1. PDO Negative (Normal) H Jet Stream Jet Stream L Warm KOE
Omega
Block
Over
British
Columbia
Weak Aleutian Low
La Nina Dominates
0 N
140 E.
180 E
130 W.

2. Weak SST Gradient Sets Aleutian Low
Negative Feedback
Heat
Flux L
Weak SST Gradient Sets Aleutian Low
Strength
Wind stress agitates waters,
Thermocline waters mix to
surface
Thermoclinic Mode Waters
(Relatively warm waters from low latitudes)

3. Positive Feedback L Lowers Salinity Mixed layer Shallows. Heat Flux
Rain
Strong SST Gradient Sets Aleutian Low
Strength
Wind stress agitates waters,
Thermocline waters mix to
surface
Thermoclinic Mode Waters
(Depleted of low latitude water,
possibly from Sea of Okhtotsk or Bering Strait)

4. Possible Sources of Mode Water
66.5 N
Arctic Ocean Water
through Bering Strait
Known to correlate
Cold, salty water
From sea ice formation
on Gulf of Alaska
Cold, salty water
From sea ice formation
on Sea of Okhtotsk
KOCS
Diffusion/ Advection from subtropical gyres
Diffusion/Advection from subtropical gyres
0 N
140 E.
180 E

5. Definition of Mode Water
According to the American Meteorological Society
Glossary [
Mode water is:
‘A term for water of exceptionally uniform properties
over an extensive depth range, caused in most instances
by convection.
‘Mode waters represent regions of water mass
formation; they are not necessarily water masses but
contribute significant volumes of water to other water
masses. Because they represent regions of deep sinking
of surface water, mode water formation regions are
atmospheric heat sources.’
[It’s not exactly the sense I use it in, but propithermoclinic
would be a bit ridiculous. I mean waters that do not penetrate
the thermocline that are entrained in the mixed layer transiently.]

6. PDO Positive Jet Stream Jet Stream H L Cool KOE El Nino Dominates
Heavy rain
Jet Stream H L
Cool KOE
Omega
Block
Over
British
Columbia
Weakens
Strong Aleutian Low
El Nino Dominates
0 N
140 E.
180 E
130 W.

7. Favoring strong El Nino
ENSO Feedback (I)
66.5 N
Omega
Block
breaks
Jet Stream
Oyashio delivers cold pulse to equatorial
W. Pacific
Limits tropical mode
Water delivery (?)
TNH pattern (?)
Favoring strong El Nino
0 N
140 E.
180 E

8. Cold Mode Water Delivery Inhibited
Gyre reverses
Blocks Bering
Strait flow
Less
Sea
Ice
On Sea of Okhtotsk (?)
Little sea
Ice on Gulf
Of Alaska
0 N
140 E.
180 E

9. Strong El Nino followed by strong La Nina
ENSO Feedback (II)
66.5 N
Warm pulse adds warm mode water as does
Advection/diffusion from tropics
Warm pulse along KOCS due to La Nina
Strong El Nino followed by strong La Nina
0 N
140 E.
180 E