Monitoring phytoplankton dynamics in Nuup Kangerlua with ocean color remote

The MarineBasis Nuuk Monitoring Programme has performed monthly sampling of hydrography, water chemistry and phytoplankton in Nuup Kangerlua for over 15 years, which may not capture changes in phytoplankton communities occurring at shorter time windows. Likewise, the sampling location is limited to a single station which may not cover the patchy phytoplankton distribution. Here, we investigate the performance of Sentinel-3 (S3) chlorophyll-a (Chl-a) estimates (2016-2022) in relation to in situ data collected in Nuup Kangerlua with the aim to use S3 data to increase both spatial and temporal coverage. Overall, the S3 estimates were significantly correlated with the in situ measurements, with a few exceptions: during spring, when in situ measurements report the highest Chl-a values that are underestimated by S3; and during late-summer and autumn, when Chl-a values are low but with an overestimation by S3, likely due to the presence of glacier flour (silt) in the water.