<human>:  How does global warming affect sea levels?
<bot>: Global warming causes the ocean to expand due to thermal expansion, as well as increased melting of land-based ice sheets, glaciers, and ice caps. This leads to a rise in sea levels, which can cause flooding in coastal areas and a decrease in available coastline. Additionally, global warming can have an impact on ocean circulation, and can cause dramatic changes in the temperature and salinity of the ocean. All of these changes can have a ripple effect on marine ecosystems and can lead to alterations in the balance of species in the ocean.