Antarctic krill under sea ice Copyright © Marlo Garnsworthy
This week in ice begins with krill—or more specifically krill poop.
Krill are tiny shrimp-like creatures that live in schools called swarms, which can be thick (10,000 to 30,00 individuals per square meter) and vast (one swarm was 170 square miles to a depth of 660 feet). Found in oceans worldwide, krill are—in terms of biomass (the mass of living organisms)—one of the most significant species on our planet.
Krill feed in the upper reaches of the water column, eating phytoplankton (tiny plants) especially diatoms, and zooplankton (tiny animals such as copepods and amphipods). Zooplankton also feed on phytoplankton. Like other plants, phytoplankton take up carbon dioxide during photosynthesis. So, when krill eat phtyoplankton or zooplankton, they’re consuming this carbon.
A constant stream of organic matter such as fecal material and parts of dead organisms, as well as inorganic material such as dust, is constantly sinking through the water column. This material is called marine snow, and it can take weeks to reach the ocean floor, where it accumulates as a thick oozy mud (which we studied on our SNOWBIRDS Transect research cruise). When krill defecate, their fecal material sinks as marine snow through the water column, and any carbon in it is sequestered.
A study by scientists from the British Antarctic Survey found that the behavior of Antarctic krill could assist the sequestration of carbon dioxide. Scientists found that krill move up and down within their swarms. This behavior is called satiation sinking—and in simple terms, it means that once you’ve eaten your fill at the buffet, you move away from the buffet table, allowing others to feed. If you’re a krill, you sink to the lower reaches of the swarm, giving your carbon-rich poop a greater chance of making it to the sea floor.
British Antarctic Survey ecologist and lead author Professor Geraint Tarling says:
“This new finding could equate to krill sequestering 23 million tonnes of carbon to the deep sea each year, equivalent to annual UK residential greenhouse gas emissions.”
Something to keep in mind when regulating the fishing of krill. Krill are also a vital food source for fish, whales, penguins, and other marine species.
The big polar news this week was the release of NOAA’s Arctic Report Card.
“Arctic shows no sign of returning to reliably frozen region of recent past decades. Despite relatively cool summer temperatures, observations in 2017 continue to indicate that the Arctic environmental system has reached a ‘new normal’, characterized by long-term losses in the extent and thickness of the sea ice cover, the extent and duration of the winter snow cover and the mass of ice in the Greenland Ice Sheet and Arctic glaciers, and warming sea surface and permafrost temperatures.”
Highlights (Credit: NOAA Arctic Report; links embedded by me)
- The average surface air temperature for the year ending September 2017 is the 2nd warmest since 1900; however, cooler spring and summer temperatures contributed to a rebound in snow cover in the Eurasian Arctic, slower summer sea ice loss, and below-average melt extent for the Greenland ice sheet.
- The sea ice cover continues to be relatively young and thin with older, thicker ice comprising only 21% of the ice cover in 2017 compared to 45% in 1985.
- In August 2017, sea surface temperatures in the Barents and Chukchi seas were up to 4° C warmer than average, contributing to a delay in the autumn freeze-up in these regions.
- Pronounced increases in ocean primary productivity, at the base of the marine food web, were observed in the Barents and Eurasian Arctic seas from 2003 to 2017.
- Arctic tundra is experiencing increased greenness and record permafrost warming.
- Pervasive changes in the environment are influencing resource management protocols, including those established for fisheries and wildfires.
- The unprecedented rate and global reach of Arctic change disproportionally affect the people of northern communities, further pressing the need to prepare for and adapt to the new Arctic.
Most troubling is that melting of sea ice is unprecedented in at least 1,500 years.
Temperatures in the Arctic have been abnormally high, so high that computers disqualified temperature data, assuming it was an error.
Arctic sea ice extent and concentration remain well below the mean. Sea ice cover in the Beaufort and Chukchi Seas is at a record low extent. The National Snow and Ice Data Center says:
“November 2017 will be remembered not for total Arctic ice extent, which was the third lowest recorded over the period of satellite observations, but for the record low extent in the Chukchi Sea. This is a key area for Arctic Ocean access, and is an indicator of oceanographic influences on sea ice extent.”
Antarctic sea ice remains below the mean. After the third-lowest November average monthly extent in the satellite record, sea ice extent is near-average in all regions except the Weddell Sea, where it’s at a record low. Sea ice around the Weddell polynya (aka Maud Rise polynya, depicted by the shape toward the top) has melted, leaving open ocean.
Glaciers & Ice Shelves
Part of the East Antarctica ice sheet Credit: Michael Hambrey/Glaciers Online
The East Antarctic Ice Sheet may not be as stable as previously thought says this study. In the past, it has undergone dramatic retreats, and scientists now feel that, as the planet warms, it may provide a significant contribution to sea level rise.
Another study showed that even small losses of ice at the edges of ice sheets can accelerate the movement of glaciers grounded on rocks. Lead-author Ronja Reese (Potsdam Institute for Climate Impact Research) says:
“Destabilizing the floating ice in some areas sends a signal as far as 900 kilometers across the largest ice shelf in Antarctica… It does so with an amazing speed, similar to the speed with which shocks from an earthquake travel.”
On Thursday, the US Coast Guard International Ice Patrol said around 1,008 icebergs drifted into shipping lanes in the North Atlantic, up from 687 in 2016. This is the fourth consecutive “extreme” ice season. Retreat of the Greenland ice sheet/calving of icebergs, plus increased storminess that broke up sea ice, setting icebergs free to drift, is responsible, according to Ice Patrol Commander Kristen Serumgard.
We have a great new graphic showing the drift of massive iceberg A-68, which calved from the Larsen C ice shelf (Antarctica) back in July.
Credit: Dave Mosher
Scientists are on their way to study the effects on lifeforms that dwelled in darkness under the ice sheet now they’ve been exposed to the light by this dramatic calving event.
Starving Polar Bears, Giant Penguins, & the GOT Ice Wall
Back to that viral “starving polar bear” video that everyone may have gotten wrong. As I discussed last week, some experts, such as polar bear biologist Andrew Derocher and Arctic wildlife biologist Jeff Higdon, believe that bear may have not been starving and may in fact have been injured or diseased. Nunavut bear monitor Leo Ikakhik agrees the bear was likely sick or injured.
(In following Derocher and Higdon and this polar bear story, I’ve discovered that polar bear Twitter is not an entirely pleasant place for polar bear scientists—it’s somewhat of a hangout for a certain breed of climate change deniers, who frequently cite dubious sources.)
While that polar bear may have died due to other causes, the fact remains that polar bears—alongside other sea ice-dependent species—will face increasing challenges as sea ice continues to decline.
This study by Deorcher et al states:
“Anthropogenic global warming is occurring more rapidly in the Arctic than elsewhere, and has already caused significant negative effects on sea ice-dependent species such as polar bears. Although observed effects have thus far been gradual, the large amount of annual variation in the climate system may cause habitat changes in individual years that exceed the long-term trend. Such years may be below critical thresholds necessary for feeding and result in unprecedented reductions in survival, reproduction, and abundance in some populations.”
Why the media keeps getting Arctic news wrong.
Credit: Gerald Mayr—AP
On a New Zealand beach, scientists have found fossil evidence of a 5’8″ penguin that lived 60 million years ago.
And that ice wall in Game of Thrones? Impossible without magic, says glaciologist Martin Truffer (University of Alaska Fairbanks).
As always, I am not a scientist, just a writer/illustrator and science communicator passionately in love with sea ice. I welcome input and corrections by polar scientists as I learn more about this remarkable and vital part of our planet and bring this knowledge to a wider audience.