//
you're reading...

Physical oceanography

Return from the deep: three-dimensional pathways of upwelling in the Southern Ocean

Source: Tamsitt, V., Drake, H. F., Morrison, A. K., Talley, L. D., Dufour, C. O., Gray, A. R., … & Weijer, W. (2017). Spiraling pathways of global deep waters to the surface of the Southern Ocean. Nature Communications, 8.

A window to the deep Ocean

Despite covering only 30% of the global ocean area, the Southern Ocean absorbs nearly half of the total carbon dioxide and 75% of the total heat absorbed by the oceans from the atmosphere. By absorbing excess heat and carbon dioxide, the Southern Ocean is damping the effect of global warming. The stability of the future climate depends on the Southern Ocean’s capacity to continue to suck heat out of the atmosphere.

One key reason the Southern Ocean plays such an important role in climate is due to its ability to upwell cold, carbon- and nutrient-rich deep water. Strong winds blowing over the Southern Ocean pull cold, deep water from the ocean abyss to the sea surface, forming a connection between the deep ocean and the atmosphere. Despite the importance of the Southern Ocean upwelling in regulating the climate, the three-dimensional pathways of this upwelling are largely unknown. A new study in Nature Communications combines ocean observations with three state-of-the-art ocean models, revealing the full three-dimensional pathway of deep water to the surface of the Southern Ocean for the first time.

 

Following the flow

A team of researchers from around the U.S. tracked upwelling by releasing virtual floats in the deep ocean in three ocean models, tracking the path they follow to the surface of the Southern Ocean. With many new measurements in the Southern Ocean in recent decades and with advancements in computing power and data assimilation techniques, scientists have developed high-resolution models which reconstruct the ocean circulation, filling in the details between observations using the physics. These models are powerful because they can be used to test how changes in the system, like rising carbon dioxide in the atmosphere or speeding up winds, will change the way the ocean behaves. The models can also be used to track the path of currents by releasing virtual floats in the model and tracking where the flow carries them.

 

Using this technique, a group of researchers did the same float release experiment in three state-of-the-art ocean models, revealing the full three-dimensional pathway of deep water to the surface of the Southern Ocean for the first time. Previously it was thought that deep water returned to the surface broadly all the way around Antarctica. This new study shows that deep water is carried to the Southern Ocean in deep, narrow currents, which meet in the Antarctic Circumpolar Current, like highways meeting and forming a high speed freeway that wraps around Antarctica. Most of the deep currents were already well known, but a new pathway was identified carrying deep water from the Indian Ocean to the Southern Ocean along the southern coast of Australia.

Figure 1 from Tamsitt et al. 2017. Three-dimensional pathways of deep water upwelling from the Atlantic Ocean (color; depth in m) over Southern Ocean topography (grey). Panel a) shows the depth of the relatively warm signature of Atlantic deep water spiraling southward and upward toward Antarctica in an ocean model, b) shows the pathways from virtual floats tracked in an ocean model, and c) shows two examples of virtual float trajectories upwelling from the eastern and western Atlantic to the sea surface.

Upwelling hot spots

As well as looking at the pathways from the Atlantic, Indian and Pacific to the Southern Ocean, the researchers looked at how the upwelling was related to undersea topography. Scientists have found that large undersea ridges and mountains are very important for mixing water across strong fronts, which usually act as a strong boundary. When the strong current interacts with these ridges and mountains, the current becomes unstable and generates strong eddies, which are efficient at driving water southward across the current, moving heat towards Antarctica. Scientists hypothesized that this topography might also be important for upwelling, however, until now, they haven’t determined exactly how this undersea topography affects upwelling of deep water. The virtual floats in the ocean models showed that the deep water spirals southward toward Antarctica and up to the surface with the help of topographic obstacles: when topography creates hotspots of swirling eddies it push water both southward and upward toward the surface. All three models showed the same result: there are five of these major upwelling hotspots associated with large undersea topographic features, which are responsible for most of the upwelling in the Southern Ocean.

Figure 7 from Tamsitt et al. 2017 showing an idealized pathway of upwelling deep water from the Atlantic Ocean to the sea surface (red line). The water spirals southward and upward, and moving southward and up toward the surface when it encounters regions with vigorous ocean eddies (yellow patches) near undersea ridges and mountains (grey).

New insights

These results have identified critical regions for upwelling of deep water, which should be targeted with future research expeditions. The researchers have also shown how the role of ocean eddy hotspots can create chimneys connecting the deep ocean with the surface, where the ocean interacts directly with the atmosphere. Three-dimensional modeling of ocean circulation and eddy hotspots is crucial for understanding the ocean’s ability to absorb heat and carbon dioxide from the atmosphere.

 

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