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See detailVertical Land Movements and Sea Level Changes on South Georgia, South Atlantic Ocean: Results from 7 Years of Geodetic and Oceanographic Observations on a Remote Island
Teferle, Felix Norman UL; Hunegnaw, Addisu UL; Hibbert, Angela et al

Scientific Conference (2020, December 16)

South Georgia Island in the South Atlantic Ocean, is a small remote land mass that supports various ground-based instrumental observations (Global Navigation Satellite System (GNSS), tide gauge ... [more ▼]

South Georgia Island in the South Atlantic Ocean, is a small remote land mass that supports various ground-based instrumental observations (Global Navigation Satellite System (GNSS), tide gauge, meteorological and seismic) in an otherwise largely under sampled oceanic region. Moreover, the South Atlantic Ocean plays an important role in global ocean circulation, con-necting the deep thermohaline circulation of the North Atlantic and Indian Oceans, whilst also linking to the Antarctic Circumpolar Current in the South, where the lack of continental barriers allows a free exchange of water between the major ocean basins. Hence, South Georgia po-tentially lies within a region susceptible to climatic changes before these can be felt further afield. In 2013 and 2014 a total of five GNSS stations were installed covering the area of the main island (approximately 170 x 50 km) with two of those being located close to the King Edward Point (KEP) Research Station and the GLOSS tide gauge (ID 187). Furthermore, precise levelling campaigns in 2013, 2014, 2017 and 2020 supported the analysis of local ground instabilities near the tide gauge. Through these activities the tide gauge datum within the Permanent Ser-vice for Mean Sea Level (PSMSL) has been established, which in turn, makes the derived KEP mean sea level (MSL) record highly valuable for long-term studies and satellite altimetry cali-brations. In this study, we will present the vertical land movement estimates from seven years of GNSS observations, five precise levelling campaigns, and will discuss their impact on the sea level record from the KEP tide gauge and nearby satellite altimetry sea surface heights. Our results confirm uplift all over South Georgia Island while the area at KEP and particularly the jetty with tide gauge are subsiding relative to the rest of the island. Using this information we correct the MSL record for the vertical land movements and investigate its signals together with those from nearby satellite altimetry tracks. [less ▲]

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See detailConsolidating Observation of Land and Sea Level Changes around South Georgia Island
Teferle, Felix Norman UL; Hunegnaw, Addisu UL; Hibbert, Angela et al

Poster (2019, December 13)

With its mid-ocean location in the Southern Atlantic Ocean South Georgia Island is in a key position for the oceanic and geodetic global monitoring networks. Since 2013 the tide gauge at King Edward Point ... [more ▼]

With its mid-ocean location in the Southern Atlantic Ocean South Georgia Island is in a key position for the oceanic and geodetic global monitoring networks. Since 2013 the tide gauge at King Edward Point (KEP) with GLOSS ID 187 has been monitored using a GNSS station nearby on Brown Mountain. By accurately geo-referencing the tide gauge and monitoring any vertical land movements, a continuous record of its datum within the Permanent Service for Mean Sea Level (PSMSL) can be established, which in turn makes the recorded and averaged sea levels useful for long-term studies and satellite altimetry calibrations. In 2014 another GNSS station was installed at KEP after local subsidence was sus-pected and later on three additional GNSS stations came to service at the periphery of the main island, making it possible to monitor uplift/subsidence wider afield. Further-more, together with four precise levelling campaigns of the KEP benchmark network in 2013, 2014 and two in 2017, it has also been possible to investigate the very local character of the vertical motions near KEP, i.e. the stability of the jetty upon which the tide gauge is mounted. In this study, we will present the results from the GNSS and precise levelling meas-urements, and will discuss their impact on the sea level record from the KEP tide gauge and nearby satellite altimetry sea surface heights. This study comes at a timely manner as during the Austral Summer 2019/2020 the jetty will be stabilized and en-larged, and consequently the current tide gauge will be replaced by a new one. Our measurements show that uplift is observed all over South Georgia Island while the ar-ea at KEP and particularly the jetty with tide gauge are subsiding relative to the rest of the island. In contrast, results for the tide gauge record show a lower magnitude of ob-served sea level rise than expected from nearby satellite altimetry. We will revisit all geodetic and oceanic observations in an attempt to improve the agreement between these measurements to summarize the status before the work at the jetty begins. [less ▲]

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