A new sea level record set in Washington?

Every few weeks I fire up a few Matlab-based tools that I've assembled to check in on what is going on with coastal water levels in Washington.  And a few weeks ago I noted an interesting milestone, the annually averaged water level in Seattle (from the Seattle tide gauge) set a new record high last year:

Check out the top panel, which is the mean sea level from the 2017 calendar year.  The previous record mean sea level was 2.120 meters relative to local MLLW, set in 1983 during that year's extreme El Nino.  Last year, by my calculation, Seattle hit an average sea level of 2.122 meters.

The subsequent two panels break that average down by season.

If we drill down further we see some interesting distinctions between WHY the 2017 average was so high versus the previous record from 1983.  Below are the same data as above, except showing the monthly averages, expressed as anomalies from the long-term seasonally-corrected average:

Focus in particular on the bottom panel, which is the monthly mean sea level anomaly.   So the intriguing thing is that while the record for 1983 seems to have been set by having a few months early in the year with really high average sea level, the average in 2017 seems to have been set by having a lot of months of somewhat above average sea level.

So its clear from the trends on these plots that relative sea level is rising in Seattle, which isn't a surprise to anyone that has been paying attention to the tide gauge data.  Is this new record due to pure sea level rise, versus subsidence of the land that appears to be happening in Seattle?  I will leave the fuller exploration of that till a later date, but wanted to quickly show the same annual water level estimates from Friday Harbor, just for comparison.  Our preliminary analysis suggests little, if any, vertical land movement in Friday Harbor, whereas Seattle appear to be subsiding.  Here it is:

So here you still see a trend - again not a surprise given NOAA's own analysis, but here appears to be entirely due to water level actually rising (not land falling).  And you will also note that 2017's average water level wasn't the highest on record...1983 retains its record by a good bit.