93Aug PD93-07: Spring cruise 29Aug93-25Sep93 A Spring cruise originally planned to be carried out once every six years. Objectives included the following considerations: 1) ice processes - effect of ice on the ecosystem; 2) temporal variability - comparison of specific geographical locations occupied summer, fall and spring. 3) hypothesis testing- a)compare pre and post winter larval krill physiology, distribution and 'abundance' in two winters b)compare Adelie diet and condition after two winters 4) ice condition - explore whether ice west of the Antarctic Peninsula is uniform as we penetrate the ice. Work was done aboard the R/V Polar Duke PD93-7. Langdon Quetin served as chief scientist. The cruise track included sampling once per twenty kilometer grid station along transects 600, 500, 400, 300, 200. All stations were ice covered, at least to some degree. There were four diel stations(*), at 600.080, 500.080, 400.080 and 300.080. During the cruise an attempt was made to resample stations in common with the January93 and March93 cruises. Sampling West Coast of Antarctic Peninsula including near Palmer and LTER grid. At the start of the cruise near Palmer stations B to E were covered followed by the 600, 500, 400, 300 and 200 LTER grid lines. Satellite data and observations from Palmer suggest that 93 is a "light" ice year, which historically would mean that we would have maximum ice coverage in mid-Sept. There was no permanent ice in Arthur Harbor this winter and it was clear until 19 Aug when cold (-5C) and light winds caused the harbor to skim over. N wind blew ice out on 20th, but brash ice returned on 21st, and cold (-7C) and snow consolidated the ice. By the 24th the ice was solid out to the Islands. When the Polar Duke arrived on the 26th the ice thickness was 30-70 cm thick with about 10cm light snow covering. Satellite data showed the lter grid to be clear of ice on 16 Aug, save for the south-east few hundred km. By 24 August the whole lter grid was covered with ice, either advected from the south and/or newly formed. On 29 Aug the Duke transected the 600 line: from 600.040 to about 600.100 the ice was a mix of glacier ice and newly formed 70 to 100cm ice; from 600.100 to 600.200 the ice was newly formed pancake ice roughly 10 cm thick and probably not more than a week old. A satellite image on the 29th confirmed that the lter grid was still covered with ice and suggested that broken ice and open water was at least 40 to 60 km beyond our 600.200 position. The cruise track sampled along transects 600, 500, 400, 300, 200 and sea ice was encountered over the whole grid; relatively new pancake ice, 30 cm to 1m thick, sometimes with visible ice algae. Ice was densely packed in the southeast corner of the grid, the location of first year ice prior to mid-August and the Duke was more or less "stuck" for a day in the vicinity of 200.040. On return to Palmer, from 200.200, we encountered some open water along the course from 200.200 to 400.200, but mostly it was pancake ice with iceslush inbetween. On return to Palmer, 24 Sept, there was ice on the approach and in Arthur Harbor. See LTER general information. Our cruise objective was to cover grid lines 600 thru 300 and as much of the 200 line as weather and ice conditions permitted. Typically we covered two grid stations per day when weather and ice conditions permitted all activities to be carried out. Under adverse conditions, when dive operations were not possible, we covered three stations. Diel stations took a full day. 1) two station day 1-m, 2-m nets dive with 30m-transect, go-flows, krill collection sea bird collections dive with PUV under ice, water collection, krill BOPS with water for biol, chem, nuts transit to next station with sea bird census and acoustics enroute xbt at 10km point between stations BOPS with water for biol, chem, nuts dive with PUV under ice, water, krill sea bird collections dive with transect, go-flows, krill sea bird census/acoustics 1-m, 2-m nets CTD casts during overnight transit to next station 2) diel stations BOPS every 3 hours for 12 hours with water for biol, chem, nuts dives, acoustics, bird collections, between BOPS casts underice light, krill sampling/observation The original sampling plan was to sample two 10/10 ice stations corresponding to LTER grid locations 20km apart and 5 stations minimum seaward of the ice stations along the transect with 20km spacing. In general we planned to proceed into the pack ice during darkness to the first LTER grid station with 10/10 pack ice. Completing this ice station 1 during daylight, we could move to another 20km into the pack ice during darkness to ice station 2. Penguin surveys and collections at night during transit maximize chances the penguins are on the ice. We could complete ice station 2 in one day then proceed 20km past ice station 1 to begin sampling the 5 stations seaward of ice station 1 on a 20km spacing. At the end of the open stations we would be be roughly 100km from 10/10 pack ice so could proceed to the ice edge of the next transect line, approximately 140km and proceed to ice station 1 in time to arrive at first daylight. During the open stations we would try to ensure that at least 3 of 5 stations are sampled in daylight. The work is at a time of minimal light change with latitude in the LTER grid. Night movements in pack ice were important to maximize chances of capturing penguins. There was much previous krill activity and more assurance of ice from 200 to 00 so the 200 transect line was incorportated in the sprint sampling strategy. Each transect was to contain approximately 3 open water and 2 ice stations until it was found that the majority of stations were ice covered. Core measurments available two years after the cruise. Citation acknowledgement: "Data from the Palmer LTER data archive were supported by Office of Polar Programs, NSF (OPP-9011927)." NSF funded Icecolors93 NSF funded krill energetics antarctic, southern ocean, bio-optics, phytoplankton, krill, marginal ice zone ~lter/data/93aug/* Christian JR and DM Karl, 1993. Palmer LTER: Bacterial exoprotease activity in the Antarctic Peninsula during Austral Autumn 1993. Antarctic Journal of the United States 28(5):331-222. Klinck JM, DA Smith, RC Smith, 1995: Hydrography in the LTER region during August and September, 1993. Antarctic Journal of the United States. Klinck JM, RC Smith: Oceanographic data collected aboard RV Polar Duke August-September. CCPO Technical Report No. 94-01, Crittenton Hall, Old Dominion Univer- sity, Norfolk, VA 023529. 1994. SIO Reference No. 94-08. Quetin LB, RM Ross, RC Smith, KS Baker, 1995: Palmer LTER: Winter cruise August/September 1993 (PD93-7). Antarc- tic Journal of the United States. Sullivan, B, HA Matlick, BB Prezelin, 1994. Palmer LTER: Patterns of distribution of Inorganiz Macronutrients, Phytoplankton Pigmentation, and Photosynthetic Activity in a Ice-Dominated Ecosystem in Austral Winter. Antarctic Journal of the United States 29(5):207-211. National Science Foundation, Division of Polar Programs 23Sep93 24Sep93-rcs 19Nov93-ksb 26Apr96-ksb 25Nov96-ksb Langdon Quetin Raymond Smith Langdon Quetin, UCSB, langdon@crseo.ucsb.edu Robin Ross, UCSB, robin@crseo.ucsb.edu

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