling. These patterns are modified in the fall and winter when shelf temperatures south of Tiburon Island cool in response to upwelling-favorable winds. These same winds bring cold, dry air from off the continental United States, causing local cooling of the shallow northern shelf. During the rest of the year, the broad, shallow shelves are warmer than offshore. The seasonally reversing temperature patterns are consistent with recent hydrographic observations which show a cyclonic surface circulation in the summer and a weaker anticyclonic circulation during the rest of the year. Atmospheric forcing of the northern gulf appears to occur over large spatial scales. Area-averaged SSTs for the Guaymas Basi, island region, and northern basin show significant fluctuations which are highly correlated. These fluctuations in SST correspond to similar fluctuations in the air temperature which are related to synoptic weather events overf the gulf. During periods of particularly low wind speed, the air temperataure over the gulf incrases dramatically. By afternoon, intense heating of the sea surface results in the appearance of warm SST anomalies in the satellite data. These SSTs are approximately 2ºC warmer than surrounding SSTs and most likely occur as a result of a spatially varying wind field. A regression analysis of the SST relative to the fortnightly tidal range shows that tidal mixing occurs over the sills in the island region as well as on the shallow northern shelf. Mixing over the sills, however, occurs as a result of large breaking internal waves or internal hydraulic jumps which mix water over the upper 300–500 m. This mixing pumps heat away from the surface, deep into the water column, thereby maintaining the cool SSTs. Since mixing occurs over greater depths in the island region, the temperatures there are much colder than those generated by tidal mixing on the shallow shelves, resulting in the persistent pool of cool water evident in the satellite data. This cooler water is mixed horizontally by the basin-scale circulation, lowering the SSTs over much of the northern gulf. These reduced SSTs have a large impact on the surface heat flux by lowering the saturation vapor pressure of the air. As a result, the amount of heat lost to the atmosphere through the latent or evaporative heat flux is reduced. This may explain why the Gulf of California gains heat on an annual average rather than losing heat as occurs in the Mediterranean and Red seas where tidal mixing is not significant. Title: Tidal and atmospheric forcing of the upper ocean in the Gulf of California, Part 1: Sea surface temperature variability Author: Winant, C. D., Abbott, Mark R., Paden, Cynthia A. Two years of satellite infrared imagery (1984–1986) are used to examine the sea surface temperature (SST) variability in the northern Gulf of California. Empirical orthogonal functions (EOFs) of the temporal and spatial SST variance for 20 monthly mean images show that the dominant SST patterns are generated by spatially varying tidal mixing in the presence of seasonal heating and cooling. These patterns are modified in the fall and winter when shelf temperatures south of Tiburon Island cool in response to upwelling-favorable winds. These same winds bring cold, dry air from off the continental United States, causing local cooling of the shallow northern shelf. During the rest of the year, the broad, shallow shelves are warmer than offshore. The seasonally reversing temperature patterns are consistent with recent hydrographic observations which show a cyclonic surface circulation in the summer and a weaker anticyclonic circulation during the rest of the year. Atmospheric forcing of the northern gulf appears to occur over large spatial scales. Area-averaged SSTs for the Guaymas Basi, island region, and northern basin show significant fluctuations which are highly correlated. These fluctuations in SST correspond to similar fluctuations in the air temperature which are related to synoptic weather events overf the gulf. During periods of particularly low wind speed, the air temperataure over the gulf incrases dramatically. By afternoon, intense heating of the sea surface results in the appearance of warm SST anomalies in the satellite data. These SSTs are approximately 2ºC warmer than surrounding SSTs and most likely occur as a result of a spatially varying wind field. A regression analysis of the SST relative to the fortnightly tidal range shows that tidal mixing occurs over the sills in the island region as well as on the shallow northern shelf. Mixing over the sills, however, occurs as a result of large breaking internal waves or internal hydraulic jumps which mix water over the upper 300–500 m. This mixing pumps heat away from the surface, deep into the water column, thereby maintaining the cool SSTs. Since mixing occurs over greater depths in the island region, the temperatures there are much colder than those generated by tidal mixing on the shallow shelves, resulting in the persistent pool of cool water evident in the satellite data. This cooler water is mixed horizontally by the basin-scale circulation, lowering the SSTs over much of the northern gulf. These reduced SSTs have a large impact on the surface heat flux by lowering the saturation vapor pressure of the air. As a result, the amount of heat lost to the atmosphere through the latent or evaporative heat flux is reduced. This may explain why the Gulf of California gains heat on an annual average rather than losing heat as occurs in the Mediterranean and Red seas where tidal mixing is not significant. Close

• 4. [Article] Surface patterns in temperature, flow, phytoplankton biomass, and species composition in the coastal transition zone of northern California

  Satellite thermal imagery and in situ biological and physical data are presented that describe the spatial variability of phytoplankton biomass and species composition in relation to the physical structure ...

  Citation × Citation Citation Abstract Copy Title: Surface patterns in temperature, flow, phytoplankton biomass, and species composition in the coastal transition zone of northern California Author: Abbott, Mark R., Hood, Raleigh R., Huyer, Adriana, 1945-, Kosro, P. Michael, 1951- Satellite thermal imagery and in situ biological and physical data are presented that describe the spatial variability of phytoplankton biomass and species composition in relation to the physical structure at the sea surface during persistent upwelling off northern California. Surface patterns in temperature, geostrophic velocity, chlorophyll, and particle size structure show that the coastal zone was dominated by two water masses separated by a well-defined physical boundary. This boundary is apparent in satellite thermal imagery as a cold front and in dynamic height as a meandering jet in the California Current. On the landward side of the front (jet) we observed cold, coastal water that was relatively enriched in phytoplankton biomass, due to the presence of large diatoms. On the seaward side of the front (jet) we observed relatively warm water where the phytoplankton biomass was low and the diatoms were largely absent. Broad tongues and narrow filaments of cold, chlorophyll-rich water that extended over 100 km offshore were present in our study area. These features were bounded by the meandering coastal jet. The coldest, most chlorophyll-rich water in these tongues and filaments was located between the onshore and offshore flows in relatively slow moving water, but entrainment of coastal water into the jet was apparent. Title: Surface patterns in temperature, flow, phytoplankton biomass, and species composition in the coastal transition zone of northern California Author: Abbott, Mark R., Hood, Raleigh R., Huyer, Adriana, 1945-, Kosro, P. Michael, 1951- Satellite thermal imagery and in situ biological and physical data are presented that describe the spatial variability of phytoplankton biomass and species composition in relation to the physical structure at the sea surface during persistent upwelling off northern California. Surface patterns in temperature, geostrophic velocity, chlorophyll, and particle size structure show that the coastal zone was dominated by two water masses separated by a well-defined physical boundary. This boundary is apparent in satellite thermal imagery as a cold front and in dynamic height as a meandering jet in the California Current. On the landward side of the front (jet) we observed cold, coastal water that was relatively enriched in phytoplankton biomass, due to the presence of large diatoms. On the seaward side of the front (jet) we observed relatively warm water where the phytoplankton biomass was low and the diatoms were largely absent. Broad tongues and narrow filaments of cold, chlorophyll-rich water that extended over 100 km offshore were present in our study area. These features were bounded by the meandering coastal jet. The coldest, most chlorophyll-rich water in these tongues and filaments was located between the onshore and offshore flows in relatively slow moving water, but entrainment of coastal water into the jet was apparent. Close

• 5. [Article] Drifter observations of a cold filament off Point Arena, California, in July 1988

  We use the position fixes and temperature readings from 56 Tristar-II mixed-layer drifters, in conjunction with advanced very high resolution radiometer images, to provide a description of the mesoscale ...

  Citation × Citation Citation Abstract Copy Title: Drifter observations of a cold filament off Point Arena, California, in July 1988 Author: Abbott, Mark R., Niiler, Pearn P., Brink, Kenneth H., Swenson, Mark S. We use the position fixes and temperature readings from 56 Tristar-II mixed-layer drifters, in conjunction with advanced very high resolution radiometer images, to provide a description of the mesoscale variability of the flows associated with cold-water filaments in the California Current system off northern California in July 1988. We find that the northern, offshore temperature front of the filament is convergent and is closely associated with the core of a high-speed (>100 cm/s) jet that has a broader spatial scale than the cold-water filament. Mesoscale features are observed to be related to all developments of the cold-water filament on a variety of time scales (1–30 days). In one well-observed feature, estimates of vertical velocity (w) based on a vorticity budget are -20 m/d over an area of 150 km2 and are associated with a gain of vorticity. Estimates of w based on a local heat budget following a drifter are about 3 times larger over an area of 60 km2. These intense downwelling features are also places where horizontal stirring occurs. Title: Drifter observations of a cold filament off Point Arena, California, in July 1988 Author: Abbott, Mark R., Niiler, Pearn P., Brink, Kenneth H., Swenson, Mark S. We use the position fixes and temperature readings from 56 Tristar-II mixed-layer drifters, in conjunction with advanced very high resolution radiometer images, to provide a description of the mesoscale variability of the flows associated with cold-water filaments in the California Current system off northern California in July 1988. We find that the northern, offshore temperature front of the filament is convergent and is closely associated with the core of a high-speed (>100 cm/s) jet that has a broader spatial scale than the cold-water filament. Mesoscale features are observed to be related to all developments of the cold-water filament on a variety of time scales (1–30 days). In one well-observed feature, estimates of vertical velocity (w) based on a vorticity budget are -20 m/d over an area of 150 km2 and are associated with a gain of vorticity. Estimates of w based on a local heat budget following a drifter are about 3 times larger over an area of 60 km2. These intense downwelling features are also places where horizontal stirring occurs. Close

• 6. [Article] Role of late winter mesoscale events in the biogeochemical variability of the upper water column of the North Pacific Subtropical Gyre

  Continuous records of upper water column (0–150 m) temperature profiles, spectral distribution of downwelling irradiance, and phytoplankton solar-induced fluorescence at 25 m depth were obtained during ...

  Citation × Citation Citation Abstract Copy Title: Role of late winter mesoscale events in the biogeochemical variability of the upper water column of the North Pacific Subtropical Gyre Author: Abbott, Mark R., Karl, David M., Lukas, Roger, Freilich, Michael H., Flament, P., Letelier, Ricardo M., Strub, P. Ted Continuous records of upper water column (0–150 m) temperature profiles, spectral distribution of downwelling irradiance, and phytoplankton solar-induced fluorescence at 25 m depth were obtained during the inaugural deployment of the Hawaii Air-sea Logging Experiment, A Long-term Oligotrophic Habitat Assessment (HALE ALOHA) mooring, near the Hawaii Ocean Time-series (HOT) Station ALOHA (22 degrees 45'N; 158 degrees 00'W). The temperature record showed a strong upwelling event in March-April 1997, displacing the thermocline by 120 m. Remote sensing satellite (NSCAT and TOPEX/ERS 2) analyses suggest that the observed upwelling was a result of strong wind divergence and the passage of a cyclonic eddy through the HOT program study area, At the onset of the upwelling event increases in colored dissolved organic matter (CDOM) and chlorophyll fluorescence efficiency in the upper water column were detected by changes in the spectral distribution of the downwelling irradiance. The 0–25 m mean chlorophyll a (chl a) concentration increased threefold toward the end of the upwelling period. Water column samples collected during the monthly HOT cruises also indicate that the relative contribution of diatoms to total chi a increased twofold inside the eddy. The long-term temporal variability in frequency and intensity of these poorly resolved mesoscale events might be key factors determining the structure of the pelagic ecosystem in the North Pacific Subtropical Gyre. Integrating multi-year remote sensing satellite, moored, and vessel-based time series records permits a quantification of the spatial and temporal scale of upper water column perturbations and the characterization of the pelagic ecosystem response at various timescales. Title: Role of late winter mesoscale events in the biogeochemical variability of the upper water column of the North Pacific Subtropical Gyre Author: Abbott, Mark R., Karl, David M., Lukas, Roger, Freilich, Michael H., Flament, P., Letelier, Ricardo M., Strub, P. Ted Continuous records of upper water column (0–150 m) temperature profiles, spectral distribution of downwelling irradiance, and phytoplankton solar-induced fluorescence at 25 m depth were obtained during the inaugural deployment of the Hawaii Air-sea Logging Experiment, A Long-term Oligotrophic Habitat Assessment (HALE ALOHA) mooring, near the Hawaii Ocean Time-series (HOT) Station ALOHA (22 degrees 45'N; 158 degrees 00'W). The temperature record showed a strong upwelling event in March-April 1997, displacing the thermocline by 120 m. Remote sensing satellite (NSCAT and TOPEX/ERS 2) analyses suggest that the observed upwelling was a result of strong wind divergence and the passage of a cyclonic eddy through the HOT program study area, At the onset of the upwelling event increases in colored dissolved organic matter (CDOM) and chlorophyll fluorescence efficiency in the upper water column were detected by changes in the spectral distribution of the downwelling irradiance. The 0–25 m mean chlorophyll a (chl a) concentration increased threefold toward the end of the upwelling period. Water column samples collected during the monthly HOT cruises also indicate that the relative contribution of diatoms to total chi a increased twofold inside the eddy. The long-term temporal variability in frequency and intensity of these poorly resolved mesoscale events might be key factors determining the structure of the pelagic ecosystem in the North Pacific Subtropical Gyre. Integrating multi-year remote sensing satellite, moored, and vessel-based time series records permits a quantification of the spatial and temporal scale of upper water column perturbations and the characterization of the pelagic ecosystem response at various timescales. Close

• 7. [Article] Tidal and atmospheric forcing of the upper ocean in the Gulf of California, Part 2: Surface heat flux

  Satellite infrared imagery and coastal meteorological data for March 1984 through February 1985 are used to estimate the net annual surface heat flux for the northern Gulf of California. The average annual ...

  Citation × Citation Citation Abstract Copy Title: Tidal and atmospheric forcing of the upper ocean in the Gulf of California, Part 2: Surface heat flux Author: Abbott, Mark R., Winant, Clinton D., Paden, Cynthia A. Satellite infrared imagery and coastal meteorological data for March 1984 through February 1985 are used to estimate the net annual surface heat flux for the northern Gulf of California. The average annual surface heat flux for the area north of Guaymas and Santa Rosalia is estimated to be +74 W m-2 for the 1984–1985 time period. This is comparable to the +20–50 W m-2 previously obtained from heat and freshwater transport estimates made with hydrographic surveys from different years and months. The spatial distribution of the net surface heat flux shows a net gain of heat over the whole northern gulf. Except for a local maximum near San Esteban Island, the largest heat gain (+110–120 W m-2) occurs in the Ballenas and Salsipuedes channels, where strong tidal mixing produces anomalously cold sea surface temperatures (SSTs) over much of the year. The lowest heat gain occurs in the Guaymas Basin (+40–50 W m-2), where SSTs are consistently warmer. In the relatively shallow northern basin the net surface heat flux is fairly uniform, with a net annual gain of approximately +70 W m-2. A local minimum in heat gain (approximately +60 W m-2) is observed over the shelf in the northwest, where spring and summer surface temperatures are particularly high. A similar minimum in heat gain over the shelf was observed in a separate study in which historical SSTs and 7 years (1979–1986) of meteorological data from Puerto Penasco were used to estimate the net surface heat flux for the northern basin. In that study, however, the heat fluxes were higher, with a gain of +100 W m-2 over the shelf and +114 W m-2 in the northern basin. These larger values are directly attributable to the higher humidities in the 1979–1986 study compared to the 1984-1985 satellite study. Significant interannual variations in humidity appear to occur in the northern gulf, with relatively high humidities during El Niño years and low humidities during anti-El Niño years. High humidities reduce evaporation and the associated latent heat loss, promoting a net annual heat gain. In the northern Gulf of California, however, tidal mixing appears to play a key role in the observed gain of heat. Deep mixing in the island region produces a persistent pool of cold water which is mixed horizontally by the large-scale circulation, lowering surface temperatures over most of the northern gulf. These cold SSTs decrease evaporation by reducing the saturation vapor pressure of the overlying air. As a result, heat loss is substantially reduced, even when humidities are low. By removing heat from the surface, tidal mixing alters the time scale of air-sea interaction and reduces or possibly even inhibits the formation of deep water masses via convection. Over climatological timescales, it may be tidal mixing that ultimately maintains the estuarinelike circulation in the northern Gulf of California, differentiating it from the Mediterranean and Red seas, which lose heat to the atmosphere. Title: Tidal and atmospheric forcing of the upper ocean in the Gulf of California, Part 2: Surface heat flux Author: Abbott, Mark R., Winant, Clinton D., Paden, Cynthia A. Satellite infrared imagery and coastal meteorological data for March 1984 through February 1985 are used to estimate the net annual surface heat flux for the northern Gulf of California. The average annual surface heat flux for the area north of Guaymas and Santa Rosalia is estimated to be +74 W m-2 for the 1984–1985 time period. This is comparable to the +20–50 W m-2 previously obtained from heat and freshwater transport estimates made with hydrographic surveys from different years and months. The spatial distribution of the net surface heat flux shows a net gain of heat over the whole northern gulf. Except for a local maximum near San Esteban Island, the largest heat gain (+110–120 W m-2) occurs in the Ballenas and Salsipuedes channels, where strong tidal mixing produces anomalously cold sea surface temperatures (SSTs) over much of the year. The lowest heat gain occurs in the Guaymas Basin (+40–50 W m-2), where SSTs are consistently warmer. In the relatively shallow northern basin the net surface heat flux is fairly uniform, with a net annual gain of approximately +70 W m-2. A local minimum in heat gain (approximately +60 W m-2) is observed over the shelf in the northwest, where spring and summer surface temperatures are particularly high. A similar minimum in heat gain over the shelf was observed in a separate study in which historical SSTs and 7 years (1979–1986) of meteorological data from Puerto Penasco were used to estimate the net surface heat flux for the northern basin. In that study, however, the heat fluxes were higher, with a gain of +100 W m-2 over the shelf and +114 W m-2 in the northern basin. These larger values are directly attributable to the higher humidities in the 1979–1986 study compared to the 1984-1985 satellite study. Significant interannual variations in humidity appear to occur in the northern gulf, with relatively high humidities during El Niño years and low humidities during anti-El Niño years. High humidities reduce evaporation and the associated latent heat loss, promoting a net annual heat gain. In the northern Gulf of California, however, tidal mixing appears to play a key role in the observed gain of heat. Deep mixing in the island region produces a persistent pool of cold water which is mixed horizontally by the large-scale circulation, lowering surface temperatures over most of the northern gulf. These cold SSTs decrease evaporation by reducing the saturation vapor pressure of the overlying air. As a result, heat loss is substantially reduced, even when humidities are low. By removing heat from the surface, tidal mixing alters the time scale of air-sea interaction and reduces or possibly even inhibits the formation of deep water masses via convection. Over climatological timescales, it may be tidal mixing that ultimately maintains the estuarinelike circulation in the northern Gulf of California, differentiating it from the Mediterranean and Red seas, which lose heat to the atmosphere. Close

• 8. [Article] Measuring the Natural Fluorescence of Phytoplankton Cultures

  A laboratory instrument, the Natural Fluorescence Chemostat, was developed to measure the natural fluorescence of phytoplankton cultures. With this instrument, the physical and chemical environment of ...

  Citation × Citation Citation Abstract Copy Title: Measuring the Natural Fluorescence of Phytoplankton Cultures Author: Booth, C. R., Kiefer, D. A., Abbott, Mark R., Letelier, R. M., Laney, S. R., Desiderio, R. A. A laboratory instrument, the Natural Fluorescence Chemostat, was developed to measure the natural fluorescence of phytoplankton cultures. With this instrument, the physical and chemical environment of a culture can be manipulated with respect to temperature, pH, nutrient delivery rate, and light intensity, while the natural fluorescence and a weak stimulated fluorescence are continuously recorded with high temporal resolution. The geometry and spectral distribution of the artificial light field minimize the contribution of scattering to the natural fluorescence signal. Preliminary investigations with the marine diatom T. weissflogii (Bacillariophyceae) indicate that the instrument can detect natural fluorescence signals in broadband artificial light fields as bright as 1250 μmol quanta m⁻² s⁻¹. Since the influence of environmental factors on natural fluorescence is not well understood, laboratory experiments are essential for investigating how ocean physics and chemistry influence this signal. This instrument provides a quantitative means to examine how the magnitude and kinetics of phytoplankton natural fluorescence vary in response to changes in the physical and chemical environment. Title: Measuring the Natural Fluorescence of Phytoplankton Cultures Author: Booth, C. R., Kiefer, D. A., Abbott, Mark R., Letelier, R. M., Laney, S. R., Desiderio, R. A. A laboratory instrument, the Natural Fluorescence Chemostat, was developed to measure the natural fluorescence of phytoplankton cultures. With this instrument, the physical and chemical environment of a culture can be manipulated with respect to temperature, pH, nutrient delivery rate, and light intensity, while the natural fluorescence and a weak stimulated fluorescence are continuously recorded with high temporal resolution. The geometry and spectral distribution of the artificial light field minimize the contribution of scattering to the natural fluorescence signal. Preliminary investigations with the marine diatom T. weissflogii (Bacillariophyceae) indicate that the instrument can detect natural fluorescence signals in broadband artificial light fields as bright as 1250 μmol quanta m⁻² s⁻¹. Since the influence of environmental factors on natural fluorescence is not well understood, laboratory experiments are essential for investigating how ocean physics and chemistry influence this signal. This instrument provides a quantitative means to examine how the magnitude and kinetics of phytoplankton natural fluorescence vary in response to changes in the physical and chemical environment. Close

• 9. [Article] Scales of variability of bio-optical properties as obersved from near-surface drifters

  copyrighted by American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: Scales of variability of bio-optical properties as obersved from near-surface drifters Author: Davis, Curtiss O., Booth, C. R., Abbott, Mark R., Blasco, Dolors, Swenson, Mark S., Brink, Kenneth H., Codispoti, L. A. copyrighted by American Geophysical Union Title: Scales of variability of bio-optical properties as obersved from near-surface drifters Author: Davis, Curtiss O., Booth, C. R., Abbott, Mark R., Blasco, Dolors, Swenson, Mark S., Brink, Kenneth H., Codispoti, L. A. copyrighted by American Geophysical Union Close

• 10. [Article] Mixing and the dynamics of the deep chlorophyll maximum in Lake Tahoe

  Chlorophyll-temperature profiles were measured across Lake Tahoe about every 10 days from April through July 1980. Analysis of the 123 profiles and associated productivity and nutrient data identified ...

  Citation × Citation Citation Abstract Copy Title: Mixing and the dynamics of the deep chlorophyll maximum in Lake Tahoe Author: Abbott, Mark R., Powell, Thomas M., Denman, Kenneth L., Richards, Robert C., Goldman, Charles R., Richerson, Peter J. Chlorophyll-temperature profiles were measured across Lake Tahoe about every 10 days from April through July 1980. Analysis of the 123 profiles and associated productivity and nutrient data identified three important processes in the formation and dynamics of the deep chlorophyll maximum (DCM): turbulent diffusion, nutrient supply rate, and light availability. Seasonal variation in these three processes resulted in three regimes: a diffusion-dominated regime with a weak DCM, a variable-mixing regime with a pronounced, nutrient supply-dominated DCM, and a stable regime with a deep, moderate light availability-dominated DCM. The transition between the first two regimes occurred in about 10 days, the transition between the last two more gradually over about 3 weeks. The degree of spatial variability of the DCM was highest in the second regime and lowest in the third. These data indicate that the DCM in Lake Tahoe is constant in neither time nor space. Title: Mixing and the dynamics of the deep chlorophyll maximum in Lake Tahoe Author: Abbott, Mark R., Powell, Thomas M., Denman, Kenneth L., Richards, Robert C., Goldman, Charles R., Richerson, Peter J. Chlorophyll-temperature profiles were measured across Lake Tahoe about every 10 days from April through July 1980. Analysis of the 123 profiles and associated productivity and nutrient data identified three important processes in the formation and dynamics of the deep chlorophyll maximum (DCM): turbulent diffusion, nutrient supply rate, and light availability. Seasonal variation in these three processes resulted in three regimes: a diffusion-dominated regime with a weak DCM, a variable-mixing regime with a pronounced, nutrient supply-dominated DCM, and a stable regime with a deep, moderate light availability-dominated DCM. The transition between the first two regimes occurred in about 10 days, the transition between the last two more gradually over about 3 weeks. The degree of spatial variability of the DCM was highest in the second regime and lowest in the third. These data indicate that the DCM in Lake Tahoe is constant in neither time nor space. Close