Summary of third meeting of ENSOs and Regime Shifts group

 
Date of Meeting: 24 September 1997
Place: International Pacific Halibut Commission conference room

Present at the meeting:

Steven Hare (IPHC), Bob Francis (UW), Brian Bigler (Wards Cove), Warren Wooster (UW), John Field (UW), Bill Pinnix (UW), Curt Ebbesmeyer (Evans-Hamilton), Jim Ingraham (NMFS), Nate Mantua (JISAO), Richard Strickland (UW), Jim Overland (PMEL), Jennifer Adams (PMEL).
 

Before beginning discussion, we showed new overheads. Jim Ingraham brought a sea level pressure map for today downloaded from the FNMOC web site. There was an extremely strong low pressure cell centered around Kodiak. Pressure at the center of the cell was 968 mbar. Jennifer Adams noted how a number of the PMEL group were sampling up around Kodiak and had been getting tossed around for several days. Steven Hare presented several graphs of historical changes in the halibut stock. Interdecadal changes have been noted in halibut growth, recruitment and size at maturity. Since the 1977 regime shift, halibut average weight at age has declined by 50% in Alaska but barely declined at all in British Columbia. The relationship between stock (either numbers or biomass) has changed dramatically with all data since the 1977 year class occupying a space well outside the cloud of points for the 1946-1976 year classes. Richard Strickland and John Field brought graphs of the Oyster Condition Index for the period 1954-1997. On a scale where 10 indicates plump and 5 is scrawny, we see a very sharp downturn in oyster condition after 1977. Between 1954 and 1976, average condition was 8-9; since 1977 average has been 4-6. There is no appearance of an upturn in condition after 1995.

 
At this meeting we focused on discussion item #1 from the proposed agenda list:

  1. Scales of climate variability
On what temporal and spatial scales can we identify climate variability that is important to marine ecosystems
How do these climate processes (ENSO, PDO, global warming, spring transition) affect the NE Pacific
What are the definitions of the terms we use, e.g., regime shifts, (inter)decadal, PDO   Hare started off with an attempt to define the term regime shift:

 

Definition of Regime Shift
Main Entry: re·gime
Variant(s): also ré·gime /rA-'zhEm, ri- also ri-'jEm/
Function: noun
Etymology: French régime, from Latin regimin-, regimen
Date: 1776
1 a : REGIMEN
1 b : a regular pattern of occurrence or action (as of seasonal rainfall)
1 c : the characteristic behavior or orderly procedure of a natural phenomenon or process
 

Main Entry: shift
Pronunciation: 'shift
Function: noun
Date: 1523
3 a : a change in direction <a shift in the wind>
3 b : a change in emphasis, judgment, or attitude
 

Regime shift

A pronounced and prolonged change in the characteristic atmosphere-ocean climate of a region.

Temporal Domain – regime duration is significantly longer than the shift duration
Spatial Domain – as applied to climate the spatial scale is on the order of atmospheric pressure systems and oceanic gyres
 
 

For the remainder of the morning, we discussed the many climate phenomenon identified as important in the North Pacific:
 

Climatic processes (possibly) affecting the NE Pacific
 
 
Jim Overland also presented an analysis of teleconnection indices he is currently undertaking. In essence, he has found an abrupt change in the sign of 2 indices, the Polar and West Pacific teleconnctions, that shifted sign around 1990. The PNA index did not switch and still remains about the same as it has since 1977. Another index, that of sea level pressure associated with the Aleutian Low was modeled as a function of the three teleconnection index. A good mulitple regression fit was made with an r-value of 0.94. Interestingly, two conclusions were drawn. A coherent shift in all three indices occurred in 1977 and 2 of the three shifted signs in 1990. The SLP index showed a very strong change in 1977, but has been weak and inconsistent since 1990. It may be that Arctic/West Pacific processes play a bigger role than has been previosly advertised.

 

We agreed that in the next meeting we would tackle Topic #2 from the list, i.e.:

  1. How do the ecosystem components respond
What are the different response times of various species
What are the pathways by which climate affects organisms
What is the relative importance of fishing vis-à-vis climate and other ecological interactions (Is Thompson-Burkenroad resolvable?)   Next meeting: 8 October 1997, 9 AM.

Where: IPHC conference room.