Theory 28/Earth, Climate & Energy /Sea level
Sea Level Hides a Groundwater Term
Sea level is budgeted from ice and heat. Water pumped from the ground ends up in the ocean too.
A substantial part of recent sea level rise comes from groundwater depletion reaching a threshold at which aquifers compact irreversibly, so the rise should accelerate as aquifers cross it rather than tracking thermal expansion alone.
01The evidence
The sea level budget has a residual that is not closed by ice and thermal expansion, and groundwater depletion is large enough to contribute.
02The tension
Budgets treat groundwater as a small correction, and compaction is treated as local subsidence rather than as a global contribution.
03The mechanism
Water pumped from an aquifer either evapotranspires or reaches the ocean. Once an aquifer passes the compaction threshold, storage capacity is lost permanently, so the extracted water becomes a permanent addition to ocean volume.
That makes the threshold the determinant, and predicts an acceleration in the groundwater term as aquifers compact.
04What this is not
Those budgets omit the groundwater term. This includes it with a threshold, which explains the residual.
05Predictions
- P1The budget residual should track groundwater depletion.
- P2Rise should accelerate as aquifers compact.
- P3Compaction should be irreversible.
06Refutation
A closed budget without groundwater would remove the term.
07What it changes
It would change sea level projections.