Deployment: AT16

Science Objectives
The overall goal of the project is to examine the transport and export of particulate organic carbon (POC) over the northwest Atlantic Ocean margin.  Specific objectives are to examine the role of the Deep Western Boundary Current in along-margin transport of POC. It is hypothesized that along- and across-margin transport of POC is important for supply of organic carbon to deep-ocean sediments.  Geochemical investigations of organic matter entrained in bottom and intermediate depth suspended particle (nepheloid) layers as well as sinking particles are planned as well as hydrographic surveys in order to place findings within the context of regional physical oceanography. Hydrographic surveys and sampling will occur along 3 across-margin transects in each case extending from the shelf-break to ~ 5000 m water depth (off Nova Scotia, off Cape Cod, and off Cape Hatteras).  The assessments of particle dynamics will be coupled to an existing hydrographic observation program along an ocean section between Cape Cod and Bermuda ('Line W'). The 'Line W' program is focused on the physical characteristics of the region, and provides an accompanying framework for the study of carbon dynamics.

A series of 3 across-margin transects are designed to capture the sources and movement of particulate matter. The proposed sampling program includes CTD hydrocasts and large-volume (up to 1000L) in-situ filtration with McLane submersible pumps. The science plan also calls for deployment of 2 sediment trap moorings and perhaps some sediment coring (multicorer). The intent is to obtain high vertical and spatial resolution filter samples for detailed analysis of particle abundance and characteristics within intermediate-depth and bottom nepheloid layers.

The science implementation plan includes deployment of: Sea-Bird Electronics, Inc. CTD rosette equipped with transmissometer and optical back scatter sensor; Glider Autonomous Underwater Vehicle (AUV) equipped with CTD and optical backscatter sensor; Sea floor-tethered mooring with Deployment of McLane Mark-7 time-series sediment traps; ship's clean seawater intake and McLane submersible pumps (Water Transfer System, WTS).

Funding for cruise AT16 is from NSF award number OCE-0851350.

Cruise information and original data are available from the NSF R2R data catalog.