RSS Discovery Cruise 341, 08 Jul – 13 Aug 2009. Porcupine Abyssal Plain time series process study

Abstract

The Biological Carbon Pump (BCP) is a major feature of the global carbon transporting approximately 10GT C yr-1 from the ocean surface to the interior mainly via the sinking of particles with an organic component. The scale of the BCP requires good year-round measurements of its functioning. Moreover, the BCP’s susceptibility to global change means that we need better information on how its climate sensitive elements function and how its poorly parameterised elements operate. These three requirements map directly onto the objectives of this cruise, which will be undertaken using Oceans 2025 funding at the Porcupine Abyssal Plain (PAP) site. The PAP site (47oN, 16.5oW) is the location of a time series of observations from surface to seafloor compiled by IOS, GDD and now NOCS over the last 20 years (Lampitt et al., 2001). A summary of these observations, together with descriptions of surface water biogeochemistry in the region from a cruise in 2005, is currently being published as a special issue of Deep-Sea Research II. The PAP site is close to the site of the JGOFS north Atlantic Bloom experiment and the French POMME programme and is a waypoint on the Atlantic Meridional Transect programme (SO1 in Oceans 2025). There is therefore a rich wealth of previous observations in which our 2009 observations can be grounded.
Objectives:
1) To recover and redeploy the PAP site observatory (Theme 10 of Oceans 2025)
2) To compile a vertical carbon budget for the PAP site with particular focus on the process of remineralisation in the mesopelagic (100 – 1000 m) and on the mechanisms leading to export from the upper ocean (Themes 2, 5 of Oceans 2025)
3) To quantify climate sensitive elements of the BCP at the PAP site, particularly the physical processes responsible for introducing nutrients to the upper water column, which combine to set the maximum level of export (Theme 2 of Oceans 2025)
Of these, 1) was partially successful, 2) was successful, 3) was unsuccessful.

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