Global
Studies:
AOML is conducting climate studies with global
scope in order to better understand the global
setting for regional signals, and how the regional
signals contribute to global phenomena. Even
strongly regional phenomena such as El Niņo-Southern
Oscillation (ENSO) have clear and important
expressions in the Atlantic and Indian Oceans.
Other signals previously thought to be regional,
such as the North Atlantic Oscillation (NAO),
are linked to the opposite side of the Northern
Hemisphere through polar vortex fluctuations.
The role of the ocean in the control and modulation
of compounds influencing climate (carbon dioxide
[CO2], water) or ozone levels (methyl
bromide [CH3Br], CO) requires both
assessment of surface fluxes and changes in
inventories over time. Analysis of sensitivity
of the relevant fluxes to seasonal and interannual
variability in hydrographic properties is critical
to make future projections of atmospheric changes
of chemical species. Finally, the evolution
of a global observation system to support these
and other such studies, and operational climate
prediction, requires the active participation
of research entities such as AOML in partnership
with operational centers such as NOAA/National
Center for Environmental Prediction (NCEP).
The AOML-based Global Ocean Observing System
(GOOS) Center achieves this by assuring efficient
acquisition and quality control of real-time
data, and by developing and implementing new
technologies for operational use.
Physical
climate studies:
Using data diagnostics, we have statistically
separated and indexed global climate signals
such as ENSO and the NAO (Figure
2). We have found that within the equatorial
Pacific region called NINO3, the interannual,
global ENSO signal can be discriminated from
the mainly interdecadal "non-ENSO" component
(Figure 3). When
these components are separately projected onto
the global atmospheric variability (NCEP reanalysis),
surprising differences can be seen in the Walker
and Hadley circulation anomalies as they relate
to the ENSO and non-ENSO variability (Figure
4). The decadal to multidecadal (D2M) variability
in the NINO3 region has anomalous Walker and
Hadley associations (in the troposphere) that
are nearly opposite to those of ENSO, over the
global tropics. This raises some transcendental
questions for future research regarding the
relationships between ENSO and D2M, and suggests
that the predictabilities emanating from ENSO
and D2M must be considered separately and combined
with care. In newly proposed work, we hope to
combine modeling and data diagnostics in an
attempt to see how the Atlantic sector is affected
by, and feeds back on, such distinct climate
modes. Why is the tropical North Atlantic variability
quasi-independent of the tropical South Atlantic
variability (non-dipole)? Does this follow from
separate forcings by larger scale, independent
tropospheric modes of variability? How is the
tropospheric direct circulation altered in each
case and how are those patterns related to known
phenomena such as the NAO?
Global
atmospheric chemistry and carbon cycle:
Research on the global ocean carbon cycle has
been collaborative work in estimating the anthropogenic
carbon inventory based on hydrographic observations
during the global CO2 survey sponsored by NOAA
and the Department of Energy, and air-sea CO2
fluxes from observations of surface water pCO2
on NOAA research ships. The high quality data,
together with innovative methods to correct
historical data, has led to robust estimates
of the penetration of anthropogenic carbon into
the ocean (Figure
5, from Peng et al., 1998, Nature, 396,
560-563). This figure shows change between the
surveys of 1978 and 1995 in the Indian Ocean
at latitudes south of about 15°S. These methods
are now being applied to make global anthropogenic
carbon inventory estimates. To gain better understanding
of shorter-term variations in air-sea CO2 fluxes,
we've instituted an active program of measurements
of pCO2 on ships and contributed to the first
global monthly climatology of air-sea CO2 fluxes.
The climatology was subsequently used to estimate
the interannual variability in air-sea fluxes,
suggesting significantly smaller year-to-year
changes than from atmospheric inference. This
issue of variability and trends is of importance
to determine the controls of carbon sequestration
by the ocean. A new technique has been developed
to measure trace level nutrients in oligotrophic
waters, and the new production can be estimated
based on the diel cycle of nitrate in the euphotic
zone on diurnal time scales.
The
atmospheric chemistry effort at AOML has included
an effort to measure and characterize the reactive
nitrogen oxide gases in the marine environment.
These gases play a critical role in the control
of ozone formation in the troposphere, and their
source/sink and concentration distributions
are a critical input for global tropospheric
chemical models. Recent field programs include
the pre-Indian Ocean Experiment (INDOEX) and
INDOEX cruises aboard the NOAA ships Malcolm
Baldrige and Ronald H. Brown in 1995 and 1999,
respectively. Results obtained in the former
cruise have been incorporated into a photochemical
box model which indicated the unexpected role
of halogens (BrO, HOBr, HBr) in constraining
the budget of ozone in the remote marine boundary
layer. Preliminary results from the 1999 INDOEX
cruise (http://www-indoex/ucsd.edu)
showed a significant impact of air pollutants
in this region.
Atmospheric
methyl bromide (CH3Br), which is of both natural
and anthropogenic origin, has been identified
as a Class I ozone-depleting substance in the
amended and adjusted Montreal Protocol on Substances
that Deplete Stratospheric Ozone. With the role
of the ocean in regulating the atmospheric burden
of this and other halocarbons still uncertain,
recent field, laboratory, and modeling studies
conducted in collaboration with investigators
from the Climate Monitoring and Diagnostics
Laboratory (CMDL) and universities have been
designed to help improve our understanding of
this role (Figure
6). We are improving our understanding of
how biological as well as chemical processes
are important in the assessment of the ocean's
ability to regulate atmospheric CH3Br and other
halocarbons (POC11).
In
1995-1996, the biological oceanography group
at AOML led an Arabian Sea expedition under
the aegis of Global Ecosystem Dynamics and Coupling
(GLOBEC), one of the National Science Foundation's
Global Climate Change programs. Using a range
of acoustic frequencies, fish and zooplankton
signals were distinguished, permitting rigorous
quantitative analysis of the effect of monsoonal
upwelling upon plankton biomass. Recent investigations
of local upwelling and current structure have
focused upon the relationship between temperature
and local production processes and have highlighted
eddy processes and local topographic effects
(http://www.aoml.noaa.gov/ocd/globec).
Future
AOML research will support the objectives of
national and international research programs.
In particular, we will contribute to the objectives
of the Carbon Cycle Science Plan and the Surface
Ocean Lower Atmosphere Study (SOLAS) through
continued examination of the role that the ocean
plays in regulating climatically important trace
gases. Improved surface trace gas flux estimates
requires expanded monitoring of surface water
pCO2 and halocarbon saturations, improved methods
of interpolation, and better parameterization
of air-sea gas fluxes. Understanding the processes
controlling the surface water trace gas concentrations,
such as improved understanding of nutrient dynamics,
vertical diffusion, biological productivity,
and biological degradation, are high priorities.
NOAA
Global Ocean Observing System (GOOS) Center:
NOAA is developing a new paradigm for operational
oceanography by placing operational activities
within research laboratories. A study using
data provided by the global expendable bathythermograph
(XBT) network illustrates how the synergy between
operations and research functions (NOAA collects
approximately 50% of the total global XBT profiles).
Analysis such as the space-time diagram of subsurface
temperature (Figure
7) was used to determine which transects
should be continued until a global profiling
float array is deployed (an operational goal)
and continues to be used to study decadal signals
in the ocean and possible interactions with
atmospheric climate (a research goal).
The
GOOS Center incorporates the activities of the
Global Drifter Program, which provides leadership
and services from instrument procurement to
data delivery for the global drifter array (GDA)
of about 800 surface drifters. Sea surface temperature
(SST) observations from the GDA are essential
for creating SST analyses which are used in
the initialization of National Center for Environmental
Prediction (NCEP) ENSO predictions. Winds and
sea-level pressures from the GDA are increasingly
used for marine, regional, and global forecasts.
Surface currents from the GDA are used in ocean
global circulation models verification and in
climate research. Products from the Global Drifter
Program include a surface current climatology
for the tropical Pacific Ocean for ENSO studies.
Higher resolution surface current climatologies
are in the works for the California Current
and the world for oil spill mitigation efforts
by the Minerals Management Service and for search
and rescue operations of the Coast Guard.
The
GOOS Center is working to improve the use of
data in ocean models for predicting seasonal-to-interannual
climatic variability. Recent research has led
to a widespread realization that ocean models
can be greatly improved with the addition of
salinity-depth information. In the absence of
an adequate observing system for salinity, it
is necessary to leverage other types of data.
In and below the thermocline, temperature-salinity
correlations can be used to exploit XBT data.
Near the surface, sea surface salinity could
be monitored inexpensively. Additional information
is available from satellite altimetric inferences
of dynamic height. Our examination of NCEP's
model-based reanalysis has revealed that the
salinity of the equatorial undercurrent is generally
too fresh, a fact that might be attributable
to the treatment of the Indonesian throughflow.
A related activity is our National Oceanographic
Partnership Program collaboration (AOML, University
of Miami, Los Alamos National Laboratory, Naval
Research Laboratory) for assimilating data into
HYCOM, a model that is distinctly different
from that used by NCEP, to produce an alternative
30-year reanalysis.
Future
GOOS Center activities will include: (1) continued
evaluation of the XBT network and identification
of important climate signals; (2) new World-Wide
Web products using the GOOS Center data to market
the data and to monitor the state of the upper
ocean; and (3) increased interactions with NCEP
to improve data management methodology, efficacy
of the observing network, and the forecast models.