Researchers walk along the bank of the Dead Sea, one of Earth’s saltiest
bodies of water. It is nearly ten times saltier than the ocean.
Credit: Nadav Lensky/Geological Survey of Israel.

New research explains why salt crystals are piling up on the deepest parts of the Dead Sea’s floor, a finding that could help scientists understand how large salt deposits formed in Earth’s geologic past.

The Dead Sea, a salt lake bordered by Jordan, Israel and the West Bank, is nearly 10 times as salty as the ocean. Humans have visited the Dead Sea for thousands of years to experience its purported healing properties and to float in its extremely dense, buoyant waters, and mention of the sea goes back to biblical times.

Much of the freshwater feeding the Dead Sea has been diverted in recent decades, lowering the sea’s water levels and making it saltier than before. Scientists first noticed in 1979, after this process had started, that salt crystals were precipitating out of the top layer of water, “snowing” down and piling up on the lakebed. The salt layer on the lake floor has been growing about 10 centimeters (4 inches) thicker every year.

The process driving this salt crystal “snow” and buildup of salt layers on the lakebed has puzzled scientists because it doesn’t make sense according to the laws of physics. Now, a new study in AGU’s journal Water Resources Research proposes that tiny disturbances in the lake, caused by waves or other motion, create “salt fingers” that slowly funnel salt down to the lakebed.

“The initial fingers might only be a few millimeters or a couple of centimeters thick, but they’re everywhere across the entire surface of the lake,” said Eckart Meiburg, also a mechanical engineer at UC Santa Barbara and co-author of the new study. “Together these small fingers generate a tremendous amount of salt flux.”

Researchers at AGU created a computer simulation of how water and salt would flow in the Dead Sea if the salt fingers theory was correct. They found the salt fingers theory correctly predicted the downward flow of salt snow and buildup of salt layers in the middle of the lake’s floor. Because the level of the lake is declining, due to pumping of freshwater from the nearby Jordan River, the salt layers are concentrated in the central part of the lake, according to the authors.

The Dead Sea is only hypersaline water body on Earth today where this salt fingering process is happening, so it represents a unique laboratory for researchers to study the mechanisms by which these thick salt deposits have formed, according to the authors. It also not only helps researchers better understand the physics of the Dead Sea but also helps explain the formation of massive salt deposits found within Earth’s crust.  See the study in full at the Association for the Sciences of Limnology and Oceanography’s official website.