you're reading...

Climate Change

Can the ocean take the heat?

Source: Peter J. Gleckler, Paul J. Durack, Ronald J. Stouffer, Gregory C. Johnson and Chris E. Forest (2016). Industrial-era global ocean heat uptake doubles in recent decades. Nature Climate Change. Advance Online Publication. http://dx.doi.org/10.1038/nclimate2915

The blanket thickens

Carbon dioxide and other greenhouse gases act as a protective blanket surrounding our planet, trapping heat on the Earth and making our climate livable. However, as humans are adding more carbon dioxide to the atmosphere by burning fossil fuels, we are making the blanket thicker and trapping extra heat on Earth. 90% of this heat is absorbed by the ocean while the small amount left over warms up our atmosphere. 

The case of the missing heat

Over the past 15 years or so, the temperature of Earth’s atmosphere has not increased significantly despite increases in greenhouse gas levels.  The effect is so dramatic it’s been called the “global warming hiatus.”  Some argue that because the atmosphere didn’t warm significantly over the past decade human-caused global warming is not happening, but this is inconsistent with the basic science of greenhouse gases.

If the heat trapped by greenhouse gases is not staying in the atmosphere, then where is it? The only other place the extra heat can be stored is in the ocean, so a group of scientists made it their mission to figure out how much heat the ocean is sucking up to see if they can account for that missing heat.

DSC_0138 copy-701063

A float (soccom.princeton.edu) which measures temperature as well as other physical and chemical properties in the top 2000 m of the ocean. I recently returned from sea where I deployed this float from an icebreaker in the Southern Ocean.

Clues from the deep

The group of scientists from around the US combined different lines of evidence to try find the missing heat stored in the ocean. The best way to look for the heat is to use direct observations of the temperature of the surface and deep ocean. However, up until the recent development of autonomous underwater robots (Argo), there have been very few measurements of ocean temperature, particularly below the surface of the ocean. Most of these measurements are collected on ships which means that remote and extreme regions like Antarctica have very few observations. This makes accurately calculating the global ocean heat content incredibly challenging.

To get around the difficulties of physically measuring ocean temperatures, the authors used another tool, global climate models, to compare with the numbers they found using historical observations. They used a suite of state-of-the-art models of the ocean, atmosphere and land system to recreate Earth’s climate over the past 150 years. Because the models take a lot of computer time to run, they are a few years behind and the historical simulations only go up to 2005; the team also added a model forecast up to 2015 to compare with the latest ocean observations.


Turning up the heat

Different estimates of ocean heat content from ocean observations from the 1960’s onwards show a steady increase. This increase is stronger near the surface of the ocean where heat can enter the ocean directly from the atmosphere, and more slowly in the deep ocean where the sluggish ocean circulation slowly carries the heat to the seafloor.

Figure 1: Modeled (black) and observed (colored) ocean heat content (Joules) since the beginning of the industrial revolution. The top panel (a) shows the model results with labels showing major volcanic eruptions. The next three panels show the model and observations for the top 700 m (b), 700-2000 m (c), and below 2000 m (d).

There are also periods where temperature decreases suddenly. These quick  dips in the ocean heat content are caused by volcanic eruptions (marked in Figure 1a) which release particles into the upper atmosphere that have a cooling effect on the atmosphere. The model results show similar changes in heat content to the direct observations and with these two lines of evidence agreeing, the scientists are more confident in the results than with the observations alone. Now that they have confidence in the results, the authors set out to see whether the ocean heat content has increased more rapidly in recent decades, and if this can explain the ‘global warming hiatus’.

Looking at how the heat content has changed over the past 150 years, it turns out that half of the total heat has accumulated in the ocean since 1997, near  when the ‘hiatus’ began (Figure 2). They authors also discovered that a large portion (35%) of this heat has been stored in the deep ocean, below 700 m depth.

Figure 2: Ocean heat uptake since the industrial revolution from model simulations. The different colors represent different depth layers of the ocean and the triangles show when major volcanic eruptions occurred, cooling the ocean temporarily. Half of the heat uptake has happened since 1997.

Case not closed

Because the observations of ocean heat content transitioned from mostly ship-based measurements to Argo around 2005, it is very difficult to determine how heat content changed during this transition. For this reason, the scientists do not have conclusive evidence to say for sure that the ocean has stored all of the missing heat from the atmosphere. The evidence from their investigation does show that the ocean is heating up much faster now than a few decades ago, and it is certainly plausible that ocean heating can explain the hiatus. The case is not closed, and this study highlights the need for more ocean observations, especially in the deep ocean, so that in the future the mystery of where the Earth stores heat can be completely solved.



  1. […] excess heat from the atmosphere. The deep ocean in particular acts as an efficient heat sink. The ocean is so good at taking up heat, it has been credited with the so-called “global warming hiatus.” Understanding how the deep […]

Post a Comment


  • by oceanbites 2 months ago
    Happy Earth Day! Take some time today to do something for the planet and appreciate the ocean, which covers 71% of the Earth’s surface.  #EarthDay   #OceanAppreciation   #Oceanbites   #CoastalVibes   #CoastalRI 
  • by oceanbites 3 months 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 4 months 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 5 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 5 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 5 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 6 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 6 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 6 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 7 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 7 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 7 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 7 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 8 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 9 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 9 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 9 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 10 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 11 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 11 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 
WP2Social Auto Publish Powered By : XYZScripts.com