Search

Search Results

• 1. [Article] On the abyssal temperatures of the world oceans

  In comparison with solar radiation, the energy of geothermal heat flowing through the sea bottom is extremely small; nevertheless, this energy is not insignificant in the circulation of the bottom water. Calculations ...

  Citation × Citation Citation Abstract Copy Title: On the abyssal temperatures of the world oceans Author: Olson, Boyd Ellertson In comparison with solar radiation, the energy of geothermal heat flowing through the sea bottom is extremely small; nevertheless, this energy is not insignificant in the circulation of the bottom water. Calculations indicate that in the deep basins of the South Atlantic the water volume transport necessary to remove this heat is at least one-tenth of the total northward flow of Antarctic Bottom Water. Plots of mean values of near bottom salinity and oxygen versus mean potential temperatures help to trace the movement of the bottom water. Geothermal and adiabatic warming associated with downslope flow combine to produce a deep temperature (in situ) minimum in portions of most of the deep basins of the world. Adiabatic or near adiabatic temperature gradients have been measured near the bottom in many of these basins. Evidence of superadiabatic gradients from temperature measurements made with reversing thermometers is inconclusive; however, careful measurements with closely spaced thermometers suggest that such gradients do exist over vertical distances of a few hundred meters in some of the deepest basins. Decreasing potential density with depth, as found in some of the Atlantic Basins in association with sharp temperature and salinity gradients, is not necessarily an indication of unstable equilibrium. This is demonstrated by the results of stability calculations in the manner prescribed by Hesselberg and Sverdrup (1915). Title: On the abyssal temperatures of the world oceans Author: Olson, Boyd Ellertson In comparison with solar radiation, the energy of geothermal heat flowing through the sea bottom is extremely small; nevertheless, this energy is not insignificant in the circulation of the bottom water. Calculations indicate that in the deep basins of the South Atlantic the water volume transport necessary to remove this heat is at least one-tenth of the total northward flow of Antarctic Bottom Water. Plots of mean values of near bottom salinity and oxygen versus mean potential temperatures help to trace the movement of the bottom water. Geothermal and adiabatic warming associated with downslope flow combine to produce a deep temperature (in situ) minimum in portions of most of the deep basins of the world. Adiabatic or near adiabatic temperature gradients have been measured near the bottom in many of these basins. Evidence of superadiabatic gradients from temperature measurements made with reversing thermometers is inconclusive; however, careful measurements with closely spaced thermometers suggest that such gradients do exist over vertical distances of a few hundred meters in some of the deepest basins. Decreasing potential density with depth, as found in some of the Atlantic Basins in association with sharp temperature and salinity gradients, is not necessarily an indication of unstable equilibrium. This is demonstrated by the results of stability calculations in the manner prescribed by Hesselberg and Sverdrup (1915). Close

• 2. [Article] Temperature microstructure profiles at Ocean Station P : preliminary results from the MILE experiment

  Citation × Citation Citation Abstract Copy Title: Temperature microstructure profiles at Ocean Station P : preliminary results from the MILE experiment Author: Caldwell, D. R. (Douglas R.), Dillon, T. M. (Thomas M.), Oregon State University. School of Oceanography Title: Temperature microstructure profiles at Ocean Station P : preliminary results from the MILE experiment Author: Caldwell, D. R. (Douglas R.), Dillon, T. M. (Thomas M.), Oregon State University. School of Oceanography Close

• 3. [Article] Small scale temperature structure of the upper ocean

  Citation × Citation Citation Abstract Copy Title: Small scale temperature structure of the upper ocean Author: Simpson, James J. (James Joseph) Title: Small scale temperature structure of the upper ocean Author: Simpson, James J. (James Joseph) Close

• 4. [Article] The fluxes of latent and sensible heat in the marine boundary layer

  Measurements of the fluctuations of humidity, temperature and velocity were made in the marine boundary layer. The humidity fluctuations were measured with a Lyman-alpha humidiometer. Temperature fluctuations ...

  Citation × Citation Citation Abstract Copy Title: The fluxes of latent and sensible heat in the marine boundary layer Author: Phelps, George Thomas Measurements of the fluctuations of humidity, temperature and velocity were made in the marine boundary layer. The humidity fluctuations were measured with a Lyman-alpha humidiometer. Temperature fluctuations were measured with a dry thermocouple and a platinum resistance thermometer. Velocity fluctuations were measured with a three component sonic anemometer. These measurements were made from the Floating Instrument Platform (FLIP) operated by the Scripps Institution of Oceanography near San Diego in February, 1969 and during the Barbados Oceanographic and Meteorological Expedition (BOMEX) in May 1969. The data were processed by digital techniques and the various spectra, cospectra and quadspectra between the velocities, humidity and temperature were obtained. Integrals of the cospectra were produced which allowed estimates of the fluxes of latent and sensible heat to be made. The normalized spectra of humidity fluctuations in San Diego and BOMEX have similar shapes. The normalized cospectra between vertical velocity and humidity in San Diego and BOMEX have similar shapes. Universal forms for the normalized humidity spectrum and the normalized cospectrum between vertical velocity and humidity may exist. The normalized spectra of the temperature fluctuations in San Diego and BOMEX have different shapes. The differences in shapes may be related to stronger radiation effects during BOMEX than in San Diego. The normalized cospectra between vertical velocity and temperature in San Diego and BOMEX also have different shapes. It is probable that a universal form does not exist for the normalized temperature spectrum or for the normalized cospectrum between vertical velocity and temperature. Directly measured values of the latent and sensible heat fluxes were used to test the validity of the bulk aerodynamic method of predicting the latent and sensible heat fluxes from the mean wind speed and mean air-sea humidity or temperature differences. The limited results from San Diego indicate that the sensible heat flux may probably be predicted from the mean wind speed and the mean air-sea temperature difference in temperate regions. The bulk aerodynamic method was not useful for predicting the sensible heat flux in BOMEX. The observed values for the sensible heat flux were much larger than would be predicted. The latent heat flux could be predicted from the mean wind speed and the mean air-sea absolute humidity difference with a probable error of less than 20%. The validity of the formula developed by Bowen (1926) for predicting the Bowen ratio (sensible heat flux/latent heat flux) was tested with directly measured values of the Bowen ratio. It was found that in San Diego the Bowen ratio could be predicted with a probable error of 15%. The Bowen ratio predicted for BOMEX was too low by a factor of two or more. The ability to predict the Bowen ratio from the ratio of the temperature fluctuations to the humidity fluctuations in the 0.05-0.1 Hz range was investigated. The method predicted the Bowen ratio with a probable error of 15% in San Diego and 20% in BOMEX. Title: The fluxes of latent and sensible heat in the marine boundary layer Author: Phelps, George Thomas Measurements of the fluctuations of humidity, temperature and velocity were made in the marine boundary layer. The humidity fluctuations were measured with a Lyman-alpha humidiometer. Temperature fluctuations were measured with a dry thermocouple and a platinum resistance thermometer. Velocity fluctuations were measured with a three component sonic anemometer. These measurements were made from the Floating Instrument Platform (FLIP) operated by the Scripps Institution of Oceanography near San Diego in February, 1969 and during the Barbados Oceanographic and Meteorological Expedition (BOMEX) in May 1969. The data were processed by digital techniques and the various spectra, cospectra and quadspectra between the velocities, humidity and temperature were obtained. Integrals of the cospectra were produced which allowed estimates of the fluxes of latent and sensible heat to be made. The normalized spectra of humidity fluctuations in San Diego and BOMEX have similar shapes. The normalized cospectra between vertical velocity and humidity in San Diego and BOMEX have similar shapes. Universal forms for the normalized humidity spectrum and the normalized cospectrum between vertical velocity and humidity may exist. The normalized spectra of the temperature fluctuations in San Diego and BOMEX have different shapes. The differences in shapes may be related to stronger radiation effects during BOMEX than in San Diego. The normalized cospectra between vertical velocity and temperature in San Diego and BOMEX also have different shapes. It is probable that a universal form does not exist for the normalized temperature spectrum or for the normalized cospectrum between vertical velocity and temperature. Directly measured values of the latent and sensible heat fluxes were used to test the validity of the bulk aerodynamic method of predicting the latent and sensible heat fluxes from the mean wind speed and mean air-sea humidity or temperature differences. The limited results from San Diego indicate that the sensible heat flux may probably be predicted from the mean wind speed and the mean air-sea temperature difference in temperate regions. The bulk aerodynamic method was not useful for predicting the sensible heat flux in BOMEX. The observed values for the sensible heat flux were much larger than would be predicted. The latent heat flux could be predicted from the mean wind speed and the mean air-sea absolute humidity difference with a probable error of less than 20%. The validity of the formula developed by Bowen (1926) for predicting the Bowen ratio (sensible heat flux/latent heat flux) was tested with directly measured values of the Bowen ratio. It was found that in San Diego the Bowen ratio could be predicted with a probable error of 15%. The Bowen ratio predicted for BOMEX was too low by a factor of two or more. The ability to predict the Bowen ratio from the ratio of the temperature fluctuations to the humidity fluctuations in the 0.05-0.1 Hz range was investigated. The method predicted the Bowen ratio with a probable error of 15% in San Diego and 20% in BOMEX. Close

• 5. [Article] On the reduction and interpretation of ocean-floor temperature and heat flow data

  In this thesis, the interpretation and reduction of ocean heat flow measurements are discussed on the basis of theoretical models. The instrument effect x heat flow measurements is investigated for the case ...

  Citation × Citation Citation Abstract Copy Title: On the reduction and interpretation of ocean-floor temperature and heat flow data Author: Shih, Keh-gong In this thesis, the interpretation and reduction of ocean heat flow measurements are discussed on the basis of theoretical models. The instrument effect x heat flow measurements is investigated for the case of long period measurements by studying the heat conduction along the measurement probe for both steady and unsteady state bottom temperatures. This effect is found to be unimportant. Measurement errors due to recent bottom temperature transients are studied and the possible magnitude of such errors is estimated. Moreover, effects of climatic variation on the ocean floor temperature are estimated on the basis of diffusion models. It is shown that climatic variations with periods longer than one thousand years will be unattenuated and will affect the entire ocean floor. The perturbation method is used to study the effects of an irregular topography and a variable thickness of ocean floor sediments on the heat flow. Some special examples are given to provide a comparison between the perturbation solutions and exact solutions of similar problems. The perturbation method is also applied to a buried body with different thermal conductivity from its surroundings and the reliability of the perturbation solution is examined. Heat flow anomalies due to heat transport by magma intruded into crustal layers is studied by solving the heat conduction equation. It is shown that magmatic intrusions can lead to very large surface heat flow anomalies. Finally, the possibility of deriving the ocean floor thermal gradient on the basis of on-ship measurements performed on sediment cores is investigated. The results appear positive. The temperature variations in flowing wells and the temperature variation in a cylindrical sediment core influenced by the movement of water along the axis of the core are also studied. Title: On the reduction and interpretation of ocean-floor temperature and heat flow data Author: Shih, Keh-gong In this thesis, the interpretation and reduction of ocean heat flow measurements are discussed on the basis of theoretical models. The instrument effect x heat flow measurements is investigated for the case of long period measurements by studying the heat conduction along the measurement probe for both steady and unsteady state bottom temperatures. This effect is found to be unimportant. Measurement errors due to recent bottom temperature transients are studied and the possible magnitude of such errors is estimated. Moreover, effects of climatic variation on the ocean floor temperature are estimated on the basis of diffusion models. It is shown that climatic variations with periods longer than one thousand years will be unattenuated and will affect the entire ocean floor. The perturbation method is used to study the effects of an irregular topography and a variable thickness of ocean floor sediments on the heat flow. Some special examples are given to provide a comparison between the perturbation solutions and exact solutions of similar problems. The perturbation method is also applied to a buried body with different thermal conductivity from its surroundings and the reliability of the perturbation solution is examined. Heat flow anomalies due to heat transport by magma intruded into crustal layers is studied by solving the heat conduction equation. It is shown that magmatic intrusions can lead to very large surface heat flow anomalies. Finally, the possibility of deriving the ocean floor thermal gradient on the basis of on-ship measurements performed on sediment cores is investigated. The results appear positive. The temperature variations in flowing wells and the temperature variation in a cylindrical sediment core influenced by the movement of water along the axis of the core are also studied. Close

• 6. [Article] Carpenter's oxygen solubility tables and nomograph for seawater as a function of temperature and salinity

  Citation × Citation Citation Abstract Copy Title: Carpenter's oxygen solubility tables and nomograph for seawater as a function of temperature and salinity Author: Gilbert, William E., Pawley, Walter H., Park, Kihlo, Oregon State University. Dept. of Oceanography Title: Carpenter's oxygen solubility tables and nomograph for seawater as a function of temperature and salinity Author: Gilbert, William E., Pawley, Walter H., Park, Kihlo, Oregon State University. Dept. of Oceanography Close

• 7. [Article] Ocean Temperature Variability during the Late Pleistocene

  This dissertation explores one overarching question relevant to the paleoclimate of the latest Pleistocene glacial cycle (approximately the last 130,000 years): “How did spatial and temporal evolution ...

  Citation × Citation Citation Abstract Copy Title: Ocean Temperature Variability during the Late Pleistocene Author: Hoffman, Jeremy Scott This dissertation explores one overarching question relevant to the paleoclimate of the latest Pleistocene glacial cycle (approximately the last 130,000 years): “How did spatial and temporal evolution of ocean temperature, both at the surface and interior, relate to other parts of the climate system in the late Pleistocene?” Results from three studies are presented that seek to address longstanding questions in paleoceanography and paleoclimatology for the late Pleistocene using a combination of novel and accepted statistical and geochemical analysis techniques and leveraging comparisons with available global climate model data. The last interglaciation (LIG; ~129-116 ka) was the most recent period in Earth’s history with higher-than-present global sea level (≥6-9 m) under similar-to-preindustrial concentrations of atmospheric CO₂. This suggests that additional feedbacks related to albedo, insolation, and ocean overturning circulation may have resulted in the apparent warming required to cause the higher sea level. Our understanding of how much warmer the LIG was relative to the present interglaciation remains uncertain, however, with current estimates suggesting that sea-surface temperatures (SSTs) were 0-2°C warmer than late-20th century average global temperatures. We present a global compilation of proxy-based annual SST spanning the LIG. Using Monte Carlo and Bayesian techniques to propagate uncertainties in age-model and proxy-based SST reconstructions, our results quantify the spatial timing, amplitude, and uncertainty in global and regional SST change during the LIG. Our conclusions suggest that the LIG surface ocean was indistinguishable from the average surface ocean temperatures observed for the last two decades (1995-2014). This may ultimately imply that the Earth is currently committed to ≥6-9m of equilibrium sea-level rise. Although the LIG is not an analogue for present and future climate change due to the large differences in seasonal orbital insolation and absence of anthropogenic greenhouse gas radiative forcing, it provides an opportunity to test the ability of global climate models to simulate the mechanisms and climate feedbacks responsible for the warmer climate and higher global mean sea level during the LIG. However, when forced only by LIG greenhouse gas concentrations and insolation changes, climate models suggest that the annual mean temperature response was not significantly different from preindustrial control simulations. We present the first multi-model and multiscenario ensemble of transient and equilibrium global climate modeling results spanning the LIG. We show, using a novel model-data comparison framework, that these scenario-specific model results exhibit regionally independent agreement with ocean basin-specific proxy-based SST stacks. This result ultimately implies structural uncertainties and/or misrepresentations of climate feedbacks in the existing suite of climate model simulations, or underestimations of additional proxy-based SST uncertainties. Our conclusions suggest a new target LIG time period for future model-data comparisons and highlight the need for higher resolution transient climate modeling of the LIG and its dependence on meltwater input to the high latitude oceans during the preceding deglaciation. Few discoveries have stimulated the paleoclimate community more so than Heinrich events. Nevertheless, the cause of Heinrich events, characterized by a large flux of icebergs sourced from the Hudson Strait Ice Stream into the North Atlantic, remains debated. Commonly attributed to internal ice-sheet instability, the occurrence of Heinrich events during the coldest intervals of the last glacial cycle instead suggests an external climate control. We expand on recent studies that have shown that incursions of warm subsurface waters into the intermediate depth North Atlantic Ocean destabilized an ice shelf fronting the Hudson Strait Ice Stream, causing a Heinrich event. We present new surface- and bottom-water stable isotope, trace metal, and sedimentary records from two cores taken along the Labrador margin that further support subsurface warming as a trigger of Hudson Strait Heinrich events. We further relate these changes to other sediment core records from the North Atlantic and transient deglacial climate modeling results to show that subsurface warming was ubiquitous across the intermediate North Atlantic during the early part of the last deglaciation and was most likely caused by a preceding reduction in the Atlantic Meridional Overturning Circulation. Title: Ocean Temperature Variability during the Late Pleistocene Author: Hoffman, Jeremy Scott This dissertation explores one overarching question relevant to the paleoclimate of the latest Pleistocene glacial cycle (approximately the last 130,000 years): “How did spatial and temporal evolution of ocean temperature, both at the surface and interior, relate to other parts of the climate system in the late Pleistocene?” Results from three studies are presented that seek to address longstanding questions in paleoceanography and paleoclimatology for the late Pleistocene using a combination of novel and accepted statistical and geochemical analysis techniques and leveraging comparisons with available global climate model data. The last interglaciation (LIG; ~129-116 ka) was the most recent period in Earth’s history with higher-than-present global sea level (≥6-9 m) under similar-to-preindustrial concentrations of atmospheric CO₂. This suggests that additional feedbacks related to albedo, insolation, and ocean overturning circulation may have resulted in the apparent warming required to cause the higher sea level. Our understanding of how much warmer the LIG was relative to the present interglaciation remains uncertain, however, with current estimates suggesting that sea-surface temperatures (SSTs) were 0-2°C warmer than late-20th century average global temperatures. We present a global compilation of proxy-based annual SST spanning the LIG. Using Monte Carlo and Bayesian techniques to propagate uncertainties in age-model and proxy-based SST reconstructions, our results quantify the spatial timing, amplitude, and uncertainty in global and regional SST change during the LIG. Our conclusions suggest that the LIG surface ocean was indistinguishable from the average surface ocean temperatures observed for the last two decades (1995-2014). This may ultimately imply that the Earth is currently committed to ≥6-9m of equilibrium sea-level rise. Although the LIG is not an analogue for present and future climate change due to the large differences in seasonal orbital insolation and absence of anthropogenic greenhouse gas radiative forcing, it provides an opportunity to test the ability of global climate models to simulate the mechanisms and climate feedbacks responsible for the warmer climate and higher global mean sea level during the LIG. However, when forced only by LIG greenhouse gas concentrations and insolation changes, climate models suggest that the annual mean temperature response was not significantly different from preindustrial control simulations. We present the first multi-model and multiscenario ensemble of transient and equilibrium global climate modeling results spanning the LIG. We show, using a novel model-data comparison framework, that these scenario-specific model results exhibit regionally independent agreement with ocean basin-specific proxy-based SST stacks. This result ultimately implies structural uncertainties and/or misrepresentations of climate feedbacks in the existing suite of climate model simulations, or underestimations of additional proxy-based SST uncertainties. Our conclusions suggest a new target LIG time period for future model-data comparisons and highlight the need for higher resolution transient climate modeling of the LIG and its dependence on meltwater input to the high latitude oceans during the preceding deglaciation. Few discoveries have stimulated the paleoclimate community more so than Heinrich events. Nevertheless, the cause of Heinrich events, characterized by a large flux of icebergs sourced from the Hudson Strait Ice Stream into the North Atlantic, remains debated. Commonly attributed to internal ice-sheet instability, the occurrence of Heinrich events during the coldest intervals of the last glacial cycle instead suggests an external climate control. We expand on recent studies that have shown that incursions of warm subsurface waters into the intermediate depth North Atlantic Ocean destabilized an ice shelf fronting the Hudson Strait Ice Stream, causing a Heinrich event. We present new surface- and bottom-water stable isotope, trace metal, and sedimentary records from two cores taken along the Labrador margin that further support subsurface warming as a trigger of Hudson Strait Heinrich events. We further relate these changes to other sediment core records from the North Atlantic and transient deglacial climate modeling results to show that subsurface warming was ubiquitous across the intermediate North Atlantic during the early part of the last deglaciation and was most likely caused by a preceding reduction in the Atlantic Meridional Overturning Circulation. Close

• 8. [Article] Thermistor chain observations during MILDEX

  Citation × Citation Citation Abstract Copy Title: Thermistor chain observations during MILDEX Author: Levine, Murray D., Oregon State University. College of Oceanography, Simpkins, Jay, Gard, Steve R. Title: Thermistor chain observations during MILDEX Author: Levine, Murray D., Oregon State University. College of Oceanography, Simpkins, Jay, Gard, Steve R. Close

• 9. [Article] Foraminiferal assemblages preserved in surface sediments correspond to multiple environmental and preservation variables

  Here we investigate the relationships between modern foraminiferal assemblages from Atlantic and Pacific surface sediment samples and multiple environmental properties including water column and preservation ...

  Citation × Citation Citation Abstract Copy Title: Foraminiferal assemblages preserved in surface sediments correspond to multiple environmental and preservation variables Author: Ross, Ann E. Morey Here we investigate the relationships between modern foraminiferal assemblages from Atlantic and Pacific surface sediment samples and multiple environmental properties including water column and preservation variables using Canonical Correspondence Analysis (CCA). CCA finds two fauna] dimensions that are highly correlated to the environmental variables included in the analysis, and then selects the best linear combination of environmental variables to explain sample positions along these dimensions. The first dimension (30.4% of the faunal variance) is related primarily to mean annual sea-surface temperature (SST, r = -0.955). Salinity, or some property correlated to it, also influences CCA Axis 1 within the tropics. The second dimension (7.9% of the faunal variance) accounts for environmental variability associated with an inverse relationship between SST and surface salinity, including variability in pycnocline phosphate concentration, range in nitrate concentration, water depth and chlorophyll. No evidence is found for a significant influence of selective dissolution, suggesting that carbonate ion concentration cannot be estimated for foraminiferal assemblages Our results support the use of foraminiferal assemblages preserved in deep-sea sediments to estimate SST. We use our results to develop a CCA-based transfer function using the relationship between SST and CCA Axis 1. We tested this new estimation method by reconstructing modern and LGM SSTs, and the SSTs down an eastern tropical Pacific sediment core, RC13-110. Title: Foraminiferal assemblages preserved in surface sediments correspond to multiple environmental and preservation variables Author: Ross, Ann E. Morey Here we investigate the relationships between modern foraminiferal assemblages from Atlantic and Pacific surface sediment samples and multiple environmental properties including water column and preservation variables using Canonical Correspondence Analysis (CCA). CCA finds two fauna] dimensions that are highly correlated to the environmental variables included in the analysis, and then selects the best linear combination of environmental variables to explain sample positions along these dimensions. The first dimension (30.4% of the faunal variance) is related primarily to mean annual sea-surface temperature (SST, r = -0.955). Salinity, or some property correlated to it, also influences CCA Axis 1 within the tropics. The second dimension (7.9% of the faunal variance) accounts for environmental variability associated with an inverse relationship between SST and surface salinity, including variability in pycnocline phosphate concentration, range in nitrate concentration, water depth and chlorophyll. No evidence is found for a significant influence of selective dissolution, suggesting that carbonate ion concentration cannot be estimated for foraminiferal assemblages Our results support the use of foraminiferal assemblages preserved in deep-sea sediments to estimate SST. We use our results to develop a CCA-based transfer function using the relationship between SST and CCA Axis 1. We tested this new estimation method by reconstructing modern and LGM SSTs, and the SSTs down an eastern tropical Pacific sediment core, RC13-110. Close