110 likes | 228 Views
Ellesmere Island coast in Kennedy Channel, Aug.-12, 2009. Velocity: Long-Range Sonars. Sonars send and receives acoustic waves Measured Doppler shift proportional to velocity 75 kHz transducers. Rigid Backbone allowed to Pitch and Roll, but NOT Change Heading.
E N D
Velocity:Long-Range Sonars • Sonars send and receives acoustic waves • Measured Doppler shift proportional to velocity • 75 kHz transducers Rigid Backbone allowed to Pitch and Roll, but NOT Change Heading Magnetic Compass unusuable: Kennedy Channel ~2800 nT Fram Strait ~ 5800 nT magnetic field strength
Semi-diurnal band Diurnal band All frequencies High-resolution Power-spectra of Depth-averaged Flow at KS10
Mean Along-Channel Velocity (cm/s) Along-Channel Freshwater Flux (mSv per km per meter rel. to 34.8) Along-Channel velocity fluctuations (cm/s)
Three-year along-channel currents from ADCP mooring (KS02) 2003/04 Depth (m) 2004/05 2005/06
10 Days Spectral Density (cm/s)^2 per cpd Winter (Landfast Ice) Summer (Mobile Ice)
Selection of Time Scale: Cumulative Variance by time scale (1/frequency) Cumulative Variance by frequency Spectral Density Volume Flux Spectral Density Along-Channel Sealevel Difference Chosen Cut-Off
Filter Design Cut-Off: ~20 Days Good Filter: Lanczos Raised Cosine Bad Filter: Running Average
Residual root mean square: 0.19 Sv Correlation: r2=0.71 Regression: a= -0.84 Sv Regression b=8.54 Sv/m
2-D Power-Spectrum (dispersion curves?) [Time Scale] From: Max-Planch Institute Solar Systems Research [Space Scale] http://www.mps.mpg.de/projects/seismo/NA4/SW/power_spectrum.html