Scientific Reports
Scientific Reports
>Received: by revelle.UCSD.EDU (SMI-8.6/UCSDUUCPGENERIC.4)
id SAA06609 to ; Thu, 26 Oct 2000 18:30:08 GMT
Date: Thu, 26 Oct 2000 18:30:08 GMT
From: revelle!jacobson@sdsioa.ucsd.edu (Dan Jacobson)
To: shipsked@ucsd.edu
Subject: Revelle NECR04 Science Report
Cc: jacobson@sdsioa.ucsd.edu, master@sdsioa.ucsd.edu, mgregg@sdsioa.ucsd.edu,
scg@sdsioa.ucsd.edu
The science report from Chief Scientist Mike Gregg.
Dan
From mgregg@revelle Thu Oct 26 06:58 GMT 2000
Date: Thu, 26 Oct 2000 06:58:59 +0000 (GMT)
From: "M. Gregg - NECR04" <mgregg@revelle>
Subject: weekly report
After finishing our stations at Nihoa we moved to the Kauai Channel
and began by running sections across the Kaena Point ridge, close to
shore where depths were as shallow as 300 m. Difficult to work there
owing to strong jet along ridge, but we observed displacements of
isotherms with the tidal cycle, one showing a wave with the width of
the ridge as the half-wavelength. Strong turbulence over the ridge
which decayed to the south in nearly the same manner as observed at
Nihoa and French Frigate Shoals. One more station in channel
tomorrow, in zone predicted to be free of M2 waves from ridge. Then
will spend a few days observing sections close to shore at Barber's
Point and Mamala Bay. Our objective is to examine the structure of a
trapped internal tide tentatively described several years ago by Peter
Hamilton of SAIC. Will finish with time series over Penguin Bank, off
Molokai. Bottom boundary there is predicted to produce all BBL
dissipation for entire Hawaiian Ridge.
The crew and facilities on Revelle have been a dream to work with --
hats off to them and the sio marfac.
Mike Gregg
>Received: by revelle.UCSD.EDU (SMI-8.6/UCSDUUCPGENERIC.4)
id SAA13477 to ; Thu, 19 Oct 2000 18:10:35 GMT
Date: Thu, 19 Oct 2000 18:10:35 GMT
From: revelle!jacobson@sdsioa.ucsd.edu (Dan Jacobson)
To: shipsked@ucsd.edu
Subject: Science Report NECR04
Cc: jacobson@sdsioa.ucsd.edu, master@sdsioa.ucsd.edu, mgregg@sdsioa.ucsd.edu,
scg@sdsioa.ucsd.edu
>From mgregg@revelle Thu Oct 19 10:07 GMT 2000
Date: Thu, 19 Oct 2000 10:07:07 +0000 (GMT)
From: "M. Gregg - NECR04" <mgregg@revelle>
Subject: another week
To: jacobson@revelle
Cc: sherman@apl.washington.edu
...
We occupied the French Frigate Shoals stations a second time,
near sprint tides this time, but did not find large increases in the
mixing compared to our earlier occupations, near neap tides. After
finishing them we moved to a site west of Nihoa, which Merrifield and
Holliway predict to be the third source of internal tides on the
ridge. We are doing 3 stations, each for about 25 hours. One
consisted of repeated lines coming over the steep slope onto the
crest. We found intense and highly sheared flows below the crest
which produced an average diapycnal diffusivity of 10^-2 m^2/s over a
section 100 m thick. It appeared to turn on when predicted surface
tides were southward over the ridge crest. Having just finished a
second station 25 nm south of the ridge, we are proceeding to a third
station 50 nm south of the ridge.
Mike Gregg
>Received: by revelle.UCSD.EDU (SMI-8.6/UCSDUUCPGENERIC.4)
id EAA26128 to ; Fri, 13 Oct 2000 04:54:03 GMT
Date: Fri, 13 Oct 2000 04:54:03 GMT
From: revelle!jacobson@sdsioa.ucsd.edu (Dan Jacobson)
To: shipsked@ucsd.edu
Subject: NECR04RV Weekly report #2
Cc: jacobson@sdsioa.ucsd.edu, master@sdsioa.ucsd.edu, mgregg@sdsioa.ucsd.edu,
scg@sdsioa.ucsd.edu
Below is the second weekly science report from chief scientist Mike
Gregg on NECR04RV.
Dan
After leaving Honolulu a week ago, we proceeded directly out the
Hawaiian Ridge to French Frigate Shoals and chose four sites to sample
microstructure and shear. We have occupied all stations once, each
for 25 hours, two cycles of the twice-daily tide. The stations are:
on the Ridge crest, over it's southern flank, 15 nm offshore, and 50
nm offshore. Strong trade winds are limiting our sampling to the
upper 800 m much of the time.
Mixing within 15 nm of the Ridge is 10-100 times open ocean background
levels throughout most of the upper 800, with the larger levels near
the bottoms of our profiles. Consistent with the elevated mixing,
strain spectra are also well above GM76 near the ridge, but relax to
it at the station 50 miles from the crest. Shear spectra are also
elevated, but do not seem to decay offshore, so we are studying them
carefully.
After 2 and a half more days here, we will head for Nihoa, to occupy
some stations where barotropic-to-baroclinic conversion is not
predicted to be strong.
Mike Gregg
>Received: by revelle.UCSD.EDU (SMI-8.6/UCSDUUCPGENERIC.4)
id AAA03546 to ; Fri, 6 Oct 2000 00:36:36 GMT
Date: Fri, 6 Oct 2000 00:36:36 GMT
From: revelle!jacobson@sdsioa.ucsd.edu (Dan Jacobson)
To: shipsked@sdsioa.ucsd.edu
Subject: NECR04 science report 1
Cc: jacobson@sdsioa.ucsd.edu, master@sdsioa.ucsd.edu, mgregg@sdsioa.ucsd.edu,
scg@sdsioa.ucsd.edu
Here is the first science report from Mike Gregg, chief scientist on
NEMO04RV.
Dan
SCG
>From mgregg@revelle Thu Oct 5 23:28 GMT 2000
Date: Thu, 5 Oct 2000 23:28:12 +0000 (GMT)
From: "M. Gregg - NECR04" <mgregg@revelle>
Subject: cruise report
To: jacobson@revelle
After leaving Honolulu at 1730, the Revelle headed for French Frigate
Shoals. We plan to work there for about 8 days, spanning neap to
spring tides. Numerical simulations by Merrifield et al. show the
largest fluxes of M2 internal tides emanating from the shoals. We
will take day-long stations over the ridge crest, the slope and
offshore to the south to examine how much dissipation accompanies the
elevated shear and displacements observed last month by Rudnick and
Pinkel. Tom Sanford on Wecoma will join us several days after we
arrive.
We stopped this morning to test our microstructure profilers and will
make several more stops for further testing today and tomorrow.
Mike Gregg
This cruise is being funded by a grant from the National Science Foundation.
Email:
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