LADC 02

During the late summer and early fall of 2002, LADC conducted acoustic & enviornmental measurements, concurrent with the second leg of the Marine Management Service (MMS) Sperm Whale Seismic Study (SWSS).

The initial area was bounded by 28°N and 29°N Latitude and 88.5°W and 89.5W Longitude. This area was chosen because it included the highest concentration of historical sightings of sperm whales according to information supplied by the National Marine Fisheries Service (NMFS). In addition, much of the environmental information obtained from LADC 01 (e.g., side scan sonar surveys) was still valid for this area and did not need to be repeated in LADC 02. Two tentative tracks were chosen for detailed study within this area. One track was an approximately 20nmi downslope track starting at the 400m contour (28.63°N, 89.08°W) and ending at the 1200m contour (28.33°N, 88.94°W). The other track was approximately 40nmi along the nominal 1100m isobath (28.15°N, 89.22°W to 28.65°N, 88.72°W).

The LADC 02 experiment was planned to coincide with as much of the second leg of the 2002 Sperm Whale Seismic Study (SWSS), funded through the MMS, the Office of Naval Research (ONR), and the International Association of Geophysical Contractors (IAGC), as possible. The second leg of SWSS took place between 19 August and 15 September 2002, and is referred to as the “D-tag experiment” after the digital-recording tags used to obtain data on the movements and physiology of Sperm whales.

Three LADC acoustic moorings (high speed Environmental Acoustic Recording System (EARS) buoys with an associated environmental sensor string) were deployed along the downslope track. The EARS buoys used in LADC 02 were upgraded versions that could record acoustic data for twice the period of the LADC 01 EARS buoys. The EARS buoys each had a single omni-directional hydrophone and an instrument package which autonomously recorded the acoustic signals up to 5859 Hz. The hydrophones for these buoys were tethered 50 m from the bottom. The remainder of the mooring, spanning almost all the rest of the water column up to within approximately 20m of the surface, was devoted to environmental sensors for temperature, conductivity, and pressure. As in LADC 01, deployment sites were chosen for depths of 600m, 800m, and 1000m. The planned deployment sites for LADC 02 were the same as the actual LADC 01 deployment sites.

During LADC02, two named stormed passed through the area. Tropical Storm Isidore passed with 73 nmi of the EARS buoys and Hurricane Lili passed within 116nmi

 

Number of buoys:
3
Locations:

EARS1: 28 ° 23.0425’N, 88° 59.4954’W
EARS2: 28° 30.0489’N, 89° 02.5552’W
EARS3: 28° 33.9916’N, 89° 04.2918’W

Dates:

Leg 1: 27 - 31 Aug 2002
Leg 2: 23 - 24 Oct 2002

Days of recorded data:
EARS1: 49.52 days
EARS2: 22.30 days
EARS3: 56.98 days
Amount of data:

EARS1: 48 Gb
EARS2: 19 Gb
EARS3: 55 Gb

Depth:
EARS1: 1067m
EARS2: 814.5m
EARS3: 620m
Special Events:

Hurricane Lili
Tropical Storm Isidore


On the 600-meter mooring, temperature time series were collected at depths of 70, 95, 120, 170, 270, 370, 470, and 571 m. Additional conductivity time series were collected at 70, 170, and 571 m.

On the 800-meter mooring, temperature and conductivity time series were collected at a 765.5 m depth.

On the 1000-meter mooring, temperature time series were collected at 417, 517, 617, 717, 817, 917, and 1081 m depths. Additional conductivity time series were collected at a depth of 1081 m.

During LADC 02, 26 CTD casts and 30 XBT launches were successfully performed. The entire cruise was safely completed ahead of schedule.