AT38 Behrenfeld "NAAMES"

Ship

Cruise Party

Departure: Aug 30, 2017

Arrival: Sep 24, 2017

Operations Area

Science Objectives

The North Atlantic Aerosols and Marine Ecosystems Study (NAAMES) is an interdisciplinary investigation addressing two primary science goals: (1) Define environmental and ecological controls on plankton communities and (2) Define linkages between ocean ecosystem properties and biogenic aerosols. Within these two broad goals, the NAAMES investigation focuses on identifying environment-ecosystem-aerosol interdependencies in the climate-sensitive North Atlantic. This ocean region hosts the largest annual plankton bloom in the global ocean and its impact on Earth’s radiative balance is particularly sensitive to biogenic aerosol emissions. Specific baseline science objectives of NAAMES are to (1) Characterize plankton ecosystem properties during primary phases of the annual cycle in the North Atlantic and their dependence on environmental forcings, (2) Determine how primary phases of the North Atlantic annual plankton cycle interact to recreate each year the conditions for an annual bloom, and (3) Resolve how remote marine aerosols and boundary layer clouds are influenced by plankton ecosystems in the North Atlantic. These objectives are accomplished by coupling autonomous in situ and satellite measurements sustained throughout the NAAMES investigation with short-term, coordinated ship and airborne campaigns that target critical events in the annual plankton cycle and focus on detailed system characterization. These direct observations are integrated with climate-ecosystem modeling to create a process-based understanding that allows improved interpretation of historical data records and improved predictions of future change.

Science Activities

The NAAMES investigation has a duration of 5 years and involves 4 field campaigns.  Each field campaign will share a common observation profile.  The first and second campaigns were conducted in November 2015 and May 2016, respectively, on the UNOLS R/V Atlantis.  For each campaign, ship-based measurements are accompanied by aircraft measurements.  The aircraft is a NASA C-130 stationed in Saint John’s Bay, Canada. The Atlantis is required for each field campaign due to requirements for foreward deck space for a full-sized aerosols van, deck space for a radioisotope van, and the large scientific complement (34 berths).  This global class vessel is also advantageous for the NAAMES project on account of sea-worthiness during field studies that span the annual cycle and familiarity of the science team gained during the first two campaigns.

Each field campaign involves a 26-day, roughly triangular-shaped ship transect. The ship’s direction around the transect triangle is scientifically irrelevant, allowing real-time adjustments based on prevailing and forecasted weather conditions and sea-states. Assuming a counterclockwise direction, the ship proceeds from Woods Hole to the turning point at 40° N. During this outbound leg, underway sampling is conducted, but not regular overboard deployments.  It is beneficial to make at least one stop during the outbound transect to conduct a ‘shake-down’ station of overboard operations.  Following the turn northward, the full complement of ship-based measurements begins and continues until the northern-most turning point (~55° to 60°N). During this primary latitudinal science leg, daily operations involve a sampling station that begins near dawn and continues through the day.  Station operations  include multiple CTD/Rosette casts.  Optical and other instruments mounted on the rosette for shallow casts but have depth limits <2000 m and will need to be removed before a deep cast.  Following a deep cast, additional shallow casts are conducted for water sampling and underwater light measurements.  Also during station, measurements will be made of downwelling light properties and water leaving radiances.  Once the primary science transect is complete and the northern-most turning point is reached, the return transect begins, with continuous in-line measurements conducted until the day before port arrival, but no additional station occupations anticipated.

In addition to water sampling and flow through seawater measurements, another key component of the NAAMES investigation is the measurement of aerosols.  For this aspect, key measurements are conducted from the Aersosols Van, located on the forward deck of the ship.  Aerosol measurements are conducted continuously while the wind is from the forward direction. These measurement have to be terminated when the wind is from the backward direction, due to contamination from the ship.  Thus, it is desired to keep the ship orientation favorable for aerosol samples for the greatest fraction of the time feasible (understanding that ship orientation during overboard castings is dictated by sea state and wire angle). 

Also during the field campaigns, deployments are made of autonomous profiling floats and surface drifters.  Deployments will occur along the N-S primary latitudinal science transect, with exact location dependent on station location and real-time information on regional mesoscale eddies.  Surface drifter deployments will target mesoscale eddy centers and will provide water parcel tracking capabilities that inform flight patterns for the C-130.   

Airborne deployments accompanying the ship measurements focus on the primary N-S latitudinal transect.  The airborne measurements include in situ aerosol sampling and remote sensing measurements with a hyperspectral ocean color sensor, a high resolution lidar, a polarimeter, and a downwelling irradiance sensor.  Aircraft measurements need to be highly coordinated with the ship, so regular communications between the two platforms is essential. Aircraft measurements begin shortly after takeoff, and continue during the transect to the ship.  Once arriving at the ship, a diversity of flight patterns are followed to characterize horizontal and vertical variability in ocean ecosystem and aerosol properties.  The aircraft transect also includes fly-overs of regions previously sampled by the ship, as tracked by the surface drifters.  These drifters essentially provide a ‘bread crumb trail’ that allows the aircraft to follow changes in system properties well after the ship has departed a given sampling station.  Once the primary science measurements are complete along the ship transect, the aircraft returns to base.

Additional Info

Stations:

Supporting documentation:

Shipboard Equipment

Shipboard Communication

CTD/Water Sampling

Critical CTD Sensors

Hydrographic Analysis Equipment

MET Sensors

Sample Storage

Navigation

Navigation

Winches

Standard Oceanographic Cables

Portable Vans

Checklist

Checklist