Sea Level Rise Simulator: Thermal Expansion, Glaciers, and Ice Sheet Dynamics

simulation intermediate ~15 min
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Formula

\text{SLR}_{\text{total}} = \Delta H_{\text{thermal}} + \Delta H_{\text{glaciers}} + \Delta H_{\text{ice sheets}}
\Delta H_{\text{thermal}} = \alpha \cdot \Delta T \cdot (1 - e^{-t/\tau})
\Delta H_{\text{ice sheet}} \propto \Delta T^{1.5-2} \cdot t \cdot (1 + t/t_0) \quad (\Delta T > T_{\text{threshold}})
\frac{dH}{dt} = a \cdot (T - T_0) \quad \text{(Rahmstorf semi-empirical)}
Sea level rise is among the most consequential and irreversible impacts of climate change. Unlike temperature, which responds relatively quickly to emission changes, sea level has enormous inertia — the decisions we make this century will determine coastlines for millennia. This simulator decomposes sea level rise into three physical components. Thermal expansion is the most predictable: as ocean water warms, it expands, contributing roughly 0.4 meters per degree of equilibrium warming. This process is well-understood but slow — the deep ocean takes centuries to equilibrate, meaning thermal expansion continues long after temperatures stabilize. Glacier and small ice cap melt is approximately linear with temperature but limited in total: all mountain glaciers contain enough water for about 0.4 meters of sea level rise. Many glaciers are already committed to disappearing. Ice sheet dynamics are the largest source of both potential rise and uncertainty. The Greenland ice sheet contains 7.2 meters of sea level equivalent; the Antarctic ice sheets contain 58 meters. Their response to warming is highly nonlinear, with threshold behavior around 1.5°C (Greenland) and 3°C (West Antarctic Ice Sheet). Below these thresholds, contribution is modest. Above them, marine ice sheet instability and ice cliff collapse can produce accelerating melt rates. Rahmstorf (2007) demonstrated a semi-empirical approach linking the rate of sea level rise to temperature anomaly: dH/dt = a·(T - T₀). This simple model reproduced observed 20th-century sea level rise and projected 0.5–1.4 meters by 2100 under various scenarios — at the high end of what process-based models predicted at the time. The coastline visualization shows the human dimension: even modest sea level rise of 0.5–1 meter threatens hundreds of millions of people in low-lying coastal cities. The nonlinear acceleration of ice sheet contributions means that the difference between 2°C and 4°C of warming is not just twice the flooding — it can be five to ten times worse.

FAQ

What causes sea level rise?

Sea level rise has three main components: (1) Thermal expansion — water expands as it warms, contributing about 40% of observed rise. (2) Glacier and small ice cap melt — contributing about 25%. (3) Ice sheet melt from Greenland and Antarctica — currently contributing about 35% and accelerating. Together, these have raised global sea levels by about 20 cm since 1900.

How much will sea levels rise by 2100?

IPCC AR6 projects 0.28–0.55 m rise under low emissions (SSP1-2.6) and 0.63–1.01 m under very high emissions (SSP5-8.5) by 2100 relative to 1995-2014. However, deep uncertainty in ice sheet dynamics means rises exceeding 2 m cannot be ruled out in high-emission scenarios — a key concern for coastal planning.

Why are ice sheets the biggest uncertainty?

Ice sheet dynamics involve complex processes — marine ice sheet instability, ice cliff collapse, basal melting by warm ocean water — that are difficult to model and may exhibit threshold behavior. Once triggered, these processes can accelerate rapidly. The West Antarctic Ice Sheet is particularly vulnerable because much of its base sits below sea level.

What is committed sea level rise?

Even if greenhouse gas emissions stopped immediately, sea levels would continue rising for centuries due to thermal inertia (the ocean takes time to equilibrate) and slow ice sheet response. Current warming of ~1.2°C has committed us to approximately 1.5–2.5 meters of long-term rise, though most would occur over centuries to millennia.

Sources

Other simulations: Climate Science

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View source on GitHub