Decadal climate variability influences the frequency and severity of many natural hazards (e.g., drought), with considerable human and ecological impacts. Understanding observed changes and predicting future impacts relies upon an understanding of the physical processes and any changes in their variability and relationship over time. However, identifying such changes requires very long observational records. Tide gauge sea level measurements provide a detailed, but indirect, record of climate change over the last century (and in a few places around the globe, even earlier).
In a recently accepted paper, AER Senior Staff Scientist Dr. Christopher Little employed a large set of long tide gauge records to show that decadal-timescale coastal sea level variability increased dramatically in the second half of the 20th century, in widely-separated geographic locations. The figure shows an example, with tide gauge data from Seattle and New York City. Using an atmospheric reanalysis of 20th century surface climate, Dr. Little found that the increased coherence after 1960 was driven by a shift in the amplitude, spatial pattern, and inter-basin coherence, of atmospheric pressure, wind, and sea surface temperatures.
Sea level at the Seattle (orange line, in cm) and New York City (blue) tide gauges over the 1900-2019 period, and b) their magnitude-squared wavelet coherence. Note the dramatic increase in coherence between 1960 and 1990. Arrows in (b) indicate the phase relationship (arrows point up if Seattle leads by 90◦; right if timeseries are in phase)
Link / Citation: Coastal sea level observations record the 20th century enhancement of decadal climate variability
J. Climate, Accepted for Publication