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Available nitrogen and phosphorus and the biochemical cycle in the Atlantic off New England
642
Oceanographic Abstracts
absorption in this region of the spectrum, and that changes in concentration can be described by Beer's law. It has been demonstrated that the spacelight within Pacific coastal water also exhibits absorption bands, and there appears to be no reason why this spectrum together with Beer's law cannot be used as in the freshwater case, for describing and predicting chlorophyll concentrations in the ocean. Differences in the spacolight spectra between the freshwater and coastal water have been noted, and it is suggested that differences of this kind may make it possible to identify some species of phytoplankton in situ by comparison of output/input ratios. UNTERSTEINER N., 1964. Calculations of temperature regime and heat budget of sea ice in the central Arctic. J. Geophys. Res., 69 (22): 4755-4766. The equation of heat conduction, including variable thermal conductivity and specific heat, an internal heat source diminishing with depth, and an advective term, is integrated numerically for sea ice of equilibrium thickness. The annual cycle of thickness (ablation-accretion~ is imposed as an external parameter. The boundary values for temperature and the vertical distribution of ice salinity are taken from empirical data. Thd computed temperature field is in good agreement with observations. The thermal history of individual particles of ice, the relative effect of the internal heat source (penetrating solar radiation), heat storage, and the annual cycle of heat flux by conduction at various depths are described. The observed maximum of brine volume at 40- to 70-cm depth is explained as the combined effect of salinity profile and internal absorption of radiation. The requirement that heat flux in the ice plus the heat equivalent of surface ablation equal the heat flux in the atmospheric boundary layer is well met by Badgley's values of radiative and turbulent heat transfer. During the melting season, 15 June to 20 August, the surface of the ice receives about 4'5 kcal/cmZ and loses, during the freezing season, 21 August to 14 June, an only slightly greater amount of heat to the atmosphere. The annual sum of heat conduction at the base of the ice is 3"6 kcal/cm 2. Of this, 2.0 kcal/cmZ originates from ice accretion and 1.6 kcal/cm z is drawn from the ocean. The atmosphere over the central Arctic receives an annual total of 2"5 kcal/cm 2, which is mainly the heat of fusion of exported ice. URICK R. J., 1963. Low frequency sound attenuation in the deep ocean, d. Acoust. Soc. Amer., 35 (9): 1413-1422. Signals received from Solar bombs dropped from an airctaft eastward from Bermuda have been studied quantitatively. The energy density of the signals received at Bermuda, measured in various bands between 20 and 1600 c/s, can be accounted for by cylindrical spreading beyond a ' transition r a n g e ' predicted approximately by simple considerations, plus an attenuation coefficient in db/Myd given by the linear expression 1'5 ÷ 8.2f, w h e r e / i s the frequency in kc/s. At frequencies below I kc/s, this attenuation is far in excess of that which would be produced by absorption alone. At very low frequencies the excess attenuation is postulated to be due to the failure of the Sofar sound channel to act as an acoustic trap. At frequencies from about 50 to 500 c/s, quantitative evidence is presented to indicate that the dominant attenuation process is scattering by index-of-refraction inhomogeneties deep in the sea. Other characteristics of Sofar-transmitted signals are described. VACCARO R. F., 1963. Available nitrogen and phosphorus and the biochemical cycle in the Atlantic off New England. J. Mar. Res., 21 (3): 284-301. The importance of ammonia as a source of available nitrogen for phytoplanktonic populations off New England has been evaluated for August and January 1962. During August, when only trace amounts of nitrate persist in the photic layer, ammonia appears to be the major source of available nitrogen. Therefore, meaningful estimates of the relative amounts of nitrogen and phosphorus being assimilated at such times require consideration of the nitrogen occurring as ammonia. Total available nitrogen : phosphorus ratios of change have been derived from the sum of the nitrogen occurring as ammonia, nitrite, and nitrate and from the concentration of phosphate. These ratios have been compared with other data (for August and April) based on the organic nitrogen and phosphorus content of particulate fractions separated from suspension by Millipore® filtration and by net tows. The results indicate that the ratios of change for August are somewhat lower than those for January and that the former are accompanied by a comparable depression in the N : P ratios for particulate material separated by Millipore® filtration. It is speculated that during late summer, when nitrate and nitrite concentrations are minimal, ammonia forestalls the extreme degree of nitrogen deficiency known for laboratory cultures of nitrogen-starved algal cells. VAN ANDEL TJEERD H., 1964. Recent sediments of Gulf of California. In: Marine geology' of the Gulf o f California, a symposium, Amer. Ass. Petrol. Geol., Memoir, (Edited by VAN ANDEL T. and GEORGE G. SHOR JR.), 3: 216-310. The Gulf of California is a long, narrow basin which is almost completely separated from the Pacific Ocean by the mountainous Peninsula of Baja California and bordered on the east by a coastal plain and the Sierra Madre Occidental of Mexico. The northern Gulf, with the exception of the deep Sal si Puedes Basin, is at shelf depth and receives sediment mainly from the Colorado River. Modern deposition is restricted to the vicinity of the Colorado River delta, to areas of sandy littoral sediments fringing the margins, and to somewhat diatomaceous clays in the deepest basin. Over
Oceanographic Abstracts
absorption in this region of the spectrum, and that changes in concentration can be described by Beer's law. It has been demonstrated that the spacelight within Pacific coastal water also exhibits absorption bands, and there appears to be no reason why this spectrum together with Beer's law cannot be used as in the freshwater case, for describing and predicting chlorophyll concentrations in the ocean. Differences in the spacolight spectra between the freshwater and coastal water have been noted, and it is suggested that differences of this kind may make it possible to identify some species of phytoplankton in situ by comparison of output/input ratios. UNTERSTEINER N., 1964. Calculations of temperature regime and heat budget of sea ice in the central Arctic. J. Geophys. Res., 69 (22): 4755-4766. The equation of heat conduction, including variable thermal conductivity and specific heat, an internal heat source diminishing with depth, and an advective term, is integrated numerically for sea ice of equilibrium thickness. The annual cycle of thickness (ablation-accretion~ is imposed as an external parameter. The boundary values for temperature and the vertical distribution of ice salinity are taken from empirical data. Thd computed temperature field is in good agreement with observations. The thermal history of individual particles of ice, the relative effect of the internal heat source (penetrating solar radiation), heat storage, and the annual cycle of heat flux by conduction at various depths are described. The observed maximum of brine volume at 40- to 70-cm depth is explained as the combined effect of salinity profile and internal absorption of radiation. The requirement that heat flux in the ice plus the heat equivalent of surface ablation equal the heat flux in the atmospheric boundary layer is well met by Badgley's values of radiative and turbulent heat transfer. During the melting season, 15 June to 20 August, the surface of the ice receives about 4'5 kcal/cmZ and loses, during the freezing season, 21 August to 14 June, an only slightly greater amount of heat to the atmosphere. The annual sum of heat conduction at the base of the ice is 3"6 kcal/cm 2. Of this, 2.0 kcal/cmZ originates from ice accretion and 1.6 kcal/cm z is drawn from the ocean. The atmosphere over the central Arctic receives an annual total of 2"5 kcal/cm 2, which is mainly the heat of fusion of exported ice. URICK R. J., 1963. Low frequency sound attenuation in the deep ocean, d. Acoust. Soc. Amer., 35 (9): 1413-1422. Signals received from Solar bombs dropped from an airctaft eastward from Bermuda have been studied quantitatively. The energy density of the signals received at Bermuda, measured in various bands between 20 and 1600 c/s, can be accounted for by cylindrical spreading beyond a ' transition r a n g e ' predicted approximately by simple considerations, plus an attenuation coefficient in db/Myd given by the linear expression 1'5 ÷ 8.2f, w h e r e / i s the frequency in kc/s. At frequencies below I kc/s, this attenuation is far in excess of that which would be produced by absorption alone. At very low frequencies the excess attenuation is postulated to be due to the failure of the Sofar sound channel to act as an acoustic trap. At frequencies from about 50 to 500 c/s, quantitative evidence is presented to indicate that the dominant attenuation process is scattering by index-of-refraction inhomogeneties deep in the sea. Other characteristics of Sofar-transmitted signals are described. VACCARO R. F., 1963. Available nitrogen and phosphorus and the biochemical cycle in the Atlantic off New England. J. Mar. Res., 21 (3): 284-301. The importance of ammonia as a source of available nitrogen for phytoplanktonic populations off New England has been evaluated for August and January 1962. During August, when only trace amounts of nitrate persist in the photic layer, ammonia appears to be the major source of available nitrogen. Therefore, meaningful estimates of the relative amounts of nitrogen and phosphorus being assimilated at such times require consideration of the nitrogen occurring as ammonia. Total available nitrogen : phosphorus ratios of change have been derived from the sum of the nitrogen occurring as ammonia, nitrite, and nitrate and from the concentration of phosphate. These ratios have been compared with other data (for August and April) based on the organic nitrogen and phosphorus content of particulate fractions separated from suspension by Millipore® filtration and by net tows. The results indicate that the ratios of change for August are somewhat lower than those for January and that the former are accompanied by a comparable depression in the N : P ratios for particulate material separated by Millipore® filtration. It is speculated that during late summer, when nitrate and nitrite concentrations are minimal, ammonia forestalls the extreme degree of nitrogen deficiency known for laboratory cultures of nitrogen-starved algal cells. VAN ANDEL TJEERD H., 1964. Recent sediments of Gulf of California. In: Marine geology' of the Gulf o f California, a symposium, Amer. Ass. Petrol. Geol., Memoir, (Edited by VAN ANDEL T. and GEORGE G. SHOR JR.), 3: 216-310. The Gulf of California is a long, narrow basin which is almost completely separated from the Pacific Ocean by the mountainous Peninsula of Baja California and bordered on the east by a coastal plain and the Sierra Madre Occidental of Mexico. The northern Gulf, with the exception of the deep Sal si Puedes Basin, is at shelf depth and receives sediment mainly from the Colorado River. Modern deposition is restricted to the vicinity of the Colorado River delta, to areas of sandy littoral sediments fringing the margins, and to somewhat diatomaceous clays in the deepest basin. Over