INFLUENCE OF THE YUKON RIVER ON THE BERING SEA 

K. Dean and C. P. McRoy 

As specified by the contract this is the annual progress report 

concerning NAS 5-28769 entitled, "Influence of the Yukon River on the Ber 

Sea". The purpose of this project is to use satellite data to study 

relationships between discharge of the Yukon River to currents and biolog 

productivity in the northern Bering Sea. 

C 

Amended specific objectives are: 

1. 

2. 

3. 

to develop thermal, sediment and chlorophyll surface maps using TM 

data of the discharge of the Yukon River and the Alaska Coastal 

Current during the ice free season; 

to develop a historical model of the distribution of the Yukon River 

discharge and the Alaska Coastal Current using Landsat MSS and NOAA 

sate 11 i te imagery; and 

to use high resolution TM data to define the surface dynamics of the 

front between the Alaska Coastal Current and the Bering Shelf/Anadyr 

Current. 

Landsat MSS and TM, and AVHRR data were recorded during the 1985 ice-free 

period. The satellite data coincided with shipboard measurements acquired by 

ISHTAR project scientists (ISHTAR: 

NSF funded project in the area). 

Inner Shelf Transfer and Recycling is an 

Circumstances were such, that on July 5 and 

July 22, all three sensors recorded data creating a unique data base for 

analysis. The remote sensing data has been registered to a common map 

projection and map base, then contrast stretched, color composi ted, and 

density sliced. 

(hASA-CH-180065) INELUEbCE CI TEE YUKCN dd7- 1629 3 

FIVER CN 2BE kE61IiG SEA Annual kroqrcss 

ReFort (Alaska Univ., Auchcraqe.) 15 p 

CSCL 08C irnclas 

G3/48 43195 
. 

Distinct water masses and turbid water were delineated on the satellite 

data. AVHRR data, thermal infrared band, provide a synoptic perspective of 

the northern Bering sea. 

coastal water, cooler shelf water and a cold up-welling near the Siberian 

coast can be observed (fig. 1). 

The extent and boundaries of the warm Alaskan 

The location of the currents observed on the imagery were compared to 

measurements in the water column acquired by ISHTAR project scientists 

(fig. 2). 

to the distribution of chlorphyll and nutrients measured in the water 

column. For example, the largest concentration of surface chlorphyll and 

nitrate that were measured (fig. 3 & 4) are located along the boundary and 

east of the cold up-welling near Siberia (fig. 1). Large concentrations of 

chlorophyll also occur along the boundary of the Alaska Coastal Current. 

Turbid water, mostly derived from the Yukon river, has been analyzed on the 

imagery as previosuly reported in the first progress report. An integrated 

model of changes in the distribution of the water masses during the ice-free 

period has also been compiled. 

The distribution of the remote-sensing-derived water masses relate 

.A 

Digital bathymetric data was acquired of the northern Bering Sea, and 

sea-bottom contours and perspective views were generated. 

closely related to the boundaries of the water masses. 

sea-surface temperatures recorded on AVHRR data were also contoured and 

perspective views generated (fig. 5). 

Bathymetry is 

The turbid water and 

TM data has been analyzed and enhanced images displayed at reduced 

resolution. Reduced resolution was utilized so that software could be refined 

and analysis techniques tested. Even though the TM resolution has been 
degraded, the thermal infrared band provides detailed information concerning 

oceanic circulation that AVHRR data could not dectect (fig. 6). The TM data 

will be analyzed at full resolution in the near future. 

Presently, the relationship bebeen the interannular distribution of 

turbid water discharged by the Yukon River and meteorologic, hydrologic, 

oceanic and geologic factors are being analyzed. The results of this analysis 

are being prepared to be published in a refereed journal. 
Figure 1. Density slice of AVHRR thermal infrared image recorded on 3 August 

1985. The boundary between the Alaska Coastal water mass (red-orange-yellow) 

and the Bering Shelf/Anadyr water mass (blues-green) is distinct and related 

to bathymetry and ship-board measurements of biological and chemical factors 

in the water column. A cold up-welling (dark blue) is present near the 

Siberian coast, lef t-cen ter . 

Figure 2. 

Shipboard sampling stations are positioned on the image. 

Contrast stretch of AVHRR visible image recorded on 7 July 1985. 

.. 

Figure 3. Integrated surface chlorphyll measured by ISHTAR investigators in 

1985. High values measured in early summer are located at the boundary of the 

cold, Siberian upwelling and at the boundary of the Alaska Coastal Current 

(fig. 1). These values rapidly decrease shoreward of the boundaries. 
Norton Sound _I ..I I kll I 

I uruiu vvaier. VISIUI~ nvnnn uaia, I-LL-oa 

Norton Sound 

I 

athymetry: 5 min. grid 

URFACES OF WATER: Nc 

.. 

. 

Figure 4. Surface nitrate measured by ISHTAR investigators in 1985. High 

values are located at the boundary of the cold Siberian upwelling. 

values rapidly decrease away from the boundary. 

These 

.. 

Figure 5. 

highly turbid water to the south (right) and a shallow water and low 

bathymetric gradient compared to the north (left) is at least partly caused by 

sediments discharged by the Yukon River. 

Perspective view of bathymetry and turbidity in Norton Sound. The 
Figure 6. Comparison of sea surface temperatures measured by TM and AVHRR 

data acquired on the same day. The high resolution of TM records subtle 

detai Is concerning oceanic circulation.