Transcript Slide 1

THE PROBLEM OF STUDYING THE
PROBLEM OF THE OCEAN IN
CLIMATE
Carl Wunsch
Ocean Sciences Meeting, Orlando
March 2008
We have collectively moved from an era in
which the ocean was generally regarded as
nearly unchanging over decades to one in
which the emphasis is on its changes.
Further shifted from delineating high frequency
phenomena such as internal waves and
mesoscale eddies to a focus on interannual,
decadal, and longer period shifts.
Our infrastructure, and to a large degree,
human society, are poorly structured to deal
with multi-decadal and longer time scales (an
inter-generational problem).
Example of an oceanographic
study. Curry & McCartney,
2001.
Phenomenological time
scales match or exceed the
data duration
The system is very noisy and it is a truism of science that one must
observe phenomena so as to clearly delineate the time scales of
change and of energy. Thus multi-decadal and longer observations
are required and there is no escaping the conclusion. No one would
advocate the study of one-second period surface waves for only a few
seconds. That is what we are doing with decadal ocean variability….
Note the extreme spatial
variability. Dynamics
tells us different regions
behave differently.
Anomaly of surface elevation, Jan 2005, ±25cm
A year of current meter data, day-by-day from a quiet
part of the ocean Sargasso Sea, 37N, 42W. How many
years to get stable statistics?
Cazenave and Nerem, 2004, trends in mean
sea level, 13 years, mm/y. Mean of 2.8mm/y
removed. Such patterns have very serious
societal consequences.
Cessi et al., 2004. Theory all implies the same problem:
Example:
Time in years for a North Atlantic disturbance to
penetrate the world ocean (sea level). Many decades
are required for its evolution and many more required to
fully observe it.
Can one possibly understand this
Without understanding this?
Character of the motions is position dependent.
Hogg & Owens, DSR, 1999
A lot of physics lies between these observed
motions---requiring years of study---and the Wüstian
arrows (which have only direction).
Nansen bottles/reversing
thermometers about 1860-1965
STD/CTD about 1965present
Maintaining calibration
over decades is one of
the most difficult of all
technical problems, as are
decisions concerning
technology replacement.
SeaOs about 2003-present
What’s next?
All the science says that observations
must be:
(1) Global
(2) Time continuous
(3) Of open-ended duration
(4) Continuously calibrated
(5) Continuously evaluated for scientific
benefit
Open ended, or operational, systems face major challenges.
(1) Sustained calibration need
(2) Obsolescence of the technology is inexorable
(3) Apparently higher priority, short-term budget requirements always appear.
(4) Low frequency signals require great patience
(5) Technicians, who are not the end-users of the data, have a hard time
maintaining continuity and quality control
(6) Sometimes the observations, when better understood, are no longer
regarded as high priority and one might best be discontinued---the
possibility has always to be considered, but a threat to jobs and careers.
(7) Satellite systems also need to be maintained, to sample often enough
(enough instruments to avoid serious aliasing ), global spatial coverage.
And that technology also evolves. Need overlaps and calibration. A
complicated scientific problem in its own right.
(8) A powerful tendency (witness US and UK obsession with the North Atlantic)
for scientists to focus on regions. But climate is global and omission of
major regions of observation will drastically curtail future understanding.
How do you do this?
None of this is easily consistent with academic or other time
scales. It becomes a scientific-engineering-societal
commitment.
Is there some way to do this, or is it beyond the capacity of human
society?
Usual initial reaction is to point at the meteorological experience--a short-term set of problems leading to long-term records.
Unhappily, the parallel is nither apt nor encouraging:
severe difficulties with calibration. Focus on short-term
forecasting as opposed to estimation of the state.
Oceanographic and general climate variations over years,
generally without ongoing constituencies to sustain the
observation systems.
Example of the Difficulty: The Bermuda Observatory of Henry
Stommel
Tide gauge in Ferry Reach (Bermuda Biological Station)
Cable down island slope to measure temperature and
bottom pressure (and plug in any new instrument as
available)
Radio tracking of surface drifters
Hydrographic station (Panulirus Station →Station S)
Only the hydrographic station continues. Stommel
himself abandoned the observatory idea within a few
years.
Hydrography was/is subject to aliasing, bad weather, ship
breakdowns, equipment loss, quality control problems.
Cable connections were hard to maintain. On-the-bottom-of-aslope temperatures on a large island require considerable theory
to interpret.
Drifter measurements proved uninterpretable (“…false mean flows
from …rectification. They repose in published obscurity.” H.
Stommel, Autobiography. They didn’t know about the eddy-field.)
Tide gauge was reliable only during the lifetime of Colonel
Stevens for whom it was a retirement hobby. After take-over by
NOAA, record was soon interrupted.
Center of the Sargasso Sea is not representative at low
frequencies of the ocean as a whole (or at least it is not obviously
so).
It’s noisy. Broken up, aliased and hard to use.
A crisis every 3-5 years when funding came up
for renewal: “You have 10 years of data; isn’t
that sufficient?”.
Global coverage by moored current meters over full
water column, circa 1975-1995. Incoherent. Not
cheap. Patience was required. Probably none is
still in maintained.
Now operational “observatory”. Upper ocean
coverage only---great missed opportunity. Is
the science community truly engaged?
All the science points to the conclusion that
our generation(s) will have inadequate
data to “solve” the ocean-in-climate
problem. Unpalatable, but how to escape
the inference?
If the inference is accepted, our problem
then becomes one of laying the foundation
for some future generation to have
adequate data. (There are parallel issues
concerning climate model development
and testing that I am omitting here.)
How does one sustain open-ended measurements and
model scrutiny when the result will be of greatest
interest to future generations? Existing infrastructure is
grossly inadequate to that end. One needs a multidecadal, century, open-ended, view.
A few organizations persist for hundreds to order 1000
years, although the true continuity of any of them is
highly debatable:
Roman Catholic and Orthodox Churches, 1000+ years
European Universities, 900+ years; US universities, hundreds of years
A handful of banks, 200 years maximum; The Hudson’s Bay Company, 200
years
The churches all had schisms, and near-collapse. The ancient universities
similarly underwent interregna and were generally founded for nowsuppressed religious purposes.
A strawman plan (see Baker, Schmitt, Wunsch,
2007, Oceanography) & later talk by Ray
Schmitt
The scarcest asset is the right
people. Need the very best scientists and
engineers, but don’t need them full time.
Need decadal commitments and a mechanism for
review and renewal.
Carrot: Major salary (where an issue), and
research support say 50% of normal salary.
Support for a student and post-doc, or
laboratory funding,…. No restriction on the
research pursued.
In return:
30% of time, on average, devoted to open-ended global
observations and/or model assessments. Would range from
lobbying governments to sustain measurements, routinely
checking calibrations, testing new technologies, engaging in
discussions of technology replacements, …
Would NOT be the observation-funding agency itself---that
would continue to lie with governments.
Thirty to fifty, mid-career, people world-wide. Would form a kind
of senate or parliament which would maintain a long-term
perspective. Self-perpetuating by consensus. A 10-20 year
commitment. A mechanism for reviewing individual’s activities
every 10-15 years.
A globally distributed system with a managerial focus
somewhere in the world.
Needs an endowment. Something under
US$1billion would do it.
(Would not be the resource for funding observations.) Pocket
money for some people
Harvard University endowment today is about US$35billion.
Perhaps there is another, better way. Can we get a dialogue
started? Urgent: unobserved climate change is gone
Not often can one identify a true intergenerational problem. This is one. Is there
anything more important we can do
collectively?
forever.
Thank you.