Clamatology

clamSome reporters are showing an interest in a lesser known proxy for climate change: giant clams. Of course, some scientists claim clams prove unprecedented global warming this century. Unsurprising since their funding (clams) depends on sounding the alarms.

For some insight into the connection between clams and climate, here is a paper Giant clam recorders of ENSO variability (here).

Giant clam stable isotope profiles from Papua New Guinea faithfully record all the major El Niño events between 1986 and 2003, thus illustrating the usefulness of this archive to reconstruct past ENSO variability. Elliott et al.

In northern Papua New Guinea precipitation and temperatures are coupled on seasonal and interannual timescales. El Niño periods are associated with lower than average SST and drier conditions, whereas La Niña periods are associated with higher than average SST and wetter conditions. The associated changes in sea water δ18O and SST will thus have cumulative effects on shell δ18O, which will become more positive during El Niño and more negative during La Niña phases.

clam-fig2

Figure 2: Comparison of T. gigas δ18O profile with ENSO index, local temperature and rainfall data. A) NINO3.4 index, (B) 3pt smoothed monthly rainfall anomaly (mm day-1, NASA/GPCPV2) for 146.25°E, 6.25°S, (C) T. gigas δ18O record, (D) Porites δ18O profiles and (E) 3pt smoothed monthly SST anomaly (from IGOSS) for the same grid box as the rainfall data. Y-axes of the δ18O are inverted. The shaded bands indicate El Niño events.

The comparison of the ENSO index with the T. gigas and Porites δ18O records shows that each El Niño event is recorded in the shell and coral profile by isotopic shifts of around 1.0 to 1.2‰ toward more positive values (Fig. 2) reflecting the combined influence of lower temperatures and decreased rainfall. During the El Niño phase of the Southern Oscillation, the region experiences relative drought and slightly reduced SSTs (~-0.2 to -0.5°C anomaly, see Fig. 2). These factors combine to drive skeletal δ18O to heavy values, with SST explaining about 30-50% of the skeletal δ18O range.

Take away message

We show that shells of T. gigas can be used to produce multi-decadal climatic records, hence providing a valuable resource for investigating changes to the frequency and strength of ENSO events in the past. The excellent reproducibility of clam and coral δ18O profiles illustrates the strength of using these archives to reconstruct large-scale hydrographic changes.

Some points worth noting: Clamshell variability is influenced by precipitation as well as water temperature. And water temperatures do not simply correlate to air temperatures. Finally, it is the water heating the air, not the other way around.

The data is good, but the interpretation can be biased by warmist beliefs.

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3 comments

  1. Hifast · December 9

    Reblogged this on Climate Collections.

    Like

  2. oiltranslator · December 9

    So… is that clam in the photo smiling or frowning?

    Like

    • Ron Clutz · December 10

      OilT, it looks to me like a grimace, partly smiley from warm water, partly unhappy from cold water.

      Like

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