you're reading...

Book Review

The Indian Ocean Dipole: How Climate Change affects South East Asia and Beyond

Reviewing: Abram, N.J., Wright, N.M., Ellis, B. et al. Coupling of Indo-Pacific climate variability over the last millennium. Nature 579, 385–392 (2020).

Often Overlooked: The Indo-Pacific

When we read about climate change impacting our society, the media typically covers droughts in California, hurricanes arriving in Florida, or maybe even heat waves in Europe. While these events are important to the many millions living there, our Eurocentric focus on global warming often neglects other regions of the world that potentially deserve more attention. For example, in the map below, you might be surprised to learn that more people in the world live inside the circle surrounding South East Asia—a region termed the Indo-Pacific—than outside of it! In a recent study, Dr. Abram and others investigated how climate change is affecting the Indo-Pacific, with important implications for the billions of people who call this part of the world home.

A global map with a circle marking the Indo-Pacific region. More people live inside than outside of the circle. (Credit: Stephen Haptonstahl)

The Indian Ocean Dipole (IOD)

One of the most important climate phenomena that affects the Indo-Pacific is the El-Nino Southern Oscillation, (click here for a quick overview).  Equally as important is the Indian Ocean Dipole (IOD). Very briefly, the Indian Ocean Dipole is measured as east-west temperature differences in the Indian Ocean just like the El Nino for the Pacific. During a so-called “positive IOD event”, the Indo-Pacific is much cooler and receives less rain, leading to droughts, while the East African coast is much warmer and receives more rain, which can cause floods (see below).

Diagram showing the temperature anomalies during a Positive IOD event, with potential natural disasters on both sides of the Indian Ocean (Image Credit: Australian Bureau of Meteorology)

As you may recall, in January and February Australia suffered multiple massive wildfires that devastated the country. Many climate scientists point to the extreme positive IOD event in late 2019 as a major contributor to the lack of rainfall and terrible wildfire season that followed.

Wildfires raging in Bairnsdale, Australia in December of 2019 (Image Credit: Glen Moery via AP)

In recent years, scientists have theorized that 21st century global warming is increasing the frequency of extreme positive IOD events, which would have huge implications for the people of the Indo-Pacific region. To prove this hypothesis though, we need to get an accurate sense of long-term natural IOD variability and see if the number of positive IOD events in recent years has been unprecedented.

Corals Provide the Answer

Because accurate records of Indian ocean sea surface temperature extend back only a few decades, we need to look into the past to reconstruct the long-term signal of IOD. This is why Dr. Abram and others recovered samples of fossilized Porites corals from the Mentawai Islands off the coast of Sumatra to better understand the IOD. The authors chose to sample corals from this location specifically because it’s been shown that sea surface temperatures off the coast of Sumatra are very strongly correlated with the IOD. If we can get a historical record of sea surface temperatures from corals then we can see how IOD has varied in the past.

Living Porites corals from the Caribbean. Corals are like logbooks that record sea temperatures of the past. Geochemists can analyze them to reconstruct past environmental conditions (Image Credit: Wikimedia Commons)

Results: Climate Change Increasing IOD Frequency

Dr. Abram and her colleagues measured the oxygen isotopic ratio of multiple fossil corals from the Mentawai Islands region and were able to reconstruct a semi-continuous record of IOD variability over the last 1,000 years.

They found that extreme positive IOD events occurred 4 times in the last 60 years.  Given that the same extreme events had occurred only 6 times in the entire preceding 1,000 years, Abram and others take this as strong evidence that extreme positive IOD events have been becoming more frequent in recent decades.  This increase is likely the result of global warming.

An unexpected finding from their study came when the scientists compared the coral record of IOD variability to similar coral records of El Nino variability in the Pacific Ocean. They found that over the last millennium, IOD and El Nino variability covaried to a remarkable degree. While the coupling of the two climate signals is not airtight—in many cases there are positive IOD years without a strong El Nino, and vice versa—this finding supports theories that propose a strong interconnectedness between the Indian and Pacific Ocean climates.

Looking Forward for the Indo-Pacific

Dr. Abram and coauthors presented a key work of paleoclimate research that has impacted the way we understand the IOD. The research shows that the Indian Ocean Dipole is sensitive to human-caused climate change, leading to more positive IOD events as a result. In addition, the data shows a long-term covariance between the IOD and the El Nino-Southern Oscillation, a relationship that could transform the way we understand tropical climate.

Droughts in Indonesia are potentially becoming more frequent with IOD intensity increasing due to climate change (Greenpeace Southeast Asia

While the paleoclimate community will continue to conduct research to validate these conclusions, government leaders, policy researchers, and agricultural industries should heed these findings as a warning of the potentially devastating effects climate change could induce on this populous area of the world.


No comments yet.

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 3 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 5 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 8 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