What factor has significantly contributed to the modern rise in global sea levels?

The rise in global sea levels is largely influenced by the thermal expansion of ocean water due to rising temperatures. As global temperatures climb, ocean water absorbs heat and expands. This thermal expansion contributes significantly to sea level rise, accounting for a substantial portion of the increase observed in recent history. The oceans are vast and capable of absorbing a considerable amount of heat, making this process a major contributor to the overall rise in sea levels.

While glacial melting also plays a significant role by adding freshwater to the oceans, thermal expansion represents a direct response to climate change and is ongoing as global temperatures continue to rise. Increased precipitation can impact sea levels but does not have the same direct effect as the thermal expansion of water. Deforestation is primarily linked to other climate issues, such as increased CO2 levels and changes in local ecosystems, rather than directly influencing sea levels on a global scale.