Natural oscillations and trends in long-term tide gauge records from the Pacific

Recognition of climate patterns is needed to characterise and understand the various climate mechanisms that culminate in the behaviour of the atmosphere or the ocean. The analysis of the periodic patterns in the oscillating sea levels is an important step in determining the presence or absence of non-periodic accelerating behaviours due to global warming or other effects. This is true for periodic patterns with a multi-decadal scale. Fast periodic (sub-decadal) patterns would not matter much if one is looking at long range accelerations. The analysis of high quality tide gauge records of the Pacific spanning more than 100 yr permits to evidence the multi-decadal oscillations of sea levels and their influence on the sea level rate of rise that may be computed by a linear fitting with different time windows. Without at least 65–70 yr of recorded data, the computed sea level rate of rise differs considerably from the actual long-term sea level rate of rise. These high quality long-term tide gauges show a non-accelerating oscillating behaviour with different periodicities in different locations. This result is consistent with a picture of locally and globally oscillating sea levels without any major sign of sharp positive accelerations at the present time.