@article {5620, title = {Paraglacial coasts responses to glacier retreat and associated shifts in river floodplains over decadal timescales (1966-2016), Kongsfjorden, Svalbard}, journal = {Land Degradation and Development}, year = {2018}, abstract = {

The aim of this paper is to quantify and map the impact of the post-LIA climate change on the coastal evolution on three glacier catchments in the Kongsfjorden area in Svalbard. Climatic data of the meteorological station of Ny-{\r A}lesund indicate an increase in the annual mean air temperature of +4{\textdegree}C from 1969 to 2016 and an increase in precipitation. On the northern coast of the Br{\o}gger Peninsula, the Austre Lov{\'e}nbreen, Midtre Lov{\'e}nbreen and Vestre Lov{\'e}nbreen glaciers have experienced a net retreat in response to changing meteorological conditions. As a consequence of this retreat, the glaciers have disclosed a large area of 7 km{\texttwosuperior} composed of terrigenous sediments which is reworked by runoff and forms coastal sandur deltas. Channel network behavior has been studied using the computation of the active floodplain width by photo-interpretation, which decreased in average from 1966 to 2010. This demonstrated a contraction of the active braided belt and a decrease in the amount of braided channels. A photo-interpretation analysis combined with acquisition of dGPS data during field work shows a mean shoreline progradation of + 0.16 m/y from 1966 to 2016, with a maximal advance of + 82 m seaward. Since 1966 coastal progradation has decreased in time with higher mean values at the beginning of the studied period and an erosional trend from 1990. The sublittoral area was studied using analog side scan sonar in 2009, 2011 and 2012. Three pro-deltas were identified and underwent an extension of 30,000 m{\texttwosuperior} from 2009 to 2012. In the light of this knowledge, our main conclusion is that, by retreating, glaciers have an impact on the sediment availability and on the capacity of the fluvial system to effectively transport sediment to the shoreline. These two factors control the overall coastal evolution by regulating the sediment supply to the coastal area. The coastal zones that were fed with sediments by runoff have experienced a coastal progradation and those that lost this supply have undergone a coastal recession. Due to the contraction of proglacial floodplains, current progradation concerns restricted coastal areas.

}, doi = {10.1002/ldr.3149}, author = {Marine Bourriquen and Agn{\`e}s Baltzer and Denis Mercier and J{\'e}r{\^o}me Fournier and St{\'e}phane Costa and Erwan Roussel} } @article {5027, title = {Space-time evolution of a large field of pockmarks in the Bay of Concarneau (NW Brittany)}, journal = {Bulletin de la Soci{\'e}t{\'e} G{\'e}ologique de France}, year = {2017}, abstract = {

About a decade ago, a large field of pockmarks, covering an overall area of 36 km2 was discovered in water depths of \<30m in the central part of the Bay of Concarneau (Southern Brittany, France). This field, composed of features from 5m to 35m in diameter and \<1m in depth, is characterized by unusual high densities of pockmarks, up to 5840 per square kilometre. Geophysical data correlated with sedimentary samples acquired in 2005 and 2009 show that pockmarks and their immediate surroundings are associated with dense tubes benches cover, built by a filter-feeding amphipod: Haploops nirae, forming original benthic communities. Two complementary surveys were carried out in April 2011 (Pock and Ploops) and April 2014 (Pock and Tide), on the Oceanographic Vedette (O/V) Haliotis (Ifremer/Genavir), to map the limit of the pockmarks and Haploops fields with the maximum accuracy. The link between the presence of the Haploops nirae communities and the occurrence of pockmarks /gas was then established and the proposed hypothesis was that tidal cycles may provide a good candidate for a short-term (monthly) triggering mechanism of fluid expulsion (Baltzer A, Ehrohold A, Rigolet C, Souron A, Cordier C, Clouet H. 2014. Geophysical exploration of an active pockmark field in the Bay of Concarneau, southern Brittany, and implications for resident suspension feeders. Geo-Marine Letters, 34, 215{\textendash}230). Due to the high-level precision (50 cm) of the positioning system (Magellan Aquarius Ixsea Hydrins) coupled with the RTK attitude system, these new bathymetric and imagery maps together with the sub-bottom Chirp profiles, allow us to compare the data sets from April 2011 and April 2014. The superimposition of the two data sets shows that the distribution of the pockmarks remains similar between these 2 dates (i.e. for 3 years), for the group of large, widely scattered pockmarks, which are deeply rooted in the Holocene palaeo-valley infills and for the group of pockmarks identified as the trawl-scour pockmarks, initiated by trawling action. Most of the pockmarks present very recent shapes without any infilling but sonar imagery reveals that some of them have been covered by a thin muddy layer, thereby reflecting, at least, a temporary cessation of expulsion or a different activity. Chirp profiles indicate some acoustic flares above the pockmarks, revealing gas/fluid expulsion. Different gas clues within the sedimentary column, such as acoustic turbidity, enhanced gas reflectors (EGR), chimneys pipes, occur at exactly the same places on the chirp seismic profiles from 2011 and 2014. Therefore, contrary to most examples described in the\  literature, this pockmarks field is still active.

}, doi = {10.1051/bsgf/2017191}, author = {Agn{\`e}s Baltzer and Marine Reynaud and Axel Ehrhold and J{\'e}r{\^o}me Fournier and C{\'e}line Cordier and H{\'e}l{\`e}ne Clouet} } @article {4265, title = {Coastal evolution and sedimentary mobility of Br{\o}gger Peninsula, northwest Spitsbergen}, journal = {Polar Biology}, year = {2016}, month = {03/2016}, pages = {1-10}, abstract = {

Since the end of the Little Ice Age (LIA), Svalbard glaciers have undergone a net retreat in response to changing meteorological conditions. Located between 76{\textdegree}N and 80{\textdegree}N, western Spitsbergen has seen a climatic transition from a glacial to a paraglacial system. On the northern shore of the Br{\o}gger Peninsula (northwest Spitsbergen), the average temperature increased by 3\ {\textdegree}C between 1965 and 2015, and cold-based valley glaciers have retreated more than 1\ km from their LIA limits. This rapid deglaciation has exposed large areas of glacigenic sediments being easily reworked by runoff. This has led to the formation of extensive glacier-river delta systems and coastal progradation. Post-LIA coastal progradation and formation of new landforms in Kongsfjorden have been controlled predominantly by substantial availability of glacial sediment. A combination of aerial photographic and field data has been employed to estimate the post-LIA evolution of coastal sandur deltas and their submarine parts (named here {\textquotedblleft}prodeltas{\textquotedblright}). The data set reveals that delta shoreline advance could have reached around 5\ m/year. between 1966 and 1990 for the most energetic delta of Austre Lovenbreen, and around 4\ m/year between 2011 and 2014 for the most energetic delta of Midtre Lovenbreen. The prodeltas registered a net growth from 2009 to 2012: the biggest, located in the prolongation of deltas of Austre Lovenbreen, measured 1033\ m in length in 2009 and 1180\ m in length in 2012. This substantial amount of sediment supplied in the fjord has an impact on the fjord ecology, especially on the benthic ecosystem.

}, keywords = {High Arctic, Paraglacial, Sedimentary flux, Submarine and aerial coastal evolution, Svalbard}, doi = {10.1007/s00300-016-1930-1}, author = {Marine Bourriquen and Agn{\`e}s Baltzer and Denis Mercier and J{\'e}r{\^o}me Fournier and Laurent Perez and Sylvain Haquin and Eric Bernard and Maria Ansine Jensen} } @inbook {3555, title = {The "Turritella Layer": a potential proxy of a drastic Holocene environmental change on the North-East Atlantic coast}, booktitle = {Sediment Fluxex in Coastal Areas}, year = {2015}, pages = {3-21}, publisher = {Springer Science}, organization = {Springer Science}, edition = {Coastal Research Library}, address = {Dordrecht}, author = {Agn{\`e}s Baltzer and Zohra Mokeddem and Evelyne Goubert and Franck Lartaud and Nathalie Labourdette and J{\'e}r{\^o}me Fournier and Jean-Fran{\c c}ois Bourillet} }