The Great Salt Lake in Utah and the world’s oceans hold dramatically different concentrations of dissolved minerals. Curiosity often centers on comparing the two, asking whether the inland lake is saltier than the global ocean. While oceans maintain a consistent composition, the Great Salt Lake is a dynamic system whose salinity fluctuates widely depending on water levels and internal geography. Understanding this comparison requires looking closely at specific measurements and the unique geological circumstances that define the lake.
Comparing Salinity Levels
The Great Salt Lake is generally saltier than the ocean, often by a substantial margin. The world’s oceans maintain a stable average salinity of approximately 3.5%, or 35 parts per thousand (ppt) of dissolved salt by weight. This consistency is maintained by the vast volume of water and constant mixing of the global circulation system.
In contrast, the Great Salt Lake’s overall salinity is highly variable, influenced by the lake’s changing water level. Historically, its salinity has ranged from a low of about 5% to a high of nearly 27%. Even at its least concentrated, the lake is significantly saltier than the ocean, and at its maximum, it can be nearly eight times as salty.
The Geological Factors Creating Hypersalinity
The extreme concentration of salt in the Great Salt Lake is attributable to its unique hydrological status as an endorheic basin. This describes a closed drainage system where water flows inward but has no natural outlet. The three major tributaries—the Bear, Weber, and Jordan Rivers—continuously flow into the lake, carrying dissolved minerals and salts leached from the surrounding soil and rock.
The only way water can leave the lake is through evaporation, which removes pure water but leaves all dissolved solids behind. This continuous inflow of mineral-laden water combined with constant removal of freshwater acts as a concentrating mechanism over geological time. The lake is a remnant of the much larger, prehistoric Lake Bonneville, which concentrated its salt load as it receded, contributing to the salt mass present today.
Salt Composition and Internal Variability
The Great Salt Lake does not possess a uniform salinity, which differs significantly from the open ocean. A railroad causeway, constructed in the late 1950s, bisects the lake and restricts water circulation between the northern and southern arms. The South Arm (Gilbert Bay) receives almost all the fresh water from the tributary rivers, keeping its salinity lower and more variable, typically ranging from 12% to 16%.
The North Arm (Gunnison Bay) receives minimal freshwater inflow and has become significantly saltier as water evaporates, often reaching near the saturation point of 26% to 28%. This separation creates two distinct water bodies with dramatically different salt concentrations. While ocean salt is overwhelmingly sodium chloride, the Great Salt Lake’s composition is slightly different. Its dissolved solids are primarily sodium chloride, but they are enriched in elements like potassium and sulfate, and depleted in calcium, reflecting the specific geology of the surrounding basin.