Maya rainfall became harder to forecast after 500 CE
A Belize speleothem shows seasonal rainfall predictability collapsing after 500 CE and bottoming in the Terminal Classic, alongside drought.
Source
Decline in seasonal predictability potentially destabilized Classic Maya societies
Study at a glance
- Design
- Other — Sub-annual speleothem δ13C analysis of seasonal rainfall predictability over 1600 years
- N
- Single Yok Balum YOK-G speleothem record spanning ~1600 years
- Population
- Seasonal hydroclimate recorded in Yok Balum Cave, Belize
- Outcome
- Collapse of seasonal rainfall predictability during the Terminal Classic drought
Structured fields used in claim comparison tables when every cited study has a complete layer.
What they did
Authors ran ensemble COPRA age models, wavelets, and recurrence plots on sub-annually resolved Yok Balum YOK-G δ13C (and δ18O) to measure seasonal-cycle strength and year-to-year predictability over 1600 years.
What they found
Drying began ~500 CE and peaked 700–900 CE. Seasonal predictability τpred fell below significance between 800 and 1000 CE, after an earlier decline from 500 CE. Toy-model tests show sampling resolution cannot explain most of the drop. Predictability later recovered ~1050–1200 CE.
The limits
What it doesn't show
Speleothem δ13C mixes infiltration, PCP, and cave processes; societal collapse is correlated, not proven causal; a one-year drought crop-loss figure is from an ecological scenario, not the cave record itself.
Key terms
- YOK-G
- Speleothem from Yok Balum Cave, southern Belize.
- Seasonal predictability
- Year-to-year similarity of the seasonal rainfall cycle (τpred from recurrence plots).
- Prior calcite precipitation
- CO2 degassing and calcite formation in the epikarst that enriches drip δ13C when it is dry.
- Terminal Classic
- Maya interval of political disintegration around 850–1000 CE.
- ITCZ
- Rain belt whose summer northward shift brings Belize’s wet season.
Flashcards
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Local seasonal proxy:
Common questions
What proxy records seasonality?
Sub-annual speleothem δ13C at Yok Balum.
When does τpred collapse?
Below significance 800–1000 CE, after decline from 500 CE.
Wet-season rain totals cited?
400–700 mm/month vs 40–70 mm in the dry season.
Is it only a sampling artifact?
Downsampling experiments explain only part of the drop.
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