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Labrador Sea convection blows life to the Northeastern Atlantic
Keywords: Ocean-shelf exchange, sub-decadal variability,
Predictability, Calanus finmarchicus
Hjálmar Hátún, Katja Lohmann, Selma Pacariz, Manfred Bersch Assthor Gislasson, Daniela Matei, Jón Ólafsson, Chris Reid and Johann Jungclaus
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http://www.frs.fo/default.asphttp://www.mpimet.mpg.de/
The energetic and productive North Atlantic Ocean
High (algae) concentrations
Ocean Color (chlorophyll-a)
The energetic and productive North Atlantic Ocean
m
Winter mixed layer depths (MLD)
Seasonal amplitude
Outline
1. The subpolar gyre - a main food source 2. Remote forcing from the Labrador Sea
to the Irminger Sea 3. Mixed Layer Depth (MLD) - a critical driver 4. The sub-arctic front 5. Predictability
Subtropical Gyre
Subpolar Gyre
Labrador Sea convection
The subpolar gyre - a main food source
(Hatun et al., Science 2005)
R
I
Salinity in the Irminger Current (obs.)
Salinity at Rockall (obs.)
Gyre index Weak.
Strong
Mid-1990s Regime shift
(Hátún et al., 2009)
Salinity ‘dips’
The Subpolar Gyre - salinity ’dips’
or Great Salinity Anomalies
On-shelf biological production
MPIOM (Max Planck Institute Ocean Model)
(Matei et al., 2012)
Gyre index (high-passed)
Zooplankton
The Subpolar Gyre and on-shelf biological production
Strong gyre high production
PV
From: (Pickart, 2003)/(Talley & McCartney, 1982)
Convection
Degree of stratification
~ 1 yr
Nitrate
Silicate
(Concentrations in June, 50m)
The Subpolar Gyre: A large nutrient source
CPR
We’ll discuss nutrients next time
Green- land
Towing lines since the 1940s The subpolar gyre is a zooplankton epicenter
(Hátún, et al., 2009)
Average abundance of Calanus finmarchicus
The Subpolar Gyre: A large zooplankton source - Continuous Plankton Recorder (CPR)
South Iceland shelf
Mainly C. finmarchicus
Hypothesis: A north-eastward extended subpolar gyre limb in the Irminger Sea improves the biological productivity southwest of Iceland – both oceanic and potentially on the shelf.
2. Remote forcing advection from the Labrador Sea to the Irminger Sea
Is the zooplankton simply related to the North Atlantic Oscillation (NAO)?
NÃO
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-0.5
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Longitude
Latit
ude
-60 -55 -50 -45 -40 -35 -30 -25 -20 -15
48
50
52
54
56
58
60
62
64
Jan-April
Corr. coeff
Remote atmospheric forcing
MLD (in North IrB) vs. Heat loss
Atmospheric forcing: heat loss (W/m2) Not local
Greenland
Particle tracking experiment
Seeding Region (March)
Target region
Greenland
MPIOM
# pa
rtic
les
~ 1 year
3. Mixed Layer Depth (MLD) a critical driver
Mixed Layer Depth
Greenland
MLD
MPIOM
Simulated March Mixed Layer Depths (MLD) N. Irminger Sea (35-30°W, 61-63°N)
MLD and oceanic Calanus finmarchicus C. finmarchicus (adults)
Green- land
CPR
MLD
Oceanic and on-shelf zooplankton C. finmarchicus (adults)
Simulated March MLDs and zooplankton on the south Iceland shelf
Convection accentuates the ‘high-or-low’ variability
4. The biologically productive sub-arctic front
Finwhales (Víkingsson et al., 2009)
Mackerel in 2013 (PGNAPES)
Bluefin tuna (Mackenzie, Payne et al., 2014)
Redfish (Pedchenko, 2005)
EOF-upper ocean temperature (Hátún et al., 2005)
The biologically productive sub-arctic front
Front Index (MPIOM)
Shelf zooplankton
Frontal shift towards Iceland
Increased zooplankton abundance when the sub-arctic front is shifted towards Iceland
Heat loss
Labrador Sea
Heat loss
Iceland shelf
Increase early Prim. Prod.
On-shelf Prim. Prod.
‘Phyto-convection’ (Backhaus et al., 1999) and/or ‘Dilution-Recoupling’ (Behrenfeld, 2010)
Highly nutrient rich
Mixed Layer Depth (MLD) - a critical parameter
Let’s re-cap
Green- land
Lab Sea
Heat loss
Lab Sea
Heat loss
Iceland shelf
Highly nutrient rich
Jan
Apr
Jul
Oct
Dec
Seeded 1/4 year 2000, depth 6
MPIOM: Particle tracking
~ 1-4 months
1-4 months
Jan
Apr
Jul
Oct
Dec
y p
MPIOM: Particle tracking
5. Predictability
10.5 months lead Start in June
Ranked probability skill score
SST Predictability Intra-seasonal to inter-annual
Seasonal forecasting system. US National Multi-Model Ensemble (NMME)
Ranked probability skill score
US National Multi-Model Ensemble (NMME) seasonal forecasting system.
SST Predictability Intra-seasonal to inter-annual
10.5 months lead Start in March Amongst the highest predictability
potential in the World
Stronger convection again in 2012 and 2014: We predict(ed) increased production
Messages
• A north-eastward extended subpolar gyre limb in the Irminger Sea improves the biological productivity southwest of Iceland – both oceanic and potentially on the shelf
• Mechanistic understanding potential for
prediction (0.5 to 1.5 years ahead)
The research leading to these results has received funding from the European Union 7th Framework Programme (FP7 2007-2013), under grant agreement n.308299 NACLIM www.naclim.eu
http://www.naclim.eu/
Labrador Sea convection� blows life to the Northeastern AtlanticThe energetic and productive� North Atlantic OceanThe energetic and productive� North Atlantic OceanOutlineSlide Number 5Slide Number 6Slide Number 7Slide Number 8Slide Number 9Slide Number 102. Remote forcing advection from the Labrador Sea to the Irminger Sea�Slide Number 13Particle tracking �experiment3. Mixed Layer Depth (MLD) �a critical driver�Mixed Layer DepthSimulated March Mixed Layer Depths (MLD)�N. Irminger Sea (35-30°W, 61-63°N)MLD and oceanic Calanus finmarchicusOceanic and on-shelf zooplanktonSimulated March MLDs and� zooplankton on the south Iceland shelf4. The biologically productive�sub-arctic frontSlide Number 22Slide Number 23Slide Number 245. Predictability SST Predictability �Intra-seasonal to inter-annualSST Predictability �Intra-seasonal to inter-annualMessagesSlide Number 29