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The Polar Retrospective – Blue aurora, seals on icebergs and an enigmatic lake

Ole Ellekrog 16. December 2024 | Arctic, Science
Seals resting on an iceberg in Johns Hopkins Inlet, Glacier Bay National Park. Photo: Jamie Womble, National Park Service

The Polar Retrospective looks at recent stories from around the world’s polar regions. This week we hone in on two polar enigmas, and a phenomenon that’s now better understood. The topics are miscolored aurora, an (almost) frozen Antarctic lake, and seals cruising on icebergs.

The Polar Retrospective is a collaborative effort by the Polar Journal team. Each writer chooses a topic they found interesting and important in the past week. The intitials at the end of each section indicate the author. We hope you enjoy it.

An Enigma full of life

Lake Enigma is one of many subglacial lakes on the Antarctic continent. Protected from the outside world by the ice cap for millions of years, these lakes are home to micro-organisms, most of which have yet to be discovered. Photo: Smedile et al.

Lake Enigma, located in Victoria Land, in the south-east of the continent, was the subject of a study carried out by the Italian Institute of Polar Sciences between 2019 and 2020, the results of which were published on December 3rd in Communications Earth & Environment. For a long time it was thought that this lake, located between the Amorphous and Boulder Clay glaciers, was nothing more than a completely frozen body of water in a region where the average temperature is -14°C. But this is not the case.

Equipped with ground-penetrating radar, scientists discovered liquid water eleven meters below the surface of a lake at least twelve meters deep. The boreholes took samples from the surface ice, the different layers of the water column and the microbial mat at the bottom.

Analyses then showed that Lake Enigma is home to an extremely diverse and abundant microbial ecosystem. Bacteria of the phyla Pseudomonadota, Actinobacteriota and Bacteroidota were identified, as well as an abundance of superphylum Patescibacteria. The latter are extremely simple bacteria, consisting of small cells and a small genome, capable of carrying out only a limited number of processes. This microbial community is unique in Antarctic subglacial lakes. 

What’s more, the species identified are probably descendants of those that managed to survive when the lake finally froze over during the continent’s glaciation. In the desert conditions that prevail in the area, the lake would have dried up. According to the researchers, this could be a sign that an as yet unidentified water source feeds the lake, which certainly lives up to its name. M.B.

Link to the study: Smedile, F., La Cono, V., Urbini, S. et al. The perennially ice-covered Lake Enigma, Antarctica supports unique microbial communities. Commun Earth Environ 5, 741 (2024). https://doi.org/10.1038/s43247-024-01842-5

How harbor seals choose the perfect iceberg

A harbor seal nursery on glacial ice in front of Grand Pacific Glacier in Glacier Bay National Park, Alaska. Photo: Richard N. Horne via Wikimedia, CC BY-SA 4.0

About 2,000 harbor seals inhabit the Alaskan fjords of Johns Hopkins Inlet in Glacier Bay National Park. Their clever survival strategy: using icebergs as floating platforms. A recent study by the University of Alaska Southeast and the National Park Service reveals that these marine mammals specifically choose large, stable icebergs as habitats for giving birth, nursing their young, and molting.  

The Johns Hopkins Glacier is one of the few glaciers in the world that is still advancing. Its terminal moraine shields it from warm ocean currents, slowing its melting. However, this natural barrier comes with a downside: fewer icebergs are calving, reducing the amount of habitat available for the seals.  

To better understand the impact on the seals, researchers observed iceberg movements and seal distribution in the fjord using time-lapse and aerial photography over a 15-year period.  

The findings show that seals with pups prefer slow-moving icebergs, which provide more stability and safety. During the molting season, however, the seals are more likely to rest on faster-drifting icebergs closer to prime feeding grounds. J.H.

Link to the study: Kaluzienski LM, Amundson JM, Womble JM, Bliss AK, Pearson LE. Impacts of tidewater glacier advance on iceberg habitat. Annals of Glaciology. 2023;64(90):44-54. doi:10.1017/aog.2023.46

Blue aurora measured by Japanese scientists

This photo by Dominik Plüss of the St. Chrischona Chuch in Bettingen outside Basel was part of a compilation of Swiss northern light photos last week. Photo: Dominik Plüss
Back in May, huge solar eruptions made the northern lights visible in unusually south regions, like here in Basel, Switzerland. But the eruptions also caused another strange phenomenon: blue aurora. Photo: Dominik Plüss

In May of this year, the aurora borealis were observed as far south as Switzerland and northern Italy. Suddenly, millions of people outside the world’s Polar regions could photograph these elusive lights in the sky. 

The unusual phenomenon was caused by a series of strong solar storms, but also, perhaps, because of advances in smartphone photography, as described by Polar Journal. Now at least, two Japanese scientists have made a new discovery in photos taken during the storms back in May: blue aurora.

Using smartphone photos from two amateur astronomers, Sota Nanjo from the University of Electrocommunication in Tokyo and Kazuo Shiokawa from Nagoya University in Aichi, observed the presence of the blue lights. They were found around the Earth’s magnetic fields and at heights of 400 to 900 kilometers. 

The existence of these blue lights remains unexplained. The measurements did not correspond with existing theories for blue aurora but Nanjo and Shiokawa did not propose a new theory either. The Japanese team now hopes future strong auroras and more observations will help unravel this mystery. O.E.

Read more here.

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