Tel Aviv University (TAU) researchers participated in a new international study finding that, as a result of global warming, lightning storms have been directly hastening the ongoing process of sea ice retreat covering the Arctic Ocean.

Until recently, lightning as a phenomenon was extremely rare in the Arctic region of the North Pole due to the intense cold, the researchers say. But due to the warming of the Earth, lightning storms have become more common there in the summers. These storms further increase the process of the melting of the ice sheets in a “feedback loop.”

Professor Colin Price and MSc student Tair Plotnik from the Department of Geophysics at TAU’s Porter School of the Environment and Earth Sciences participated in the study alongside Dr. Anirban Guha and Dr. Joydeb Saha from Tripura University in India. The article was published in the October 2023 issue of Atmospheric Research.

“The Arctic region is defined as the region located north of the 66.5° latitude,” Professor Price explains. “In the heart of this region, around the North Pole, there is no land, and due to the extreme cold conditions, the sea is covered with a thick layer of sea ice, which currently extends over about 8 million square kilometers. The white ice reflects the sun’s rays, and thus contributes to the cooling of the Earth.

“But in recent decades, with the warming of the Earth, the ice cover has retreated at a rate of about 70,000 square kilometers per year, or 6.5% per decade. In this context it is important to note that the temperature at the North Pole has been rising at an accelerating pace — about 4° until today, in contrast to about 1° on Earth as a whole. The retreat of the ice increases the warming even further, because the dark areas of the ocean under the ice, which are getting bigger and bigger, absorb the sun’s rays that would normally be reflected back to space. This is how a feedback loop is created: the retreat of the ice increases the warming, which in turn increases the melting of the ice, and the cycle repeats.”

The researchers explain that lightning, as a phenomenon, was extremely rare in the Arctic region until recently, due to the intense cold that prevails there. But in recent decades, apparently due to global warming, lightning storms have been observed there in the summer season, when the sun does not set at all, heating the Earth’s surface. Lightning storms are formed when the surface of the ground heats up, and pockets of air rise up in the atmosphere, where they cool, condense, and become clouds that sometimes develop into thunderstorms.

A statistical analysis of the ice sheet retreat compared with the number of lightning storms revealed a correlation: as the number of storms increased in a certain year, so did the melting of the sea ice increase that year. The researchers explain this by comparing thunderstorms to a giant vacuum cleaner, sucking water vapor up from the surface layer to the upper atmosphere (5-10km altitude), where it accumulates and acts like an additional blanket, trapping the surface heat from leaving, and increasing the surface temperature. Another possibility is that these same lightning storms lead to an increase in the formation of high cirrus clouds in the upper layers of the atmosphere, which also form a similar “blanket.”

“In our research, we found a clear statistical relationship between the number of lightning storms in the Arctic region in a certain year and the rate of sea ice melting in that year,” Professor Price concludes. “This means that the storms are another factor that increases the melting of the polar ice, producing a feedback loop: the initial melting of the ice increases the dark surface areas of the sea which absorb more of the sun’s rays, warming up the waters, causing more melting, accelerating the rate of warming, which in turn increases the amount of lightning storms, and the cycle repeats itself.

“As a result of this, and of the warming of the Earth in general, we expect that the frequency of lightning storms in the Arctic region will increase in the coming years, and with it the rate of sea ice retreat in the Arctic Sea will accelerate.”