//
you're reading...

Physical oceanography

Reevaluating the Ocean Conveyer Belt

Source: Newsom, E. R., and A. F. Thompson (2018), Reassessing the role of the Indo-Pacific in the ocean’s global overturning circulation. Geophysical Research Letters, doi:10.1029/2018GL080350.

Water is transported around the world’s oceans via a current system called the global overturning circulation (GOC), 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.

The GOC pathways shown in Figure 1 are controlled, in part, by changes in the density of the surface ocean–called surface buoyancy fluxes. The density of seawater depends on its temperature and salinity (the amount of salt in it). Therefore, surface buoyancy fluxes are related to changes in the heating or cooling of the surface ocean, as well as changes in the salt content due to precipitation, evaporation, and ice processes.

For example, consider the sinking of waters in the North Atlantic signified by the red-to-blue arrows off Greenland in the diagram. This deep water formation is due to the rapid cooling of surface waters as they flow into the Arctic (making it denser). Water also sinks in the Antarctic because of sea ice formation. As water freezes, salt is removed and ends up in the surface water (making it denser). In other words, sinking of waters in the polar regions due to surface buoyancy fluxes is known to have a significant influence on the GOC. It is generally assumed however, that surface processes in the Indian and Pacific Oceans (collectively called the Indo-Pacific) are not as important as in the polar regions.

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

In a recent study published in Geophysical Research Letters, scientists at Caltech challenged this assumption that surface buoyancy fluxes in the Indo-Pacific are less important to the GOC than surface processes in the polar regions. This conclusion is reached through examination of buoyancy transport in a coupled climate model. The scientists developed a new technique that uses the patterns of surface buoyancy flux to infer the circulation in the ocean interior.

The map in Figure 2 shows the surface buoyancy flux in the global ocean. Note that the equatorial Pacific is the most orange, meaning that it has the highest positive buoyancy flux (surface ocean becomes lighter). The north Atlantic on the other hand is blue, meaning that it has negative buoyancy flux (surface ocean becomes denser). The GOC must act to counter this imbalance, transporting buoyancy from where it is gained at the surface (equatorial Indo-Pacific) to where it is lost (North Atlantic). This reinforces the importance of the GOC in linking the different ocean basins. The scientists also argue that this means the structure of the GOC depends equally on surface processes in the equatorial Indo-Pacific and in the polar regions.

Figure 2. Map of surface buoyancy flux in the global ocean (Talley, 2013).

It may seem like a small and unimportant detail that the global overturning circulation is driven by surface processes in the low-latitudes of the Indo-Pacific and the polar regions (as opposed to just in the polar regions as was previously assumed). But this result could have significant implications for global climate, namely that it may depend more on surface buoyancy fluxes in the Indo-Pacific than is usually assumed. Scientists are still working to understand the processes that drive this global system. The results from this study help reframe the way we think about the controls on the GOC. Accurately describing these processes is important because changes in the circulation affect the rate of heat and carbon uptake by the ocean.

Discussion

No comments yet.

Post a Comment

Instagram

  • by oceanbites 2 weeks ago
    Not all outdoor science is fieldwork. Some of the best days in the lab can be setting up experiments, especially when you get to do it outdoors. It’s an exciting mix of problem solving, precision, preparation, and teamwork. Here is
  • by oceanbites 1 month 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 2 months 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 3 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 3 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 3 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 4 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 4 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 4 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 5 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 5 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 5 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 6 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 6 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 7 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 7 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 8 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 8 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 9 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 9 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
WP2Social Auto Publish Powered By : XYZScripts.com