Climate change research in the Gulf of Alaska Russ Hopcroft, Ken Coyle, Tom Weingartner, Terry Whitledge Mountains have profound affect on the ocean

Why care? Late 1960’s Mid 1970’s Early 1980’s Changes catches in a small mesh bottom trawl in Pavlof Bay, Alaska, through the regime shift of the mid-1970s.

Recapitulate the Basin current systems. Then the Shelf current system Recapitulate the Basin current systems. Then the Shelf current system. These are organized flow pathways that can transmit climate signals from afar into the GOA and Bering Sea. The black bars indicate annual precipitation rates which are very high because storms interact with mountainous terrain. The precipitation is converted to runoff that affects ocean structure. Precipitation and runoff is poorly known! The currents and water column properties respond to changes in the Aleutian Low Pressure System and convey physical and biological climate signals from lower latitudes.

COASTAL GULF OF ALASKA STUDY AREA Data over ~3 decades GLOBEC 1997-2004 “Why is this system so productive…..” Climate: Salmon NPRB 2005 & 2006 Long-term? 200km

Annual cycle Surface water warms seasonally PWS and Alaska Coastal Current freshen over summer & fall

April 1, 2003 May 16, 2003 Cross-shelf Average Primary production starts on the inner shelf earlier (0.5 – 1 month) than the mid- and outer shelf where it peaks in May

Neocalanus The success of the zooplankton that dominate the spring is related to their unique adaptations to the production cycles of the Gulf

Would climate change lead to a year-round dominance of small species (poor fish food)???? Note that while Neocalanus may dominate biomass, Pseudocalanus dominates annual production due to year-round growth, especially in warm Summer/Fall

How does 2005 compare? Mixed layer was warmer than all other GLOBEC Mays (2003 was later than all other years, therefore warmer)

At Gak1 (where we have 10-20 years of data) mixed layer was warmer than long-term means MAY SEPT

Across the line, the average temperature (i. e Across the line, the average temperature (i.e. total amount of heat) looks less unusual MAY SEPT 13 1

May 2005 Nothing unusual about chlorophyll or zooplankton …But higher number of pteropods (pink salmon food?)

Copepods have 6 stages, more late stages suggests faster growth 2005 appears to have faster growth than many years (for both species) Direct measurements less clear (limited data)

Fall 2005 Several other “southern species” also observed 1998 99 00 01 02 03 2005 1998 99 00 01 02 03 2005 Several other “southern species” also observed

Summary The Gulf of Alaska was warmer in 2005 than typical for a “non-El Niño” year, and this appears to have favored faster development of the spring zooplankton Much of the North American West coast experienced such anomalous conditions (with delayed pelagic production south of Alaska) These basin-wide conditions favored the transport of “southern species” northward into the Gulf of Alaska Implications for Fisheries?