The surge residual is the non-tidal component of coastal sea level. It responds to the atmospheric circulation, including the direct effect of atmospheric pressure on the sea surface. Tide gauges have been used to measure the sea level in coastal cities for centuries, with many records dating back to the 19th century or even earlier to times when direct pressure observations were scarce. Therefore, these old tide gauge records may be used as indirect observations of sub-seasonal atmospheric variability that are complementary to other sensors such as barometers. To investigate this claim, the present work relies on the tide gauge record of Brest, western France, and on the members of NOAA's 20th Century Reanalysis (20CRv3), which only assimilates surface pressure observations and uses a numerical weather prediction model. Using simple statistical relationships between surge residuals and local atmospheric pressure, we show that the tide gauge record can help to reveal part of the 19th century atmospheric variability that was uncaught by the pressure-observations-based reanalysis, advocating for the use of early tide gauge records to study past storms. In particular, weighting the 80 reanalysis members based on tide gauge observations indicates that a large number of members seem unlikely, which induces corrections of several tens of hectopascals in the Bay of Biscay. Comparisons with independent pressure observations shed light on the strengths and limitations of the methodology, particularly for the case of wind-driven surge residuals. This calls for the future use of a mixed methodology between data-driven tools and physics-based modeling. Our methodology could be applied to use other types of independent observations (not just tide gauges) as a means of weighting reanalysis ensemble members.