Download - Fueling the ocean biological pump
![Page 1: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/1.jpg)
Fueling the ocean
biological pumpJorge Sarmiento
& Jennifer SimeonPrinceton University
![Page 2: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/2.jpg)
Fueling the ocean biological pump
I. IntroductionA. The problem and a hypothesisB. Support for the hypothesis
1. From model simulations2. From observations (Si* and water mass analysis)
II. Gaining insights from model simulations
III. ImplicationsIV. Future research
![Page 3: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/3.jpg)
The Problem• Sediment traps suggest that ~one-third of
the particulate organic matter flux at 200 m continues past the base of the main thermocline (defined as = 26.8)
• If nitrate lost by the above particle sinking were not replaced, the thermocline nitrate would be depleted within ~50 years!
• QUERY: How do nutrients return from the deep ocean to the thermocline?
![Page 4: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/4.jpg)
(Sarmiento et al., Nature, 2004)
Hypo-thesis:
The main return pathway for nutrients from the deep ocean is Subantarctic Mode Water (SAMW)
![Page 5: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/5.jpg)
Support from model
simulations
![Page 6: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/6.jpg)
RESULT: ~Three-quarters of biological production N of 30°S is controlled by nutrients fed in from the south. Most of the effect occurs in the density interval corresponding to SAMW and upper AAIW ( < 27.3; LL model; Marinov et al., Nature, 2006)
“normal”
Nutrient depletion south of 30°S
Primary evidence:
Export production
(Pg C yr-1 deg-1)
![Page 7: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/7.jpg)
Support from Si*
Observations
![Page 8: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/8.jpg)
SAMW forms in deep wintertime mixed layers in the Southern
Ocean spanning the Subantarctic
Front
Density increases from 26.5 to 27.1 in an eastward
circuit from W. Atlantic Ocean
(McCartney, 1977)
Fronts = STF (N&S), SAF, & PF
Zones = SAZ and PFZ
![Page 9: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/9.jpg)
Southern Ocean Nitrate and Silicic Acid Distributions
•An unusual characteristic of the waters spanning the Subantarctic Front is their high nitrate and low silicic acid concentrations.
•We find that Si* = Si(OH)4 - NO3- is an excellent tracer of
these low silicic acid high nitrate surface waters
![Page 10: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/10.jpg)
Si* and wintertime mixed layer depth
Note that low Si* region (blue on left) matches deep wintertime mixed layer where SAMW forms (red on right).
![Page 11: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/11.jpg)
Si* on 26.8 (~SAMW) isopycnal shows global extent of the SAMW influence
•This isopycnal surface is at the depth of the NPIW (North Pacific Intermediate Water), which forms in the Sea of Okhotsk and "mixed water region" between the Kuroshio and Oyashio Currents. Tidal mixing may play a central role there.
![Page 12: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/12.jpg)
There is nowhere else at the surface of the ocean where Si* is negative
But why is Si* so negative in this band?
`
![Page 13: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/13.jpg)
-When stressed (e.g., by iron or light limitation), diatoms tend to build more silicified shells, leading to a Si to NO3 uptake ratio of 2:1 and higher [Hutchins and Bruland, 1998; Takeda, 1998.]
-When diatoms have adequate light and nutrients, they tend to take up Si and nitrate in a ratio close to 1:1
-Hypothesis: iron or light stress in Southern Ocean leads to high Si to NO3 uptake ratio, which generates negative Si*
Schematic of nutrient cycle in Southern Ocean
![Page 14: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/14.jpg)
Support from water type
analysis
![Page 15: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/15.jpg)
Plancherel et al. (pers. comm.)
water type analysis
• Si* on WOCE Indian Ocean I8S+I9N section (Western Indian Ocean)
• SAMW water type fraction (STMW water type above, AAIW water type below)
![Page 16: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/16.jpg)
Fueling the ocean biological pump
I. Introduction
II. Gaining insights from model simulations
A. Tagged water type simulations
B. Tagged phosphate simulations
III. Implications
IV. Future research
![Page 17: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/17.jpg)
Tagged water type simulations
![Page 18: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/18.jpg)
SAMW
AAIW
Northern
Tropical
Tagging water types
•Dye tracers are used to determine the relative contribution of four water types (black) to the main thermocline (blue)
•Tracer is set to 1 in black area, set to 0 in white area, conserved in blue area.
![Page 19: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/19.jpg)
Fractional contribution of different water types to the main thermocline ( < 27.4)
(LL model)
SAMW
North
Tropical
AAIW
![Page 20: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/20.jpg)
Fractional contribution of different water types to the main thermocline. Average above = 26.5
(LL model)
![Page 21: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/21.jpg)
“Typical” model
Kv = 0.6 cm2 s
-1 AI = 2000 m2 s-1
HH
Low vertical mixing model
Kv = 0.15 cm2 s
-1 AI = 1000 m2 s-1 LL-low Kv
High wind model
LL with ECMWF winds (higher over Southern Ocean), narrowed Drake Passage, higher surface S in Weddell & Ross Seas, 50 cm2 s-1 between top two layers, and 1.3 cm2 s-1 in Southern Ocean.
P2A-high wind
Three models were used:
⎟⎟⎠
⎞⎜⎜⎝
⎛−+=
S
y
Ix
s
Sxv
L
DAL
f
L
D
AKpDg
ρ
τ
ρε
δ 2
Gnanadesikan (1999)0
1
2
![Page 22: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/22.jpg)
LL-low Kv
HH
P2A-high wind
Meridional overturnin
g (Sv)
NADW
NADW
NADW
![Page 23: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/23.jpg)
Transport in waters of < 27.4
P2A-high winds
HH
LL-low KvNorthward flow
Southward flow
![Page 24: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/24.jpg)
MODEL SAMW TROPICAL NPAC AAIW NATL HH 0.450 0.291 0.189 0.033 0.028
LL-low Kv 0.592 0.070 0.285 0.021 0.029
P2A-high wind 0.700 0.047 0.189 0.016 0.038
Fractional contributions of water types to the upper thermocline ( <
26.5) by different models
Annual, global average at Year 400
Simulating a strong SAMW influence requires low vertical mixing and high Southern Ocean winds
![Page 25: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/25.jpg)
Which model is more “realistic”?
Observations
Pacific radiocarbon at 150°W (P16) favors P2A. LL has too low deep concentrations. HH has too low surface concentrations.
![Page 26: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/26.jpg)
However, observational analyses favor low latitude upwelling (HH)
We plan to explore localized vertical mixing in regions of strong interactions between tides, internal waves, and rough topography as an alternative mechanism for low latitude upwelling.
![Page 27: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/27.jpg)
Tagged phosphatesimulations
![Page 28: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/28.jpg)
Phosphate partitioning in nutrient model
Total
SAMW
Tropical
NPAC South
NAtl
AAIW
Remin
(LL model)
![Page 29: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/29.jpg)
Phosphate partitioning in LL model - average
above 26.5
Total
SAMW
Tropical
NPAC
Remin
![Page 30: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/30.jpg)
Phosphate end-members(fractional contribution above 26.5)
![Page 31: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/31.jpg)
Model new production: Contribution from each end-member
![Page 32: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/32.jpg)
LL
HH
P2A
Net Phosphate
flux through 26.5
Red is positive
(upwards)
(mmol m-2 y-
1)
![Page 33: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/33.jpg)
Conclusions(1) Fueling the biological pump
SAMW accounts directly for about 20% of biological production in the world ocean.
Indirectly (including remineralized production) SAMW and AAIW together account for more than two-thirds of biological production north of 30°S - most of this is due to SAMW.
The NPIW accounts for North Pacific nutrient return(2) Processes controlling the rate of SAMW formation
• Low interior vertical mixing shifts NADW return flow from low latitudes to Southern Ocean (and North Pacific)
• High Southern Ocean winds increase upwelling in Southern Ocean, shifting it away from North Pacific and tropics.
(3) Mechanisms & pathways by which SAMW enters the upper thermocline
• Primarily by advection along isopycnals from southeast corner of subtropical gyres followed by upwelling along boundaries
• Small amount of surface (Ekman) transport to north
![Page 34: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/34.jpg)
Fueling the ocean biological pump
I. IntroductionII. Gaining insights from model
simulationsIII. Implications
A. For global diatom productionB. For deep trapping of Si(OH)4
C. For global warming response
IV. Future research
![Page 35: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/35.jpg)
For global diatom
production
![Page 36: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/36.jpg)
Silicic acid to nitrate supply ratio across 100 m
€
J opal
J organic nitrogen
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟=
Si(OH)4 100 −200 m− Si(OH)4 0 −100 m( )∑
NO3-
100 −200 m− NO3
-
0 −100 m( )∑
![Page 37: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/37.jpg)
For deep trapping of
Si(OH)4
![Page 38: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/38.jpg)
WOCE “Conveyor Belt” Sections
![Page 39: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/39.jpg)
Nitratemol/kg)
Silicic Acidmol/kg)
![Page 40: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/40.jpg)
Regional analysis of results from Schlitzer adjoint model
Preservation fraction enhancement: fi2000 m/133 m=fAverage2000m/133m⋅εipreservationwhere
fAverage2000m/133m=ΦTotal(2000m)ΦTotal(133m)εipreservation=Φi(2000m)Φi(133m)fAverage2000m/133m
Export production enhancement: fi133 m=fiArea⋅εiproductionwhere
fiArea=AreaiAreaTotalεiproduction=Φi(133m)ΦTotal(133m)fiArea
Φi(2000m)=ΦTotal(133m)⋅fi133m⋅fi2000m/133m
Sarmiento et al. (2007)
![Page 41: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/41.jpg)
Opal flux analysis
Sarmiento et al. (2007)
![Page 42: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/42.jpg)
Organic nitrogen flux analysis
Sarmiento et al. (2007)
![Page 43: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/43.jpg)
Summary of implications
• The low silicic acid to relative to nitrate of SAMW represents a key factor determining Si limitation of diatoms in low latitudes.
• The high silicic acid relative to nitrate of the deep ocean is due to high export in the Southern Ocean, not to a globally distributed deep dissolution of opal.
• GFDL climate model shows modest response of the SAMW return path to global warming. Paleo-implications examined by Brzezinski et al. (2002) & Matsumoto et al. (2002).
![Page 44: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/44.jpg)
Fueling the ocean biological pump
I. IntroductionII. Further insights from model simulationsIII. ImplicationsIV. Future research
A. Further work with water mass analysis (Y. Plancherel)
B. Pathways from thermocline to surface (J. Palter)C. Return pathway of MOC: exploration of localized
mixing mechanisms using 14C and 3He (D. Bianchi)D. Global warming response (A. Gnanadesikan, J.
Simeon, E. Galbraith)
![Page 45: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/45.jpg)
Watermass budgeting in GFDL CM2.1 coupled climate
model
Net transformation into density class= Flow out on east
– Flow in on west (fixed at 80°E)– Flow in on North
![Page 46: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/46.jpg)
Budget for years 300-320 of 1860 control south of 30°S
Formation of Mode-Intermediate waters from mixing light and dense waters (light waters predominate)
Dense to light transformation
Net lightening of dense water
![Page 47: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/47.jpg)
Comparison with 1%/yr to 2X CO2 run (Control fluxes are bold lines)
More intermediate water formation from dense water south of Australia.
Net lightening essentially unchanged
Less transformation of light to intermediate waters north of Kerguelen.
![Page 48: Fueling the ocean biological pump](https://reader033.vdocuments.us/reader033/viewer/2022051218/56815a7d550346895dc7e704/html5/thumbnails/48.jpg)
Summary of global warming simulations
• Upwelling transformation of dense water essentially unchanged.
• Eventual fate of deep water (mode/intermediate vs. lighter waters) changes somewhat.
• Transformation in Southern Indian vs. Australia shows major shifts.