same type of adjustment was performed for the other observed spectra: the best fits
for parameter r were 40, 45, and 35 m
2 cph in 2007, 2010, and 2012, respectively.
If we compare the levels of the spectra of the Arctic internal waves measured in
1966–1989 and 2007–2012, it is easy to see that there is no trend in the spectral
level (Table 1, Fig. 2). Indeed, because of the causes that are not completely clear
yet, the spectra levels determined on the basis of relatively short measurements in
different years can differ by one order of magnitude even at close geographic
coordinates and under similar meteorological and ice conditions. Bearing this in
mind, however, it can be argued that until 2012 there has been clearly no increase in
the energy of internal waves in the Arctic.
The same conclusion about the absence of a trend in the energy of internal waves
was recently obtained on the basis of another type of measurement [10]. Internal
wave energy was estimated from expendable current probes (XCP) shear variance
and CTD derived buoyancy frequency. A total of 43 vertical profiles of the currents
were used to characterize internal wave energy in April of 2007, 2008, 2010, and
2012, while five vertical profiles were used in the summer of 2007. These data were
compared with 11 profiles measured during the MIZEX 83 experiment in June–July
1983, 20 profiles from the Polarstern 87 cruise in July–August 1987 and 40 profiles
of the AIWEX experiment in March–April 1987. At least one vertical current
profile in 2007, 2010, and 2012 was measured on the same ice floe, on which our
observations of internal waves were performed.
Fig. 6 Spectrum of the
vertical displacement at a
depth of ∼80 m (solid line).
Vertical displacement was
inferred from salinity by
means of dividing by the
current vertical salinity
gradients. The GM spectrum
is shown for comparison
(dashed line). The 95%
confidence limits are
indicated bellow
Internal Wave Frequency Spectrum in the Amundsen Basin …
587
for parameter r were 40, 45, and 35 m
2 cph in 2007, 2010, and 2012, respectively.
If we compare the levels of the spectra of the Arctic internal waves measured in
1966–1989 and 2007–2012, it is easy to see that there is no trend in the spectral
level (Table 1, Fig. 2). Indeed, because of the causes that are not completely clear
yet, the spectra levels determined on the basis of relatively short measurements in
different years can differ by one order of magnitude even at close geographic
coordinates and under similar meteorological and ice conditions. Bearing this in
mind, however, it can be argued that until 2012 there has been clearly no increase in
the energy of internal waves in the Arctic.
The same conclusion about the absence of a trend in the energy of internal waves
was recently obtained on the basis of another type of measurement [10]. Internal
wave energy was estimated from expendable current probes (XCP) shear variance
and CTD derived buoyancy frequency. A total of 43 vertical profiles of the currents
were used to characterize internal wave energy in April of 2007, 2008, 2010, and
2012, while five vertical profiles were used in the summer of 2007. These data were
compared with 11 profiles measured during the MIZEX 83 experiment in June–July
1983, 20 profiles from the Polarstern 87 cruise in July–August 1987 and 40 profiles
of the AIWEX experiment in March–April 1987. At least one vertical current
profile in 2007, 2010, and 2012 was measured on the same ice floe, on which our
observations of internal waves were performed.
Fig. 6 Spectrum of the
vertical displacement at a
depth of ∼80 m (solid line).
Vertical displacement was
inferred from salinity by
means of dividing by the
current vertical salinity
gradients. The GM spectrum
is shown for comparison
(dashed line). The 95%
confidence limits are
indicated bellow
Internal Wave Frequency Spectrum in the Amundsen Basin …
587