The Brightest Day of the Year
December 23, 2022
Summer Solstice, 2022
Cape Crozier, Ross Island, Antarctica
On the longest day of the year in the southern hemisphere, the Adélie penguins are about half-way through their breeding season. They’ve been here since late October, when they claim their nesting territories and choose mates. They lay their eggs by about November 15, and chicks hatch mid-December. By early February the chicks are independent, and the adults start preparing to molt. Today, most of the chicks are about the size of grapefruits, growing fatter by the moment as their parents stuff them full of krill and silverfish.
Our team has been here since early November, as we have been most years since 1996. I joined them on December 10th this year to help with attaching and retrieving newly redesigned biologgers (devices that have video cameras, accelerometers, dive recorders, GPS locators, and other sensors on board) to Adelie penguins. Other teammates launched three autonomous seagliders (8 foot long autonomous submarines with arrays of sensors on board) a few weeks ago and they are piloting them remotely, attempting to keep one within the penguin foraging area, and the other outside, to assess whether there are differences in the amount and kind of food available to them, and how that might be affected by changing ocean conditions. Our team has spent the past several years preparing for this field season, and it is exciting to finally see all the pieces come together.
Over the years, we have tried to find differences in the ocean habitat that predicted where they would find the most food, but that was largely unsuccessful. The main difference we found between successful penguin feeding locations and less-successful ones was the amount of light available underwater, which is largely a function of how much sea ice is covering the ocean, and how much algae is growing in it. Light availability changes from day to day and place to place, but solstice is the brightest day of the year! Good for penguin feeding, not so good for krill and silverfish who have a hard time hiding from all the predators without the cover of night. The video that the penguins are collecting show that some are finding lots of krill in clear water near the colony, to the northwest, but others are foraging farther away, to the northeast, in algae-filled water and working harder to find food. Analyzing all the data we are collecting this season will be the work of several graduate students and other scientists for years to come.
The ocean I see from our cozy little hut is bustling, with thousands of animals visible at any time – Adelie and emperor penguins, south-polar skuas, snow petrels, killer whales, minke whales, Weddell seals. We’ve also seen southern fulmars and Wilson’s storm-petrels. This far south, that’s a pretty good species list! I look forward to spending time with those attending our Antarctica trip on the other side of the continent a little more than a year from now. Happy holidays to you all!