RESUL4TS AND DISCUSSION OCEANOGRAPHY

Water-level monitoring for 65 days in 2000 and 58 days in 2001 revealed peak water surface elevations of 1.0 m and 0.5 m above mean sea level, respectively (Figure 2). Mean daily tidal variations were 0.31 m i n 2000 and 0.29 m in 2001. Seasonally, high tides varied by 0.3 to 0.5 m on a weekly basis depending on atmospheric conditions.

The unusually high water levels on 11 and 12 August 2000 were the result of a severe storm that originated over northem Siberia, tracked east over the Chukchi Sea, and then moved to the northeast into the Beaufort Sea. The National Weather Service reposted a sustained wind at 54 mph and a peak wind at 64 mph between 3 and 5 P M at Bassow, and 38-mph sustained winds, with gusts to 54 mph at 7 AM on August 1 1 , at Barter Island. At Bastes Island, the storm caused damage to homes and flooding of the airport runway. A recent driftline at Transect l had a maximum elevation of 1.1 m and presumably resulted from the 2000 storm.

The coastal bluffs are protected by a long barrier island System extending from the mouth of the Kongakut River to Camden Bay. Fetch distances for wave development from northeast winds for Transects 1-3 are 2750 m,1980 m, and 2600 m respectively. Spit development evident on the aerial photography is to the northwest, indicating dominant northwest flow of water. Two measurements of cussents in the middle of the lagoon indicated very low current velocities (0.1-0.8 mls).

Mean tidal range = 0.31 rn -1.0

7/13/2000 8/2/2000 8/22/2000 911 1/2000 DATE

7/31/2001 8/20/2001 9/9/2001 9/29/2001 DATE

1 0 - 0 5 -

-0 5 -1 0

Figure 2. Mean daily maximum and minimum water levels during the ice-free periods in 2000 and 200 1 at Beaufort Lagoon, Arctic National Wildlife Refuge, northeastem Alaska.

/O 5 rn on 17 August lagoon ranged from 3.3 to 3.6 m. At Transect 2, which extended all the way across the lagoon, the barrier island had steep landward and seaward profiles and rose only 0.5 m above water level.

Arctic Coastal Dynamics - Report of an International Workshop 3 Extended Abstracts

PERMAFROST CHARACTERISTICS

Soil stratigraphy obtained from bank exposures at the three transects revealed a range of soil characteristics. Transects 1 and 3 were situated on abandoned floodplain deposits and Transect 2 was situated on a sand sheet possibly of glacial origin. All exposures had a thin (10-1 1 cm) fibrous peat accumulation at the surface underlain by a thin (17-23 cm) eolian silt deposit. Below these surface layers were thick accumulations of disrupted, amosphous peat clumps extending as deep as 1.5 m. Ice contents were higher in the sand sheet deposit with intermixed organic masses (72-79% vol.), than in the two abandoned floodplain deposits (45-79%). Ice wedges were wider (4 m across at the surface) and more dense in the older sand sheet deposit that in the abandoned floodplain (2 m).

Despite having the highest contents of both segregated and wedge ice, Transect 2 had the lowest erosion rate (see below). We attribute this lower erosion rate to the height of the bank and coarser soil materials. Because the bank at Transect 2 was about twice a high as the other transects, the volume of material that must be removed by erosion is nearly double. The coarser soil reduces erosion by providing small amounts of gravel that accumulates On the beach surface and reduces movement of fine-grained material.

COASTAL EROSION RATES

Photogrammetric analysis of aerial photography from 1948-1950 and 1978, and IKONOS imagery from 2001, revealed a mean erosion rate of 0.5 mlyr (SD k0.3, n=61) for the 1948-1978 period and 0.5 d y r (SD k0.4) for the 1978-2001 period along a 10 km stretch of coastline (Figure I). The comparison of erosion rates between periods indicates there has been no change in long-term erosion rates. Erosion, however, varied from 0 to 1.5 d y r over the entire coastline. Specific erosion rates for Transect 1-3 were 0.7, 0.5, and 1.0 mfyr, respectivel Y.

Erosion rates observed at Beaufort Lagoon are less than those observed along other stretches of the Beaufort Sea coast. At Elson Lagoon near Barrow, erosion rates over a 21-year period from 1979 to 2000 were 0.9, 0.7, 0.9, and 2.8 d y r for 4 short (2.0-3.4 km) coastal Segments (Brown et al. 2001). Over a broader area near Elson Lagoon, Lewellen (1970) measured mean erosion rates of 2.8 d y r (SD k2.5, n=13) with a maximum of 10.0 mlyr. Mean rates of coastal bluff retreat at Simpson Lagoon over a 25-year period (1955-1980) were 1.1 mlyr (SD k1.0, n=33) with a maximum of 5.4 m/yr (Naidu et al. 1984). For the coast between the MacKenzie Delta and Demarcation Bay, Mackay (1963) detemined a mean retreat rate of 2.5 mlyr. For a 344 km stretch of coast extending from Drew Point to Prudhoe Bay, the mean rate of coastal retreat was 2.5 d y r (excluding accretionary shoreline along Colville Delta) over a thirty year period with a maximum of 18 mlyr (Reimnitz et al. 1988). We attribute the lower rates at Beaufort Lagoon to: (1) shallow water in the lagoon which reduces wave height. (2) close proximity of barrier islands to the coastal bluffs which reduces fetch, and (3) to the prevalence of pack ice outside of the lagoon System (northeast Corner of Figure 1) which dampens wave energy during storm surges.

Arctic Coastal Dvnamics - Reoort of an International Workshoo 3 Extended Abstracts

-

TFWNSECT 1 Shoreline in 1948-50, based on 37 rn change m a s u r e d frorn photo analysis

I

-2

- -

-

Shoreline in 1948-50 based on 25 rnchange TRANSECT 2

TFWNSECT 3

-

W

2

0

5

LU

d -1 -2 -3 -4

DISTANCE (m)

Figure 3. Topographie profiles for permanent monitoring Transects 1-3 at Beaufort Lagoon. Arctic National Wildlife Refuge, northeastem Alaska.

REFERENCES

Brown, J. and S. Solomon (Eds.). 2001. Arctic Coastal Dynamics, Report of an International Workshop. Natural Resources Canada, Ottawa, Canada. Geol. Surv. Canada Open File 3929. 31 pp. (ACD, http://www.awi-potsdam.de/www-pot/geo/acd.html)

Arctic Coastal Dvnamics - R e ~ o r t of an International Workshoo 3 Extended AbsUacts

Brown, M. T., M. T . Jorgenson, and M. Macander. 2001. Fifty-year record of arctic coastal erosion, Bamow, Alaska. Eos. Trans. AGU 82:S231, Spring Meet. Suppl. (abstract).

Hopkins, D. M. and Hartz, R. W. 1978. Coastal morphology, coastal erosion, and barrier islands of the Beaufort Sea, Alaska: U. S. Geol. Surv., Open-File Report 78-1063. 54 pp.

Lewellcn, R.I. 1970. Permafrost erosion along the Beaufort Sea coast. Unpublished report produced by Lewellen Arctic Research, Palmer, Ak. 25 pp.

Mackay, J. R. 1963. Notes on the shoreline recession along the coast of the Yukon Territory.

Arctic (16):195-197.

Morkill, A.E. and D.L. Vandergraft. 2000. Dynamics of high latitude coasts: implications for managing the Arctic National Wildlife Refuge Alaska. Pages 293-296 in Proceedings of 2000 Annual Spring Specialty Conference on Water Resources in Extreme Environments.

American Water Resources Association, Middleburg, VA.

Reimnitz, E., S . M. Graves, and P. W. Barnes. 1988. Beaufort Sea coastal erosion, sediment flux, shoreline evolution, and the erosional shelf profile. U.S. Ge01 Surv., Map 1-1 182-G.

Naidu, S.A., T.C. Mowatt, S.E. Rawlinson, and H.V. Weiss. 1984. Sediment characteristics of the lagoons of the Beaufort Sea coast, and evolution of Simpson Lagoon. Pages 275-292 in The Alaskan Beaufost Sea: Ecosystems and Environments. Acadernic Press, Inc. New York.

Arctic Coastal Dvnamics - Reuort of an International Workshop 3 Extended Abstracts

A CIRCUM-ARCTIC COASTAL