LB01, Lamon bay LB01, Bifurcation track

vertical black bar: coreX: XBTV: vertical net towsO: oblique net towsRed triangle: TRBMVertical red bar: line moorings

vertical black bar: coreX: XBTV: vertical net towsO: oblique net towsRed triangle: TRBMVertical red bar: line moorings

Pres

sure

db

[met

ers]thermocline

S-maxNPsubtropical

S-minNPIW

Lower thermoclineO2-min

100-200 m frequent O2-min

Polillo depression O2-min

Polillo depressionPolillo depression

All CTD

Stratification: LB01, LB02, LB02 (NE)

“Port Irene bay”

“Port Irene bay”

“Port Irene bay”

LB1

LB2

LB1 LB2

All CTD stations: 1-78

Polillo channel

NPIW

NEC S-max

Kuroshio S-min

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

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

NEC S-min

Kuroshio S-max

LB1LB2

CTD 1-78

Kuroshio

Polillo channel

NPIW

NEC, S-max

Black: LB0-1Red: LB02Cyan: LB02Green: LB02

Kuroshio

NECPolillo and ‘Port Irene Bay’

NEC

Kuroshio

All CTD stations: 1-78

Kuroshio

LB02: dominate NEC signature, except in NE part of stations array

Focus on Lamon Bay south of 17.5°N:LB01 BlackLB02 Red

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?

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?

LB01LB02

LB01

LB02

18.35°N

17.12°N

looking south

looking north

western boundary

western boundary

NEC S-max

North Pacific S-minKuroshio

NEC S-max

looking north

wes

tern

bou

ndar

y

looking north

wes

tern

bou

ndar

y

looking south

western boundary

NEC S-max

North Pacific S-minKuroshio

looking west

NEC S-max

Nor

th P

acifi

c S-

max

& S

-min

Kuro

shio

16.50°N

124.25°E

Southern boundary

looking north

wes

tern

bou

ndar

y

looking westSo

uthe

rn b

ound

ary

Lamon Bay cruise 2, 23-55 m current vectors, as of 8 May 2012

Lamon Bay cruise 2, 23-55 m current vectors, as of 8 May 2012

SSS color coded

Strong NEC source

cyclonic dipole

anticyclonic dipole

Kuroshio feeder current

Polillo current

anticyclone dipole

Lam

on bi

furc

ation

Polillo current

Lamon Bay cruise 1, 23-55 m current vectors, Lamon Bay cruise 1, 23-55 m current vectors,

Lam

on bi

furc

ation

cyclonic dipole

Kuroshio recirculation gyre

Weak NEC signal

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]

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]

SSS color coded

Kuroshio recirculation gyre

Nascent Kuroshio

Nascent Kuroshio

LB02 Transports [~±15%?], upper 300 mLB02 Transports [~±15%?], upper 300 m

-10.2 Sv

+12.4 Sv

-5.5 Sv

+15.3 Sv

2.6 Sv

2.2 Sv

+10 Sv, LB01

+11 Sv, LB01

Bifurcation

10° - 11° N North Equatorial Current

NEC bifurcation, April 2012,During R/V Revelle transit, Freemantle to Legaspi.

[stronger] Mindanao Current

North Equatorial Current

Bifurcation

~13° - 14° N

NEC bifurcation, late May 2011, during R/V Revelle transit to south to avoid tyhpoon Songda

[weaker] Mindanao Current

April 2012La Niña

April 2012La Niña

May 2011Neutral

May 2011Neutral

bifu

rcatio

n

bifu

rcatio

n

North Equatorial Current

North Equatorial Current

Mindanao

Mindanao

Kuroshio

Kuroshio

South China Sea throughflow

Luzon Strait throughflowWeak or ~0Luzon Strait throughflow

Weak South China Sea throughflow

Stronge

r Mak

assa

r ITF

Wea

ker M

akas

sar IT

F

For supporting information see ppt slide ‘Notes page’; see next slide for

relation to Aviso

For supporting information see ppt slide ‘Notes page’; see next slide for

relation to Aviso

Stronger Kuroshio, enriched in Equatorial water

Weaker Kuroshio

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.

t = 4°C @ 200 m;18°C isotherm z = @ 70 m

Kuroshio

Shallower isotherms

Deeper isotherms