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.

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)

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)

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

Definition of Mode Water According to the American Meteorological Society Glossary [http://amsglossary.allenpress.com] 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.]

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.

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

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

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