Sea Level Change and related impacts

Imagery of meandering river-like channel features up to 5 m deep and 100 m wide on the floor of Port Phillip Bay have been revealed by recent multibeam surveys. They are in water depths to 722 m below the present bay water level. This young channelling overlies older infilled Pleistocene–early Holocene channels considered to be cut by the Yarra and Werribee rivers during the last glacial or previous low stand minima 410 000 cal. yr BP and infilled during the Holocene transgression. Vibrocoring data indicate the young channels incise shelly mud. Twelve 14C shell dates in vibrocores from bay floor to 3.5 m are in two units—a lower unit range between 2880 cal. yr BP at 0.7 m to 9491 cal. yr BP at 3.5 m, and
an upper unit *0.5 to 0.7 m thick 5869 cal. yr BP forming the present bay floor. Seismic and vibrocore evidence suggests the post-869 cal. yr BP upper unit also covers the base of the young channels. This evidence implies that Port Phillip dried out to 722 m between *2800 and *1000 cal. yr BP at a time of stable present day sea-levels. The most likely cause is a sand blockage to the Port Phillip Bay channel entrances, coupled with high evaporation rates. Palynological and foraminiferal evidence suggests variable salinities occurred immediately prior to the sedimentary hiatus, with restoration of marine conditions after. The results have wide implications on Port Phillip’s water balance, salinity, pre-European climatic events and Aboriginal occupation.

This paper describes the sedimentary architecture, chronostratigraphy and palaeogeography of the late Middle and Late Pleistocene (Marine Isotope Stage / MIS 6-2) incised Rhine-valley fill in the central Netherlands based on six geological transects, luminescence dating, biostratigraphical data and a 3D geological model. The incised-valley fill consists of a ca. 50 m thick and 10-20 km wide sand-dominated succession and includes a well-developed sequence dating from the Eemian interglacial (Last Interglacial).
The lower part of the valley fill contains coarse-grained fluvio-glacial and fluvial Rhine sediments that were deposited under Late Saalian (MIS 6) cold-climatic periglacial conditions and during the transition into the warm Eemian interglacial (MIS 5e-d). This unit is overlain by fine-grained fresh-water flood-basin deposits, which are transgressed by a fine-grained estuarine unit that formed during marine high-stand. This ca. 10 m thick sequence reflects gradual drowning of the Eemian interglacial fluvial Rhine system and transformation into an estuary due to relative sea-level rise. The chronological data suggests a delay in timing of regional Eemian interglacial transgression and sea-level high-stand of several thousand years, when compared to eustatic sea-level. As a result of this glacio-isostatic controlled delay, formation of the interglacial lower delta took only place for a relative short  period of time and delta progradation was limited. During the cooler Weichselian Early Glacial period (MIS 5d-a) deposition of deltaic sediments continued and extensive westward progradation of the Rhine delta occurred.
Major parts of the Eemian and Weichselian Early Glacial deposits were eroded and buried as a result of sea-level lowering and climate cooling during the early Middle Weichselian (MIS 4-3). Near complete sedimentary preservation occurred along the margins of the incised valley  allowing the detailed reconstruction presented here.

Recent discoveries from Pakefield and Happisburgh (Britain) have provided clear evidence for an unexpectedly early hominin occupation of north-west Europe. The sites, found in the deposits of interglacial rivers and estuaries on the southern rim of the ancient North Sea coast, span the older and younger parts of the 'Cromerian Complex' Stage. The older of these sites pre-date w0.5 Ma based on the presence of a Mimomys micromammal fauna, and may be as old as 0.78e1.0 Ma. On the European continent, stone artefacts unambiguously as old derive from the Mediterranean. The earliest archaeological evidence that has been discovered inland in Europe north of the Alps is associated with an Arvicola fauna (younger than w0.5 Ma), and was deposited in temperate conditions near rivers that flowed into the North Sea. Only after the 'Cromerian Complex' is there evidence for hominin activity in cooler conditions, and also in locations east of the Rhine valley. This spatial and temporal pattern in site distribution occurs despite the long history of research in north-west Europe and the presence of deposits of the same age from both the coast and rivers. This paper explores the idea that the changes in site distribution before and after the 'Cromerian Complex' signal that early hominin occupation in northern Europe during the earlier period was an 'Atlantic' phenomenon, i.e. restricted to the milder temperate climates in the coastal continental regions. Dispersal to more inland habitats originated in the coastal regions. The conditions explaining preservation of the oldest sites from a geological perspective are investigated, providing a geographical, climatological and habitat context for the wider surroundings of the sites. Because of differences in the potential for preserving archaeology in fluvial and coastal contexts, poor long-term preservation of coastal depositional contexts and low numbers of sites, it is difficult to disentangle the influence of hominin habitat preference (or even: tolerance) from habitat preservation. However, the hypothesis that the earliest hominins in Europe were restricted to the temperate Atlantic parts of Europe provides a testable framework for evaluating future archaeological discoveries, and makes it possible to formulate research strategies for locating new hominin occupation sites in Europe, especially its Atlantic regions.

Sea Research Society's poster "Looking At The Forward Running Clocks' - Carbon Cycles and Time From Pleistocene to Present" was presented at a major international conference organised by Royal Anthropological Institute (RAI): "Anthropology, Weather and Climate Change". This international conference took place at the British Museum from 27th to 29th May 2016. RAI organised it in conjunction with the British Museum's Department for Africa, Oceania and the Americas. Sea Research Society was asked during the conference to re-formulate this poster to an article for a peer-reviewed science periodical, the online science publication "Arcadia - Explorations in Environmental History", published by Environment and Society Organisation, by its editor Katrin Kleemann. We are working to issue this poster in a periodical format in a due course.  The key points and observations of the RAI 2016 conference poster and the forthcoming paper are:

The natural carbon and methane cycles are hugely disrupted by today’s human activities. The Palaeolithic meat-hunting evolved first to a very small-scale Neolithic cattle-rearing, then to today’s mega-scale industrial farms that increase methane in the atmosphere. Meat consumption, what initially started as a globally harmless hunter-gatherer activity has evolved into today's massive, environmentally highly stressful activity as world population has grown together with the land scarcity. Thus meat consumption has today emerged as one of the most important drivers of the anthropogenic climate change due to its addition of methane to the atmosphere.

The poster presents a hypothesis where the end of Palaeolithic (Pleistocene) thawing permafrost soils and sea beds (as well as the changes in the sea bed pressurization), destabilised methane clathrates and became important and major contributor to the carbon cycle at times of lowering sea levels.  Meanwhile, the Pleistocene era's cold oceans captured carbon from the atmosphere more effectively than during the warmer Holocene. Thus it is postulated that the destabilised methane clathrates (both from on-shore and off-shore permafrost) replenished the atmospheric carbon stocks by carbon-12 and carbon-13 rich 'old' carbon isotopes (due to above sea bed depressurisation and melting-derived permafrost soil outgassing). The permafrost-released 'old carbon' thus skews the Pleistocene to Holocene Thermal Maximum eras' carbon isotope portfolio in biological samples which results in a lowered carbon-14 content within biological samples (as the plants do not differentiate between the three carbon isotopes).

The presence of permafrost-released old carbon can be detected by plant metabolistic research of the period's samples from which it could be concluded that short-term carbon-12/13 permafrost release intake (hourly and daily isotope variation in carbon synthesis [changes in temperature and prevailing wind direction]), seasonal carbon isotope variation (spring-autumn in carbon synthesis [spring-time carbon capture from the atmosphere versus later releases of old permafrost carbon once permafrost melts towards the autumn]) and multi-year carbon isotope trend (the long-term build-up of old carbon in the air mass) analyses can be carried out. These result in radiocarbon outliers, or radiocarbon-dilution, in biological and archaeological materials retrieved from Pleistocene to Holocene Thermal Maximum period.

The poster (paper) also discusses the reasons for the absence of elevated carbon dioxide and methane levels in the era's ice cores and correlates this anomaly with the present-day rapid deposition of carbon, especially methane (that has increased 4.4-times faster at 74 mb level in the atmosphere 2013-2017 that it does at ground level). This is due to cessation of the filtering effect of hydroxyl that tends to oxidise methane relatively rapidly into carbon dioxide. This filtration mechanism appears to have faltered since 2013 allowing the lighter-than-air methane to rise and accumulate in the upper troposphere and stratosphere where there is very little hydroxyl to oxidise it. When this is taken into account, a new image of 3-tier greenhouse effect emerges in the Arctic region, where methane traps Outgoing Longwave Radiation (OLR) extremely efficiently at high altitudes, carbon dioxide traps it at lower altitudes and melted snow and ice cover forces ground to absorb more sunlight at surface level. As methane appears to be accumulating in the current Arctic warming well above all glaciers, this must also have happened invisibly throughout the Pleistocene glaciations and contributed to the period's highly volatile climatic rollercoaster movements.

The poster (paper) then discusses methods and presents examples of some well-known mega radiocarbon-outliers as potential artefacts of the above proposed radiocarbon-dilution effect (which did not leave any signs of its existence in the ice cores of the past eras as methane's primary build up - in the absence of oxidising hydroxyl - occurs well above the glaciers at the very high altitudes of the upper troposphere and stratosphere). Moreover, this implies now that the Arctic might very soon and unexpectedly enter into a runaway warming state from the above-said high altitude methane accumulation which originates from melted and perforated soils and sea beds - and equally importantly from the positive feedback of the lower troposphere's hydroxyl filter failure since 2013 (as illustrated in the bar chart). The paper's major concern is less on the carbon dating effects, but rather on the possible global warming risk of a very large increase in atmosphere's carbon-12 and carbon-13 stock from methane. This release of carbon occurs initially as high-altitude methane and only later as closer-to-surface level carbon dioxide (which leaves its signal behind in the ice cores; see the temperature curve diagram of the warming occurring prior to carbon dioxide build-up in the ice cores (the red arrows) which warming trend is, thereafter often arrested and punctuated suddenly by the rapid collapses of major ice shelves and ice sheets or glacial melt water reservoir discharges, i.e. producing the cold 'Dryases' (the blue arrows). These releases will obviously skew future carbon-14 readings even further and possibly even more than our anthropogenic fossil carbon build up from the present-day use of fossil fuels.

More examples of radiocarbon-dilution effect (radiocarbon mega-outliers) will be given in the forthcoming paper. The poster invitation was presented at the conference prospectus: "RAI/BM16 - Royal Anthropological Institute, British Museum Department of Africa, Oceania and the Americas: 'Anthropology, Weather and Climate Change - British Museum, Clore Centre, 27-29 May 2016'. Conference programme and book of abstracts", published by the conference organisers Royal Anthropological Institute (RAI), The British Museum (BM) and the Wenner-Gren Foundation (WG), on a page 148.

Climate change in combination with increased anthropogenic activities will affect coastal groundwater systems throughout the world. In this paper, we focus on a coastal groundwater system that is already threatened by a relatively high seawater level: the low‐lying Dutch Delta. Nearly one third of the Netherlands lies below mean sea level, and the land surface is still subsiding up to 1 m per century. This densely populated delta region, where fresh groundwater resources are used intensively for domestic, agricultural, and industrial purposes, can serve as a laboratory case for other low-lying delta areas throughout the world. Our findings on hydrogeological effects can be scaled up since the problems the Dutch face now will very likely be the problems encountered in other delta areas in the future. We calculated the possible impacts of future sea level rise, land subsidence, changes in recharge, autonomous salinization, and the effects of two mitigation countermeasures with a three‐dimensional numerical model for variable density groundwater flow and coupled solute transport. We considered the effects on hydraulic heads, seepage fluxes, salt loads to surface waters, and changes in fresh groundwater resources as a function of time and for seven scenarios. Our numerical modeling results show that the impact of sea level rise is limited to areas within 10 km of the coastline and main rivers because the increased head in the groundwater system at the coast can easily be produced though the highly permeable Holocene confining layer. Along the southwest coast of the Netherlands, salt loads will double in some parts of the deep and large polders by the year 2100 A.D. due to sea level rise. More inland, ongoing land subsidence will cause hydraulic heads and phreatic water levels to drop, which may result in damage to dikes, infrastructure, and urban areas. In the deep polders more inland, autonomous upconing of deeper and more saline groundwater will be responsible for increasing salt loads. The future increase of salt loads will cause salinization of surface waters and shallow groundwater and put the total volumes of fresh groundwater volumes for drinking water supply, agricultural purposes, industry, and ecosystems under pressure.

The Northern Bay of Bengal (NBoB) is a globally important region for deep-sea organic matter (OM) deposition due to massive fluvial discharge from the Ganges-Brahmaputra-Meghna (G-B-M) rivers and moderate to high surface productivity. Previous studies have focused on carbon burial in turbiditic sediments of the Bengal Fan. However, little is known about the storage of carbon in pelagic and hemipelagic sediments of the Bay of Bengal over millennial time scales. This study presents a comprehensive history of OM origin and fate as well as a quan-tification of carbon sediment storage in the Eastern Bengal Slope (EBS) during the last 18 ka. Bulk organic proxies (TOC, TIC, TN, δ 13 C TOC , δ 15 N TN) and content and composition of total hydrolysable amino acids (THAA) in a sediment core (SO188-342KL) from the EBS were analyzed. Three periods of high OM accumulation were identified: the Late Glacial (LG), the Bölling/Alleröd (B/A), and the Early Holocene Climatic Optimum (EHCO). Lower eustatic sea level before 15 ka BP allowed a closer connection between the EBS and the fluvial debouch, favoring high terrestrial OM input to the core site. This connection was progressively lost between 15 and 7 ka BP as sea level rose to its present height and terrestrial OM input decreased considerably. Export and preservation of marine OM was stimulated during periods of summer monsoon intensification (B/A and EHCO) as a consequence of higher surface productivity enhanced by cyclonic-eddy nutrient pumping and fluvial nutrient delivery into the photic zone. Changes in the THAA composition indicate that the marine plankton community structure shifted from calcareous-dominated before 13 ka BP to siliceous-dominated afterwards. They also indicate that the relative proportion of marine versus terrestrial OM deposited at site 342KL was primarily driven by relative sea level and enlarged during the Holocene. The ballasting effect of lithogenic particles during periods of high coastal proximity and/or enhanced fluvial discharge promoted the export and preservation of OM. The high organic carbon accumulation rates in the EBS during the LG (18–17 ka BP) were 5-fold higher than at present and comparable to those of glacial upwelling areas. Despite the differences in sediment and OM transport and storage among the Western and Eastern sectors of the NBoB, this region remains important for global carbon sequestration during sea level low-stands. In addition, the summer monsoon was a key promotor of terrestrial and marine OM export to the deep-ocean, highlighting its relevance as regulator of the global carbon budget.

Στην παρούσα σύντομη παρουσίαση συνοψίζονται αποτελέσματα διερευνήσεων με υπολογιστικές προσομοιώσεις αναφορικά με την επίδραση της Κλιματικής Αλλαγής στην εξέλιξη της θαλάσσιας στάθμης λόγω των μετεωρολογικών παλιρροιών και επομένως και των δυνητικών παράκτιων πλημμυρών, στη Μεσόγειο και πιο ειδικά στο Αιγαίο και το Ιόνιο Πέλαγος και την ευρύτερη ελληνική παράκτια ζώνη.

Relative sea-level projections are provided for 59 locations in Canada and 10 in the adjacent mainland United States through the 21 st century, relative to [1986][1987][1988][1989][1990][1991][1992][1993][1994][1995][1996][1997][1998][1999][2000][2001][2002][2003][2004][2005]. The projections are based on the Representative Concentration Pathway (RCP) scenarios of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5). They include contributions from the thermal expansion of the ocean (steric effect), land ice melting and discharge, and anthropogenic influences. The global mean sea-level projection for RCP8.5, the largest emissions scenario, at 2100 is 74 cm (5%-95% range is 54 to 98 cm). Global Positioning System (GPS) measurements of vertical land motion are incorporated into the relative sea-level projections. In the regions presented here, vertical land motion, largely arising from glacial isostatic adjustment, plays a prominent role in determining projected relative sea-level change. On the east coast, crustal subsidence, combined with dynamic oceanographic changes, generates relative sea-level projections that are similar to or larger than the global mean projections in large parts of Atlantic Canada and New England. On the west coast, most relative sea-level projections are smaller than the global means, although some sites in Washington State and southern British Columbia feature relative sea-level projections similar to the global values. The largest variation in projected relative sea-level rise occurs in northern Canada, owing to the very large spatial differences in present-day crustal uplift due to glacial isostatic adjustment. Here, projected relative sea-level at 2100 varies from around 1 m of sea-level fall (median values) where land is rising quickly on Hudson Bay, while it reaches about 70 cm of sea-level rise on the Beaufort coast where the land is subsiding. A scenario featuring partial collapse of a portion of the West Antarctic Ice Sheet provides an additional 65 cm of sea-level rise to RCP8.5, and may be appropriate to consider when tolerance to the risk of sea-level rise is low. The relative sea-level projections given here only provide a trajectory through this century, but the IPCC AR5 projects continued global sea-level rise in coming centuries. As understanding improves of the various components of sea-level rise, it will be necessary to update, on an occasional basis, the relative sea-level projections and re-evaluate the implications for infrastructure, habitat, and marine navigation.

The importance of Pozzuoli's archaeological ruins in linking sea-level change and Earth deformation with volcanic activity has been recognized since the nineteenth century. The pillars of the Roman market were used as a paleotide gauge by pioneer geologists such as Lyell. For the first time, we have radiocarbon dated biological indicators on these remains, showing three 7 m relative sea-level highstands during the fifth century A.D., the early Middle Ages, and before the 1538 eruption of Monte Nuovo. These repeated uplift and subsidence cycles, not always followed by volcanic activity, have important implications for the evaluation of volcanic hazard.

Hydrodynamic models are commonly used for predicting water levels and currents in the deep ocean, ocean margins and shelf seas. Their accuracy is typically limited by factors, such as the complexity of the coastal geometry and bathymetry, plus the uncertainty in the flow forcing (deep ocean tide, winds and pressure). In Southeast Asian waters with its strongly hydrodynamic characteristics, the lack of detailed marine observations (bathymetry and tides) for model validation is an additional factor limiting flow representation. This paper deals with the application of ensemble Kalman filter (EnKF)-based data assimilation with the purpose of improving the deterministic model forecast. The efficacy of the EnKF is analysed via a twin experiment conducted with the 2D barotropic Singapore regional model. The results show that the applied data assimilation can improve the forecasts significantly in this complex flow regime.