Carbon/Nutrient Dynamics and Fluxes over
Shelf Systems (CANDYFLOSS)
Jonathan Sharples (University of Liverpool)
C, N, P, Si cycling on the NW European shelf, towards
understanding the role of the shelf in carbon export
Background
It is broadly accepted that shelf seas provide a net sink for atmospheric CO2:
0.35 GT C a-1, or 29% of global oceanic uptake of anthropogenic C (Chen & Borges, 2009)
Also thought to drive >40% of global particulate carbon sequestration (Muller-Karger et al., 2005)
Work in the North Sea has established a paradigm for carbon export from a
stratifying shelf (Thomas et al., Science, 2004)
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2 Objectives
1. How much carbon does the
NW European shelf remove
from the atmosphere in a year?
2. How is this carbon export
sustained?
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Objective 1
Quantify how much carbon is exported from the NW European shelf.
What is the annual air-sea
CO2 flux over the entire NW
European shelf?
How much of the shelf
water is exchanged with the
adjacent ocean, and what
are the water elemental
properties?
Does the exported water
reach depths below the
winter mixed layer?
Does C get buried in shelf
sediments (WP2) and how is
particulate matter
transported at the shelf
edge?
From Simpson & Sharples,
2012. Rates from LOIS-SES
(Wolff, Univ of Liverpool)
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Approach (Objective 1)
Summer sea surface temperature
12 months of nutrient and carbonate
chemistry sampling
Daily surface sampling, key transects,
moorings (Marine Scotland, CEFAS, AFBI,
Irish Marine Institute). Collaboration with
5 groups running ferry box routes
(Roscoff, HZG, Universities of Bergen,
Vigo, Las Palmas)
Earth-Observation and statistical
techniques to interpolate across patchy
data fields.
Utilise existing databases on riverine and
atmospheric inputs.
Achieving this Objective will be
challenging, but brings with it a great
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prize.
Objective 2
Determine how the carbon export is sustained.
C
THE PROBLEM:
C:Nfixed
thermocline
If C:Nfixed = C:Nexport then shelf
nutrient pools will be diminished
C:Nexport
C
N
If C:N is constant, then we need a
supply of excess N from elsewhere
SOLUTION 1:
C:Nexport
C
SOLUTION 2:
C:Nexport
C:Nfixed < C:Nexport due to different
rates of elemental cycling on shelf
(water column and sediments)
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Approach (Objective 2)
Summer sea surface temperature
Four process cruises
Key physics-biogeochemistry process
stations and moorings, whole-shelf
transects, backed up with gliders and
Earth Observation.
Cruises timed at key stages of the
seasonal cycle.
Collaborative effort: elemental cycling
quantified both in water column, and in
sediments.
Celtic Sea: A generic temperate shelf
region with well-constrained physics.
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Key Constraints for Models
Models lack validation data and are hampered by inaccurate process descriptions.
e.g. modellers request:
Whole-shelf observational
maps of carbonate and
nutrient chemistry over 12
months
Vertically-resolved time
series of carbon and
nutrient chemistry at key
location
Time series of turbulence
during onset of stratification
We will supply data types and process descriptions identified as priorities by
modellers (See deliverables S1 – S17)
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Synthesis
9 partners
FASTNEt
Objective 1:
Whole shelf C, N, P,
Si, CO2 flux, C export
WP3
Iron fluxes
2 partners
WP2
Sediments
whole- shelf data:
calibration/validation
WP4
Modelling
Objective 2:
Process studies C, N,
P, Si, cycling,
stoichiometry
rate measurements,
process descriptions,
C, N, P, Si budgets
How much carbon does the NW European shelf export,
and how does it sustain this.
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