NOAA Technical Report ERL 455-PMEL 43

A Time Series of Temperature, Salinity, and

Geopotential Across the Southeastern

Bering Sea Shelf, 1995–1999

Ronald K. Reed

Pacific Marine Environmental Laboratory

7600 Sand Point WayNE

Seattle, WA 98115

September 1999

Contribution 2134 from NOAA/Pacific Marine Environmental Laboratory
NOTICE

Mention of a commercial companyor product does not constitute an endorsement

byNOAA/ERL. Use of information from this publication concerning proprietary

products or the tests of such products for publicityor advertising purposes is not

authorized.

Contribution No. 2134 from NOAA/Pacific Marine Environmental Laboratory

For sale by the National Technical Information Service, 5285 Port Royal Road

Springfield, VA 22161

ii
Contents

ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2. DATA AND METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

3. RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3.1 1995 Data . . . ................................... 3

3.2 1996 Data . . . ................................... 3

3.3 1997 Data . . . ................................... 8

3.4 1998 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.5 1999 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

4. DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5. CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

6. ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

7. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

iii
A Time Series of Temperature, Salinity, and

Geopotential Across the Southeastern

Bering Sea Shelf, 1995–1999

Ronald K. Reed

Abstract. CTD (conductivity/temperature/depth) casts were taken during sixteen

occupations of a standard section across the southeastern Bering Sea shelf during 1995–

1999. Vertical sections of temperature and salinity, plus computed geopotential anomaly

values, are presented here. Water temperatures varied from ∼ –1 to 10◦C, and salinities

varied from ∼31.3 to 33.1. Nontidal flow was organized but was generally <5 cm s−1. Six

sections were obtained during 1997, a year with considerable sea ice. The melting sea ice

produced low salinity (<31.4) that altered geopotential gradients inshore and reversed the

typical southeastward geostrophic flow. Thus these waters are subject to large seasonal

changes and occasional marked interannual ones.

1. INTRODUCTION

The southeastern Bering Sea shelf is a vast region with a distance of nearly300 km

between the 50- and 200-m isobath (Fig. 1). Coachman (1986) noted that this shelf is the

widest outside the Arctic. The nontidal currents inshore of the 150-m isobath seldom exceed

5 cm s−1 (Schumacher and Kinder, 1983; Coachman, 1986; Reed and Stabeno, 1996). The

region is also unusual, besides having the wide shelf and weak flow, as a result of large

seasonal changes in water and air temperatures and wind forcing. Sea surface temperatures

typically range from about –1 to 10◦C over the years; bottom temperatures vary from ∼ –1

to 7◦C (Reed, 1995). Salinityincreases downward from about 31.2–32.5 at the surface to

31.4–33.0 at the bottom (Reed, 1995).

The main factor determining water temperatures over the shelf is the amount of sea ice

in the previous winter–spring (Coachman, 1986; Neibauer, 1988; Neibauer and Day, 1989).

Swan and Ingraham (1984) presented bottom-water temperature anomalies during 1950–

1982. In this data set, 1976 was the coldest year. Neibauer and Day (1989) attributed

most of the sea-ice variabilityto atmospheric, not oceanic, forcing. The winter position

of the atmospheric Aleutian Low was found to explain up to 40% of the variations. This

mode of variabilitywas found to be linked to El Ni ̃no–Southern Oscillation events, however.

During summer (July–August), with typical light winds, changes in heat content of the water

over the shelf are dominated byinsolation; at other times, latent and sensible heat flux are

important (Reed, 1978).

In early1995, as part of the Fisheries OceanographyCoordinated Investigations of NOAA’s

Coastal Ocean Program, moorings were established to measure currents and physicalbiological variables (Stabeno et al., 1998) at two sites (M2 and M3; Fig. 1). Along this line,
0.23

0.22

0.21

0.15

168°W 167° 166° 165° 164°

57°N

56°

55°

Bering

Sea

ALASKA

Alaska Peninsula

Aleutian Is.

M2

M3

100 m

200 m

0.147

0.145

0.147

0.150

0.153

0.156

0.156

0.240

0.238

0.232

0.224

0.222

0.210

0.200

100 m

1000 m

50 m

Pribilof Is.

Figure 1. The location of CTD sections used here, 1995–1999, and the sites of current

moorings (M2 and M3). The open circles indicate the location of stations, with mean

computed geopotential anomalies at the sea surface, referred to 60 or 100 db, on the

PROBES line, spring 1979–1981.

with extensions to the northeast and southwest, CTD (conductivity, temperature, depth)

casts have been made on sixteen cruises (1995–1999). These data provide a time series

of temperature, salinity, and geopotential over this period and are used here to examine

ocean conditions and their variability. A similar analysis of geopotential (Reed, 1998) was

performed on data from the nearbyPROBES (Processes and Resources of the Bering Sea;

Coachman, 1986) line, which is also shown in Fig. 1.

2. DATA AND METHODS

CTD casts were made at lowering speeds of 15–30 m min−1. The data are thought to be

accurate to at least 0.01◦C and 0.01 in salinity. Each occupation of this CTD line took five

days or less; thus the data are essentially synoptic. Data from each cast were examined to

ensure against spurious values, such as densityinversions. The use of dual temperature and

salinitysensors reduced significant data gaps and helped verifydata quality.

2
A computed quantity, geopotential anomaly (in dynamic meters, dyn m, which has units

of 105 erg g−1) is shown at each station on the location map of each figure. These values are

for the sea surface, referred to 60 db (decibars; 1 db ∼= 0.98 m) inshore of 100 m, and referred

to 100 db offshore of 100 m. Directions of flow computed from the anomalyvalues, assuming

a balance between pressure gradient and Coriolis accelerations, are shown byarrows on the

maps. The location of the stations on the temperature and salinitysections were produced

bydownward extrapolation of longitude.

3. RESULTS

Data from 16 cruises during 1995–1999 are presented in Figs. 2–17 below.

3.1 1995 Data

Figure 2 shows the location map, with station numbers and computed geopotential anomalies, for 12–14 March 1995. It was the onlysection occupied in 1995. Onlyabout half of the

planned stations were taken because of operational constraints. The arrows indicate even

numbers of geopotential anomaly, as discussed above, based on the tendency for motion to

start from high to low values and turn to the right. There are oppositelydirected values of

0.13 dyn m, suggesting an eddy-like feature, and a value of 0.14 dyn m toward the southeast.

On the temperature and salinitysections (Fig. 2), the inverted “T” for station 8 at 75 db

indicates that there were no temperature or salinitydata below that level; at station 15,

the “T” indicates no data above 20 db. The temperature section shows that the lowest

temperatures (<0◦C) were at station 15; the highest temperatures were >4◦C at station 6.

Salinityvaried from <31.8 to >32.8. Our occupation of the section in mid-March, however,

was not during the most extreme winter conditions. These were in late March–earlyApril,

when much of the shelf was ice-covered (Stabeno et al., 1998). It now appears clear that

1995 was an extensive ice year, but that the cold conditions were short-lived (Stabeno et al.,

1998).

3.2 1996 Data

Three sections were occupied in 1996. Again, however, none were taken over the complete

planned section. Figure 3 shows conditions during 13–15 February1996. Offshore, nearbottom waters were warmer than 5◦C; the coldest waters inshore were less than –0.5◦C.

In offshore waters, a strong halocline coincided with the sharp thermocline there. Inshore

salinities were slightlyless than in March 1995 (Fig. 2), possiblyas a result of some melting

ice prior to the observations. A southeastward flow is indicated in Fig. 3 near 56.5◦N, 165◦W.

This is much like the southeastward flow from the mean of spring PROBES data (Fig. 1).

Reed (1998) concluded that this feature likelyresults from the northwestward offshore flow

approaching shoal water near the Pribilof Islands and retroflecting back toward the southeast

3
57°N

56°

13 0.135

12 - 14 Mar 95

6

0.234

8

0.144

0.132

12

0.131

10 0.127

7

0.234

0.14

0.13

11

168° 166° 164°W

0

db50

100

0

db50

100

6

S

11 13 10 12 7 15

32.0

32.2

8

32.0

32.6

32.8

32.4

T(°C)

T

T

7 8 13 12 10 11

2

4

15 6

1

3

2

0.5

0

T

T

15

0.13

Figure 2. Vertical sections of temperature (◦C)

and salinitywith station locations and sea-surfacegeopotential anomalies (dyn m), referred to 60 or100 db, 12–14 March 1995.

57°N56°

12

13

0.142

13 - 15 Feb 96

5

0.253

6

3

0.264

0.265

0.254

8

0.150

9

0.151

10

0.15

168° 166° 164°W

0.150

0.147

4

0.26

0.26

0.156

0

db

50

100

5 3 10 13

5 64 9 10 12

>31.8

S

T(°C)

12 4 6

0

db50

100

3

2 1

0.5

0

-0.5

3 4 5

8 9

13 8

31.8

31.8

31.8

32.0

32.6

32.8

Figure 3. Vertical sections of temperature (◦C)

and salinitywith station locations and sea-surfacegeopotential anomalies (dyn m), referred to 60 or100 db, 13–15 February1996.

4
57°N

56°

29

26

0.151

24 - 26 Apr 96

40

0.24

39

0.236

0.248

0.152

32

0.154

31

0.150

30

0.152

0.153

168° 166° 164°W

33

0.246

0

db

50

100

40 30 26

S

T(°C)

29 33 39

0

db50

100

2 0.5

3

4

32 31

32.6

32.0

32.4

1

40 30 26 29 33 39 32 31

Figure 4. Vertical sections of temperature (◦C)

and salinitywith station locations and sea-surfacegeopotential anomalies (dyn m), referred to 60 or100 db, 24–26 April 1996.

0.183

57°N56°

6

18 - 19 Sep 96

4 0.182

5

168° 166° 164°W

9

3

0.182

7

0.186

0.278

0.184

9 345 6 79 345 6 7

0

db

50

100

0

db50

100

S

T(°C)

8

6

5

4

3

31.6

31.8

32.0

32.4

32.6

0.186

Figure 5. Vertical sections of temperature (◦C)

and salinitywith station locations and sea-surfacegeopotential anomalies (dyn m), referred to 60 or100 db, 18–19 September 1996.

5
0.228

57°N56°

168° 164°W

0.23

0.24

0.237 14

13

12

0.239

0.246

29

31

0.243

0.248

0.148 11

0.140

8

0.145

0.150 4

7

0.148

20 - 25 Feb 97

27

0

db

50

100

14 29 7 8 12 13 31 11 27 4

0

db

50

100

14 4

S

12 13 27 31 29 11 8 7

<32.0

T

0.5

3

4

>32.0

T

32.0

32.2

32.6

32.8

T(°C)

1 2

32.0

Figure 6. Vertical sections of temperature (◦C)

and salinitywith station locations and sea-surfacegeopotential anomalies (dyn m), referred to 60 or100 db, 20–25 February1997.

0

db

50

100

17 20 36 34 19 18 23 28 22

0

db50

100

17 34

S

30 19 22 25 20 28 31 36

T(°C)

25 31 33

18

29

29

30

4

3

2 1 0.5

0

-0.5

-1

23 33

32.0

31.8

31.4

31.6

32.0

32.2

32.8

57°N56°

168° 166° 164°W

0.23

0.219

0.235 17

18

20

0.238

22

0.239

25

23

0.236

0.143 28

0.140

31

0.156

0.164 34

33

19 - 21 Apr 97

0.22

0.236

29

0.140

30

0.148

0.15

0.166

36

0.161

19

0.16

0.238

Figure 7. Vertical sections of temperature (◦C)

and salinitywith station locations and sea-surfacegeopotential anomalies (dyn m), referred to 60 or100 db, 19–21 April 1997.

6
57°N

56°

168° 166° 164°W

0.23

0.222

0.232 17

19

32

0.166

35 0.162

6 - 7 May 97

0.167 36

0.16

0.24

20

0.238

21

0.244

22

24

26

0.243 0.24

0.241

0.237

27

0.140 29

0.144 30

0.149

0.15

33

0.156

0

db50

100

17 21 29 33

T(°C)

30 20 19 24 26 22 27 32 35 36

2

1 0.5 0 -0.5 3

4

4

0

db50

100

17 21 29 33

S

30 20 19 24 26 22 27 32 35 36

32.2

31.6

31.4

31.8

32.0

32.0

32.4

32.6

0.144

Figure 8. Vertical sections of temperature (◦C)

and salinitywith station locations and sea-surfacegeopotential anomalies (dyn m), referred to 60 or100 db, 6–7 May1997.

0.24

0.234

56

69

0.176

0.173

0.174 76

57

0.249

0.25 58

0.260

59

63

65

0.261

0.26 0.263

0.259

66

0.156

67

0.155

0.17 70 0.173

73

0.16

0.26

57°N56°

168° 166° 164°W

0.16

0.166

0

db

50

100

56 59 76 70 58 57 66 67 63

0

db

50

100

56 73

S

69 58 63 65 59 66 70 76

T(°C)

65 69 73

57 67

4

4

3 2

1 0.5

7 8

31.8 32.0

32.0

32.4

31.6

31.4

32.6

5

17 - 19 Jun 97

Figure 9. Vertical sections of temperature (◦C)

and salinitywith station locations and sea-surfacegeopotential anomalies (dyn m), referred to 60 or100 db, 17–19 June 1997.

7
in shoaler, inshore waters. In Fig. 3, there also seems to be a clockwise-rotating eddyas

indicated bythe 0.26 dyn m vectors. This occurs ∼20% of the time in this area (Reed, 1998).

During 24–26 April 1996 (Fig. 4), inshore waters were warmer than in mid-Februaryand

had similar salinity(Fig. 3). Offshore, near-surface waters in late April were warmer and

more saline than in mid-February(Fig. 3). Near-bottom waters offshore, however, were

cooler and fresher in April than in February. In Fig. 4, there is no indication of significant

flow except for the typical northwestward flow offshore.

Onlysix stations were occupied in mid-September 1996 (Fig. 5). Near-surface waters

were from 7 to >8◦C, and near-bottom waters were from <3 to >5◦C. There was a zone of

relativelyfresh water (<31.6) above 50 db at stations 5 and 6. There was no significant flow

at the time of this section.

3.3 1997 Data

During late February1997 (Fig. 6), inshore waters were warmer than in mid-March

1995 (Fig. 2) or in mid-February1996 (Fig. 3); inshore salinities were similar during these

periods. Offshore waters in winter were similar during 1995, 1996, and 1997 in salinity, but

1996 and 1997 (Fig. 3 and Fig. 6) were warmer than in 1995 (Fig. 2). Figure 6 also indicates

northwestward flow offshore but quite weak flow inshore.

The April 1997 section (Fig. 7) was the first in which all of the planned stations were

occupied. The four subsequent 1997 sections also had good data coverage. Figure 7 indicates

inner shelf waters that were < –1◦C and had salinity <31.4. These are quite extreme winter–

spring conditions (Reed, 1995) and resulted from ice over the shelf during late March–

earlyApril (Stabeno et al., 1999). Relativelyintense northwestward flow occurred offshore

(between stations 17 and 18; Fig. 7). The most striking feature is the northwestward flow

inshore of station 30. It results from the verylow (<31.4) near-surface salinitycaused by

melting ice (Stabeno et al., 1999). Consequently, the normal inshore southeastward flow

(Reed, 1998; Fig. 1) was reversed.

In earlyMay(Fig. 8), inshore waters were still quite cool and fresh, and a reversed,

northwestward flow also occurred inshore. Bymid-June (Fig. 9), near-surface waters everywhere were >7◦C. Inshore salinitywas still relativelylow, and northwestward flow was

present between stations 67 and 69. More typical southeastward flow did occur between

stations 65 and 66. Well-developed northwestward flow was offshore of 167◦W (Fig. 9). By

earlyJuly(Fig. 10), surface waters were mainly >9◦C, but inshore salinities were <31.6.

Weak northwestward flow was present inshore. Relativelystrong flow (11 cm s−1) occurred

between stations 16 and 17. In September (Fig. 11), near-surface waters inshore had cooled

somewhat but were still relativelyfresh. A more typical southeastward flow (Reed, 1998)

was present between stations 18 and 20.

8
0.178

57°N56°

30 0.181

3 - 4 Jul 97

31

28 0.172

29

20

0.263

0.166

22

26

27

0.184

33 0.186

35

0.255

18 0.25 0.256

19

0.162

0.168

17

16 0.255 0.228

0.26 0.261

0.17

0.18

168° 166° 164°W

4

0

db

50

100

16 19 35 31 18 17 26 27 20

0

db

50

100

S

22 30 33 28 29

1

9 8

3

2

TT

32.6

32.8

32.2

32.4

32.6

32.0

T(°C)

31.8 31.6 31.4

16 19 35 31 18 17 26 27 20 22 30 33 28 29

0.168

0.23

Figure 10. Vertical sections of temperature (◦C)

and salinitywith station locations and sea-surfacegeopotential anomalies (dyn m), referred to 60 or100 db, 3–4 July1997.

57°N56°

0.26

0.25

0.250

6

25

17

12

0.174

21 - 22 Sep 97

14

0.180 0.18

24

0.268

23

21

0.270

0.262

20

0.183

0.173

16

168° 166° 164°W

0.181

0.178

0.18

18

0.18 0.180

22

0.257

0.264

0

db50

100

26 23 16

T(°C)

18 24 25 21 22 20 17 12 14

0

db50

100

26 23 16

S

18 24 25 21 22 20 17 12 14

31.8

32.8

32.6 32.4

32.6

32.2

32.0

31.8

31.6 31.4

4

3 2

4

8 8 9

Figure 11. Vertical sections of temperature (◦C)

and salinitywith station locations and sea-surfacegeopotential anomalies (dyn m), referred to 60 or100 db, 21–22 September 1997.

9
0.15

0.25

0.252

0.243

0.152

0.143

0.139

0.14

0.147

0.144

25

23

22

21

32

26

28 57°N

56°

23 - 25 Feb 98

168° 166° 164°W

0

db

50

100

25 21 32 28

25 23 22 32 26 28

32.0

32.0

S

T(°C)

26 22 23

-0.50

0.5

1

2

3

4

0.5

0

1

-1

0

db

50

100

31.8

21

31.8 31.6

32.6

32.2

0.152

Figure 12. Vertical sections of temperature (◦C)

and salinitywith station locations and sea-surfacegeopotential anomalies (dyn m), referred to 60 or100 db, 23–25 February1998.

32.6

2

2

3

4

0

db

50

100

81 83 80 79 78 77 73 75 71 69 68 67

32.0

0

db

50

100

81 83 80 79 78 77 73 75 71 69 68 67

32.4

32.8

32.0 32.2

S

T°(C)

0.148

81

79 0.149

80

73

77

0.145

83

0.146

0.241

0.148

75

0.239 71

0.232 69

0.229 68

0.222 67

0.223

78

0.146

0.242

0.23

0.24

57°N56°

25 - 26 Apr 98

168° 166° 164°W

Figure 13. Vertical sections of temperature (◦C)

and salinitywith station locations and sea-surfacegeopotential anomalies (dyn m), referred to 60 or100 db, 25–26 April 1998.

10
57°N

56°

10 0.147

2 - 4 May 98

22

0.148

12 0.149

11

168° 166° 164°W

16

0.240

18

0.240

21

13

7

0.144

0.143

3

>2 2

2 3

0

db

50

100

16 18 21 13 12 11 10 22 7 3

16 18 21 11 10 22 7 3

< 32.0

32.0

>32.0

32.0

32.2

32.4

S

T(°C)

0

db

50

100

0.147

0.240

Figure 14. Vertical sections of temperature (◦C)

and salinitywith station locations and sea-surfacegeopotential anomalies (dyn m), referred to 60 or100 db, 2–4 May1998.

5

0.177

57°N

56°

10

2 - 4 Oct 98

12 0.177

11

168° 166° 164°W

14

13

0.178

8

0.242

16

15

0.256

0.181 0.18

17

18 0.247

0.242

0.26

0.25 0.265

0.18 0.180

0

db

50

100

18 17 16 15 13 12 11 10 8

0

db50

100

18 17 16 15 14 13 12 11 10 8

T°(C)

S

14

4

6

8

7

5

8

32.0

31.8

32.4 32.6

32.8

33.0

0.178

Figure 15. Vertical sections of temperature (◦C)

and salinitywith station locations and sea-surfacegeopotential anomalies (dyn m), referred to 60 or100 db, 2–4 October 1998.

11
0

db

50

100

14 13 12 11 10 6 7 5

4

5 5

3

2

4

1

1

0

db

50

100

32.0

<32.0

32.2 32.4

32.6

32.8

T°(C)

SS

8 -10 Feb 1999

57°N

56°

0.21

0.218 14

13

1

0.140

12

0.23

11

10

6

7

0.237

5

0.139

4

0.135

168° 166° 164°W

0.208

0.22

0.225

0.230

0.240

0.234

0.140

-0.5

0.5 0

14 13 12 11 10 6 7 5 4 1

Figure 16. Vertical sections of temperature (◦C)

and salinitywith station locations and sea-surfacegeopotential anomalies (dyn m), referred to 60 or100 db, 8–10 February1999.

-0.5

0.138

57°N56°

46 0.138

3 - 8 May 99

2

44 0.139

45

168° 166° 164°W

0.220

35

37

0.225

0.227

39

43

0.146

4 60.146

0.207

31 0.208

32

0.216

33

0.21

0.22

0.222

34

0.137

0.138

0

db

50

100

31 32 33 34 35 37 39 44

2

3

1

0.5 0

43 45 46 2 4 6

0

db

50

100

31 32 33 34 35 37 39 44 43 45 46 2 4 6

31.8

32.0

32.2 32.4

32.6

32.8

33.0

T°(C)

S

3

0.136

0.14

Figure 17. Vertical sections of temperature (◦C)

and salinitywith station locations and sea-surfacegeopotential anomalies (dyn m), referred to 60 or100 db, 3–8 May1999.

12
3.4 1998 Data

During late February1998 (Fig. 12), near-surface waters were generallycool (<0.5◦C)

from inshore to the central shelf at ∼90 m depth; theywere not especiallyfresh, however.

This section onlyhad seven stations, but there was both northwestward and southeastward

flow. In late April 1998 (Fig. 13), waters were fairlywarm and saline in comparison with

April 1996 (Fig. 4) and April 1997 (Fig. 7). Flow was weak, except offshore of 100 m. The

section during 2–4 May1998 (Fig. 14) was incomplete, but the data show water properties

much like Fig. 13; geostrophic flow was insignificant everywhere. In early October 1998

(Fig. 15), upper waters were more saline than in fall 1996 (Fig. 5) or fall 1997 (Fig. 11), but

1998 upper waters were relativelycool. Figure 15 shows weak southeastward flow inshore

and northwestward flow offshore.

3.5 1999 Data

The inshore part of the February1999 section (Fig. 16) was incomplete; offshore waters

were relativelywarm and saline compared with 1996 (Fig. 3), 1997 (Fig. 6), or 1998 (Fig. 12).

There was no significant flow in February1999 (Fig. 16), except offshore of ∼140 m, where it

was toward the northwest. In earlyMay1999 (Fig. 17), the section was complete. Offshore

deep waters were cooler and more saline than in February1999 (Fig. 16).

4. DISCUSSION

The first five sections presented here were incomplete because of operational constraints;

most of the remaining sections were largelycomplete, however. In general, the data show

the effects of seasonal warming from winter into earlyfall. Seasonal effects on salinityseem

limited here as well as in Reed (1995).

Interannual effects can be pronounced. Although both 1995 and 1997 were substantial

“ice years” (Stabeno et al., 1999), we onlyhave one section in 1995, and it was before the

onset of ice. Observations in 1997 (Figs. 6–11), however, show the effects of ice through much

of the year. The most noticeable effect is persistent low salinity over the inner shelf. As seen

in Figs. 7–11, the low-salinitywater was present into earlyfall. The effect of the low-salinity

water reversed the normal (southeastward) inshore flow. This southeastward flow seems to

be a retroflected branch of the offshore northwestward flow that “feels bottom” near the

Pribilof Islands and turns southeastward (Reed and Stabeno, 1996; Reed, 1998). Although

1995 and 1997 were substantial ice years, they were not as severe as 1976 (Stabeno et al.,

1999).

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5. CONCLUSIONS

The data presented here provide additional information on water propertydistributions

during the period 1995–1999. The observations were along a single line across the southeastern Bering Sea shelf from water depths of ∼70 to ∼140 m. Although the data were

not distributed evenlyin time, some data are available over all months except August and

November–January.

Water temperatures varied from ∼ –1 to 10◦C; salinityranged from ∼31.3 to 33.1.

Geostrophic speeds were mainly <5 cm s−1, but a value of 11 cm s−1 was obtained from

earlyJuly1997. Substantial changes occurred during 1997 as a result of sea ice. Salinity

was as low as 31.3. The normal inshore southeastward geostrophic flow reversed as a result

of the persistent dilute water. Although net, nontidal circulation over the shelf is weak, it is

not constant.

6. ACKNOWLEDGMENTS

I thank Phyllis Stabeno for support, suggestions, and insight. I thank Sheri Rees for

preparing data products that accelerated preparation of this report. David Kachel also

provided considerable assistance. Carol DeWitt, David Kachel, William Floering, Sheri

Rees, and Sigrid Salo collected data at sea. Shipboard observations were conducted aboard

the NOAA Ship Miller Freeman and the R/V Wecoma. Program support was provided

byNOAA’s Coastal Ocean Program, Southeast Bering Sea Carrying Capacity. This is

contribution FOCI-B373 to the Fisheries OceanographyCoordinated Investigations.

7. REFERENCES

Coachman, L.K., 1986. Circulation, water masses, and fluxes on the southeastern Bering Sea shelf.

Cont. Shelf Res. 5:23–108.

Neibauer, H.J., 1988. Effects of the El Ni ̃no–Southern Oscillation and North Pacific weather patterns on interannual variability in the subarctic Bering Sea. J. Geophys. Res. 93:5051–5068.

Niebauer, H.J., and R.H. Day, 1989. Causes of interannual variability in the sea ice cover of the

eastern Bering Sea. GeoJournal 18:45–59.

Reed, R.K., 1978. The heat budget of a region in the eastern Bering Sea, summer 1976. J. Geophys.

Res. 83:3636–3645.

Reed, R.K., 1995. Water poperties over the Bering Sea shelf: climatology and variations. NOAA

Tech. Report ERL 452-PMEL 42, 15 pp.

Reed, 1998. Confirmation of a convoluted flow over the Bering Sea Shelf. Cont. Shelf Res. 18:99–103.

14
Reed, R.K., and P.J. Stabeno, 1996. On the climatological mean circulation over the eastern Bering

Sea shelf. Cont. Shelf Res. 16:1297–1305.

Schumacher, J.D., and T.H. Kinder, 1983. Low-frequency current regimes over the Bering Sea shelf.

J. Phys. Oceanogr. 13:607–623.

Stabeno, P.J., J.D. Schumacher, R.F. Davis, and J.M. Napp, 1998. Under-ice observations of water

column temperature, salinity and spring phytoplankton dynamics: Eastern Bering Sea shelf. J.

Mar. Res. 56:239–255.

Stabeno, P.J., N.A. Bond, N.B. Kachel, S.A. Salo, and J.D. Schumacher, 1999. On the temporal variability of the physical environment over the southeastern Bering Sea. Fish. Oceanogr.

(submitted).

Swan, N.P., and W.J. Ingraham, Jr., 1984. Numerical simulation of the effect of interannual temperature fluctuations on fish distribution in the eastern Bering Sea. NOAA Tech. Memo. NMFS

N/NWC-57, NOAA National Marine Fisheries Service, Seattle, WA, 60 pp.

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