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Anthropogenic aerosol deposition reduces the
sensitivity of oceanic productivity to warming
Feng Zhou (Peking University, [email protected])Rong Wang, Yves Balkanski, Laurent Bopp, Didier Hauglustaine, Philippe Ciais
INI2016 in Melbourne
Dec 4-8, 2016
McNutt, M. (2015), Science, 348, 841–841
25% CO2 is absorbed by the ocean,moderating climate warming
Ocean acidity increased by 30%,having negative impact on oceanicnet primary productivity (NPP)
30%
Ocean is a large sink of the Earth’s carbonemission, sustaining the habitability ofEarth
Motivation1
Behrenfeld et al. (2010) in Nature; Gregg and Rousseaux (2014), JGR
Multiple satellite data indicated that all North Hemisphere and EquatorialIndian basin experienced a significant decline of Chlorophyll-a (or NPP)
Motivation1
Increasing
Decreasing
Current: Such climate-driven decline is attributed mainly to the increasingthermal stratification of ocean water columns (reduced mixing, lower N supply,decreased phytoplankton).
From L Bopp in LSCE
ENSO - Observations
Motivation1
Future: The decline is simulated by ocean biogeochemical model and isexpected to continue further, reducing oceanic NPP and hence CO2 sink (-6% to-25% in 2050).
Bopp et al., 2013 in Biogeosciences
Motivation1
In contrast, anthropogenic aerosols provide nutrients to the surface oceans,
which stimulate the phytoplankton and promote the oceanic NPP.
Key question addressed -------
Can aerosol deposition partly offset the
decline of NPP caused by warming?
Motivation1
To understand the impact of aerosol deposition, we simulated the
change of Nr, phosphate (PO4), and sFe, deposition from 1850 to 2010
in a global atmospheric general circulation model (GCM) and input the
results into an ocean biogeochemical model with the varying climate.
Emission GCM Deposition Ocean model
NPP
Climate change
NPP Temperature
Data and methods2
Species Sector Source Period
NH3 + NOx + N2O Agriculture, CombustionACCMIP and MACCity
PKU-inventory1850-2010
NO + N2O + NH3 Natural soil, ocean PKU-inventory Constant
P + Fe Combustion, wildfire PKU-inventory 1960-2007
P + Fe Dust, biogenic aerosol, volcano Mahowald et al., 2008 Constant
P Bioavailability: 10% of P from dust, 100% of P from volcanoes, and 50% of P from others
Fe Bioavailability: 12± 9% for coal fly ash, 63.0 ± 17.0% for vehicle oil, 79.8 ± 8.5% for
heavy oil, 30± 14% for biomass, 2± 4% for dust
Data and methods2 Emission http://inventory.pku.edu.cn/
Historical emissions of Nr, PO4 and sFe
(0.5 0.5 grid cell)
• Increased by 1.8, 0.8, 0.4 times since
1850 globally
• Nr: increased until 1990s, then kept
stable
• PO4: persistently increased due to
biofuels and deforestation
• sFe: increased until 1990s and then
declined, due to dust abatment & use of
cleaner fuels
Data and methods2
Data and methods2An oceanic biogeochemical model NEMO-PISCES version 2 to simulate Nr, PO4, sFeas well as Chlorophyll and NPP
Aumont et al., 2015, Geosci. Model Dev., 8, 2465–2513
A global chemistry-aerosol-climate model LMDz-OR-INCA tosimulate aerosol deposition
Hauglustaine et al., 2014 in ACP
Models from LSCE
Data and methods2
The difference was considered as the response to aerosol deposition
Model performance3
Wang et al., ACP, 2015
Hauglustaine et al., 2014
NH4
NO3
PO4 Fe
Modeled v.s. observed deposition
Observed deposition: CASNET, EMEP, EANET
Model performance3
10-3 100 10110-110-3
B101
10-2
100
Mod
elle
d sF
e (μ
mol
m-3
)
Observed sFe (μmol m-3)
10-1
10-2
N 214RMSD 0.64NMB -68%
CTL
10-3 100 10110-1
N 214RMSD 0.57NMB -63%
10-3
C101
10-2
100
Mod
elle
d sF
e (μ
mol
m-3
)
Observed sFe (μmol m-3)
10-1
10-2
DEP
10-4 100 10210-2
N 13 974RMSD 0.56NMB -46%
10-4
A102
10-2
100
Observed NO3 (mmol m-3)
Mod
elle
dN
O3
(mm
olm
-3)
12 2671
DEP
Mod
elle
dP
O4
(mm
olm
-3)
10-4
B102
Observed PO4 (mmol m-3)
10-2
10-4 100 102
100
10-2
N 75 656RMSD 0.46NMB -47%
91 6851
DEP
10-4 100 10210-210-4
B102
10-2
100
Observed NO3 (mmol m-3)
Mod
elle
dN
O3
(mm
olm
-3)
10 9791
N 12 439RMSD 0.61NMB -56%
CTL
Mod
elle
dP
O4
(mm
olm
-3)
10-4
D102
Observed PO4 (mmol m-3)
10-2
10-4 100 102
100
10-2
N 81 949RMSD 0.45NMB -45%
103 4601
CTL RMSD 0.18NMB -39%
Mod
eled
[Chl
](m
g m
-3)
10-2
101
Observed [Chl] (mg m-3)
10-1
10-2 100 101
100
10-1
N = 182552
196
836
B
RMSD 0.17NMB -38%
N = 182552Mod
eled
[Chl
](m
g m
-3)
10-2
101
Observed [Chl] (mg m-3)
10-1
10-2 100 101
100
10-1
198
187
D
182,552 data
214 data
438,240 data
170,588 data
https://www.nodc.noaa.gov/OC5/WOD13/; http://www.bodc.ac.uk/geotraces/
NO3
PO4
sFe
Chl-a
Model performance3
Pre-industrial, 1850 1997-2013
Nr (1850) Nr (1997-2013)
P (1850) P (1997-2013)
Impact to concentration4
DIN sFe
PO4
AD increases the concentrations ofDIN and sFe,but decreases PO4, due to theenhancing phytoplankton growth
226 v.s. 9 Gmol yr-1
Difference of 2 experiments
Impact to concentration4
Chl-a
NPP1.3 Pg yr-1
34%
Difference of 2 experiments
the ocean area with a relative differencelarger than 10% for DIN and Chl-a/NPPaccounts for 65% and 34%, respectively
65%
>10%
RD=Difference in 0.5
Mean in 0.5
Impact to NPP sensitivity5
Figure: Changes of the annual mean sea-surface temperature (SST) and oceanic NPP in thepermanently stratified oceans from 1948-1977 to 1978-2007 in the simulations (A) with, or (B)without aerosol deposition
Behrenfeld et al. [2006] found an inverse relationship. We observed a similar
relationship when comparing the period from 1948–1977 to 1978–2007
Impact to NPP sensitivity5
SST: Sea-surface temperature
However, aerosol depositiondecreases the sensitivity ofNPP to SST changes
NPP Temperature
15 to 13 Pg Cyr-1 C-1 or 12.5%
• North Pacific: 23% (2.56->1.96)
• North Atlantic: 40% (0.35 to 0.21)
• Indian: 25% (1.1 to 0.83)
Take-home messages6• Aerosol deposition offsets the oceanic NPP sensitivity to SST, which
is much important for calculating terrestrial carbon source/sink
(=Emission – atmosphere sink – ocean sink)
• Future observation-based techniques to detect the influence of
global warming on oceanic NPP have to take into account the role of
aerosol deposition esp. of Nr
• Fertilizing effects of aerosols (N, PO4, sFe) should be considered
along with the effects of climate change in driving NPP variations
Wang R., Zhou F., et al., GRL, 2016
Thanks so much for your attention
Feng [email protected]