Dr Aron Meltzner Explains Why SE Asia may be at Risk of a Disastrous Flooding

Dr Aron Meltzner Explains Why SE Asia may be at Risk of a Disastrous Flooding

  • EOS News
10 Feb 2017

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EOS scientist, Dr Aron Meltzner, working on a microatoll during an earlier research expedition (Source: Imam Suprihanto)

A new study led by Dr Aron Meltzner, Senior Research Fellow from the Earth Observatory of Singapore (EOS), was published today in Nature Communications.

Using a method of remarkable precision (measuring the concentric growth rings of coral microatolls) to determine past sea levels, Dr Meltzner and a team of scientists from EOS, the Indonesian Institute of Sciences (LIPI), and Rutgers University in the United States, discovered that sea level in Southeast Asia rose significantly 6,000 years ago.

In the Q&A below, Dr Meltzner explains why the occurrence of such an event in the past means that it could happen again in the future, and what it could mean for the populations living in low-lying coastal areas in Southeast Asia.

Q&A with Dr Aron Meltzner:

Q1. What were the natural factors that drove this rapid change 6,000 years ago?

We suspect that century-scale changes in the intensity of the monsoon and/or in the intensity of ENSO (El Niño/Southern Oscillation) played a big role. Unfortunately, the resolution of paleoclimate proxy data (the geological data that gives scientists information about how climate varied in the past) in this part of the world over that time period is not yet good enough that it allows us to make any definitive correlations. That's a problem we and some colleagues of ours are currently looking into.

Q2. How localised were these fluctuations in sea level? Did they extend throughout much of Southeast Asia?

Because we see similar fluctuations at the same time along the southern coast of China, we argue that it affected much or all of the Sunda Shelf and the South China Sea – so, likely the area from Jakarta to Hong Kong, including Singapore and the coast of Vietnam, among other places in the region. 

Q3. Can you explain to us the methods you used?

The data come from coral microatolls. These are remarkably precise proxies for (recorders of) relative sea level, because their upward growth is precisely limited by exposure at extreme low tide. These microatolls are annually banded, so we can count the bands like tree rings, and figure out where the lowest tides were each year. This precision, both in terms of timing and elevation, allows us to track past sea level in unprecedented detail.

A microatoll near Belitung Island in Indonesia (Source: Aron Meltzner) 

Q4. What implications does this have for low-lying areas of Southeast Asia today?

If it happened in the past, it could happen again. And when it happened 6,000 years ago, there was no human-induced climate change going on. So if it were to happen again, this regional phenomenon would happen independently of, and on top of, the global sea level rise that is anticipated due to climate change.

Southeast Asia is one of the most densely populated parts of the Earth, with its population living disproportionately in low-lying coastal areas. So, the bottom line, our study shows that there are plausible scenarios in which this highly exposed population in Southeast Asia could see rates and magnitudes of sea-level rise that far exceed those already projected due to climate change.

Q5. Are there equal chances of similar rises or fluctuations happening today as 6,000 years ago, or has the situation significantly changed?

I don't think we (the scientific community) have an adequate understanding of how sea level behaves at a regional spatial scale, on multidecadal timescales. Certainly, one of the next challenges for us – and for the scientific community in general – is to understand what drove these fluctuations 6,000 years ago. But, given the limitations of our present understanding, I would say that our logic should be that if it happened in the past, it could happen again sometime in the future.

Q6. Could the current rise in sea level be due to natural causes?

There's an important distinction between the sea level changes that occurred more than 6,000 years ago and the changes that have occurred in recent decades to centuries. The changes more than 6,000 years ago were likely regional in scope (affecting mainly Southeast Asia), and there is NO evidence that they were accompanied by the melting of ice caps and glaciers. The recent changes, in contrast, are global, and are clearly accompanied by the melting of ice caps and glaciers. So these are different phenomena, but they're not necessarily mutually exclusive.

In other words, a repeat of what we observed more than 6,000 years ago could happen in the future, and if it does, it would occur on top of, and potentially exacerbate the effects of, projected sea-level rise due to climate change. This could be a "double whammy" for Southeast Asia.

Q7. Should coastal cities be taking extra precautions against possible rapid sea level rise?

Absolutely. They should already be taking precautions, because we know sea-level rise will happen due to climate change – that's inevitable. But this study suggests that, at least in Southeast Asia, there are plausible scenarios in which sea level could rise much more, and much more quickly, than we had previously realised.