Earth's hypsometry and what it tells us about global sea level
Bibliographic record
Abstract
• Earth's hypsometry shows a prominene maximum ∼2–5 m above the sea surface. • We explore how this maximum evolved over a glacial cycle and into the future. • Holocene glacial isostatic adjustment raised the maximum from the sea surface. • Residual glacial isostatic adjustment will raise the maximum a further ∼2 m. • Alternatively the maximum may reflect a longer-term mean state of earth's sea level. Over geological time scales, the combination of solid-Earth deformation and climate-dependent surface processes have resulted in a distinct hypsometry (distribution of surface area with elevation) on Earth, with the highest concentration of surface area focused near the present-day sea surface. However, in addition to a single, well-defined maximum at the present-day sea surface, Earth's hypsometry is also characterized by a prominent maximum ∼2–5 m above this level, with the range accounting for uncertainties in recent digital elevation models. Here we explore the nature of this enigmatic maximum and examine, using a gravitationally self-consistent model of ice-age sea-level change, how it evolved over the last glacial cycle and may evolve moving towards a near-ice-free future. We argue that the hypsometric maximum captures topographic conditions at the end of the last deglaciation phase and subsequent glacial isostatic adjustment (GIA) raised it from the sea surface to its present-day elevation. Moreover, ongoing GIA will raise the maximum a further ∼2 m in the absence of future ice mass loss. If a portion of the hypsometric maximum has persisted for longer than Holocene time scales, the resulting GIA-converged elevation of the hypsometric maximum at +4–7 m above the sea surface implies a longer-term mean state of the Earth that may reflect lower ice volumes, trends in erosion, dynamic topography, or a combination of these. The signature of these various contributions on present-day hypsometry is intimately connected to the time scale of erosional and depositional processes near shorelines.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.000 | 0.003 |
| Scholarly communication | 0.003 | 0.007 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".