//
you're reading...

Biogeochemistry

Key Role of Sea Ice in Glacial Cycles

Source: Marzocchi, A., and M. F. Jansen (2019), Global cooling linked to increased glacial carbon storage via changes in Antarctic sea ice. Nature Geoscience. doi:10.1038/s41561-019-0466-8

Water is transported around the world’s oceans via a current system called the meridional overturning circulation (MOC), often referred to as the great ocean conveyer belt. Figure 1 below shows the approximate path of this conveyer belt–red indicates transport near the surface and blue represents deep transport. Along with water, these currents carry and redistribute heat, salt, and gasses. Therefore, the overturning circulation plays an important role in regulating the global climate system.

Figure 1: Schematic of the global overturning circulation (Robert Simmon via Wikimedia Commons)

Over the past 2.5 million years, Earth’s climate has varied between cold glacial and warm interglacial periods. This variability is linked to slight changes in Earth’s orbit, which determine the amount of warming from the sun. Rise and fall of atmospheric carbon dioxide (CO2) levels is also important in driving these glacial-interglacial cycles. Given the role of the ocean in regulating atmospheric CO2 concentrations, it follows that changes in the large-scale ocean circulation over time can also play a role in the glacial cycles. However, the relative importance of the ocean circulation in affecting these trends is not well understood.

Studying changes in the ocean circulation between glacial and interglacial periods is difficult since there is no observational data from thousands of years ago. Therefore, scientists have to infer past circulation using other methods such as analysis of sediment cores from the seafloor and ice cores from glaciers. These reconstructions are based on the properties of the atoms within the sediment or ice. For example, isotopes are different forms of the same element with varying numbers of neutrons. By measuring the ratio of different isotopes for a particular element in a sediment or ice sample, scientists can infer past temperature or carbon dioxide levels. This type of analysis suggests that the ocean circulation has experienced major glacial-interglacial modifications over the past 2.5 million years.

Figure 2: Aerial image of Antarctic sea ice (NASA/Nathan Kurtz via Wikimedia Commons)

In addition to reconstructions of oceanographic conditions from isotope ratios, scientists can also use numerical models to try to understand glacial cycles. A recent study in Nature Geoscience led by Alice Marzocchi at the National Oceanography Centre in the UK uses an idealized model of the Atlantic Ocean to investigate the role of Antarctic sea ice in forcing glacial cycles.

In the model simulations, Marzocchi lowered the atmospheric temperature to imitate the transition into a glacial period. As a result of this, Antarctic sea ice expanded and the deep ocean became more stratified. These changes are consistent with reconstructions of the circulation at the Last Glacial Maximum (LGM), about 21,000 years ago. Furthermore, the reorganization of waters in the deep ocean led to enhanced oceanic carbon uptake, which could account for up to half the glacial-interglacial variation in atmospheric CO2.

These results suggest that changes in Antarctic sea ice and circulation, triggered by atmospheric cooling, stimulate carbon drawdown and thus play a large role in glacial-interglacial transitions. By describing the mechanisms driving changes in oceanic carbon storage over long timescales, studies such as this are key to understanding glacial cycles.

Discussion

No comments yet.

Post a Comment

Instagram

  • by oceanbites 22 hours 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 1 week 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 weeks 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 3 weeks 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 1 month 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 2 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 2 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 2 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 2 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 3 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 3 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 4 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 4 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 5 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 5 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 6 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 6 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 7 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 7 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
  • by oceanbites 8 months ago
    Today is the day of  #shutdownacademia  and  #shutdownstem  and many of us at the Oceanbites team are taking the day to plan solid actions for how we can make our organization and the institutions we work at a better place
WP2Social Auto Publish Powered By : XYZScripts.com