This dataset represents spatiotemporal variability in coastal pH-variability measured in a nested scale in the sub-Arctic Kobbefjord (64⁰10’ N, 51⁰33’ W) which makes part of the extensive Godthåbsfjordsystem near Nuuk, SW Greenland. A sensor array logging pH, oxygen, photosynthetically active radiation (PAR), temperature and salinity was applied on spatial scales ranging from km-scale across the horizontal extension of the fjord, over 100 m-scale vertically in the fjord, 10-100 m scale between subtidal habitats with and without kelp forests and between vegetated tidal pools and adjacent vegetated shores, to cm-m scale within kelp forests and pH was also measured at mm-scale across boundary layers of macrophyte tissue. In addition, we assessed the temporal variability in pH on diurnal and seasonal scales. Based on pH-measurements combined with relationships between salinity, total alkalinity and dissolved inorganic carbon we also estimated variability of the carbonate saturation state for aragonite Ωarag. Fjord-scale data sets were collected during three field campaigns (19 Apr, 18 Jul, 3 Sep 2013), shallow subtidal habitats and microscale data sets represent an intensive campaign (27 August–6 September 2013) and intertidal data were collected ultimo Aug 2014. Methods are described in detail in Krause-Jensen et al. (2015) which also contains a thorough presentation, analysis and discussion of the results.