//
you're reading...

Physical oceanography

What caused a massive hole in Antarctic sea ice?

Source: Campbell, E. C., E. A. Wilson, G. W. Kent Moore, S. C. Riser, C. E. Brayton, M. R. Mazloff and L. D. Talley (2019), Antarctic offshore polynyas linked to Southern Hemisphere climate anomalies. Nature, doi:10.1038/s41586-019-1294-0

Sea ice plays an important role in the climate system by modulating interactions between the ocean and atmosphere. For example, sea ice shields the surface ocean from winds and reflects a lot of sunlight due to its white color. Through mechanisms such as this, sea ice affects the ocean’s uptake of heat and nutrients. Therefore, accurately predicting sea ice extent and thickness is crucial to understanding and modeling global climate.

In some regions of the Antarctic, massive holes in the sea ice, called polynyas, can form. In 2016 and 2017 a large polynya formed in the Weddell Sea over a plateau on the seafloor called Maud Rise – the largest since the 1970s. What caused the polynya to form and why was it so large in these years? A group of scientists led by Ethan Campbell at the University of Washington investigated these questions.

The study uses data collected by robotic floats that drift around the Southern Ocean, as well as measurements collected by seals! Elephant seals outfitted with data-collecting instruments, like the one in the picture below, are an important source of data in ice-covered regions that are difficult to reach by ship.

An elephant seal with an instrument strapped to its head that measures the temperature and salinity of the ocean (Lars Boehme via SEANOE).

The measurements showed that the waters over Maud Rise were particularly salty during the years in which the polynya formed. This is important since the density of seawater depends on its salinity and temperature – namely, saltier and colder water is more dense. The researchers suggest that high salinity, combined with strong storms, is responsible for opening the hole in the ice in 2016 and 2017. The storms mix the salty water up to the surface, where it gets cooled and sinks, being replaced by warmer water from below. This sets up a feedback loop that prevents ice from re-forming.

Although the polynya formation is a local process, it could have large impacts on the climate system. For example, the waters being brought up to the surface in the polynya are enriched in carbon since they haven’t been in contact with the atmosphere for hundreds of years or more. This sequestered carbon can be released back into the atmosphere when the water gets drawn up by the polynya.

Satellite image of the Weddell polynya (NASA Earth Observatory).

Can we expect more frequent polynyas in the future or were the 2016 and 2017 events unique? According to the researchers, the answer is not clear. On the one hand, the trend of shifting wind patterns over the Southern Ocean may increase the mixing that is necessary for polynya formation. However, increased freshwater input from Antarctic ice sheet melt could make the ocean more stratified and prevent mixing, subsequently preventing polynya formation. Trying to tease out these competing mechanisms is important going forward.

Sea ice extent and concentration is driven by a complex combination of circulation and mixing, as well as interaction with the atmosphere. Holes in the sea ice, called polynyas, are particularly important since they are a direct conduit between the surface and deep ocean. Therefore, accurately describing the dynamics of these systems, through studies like this one, is critical to improving future climate predictions.

Discussion

No comments yet.

Post a Comment

Instagram

  • by oceanbites 4 days ago
    Being on a research cruise is a unique experience with the open water, 12-hour working shifts, and close quarters, but there are some familiar practices too. Here Diana is filtering seawater to gather chlorophyll for analysis, the same process on
  • by oceanbites 1 month ago
    This week for  #WriterWednesday  on  #oceanbites  we are featuring Hannah Collins  @hannahh_irene  Hannah works with marine suspension feeding bivalves and microplastics, investigating whether ingesting microplastics causes changes to the gut microbial community or gut tissues. She hopes to keep working
  • by oceanbites 2 months ago
    Leveling up - did you know that crabs have a larval phase? These are both porcelain crabs, but the one on the right is the earlier stage. It’s massive spine makes it both difficult to eat and quite conspicuous in
  • by oceanbites 2 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring Cierra Braga. Cierra works ultraviolet c (UVC) to discover how this light can be used to combat biofouling, or the growth of living things, on the hulls of ships. Here, you
  • by oceanbites 2 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Elena Gadoutsis  @haysailor  These photos feature her “favorite marine research so far: From surveying tropical coral reefs, photographing dolphins and whales, and growing my own algae to expose it to different
  • by oceanbites 3 months ago
    This week for  #WriterWednesday  on Oceanbites we are featuring Eliza Oldach. According to Ellie, “I study coastal communities, and try to understand the policies and decisions and interactions and adaptations that communities use to navigate an ever-changing world. Most of
  • by oceanbites 3 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Jiwoon Park with a little photographic help from Ryan Tabata at the University of Hawaii. When asked about her research, Jiwoon wrote “Just like we need vitamins and minerals to stay
  • by oceanbites 3 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring  @riley_henning  According to Riley, ”I am interested in studying small things that make a big impact in the ocean. Right now for my master's research at the University of San Diego,
  • by oceanbites 3 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Gabby Stedman. Gabby is interested in interested in understanding how many species of small-bodied animals there are in the deep-sea and where they live so we can better protect them from
  • by oceanbites 4 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Shawn Wang! Shawn is “an oceanographer that studies ocean conditions of the past. I use everything from microfossils to complex computer models to understand how climate has changed in the past
  • by oceanbites 4 months ago
    Today we are highlighting some of our awesome new authors for  #WriterWednesday  Today we have Daniel Speer! He says, “I am driven to investigate the interface of biology, chemistry, and physics, asking questions about how organisms or biological systems respond
  • by oceanbites 5 months ago
    Here at Oceanbites we love long-term datasets. So much happens in the ocean that sometimes it can be hard to tell if a trend is a part of a natural cycle or actually an anomaly, but as we gather more
  • by oceanbites 5 months ago
    Have you ever seen a lobster molt? Because lobsters have exoskeletons, every time they grow they have to climb out of their old shell, leaving them soft and vulnerable for a few days until their new shell hardens. Young, small
  • by oceanbites 6 months ago
    A lot of zooplankton are translucent, making it much easier to hide from predators. This juvenile mantis shrimp was almost impossible to spot floating in the water, but under a dissecting scope it’s features really come into view. See the
  • by oceanbites 6 months ago
    This is a clump of Dead Man’s Fingers, scientific name Codium fragile. It’s native to the Pacific Ocean and is invasive where I found it on the east coast of the US. It’s a bit velvety, and the coolest thing
  • by oceanbites 7 months ago
    You’ve probably heard of jellyfish, but have you heard of salps? These gelatinous sea creatures band together to form long chains, but they can also fall apart and will wash up onshore like tiny gemstones that squish. Have you seen
  • by oceanbites 7 months ago
    Check out what’s happening on a cool summer research cruise! On the  #neslter  summer transect cruise, we deployed a tow sled called the In Situ Icthyoplankton Imaging System. This can take pictures of gelatinous zooplankton (like jellyfish) that would be
  • by oceanbites 8 months ago
    Did you know horseshoe crabs have more than just two eyes? In these juveniles you can see another set in the middle of the shell. Check out our website to learn about some awesome horseshoe crab research.  #oceanbites   #plankton   #horseshoecrabs 
  • by oceanbites 8 months ago
    Feeling a bit flattened by the week? So are these summer flounder larvae. Fun fact: flounder larvae start out with their eyes set like normal fish, but as they grow one of their eyes migrates to meet the other and
  • by oceanbites 8 months ago
    Have you seen a remote working setup like this? This is a photo from one of our Oceanbites team members Anne Hartwell. “A view from inside the control can of an underwater robot we used to explore the deep parts
WP2Social Auto Publish Powered By : XYZScripts.com