NOAA Technical Memorandum NMFS-AFSC-8

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Alaska Fisheries Science Center

January 1993

by

Bruce L. Wing

Winter Oceanographic Conditions

in the Eastern Gulf of Alaska,

January-February 1986
NOAA Technical Memorandum NMFS

The National Marine Fisheries Service's Alaska Fisheries Science Center

uses the NOAA Technical Memorandum series to issue informal scientific and

technical publications when complete formal review and editorial processing

are not appropriate or feasible. Documents within this series reflect sound

professional work and may be referenced in the formal scientific and technical

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The NMFS-AFSC Technical Memorandum series of the Alaska Fisheries

Science Center continues the NMFS-F/NWC series established in 1970 by the

Northwest Fisheries Center. The new NMFS-NWFSC series will be used by

the Northwest Fisheries Science Center.

This document should be cited as follows: 

 Wing, B. L. 1993. Winter oceanographic conditions in the eastern 

Gulf of Alaska, January-February 1986. U.S. Dep. Commer., NOAA

Tech. Memo. NMFS-AFSC-8, 53 p.

Reference in this document to trade names does not imply endorsement by

the National Marine Fisheries Service, NOAA.
NOAA Technical Memorandum NMFS-AFSC-8

Winter Oceanographic Conditions

in the Eastern Gulf of Alaska,

January-February 1986

by

Bruce L. Wing

Alaska Fisheries Science Center

Auke Bay Laboratory

11305 Glacier Highway

Juneau, Alaska 99801-8626

U.S. DEPARTMENT OF COMMERCE

Barbara Hackman Franklin, Secretary

National Oceanic and Atmospheric Administration

John A. Knauss, Administrator

National Marina Fisheries Service

William W. Fox, Jr., Assistant Administrator for Fisheries

January 1993
This document is available to the public through:

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iii

ABSTRACT

In 1986, Eastern Gulf of Alaska oceanographic conditions

in January-February (the beginning of the Pacific halibut

(Hippoglossus stenolepis) and sablefish (Anoplopoma fimbria)

spawning period) were determined from 32 stations east of long.

140°W between lat. 56°N and lat. 58°N. A well-mixed surface

layer characterized by temperatures near 6°C and salinities of

32.25-32.75% was present throughout most of the study area.

West of the continental slope, this surface layer extendedto

the permanent pycnocline at 50-150 m. The pycnocline was

weakest over the continental slope and absent over the

continental shelf. Below the pycnocline to 1,000 m,

temperatures decreased from 6.0°C to less than 3.5°C and

salinities increased from 33.75% to greater than 34.25%.

A northward-flowing subsurface current was present along

the continental slope at or below the pycnocline. This current

was distinguished by weak thermal maxima from 6.5° to 7.0°C at

125-150 m. These core temperatures diminished from south to

north. The eastern boundary of the current appeared to be the

continental slope. I hypothesizes that this subsurface current

is the Haida Current whose surface manifestation was erased by

the storm and terrestrial runoff conditions of the 1985-86

winter.
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V

CONTENTS

INTRODUCTION 

DATA AND METHODS 

RESULTS

DISCUSSION

Sitka Eddy

Source of Subsurface Current

California Undercurrent 

Alaska Current 

Haida Current

SUMMARY

ACKNOWLEDGMENTS

CITATIONS 

APPENDIX 

1

2

2

4

4

9

9

12

12

13

14

15

17

Preceding page blank 
Currents of the eastern Gulf of Alaska flow north from the

Queen Charlotte Islands, B.C., toward Prince William Sound,

Alaska, before converging to form the westward flowing Alaskan

Stream. The Alaska Current, a weak eastern boundary current

seaward of the continental shelf, is typically several hundred

kilometers wide. Over the continental slope and shelf, large

topographic features, freshwater runoff, coastal winds, and

atmospheric pressure gradients produce localized currents,

mesoscale eddies, and meanders. The resultant baroclinic

features may be intermittent and of short duration (e.g.,

Glacier Bay Plume extension; Wing 1979), seasonal (e.g., Haida

Current; Thomson and Emery 1986), or persist for more than a

year (e.g., Sitka Eddy; Tabata 1982). Interannual variability

of the strength and duration of these features may contribute

to variations in Southeast Alaska salmonid (Oncorhynchus spp.)

migration patterns (Hamilton and Mysak 1986) and to year-class

strength of groundfish along the British Columbia and Alaska

coasts (Tabata 1982; Thomson and Emery 1986; Karinen and Wing

1987).

Systematic observations of oceanographic variables in the

Gulf of Alaska during December through March have been

infrequent, with few stations sampled east of long. 140°W and

over the continental shelf between lat. 54° and 59°N (Tabata

1982). This area of the Gulf of Alaska includes important

winter spawning grounds of Pacific halibut, Hippoglossus

stenolepis (Thompson and van Cleve 1936), and sablefish,

Anoplopoma fimbria (Bracken 1982). Sablefish spawn from

January to March along the British Colombia continental slope

(Kendall and Matarese 1987); and probably the same or slightly

later in Southeast Alaska. Because the spawning biology of

sablefish and the oceanography of this critical habitat are not

understood, the January-February 1986 cruise of the NOAA

research vessel Miller Freeman investigated oceanographic

conditions and the reproductive state of sablefish at the

beginning of their spawning season. Examination of

trawl-caught sablefish during the cruise revealed that few

female sablefish had reached spawning condition. Plankton

sampling (neuston tows and oblique bongo net tows to 300 m)

during the cruise captured no sablefish larvae and only

2 sablefish eggs. This report presents results of

conductivity-temperature-depth (CTD) profile observations

during the cruise, giving evidence for the absence of the Sitka

Eddy in January 1986 and the presence of a warm northwardflowing subsurface current along the continental slope.
2

DATA AND METHODS

Seven days (28 January through 3 February 1986) were

devoted primarily to oceanographic profiling and

ichthyoplankton sampling east of long. 139°30'W between lat.

56°30' and 58°OO'N. Thirty-two stations were positioned on a

30' longitude by 30' latitude grid (Fig. 1) to provide coverage

of both the continental shelf and the assumed Sitka Eddy area.

Oceanographic profiles were obtained with Plessey Model

6040' CTD units and recorded on nine-track data tapes and

analog strip charts. The quality of CTD observations was

monitored throughout the cruise by sampling with Niskin bottles

equipped with reversing thermometers. The CTD casts were made

to 1,000 m at stations beyond the continental shelf break and

to within 10-15 m of the sea bottom (sea conditions permitting)

over the continental shelf.

The CTD data tapes were analyzed for computation of

salinity, temperature., density (measured as sigma-t), and

dynamic height values by the National Ocean Service, Ocean

Assessments Division, Alaska Office. Specialized computer

programs were used to graph salinity, temperature, and sigma-t

profiles with l-m resolution for each station (Appendix);

salinity, temperature, and sigma-t sections for each east-west

transect; and contour plots of sea surface temperature and

dynamic height topography.

During the survey, surface waters were generally well

mixed with isopycnal conditions from the surface to 50-150 m.

Beyond the continental shelf, mixed-layer temperatures were

5.7°-6.3°C, salinities were 32.50-32.75%, and sigma-t was less

than 25.75 (Figs. 2-5). Below the surface layer was a strong

pycnocline characterized by a 1% salinity increase over

approximately 50 m. Weak subsurface temperature maxima of

6.5°-7.1°C at or near the pycnocline were observed at most

stations beyond the continental shelf break. Along the

continental slope, the pycnocline was not as sharply defined as

it was further offshore. Below the pycnocline, temperatures

decreased with depth to a low of about 3.5°C, salinities

increased to near 34.30%, and sigma-t increased to between

27.26 and 27.45 at 900-1,000 m.

'Reference to trade names does not imply endorsement by the National Marine

Fisheries Service, NOAA.
3

Figure 1. --Location of oceanographic stations occupied by

the RV Miller Freeman, 27 January-4 February 1986.

(--- = 200 m contour, -- = 2,000 m contour,

Sitka Eddy, when present.)
4

Visual examination of the east-west sections (Figs. 2-5)

did not reveal evidence of the Sitka Eddy during the survey

period. The Sitka Eddy is characterized by a warm temperature

core with a strong depression of the halocline and pycnocline

at the center of the eddy (Tabata 1982). Sea-surface property

contours (Fig. 6) and dynamic height contours (Fig. 7) do not

show evidence of the eddy. The dynamic height contours

indicated a general northwesterly flow at 0, 150, and 300 m.

The most prominent oceanographic feature during the cruise

was a subsurface current flowing northwest along the

continental slope. This current was evident by relatively warm

(6.5°-7.1°C) thermal maxima at about 125-150 m (Figs. 2-5). At

stations nearest to the continental slope, the thermal maximum

appeared to be associated with the top. of the pycnocline at the

25.75 sigma-t surface; although farther offshore the maxima

were closer to the 26.2 sigma-t surface. Core temperatures

within this current decreased from south to north. The dynamic

height anomaly of the 150 decibar surface relative to the

1,000 decibar surface (Fig. 7B) shows this current was

strongest at about long. 137°W. The subsurface current did not

intrude onto the shelf, thus the continental slope appears to

form its eastern boundary. The western boundary of the current

may be 80-90 km west of the shelf break where salinity and

sigma-t contours rise slightly toward the surface. Because CTD

casts were to a maximum depth of only 1,000 m, and stations

were approximately 30 km apart along the transects, it was not

possible to define a surface of no motion from which to

determine the velocity of this current. If levels of no motion

are assumed at 900 m at lat. 56°30'N and 500 m at lat. 57°30'N,

I estimate current velocities of 32 and 19 cm/sec, respectively.

DISCUSSION

Sitka Eddy

The Sitka Eddy may form as early as January-February or as

late as June-July (Mysak 1985). Although the eddy does not

form each year, it may have a life span of 10 to 17 months when

present (Tabata 1982). Initially the Sitka Eddy could

transport planktonic eggs and larvae offshore and eventually

return them to the area near the point of entry. In the

absence of the Sitka Eddy, any transport of sablefish eggs and

larvae away from suspected spawning areas is probably a result

of currents along the upper continental slope.
5

Figure 2. --Contours of temperature (A), salinity (B),

and density as sigma-t (C) along section at

lat. 58°00'N, January 1986.
6

Figure 3. --Contours of temperature (A), salinity (B),

and density as sigma-t (C) along section at

lat. 57°30'N, January 1986.
7

Figure 4. --Contours of temperature (A), salinity (B),

and density as sigma-t (C) along section at

lat. 57°00'N, January 1986.
a

Figure 5. --Contours of temperature (A), salinity (B),

and density as sigma-t (C) along section at

lat. 56°30'N, January-February 1986.
9

The most recent intensive coverage of the southeastern

Alaska coast was the Gulf of Alaska Survey (GAS) by the United

Stated Coast Guard vessel Campbell in September 1976. Eleven

transects (118 stations) were surveyed between the Queen

Charlotte Islands, British Columbia, and Yakutat, Alaska. The

Sitka Eddy may have been present in September 1976, as shown by

depressed salinity and sigma-t contours on three transects

between Sitka and Cape Spencer, Alaska, although the warm core

was not present.

Source of Subsurface Current

The subsurface slope current present in January-February

1986 may be a seasonal feature of the eastern Gulf of Alaska

and the Alaska Current, or, like the Sitka Eddy, may be

intermittent. The subsurface maxima which characterize the

slope current were not present in the GAS data, but they have

been noted in winter profiles from the eastern Gulf of Alaska

(Robinson 19573. Similar phenomena are observed in the western

Gulf of Alaska. There are neither sufficient seasonal nor

historical data to definitively identify the origin of the warm

water along the continental slope in January 1986. Possible

sources are the California Undercurrent, the Alaska Current,

and the Haida Current.

California Undercurrent

The California Undercurrent does not appear to be a likely

source, although it is believed to flow with the Alaska Current

from Canada to the Aleutian Islands (Reid 1965). The

California Undercurrent has been identified as far north as

Dixon Entrance (Gardner 1982) and may contribute to the Alaska

Coastal Current (Cooney and Coyle 1985). Wooster and Jones

(1970) and Gardner (1982) report the California Undercurrent's

warm, high salinity, low oxygen core to be associated with the

26.54 sigma-t surface at approximately 200-250 m. Although the

California Undercurrent may surface in the winter as the

Davidson Current, its salinities appear to be too high to be

the Alaskan subsurface current, which has a core at about the

25.8 sigma-t suface.

2USCG Oceanographic Unit, unpubl. data. 1977. Washington, D.C. USCG

Oceanographic Unit Bldg. 159 E. Navy Yard Annex, Wash. D.C. 20590.

3

Dr. D. Musgrave, School of Fisheries and Ocean Sciences, Univ. of Alaska

Fairbanks, 905 Koyukuk Ave., Fairbanks, AK 99775-1080, pers. commun., August

1991.


12

Maska Current

The Alaska Current is a relatively weak, broad current

flowing northward beyond the continental shelf and forming the

eastern boundary of the Alaska Gyre. The Alaska Current draws

its surface thermal and salinity properties from the eastern

Subarctic Current and Dilute Domain of Favorite et al. (1976).

During much of the spring and summer, it can be recognized as a

warm, high salinity tongue extending northward along the

26.2 sigma-t surface (Barkley 1968) and at the surface as an

offshore warm water tongue. This warm-water tongue associated

with the Alaska Current has an axis 160-480 km offshore, and is

present in all months (Robinson 1957). In the winter, the

warm-water tongue is evident as a positive thermal gradient

near 125 m. Robinson's winter thermal profiles of the Alaska

Current are most similar to the profiles observed in JanuaryFebruary 1986 at those stations 80-160 km offshore. Published

data are too sparse to determine if the subsurface slope

current is a winter intensification of the Alaska Current,

although the sharp decline of the pycnocline between stations

12 and 13 (Fig. 3C) and between stations 30 and 31 (Fig. 5C)

may mean that the two currents are separate and that, on the

average, the Alaska Current was centered 80 km west of the

slope subsurface current.

Haida Current

The subsurface current observed in January-February 1986

may be the Haida Current described by Thomson and Emery (1986).

Thomson and Emery (1986) do not detail the subsurface

characteristics of the Haida Current or its relationship to the

Alaska Current. The Haida Current is a warm-cored surface

current originating off the northern Queen Charlotte Islands.

Near-surface temperatures in the Haida Current core may be up

to l°C above with salinities 0.1% below ambient levels within

the upper 100 m. It flows northward along the continental

slope to at least the southern edge of the 1986 survey area and

may extend to Yakutat, Alaska. The Haida Current appears to be

only 20-30 km wide, extending from the surface to about 500 m.

It develops during the winter between October and April and has

its maximum flow (15-25 cm/sec) from November through February.

When present, the Haida Current occupies approximately the same

position as the warm-cored subsurface current in the 1986 data.

The 0.5°-l°C surface temperature elevation of the Haida

Current was not present in 1986. The 30-km interval of our

stations, however, may have missed the narrow surface

manifestation of the Haida Current. Additionally, as the Haida

Current flows northward, it will mix with surrounding waters

and have a weaker surface signature at its northern extent.

Alternatively, strong storm conditions providing heavy

freshwater runoffs from the adjacent coastal areas may have

diluted the surface signature of the Haida Current. Ingraham
13

(1979) indicates that in the summer, coastal dilution extends

throughout the survey area. Although coastal dilution is

usually minimal during the winter, the months preceding the

January-February 1986 survey were characterized by above

average temperatures and precipitation (DOC 1986, 1987).

December 1985 and January 1986 had record or near-record high

runoffs that exceeded the average peak spring runoffs

(VanMaanen et al. 1988). These conditions may have resulted in

freshwater runoffs equivalent to summer conditions. Strong

storms prior to and during the cruise, with concomitant wind

mixing, could have produced isopycnal surface conditions, thus

removing features of the Haida Current above 100 m.

The Haida Current may have a major influence on the

groundfish fisheries of the continental slope area by affecting

development and feeding rates of larvae, juveniles, and adult

fishes by raising the water temperatures at the upper edge of

the slope. The eggs of winter spawning Pacific halibut and

sablefish could be carried 15-30 km per day by the current.

Sablefish eggs are believed to have an incubation period of

2-3 weeks (Kendall and Matarese 1987); thus, hatching areas

could be considerably distant from spawning areas, depending on

the strength of the current. Interannual variation of these

currents may be one of the factors determining whether or not

larval fish are transported to nursery areas.

SUMMARY

In late January and early February 1986, oceanographic

conditions in the eastern Gulf of Alaska were characterized by

well-mixed surface waters in the upper 50-100 m. Temperatures

within the surface layer ranged from 5.5° to 6.3°C, being

coldest near shore and at stations farthest offshore.

Salinities in this layer were generally 32.50-32.75% offshore

and less than 32.50% over the continental shelf. Below the

isopycnal surface layer, the permanent pycnocline at 100-150 m

was strongest at stations west of the continental slope and

weakest over the slope. In the pycnocline, thermal maxima of

6.5°-7.0°C were present. Below the pycnocline, temperature

decreased with depth from 6.0° to 3.5°C and salinities

increased from 33.75 to 34..30% at 1000 m.

The observed distributions of temperatures and salinities

indicate that the Alaska Current was 80-160 km offshore and

that a northward flowing subsurface current was present at

100-300 m along the continental slope. The relationship of

this subsurface current to the Alaska Current is not known. It

may be a subsurface manifestation of the Haida Current, which

forms in the winter and flows northward from the Queen

Charlotte Islands along Southeast Alaska.
14

ACKNOWLEDGMENTS

I thank the crew of the NOAA research vessel Miller

Freeman for courtesies extended during the cruise. Survey

Technicians Carol Dewitt and Daniel Dougherty took all the CTD

casts and associated physical observations. Dr. David A. Hale,

National Ocean Service (Office of Oceanography and Marine

Assessment, Ocean Assessments Division, Alaska Office,

Anchorage), edited the CTD data tapes and prepared the initial

computer graphics displaying the data. Drs. James Schumacher

and Ronald Reed of the NOM Pacific Marine Environmental

Laboratory and Drs. David Musgrave and Thomas Royer of the

Institute of Marine Sciences, University of Alaska Fairbanks,

reviewed the manuscript and gave valued suggestions on

presentation and interpretation of the data.
15

CITATIONS

Barkley, R. A. 1968. Oceanographic atlas of the Pacific

Ocean. Univ. Hawaii Press, Honolulu, 176 p.

Bracken, B. E. 1982. Sablefish (Anoplopoma fimbria) migration

in the Gulf of Alaska based on gulf-wide tag recoveries,

1973-1981. Info. Leaf. 199, 24 p. Alaska Dep. Fish Game,

Div. Commer. Fish., Box 667, Petersburg, AK 99833.

Cooney, R. T., and K. Coyle. 1985. The occurrence of the

subtropical copepod, Mesocalanus tenuicornis, in Columbia

Bay, Prince William Sound, Alaska. Crustaceana 49(3):310-

313.

Favorite, F., A. J. Dodimead, and K. Nasu. 1976. Oceanography

of the Subarctic Pacific Region, 1960-71. Int. North Pac.

Fish. Comm. Bull. 33. 187 p.

Gardner, G. A. 1982. Biological and hydrographical evidence

for Pacific equatorial water on the continental shelf

north of Vancouver Island, British Columbia. Can. J.

Fish. Aquat. Sci. 39:660-667.

Hamilton, K., and L. A. Mysak. 1986. Possible effects of the

Sitka Eddy on sockeye (Oncorbynchus nerka) and pink salmon

(Oncorhynchus gorbuscha) migration off Southeast Alaska.

Can. J. Fish. Aquat. Sci 43:498-504.

Ingraham, W. J., Jr. 1979. The anomalous surface salinity

minima area across the Northern Gulf of Alaska and its

relation to fisheries. U.S. Natl. Mar. Fish. Serv., Mar.

Fish. Rev. 41(5-6):8-19.

Karinen, J. F., and B. L. Wing. 1987. Age composition and

recruitment trends of Pacific ocean perch off southeastern

Alaska in 1984 and 1986. In R. L. Major (editor),

Condition of groundfish resources of the Gulf of Alaska

region as assessed in 1986, p. 139-148. U.S. Dep.

Commer., NOM Tech. Memo. NMFS F/NWC-119.

Kendall, A. W., Jr., and A. C. Matarese. 1987. Biology of

eggs, larvae, and epipelagic juveniles of sablefish,

Anoplopoma fimbria, in relation to their potential use in

management. U.S. Natl. Mar. Fish. Serv., Mar. Fish. Rev.

49(1):1-13.
16

Mysak, L. A. 1985. On the interannual variability of eddies

in the Northeast Pacific Ocean. In W. S. Wooster and

D. L. Fluharty (editors), El Nino North: Nino effects in

eastern subarctic Pacific Ocean, p. 97-106. Washington

Sea Grant Program, Univ. Washington, Seattle, W-85-3.

Reid, J. L., Jr. 1965. Intermediate waters of the Pacific

Ocean. The John Hopkins Oceanographic Studies No. 2. The

Johns Hopkins Press, Baltimore, 85 p.

Robinson, M. K. 1957. Sea temperature in the Gulf of Alaska

and the Northeast Pacific Ocean, 1941-1952. Bull. Scripps

Inst. Oceanogr. Univ. California 7(1):1-98.

Tabata, S. 1982. The anticyclonic, baroclinic eddy off Sitka,

Alaska, in the Northeast Pacific Ocean. J. Phys.

Oceanogr. 12:1260-1282.

Thompson, W. F., and R. van Cleve. 1936. Life history of the

Pacific halibut. (2) Distribution and early life history.

Rep. Int. Fish. Comm. 9, 184 p.

Thomson, R. E., and W. J. Emery. 1986. The Haida Current.

J. Geophys. Res. 91(C1):845-861.

U.S. Department of Commerce (DOC). 1986. NOAA Climatological

Data Annual Summary, Alaska 1985, 71(13):3-10.

U.S. Department of Commerce (DOC). .1987. NOAA Climatological

Data Annual Summary, Alaska 1986, 72(13):2-10.

VanMaanen, J. L., R. D. Lamke, P. J. Still, J. E. Vaill, and

B. B. Bigelow. 1988. Water Resources Data, Alaska, Water

Year 1986. U.S. Geological Survey Water-Data Report

AK-86-1, 330 p.

Wing, B. L. 1979. Satellite observations of the Glacier Bay

Plume. Coastal Ocean. Clim. News 2(1):8-g.

Wooster, W. S., and J. H. Jones. 1970. California

undercurrent off northern Baja California. J. Mar. Res.

28:235-250.
APPENDIX

Depth profiles and data summaries for stations occupied in the

eastern Gulf of Alaska, 28 January to 4 February 1986.
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