QUALITY ASSESSMENT OF SEA LEVEL DATA by the UH SEA LEVEL CENTER/NATIONAL OCEANOGRAPHIC DATA CENTER JOINT ARCHIVE FOR SEA LEVEL updated: 22 Aug 2019 Station : Rothera Latitude: 67 34.0S Country : United Kingdom Longitude: 068 08.0W JASL # : 832A Time Meridian: 060W (GMT-4 hr) GLOSS # : 342 TOGA #: none NODC #: 56067801 Contributor : National Oceanography Centre Proudman Oceanographic Laboratory 6 Brownlow Street Liverpool L69 3GP United Kingdom Originator : same Original Data: digital Instrmnt Type: Digiquartz pressure sensor and barometer Digitzd Intvl: 15 minutes Present Data : Hourly, daily, and monthly values obtained by: Hourly : 01 Dec 2009 - 08 Dec 2011 (rot4.sl original file) data received with data +/- 7.5 minutes from the hour thus the filter was an average of values on either side of the hour. Other spans: spot sample on hour. Daily : 119-point convolution filter (Bloomfield, 1976) centered on noon applied to the hourly data with respective periods of the 95, 50, and 5% amplitude points at 124.0, 60.2, and 40.2 hours Monthly: Simple average of all daily values; calculated if 7 or fewer days are missing Span of data : 23 Dec 2002 - 06 Sep 2018 Gaps > 1 mon : 14 Jul 2003 - 19 Aug 2003;16 Feb 2004 - 26 Apr 2004 19 Apr 2005 - 15 Dec 2006;02 Aug 2017 - 10 Nov 2017 Time Refernce: GMT (00-23 hours) Space-filler Flag :-9999 Units : millimeters Missing Data Flag : 9999 Existing : Yes Operational : Yes Sat. Trans. : unconfirmed Distribution : 2002-2018 Refernce Levl: Precise datum control using technique described by Woodworth et al., 1994. Heights are relative to the "ROTHERA B-DATUM DECEMBER 2002". Comment : This station is part of Phase 2 of the ACCLAIM project. The ACCLAIM (Antarctic Circumpolar Current Levels by Altimetry and Island Measurements) programme in the South Atlantic and Southern Oceans consists of measurements from coastal tide gauges and bottom pressure stations, together with an ongoing research programme in satellite altimetry. ACCLAIM is the Proudman Oceanographic Laboratory's main contribution to WOCE (and, in particular, to WOCE Core 2) and one of its objectives is the study of variations of the Antarctic Circumpolar Current. ACCLAIM is managed within the Global Sea Level Change (GSLC) group at POL led by Dr.J.M.Vassie. The history of the development of ACCLAIM is described in the report by Spencer et al. (1993): Spencer, R., Foden, P.R., McGarry, C., Harrison, A.J., Vassie, J.M., Baker, T.F., Smithson, M.J., Harangozo, S.A. and Woodworth, P.L. 1993. The ACCLAIM programme in the South Atlantic and Southern Oceans. International Hydrographic Review, 70, 7-21. In that report it will be seen that, in Phase 1 of ACCLAIM from 1983, measurements at coastal tide gauge sites took the form of sub-surface pressure (SSP) measurements (units of pressure e.g. mbar) rather than sea level (units of length e.g. centimetres). SSP is here defined as the total, measured pressure recorded by a sub-surface pressure transducer, a measurement which includes the pressure load from the atmosphere as well as from the water column. It is absolutely essential that any user of ACCLAIM data realises which data type (either SSP or sea level) is being analysed. From around early 1993, the gauges at many of the sites were replaced by Phase 2 ACCLAIM 'B gauges' which record SSP, air pressure and sea level as described in: Woodworth, P.L., Vassie, J.M., Spencer, R. and Smith, D.E. 1994. Precise datum control for pressure tide gauges. To be published in Marine Geodesy. The Phase 1 coastal SSP data were acquired in different ways (e.g. with a diver-replaced Aanderaa pressure gauge at Ascension, or with a Digiquartz in the sea sensor at St.Helena, see Spencer et al. 1993 for details) and with different pressure integration periods (e.g. quarter hour, half hour, one hour). For WOCE Centre purposes the original data have generally been filtered to give one hour sampling. However, common to all records is an uncertainty connected with potential offset biases and drifts in the pressure sensors. At some sites (e.g. St.Helena) extensive tide pole data are also available and biases and long term drifts in the sensor data may eventually be rectified (this is under study at present). However, the drifts in general mean that in most cases the records should not be used, without further careful attention in particular studies, for the study of timescales seasonal or longer. The Phase 2 coastal sea level data have precise datum control (see Woodworth et al. 1994 for details) and can certainly be used for long term studies. These data have also been contributed to the Permanent Service for Mean Sea Level (PSMSL) and Global Sea Level Observing System (GLOSS). Some of the Phase 1 data and all the Phase 2 coastal data will also contain ancillary information on air pressures and sea temperatures from ACCLAIM sensors. Several of these records contain large gaps. However, the GSLC group at POL has collected extensive sets of such ancillary data from meteorological agencies for its own analysis purposes, and should be able to provide further advice. SSP measurements at deep ocean bottom pressure stations (together with inverted echo sounder and temperature measurements) have also been a feature of ACCLAIM. Measurements at Amsterdam and Kerguelen in the Indian Ocean are described in: Vassie, J.M., Harrison, A.J., Woodworth, P.L., Harangozo, S.A., Smithson, M.J. and Thompson, S.R. 1994. On the temporal variability of the transport between Amsterdam and Kerguelen Islands. Journal of Geophysical Research, 99(C1), 937-949. while most recording is now concentrated in the Scotia Sea - Drake Passage area of the Southern Ocean as part of WOCE Core 2. Tidal constituents from these recorders have been contributed to the IAPSO Pelagic Constants data base maintained by the PSMSL at Bidston on behalf of IAPSO. For the JASL update Mar 2019, data were downloaded: https://www.ntslf.org/files/acclaimdata/phase2/ See notes in the Inventory link. This series represents the real or in situ sea level signal, as opposed to sub-surface pressure gauges without venting or atmospheric pressure compensation which measure the absolute pressure (water plus air column). CI MISSING REPLACED GAPS QUESTIONABLE YEAR (%) DATA OR BAD DATA FLUCTUATIONS ---- --- -------------------- --------------- -------------------- 2002 2 none none none 2003 86 97-98,195-231, none 286-300 2004 81 47-117 none none 2005 28 75-80,109-365 (19)094-(13)095 none 2006 5 1-349 none none 2007 96 354-365 (23)346-(19)347 none 2008 78 1-77,352-356 (00)078-(07)078 none (07)083-(14)083 2009 94 21-41,334-366 none none 2010 98 288-297 none none 2011 100 none (00)342-(18)342 none 2012 99 12-13 none 63-347 2013 100 none none none 2014 100 none (11)169-(02)170 none (15)194-(23)194 (09)195-(22)195 (09)209-(20)209 (12)226-(19)226 (17)235-(03)236 2015 89 107-108,110-116,136- (20)053-(14)054 none 149,215-220,222-223, (21)084-(09)085 232-240,245-247, (03)104-(14)104 362-365 (02)132-(12)132 (21)149-(12)150 (01)151-(12)151 (01)152-(12)152 (03)153-(11)153 (02)154-(11)154 (03)156-(10)156 (04)157-(11)157 (05)158-(13)158 (22)162-(12)163 (23)163-(10)164 (23)164-(10)165 (22)175-(05)176 (12)182-(22)182 (17)202-(04)203 (12)205-(00)206 (11)209-(18)209 (11)211-(18)211 (12)212-(19)212 (13)213-(22)213 (13)214-(01)215 (17)247-(07)248 (06)274-(13)274 (09)301-(17)301 2016 97 105-112,253-258 (14)013-(03)014 none (05)076-(12)076 (05)117-(12)117 (23)136-(07)137 (03)147-(17)147 (12)220-(04)221 (06)247-(15)247 (08)258-(15)258 (10)275-(20)275 (01)276-(14)276 (03)336-(12)336 2017 70 81-83,201-202,214- (14)004-(22)004 none 314,319-321,332-336 (13)005-(20)005 (09)154-(18)154 (22)204-(15)205 2018 67 15-16,26-28 (15)043-(13)044 none (07)154-(15)154 (13)201-(00)202 (14)208-(06)209 (15)230-(22)230