Global sea-level rise is driven by three major processes.

Unchecks extraction of groundwater for irrigation and industrial use turns out to be an important missing factor in past estimates of sea-level changes. It isn’t good news for the future.

#1 Melting of glaciers and ice sheets ~ 66%

Ice currently on land adds new water to the ocean when it melts or flows into it.

Two major components:

Greenland and Antarctic ice sheets

Greenland loses ice through surface melting and increased glacier discharge into the ocean.
In Antarctica, warmer seawater melts floating ice shelves from below. This is negating their restraining effect on glaciers, allowing more land-based ice to flow into the ocean.

Mountain glaciers

Glaciers are shrinking on virtually every continent.
Meltwater eventually reaches the ocean.
Collectively, glaciers make a significant contribution to sea-level rise.

Together, land-ice loss accounts for about two-thirds of global sea-level rise.

Important distinction: Melting floating sea ice in the Arctic and Antarctic makes only a small contribution to sea levels rise because it is already floating in the ocean. It is melting land ice that substantially raises sea level.

Global ice sources

Sea Level 101, Part Two: All Sea Level is "Local" - NASA Science

#2 Thermal expansion ~ 33%

As the ocean absorbs heat from global warming, seawater expands. This is called thermal expansion.

Water molecules move farther apart as their temperature rises.
The amount of water doesn’t increase, but its volume does, pushing the ocean surface upward.
The ocean absorbs more than 90% of the excess heat accumulating in Earth’s climate system.
Thermal expansion currently accounts for roughly one-third of global sea-level rise.

This process is particularly important because warming penetrates progressively deeper into the ocean.

#3 Human extraction diverts more water into the oceans ~ 1%

The third process is less obvious: water is transferred between the land and the ocean. Extraction of groundwater for irrigation and home and industrial use is an important missing piece of the puzzle. Until now, it has not been included in estimates for past and current sea-level changes and for projections of future rises

Groundwater pumping: water extracted from aquifers for agriculture, cities and industry can eventually reach the ocean.
Drainage of wetlands and soils: stored water can be transferred to rivers and ultimately the ocean.
Deforestation and changes in precipitation: alter how much water is temporarily stored on land.

This third component is relatively small compared with thermal expansion and land-ice loss, but it matters when scientists construct the complete global sea-level budget.

Human extraction diverts more water into the ocean