130 research outputs found
Oslofjorden 20-23 juni 2011, CTD och spridningshastigheter
No full textVertical profiles of stratification and dissipation rates of turbulent kinetic energy along transects. The data were collected during the period June 20 to June 23, 2011 on board the R/V Trygve Braarud. The wind conditions were relatively calm during the data collection. The maximum measured wind speed at station Gullholmen (59°26.11’N 10°34.68’) was 8.4 m/s. A MSS90L profiler (MSS) was dropped continuously from the stern of the ship as it cruised at low speeds (~1 knot). The MSS90L is a loosely tethered profiler with standard conductivity, temperature and pressure (CTD) sensors as well as two airfoil shear probes (PNS06) sampling at 1024 Hz with 16 bit resolution while the profiler is freely falling through the water with a sinking speed of about 0.6-0.7 m s-1. A more detailed discussion of an earlier version of the instrument can be found in Prandke and Stips (1998). A sensor protecion guard allowd full depth profiles down to 0.1 m above the bottom, with exception of the upper 2-3 meters which were influenced by vessel turbulence and removed. A total of 15 transects were performed; 13 along-fjord transects over the Drøbak Sill and 2 across-fjord transects just inside the sill. Altogether 368 profiles were collected.
Dissipation rates: Dissipation rates of turbulent kinetic energy were obtained from the microstructure shear data using standard methods, as describe in more detail by e.g. Arneborg and Liljebladh (2009). Basically, the shear probes measure how one transverse velocity component changes along the path of the profiler. From the shear variance one can calculate the dissipation rate under the assumption of isotropic turbulence. However, since the sensors do not cover the complete wave-number range of the shear variance, the dissipation rates are obtained by fitting the observed shear spectrum to the universal Nasmyth spectrum for that component. This is done in 50% overlapping 512 point segments, and the resulting estimates of dissipation rate are averaged into 0.5 m bins. In the present case, the main problem with this method is that the velocity of the sensor tip through the water is estimated from the rate of change of the pressure. The velocity through the water enters the calculation of dissipation rates to the power of 4, so small errors in the velocity give considerable errors in the dissipation rate. As discussed in Klymak and Gregg (2004) this may cause large problem in a hydraulic jump where the vertical velocities can be large relative to the sinking velocity of the profiler. As proposed by Klymak and Gregg (2004) we also considered a constant velocity rather than that calculated from the pressure, but found no significant differences in the results. The results presented here are therefore obtained by using the traditional method.
Temperatures: The NTC channel is based on an fp07 fast thermistor, which designed for fast response rather than stability. The TEMPcor channel is based on an Pt100 sensor with better accuracy (+/- 0.01 deg C) but slower response. The raw temperatures are corrected for response time before averaging.
The conductivity sensor is a 7-pole cell with specified accuracy of about +/- 0.05mS/cm.Vertikala profiler för stratifiering och spridningshastigheter av turbulent kinetisk energi längs transekt.
Data samlades in under perioden 20 juni till 23 juni 2011 ombord på fartyget R/V Trygve Braarud. Vindförhållandena var relativt lugna under datainsamlingen.
Mätningar/profileringarna genomfördes med ett turbulensinstrument, MSS90L. Totalt 15 transekter utfördes; 13 längs fjorden och 2 tvärs över fjorden. Totalt insamlades 368 profiler
För mer information se den engelska katalogsidan: https://snd.gu.se/en/catalogue/study/ecds0113
Se beskrivning på engelska
Oslofjorden 20-23 juni 2011, CTD och spridningshastigheter
No full textVertical profiles of stratification and dissipation rates of turbulent kinetic energy along transects. The data were collected during the period June 20 to June 23, 2011 on board the R/V Trygve Braarud. The wind conditions were relatively calm during the data collection. The maximum measured wind speed at station Gullholmen (59°26.11’N 10°34.68’) was 8.4 m/s. A MSS90L profiler (MSS) was dropped continuously from the stern of the ship as it cruised at low speeds (~1 knot). The MSS90L is a loosely tethered profiler with standard conductivity, temperature and pressure (CTD) sensors as well as two airfoil shear probes (PNS06) sampling at 1024 Hz with 16 bit resolution while the profiler is freely falling through the water with a sinking speed of about 0.6-0.7 m s-1. A more detailed discussion of an earlier version of the instrument can be found in Prandke and Stips (1998). A sensor protecion guard allowd full depth profiles down to 0.1 m above the bottom, with exception of the upper 2-3 meters which were influenced by vessel turbulence and removed. A total of 15 transects were performed; 13 along-fjord transects over the Drøbak Sill and 2 across-fjord transects just inside the sill. Altogether 368 profiles were collected. Dissipation rates: Dissipation rates of turbulent kinetic energy were obtained from the microstructure shear data using standard methods, as describe in more detail by e.g. Arneborg and Liljebladh (2009). Basically, the shear probes measure how one transverse velocity component changes along the path of the profiler. From the shear variance one can calculate the dissipation rate under the assumption of isotropic turbulence. However, since the sensors do not cover the complete wave-number range of the shear variance, the dissipation rates are obtained by fitting the observed shear spectrum to the universal Nasmyth spectrum for that component. This is done in 50% overlapping 512 point segments, and the resulting estimates of dissipation rate are averaged into 0.5 m bins. In the present case, the main problem with this method is that the velocity of the sensor tip through the water is estimated from the rate of change of the pressure. The velocity through the water enters the calculation of dissipation rates to the power of 4, so small errors in the velocity give considerable errors in the dissipation rate. As discussed in Klymak and Gregg (2004) this may cause large problem in a hydraulic jump where the vertical velocities can be large relative to the sinking velocity of the profiler. As proposed by Klymak and Gregg (2004) we also considered a constant velocity rather than that calculated from the pressure, but found no significant differences in the results. The results presented here are therefore obtained by using the traditional method. Temperatures: The NTC channel is based on an fp07 fast thermistor, which designed for fast response rather than stability. The TEMPcor channel is based on an Pt100 sensor with better accuracy (+/- 0.01 deg C) but slower response. The raw temperatures are corrected for response time before averaging. The conductivity sensor is a 7-pole cell with specified accuracy of about +/- 0.05mS/cm.Vertikala profiler för stratifiering och spridningshastigheter av turbulent kinetisk energi längs transekt. Data samlades in under perioden 20 juni till 23 juni 2011 ombord på fartyget R/V Trygve Braarud. Vindförhållandena var relativt lugna under datainsamlingen. Mätningar/profileringarna genomfördes med ett turbulensinstrument, MSS90L. Totalt 15 transekter utfördes; 13 längs fjorden och 2 tvärs över fjorden. Totalt insamlades 368 profiler För mer information se den engelska katalogsidan: https://snd.gu.se/en/catalogue/study/ecds0113 Se beskrivning på engelska
The High Arctic "utmark" of the Norse Greenlanders:The Norse Greenlander´s use of High Arctic resources
No full textADCP Kråkefjord 2016
No full text<p>A bottom mounted, upward-looking, RDI Workhose 600 kHz broadband ADCP was deployed in Kråkefjorden at depth 26 m, position (N58.044 E11.485) in the period 2016-08-17 to 2016-10-04. The ADCP was set up with 1 m vertical bins, 5 min ensembles, and 50 pings per ensemble.</p>
<p><strong>Files:</strong></p>
<p>The <strong>KråkefjordADCP.mat</strong> file is a matlab format export of the raw data using the WinADCP software.</p>
<p>The <strong>KråkefjordADCP_proc.mat</strong> file is a matlab format file containing processed data, where the main processing is to estimate the depth of each bin, and remove data before and after the deployment and above the levels influenced by the surface. The variable in this files are:</p>
<p>t: Time in decimal days ince 0000 00:00</p>
<p>z: Vertical coordinate of each bin in m relative to mean surface postion</p>
<p>u: East velocity (m/s)</p>
<p>v: North velocity (m/s)</p>
<p>w: Vertical velocity (m/s)</p>
<p><strong>Funding:</strong></p>
<p><span>The work was partly supported by the European Union Horizon 2020 project JERICO-NEXT (Joint European Research Infrastructure network for Coastal Observatory – Novel European eXpertise for coastal observaTories) grant agreement no. 654410.</span></p>
Temperature and Salinity mooring data from Stigfjorden 2016
No full text<p>A mooring with 5 Seabird SBE37 CT loggers was placed in Stigfjorden on the Swedish west coast at 15 m depth, postition N58.058, E11.565, at 15 m depth, from 2016-08-17 to 2016-10-04. The instruments were set up to log data with 10 min intervals.</p>
<p><strong>Files:</strong></p>
<p>The <strong>RawData.zip</strong> file contains rawdata from the instruments. The nominal depths of the instruments are:</p>
<p>sbe37sm-rs232_03706474_2016_10_04.cnv: 15 m</p>
<p>SBE37SM-RS232_03706473_2016_10_04.cnv: 10.5 m</p>
<p>SBE37SM-RS232_03706373_2016_10_04.cnv: 7 m</p>
<p>SBE37SM-RS232_03706475_2016_10_04.cnv: 5 m</p>
<p>SBE37SM-RS232_03706287_2016_10_04.cnv: 2 m</p>
<p>The <strong>mooring_stig.mat</strong> file is a matlab file that contains processed data in the shape of a struct array DATA with fields:</p>
<p>t: time (Matlab datenum, number of decimal days since January 0, 0000)</p>
<p>T: Temperature (ITS-90, deg. C)</p>
<p>C: Conductivity (S/m)</p>
<p>P: Pressure (db)</p>
<p>S: Practical Salinity (PSU)</p>
<p>Znom: Nominal depth, i.e. approximate depth for constant sea level and vertical mooring line (m)</p>
<p><strong>Funding:</strong></p>
<p><span>The work was partly supported by the European Union Horizon 2020 project JERICO-NEXT (Joint European Research Infrastructure network for Coastal Observatory – Novel European eXpertise for coastal observaTories) grant agreement no. 654410.</span></p>
Temperature and Salinity mooring data from Mollöfjorden 2016
No full text<p>A mooring with 6 Seabird SBE37 CT loggers loggers was placed outside Mållösund on the Swedish west coast, postition N58.044 , E11.429, at 30 m depth, from 2016-08-17 to 2016-10-04. The instruments were set up to log data with 10 min intervals.</p>
<p><strong>Files:</strong></p>
<p>The <strong>RawData.zip</strong> file contains rawdata from the instruments. The nominal depths of the instruments are:</p>
<p>SBE37-IM_03706943_2016_10_04.cnv: 29.5 m</p>
<p>SBE37-IM_03706936_2016_10_04.cnv: 21 m</p>
<p>SBE37-IM_03706942_2016_10_04.cnv: 14.5 m</p>
<p>SBE37-IM_03706937_2016_10_04.cnv: 10 m</p>
<p>SBE37SM-RS232_03706476_2016_10_04.cnv: 7 m</p>
<p>SBE37SM-RS232_03706947_2016_10_04.cnv: 5 m</p>
<p>The <strong>mooring_mollo.mat</strong> file is a matlab file that contains processed data in the shape of a struct array DATA with fields:</p>
<p>t: time (Matlab datenum, number of decimal days since January 0, 0000)</p>
<p>T: Temperature (ITS-90, deg. C)</p>
<p>C: Conductivity (S/m)</p>
<p>P: Pressure (db)</p>
<p>S: Practical Salinity (PSU)</p>
<p>Znom: Nominal depth, i.e. approximate depth for constant sea level and vertical mooring line (m)</p>
<p><strong>Funding:</strong></p>
<p><span>The work was partly supported by the European Union Horizon 2020 project JERICO-NEXT (Joint European Research Infrastructure network for Coastal Observatory – Novel European eXpertise for coastal observaTories) grant agreement no. 654410.</span></p>
Comment on “Influence of sea level rise on the dynamics of salt inflows in the Baltic Sea” by R. Hordoir, L. Axell, U. Löptien, H. Dietze, and I. Kuznetsov
No full text
Turnover times for the water above sill level in Gullmar Fjord
No full textDaily hydrographic measurements between 1954 and 1986, monthly environmental monitoring data from the last decades, and high-resolution data from 2001 are combined to obtain statistics on the exchange of the water above sill level in Gullmar Fjord, Sweden. The analyses show: (i) that the average turnover time is 16-26 days for the water above the halocline (S < 28), and 40 days for the intermediate water below the halocline, (ii) that the exchange is dominated by baroclinic currents caused by vertical fluctuations of the halocline outside the fjord, and (iii) that the statistics for the turnover times are relatively independent of year and season. One implication of these results is that a coupling between climate variations and water quality in Gullmar Fjord, cannot be explained in terms of variations in the water exchange. (C) 2004 Elsevier Ltd. All rights reserved
Förtöjd ADCP- och CTD-data från Oslofjorden
No full textVelocity and CTD data från ADCPs and CT loggers moored at Ristsundet and Aspond in Oslo fjord between 20-23 June 2011. Ristsundet: Position: N59.7215, E10.5702 Water depth: 82 m MicroCat SBE37 CTD loggers at 82, 45, 34, 25 and 14 m depth logging with 5 min intervals. RDI 300 kHz ADCP, upward looking, with two meter bins from 75 to 7 m depth, and 5 min ensemble intervals. Aspond: Position: N59.7243, E10.5813 Water depth: 90 m MicroCat SBE37 CTD loggers at 89, 46, 36, 26 and 16 m depth logging with 5 min intervals. RDI 300 kHz ADCP, upward looking, with two meter bins from 84 to 6 m depth, and 5 min ensemble intervals.Förtöjd ADCP- och CTD-data från Oslofjorden. För mer information se den engelska katalogsidan: https://snd.gu.se/en/catalogue/study/ecds011
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