Pacific Sea Levels- Warming, ENSO, or Wind?

Apparently our Opposition Leader Bill Shorten, his deputy Tanya Plibersek, and immigration spokesman Richard Marles are heading off to the Pacific to discuss “the dangerous consequences of climate change”, all paid for by media baron Harold Mitchell, according to yesterday’s Weekend Australian.
They will visit Papua New Guinea, the Marshall Islands, and Kiribati (pronounced “Kiri-bahss”).
The President of Kiribati leads the complaints about the threat of global warming to his island nation. Kiribati has indeed seen foreshore erosion and salt water intrusion in recent years- just don’t mention causeway construction and underground water extraction.
Time for a reality check.
Sea level rise in Kiribati and the Marshalls has nothing to do with climate change and everything to do with the ENSO cycle, and winds in particular.
In this post I use data from the Australian Bureau of Meteorology’s Pacific Sea Level Monitoring Project at http://www.bom.gov.au/pacific/projects/pslm/. I also use NINO 4 data from http://www.cpc.ncep.noaa.gov/data/indices/sstoi.indices and Trade Wind Index data from http://www.cpc.ncep.noaa.gov/data/indices/wpac850.
Fig. 1: Island nations in the Pacific Sea Level Monitoring Project, also showing the area of the NINO 4 index. (Click graphics to enlarge).

Pacific MSL map
I have converted raw mean sea level data to monthly anomalies from 1995-2014 means, and scaled down NINO 4 and Trade Wind data, in order to make comparison easier.
This figure shows sea level data at all of the islands in the BOM’s Pacific Sea Level Monitoring Project.
Fig. 2: 12 month smoothed sea level anomalies, 1992-2015, for all islands in the Sea Level Monitoring Project. The vertical axis is in metres.

MSL graph all
Point 1: While there is broad agreement on rises and falls, the timing of the rises and falls is very mixed- some rise at the same time as others fall.

This is clearly shown by Kiribati and the Marshalls- when one is rising the other is falling.
Fig. 3: 12 month sea level anomalies at Kiribati and Marshalls, 1992 to 2015.

MSL M & K
Perhaps Mr Shorten can discuss why sea level changes at the Marshalls precede those at Kiribati by many months, such that they are presently moving in opposite directions.
Point 2: There is no doubt that from 1992 to 2015, throughout this region sea levels have been rising: both the Marshalls and Kiribati by 4.8 mm per year. However, since sea level rise occurs at different times, it cannot be due to temperature change. This is further reinforced by the next graphic.
Fig. 4: NINO sea surface temperature anomalies, January 1982- September 2015, 12 month means.

NINO indices
NINO 4 sea surface temperature anomalies since 1982 have almost zero (+0.01C per decade) trend (and the other indices show negative trend in sea surface temperatures). The tropical Pacific has not warmed.
At first glance, sea level change at these islands appears to correlate well with El Ninos and La Ninas, however close analysis shows a much more complex picture.
Fig. 5: 12 month running means of Kiribati sea level anomalies compared to NINO 4

K MSL v NINO4
Note that sea level changes several months before the NINO 4 index.
Fig. 6: 12 month running means of Marshall Islands sea level anomalies compared to the Trade Winds Index.

Tr Winds v MSL Marshalls
Note that the Trade Winds mostly change simultaneously with or some months before sea levels change.
Point 3: Sea level changes at Kiribati precede ENSO events, as measured by the NINO 4 index, but follow or match the Trades at the Marshalls (just to the north of the NINO 4 region).
However, in Figure 3 above, note that sea level anomalies at the Marshalls PRECEDE Kiribati.
So what is the cause of sea level rise in the western Pacific, which is an alarming 4.8mm per year at Kiribati and the Marshall islands?
Fig. 7: Trade Wind Index, December 1992 to September 2015

Trades trend
The Trade Winds have been increasing throughout the period of the Sea Level Monitoring Project, pushing surface water from east to west across the Pacific.
Fig. 8: Western Pacific winds at 1 November 2015

Pacific winds 1Nov 15(From http://earth.nullschool.net/#current/wind/surface/level/orthographic=163.83,1.50,277 )
At Kiribati westerly wind pulses, which help to initiate and strengthen El Ninos, push water against the low coral cay and raise the sea level at the tide gauge, (located on the western side of Tarawa, which is in normal and La Nina years the leeward side).

 

Fig. 9:  Tarawa Atoll

Tarawa atoll
When these winds slacken and trade winds strengthen, the sea level drops. In the rising sea level phase, the westerly winds push warmer water eastwards, and the weaker trades do not bring in as much cooler water from higher latitudes. Thus the rise in sea level at Kiribati precedes a rise in sea surface temperature, and the peak in sea level occurs about 5 months before the peak in NINO 4, one of the El Nino indicators.
Conversely, weaker trade winds bottom out some months before the bottom of sea levels at the Marshalls, which are to the north of the area affected by westerly wind pulses.
Therefore we can reassure Mr Shorten and his pals that sea level rise has little to do with climate change (unless alarmists claim that global warming will lead to stronger La Ninas, which lead to cooler temperatures- but I thought the plan was for more El Ninos).
Sea level rise is largely due to wind. And no doubt Mr Shorten will contribute to that.

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15 Responses to “Pacific Sea Levels- Warming, ENSO, or Wind?”

  1. MorinMoss Says:

    “unless alarmists claim that global warming will lead to stronger La Ninas, which lead to cooler temperatures”

    We’ve had strong and even double-dip La Ninas during the past 20 years with only a mild impact on the global temp anomaly.

    Every La Nina year since the record El Nino of ’98 is as warm or warmer as any year prior except ’97.

  2. kenskingdom Says:

    I guess you could believe anything if your source is Wikipedia.

    • MorinMoss Says:

      “I guess you could believe anything if your source is Wikipedia”

      Which source gives the answers you prefer?

      • easytiger Says:

        If I could interrupt you two fine gentleman.
        I prefer RSS, though it’s shortcoming is it doesn’t go back afr enough, but any other reputable product is fine.
        It seems obvious from your graph that after an el-Nino we get a cooling for a short time.
        If I may say Morin your graph does seem to be very flat since 1997 or so. why is that do you think?

        • MorinMoss Says:

          “If I may say Morin your graph does seem to be very flat since 1997 or so. why is that do you think?”

          I really don’t know but the fact that global temps no longer go through the wild up & down swings of previous decades is & should be very interesting, wouldn’t you say?

          It’s almost as if there’s a setpoint or some control knob that periodically gets adjusted higher & higher and the natural variability of weather applies less strongly than just a couple decades prior.

      • kenskingdom Says:

        UAH or RSS- definitely not Wikipedia! Check plots in previous posts on the pause- nothing like that graph from Wikipedia.

        • MorinMoss Says:

          Wikipedia wasn’t the “source” of that graph; it’s from NOAA’s 2012 global analysis but many sites don’t like hotlinking to their source images so I did it from Wikipedia’s repository instead.

        • MorinMoss Says:

          I’m not clear on why anyone would take satellite plots as gospel given that they don’t measure temperature directly and don’t measure ground temps – which is where we live.
          The satellite records have also required numerous corrections but when ground data is adjusted, it’s because of some scurrilous conspiracy.

  3. kenskingdom Says:

    So Morin, getting back to sea levels in the Pacific, what do you think sea level at Kiribati will be a year from now- higher, lower, or the same as now, and why? I reckon it will be lower- because of the ENSO cycle. The Pacific will be in neutral or La Nina phase by then, trades will be dominant, with less westerly wind bursts on the Equator.

  4. RGB from Oz Says:

    Nice analysis Ken. Love the wind influence. Makes perfect sense. Short time periods (1993 to current) is clearly insufficient to gauge long term sea level trends. Looking at all the tide gauges at Kiribati, I get about 1mm rise per year (1949 to Oct 2015). Last year I created a long record from all of the tide gauges at Kiribati to get a 60+ year trend. https://eyesonbrowne.wordpress.com/2014/04/25/kirabati-sea-level-rising-or-falling/

  5. kenskingdom Says:

    Gday RGB

    Thank you. Yes, I’ve seen your post- I should have referenced it. I wanted to restrict the time to the duration of the sea level project.

  6. RGB from Oz Says:

    All good Ken. I wish I had the time to look more in depth into this stuff, but gotta earn a livi’n. Good to see you have broached it. I was aware of the prevailing wind influence on the tide gauge, but had not made the connection to Nino/Nina phases. Very cool.

  7. daveburton Says:

    Good work, Ken. I’ve added links to your article and to one of your graphs on my web site, here:

    http://www.sealevel.info/resources.html#enso

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