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Earth Matters

August Puzzler Answer: Bloom in the Baltic Sea

August 26th, 2015 by Kathryn Hansen


When I first saw the image for the August puzzler, I was struck by its beauty. The blue-green swirls look like they could be the brush strokes of an impressionist painting. Instead, this false-color scene was acquired by the Operational Land Imager (OLI) on Landsat 8.

Without any land visible in the scene, I thought it would be at least a day or two before receiving a correct guess. I was wrong. Congratulations to Helen Macintyre who was the first to correctly post a correct answer to the blog on August 18, just 94 minutes after the puzzler was posted.

Macintyre wrote, “Initially I thought hurricane, but the strands in the upper left seem too sharp and thin. I think this is an algal bloom swirling in ocean currents. The line near the top I think is a large ocean liner cutting through this, leaving a darker colored wake.”

Indeed, the scene shows a phytoplankton bloom. This particular bloom contains cyanobacteria—an ancient type of marine bacteria that, like other phytoplankton, capture and store solar energy through photosynthesis.

Later that same day, Kari Nöjd posted a comment and became the first to correctly guess the phenomenon and its location. In fact, Nöjd was the only participant to correctly place this bloom in the Baltic Sea. Excellent work!

Nöjd wrote, “My guess is that this picture shows sea surface where algae is blooming. The line is from the boat, which is driving through the sea surface. Picture could have been taken from the Baltic Sea where has been big algae blooming fields forming for the past month … Unfortunately this is also effect of a human behavior. Nutrients from fields and waste waters increase the algae blooming.”

According to NASA oceanographer Norman Kuring, major cyanobacteria blooms like this one appear in the Baltic Sea nearly every summer, “and they always look like this in the satellite data.” Physical measurements from an expert in the field, however, were required to confirm that the bloom was cyanobacteria.

As for the line cutting through the scene? Yes, that’s the result of a ship cruising through the bloom. There are other ships too, as well as an airplane, visible in the zoomed-out version posted in our August 23, 2015, Image of the Day.

On Facebook, Scot Hoffman was the first to guess algae bloom. In fact, a lot of comments on Facebook noted that the scene was a bloom, but the location remained elusive. Many thought it might be Lake Erie—a good guess because blooms are visible during the summer in that lake as well.

August Puzzler

August 18th, 2015 by Kathryn Hansen


Every month on Earth Matters, we offer a puzzling satellite image. The August 2015 puzzler is above. Your challenge is to use the comments section to tell us what part of the world we are looking at, when the image was acquired, what the image shows, and why the scene is interesting.

How to answer. Your answer can be a few words or several paragraphs. (Try to keep it shorter than 200 words). You might simply tell us what part of the world an image shows. Or you can dig deeper and explain what satellite and instrument produced the image, what spectral bands were used to create it, or what is compelling about some obscure speck in the far corner of an image. If you think something is interesting or noteworthy, tell us about it.

The prize. We can’t offer prize money, but, we can promise you credit and glory (well, maybe just credit). Roughly one week after a puzzler image appears on this blog, we will post an annotated and captioned version as our Image of the Day. In the credits, we’ll acknowledge the person who was first to correctly ID the image. We’ll also recognize people who offer the most interesting tidbits of information about the geological, meteorological, or human processes that have played a role in molding the landscape. Please include your preferred name or alias with your comment. If you work for or attend an institution that you want us to recognize, please mention that as well.

Recent winners. If you’ve won the puzzler in the last few months or work in geospatial imaging, please sit on your hands for at least a day to give others a chance to play.

Releasing Comments. Savvy readers have solved some of our puzzlers after only a few minutes or hours. To give more people a chance to play, we may wait between 24-48 hours before posting the answers we receive in the comment thread.

Good luck!