About NIES, Ministry of Environment National Institute for Environmental Studies

1
SOOP observation of sea surface pCO2 covering
northern North Pacific since 1995?Climatology,
interannual variability, strategy expanding to
global coverage
Yukihiro Nojiri (NIES) C. S. Wong (IOS), Jiye
Zeng, Shigeru Kariya, Tomonori Watai (GEF),
Masahiko Fujii, Hitoshi Mukai, Yasumi Fujinuma,
Toshinobu Machida (NIES)
GCP Workshop, 2003-Jan-13, Paris
2
Measurement of ocean surface biogeochemical
parameters for global carbon cycle research

• Ocean surface pCO2 (CO2 partial pressure)
• estimation of ocean CO2 flux (source and sink)
  from difference of DpCO2 (ocean-atmosphere pCO2)
• global ocean carbon cycle model requests global
  oceanic DpCO2 observational map with seasonal or
  monthly resolution for model evaluation
• information about inter-annual variability of
  DpCO2 map is helpful to interpret
  atmosphere/ocean partitioning of anthropogenic
  CO2, and its temporal change

3
Monthly resolution, how?

• One of solutions
• Commercial cargo ship as VOS (volunteer
  observation ship)/SOOP (ship-of-opportunity)

• North Pacific and North Atlantic
• cargo ship cruises are operated monthly (round
  trip interval of four to six weeks), container
  liner, lumber ship, and car carrier
• Water intake line installation is usually the key
  problem to start observation of biogeochemical
  parameters

4
Starting up

• NIES monitoring network by VOS
• Started primarily for atmospheric observation
  using canister sampling on board Japan-Australian
  container liner from 1992

• NIES/IOS, Canada joint study for North Pacific
  surface ocean biogeochemistry
• pCO2 continuous measurement and discrete water
  sampling
• SST and SSS measurement as biproducts

5
North Pacific VOS Monitoring from 1995
M/S Skaugran, Seaboard (Canada) lumber/car
carrier, Japan-Vancouver and US West Coast,
atmosphere/ocean 1995 Mar.-1999 Sept. operation
by laboratory technician on board
M/S Alligator Hope, MOL (Japan) container
carrier, Japan-Seattle, Vancouver,
atmosphere/ocean 1999 Nov.-2001 May operation
by contracted seaman
M/S Pyxis, Toyofuji (Japan) Toyota car carrier,
Japan-Portland, Oakland, Long Beach, atmosphere
2001 Nov.-present ocean 2002 Jul.-present operat
ion by contracted seaman
6
CGER/NIES VOS Cruise Line in North Pacific
Skaugran route (38 round trips of measurement in
4.5 years) Ports variable Wide coverage north of
34N Difficulty in time series analysis
Alligator Hope route (16 round trips of
measurement in 1.5 years) Ports fixed Dense time
series in sub-arctic Pacific
Pyxis route (from 2002 summer) Poets fixed, mid
lat. coverage
7
Measurement parameters in the cargo ship
monitoring program of North Pacific since 1995
8
System Arrangement on board M/S Skaugran
Skaugran Observation system occupied upper floor
in engine room. 2 different pCO2 systems (shower
bubbling) to ensure accuracy. Modem and
atmosphere lines were installed from top
deck. Problems were long seawater line, and oily
and dusty environment.
9
M/S Alligator Hope on board water and air pCO2
system
10
air radio room
data logging through ethernet in a server computer
Water and air pCO2 system on board M/S Pyxis
water pump room
11
OSP
KNOT
HOT
M/S Skaugran ship route of observation
(Mar.1995-Mar.1999) and selected bands for
seasonal functions 34 round trips were carried
out with on board operators. Western bound legs
were generally great circle route from Vancouver
to Japan. East bound legs have variable routes.
More than million of pCO2 data were logged. Data
north of 34N were served for analysis using pCO2
seasonal functions.
12
low latitude winter low/summer high temperature
effectgtbiology
high latitude winter high/summer low temperature
effectltbiology
Example of seasonal functions of DpCO2 along a
meridian Seasonal functions of ?pCO2 for four
latitudinal bands of the 175?W longitudinal
section. The line shows the seasonal function
fit and diamonds the observed data.
13
Winter
Spring
Summer
Autumn
Monthly maps of ?pCO2 (ocean-atmosphere) in
?atm Data analysis from M/S Skaugran monitoring
(April 1995 March 1999)
14
Seasonal net flux of CO2 for North Pacific north
of 34N, mgC/m2/day (Jan.-Mar.) (Apr.-Jun.) (Jul.-
Sept.) (Oct.-Dec.)
Annual integration, flux in Mt (0.001Gt) Total
integration for North Pacific 0.24 GtC/y
15
Skaugran monitoring home page Measurement detail
and data are available from web
(http//www-cger.nies.go.jp/index.html) under
cooperation with MIRC/JHA (Marine Information
Research Center of Japan Hydrographic
Association).
16
Detection of inter-annual variability in pCO2 and
nutrient

• Eastern subarctic Pacific (Ocean Station P) shows
  small seasonal variability in pCO2, because of
  the compensating effects of summer biological
  productivity (pCO2 decrease) and temperature
  effect (pCO2 increase). ref Takahashi et al.
  (1993 and 2002)

• NIES pCO2 monitoring data set has good coverage
  for eastern subarctic Pacific, north of Station
  P.
• Data for 1995-1999 showed remarkably constant
  pCO2 without seasonal change, having
  climatological average of zero delta pCO2.

17
Climatological annual mean from 1995-1999 obs.
2001
2000
Seasonal change of DpCO2 (seawater minus
atmosphere) at 50-54N, 145W in the eastern North
Pacific
18
Nutrient change in 2000 summer pCO2 drawdown event

• No significant change in summer average
  concentrations of nitrate and phosphate

• Silicate depletion at the pCO2 drawdown event
• Diatom blooming, which might be similar to the
  silicate depletion event recorded at station P in
  1970s (era of weather ship in station P time
  series)

• The Si/NO3 assimilation ratio in diatom showed
  high in the blooming. The Si/pCO2 anomaly should
  be results of iron supply event. Possible iron
  supply is Siberian dust of forest fire

• North-south scale of the silicate drawdown
  (possibly same as pCO2 drawdown) was
  approximately 500 km.

19
Objective analysis of inter-annual variability of
pCO2 in NP

• Change of DpCO2
• Cooling ? temperature effect,
• ? vertical mixing
• Heating ? temperature effect,
• ? shallower ML enhances biological drawdown

Winter south
Winter north
cooling
mixing
cooling
mixing
20
Objective analysis of inter-annual variability of
pCO2 in NP

• Comparison
• year by year annual mean vs. climatological
  annual mean
• Climatology ? climatological annual mean for
  1995-2000
• Annual mean ? year of full seasonal coverage
• As the result, possible comparison is only given
  where good observational coverage.
• However, there is less uncertainty comes from
  interpolation.

21
St.P
KNOT
pCO2 Climatology from SK and AH observation from
1995-2001
22
How to extract climatological DpCO2

• Fixed 2.5 x 2.5 degree grid point

Example 155E, 42.5N grid pt
155.0
152.5
cruise routes
cruise routes
7 cruises available in 2.5x2.5 grid
42.5
12cruises available in 4.5x4.5 grid
40.0
quasi 2.5 x 2.5 grid (actually 4.5 x 4.5 grid)
23
2000
Year by year cruise route of pCO2 measurement by
SK and AH
24
Actually available SK and AH data in 155E, 42.5N
grid for 2.5 degree grid scheme and quasi 2.5
degree grid scheme
25
Example of cruise availability (155E, 42.5N,
2000 Apr.-2001 Mar.)
17 cruises for quali 2.5 degree (4.5 degree)
scheme and then give climatology.
7 cruises in one year period, but lack of autumn
data! No climatology
2.5x2.5
4.5x4.5
26
Actually available SK and AH data in 155E, 42.5N
grid for 2.5 degree grid scheme and quasi 2.5
degree grid scheme
27
St.P
KNOT
example grid
Climatology available grids have at least 3 years
of full seasonal coverage data during 1995 April
and 2001 March
28
1995
1996
1997
1998
1999
2000
Year by year cruise route of pCO2 measurement by
SK and AH
29
(Annual averaged DpCO2 field) minus (Climatology)
1995
1996
1997
1998
1999
2000
30
St.P
KNOT
Zonal analysis of pCO2 difference from climatology
31
1995
1996
1997
1999
2000
32
Summary of interannual variability of DpCO2 in
the North Pacific
33
Summary of interannual variability of DpCO2 in
the North Pacific
Smaller basin like Bering Sea may show more
significant interannual change, however, the
relationship with SST and SSS change is not clear.
34
Inter-annual variability of DpCO2 in the northern
N.Pacific

• Simple and strait forward analysis was applied
  for the over 6 year data set of surface pCO2 by
  SOOP/VOS.
• No interpolation technique was used, but, the
  data observed in a grid having compete seasonal
  coverage in a single year were just averaged.

• Subarctic North Pacific showed extremely small
  inter-annual change in DpCO2 (/-3 matm in West,
  /- 10 matm in East) as the zonal average for the
  period (1995-2000) including intense El Nino of
  1997/98.

• Smaller ocean basin like Bering Sea may have much
  clearer inter-annual difference which could be
  related to the change of biological and/or
  physical processes.

35
Networking DpCO2 monitoring in the global ocean

• Necessary precision and accuracy in pCO2 or DpCO2
• Ideally 1 or 2 matm in DpCO2 (oceanatmosphere
  differential, or both ocean and atmosphere)
• Subtraction of climatological atmospheric CO2 is
  not ideal.
• Ancillary measurements
• necessary SST, SSS
• useful underway fluorescence, discrete carbon
  parameters, nutrients, chlorophyll and pigments

36
Networking DpCO2 monitoring in the global ocean

• Combination of SOOP/VOS and autonomous buoy
• SOOP/VOS
• Stable cruise route is requested to get year
  around coverage.
• 3 ships in a large ocean basin (N Pacific, N
  Atlantic, S Pacific, S Atlantic and Indian), then
  high, middle and low latitude may be covered with
  monthly or bimonthly coverage. It needs
  bilateral collaboration at ports of both sides of
  the basin.
• Fulfillment of accuracy will be possible with
  inter-calibration exercises.
• Unmanned operation? Solution is the employment
  of seamen.

37
Networking DpCO2 monitoring in the global ocean

• Combination of SOOP/VOS and autonomous buoy
• buoy
• How many buoys are necessary to represent zonal
  average DpCO2? 5 or 10 in sub-basin (W N Pacific
  subarctic) scale? It may not to be 2 or 3? (but
  it is from my feeling)
• How to keep accuracy?
• Buoy should be strongly useful
• getting time series change of pCO2
• ocean basin scarcely have cargo ship routes

38
Photo of Japanese Domestic Intercalibration in
1998

• Standard gas supply lines to all the pCO2 system

• Seawater line of 300L/min flow rate.

39
pCO2 Inter-comparison setting

• Standard gas supply line to all the pCO2 system
  was installed.

Pool side deck
T sensors
Equilibrators
Thermosalinograph
main water flow
Floating pCO2 systems
underwater pump

• Experience from the 1998 intercomparison results,
  we will prepare best situation of
  inter-comparison.
• Standard gas supply line to all the pCO2 system
  was installed.
• Main water line of 300 L/min will be installed on
  the deck.
• Two Thermosalinograph are installed at the upper
  and lower stream of the water line to ensure no
  temperature difference.
• Calibrated temperature sensors will be supplied
  to all the equilibrators to ensure 0.3 matm
  resolution in pCO2 comparison.

40
International ocean pCO2 intercomparison using
indoor seawater pool

• Proposed date
• March 10 (Mon)14 (Fri), 2003

• Sponsorship
• Ministry of Environment, Japan
• National Institute for Environmental Studies
  (NIES)
• Location
• Hazaki, Japan
• 30 km east of Tokyo/Narita Airport