Current Research
I joined NOAA/AOML in October 2004 and I am currently involved in
several
research projects, including:
-
Studying Deep Western Boundary Current variability and the
associated
impact on climate using long term repeat hydrography, bottom pressure
gauges,
current meters, and inverted echo sounder measurements east of Abaco
Island
in the Bahamas. For more information on this project, please
check this link.
-
Studying the variations in the Florida Current transport
using a retired
undersea cable between Florida and Grand Bahama Island
-
Comparing the Subantarctic Front from data and from a high resolution
numerical model to evaluate the strengths and weaknesses of the model.
-
Reanalyzing the Gulf Stream data set obtained in the SYNOP
experiment
during 1988-1990 using more advanced analysis techniques in order to
get
an improved picture of the Gulf Stream structure and dynamics.
Other
research
projects I have been involved in:
Subantarctic Flux and Dynamics Experiment
(SAFDE)
The SAFDE was a two-year field experiment funded by NSF involving an
array of about 40 instruments moored across the Subantarctic Front
south
of Australia. I worked at the University of Hawaii at Manoa for
just
under two years as a postdoctoral fellow on this project and the goals
of my work were to quantify the structure, transport, and variability
of the Antarctic Circumpolar Current along the Subantarctic Front near
143.5°E. This included descriptions of the stream-coordinates mean
temperature, salinity, and absolute velocity structure of the
Subantarctic
Front as well as quantification of the fluxes both along and across the
front. My supervisor and collaborator on this project was Dr.
Doug
Luther at the University of Hawaii, however Drs. Alan Chave (Woods Hole
Oceanographic Institution) and Randy Watts (University of Rhode Island)
also made important contributions to the work I was doing. The
data
set we used was the array of Inverted Echo Sounders (IES), Horizontal
Electric
Field Recorders (HEFR), and Current Meters (CM) which were moored
across
the Subantarctic Front during 1995-1997. Over this
approximately
two year period nearly 40 moorings were in place measuring vertical
acoustic
round-trip travel times (IES), vertically-averaged horizontal absolute
velocity (HEFR), and point measured temperatures and absolute
velocities
(CM). The SAFDE experiment is described on this
web page. Using historical hydrography from the region
the IES measured travel times can be interpreted in terms of vertical
profiles
of temperature, salinity, and specific volume anomaly; profiles of
specific
volume anomaly can be vertically integrated to provide dynamic height
anomaly
profiles, and then neighboring profiles can be differenced to provide
geostrophic
relative velocity profiles. When combined with the HEFR measured
absolute vertical average horizontal velocities the result is a profile
of absolute velocity over the full water column. The IES and HEFR
moorings in the SAFDE program have provided roughly two years of daily
absolute velocity, temperature, and salinity estimates for a region
spanning
approximately 100 km (zonal) by 200 km (meridional). Four
papers have been published describing the results
of my work on this project; additional papers are in the works from
myself
and several of the other researchers involved in the project as
well. Right now the main thrust of my continuing research in this
area is on a model-data comparison study being done in collaboration
with Dr. Doug Luther (Univ. of Hawaii) and Dr. Mat Maltrud (Los Alamos
National Laboratory).
Tropical Atmosphere and Ocean (TAO) Array
The TAO Array is an ongoing project funded
mainly
by NOAA and consisting of an array of about 70 moorings spanning the
equatorial
Pacific between 8°S and 8°N. I spent a little
over
two years as a postdoctoral researcher working with the Tropical
Atmosphere and Ocean (TAO) Array group at PMEL studying how
the
transports within the equatorial Pacific vary as a result of the El
Nino-Southern
Oscillation cycle. My supervisor and primary collaborator at PMEL
was Dr. Mike McPhaden. Monthly estimates of the geostrophic
transports
(relative to an assumed level of no motion at 1000 dbar) were estimated
using a combination of hydrography and moored temperature measurements
from the TAO array; monthly estimates of Ekman transports also were
determined
using three different wind products. The imbalance between the
variations
of geostrophic and Ekman transports was shown to be the dominant factor
controlling the large variations in warm water volume (T>20°C)
within
the equatorial Pacific. As another part of my work, I quantified
the vertical transports and their variability in the upper water
column,
both the total vertical transport and the component across isotherm
surfaces,
using a box volume technique. Data sources used for the project
included
the
TAO
array, TOPEX/POSEIDON altimetry data; monthly ocean temperature
analyses
from the Bureau of Meteorology Research Centre in Australia; the
Reynolds
SST Climatology; wind and wind pseudo-stress products from Florida
State
University (FSU), the European Community Model (ECMWF), and satellite
scatterometer
winds from a number of satellites (NSCAT, ERS-1, and ERS-2); and a
large
volume of hydrography archived at PMEL. Three papers have been
published
describing the work I did at PMEL. I have also been continuing
work into this area, and have recently (2005) published a paper tracing
the warm water exchanges between the tropics and the higher
latitudes.
North Atlantic Current study
The North Atlantic Current brings warm water
from
the Gulf Stream along the Atlantic coast of Canada up to near Greenland
before it turns east across the Atlantic Basin towards Europe.
During
1993-1995 a line of tall current meter moorings and Inverted Echo
Sounders
additionally equipped with bottom pressure sensors (PIES) spanned the
North
Atlantic Current (NAC) just downstream of the Southeast
Newfoundland
Ridge. I did my Ph.D. study on this data looking at
the
structure
and transports of the NAC. These quantities were studied both from the
line of moored current meters and PIES, and using a hydrographic
section
that included POGO transport floats and Acoustic Doppler Current
Profiler
data. As part of this study I developed a new method for
interpreting
PIES measurements of acoustic round-trip travel time (between the PIES
and the sea surface) to provide full water column profiles of
temperature
and specific volume anomaly using historical hydrography from the
region.
This method, referred to as the "Gravest Empirical Mode" method
or
GEM method, uses hydrography from a limited region around the PIES to
determine
the "mean" profile of temperature, salinity, and specific volume
anomaly
associated with any particular measurement of acoustic round-trip
travel
time. The method also provides natural accuracy estimates by
comparing
the measured values from the hydrography with the "mean" GEM
values.
One of the most important determinations made as part of this study was
that the mean NAC absolute transport, including a portion of the
adjacent
permanent Mann Eddy, was nearly 150 Sv. This value was 2-3 times
larger than most previous estimates of the NAC transport using only
hydrography.
Academic
Background
I graduated with a Ph.D. in oceanography (physical option) from the
Graduate
School of Oceanography,
University of
Rhode Island in the spring of 1998. My advisor was Dr. Randy
Watts.
After finishing my Ph.D. in Rhode Island I spent a little over two
years
as a postdoctoral researcher at the Joint Institute for the Study of
the
Atmosphere and Ocean, University of Washington. My primary
supervisor
was Dr. Mike McPhaden at NOAA/PMEL. I left Washington in the
summer
of 2000 and moved to take a postdoctoral fellowship at the University
of
Hawaii at Manoa. My supervisor in Hawaii was Dr. Doug
Luther.
In the summer of 2002 I moved to Miami to take up a position at the
Cooperative
Institute for Marine and Atmospheric Studies at the University of
Miami,
and in October 2004 I moved into my current position at AOML.
Contact
information
Dr. Christopher Meinen
NOAA/AOML/PHOD
4301 Rickenbacker Causeway
Miami, FL 33149
Office Ph# (305)361-4355
Office Fax# (305)361-4412
email:
Christopher.Meinen @ noaa.gov
