Sea ice quality is of paramount importance for ice security and under-ice lake ecology, but its temporal and spatial variability is largely unknown. From 2021–2022, an international research team including IGB researcher Hans-Peter Grossart conducted a coordinated sampling campaign on sea ice quality across the entire northern hemisphere during one of the warmest winters since 1880.
The team, led by Sweden’s Uppsala University, was able to show that sea ice during this period generally consisted of unstable white ice, at times accounting for up to 100% of the total ice thickness.
Sea ice can have different qualities, and you can already tell the difference by the color: there is white ice and there is smooth ice. Compared to black ice, white ice is more unstable and has a lower carrying capacity, making it risky to use for transportation, recreation, or other purposes. It is also known that white ice significantly reduces the amount of sunlight entering the ice. This threatens the growth and reproduction of all organisms that engage in photosynthesis, and thus the entire food web can be disrupted or disrupted.
White ice is likely to become more common in the future
“During the IceBlitz sampling campaign, we collected 167 ice cores in ten different countries. In January, most lakes had a thin layer of white ice, which then gradually grew across the entire ice sheet. Before the ice melted, white ice was the dominant type of ice on most of the lakes we sampled,” explains IGB researcher Hans-Peter Grossart, who was involved in the study.
White sea ice is usually formed when snow accumulates on ice, melts, and then refreezes. Or when rain falls on the layer of snow, forming slush that can then freeze and turn into white ice. Likewise when the snow load is sufficient to push sea through cracks in the ice matrix to the ice surface. All of this occurs especially when air temperatures hover around freezing.
Ice stability decreases
“As global warming progresses, the prevalence of white ice is likely to increase significantly during the critical period prior to melting. In school, we learn that it’s okay to walk on ice if the ice thickness is four inches or more. We estimated that 10 centimeters.” ice allows a load of 1,753 kilograms in black ice conditions, while in white ice conditions they can only support a load of up to 175 kilograms, so the differences in ice stability are very large and relatively small increasing the percentage of white ice may threaten the use of seasonally ice-covered lakes for subsistence, recreation, transport and other purposes,” warned Professor Gesa Weyhenmeyer, lead author of the study from Uppsala University.
Light transmission through white ice and ecological effects
White ice is many times more reflective than black ice, so only small amounts of light penetrate white ice. Low light conditions in spring, caused by a white ice sheet and snow on the ice, are crucial for the development of primary producers and consumers, since their growth and reproduction depend on light. Although organisms have evolved a variety of survival strategies, changes in the photoautotrophic community induced by snow and white ice have a cascading effect on the food web, with significant consequences for microbial, zooplankton, and fish populations.
“The ice safety guidelines need to be renewed, and the thickness of the white ice also needs to be considered as an important regulator of physical, chemical and biological processes in lakes,” concluded Weyhenmeyer.
The research was published in nature communication.
Gesa A. Weyhenmeyer et al., On Critical White Ice Conditions in Lakes Under Global Warming, nature communication(2022). DOI: 10.1038/s41467-022-32633-1
Provided by Forschungsverbund Berlin eV (FVB)
Citation: Study Highlights Dangers of White Ice Conditions in Lakes (2022, November 23) Retrieved November 23, 2022 from https://phys.org/news/2022-11-highlights-dangers-white-ice-conditions.html
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