774 MONTHLY WEATHER REVIEW Vol. 98, No. 10UDC .551.507.362.2:551.46.027(084.1)(269.46)(99) "1969"PICTURE OF THE MONTHGiant Icebergs in the Weddell SeaRUBEN NASA and ROLAND0 NAWRATILServicio Meteorolbyico de la Armada ArgentinaSwithinbank (1969) ment,ions t,hc drifting of txo greaticebergs, possibly tlctachetl from the Amery Barrier(73' E.) at t,he end of 1963 and seen along the Antarcticcoast bet\\-ecn 15' and 20' \Ir. in January 1968 (fig. 1).During the Argentine ?;a\-y Antarctic campaign in thesummer of 1968/1969, the icebreaker ARA General Sun,%.furtin mct with serious difficulties in furnishing suppliesto Base General Bclprano (77'5s' S., 38'48' W.) due tothe presencc of two large icebergs in Duke Ernest Bay(figs. 2 and 3). Thesc icebergs ma,y be the same HS t!hoseidentified in thc ESSA 7 picture on Feb. .7, 1969 (fig. 4),and also on Fcb. 5, 1969.hfonths later, BPT images from Nimbus 3 received at,Base Aeronrtval Rio Gallegos (51'38' S., 69'13' aT.) andAVCS photograph)- from ESSA 9 of October 1969 (fig. 5)showed a dark northcast-sonthn-est-oriented patch about,11 km wide and 80 km long in thc eastern part of DukeErnest Bay. This patch is assumed to be asmallwater leadassociated with an iceberg nearby to the north and havingsimilar dimensions-observe the hummocked appearance(A) in figure 5. This water lead with the brighter northernborder differs notably in appearance from other knownice-free waters-sec (B) in figure 5. The patch at, (A)appears clear on those days with very lit.tle or no cloudi-ness at Base General Belgrano, ruling out the hypothesist,hat these are clouds (table 1).Note in figure 5 that the iceberg in question has arelative position rotated 90" around its soutllern end,possibly aground, with respect' to the position observed infigure 4. This agrees with the obserration illust'rated infigure 2.Due to the natural erosion suffered by the afore-mentioned iceberg, its tracking has become very difficult.FIGURE 2.-Positions of two icebergs at 2000 GMT on Feb. 8, 1969,drawn aboard the icebreaker ARA General Sun Martin. Bothicebergs pivoted about point (A), thus creating a very hazardousFIGURE 1.-ESSA 3 view, orbit 6869, frame 11, of Jan. 12, 1968. approach for the ship to the base.FIQURE 3.-Panoramic view northn-ard at 1300 GMT on Feb. 6, 1969, depicting the large iceberg shown in figure 2. These high-angleoblique views were taken aboard a helicopter from the icebreaker ARA General Sun Martin in the left middle ground. The helicopter'sposition was in the vicinity of Shackleton Base at 77'56` S., 37'08' W.October 1970Ruben Nasta and Rolando Nawratil 775TABLE 1.-Cloudiness data at Base General Belgrano, including ESSA 9 views, frames 11 and 12, for October 1969Day Hour (GMT) Orbit Cloudiness at 1800 GYT(Octad 24 1644 3002 24 3 1 1839 3003 3.I 25 1743 3015 No data" 26 1841 3023 4 27 27 0. .,* 1745 3040 0 29 1548 3064 0 30 29 1743 3065 0 30 1842 3078 0 01550 30391646 3077*-FIGURE 4.-ESSA 7 view, orbit 2194, frame 11, of Feb. 7, 1969.TABLE 2.-Evidences indicating iceberg presence since October 1969 as detected from AVCS pictures from ESSA 9 Orbit Bearing Orbit BearingI312731403164337733%3577NE .-SW.3729 N.-S.37783990 NU'.-SE.4089 NNR.-SSE.41394352 NNE.-SSR'.435343624389FIGURE 6."ESSA 9 view, orbit 3002, frame 12, of Oct,. 24, 1969.since October 1969. There are certain evidences (t8ablo 2)that donote its presence.Unfortunately, sincc we do not llave any infraredinformation from 1ightJess periods of the polar regionsthat would have allowxl systematic tracking, we cannotbe absolutely certain that, thc icebcrg observed in 1968at Duke Ernest Bay is the same one that tlctacl1t.d itselfat t'he end of 1963 from the Amery Barrier.The idea suggnst,ed by Fleming (1969)-it3 might bethe SAXAE (South African Xational Antarctic Espcdition)Glacier Tongnc that sheared off in mid-1967, being p"mpsknocked off when t,ho migrating iceberg pnsscd by-mustnot be discarded. It is, hou-ever, evident that, two icebergshave been observed sincc this date.REFERENCESFleming, Michael H., Environmcntal Sciences Group, XationalEnvironmcntal Satcllitc Center, EPSA. Hillcrest Heights, Md.,1969 (personal comrnt~nication).Swithinbank, Charles, "Giant Icebergs in the Wcddcll Sen 1967/68,"Polar Record, Vol. 14, No. 91, Thc Scott Polar Research Institute,Cambridge, England, Jan. 1969, pp. 477-4'78.