Acknowledgments

This cruise and preliminary data report was prepared by Richard Limeburner. We thank the officers and crew of the R/V Oceanus Cruise 345 for their skill and superb assistance that made possible the recovery of 8 moorings and completion of the hydrographic survey. Special thanks to Wil Ostrom for leading the successful mooring deployment operation and George Tupper for maintaining and operating the shipboard scientific equipment and coordinating this instrumentation with the needs of the scientific party.

The GLOBEC research effort is sponsored by the National Science Foundation and the National Oceanic and Atmospheric Administration. Support for Frontal Exchange Processes over Eastern Georges Bank Program as part of the U.S. GLOBEC Northwest Atlantic/Georges Bank Study was provided by NSF research grant OCE-98-06379. All data and results in this report are to be considered preliminary.

Cruise Report

GLOBEC R/V OCEANUS OC345

Table of Contents 2

Purpose and Accomplishment Summary 3

Cruise Results 4

1. Frontal Study Moorings 4

1.1 North Flank Shallow – Mooring site NFS 4

1.2 Eastern Flank – Mooring site EF 4

1.3 North Flank Deep – Mooring site NFD 4

2. Hydrography 5

2.1 Calibration 5

2.2 Hydrographic Station Locations 6

2.3 Near-surface Temperature and Salinity Profiles 6 2.4 T/S plot of all stations 8

Cruise Event Log 9

Cruise Personnel 11

Chief Scientist’s Log of Daily Events 11

Appendix 1 – CTD station profile data 14

Lists of Figures

Figure 1. R/V Oceanus OC345 Cruise Track and Mooring Locations.

Figure 2. CTD Conductivity Sensor calibration

Figure 3. Oceanus 345 CTD station locations

Figure 4. Surface temperature and Salinity, August 1-6, 1999

Figure 5. T/S plot of all CTD stations.

Figures 6-22. CTD profile data

Preliminary Cruise Report

GLOBEC R/V OCEANUS – OC345

US State Department Cruise No. 99-013

Woods Hole to Georges Bank to Woods Hole

August 1-6, 1999

Purpose

The primary purpose of OC345 was to recover instrumented moorings at several sites on the northern and eastern flank of Georges Bank and to conduct CTD and ADCP surveys over the eastern half of the Bank. This NSF program, Frontal Exchange Processes Over Eastern Georges Bank, was designed to focus on frontal processes, which occur over eastern Georges Bank in winter through spring. In particular we want to examine (a) the flow of water and biota onto the Bank along the northeastern flank driven by the strong local semidiurnal tidal currents (which can reach 1.5 m/s during spring tide), winter storms, and the seasonally-evolving density field, and (b) the advection of Scotian shelf water across the Northeast Channel onto the Bank associated with the shelf/slope front and episodic events such as winds and buoyancy pulses.

Accomplishment Summary

The cruise successfully recovered 8 moorings at 3 sites over the north and east flanks of Georges Bank. The ship’s track, mooring locations, and CTD station locations are shown in Figure 1. A total of 33 CTD stations were made during the cruise.

Figure 1. OC345 cruise track, CTD station and mooring locations.

Cruise Results:

Frontal Study Moorings – Dick Limeburner and Charlie Flagg

1.1 North Flank Shallow - Mooring Site NFS

The ship arrived at the NFS mooring site at 1800Z on 8/2/99 and we immediately made a CTD cast. Preparation for recovery of NFS guard buoy C began after the CTD cast and the recovery was completed at 1910Z. There was a large knot of chain near the anchor and about 78 m of chain were measured between this chain knot and the mooring swivel. NFS guard buoy A was recovered at 2058 Z and again there was a large chain knot near the anchor located about 72 m below the wire rope. The NFS subsurface mooring was recovered at 2218Z and all the subsurface instrumentation appeared in good condition. A GPS drifter with drogue centered at 10 m was deployed near the NFS site at 2255Z and we then began making CTD stations along a north/south line passing through the NFS and NFD sites.

At 1020 Z on August 31, 1999 we began recovering the NFS discus mooring. Large tensions were apparent during the recovery and we believe the NFS discus ground chain was also wrapped in a knot near the 5000 lb anchors. We disconnected the mooring below the lowest instrument and steamed to the EF mooring site

Eastern Flank - Mooring Site EF

The guard buoy at the EF mooring site was recovered on August 2, 1999 at 1429Z along with a small fisherman’s buoy. We then began recovering the EF discus mooring at 1658Z. A piece of polypropylene fishnet was caught in the discus bridle and needed to be cut away in order to disconnect the EF discus from the rest of the mooring. We disconnected the mooring below the lowest instrument and began an east/west CTD section during the evening.

1.3 North Flank Deep – Mooring Site NFD

At sunrise on August 3, 1999 we released the anchor on the ADCP frame, but the instrument package remained on the bottom at the NFD site. We decided to recover the NFD discus and then begin dragging operations for the bottom mounted ADCP. The NFD discus was on the deck at 1233Z. Fish line was attached to the discus bridle as well as a collapsed polyform buoy. We disconnected the mooring below the lowest instrument and began the dragging operation for the ADCP. At 1824Z the ADCP surfaced after one hour of dragging and at 1851Z the ADCP was on the deck. Table 1 summarizes the mooring recoveries.

Mooring	ID	Date	Time UTC	Latitude N	Longitude W	Depth m
North Flank Shallow Guard	NFSC	8/2/99	1930	42° 04.80’	66° 42.00’	74
North Flank Shallow Guard	NFSO	8/2/99	2104	42° 04.71’	66° 42.27’	74
North Flank Shallow SubSurf.	NFSSS	8/2/99	2223	42° 04.60’	66° 41.93’	72
North Flank Shallow Discus	NFS	8/3/99	1022	42° 04.49’	66° 42.04’	76
East Flank Guard	EF	8/3/99	1432	41° 44.29’	66° 06.78’	97
East Flank Discus	EF	8/3/99	1658	41° 44.31’	66° 06.53’	100
North Flank Deep Discus	NFD	8/4/99	1233	42° 09.79’	66° 42.19’	160
North Flank Deep ADCP	NFD	8/4/99	1851	42° 10. 25’	66° 42.57’	160

Table 1. OC345 mooring recovery times and positions.

2. HYDROGRAPHY – Dick Limeburner

2.1 Calibration

Standard CTD data was collected during Oceanus 345 with a Sea Bird Electronics SBE-911 profiling CTD measuring pressure, conductivity, temperature, light transmission, fluorescence, turbidity and irradiance. At least one seawater sample was collected at each station for calibration of the conductivity sensor on the SBE-911 CTD. Figure 2 below summarizes the comparison between the conductivity measured by the CTD and the in situ conductivity calculated from the water sample bottle salinity using a Guildline Salinometer. The RMS conductivity difference was 0.0032 s/cm and this offset was not applied to the data.

Figure 2. Differences between the CTD conductivity and the seawater sample conductivity during the cruise.

2.2 Hydrographic Station Locations

A total of 33 CTD stations were completed during the cruise along 3 sections radiating outward from the center of the eastern flank of Georges Bank. The locations of the CTD stations are shown in Figure 3.