Tracing winter temperatures over the last two millennia using a north-east Atlantic coastal record

We present 2500 years of reconstructed bottom water temperatures (BWT) using a fjord sediment archive from the north-east Atlantic region. The BWT represent winter conditions due to the fjord hydrography and the associated timing and frequency of bottom water renewals. The study is based on a ca. 8&thinsp;m long sediment core from Gullmar Fjord (Sweden), which was dated by 210Pb and AMS 14C and analysed for stable oxygen isotopes (δ18O) measured on shallow infaunal benthic foraminiferal species Cassidulina laevigata d'Orbigny 1826. The BWT, calculated using the palaeotemperature equation from McCorkle et al. (1997), range between 2.7 and 7.8&thinsp;°C and are within the annual temperature variability that has been instrumentally recorded in the deep fjord basin since the 1890s. The record demonstrates a warming during the Roman Warm Period ( ∼ 350&thinsp;BCE–450&thinsp;CE), variable BWT during the Dark Ages ( ∼ 450–850&thinsp;CE), positive BWT anomalies during the Viking Age/Medieval Climate Anomaly ( ∼ 850–1350&thinsp;CE) and a long-term cooling with distinct multidecadal variability during the Little Ice Age ( ∼ 1350–1850&thinsp;CE). The fjord BWT record also picks up the contemporary warming of the 20th century (presented here until 1996), which does not stand out in the 2500-year perspective and is of the same magnitude as the Roman Warm Period and the Medieval Climate Anomaly.</p

Anthropogenic and climatic impacts on a coastal environment in the Baltic Sea over the last 1000 years

Coastal environments have experienced large ecological changes as a result of human activities over the last 100-200 years. To understand the severity and potential consequences of such changes, paleoenvironmental records provide important contextual information. The Baltic Sea coastal zone is naturally a vulnerable system and subject to significant human-induced impacts. To put the recent environmental degradation in the Baltic coastal zone into a long-term perspective, and to assess the natural and anthropogenic drivers of environmental change, we present sedimentary records covering the last 1000 years obtained from a coastal inlet (Gasfjarden) and a nearby lake (Lake Storsjon) in Sweden. We investigate the links between a pollen-based land cover reconstruction from Lake Storsjon and paleoenvironmental variables from Gasfjarden itself, including diatom assemblages, organic carbon (C) and nitrogen (N) contents, stable C and N isotopic ratios, and biogenic silica contents. The Lake Storsjon record shows that regional land use was characterized by small-scale agricultural activity between 900 and 1400 CE, which slightly intensified between 1400 and 1800 CE. Substantial expansion of cropland was observed between 1800 and 1950 CE, before afforestation between 1950 and 2010 CE. From the Gasfjarden record, prior to 1800 CE, relatively minor changes in the diatom and geochemical proxies were found. The onset of cultural eutrophication in Gasfjarden can be traced to the 1800s and intensified land use is identified as the main driver. Anthropogenic activities in the 20th century have caused unprecedented ecosystem changes in the coastal inlet, as reflected in the diatom composition and geochemical proxies. (c) 2018 Elsevier Ltd. All rights reserved.Peer reviewe

On the Convergence of Kergin and Hakopian Interpolants at Leja Sequences for the Disk

We prove that Kergin interpolation polynomials and Hakopian interpolation polynomials at the points of a Leja sequence for the unit disk $D$ of a sufficiently smooth function $f$ in a neighbourhood of $D$ converge uniformly to $f$ on $D$. Moreover, when $f$ is $C^\infty$ on $D$, all the derivatives of the interpolation polynomials converge uniformly to the corresponding derivatives of $f$

Data descriptor: a global multiproxy database for temperature reconstructions of the Common Era

Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850-2014. Global temperature composites show a remarkable degree of coherence between high-and low-resolution archives, with broadly similar patterns across archive types, terrestrial versus marine locations, and screening criteria. The database is suited to investigations of global and regional temperature variability over the Common Era, and is shared in the Linked Paleo Data (LiPD) format, including serializations in Matlab, R and Python. (TABLE) Since the pioneering work of D'Arrigo and Jacoby1-3, as well as Mann et al. 4,5, temperature reconstructions of the Common Era have become a key component of climate assessments6-9. Such reconstructions depend strongly on the composition of the underlying network of climate proxies10, and it is therefore critical for the climate community to have access to a community-vetted, quality-controlled database of temperature-sensitive records stored in a self-describing format. The Past Global Changes (PAGES) 2k consortium, a self-organized, international group of experts, recently assembled such a database, and used it to reconstruct surface temperature over continental-scale regions11 (hereafter, ` PAGES2k-2013'). This data descriptor presents version 2.0.0 of the PAGES2k proxy temperature database (Data Citation 1). It augments the PAGES2k-2013 collection of terrestrial records with marine records assembled by the Ocean2k working group at centennial12 and annual13 time scales. In addition to these previously published data compilations, this version includes substantially more records, extensive new metadata, and validation. Furthermore, the selection criteria for records included in this version are applied more uniformly and transparently across regions, resulting in a more cohesive data product. This data descriptor describes the contents of the database, the criteria for inclusion, and quantifies the relation of each record with instrumental temperature. In addition, the paleotemperature time series are summarized as composites to highlight the most salient decadal-to centennial-scale behaviour of the dataset and check mutual consistency between paleoclimate archives. We provide extensive Matlab code to probe the database-processing, filtering and aggregating it in various ways to investigate temperature variability over the Common Era. The unique approach to data stewardship and code-sharing employed here is designed to enable an unprecedented scale of investigation of the temperature history of the Common Era, by the scientific community and citizen-scientists alike

The Little Ice Age: evidence from a sediment record in Gullmar Fjord, Swedish west coast

We discuss the climatic and environmental changes during the last millennium in NE Europe based on a ca. 8-m long high-resolved and well-dated marine sediment record from the deepest basin of Gullmar Fjord (SW Sweden). According to the ²¹⁰Pb- and ¹⁴C-datings, the record includes the period of the late Holocene characterised by anomalously cold summers and well-known as the Little Ice Age (LIA). Using benthic foraminiferal stratigraphy, lithology, bulk sediment geochemistry and stable carbon isotopes we reconstruct various phases of the cold period, identify its timing in the study area and discuss the land–sea interactions occurring during that time. The onset of the LIA is indicated by an increase in cold-water foraminiferal species <i>Adercotryma glomerata</i> at ~ 1350 AD The first phase of the LIA was characterised by a stormy climate and higher productivity, which is indicated by a foraminiferal unit of <i>Nonionella iridea</i> and <i>Cassidulina laevigata</i>. Maximum abundances of <i>N. iridea</i> probably mirror a short and abrupt warming event at ~ 1600 AD. It is likely that due to land use changes in the second part of the LIA there was an increased input of terrestrial organic matter to the fjord, which is indicated by lighter &delta;¹³C values and an increase of detritivorous and omnivorous species such as <i>Textularia earlandi</i> and <i>Eggerelloides scaber</i>. The climate deterioration during the climax of the LIA (1675–1704 AD), as suggested by the increase of agglutinated species, presence of <i>Hyalinea balthica</i>, and a decline of <i>N. iridea</i> may have driven the decline in primary productivity during this time period

Large spatial variations in coastal C-14 reservoir age a case study from the Baltic Sea

Coastal locations are highly influenced by input from freshwater river runoff, including sources of terrestrial carbon, which can be expected to modify the C-14 reservoir age, or R(t), associated with marine water. In this Baltic Sea case study, pre-bomb museum collection mollusc shells of known calendar age, from 30 locations across a strategic salinity transect of the Baltic Sea, were analysed for C-14, delta C-13 and delta O-18. R (t) was calculated for all 30 locations. Seven locations, of which six are within close proximity of the coast, were found to have relatively higher R(t) values, indicative of hard-water effects. Whenever possible, the Macoma genus of mollusc was selected from the museum collections, in order to exclude species specific reservoir age effects as much as possible. When the Macoma samples are exclusively considered, and samples from hard-water locations excluded, a statistically significant correlation between Macoma R(t) and average salinity is found, indicating a two end-member linear mixing model between (14)Cmarine and C-14(runoff). A map of Baltic Sea Macoma aragonite R(t) for the late 19th and early 20th centuries is produced. Such a map can provide an estimate for contemporary Baltic Sea Macoma R(t), although one must exercise caution when applying such estimates back in time or to C-14 dates obtained from different sample material. A statistically significant correlation is found between delta O-18(aragonite) and Macoma R(t), suggesting that delta O-18(aragonite) can be used to estimate Macoma palaeo-R (t), due to the delta O-18(aragonite) signal being dominated by the salinity gradient of the Baltic Sea. A slightly increased correlation can be expected when delta O-18(aragonite) is corrected for temperature fractionation effects. The results of this Baltic Sea case study, which show that R(t) is affected by hydrographic conditions and local carbon inputs, have important consequences for other coastal and estuarine locations, where R(t) is also likely to significantly vary on spatial and temporal bases

Large spatial variations in coastal C-14 reservoir age a case study from the Baltic Sea

Coastal locations are highly influenced by input from freshwater river runoff, including sources of terrestrial carbon, which can be expected to modify the C-14 reservoir age, or R(t), associated with marine water. In this Baltic Sea case study, pre-bomb museum collection mollusc shells of known calendar age, from 30 locations across a strategic salinity transect of the Baltic Sea, were analysed for C-14, delta C-13 and delta O-18. R (t) was calculated for all 30 locations. Seven locations, of which six are within close proximity of the coast, were found to have relatively higher R(t) values, indicative of hard-water effects. Whenever possible, the Macoma genus of mollusc was selected from the museum collections, in order to exclude species specific reservoir age effects as much as possible. When the Macoma samples are exclusively considered, and samples from hard-water locations excluded, a statistically significant correlation between Macoma R(t) and average salinity is found, indicating a two end-member linear mixing model between (14)Cmarine and C-14(runoff). A map of Baltic Sea Macoma aragonite R(t) for the late 19th and early 20th centuries is produced. Such a map can provide an estimate for contemporary Baltic Sea Macoma R(t), although one must exercise caution when applying such estimates back in time or to C-14 dates obtained from different sample material. A statistically significant correlation is found between delta O-18(aragonite) and Macoma R(t), suggesting that delta O-18(aragonite) can be used to estimate Macoma palaeo-R (t), due to the delta O-18(aragonite) signal being dominated by the salinity gradient of the Baltic Sea. A slightly increased correlation can be expected when delta O-18(aragonite) is corrected for temperature fractionation effects. The results of this Baltic Sea case study, which show that R(t) is affected by hydrographic conditions and local carbon inputs, have important consequences for other coastal and estuarine locations, where R(t) is also likely to significantly vary on spatial and temporal bases

The Little Ice Age: evidence from a sediment record in Gullmar Fjord, Swedish west coast

"El parque del Bicentenario se encuentra situado en una zona con gran potencial cultural y turístico, actualmente existen planes de saneamiento de el Lago de Valsequillo así como la realización de proyectos que a futuro esta se convertiría en una zona altamente rentable y que cuenta con criterios y objetivos de sustentabilidad, el diseño, la construcción, operación y mantenimiento de un parque urbano que promueva un desarrollo sustentable. es por ello que con el propósito de combatir, prevenir y aportar a la problemática de saqueo y robo de piezas prehispánicas y arte sacro en la zona de Valsequillo, el tema que se plantea en esta tesis es un "Museo Local en el Parque Bicentenario".

Long-term coastal openness variation and its impact on sediment grain-size distribution: a case study from the Baltic Sea

We analysed the long-term variations in grain-size distribution in sediments from Gåsfjärden, a fjord-like inlet in the southwestern Baltic Sea, and explored potential drivers of the recorded changes in the sediment grain-size data. Over the last 5.4 thousand years (ky) in the study region, the relative sea level decreased 17 m, which was caused by isostatic land uplift. As a consequence, Gåsfjärden was transformed from an open coastal setting to a semi-closed inlet surrounded by numerous small islands on the seaward side. To quantitatively estimate the morphological changes in Gåsfjärden over the investigated time period and to further link the changes to the grain-size distribution data, a digital elevation model (DEM)-based openness index was calculated. The largest values of the openness indices were found between 5.4 and 4.4 cal ka BP, which indicates relatively high bottom water energy. During the same period, the highest sand content (∼  0.4 %) and silt / clay ratio ( ∼  0.3) in the sediment sequence were also recorded. After 4.4 cal ka BP, the average sand content was halved to ∼  0.2 % and the silt / clay ratio showed a significant decreasing trend over the last 4 ky. These changes were found to be associated with the gradual embayment of Gåsfjärden, as represented by the openness indices. The silt&thinsp; /&thinsp; clay ratios exhibited a delayed and relatively slower change compared with the sand content, which indicates different grain-size sediment responses to the changes in hydrodynamic energy. Our DEM-based coastal openness indices have proved to be a useful tool for interpreting the temporal dynamics of sedimentary grain size