carbon uptake and seasonal traits of antarctic
TRANSCRIPT
CUSTARDCarbon Uptake and Seasonal Traits of
Antarctic Remineralisation Depth
CUSTARD is part of
Role of the Southern Ocean in the Earth System
(RoSES)
Also includes• ORCHESTRA (PI Mike Meredith, NERC centres)• SONATA (PI Corinne le Quere)• PICCOLO (PI Karen Heywood)
55S60S 50S65S
500m
1000m
4000m
surface
SAMW
AAIW
AABW
CDW
SubAntarcticFront
PolarFront
Latitude
Dep
th
55S60S 50S65S
500m
1000m
4000m
surface
SAMW
AAIW
AABW
CDW
SubAntarcticFront
PolarFront
Latitude
Dep
th
55S60S 50S65S
500m
1000m
4000m
surface3
4
SAMW
AAIW
AABW
CDW
2
1
SubAntarcticFront
PolarFront
Latitude
Dep
th
0.35 Pg C /yr
S. Ocean total C uptake rate =1.2 Pg C /yrLandschützer et al. (2015) Science
Southern Oceannatural Cuptake rate
Carbon flux into the Southern Ocean
Uncertainty 1861-2005
Anthropogenic 20 Pg C a
Natural >50 Pg C b
a Frölicher et al (2015) J.Climb CUSTARD preliminary modelling
S
Depth of remineralisation
300mSi
nkin
g ra
te (m
/d)
0.8
0.6
0.4
0.2
0.0Iron
repleteIron
stressedRedrawn fromMuggli et al. (1996) MEPS
1.0
Image courtesy of M. Iversen
Actinocyclus sp.
Seasonal influences onremineralisation depth
• Iron• Silicate• Phytoplankton community• Phytoplankton physiology• Primary and export production
Hypothesis:
The seasonal interplay ofupper limb surface biogeochemistry, circulation and remineralisation
controls how long carbon entering the ocean is kept out of the
atmosphere.
Approach
• Focus on key water mass formation area
• Sensors, mooring & gliders: annual cycle
• Cruise: gradients, dynamic spring period
• Modelling: consequences for C
Location
Holte & Talley (2009) JAOTech
Sr1b
Location
OOITN
TS
Holte & Talley (2009) JAOTech
What are the seasonal air-sea C flux and macronutrient drawdown? (WP1)
• C data in key mode water area• Seasonal CO2 and drivers • Seasonal silicate & nitrate• Augmented by repeat transects
in spring Bouman et al. (2012)
o wintero summer
Landschützer et al. (2013)
OOITS
What is the seasonality in iron stress and its impacts? (WP2)
• Full year time series of productivity & iron stress
• Response to iron stress• Iron dynamics in key spring
period Browning et al. (2014)
Redrawn from Moore et al. (2007)
silic
ate:
nitr
ate
(mol
:mol
)4
3
2
1
0
noadded
ironadded
iron
low high
Iron stress
What is the seasonality in remineralisation depth? (WP3)
• Annual time-series of remin. depth• Cutting-edge glider method (GOCART)• Cruise Marine Snowcatcher samples:
- benchmark, composition, speed
Flux
at 4
00
mFl
ux a
t 10
0m
days
How does seasonality in S. Oceanremin. depth affect C storage? (WP4)
• Quantify fate of organic C• Multiple models for robustness• Parameterisations
?
Cruise
The CUSTARD team
WP1 WP2
WP3 WP4
CUSTARD
CARBON ironsilica
phytoplankton
mode water
remin.depth
Extra
Southern OceanNatural CUptake rate
~0.2 Pg C yr-1
Based on estimate with largest uncertainty in Marsay et al. (2015)
From Takeda et al. (1998) Nature
From Brown,…Landschützer, Bakker et al., (2015) GBC
Seasonal variation in export
Calculated using the export algorithm of Henson et al. (2012)
Jul Sep Nov Jan Mar May
0.4
0.3
0.5
0.2
0.1
Expo
rt flux (gCm
‐2day‐1 )