LB01, Lamon bay
LB01, Bifurcation track
vertical black bar: core
X: XBT
V: vertical net tows
O: oblique net tows
Red triangle: TRBM
Vertical red bar: line moorings
S-max
NPsubtropical
Polillo depression
Pressure db [meters]
“Port Irene bay”
S-min
NPIW
Polillo depression
Polillo depression O2-min
100-200 m
frequent O2-min
“Port Irene bay”
All CTD
Stratification: LB01, LB02, LB02 (NE)
Lower thermocline
O2-min
Kuroshio S-max
LB02 thermohaline pattern (red and cyan) in Lamon Bay
reflects dominance of North Equatorial Current (NEC)
water; whereas LB01 (black) reflects Kuroshio
recirculation gyre regime.
The cyan LB02 stations, with Kuroshio T/S, are in the
northeastern part of the station array. The LB02 green
stations are within the embayment of Port Irene.
The LB02 nascent Kuroshio is composed of NEC T/S
LB1
Kuroshio S-min
NPIW
NEC S-min
LB2
LB1
NEC S-max
LB2
All CTD stations: 1-78
CTD 1-78
NEC,
S-max
Black: LB0-1
Red: LB02
Cyan: LB02
Green: LB02
NPIW
Kuroshio
Polillo channel
Kuroshio
LB2
LB1
Polillo and ‘Port Irene Bay’
Kuroshio
NEC
All CTD stations: 1-78
NEC
Kuroshio
LB02: dominate NEC signature, except in NE part of stations array
LB01
LB02
Focus on Lamon Bay south of 17.5°N:
LB01 Black
LB02 Red
LB01
Message: the time period (april/may
2012) of LB02 displays greater
presence tropical North Equatorial
Current water than the LB01 period
(May/June, 2011), why?
LB02
18.35°N
western boundary
western boundary
NEC S-max
North Pacific S-min
Kuroshio
looking north
looking south
17.12°N
western boundary
NEC S-max
western boundary
looking north
looking north
16.50°N
western boundary
western boundary
NEC S-max
North Pacific S-min
Kuroshio
looking north
looking south
Southern boundary
NEC S-max
North Pacific
S-max & S-min
Kuroshio
124.25°E
looking west
Southern boundary
looking west
Lamon Bay cruise 1, 23-55 m current vectors,
Lamon Bay cruise 2, 23-55 m current vectors, as of 8
May 2012
Kuroshio
recirculation gyre
SSS
color coded
anticyclone
dipole
cyclonic dipole
cyclonic dipole
Polillo current
Polillo current
SSS
color coded
Solid arrows denote stronger flow, with clear T/S source water signal. LB02 Kuroshio recirculation gyre retreats
northward to be replaced by NEC waters; LB01 shows southward penetration of the Kuroshio recirculation gyre, with
reduced NEC water [vectors not to same scale]
+15.3 Sv
+10 Sv, LB01
D+2.6 Sv
-5.5 Sv
+12.4 Sv
+11 Sv, LB01
D-2.2 Sv
-10.2 Sv
LB02 Transports [~±15%?], upper 300 m
North Equatorial
Current
North Equatorial
Current
[weaker] Mindanao Current
NEC bifurcation, April 2012,
During R/V Revelle transit,
Freemantle to Legaspi.
[stronger] Mindanao Current
NEC bifurcation, late May
2011, during R/V Revelle
transit to south to avoid
tyhpoon Songda
April 2012
La Niña
Stronger Kuroshio, enriched in
Equatorial water
May 2011
Neutral
Kuroshio
Weaker Kuroshio
Kuroshio
Luzon Strait throughflow
Weak or ~0
Luzon Strait throughflow
North Equatorial Current
North Equatorial Current
For supporting information see ppt
slide ‘Notes page’; see next slide for
relation to Aviso
Possible Implications of an ENSO [bifurcation]
dependent Kuroshio source:
§ During La Niña there is increased injection of NEC
tropical Pacific water into the subtropical North Pacific;
during El Niño the subtropical North Pacific is more 'isolated'
from the NEC.
§ The NEC enhanced Kuroshio transport during La Niña,
leads to greater northward heat flux into the North Pacific;
reduces western pacific warm pool volume.
§ The NEC injection into the subtropical regime, on climatic
average (the integrated La Niña/El Niño phases), balances
the loss of North Pacific water through the Bering Straits (~1
Sv) and through Luzon Strait (~3 Sv) into the South China
Sea (that most likely advects into the Indian Ocean as part of
the Indonesia Throughflow). During El Niño the Kuroshio
recirculation gyre reaches into Lamon Bay, to can feed the
westward ‘leakage’ into the South China Sea, (Luzon Strait
westward transport is increased during El Niño, HYCOM,
Hurbert et al 2011). In this way the Kuroshio recirculation
gyre exports the accumulated NEC injected during the
previous La Niña phases.
§ More... effect on ecosystems, linkage with PDO, impact
on ITF, WPWP ...
ITF comment: During El Niño
the SCS throughflow via
Sibutu Passage blocks
Mindanao surface layer
leakage to Makassar Strait,
which lowers the Makassar
net transport, counteracting
thegreater Mindanao transport
associated with the northern
bifurcation position.
Dt = 4°C @ 200 m;
18°C isotherm Dz = @ 70 m
Deeper isotherms
Shallower isotherms