Northeast Pacific Report

Northeast Pacific Program Update

Ted Strub and Suzanne Strom provided the update for the Northeast Pacific. The NEP has been concerned with organizing a mesoscale monitoring component which, although identified as an important part of the project, it was not initially funded. However, both historical and recent observations indicate the existence of persistent mesoscale features in both the Coastal Gulf of Alaska and California Coastal Current study areas. This persistence should allow an effective mesoscale survey to be designed. Negotiations are underway to see if this important work can be added to the project.

Ted began with a description of altimeter data observed around the Seward survey line. These data suggest that temporal and spatial variability in mesoscale circulation could be considered the largest controlling factors in the region. In the Coastal Gulf of Alaska (CGOA) most occupied stations are along the Seward Line. A second line (the Cape Clear Section) was added parallel to and 'upstream' of the Seward Line to provide a context for these observations. In the Hecate Bank region there is some predictability between years in the temperature field.

In the California Coastal Current (CCC) Adriana Huyer et al. have conducted hydrographic surveys out of New Port (44.6ƒ N) since 1997. This Long Term Observing Program was in place to observe the El Nino/La Nina transition. Mark Ohman suggested examining the Scripps Pier air temperature time series in conjunction with the historical data associated with the Newport survey. The Scripps Pier data display a shift to a warmer state in the mid 1970's and salp abundance measured in CalCOFI monitoring declined during this same time period.

Ted next discussed sardine synchrony across ocean basins and related it to the 200hPa height anomalies.

Botsford is working in the CGOA and CCC to examine relationships between chinook and coho salmon which are responding to the same environmental changes in different ways. Spawning distributions do not account for observed differences.

Dale Haidvogel briefly discussed finite element (FEM) and finite difference (FDM) modeling in the Northeast Pacific Program. Those involved in this effort include Zack Powell, Craig Lewis, Al Hermann, Chris Edwards, Hal Batchelder and Dale et al. The circulation models comprise a suite of nested models varying from 40km basin scales and 10km NEP scale to 2km regional models capable of resolving estuarine processes. Time step and spatial scale constraints actually make the larger models cheaper to run. Runs of the 10km scale model should begin in a couple of months. Currently there are a series of idealized model runs being conducted to examine upwelling near capes and banks. The velocity fields from these model runs are being used by Batchelder for biological modeling and Edwards for energetics.

Biological modeling in the NEP is occurring on a number of fronts. NPZ modeling is being carried out by both Zack Powell and Sarah Hinkley. There are significant differences between these efforts. Sarah's model is striving for initial realism and uses 10 component model, Zack's simpler model is composed of 4 components. Hal Batchelder et al. have developed an individual based model for copepods. The IBM is coupled to hydrodynamic and NPZ models. These researchers were interested in understanding how environmental conditions could influence individual growth and behavior and how this may effect nearshore retention and demographic processes. The IBM includes feeding and vertical migration and suggests that vertical migration plays an important role in the success of copepods in the system.

Zack Powell suggested a comparison between biological models in the different programs, especially between Hal's copepod model and Eileen's krill model. Hal's work uses an NPZ model and 'food' is calculated at run time. Velocity is read from a saved field. The physical model used in the Southern Ocean Program is ROMS.

Ted Strub discussed the improvements three new long range radar sites have made over existing short range stations. The three stations are located in Florence, Cape Blanco and Cresent Hill. (How far out were the 80% returns? And what were they before?)

Ships used last year were the New Horizon (for plankton, birds and mammals), the Sea Eagle (for fish trawling) and the Wecoma (for SeaSoar work). This year the ships will be arranged more efficiently. Research taking place onboard any particular ship will be more compatible.

Suzanne Strom provided an update on the Coastal Gulf of Alaska Program. She talked about the general region, its relation to the Kurishio Current and the importance of buoyancy on the Alaska Current. She talked about the LTOP studies beginning in 1997 and the ongoing process studies. Next she gave Tim Wiengartner's overview of the hydrography of the CGOA region.

The shelf in the Gulf of Alaska is deep with complex topography and is subject to strong downwelling. Eddies sometimes persist in the vicinity of the Seward Line and Suzanne pointed out the importance of the Cape Clear Section in providing upstream information for the Seward Line data. She also discussed sampling strategies on the Seward Line (occupying a number of stations around each main station). A figure showing the upwelling index and river discharge for over a year was discussed. Both of these factors determine buoyancy and stratification in the CGOA region. Although the figure was representative, the timing of the peaks changes from year to year.

Along the Seward Line higher biomass is typically encountered on the west end of the line. There are also changes in community composition as one moves offshore. For example, in Agust 2000 pink sDuring the April 18-25 2000 survey zooplankton biomass was high in the ACC and Seawifs recorded significant mesoscale variability including shelf break eddies. Several months later, August 13-17, pink salmon.

Seawifs indicated lots of mesoscale variability in the area including shelf break eddys.

Zooplankton biomass was high in ACC.

13-17 August 2000 on the Seward line. Had a plot along the Seward line showing Pink Salmon and Rock fish abundance. Pink salmon were abundant inshore, rockfish offshore. www.ims.uaf.edu:8000/globec/results

The shelf can divided into three different regions based on the hydrographic regime characteristics. The inner shelf or ACC 35-50km, the midshelf from 50-100km and the shelf break front seaward.

Biological dynamics (turnover) are on the order of 3-10 days so one would expect to get changes within coherent features during a sampling.

Brunt Vaisala frequencies where calculated for different areas on the shelf the inner shelf is dominated by Salinity (buoyancy, stratification), the midshelf was dominated by temperature and salinity, the outsehlf was dominated by temerature and salinity too.

Stratification doesnt occur uniformly in the GOA, fresh water input is very important so flow patterns are crucially important. Productivity in the Gulf of Alaska is not locked to solar cycles.

Ken Loyle did a MDCA cluster analysis and found that the inner, mid, outer and Prince Willian Sound areas separate out fairly well for zooplankton and hytdrographics.

Autocorrelation of hydroacoustics along the Seaward line to look at length scales for zooplankton to fish sized organisms. Zero crossings occured at about 10km in May 1998 and 20km in May 1999. The Rosby radius is about 10km. The length scale of the patches, then, is on the order of the length scale of the Rossby Radius and therefore on the size of the mesoscale features....

Eddy driven freshwater losses may be a source of seasonal/interannual variability.

There are persistent features, the big eddy and assocaited upwelling areas.

Process cruises - Early spring, Late spring and Mid summer (Strom)

Neocalanus sp, Pseudocalanus, Calanus and Eucalanus (growth on all, Fecuntidy? on last three)

Three stations along Seward Line and in Prince William Sound. Core station and fine scale grid survey added to get background information around the core station.

The species composition in the Prince William Sound outflow is different than else where on the inner shelf.

Large cells are driving the variability in Chl

Andy Thompsons Seawifs image from July 2001

Cell division rates are about 0.7 day or a doubling about every day

Growth rates of different sized cells in April, May and July show that growth rates are lower than expected indicating limiting nutrients. Experiments say that there are limiting nutrients on the inner, mid shelf but not on the outer shelf or in Prince William Sound, despite a lot of stratification AND expectation of limitation out there. Largest cells are stimulated to the greatest extent when nutrients are limited.

FlowCam - microzooplankton imaging. Numbers of about 10 cells/liter can be handled by the system and you get near real time images of whats in the water.

Copepods are removing microzooplankton and releasing diatoms from predation. See plots with different grazer communities....

Timelines

CGOA - LTOP 6/year March, April, May, July, August and December for the next three years to 2003. No field work next year as resources are shifted to the California Coastal Current. Next process work will be in 2003.

CCC - LTOP will be in 2001, 2002 and 2003. Process work to be conducted next year in 2002.

Mesoscale Needs (Strub) Mesoscale surveys are almost obviously important to the region.

Is SeaSoar synoptic? No but the survey can be run in about five days and featuresd are relatively stable within that time frame. Phytoplankton appear in warm features. Hermann's models, which are under resolved in the area right now, display reasonable dynamics and suggest processes(?) are autocorrelated for 6-9 days in the ACC and 3-6 days.... (WHERE - In the trough?)

Surface water seems to flow out at the surface along the trough as offshoot of the ACC, water is moving in at depth.

Drifters suggest cytclonic flow within the basin and have been tracked as long as 15 days (retained?)

The NOAA guy asked is aircraft could be used to deploy xbt to get a handle on the physical environment. And a surface salinity mapper is under development. The bottom line here was that a mesoscale survey should be attempted eeven if the ideal survey can't be funded.

Two cruises at 20 days each should cost about 150K.

Need to be certain that LTOP and process cruises are done with respect to the mesoscale surveys in some coherent strategy. LTOPs give broader time dynamics.

Difficulty in ship scheduling is not necessarily a good reason for not having a mesoscale survey... xbts are expensive. NCAR has aircraft (a C130) that isn't being used very much during the next couple years. NOAA has a P3 and can get ocean color data too. May be free this time of year. Perhaps investigating Coast Guard overflights?

So we need an additional source of funding to get this part of the program in place.

Kneric suggested that it might be very productive to list current infrastructure capable of providing coverage to the program. What can be leveraged, what do we know. Such as: Salmon Surveys by NMFS, CCC Work, Seawifs image collections, Gliders, other available transects...) Talk about adjustments to cover areas they haven't worked in.

Because we want to do system to system comparisons it may be very important that the CGOA and CCC are comparable.

Letter from SSC to DAVID might be a good way to begin.

150-200K will be needed to run the survey plus an additional 2 years to work up the data. Say 500K per field year and 250K for analysis for the next two years.

Comparability to other programs especially within the NEP is critical

SO: CTD, BIOMAPER, Net tows, top trophics

NEP: CTD, Seasoar, net tows

GB: CTD, Biomaper, Net tows

A draft AO for the mesoscale should be released around January 2002. A short, well defined draft AO.

NEP website should be set up as an easy to access clearing house for information to facilitate proposal writing by the populace.

Someone should start drafting the AO NOW, Probably Hal, Mike, Ted and Suzanne.

Should be scientifically justafiable research.

Need draft AO asap

David Ainley presented information on the abundance and distribution of birds, copepods, phytoplankton and nutrients in the Haecate Bank region. Copepod and bird abundance was high where nutrients were high. Animals were concentrationed around fronts. David said the 85% of the auklet variability was accounted for by phytoplankton. However, the birds occurred around the periphery of the bloom and were feeding on phytoplankton grazers such as euphausids. Mature blooms are nutrient limited so phytoplankton must have some strategy of avoiding grazing. If microplankton were the dominant grazer, their numbers might lag the bloom by only about six hours. The dynamics are complex and prey switching is very likely to play an important role.