Determining Atlantic Ocean province 1 variability 2

12 The Atlantic Meridional Transect (AMT) series of twenty-five cruises over the past twenty years has 13 produced a rich depth-resolved biogeochemical in situ data resource consisting of a wealth of essential 14 core variables. These multiple core datasets, key to the operation of AMT, such as temperature, 15 salinity, oxygen and inorganic nutrients, are often only used as ancillary measurements for 16 contextualising hypothesis-driven process studies. In this paper these core in situ variables, alongside 17 data drawn from satellite Earth Observation (EO) and modelling, have been analysed to determine 18 characteristic oceanic province variability encountered over the last twenty years on the AMT through 19 the Atlantic Ocean. The EO and modelling analysis shows the variability of key environmental variables 20 in each province, such as surface currents, the net heat flux and subsequent large scale biological 21 responses, such as primary production. The in situ core dataset analysis allows the variability in 22 features such as the tropical oxygen minimum zone to be quantified as well as showing clear 23 differences between the provinces in nutrient stoichiometry. Such observations and relationships can 24 be used within basin scale biogeochemical models to set realistic variability bounds. 25