The nature and purpose of the trip
My role: sea ice measurements and observations
"Sea Ice Conditions in the Weddell Sea, Jan-Feb 1998," our preliminary cruise report
Other ship activities
The Science Team
Phots
Journal Excerpts

The nature and purpose of the trip
The information in this section was largely culled from "ICD Southern Weddell Sea cruise on HMS Endurance during the 97/98 field season: Cruise Plan" by Dr. Keith Nicholls, British Antarctic Survey.

Near the Antarctic continent, sea ice forms in areas of open water (polynyas), which may be maintained by winds or by latent heat. Because sea ice is fresh compared to the ocean, high salinity water is created as ice forms. This comparatively dense water flows into the cavities beneath the floating ice shelves. When it meets the ice shelf, it melts some of the ice, which mixes to form fresher "ice shelf water," which flows back toward the shelf edge, above the high salinity water. Some of it refreezes onto the underside of the ice shelf, and some of it contributes to the production of Antarctic Bottom Water and therefore helps drive the global thermohaline circulation. Thus, a changing climate affects the formation of sea ice, which affects underside melting rates of the ice shelves, which in turn affects deep water formation and feeds back on the global climate. More from Keith's Letter to Nature.

The purpose of the cruise was to study the distribution and nature of water masses on the southern Weddell continental shelf, and to relate them to energy fluxes between the ocean, ice and atmosphere. This goal was achieved through CTD (current/temperature/depth) sections, bottom pressure measurements, current meter deployment and retrieval, weather balloon releases, atmospheric boundary layer measurements, and observations and measurement of sea ice, both in the central Weddell Sea and along the ice shelf. Two programs were undertaken:

ROPEX (Ronne Polynya Experiment) took place along the Ronne ice shelf. The purpose was to enable year-round estimates of sea ice formation rates and production of associated high salinity shelf water. In addition to measuring flux exhanges between ocean and atmosphere near the polynyas, a detailed survey of the emerging shelf water plume was carried out, and three current meter moorings with several years worth of data were retreived from just in front of the ice shelf.

The intent of OVERFLOW, which took place at the (continental) shelf break northeast of the Filchner ice shelf, was to study the flow of ice shelf water over the shelf break. This program also included surveying the shelf water plume and deployment of current meters and other instruments to monitor the ice shelf water in the future. Two additional moorings were also retreived from this area.

My job was to assist Steve Ackley in making observations and measurements of the sea ice. Ice observations involved photographing and recording the surface coverage while underway, along with ship position, meteorological data and ancillary information. We also used helicopters for visual observations and debarked the ship to take ice cores for structural information and to make snow and ice thickness measurements. We took ice cores both from first year, drifting sea ice and from ice that has been attached to the continent for many years.

The resulting data sets will be useful for analyzing sea ice processes and relating them to atmospheric and oceanic processes in the Weddell Sea, and for verifying climate models on both regional and global scales. While in the pack ice, we faxed our observational data to the National Ice Center in Washington D. C., which incorporated the information into their weekly ice maps. The ship then used these maps, which also incorporate data from many other sources, for navigational guidance. Additionally, our photographs, surface measurements and ice cores will be used as ground truth for Radarsat image interpretation, a remote sensing technique that is used in creating the ice maps.

Another, unexpected development yielded new, exciting scientific information for the polar biology community: Steve and I discovered and photographed several molting sites of Emperor penguins. The experts have suspected that the penguins go to the pack ice to molt, but it hasn't been documented until now!

A preliminary cruise report, "Sea Ice Conditions in the Weddell Sea, Jan-Feb 1998," further describes our observing techniques and findings.

The ship and its two helicopters also carried out numerous scientific, logistical and diplomatic tasks, including
aerial photographic mapping of Bird Island
transporting two biologists to Bird Island
stationing hydrographers on South Georgia Island "boat camps" to do local hydrographic studies while the ship was in the Weddell Sea
delivering mail to and from the residents of South Georgia Island
locating (by helicopter) a suitable landing site on the ice shelf for a BAS Twin Otter to deliver helicopter replacement parts, and retrieving the parts along with several bags of mail for the ship's crew
gathering bathymetric data in an area of the Weddell Sea that had never before been visited by a ship
laying a supply depot (600 fuel barrels) on the Ronne ice shelf for use next year
transporting German scientists from Neumayer Station on the Antarctic continent to the Falkland Islands and on to the UK
treating a scientist who had been injured on Bird Island, and transporting him back to the Falkland Islands
diplomatic exchanges with the Argentinian icebreaker Almirante Irizar and the German research vessel Polarstern

British Antarctic Survey, Cambridge UK ("BAS")
Keith Nicholls, Cruise Leader
Adrian Jenkins
Mark Johnson
Andy Wood
John Hall

Proudman Oceanographic Laboratory, Birkenhead UK
Mike Smithson
Geof Hargreaves

Southampton Oceanography Centre, Southampton UK
Robin Bonner
Ben Moat

Alfred-Wegener Institute, Bremerhaven Germany
Rebecca Woodgate

Earth and Space Research, Seattle WA
Laurie Padman

Cold Regions Research and Engineering Laboratory, NH
Stephen Ackley

Los Alamos National Laboratory, Los Alamos NM
Elizabeth Hunke

DERA, Farnborough, Hampshire UK
Ian Pilling

We were "Billy BAS Blokes" whether we were from BAS or not, except for Rebecca and me, who were "Betty BAS Birds."

Photography by Mark Southwell, HMS Endurance

Small bergs and sea ice
A calm evening
Adelie penguin
Emperor penguins
Leaping emporers
Sea fog and ice
The last sunset before 24-hour sunlight
Finger-rafted nilas
Iceberg mirage
Me and HMS Endurance
Cold hands (photography by Mark Southwell, HMS Endurance)