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Hanna Silvennoinen, Elena Kozlovskaya, Eduard Kissling. (2016). POLENET/LAPNET teleseismic P wave travel time tomography model of the upper mantle beneath northern Fennoscandia (Vol. 7).
Abstract: Abstract. The Polenet/lapnet (Polar Earth Observing Network) Broadband Seismic Network Was Deployed In Northern Fennoscandia (Finland, Sweden, Norway, And Russia) During The Third International Polar Year 2007–2009. The Array Consisted Of Roughly 60 Seismic Stations. In Our Study, We Estimate The 3-d Architecture Of The Upper Mantle Beneath The Northern Fennoscandian Shield Using High-resolution Teleseismic P Wave Tomography. The P Wave Tomography Method Can Complement Previous Studies In The Area By Efficiently Mapping Lateral Velocity Variations In The Mantle. For This Purpose 111 Clearly Recorded Teleseismic Events Were Selected And The Data From The Stations Hand-picked And Analysed. Our Study Reveals A Highly Heterogeneous Lithospheric Mantle Beneath The Northern Fennoscandian Shield Though Without Any Large High P Wave Velocity Area That May Indicate The Presence Of Thick Depleted Lithospheric “Keel”. The Most Significant Feature Seen In The Velocity Model Is A Large Elongated Negative Velocity Anomaly (Up To −3.5 %) In Depth Range 100–150 Km In The Central Part Of Our Study Area That Can Be Followed Down To A Depth Of 200 Km In Some Local Areas. This Low-velocity Area Separates Three High-velocity Regions Corresponding To The Cratonic Units Forming The Area.
Programme: 1201
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Olga Usoltseva, Elena Kozlovskaya. (2016). Studying local earthquakes in the area Baltic-Bothnia Megashear using the data of the POLENET/LAPNET temporary array (Vol. 7).
Abstract: Earthquakes in areas within continental plates are still not completely understood, and progress on understanding intraplate seismicity is slow due to a short history of instrumental seismology and sparse regional seismic networks in seismically non-active areas. However, knowledge about position and depth of seismogenic structures in such areas is necessary in order to estimate seismic hazard for such critical facilities such as nuclear power plants and nuclear waste deposits. In the present paper we address the problem of seismicity in the intraplate area of northern Fennoscandia using the information on local events recorded by the POLENET/LAPNET (Polar Earth Observing Network) temporary seismic array during the International Polar Year 2007–2009. We relocate the seismic events using the program HYPOELLIPS (a computer program for determining local earthquake hypocentral parameters) and grid search method. We use the first arrivals of P waves of local events in order to calculate a 3-D tomographic P wave velocity model of the uppermost crust (down to 20 km) for a selected region inside the study area and show that the velocity heterogeneities in the upper crust correlate well with known tectonic units. We compare the position of the velocity heterogeneities with the seismogenic structures delineated by epicentres of relocated events and demonstrate that these structures generally do not correlate with the crustal units formed as a result of crustal evolution in the Archaean and Palaeoproterozoic. On the contrary, they correlate well with the postglacial faults located in the area of the Baltic-Bothnia Megashear (BBMS). Hypocentres of local events have depths down to 30 km. We also obtain the focal mechanism of a selected event with good data quality. The focal mechanism is of oblique type with strike-slip prevailing. Our results demonstrate that the Baltic-Bothnia Megashear is an important large-scale, reactivated tectonic structure that has to be taken into account when estimating seismic hazard in northern Fennoscandia.
Programme: 1021
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J. Plomerová, L. Vecsey, V. Babuška, LAPNET Working Group. (2011). Domains of Archean mantle lithosphere deciphered by seismic anisotropy – inferences from the LAPNET array in northern Fennoscandia (Vol. 2).
Abstract: An international LAPNET array (2007–2009, http://www.oulu.fi/sgo-oty/lapnet) of the POLENET/LAPNET sub-project of the POLENET-IPY consortium, related to seismic and geodetic studies in the Arctic regions, consisted of about 60 broadband seismic stations located on the territory of northern Finland and adjacent parts of Sweden, Norway and Russia. We analyze relative P-wave travel-time deviations evaluated for a subset of 90 teleseismic events recorded by the LAPNET array and show examples of lateral variations of shear-wave splitting to demonstrate variability of fabrics of the Archean mantle lithosphere. The initial results clearly demonstrate the Archean mantle lithosphere consists of domains with consistent fabrics reflecting fossil anisotropic structures. 3-D self-consistent anisotropic models with inclined symmetry axes accommodate two independent sets of body-wave anisotropic observations. Individual domains are delimited by boundaries (sutures), where the anisotropic parameters change. The results obtained from the LAPNET array fill a gap in structural studies of the upper mantle beneath northern Fennoscandia.
Programme: 1021
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Williams G D, Hindell M, Houssais M-N, Tamura T, Field I C, . (2011). Upper ocean stratification and sea ice growth rates during the summer-fall transition, as revealed by Elephant seal foraging in the Adélie Depression, East Antarctica
. 1812-0784, 7(2), 185–202.
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Philip L. Woodworth. (2019). The global distribution of the M1 ocean tide (Vol. 15).
Abstract: The worldwide distribution of the small degree-3 M1 ocean tide is investigated using a quasi-global data set of over 800 tide gauge records and a global tide model. M1 is confirmed to have a geographical variation in the Atlantic consistent with the suggestion of Platzman (1984b) and Cartwright (1975) that M1 is generated in the ocean as a consequence of the spatial and temporal overlap of M1 in the tidal potential and one (or at least a small number of) diurnal ocean normal mode(s). As a consequence, it is particularly strong around the UK and on North Sea coasts (amplitudes ∼10 mm). This analysis shows that their suggestion is also consistent to a great extent with the observed small amplitudes in the Pacific and Indian oceans. However, there are differences at the regional and local level which require much further study via more sophisticated ocean tidal modelling. By contrast, what is called the M1' tide (a combination of several degree-2 lines in the tidal potential with frequencies close to that of M1) is shown to have a geographical distribution consistent with expectations from other degree-2 diurnal tides, apart from locations such as around the UK where tidal interactions introduce complications. As far as I know, this is the first time that these small tidal constituents have been mapped on a global basis and, in particular, the first time that the ocean response to the degree-3 component of the tidal potential has been investigated globally.
Programme: 688
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Biermann L, Guinet C, Bester M, Brierley A, Boehme L, . (2015). An alternative method for correcting fluorescence quenching. Ocean Sci., 11(1), 83–91.
Abstract: Under high light intensity, phytoplankton protect their photosystems from bleaching through non-photochemical quenching processes. The consequence of this is suppression of fluorescence emission, which must be corrected when measuring in situ yield with fluorometers. We present data from the Southern Ocean, collected over five austral summers by 19 southern elephant seals tagged with fluorometers. Conventionally, fluorescence data collected during the day (quenched) were corrected using the limit of the mixed layer, assuming that phytoplankton are uniformly mixed from the surface to this depth. However, distinct deep fluorescence maxima were measured in approximately 30% of the night (unquenched) data. To account for the evidence that chlorophyll is not uniformly mixed in the upper layer, we propose correcting from the limit of the euphotic zone, defined as the depth at which photosynthetically available radiation is ~ 1% of the surface value. Mixed layer depth exceeded euphotic depth over 80% of the time. Under these conditions, quenching was corrected from the depth of the remotely derived euphotic zone Zeu, and compared with fluorescence corrected from the depth of the density-derived mixed layer. Deep fluorescence maxima were evident in only 10% of the day data when correcting from mixed layer depth. This was doubled to 21% when correcting from Zeu, more closely matching the unquenched (night) data. Furthermore, correcting from Zeu served to conserve non-uniform chlorophyll features found between the 1% light level and mixed layer depth.
Programme: 109
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Jean Roger, Bernard Pelletier, Maxime Duphil, Jérôme Lefèvre, Jérôme Aucan, Pierre Lebellegard, Bruce Thomas, Céline Bachelier, David Varillon. (2021). The Mw 7.5 Tadine (Maré, Loyalty Is.) earthquake and related tsunami of December 5, 2018: implications for tsunami hazard assessment in New Caledonia.
Abstract: On The 5th Of December 2018, A Magnitude Mw 7.5 Earthquake Occurred Southeast Of Maré, An Island Of The Loyalty Archipelago, New Caledonia. This Earthquake Is Located At The Junction Between The Plunging Loyalty Ridge And The Southernmost Vanuatu Arc, In A Tectonically Very Active Area Regularly Subjected To Strong Seismic Crises And Events Higher Than Magnitude 7 And Up To 8. Widely Felt In New Caledonia It Has Been Immediately Followed By A Tsunami Warning, Confirmed Shortly After By A First Wave Arrival At The Loyalty Islands Tide Gauges (Maré And Lifou), Then Along The East Coast Of Grande Terre Of New Caledonia And In Several Islands Of The Vanuatu Archipelago. Seafloor Initial Deformation Linked To Tsunami Generation Has Been Modeled With Most Numerical Code Using Earthquake Parameters Available From Seismic Observatories. Then The Wave Propagation Has Been Modeled Using Schism, Another Modelling Code Solving The Shallow Water Equations On An Unstructured Grid Based On A New Regional Dem Of ~180 M Resolution And Allowing Refinement In Many Critical Areas. Finally, The Results Have Been Compared To Tide Gauge Records, Field Observations And Testimonials From 2018. The Arrival Times, Wave Amplitude And Polarities Present Good Similarities, Especially In Far-field Locations (Hienghène, Port-vila And Poindimié). Maximum Wave Heights And Energy Maps For Two Different Scenarios Highlight The Fact That The Orientation Of The Source (Strike Of The Rupture) Played An Important Role, Focusing The Maximum Energy Path Of The Tsunami South Of Grande-terre And The Isle Of Pines. However, Both Scenarios Indicate Similar Propagation Toward Aneityum, Vanuatu Southernmost Island, The Bathymetry Acting Like A Waveguide. This Study Has A Significant Implication In Tsunami Hazard Mitigation In New Caledonia As It Helps To Validate The Modelling Code And Process Used To Prepare A Scenarios Database For Warning And Coastal Evacuation.
Programme: 133
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Pierre Stephan, Lancelot Massé, David Dider, Ronan Autret, Antoine Soloy, Serge Suanez. (2022). Pluri-annual morphological and sedimentological changes of the Valahnúkur boulder barrier, SW Iceland.
Abstract: While recent studies highlighted the great mobility of boulder beaches related to the impact of storm waves, numerous researches are still needed to better understand the morphodynamic of coastal boulder accumulations. This paper provides original data about pluri-annual morphological and sedimentological changes, as well as storm-induced geomorphic processes and their impact on the Valahnúkur boulder barrier, in the south-west of Iceland. First described by Etienne & Paris (2010), this massive accumulation of boulders shows numerous evidences of coastal barrier flooding and intense boulder mobility. Between May 2015 and May 2021, a topo-morphological survey was undertaken to analyze and quantify both cross-shore and longshore morphosedimentary processes of the Valahnúkur boulder barrier and surrounding areas. Annual campaigns of UAV (Unmanned Aerial Vehicle) flights were conducted in order to produce a set of Digital Elevation Models (DEMs) and Orthophotographs using Structure-from-Motion photogrammetry. DEMs were compared to deduce the morphological changes. Orthophotographs were analyzed from a deep learning-based method to estimate the changes in the spatial distribution of boulder sizes. Hydrodynamic conditions were reconstructed using wave buoy and tide gauge measurements. Wave runup were calibrated from the analysis of a wave/swash motion data set acquired by video monitoring related to different hydrodynamic conditions. The chronology of extreme water levels has been reconstructed on this high refective beach to estimate the elevation of the wave action during the survey period. From the sediment budget calculation, a significant northward longshore drift of around 1000 m3/a is highlighted on the beachface. The ridge and back-barrier areas were dominated by accretion related to cross-shore boulder transport from the beach. The volume of transported boulders is highly variable according to hydrodynamic conditions. Although the morphogenic impact of winter storms is difficult to assess, the observed morphological changes suggest processes dominated by swash, overtopping and overwash. The boulder size analysis highlights a link between the boulders mass and their movement landward. Video monitoring indicates that the amplitude of the swash is quite similar whether the hydrodynamic conditions are normal or energetic. The high porosity of the barrier appears to be a key factor in the dissipation of wave energy.
Programme: 1216
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Locatelli R, Bousquet P, Hourdin F, Saunois M, Cozic A, Couvreux F, Grandpeix J-Y, Lefebvre M-P, Rio C, Bergamaschi P, Chambers S D, Karstens U, Kazan V, van der Laan S, Meijer H A J, Moncrieff J, Ramonet M, Scheeren H A, Schlosser C, Schmidt M, Vermeulen A, Williams A G, . (2015). Atmospheric transport and chemistry of trace gases in LMDz5B: evaluation and implications for inverse modelling
. Geosci. Model Dev., 8(2), 129–150.
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O'Connor, F.M., C.E. Johnson, O. Morgenstern, N.L. Abraham, P. Braesicke, M. Dalvi, G.A. Folberth, M.G. Sanderson, P.J. Telford, A. Voulgarakis, P.J. Young, G. Zeng, W.J. Collins, and J.A. Pyle. (2014). Evaluation of the new UKCA climate-composition model – Part 2: The Troposphere. GMD, 7, 41–91.
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