Biogeochemical variations at the Porcupine Abyssal Plain sustained Observatory in the northeast Atlantic Ocean, from weekly to inter-annual timescales

[摘要] We present high-resolution autonomous measurements of carbon dioxide partialpressure p(CO₂) taken in situ at the Porcupine Abyssal Plain sustainedObservatory (PAP-SO) in the northeast Atlantic (49° N,16.5° W; water depth of 4850 m) for the period 2010–2012.Measurements of p(CO₂) made at 30 m depth on a sensor frame arecompared with other autonomous biogeochemical measurements at that depth(including chlorophyll a fluorescence and nitrate concentration data) toanalyse weekly to seasonal controls on p(CO₂) flux in the inter-gyreregion of the North Atlantic. Comparisons are also made with in situ regionaltime series data from a ship of opportunity and mixed layer depth (MLD)measurements from profiling Argo floats. There is a persistent under-saturation of CO₂ in surface waters throughout the year which gives riseto a perennial CO₂ sink. Comparison with an earlier data set collected atthe site (2003–2005) confirms seasonal and inter-annual changes in surfaceseawater chemistry. There is year-to-year variability in the timing of deepwinter mixing and the intensity of the spring bloom.

The 2010–2012 period shows an overall increase in p(CO₂) values whencompared to the 2003–2005 period as would be expected from increases due toanthropogenic CO₂ emissions. The surface temperature, wind speed and MLDmeasurements are similar for both periods of time. Future work shouldincorporate daily CO₂ flux measurements made using CO₂ sensors at 1 mdepth and the in situ wind speed data now available from the UK MetOffice Buoy.

[学科分类] 地球化学与岩石