why does natural variability in el nino and la nina cause rising sea levels

El Niño and La Niña are part of a natural climate phenomenon known as the El Niño-Southern Oscillation (ENSO) cycle. These events involve fluctuations in a band of sea surface temperatures, which are anomalously warm or cold for long periods of time, and occur across the central and east-central Equatorial Pacific.

1. During El Niño events, the trade winds weaken or even reverse direction. This causes the warmer surface waters in the western Pacific to move towards the eastern Pacific. As a result, the sea level in the eastern Pacific rises.

2. Conversely, during La Niña events, the trade winds are stronger than usual, pushing the warm water towards the western Pacific. This causes a rise in sea level in the western Pacific.

3. The rise in sea level is not uniform across the globe due to these events. Some areas experience a rise in sea level, while others may actually see a drop in sea level.

4. It's also important to note that these events can influence global weather patterns and precipitation, which can indirectly affect sea levels. For example, increased rainfall can lead to higher sea levels.

5. Finally, these events can also cause thermal expansion. Warmer water expands and takes up more space, causing sea levels to rise.

So, while El Niño and La Niña events do cause fluctuations in sea levels, they are part of a natural cycle. The current trend of rising sea levels is more significantly influenced by anthropogenic (human-caused) factors, such as global warming and melting ice caps.