Sea Level Changes: Natural Causes and Time Scales

What naturally causes sea level to change at long (multi-million year), medium (multi-thousand year), and short (100-year) time scales?

How do various natural factors contribute to sea level changes at different time scales?

Sea Level Changes: Natural Causes and Time Scales

Sea level changes are influenced by different natural factors at various time scales. Let's explore how these factors impact sea level over long (multi-million years), medium (multi-thousand years), and short (100-year) time scales.

Long Time Scale (Multi-Million Years)

At a long time scale, sea level changes are primarily driven by tectonic processes. Plate tectonics, the movement of Earth's lithosphere, can cause the uplift or subsidence of the Earth's crust. This movement affects the volume of ocean basins, leading to fluctuations in sea level. For example, the formation and fragmentation of supercontinents like Pangaea can result in significant sea level changes over millions of years.

Medium Time Scale (Multi-Thousand Years)

On a medium time scale, sea level changes are influenced by factors such as climate change and the melting of ice sheets. Changes in global temperature can cause seawater to expand or contract, affecting sea level. Moreover, the melting of large ice sheets, particularly in Antarctica and Greenland, contributes to sea level rise over thousands of years.

Short Time Scale (100 Years)

At a short time scale, human-induced activities significantly impact sea level changes. Activities like burning fossil fuels and deforestation release greenhouse gases into the atmosphere, leading to global warming. This results in the expansion of seawater due to thermal heating and accelerated melting of glaciers and ice caps, causing a rapid rise in sea level over a century.