Overview

Selected Sources Regarding the Great Salt Lake

Physiography and Variations in Lake Level

The Stansbury expedition of 1850

Chemistry of the Great Salt Lake

Biology of the Great Salt Lake

Thermodynamics of the Great Salt Lake

Current Monitoring Over the Great Salt Lake

Future Monitoring of the Great Salt Lake

Web Sources on the Great Salt Lake

Expanded version of this seminar with links and references: www.met.utah.edu/jhorel/ homepages/jhorel/seminar_lake.html

U.S. Geological Survey

Utah Geological Survey

State Department of Natural Resources

Westminster University

Physiography and Variations in Lake Level

Terminal basin of the Great Salt Lake includes the Provo, Weber, and Bear River drainages

16,000 years ago, Lake Bonneville's elevation was approximately 5100 feet ( 1550 m)

During past 10,000 years, lake has fluctuated between 4240 feet and 4180 feet

During historical record, lake has fluctuated between 4212 feet (1985) and 4192 feet (1964)

Present elevation of the Great Salt Lake is 4202 feet (1281 m)

The Stansbury Expedition of 1849-50

First detailed weather observations on the Great Salt Lake

Captain Howard Stansbury was instructed by the Army to conduct a mile-by-mile survey of the Great Salt Lake

Examples of weather observations on the Great Salt Lake:

• May 1. Sunrise 57F, cirrus. Noon 71F cirrus. 3 PM 69F cloudy. Sunset 63F calm

• April 16. About 4 oclock a violent gale came up accompanied by thunder and lightning from the west which instantly prostrated most of our tents and a copious fall of hail mingled with rain which wetted the party to the skin.

• May 8. Gunnison Island. We set out at 5 oclock on our return. When within 3 or 4 miles of camp a most furious gale of wind broke down upon us from the NW, which soon raised such a sea as to render the progress of our heavy boat so slow that we did not reach camp until 10 clock, cold tired & hungry.

Chemistry of the Great Salt Lake

Prior to the completion of the causeway in 1959, the Great Salt Lake was a relatively homogeneous saline lake

Gunnison Bay (north arm) is quite different from Gilbert Bay (south arm)

U.S.G.S. samples lake monthly

Small (1 foot) difference in height between two Arms now; surface flow through causeway is from north to south as a result of density differences

During summer, sodium chloride precipitates on floor and will remain on floor until salinity decreases significantly

Strong wind storms may cause hydrogen-sulfide rich bottom layers to be mixed to surface and contribute to "Lake Stink" as well as expose decomposing sulfur-rich mud flats

Biology of the Great Salt Lake

Surface layer

• Algae blooms during winter
• Brine shrimp hatch from hard-walled eggs (cysts) in April and graze phytoplankton
• Shrimp grow and reproduce during summer molting in as many as 12 different stages
• When shrimp stressed by lack of food or environmental conditions, they switch from producing live young to cysts
• Cysts harvested commercially during Fall and persist in a semi-dehydrated state until the salinity decreases in spring
• No live brine shrimp survive temperatures below 5C (42F)

Bottom layer

• During spring, shrimp consume enough phytoplankton for light to penetrate to depths
• Photosynthesis by algae in bottom layer provides source of food as well as detritus falling from surface water
• Two species of brine fly spend larval period on bottom of lake
• Flies emerge as adults in early summer
• 110 billion flies plus 10 billion pupae are estimated to hover over 300 miles of beaches (370 million flies per mile of beach)
• Flies consume algae and waste equivalent to a 78,000,000 gallon per day waste treatment plant

Thermodynamics of the Great Salt Lake

North Arm is warmer near the surface and cooler at depth than the South Arm

Annual cycle in temperature indicates:

• Surface temperature varies from 33.9 F in January to 79.3F in July

• Top 20 feet fairly well mixed during year

• Thermocline (warm water above cold depths) evident at 25-30 feet from April-August while higher temperatures at depth from October-February

• Warmer water at depth is possible, since salinity increases slightly with depth (density more sensitive to salinity than temperature)

Implications for the atmosphere of thermodynamic structure:

• Strong winds and upwelling bring colder water to surface from April-August

• Strong winds and upwelling bring warmer water to surface from October-February

• lake-effect snowstorms may be more persistent during Fall-early Winter than late Winter-Spring since strong winds in post-frontal environment do not cool off lake significantly

Current Monitoring over the Great Salt Lake

Utah Mesonet (www.met.utah.edu)

• Surface observations obtained from local, state, and federal agencies and private firms

• Cooperating agenices bear the cost of installing, maintaining, and upgrading equipment and communication costs for the most part

• Data retrieved, processed, and displayed every 15 minutes

• Goals:
  • provide access to weather information in a timely fashion for operational decision makers and the public
  • archive and utilize weather data for research and education related to understanding weather phenomena in the intermountain region

Applications of the Utah Mesonet: Utah ARPS Data Analysis System (ADAS)

• Local analysis at high temporal (1 h) and spatial resolution (1 km)

• Based on the Oklahoma ADAS (ARPS Data Analysis System) developed by the Center for Analysis and Prediction of Storms (CAPS)

• Incorporation of large-scale and local data

Physical Linkages Between the Great Salt Lake and the Atmosphere

• Moisture flux
• Sensible heat flux
• Stability
• Surface roughness

Examples of Current Monitoring and Analysis over the Great Salt Lake

• Mesonet stations near the Great Salt Lake
  • Many stations on the periphery including several each in Tooele, Salt Lake, and Weber Counties
  • Stations on Lake:
    • Antelope Island
    • Gunnison Island (Installed 5/22/98)
    • Hat Island (Installed 9/2/98)

• ADAS surface analyses of the diurnal cycle

Future Monitoring of the Great Salt Lake

Weather support for 2002 Winter Olympics requires high-resolution numerical guidance

Lake remains large data void in northwestern Utah

Considerable need to have reliable measure of lake temperature in open water for initialization of forecast models

Lake temperature sensor placed off Hat Island was expected to be temporary and communication to sensor is beginning to fail

Collaborative project underway with Woods Hole Oceanographic Institution and State Department of Wildlife Resources to place buoy on the lake

Parameters to be measured and available every hour:

• Surface air temperature
• Solar radiation at surface
• Surface lake temperature
• Lake temperature at 3, 5 and 7 m depth
• Photosynthetically Active Radiation (PAR)
• Chlorophyll
• Turbidity
• Salinity (to be added later)