sea level change
Scientific and general term for changes in sea level, including long-term trends and short-term fluctuations.
Sea level change due to global warming has become a problem.
We are observing sea level changes in this region over the long term.
海面上昇 specifically means 'sea level rise', while 海面変動 is a broader term encompassing both rise and fall.
Compound of 海面 (sea surface) and 変動 (change, fluctuation).