Rapid Sea-level Rise Research Articles

The Heuksan mud belt on the tide-dominated shelf of Korea: a supply-driven depositional system?

A 20–50-km-wide, approx. 200-km-long and 50-m-thick mud deposit around Heuksan Island, southwest Korea, extends from the mouth of the Geum River to the shelf off Jeju Island. The deposit formed in association with postglacial sea-level rise. However, the substantial thickness and rapid seaward progradation of the deposit over a period of only about 3–4 thousand years, as postulated by previous investigators, are difficult to reconcile with the rapid sea-level rise during the early to mid-Holocene. To resolve this discrepancy, the origin and stratigraphic evolution of the Heuksan mud belt were reexamined using high-resolution seismic profiles and three drill cores penetrating down to the basement. A sedimentary facies analysis with AMS 14C age control facilitated reconstruction of the postglacial evolution of the deposit. The seismic profiles reveal that the Heuksan mud deposit can be divided into three depositional events clearly defined by distinct spatiotemporal bounding surfaces. The lower unit contains retrograding tidal flat sequences formed during an earlier transgression commencing at ca.16.0 ka and terminating at 11.6 ka. The middle unit consists of rapidly prograding mud clinoforms deposited from 11–6.5 ka. This unit extends 80 km onto the distal shelf, and is characterized by sedimentation rates of 5.0 cm/year. From 6.5–6 ka, progradation was interrupted for a 500 year period during which the deposit retreated by 35 km due to a decrease in the sedimentation rate to 0.18 cm/year. The abrupt stratigraphic break was evidently triggered by a sudden change in sediment supply, resulting in rapid retreat of the unit despite continuing local sea-level rise. Renewed sedimentation commenced at about 6.0 ka, being initially characterized by clinoform progradation, followed by autoretreat from about 2.5 ka onward due to a decreasing sediment supply. The Heuksan mud belt may thus represent an example of a shelf depositional system driven predominantly by the rate of sediment supply, rather than by sea-level rise.

Late Quaternary relative sea level in Southern California and Monterey Bay

Few records of late Quaternary relative sea level (RSL) are available for the Pacific coast of North America south of San Francisco Bay, a region where RSL data would be particularly useful for constraining vertical rates of tectonic motion. This paper provides the first regional, uplift-corrected late Quaternary RSL history for southern California derived from a compilation of 132 previously published and unpublished radiocarbon ages from nearshore, estuarine, and freshwater deposits in sediment cores from coastal southern California. We also provide a local, uplift-corrected RSL history for Monterey Bay, central California, generated from 48 radiocarbon ages from Elkhorn Slough and surrounding environments. Our resulting compilations show rapid sea-level rise from 15 ka which begins to decelerate to present mean sea level (PMSL) between 6 and 8 ka. Late Holocene (<4 ka) sea-level rise averaged 0.8 ± 0.3 mm a−1 in southern California and 1.3 ± 0.19 mm a−1 along Monterey Bay in central California. Both rates of late Holocene RSL rise calculated are lower than recent RSL rates from southern California (∼1.61 ± 0.34 to 2.4 ± 1.04 mm a−1) and Monterey Bay (1.49 ± 0.95 mm a−1), derived from uplift-corrected, 20th century tide gauge data. This new RSL data fills geographical gaps in relative sea-level histories, as well as provides important datums for local tectonic processes.

Estimation and Projection of Non-Linear Relative Sea-Level Rise in the Seto Inland Sea, Japan

ABSTRACTFuture sea-level rise (SLR) in and around the Seto Inland Sea (SIS), Japan, is estimated in 2050 and 2100 using ensemble empirical mode decomposition (EEMD) and long-term sea-level records. Ensemble empirical mode decomposition, an adaptive data analysis method, can separate sea-level records into intrinsic mode functions (IMFs) from high to low frequencies and a residual. The residual is considered a non-linear trend in the sea-level records. The mean SLR trend at Tokuyama in the SIS from EEMD is 3.00 mm y−1 from 1993 to 2010, which is slightly lower than the recent altimetry-based global rate of 3.3 ± 0.4 mm y−1 during the same period. Uncertainty in SLR is estimated by considering interdecadal variations in the sea levels. The resulting SLR in 2050 and 2100 for Tokuyama is 0.19 ± 0.06 m and 0.56 ± 0.18 m, respectively. The stations along the coast of the Pacific Ocean display a greater and more rapid SLR in 2100 compared with other stations in the SIS. The SLR is caused not only by mass and volume changes in the sea water but also by other factors, such as local subsidence, tectonic motion, and river discharge. The non-linear trend of SLR, which is the residual from EEMD, is interpreted as the sum of the local factors that contribute to the sea-level budget.

Geochemical and palynological sea-level proxies in hemipelagic sediments: A critical assessment from the Upper Cretaceous of the Czech Republic

Geochemical and palynological records are presented for an expanded Turonian–Coniacian hemipelagic succession in the central Bohemian Cretaceous Basin. A high-resolution stratigraphic framework is provided by biostratigraphy and organic carbon stable-isotope (δ13Corg) chemostratigraphy. A short-term (100 kyr) sea-level curve has been derived from high-resolution transgressive/regressive maxima / shore-proximity data established from basin-wide sediment geometries. The viability of geochemical and palynological parameters as potential sea-level proxies is tested against this independently derived sea-level record. Elemental chemostratigraphy is demonstrated to offer a reliable means of identifying medium- to long-term (0.4–2.4 Myr) sea-level trends. Manganese maxima are associated with periods of high sea level, and troughs with intervals of low sea level. Falling Mn contents accompany regression and rising values transgression. Major transgressive events associated with medium-term sea-level change are marked by sharp increases in Ti/Al ratios, but short-term (100 kyr) sea-level cycles are not consistently identified. Long-term δ13Corg variation and dinoflagellate cyst species richness are positively correlated and show similarities to the sea-level curve. Baseline trends have a cycle duration close to the 2.4 Myr long-eccentricity cycle. Dinocyst species richness closely follows short-term changes in sea level, with marked increases in dinocyst diversity coincident with most short-term flooding events. Periods of rapid sea-level rise caused an influx of a more diverse ‘outer shelf’ assemblage into the study area, together with the addition of shallower water species, some of which may have been transported into the central basin by hypopycnal flows. Changes in the proportion and abundance of peridinioid dinoflagellate cysts (principally Palaeohystrichophora infusorioides) were controlled principally by changing nutrient levels. Proximity proxies derived from geochemical and palynological data are not always consistent with the independent sea-level model. This exemplifies the need to understand all factors influencing elemental geochemical and palynological proxies before making simplistic sea level interpretations.

Bipolar seesaw control on last interglacial sea level.

Our current understanding of ocean-atmosphere-cryosphere interactions at ice-age terminations relies largely on assessments of the most recent (last) glacial-interglacial transition, Termination I (T-I). But the extent to which T-I is representative of previous terminations remains unclear. Testing the consistency of termination processes requires comparison of time series of critical climate parameters with detailed absolute and relative age control. However, such age control has been lacking for even the penultimate glacial termination (T-II), which culminated in a sea-level highstand during the last interglacial period that was several metres above present. Here we show that Heinrich Stadial 11 (HS11), a prominent North Atlantic cold episode, occurred between 135 ± 1 and 130 ± 2 thousand years ago and was linked with rapid sea-level rise during T-II. Our conclusions are based on new and existing data for T-II and the last interglacial that we collate onto a single, radiometrically constrained chronology. The HS11 cold episode punctuated T-II and coincided directly with a major deglacial meltwater pulse, which predominantly entered the North Atlantic Ocean and accounted for about 70 per cent of the glacial-interglacial sea-level rise. We conclude that, possibly in response to stronger insolation and CO2 forcing earlier in T-II, the relationship between climate and ice-volume changes differed fundamentally from that of T-I. In T-I, the major sea-level rise clearly post-dates Heinrich Stadial 1. We also find that HS11 coincided with sustained Antarctic warming, probably through a bipolar seesaw temperature response, and propose that this heat gain at high southern latitudes promoted Antarctic ice-sheet melting that fuelled the last interglacial sea-level peak.

A 12,000-yr pollen record off Cape Hatteras — Pollen sources and mechanisms of pollen dispersion

Abstract Integrating both marine and terrestrial signals from the same sediment core is one of the primary challenges for understanding the role of ocean–atmosphere coupling throughout past climate changes. It is therefore vital to understand how the pollen signal of a given marine record reflects the vegetation changes of the neighboring continent. The comparison between the pollen record of marine core JPC32 (KNR178JPC32) and available terrestrial pollen sequences from eastern North America over the last 12,170 years indicates that the pollen signature off Cape Hatteras gives an integrated image of the regional vegetation encompassing the Pee Dee river, Chesapeake and Delaware hydrographic basins and is reliable in reconstructing the past climate of the adjacent continent. Extremely high quantities of pollen grains included in the marine sediments off Cape Hatteras were transferred from the continent to the sea, at intervals 10,100–8800 cal yr BP, 8300–7500 cal yr BP, 5800–4300 cal yr BP and 2100–730 cal yr BP, during storm events favored by episodes of rapid sea-level rise in the eastern coast of US. In contrast, pollen grains export was reduced during 12,170–10,150 cal yr BP and 4200–2200 cal yr BP, during episodes of intense continental dryness and slow sea level rise episodes or lowstands in the eastern coast of US. The near absence of reworked pollen grains in core JPC32 contrasts with the high quantity of reworked material in nearby but deeper located marine sites, suggesting that the JPC32 record was not affected by the Deep Western Boundary Current (DWBC) since the end of the Younger Dryas and should be considered a key site for studying past climate changes in the western North Atlantic.

Climate science: timing is everything during deglaciations.

Links between various climate records for the North Atlantic Ocean and the Mediterranean Sea have helped to identify a potential mechanism that enhanced sea-level rise during the last interglacial time interval. See Letter p.197 A central goal of palaeoclimate research is that of deciphering the mechanisms responsible for major state shifts in the Earth system, such as between glacial and interglacial conditions. This has proven difficult enough even for the last glacial termination (T-I), much less termination II (T-II), which ended glacial conditions about 130,000 years ago. Gianluca Marino et al. use new and existing data to demonstrate a link, within uncertainties, between Heinrich Stadial 11 (HS11) — a prominent Northern Hemisphere cold event — and the timing of peak sea level rise during T-II. A strong Southern Hemisphere warming also occurred during HS11, consistent with the idea of a bipolar seesaw that would probably have promoted Antarctic ice sheet melting. In contrast, rapid sea level rise in T-1 clearly postdated Heinrich Stadial 1. Possibly in response to differing CO2 and insolation conditions during T-I and T-II, fundamentally different mechanisms seem to be at work in triggering glacial terminations.

Evidence for sea level and monsoonally driven variations in terrigenous input to the northern East China Sea during the last 24.3 ka

AbstractGeochemical and sedimentological analyses of core PC‐1 recovered from the northern East China Sea (ECS) provide insights into variations in terrigenous input associated with sea level and climate changes over the past 24.3 ka. Based on high‐resolution multiproxy records, our results suggest that the competing processes of sea level and monsoonally driven precipitation determined terrigenous input to the northern ECS. Dominance of terrigenous material, along with relatively light Globigerinoides ruber δ18O, indicates that the Last Glacial Maximum (LGM) lowstand of sea level has occurred during the period 21.5–19.6 ka, not suggesting an early slow rise but supporting the conventional LGM age of 21 ka. This LGM lowstand was terminated by the rapid sea level rise of 19 ka meltwater pulse (MWP), which is well expressed by the nearly synchronous decreases in both terrigenous detritus and mean grain size from 19.6 to 18.9 ka. MWP‐1A is clearly marked in our records by a sharp reduction in terrigenous input and pronounced maxima of G. ruber δ18O at 15.3–14.8 ka, given the considerable age uncertainties of deglacial marine radiocarbon samples. A slightly increasing input of terrigenous matter is noted after 13.4 ka, potentially pointing to a sea level fall following the Inter‐Allerød Cooling Period, which was seldom reported previously. Although MWP‐1B did not leave robust signatures in terrigenous input, it is explicitly captured by the heavy δ18O of G. ruber and decline in mean grain size at 11.5–10.9 ka. MWP‐1c probably occurred in a broad millennial interval with multiple peaks, which are robustly marked by the abrupt variations in terrigenous input and marine organic matter at 9.7–9.3 and 9.1 ka, respectively. During the late Holocene, the effect of continuously weakening monsoon precipitation overwhelmed that of stable sea level resulting in a uniform increase in the proportion of marine‐derived organic matter after 5.5 ka.

Sr–Nd isotopic constraints on detrital sediment provenance and paleoenvironmental change in the northern Okinawa Trough during the late Quaternary

For this study, elemental and Sr-Nd isotopic compositions of AMS C-14 age-dated core sediments from the northern Okinawa Trough were investigated to reconstruct sediment provenance and transport processes over the last 22.3 ka and further to trace the forcing mechanisms behind the provenance changes. The results clearly showed that large compositional variations of these elements and isotopes occur in deposition, suggesting three-phases of changes in sediment source: paleo-Huanghe (Unit 3, 223-14.8 ka), East China Sea shelf-derived (Unit 2, 14.8-7.3 ka), and Taiwan-derived detritus stages (Unit 1, <7.3 ka). Such provenance changes since the last glacial maximum may be closely correlated to sea-level fluctuation, the evolution of Tsushima Warm Current, as well as East Asian monsoonal climatic variation. At 22.3-14.8 ka, the paleo-Huanghe mouth was situated close to the study area, thus dominating sedimentation therein, especially during stronger winter monsoon periods. At the beginning of Unit 2 (14.8-12.8 ka), rapid sea-level rise and significant retreat of the river mouth overwhelmed enhanced continental weathering, leading to less detrital sediment supply from the paleo-Huanghe to the study area. Subsequently, the East China Sea shelf-derived matter dominated detrital deposition therein from 12.8 to 73 ka. Since 73 ka, the fully evolved Tsushima Warm Current has transported some detrital particles from Taiwan to the study area, especially during the strengthening period at 7.3-5.1 ka. A prominent decline in Taiwan-sourced matter supply at 5.1-2.8 ka may have been caused by suppression of the Tsushima Warm Current, possibly associated with the Pulleniatina minimum event. (C) 2015 Elsevier B.V. All rights reserved.

Palaeoecology, taphonomy, and preservation of a lower Pliocene shell bed (coquina) from a volcanic oceanic island (Santa Maria Island, Azores)

Abstract Massive fossil shell accumulations require particular conditions to be formed and may provide valuable insights into the sedimentary environments favouring such concentrations. Shallow-water shell beds appear to be particularly rare on reefless volcanic oceanic islands on account of narrow, steep and highly-energetic insular shelves where the potential for preservation is limited. The occurrence of an exceptional coquina (Pedra-que-pica) within the Miocene–Pliocene deposits of Santa Maria Island (Azores), therefore provides a rare opportunity to understand the conditions that led to the formation and preservation of a massive shell bed at mid-ocean insular setting. This study provides a detailed analysis regarding a 10–11-m-thick bivalve-dominated fossil assemblage exposed at Pedra-que-pica on Santa Maria Island in the Azores. Integration of taphonomical, palaeoecological and sedimentological observations are used to reconstruct the genesis of the coquina bed and related events, and to discuss why such exceptional sedimentary bodies are so rare on shelves around reefless volcanic oceanic islands. The sequence at Pedra-que-pica demonstrates a complex succession of sedimentary environments in response to the drowning of an existing coastline during a period of rapid sea-level rise. The Pedra-que-pica shell bed incorporates storm-related materials and possible debris falls that originated nearby in a shallow and highly productive carbonate factory. Deposition took place below fair-weather wave base, at around 50 m depth, as inferred from the overlying volcanic succession. The preservation of this coquina was favoured by deposition on a platform laterally protected by a rocky spur, combined with rapid burial by water-settled volcanic tuffs and subsequent volcanic effusive sequences. The recent exhumation of the deposit is the result of island uplift and subsequent erosion.

Reappraisal of sea-level lowstand during the Last Glacial Maximum observed in the Bonaparte Gulf sediments, northwestern Australia

During the Last Glacial Maximum (LGM), ice volume reached a relative maximum and global temperature was lower than today. Understanding continental ice volume change requires accurate reconstruction of relative sea level, but tectonic uplift and isostatic adjustment effects complicate many records. Using marine sediment cores from the Bonaparte Gulf in northwestern Australia, a so-called “far field” tectonically stable site, Yokoyama et al. (2000) reported that the LGM terminated abruptly at 19 ka with a rapid sea-level rise (19 ka event). Their sea-level reconstruction determined the age of the LGM termination, but the timing of its inception remained less well constrained, partly because the number of radiocarbon analyses was insufficient to clarify LGM duration. Here we return to the Bonaparte Gulf and present a new relative sea level that better constrains LGM duration with high-resolution radiocarbon dating of a recently recovered marine sediment core (water depth: 120 m, length: 583 cm). Radiocarbon dating of 23 molluscs and 26 bulk organic-matter samples, together with total organic carbon, total nitrogen, and stable carbon isotopes, provide a record of paleoenvironmental variability in response to sea level change. Our results indicate that the LGM sea-level minimum occurred at 20.8 cal ka BP and the LGM duration was shorter than previously reported.

Sea-level rise since 8.2ka recorded in the sediments of the Potengi–Jundiai Estuary, NE Brasil

Abstract We present the first data set on the evolution and Holocene infilling of the Potengi River Estuary at the NE Brazilian Continental Margin near the city of Natal. The study is based on integrated sedimentological, geochemical and palaeontological information from 6 boreholes drilled in the area of estuarine mangroves, complemented by radiocarbon dating of the in situ remains of mangrove vegetation. Four samples taken close to the pre-inundation substratum set the baseline of reference points for the sea-level reconstruction. This palaeoenvironmental reconstruction, coupled with a 14 C age model, complements previous sea-level studies along the Rio Grande do Norte coast, which have been based primarily on beach-rocks and other on-shore exposed sedimentary materials. A rapid sea-level rise, at an averaged rate of approximately 6.1 mm/yr − 1 , occurred between 8300 and 7000 cal. yr BP. Since then, the pace of relative sea-level rise slowed and non-eustatic factors, namely terrigenous sediment supply and coastal dynamics, became dominant in the evolution of the estuary. The post-transgression period witnessed the decline of mangroves, whose remnants were identified mostly in the initial 2 m of Holocene estuarine sediments. Accelerated sea-level rise, combined with geomorphological confinement of the studied intertidal zone, was probably responsible for the demise of halophyte vegetation, which thrived again in the late Holocene.

Late Quaternary sedimentary environmental evolution offshore of the Hangzhou Bay, East China—implications for sea level change and formation of Changjiang alongshore current

This study focuses on sedimentary environmental changes offshore of Hangzhou Bay, East China, since the Late Quaternary. AMS C-14 ages from core CJK10, lithologies, distribution of foraminifera, heavy minerals, and S and Cl elements show a fluvial terrace environment during similar to 23.2-11.0 cal ka BP; a littoral to tidal-flat environment during 11.0-10.2 cal ka BP; and a shallow marine environment with a relatively low sedimentation rate (0.1-0.22 cm/a) since 4.3 cal ka BP. High depositional rates (similar to 1.6 cm/a) from 10.9 to 10.2 cal ka BP resulted from sufficient accommodation space created by rapid sea level rise from -44 m to -33 m, from high sediment delivery by local rivers, and effective trapping of sediments by tidal-flat vegetation. The rate of sea level rise was variable; relatively high from 10.9 to 10.6 cal ka BP (2.1 cm/a), and lower since 10.6 cal ka BP (1.2 cm/a). The Changjiang alongshore current crossed the Hangzhou Bay to form the mud wedge on the inner shelf of the East China Sea later than 9.4 cal ka BP. The CJK10 site was a tide-dominated shelf environment and experienced erosion from approximately 9.4-9.2 cal ka BP to 4.3 cal ka BP. The depositional hiatus was caused by the Changjiang alongshore current, which was relatively weak during 9.4-7.5 cal ka BP and increased in strength during similar to 7.5-4 cal ka BP. From similar to 4.3 cal ka BP, a large amount of sediment from the Changjiang River was partly deposited on the continental shelf of Hangzhou Bay with some transported southward. Therefore, this study clarifies the history of Changjiang-derived sediment dispersal and deposition, although a detailed record of the changes in the Changjiang alongshore current since 4.3 cal ka BP is difficult to obtain because of the scarcity of evidence.

Chapter 17 Sedimentation in the Papaghni Group of rocks in the Papaghni sub-basin of the Proterozoic Cuddapah Basin, India

Abstract The Gulcheru Quartzite (30–200 m thick) overlies Archaean basement rocks, and comprises an impersistent conglomerate at the base of more widespread quartzites, with shale and ferruginous interbeds. The overlying Vempalle Formation (≤1500 m) comprises mainly stromatolitic carbonates, lesser cherts and mudrocks. Together, these two units make up the Palaeoproterozoic Papaghni Group, which displays an arcuate outcrop belt in the SW Cuddapah Basin, bearing no obvious relationship to the tectonic grain in the basement lithologies. Facies defined in the Gulcheru Quartzite are ascribed to initial alluvial fans, which transitioned into a shallow-marine coastline and shelf, as transgression occurred under overall thermal subsidence, possibly related to post-plume thermal relaxation. The shallow siliciclastic Gulcheru shelf is inferred to have evolved to a stromatolitic ramp that accommodated deposition of the Vempalle chemical sediments. The abrupt vertical transition from clastic to carbonate deposits is ascribed to rapid sea-level rise. Late-stage shoreline progradation during uppermost Vempalle times and concomitant clastic inflows terminated the carbonate factory.

The Global Impacts of Extreme Sea-Level Rise: A Comprehensive Economic Assessment

This paper investigates the world-wide economic cost of rapid sea-level rise of the kind that could be caused by accelerated ice flow from the West Antarctic and/or the Greenland ice sheets. Such an event would have direct impacts on economic activities located near the coastline and indirect impacts further inland. Using data from the DIVA model on sea floods, river floods, land loss, salinisation and forced migration, we analyse the effects of these damages in a computable general equilibrium model for 25 world regions. We consider three sea-level rise scenarios that correspond to 0.47, 1.12 and 1.75 m by the 2080s. By incorporating a wider range of damage categories, implemented in an economy-wide framework and including very rapid sea-level rise, the study offers a new contribution to climate change impact studies. We find that the loss of GDP worldwide is 0.5 % in the highest sea-level rise scenario, with a loss of welfare (equivalent variation) of almost 2 % world-wide. Within these aggregates, there are large regional disparities, with the Central Europe North region and parts of South-East Asia and South Asia being especially prone to high costs (welfare losses in the range of 4–12 %). The analysis assumes that there is not public adaptation, which would substantially lower the costs. In this way, the analysis demonstrates what is at risk, and could be used to justify adaptation expenses.

Variability in transport of terrigenous material on the shelves and the deep Arctic Ocean during the Holocene

Arctic coastal zones serve as a sensitive filter for terrigenous matter input onto the shelves via river discharge and coastal erosion. This material is further distributed across the Arctic by ocean currents and sea ice. The coastal regions are particularly vulnerable to changes related to recent climate change. We compiled a pan-Arctic review that looks into the changing Holocene sources, transport processes and sinks of terrigenous sediment in the Arctic Ocean. Existing palaeoceanographic studies demonstrate how climate warming and the disappearance of ice sheets during the early Holocene initiated eustatic sea-level rise that greatly modified the physiography of the Arctic Ocean. Sedimentation rates over the shelves and slopes were much greater during periods of rapid sea-level rise in the early and middle Holocene, as a result of the relative distance to the terrestrial sediment sources. However, estimates of suspended sediment delivery through major Arctic rivers do not indicate enhanced delivery during this time, which suggests enhanced rates of coastal erosion. The increased supply of terrigenous material to the outer shelves and deep Arctic Ocean in the early and middle Holocene might serve as analogous to forecast changes in the future Arctic.Keywords: Arctic; riverine input; coastal erosion; land–ocean interaction; Holocene.(Published: 9 December 2015)To access the supplementary material for this article, please see supplementary files in the column to the right (under Article Tools).Citation: Polar Research 2015, 34, 24964, http://dx.doi.org/10.3402/polar.v34.24964

Seabed mapping and seafloor processes in the Kish, Burford, Bray and Fraser Banks area, South‐Western Irish Sea

Mapping of the seabed and sub-seabed strata in an area comprising offshore banks and intervening sediments in outer Dublin Bay is presented. Bathymetric comparisons suggest that the offshore banks are quasi-stable over time probably maintaining their position due to the interaction between wave and current regimes. Seven acoustic seabed facies are defined on the basis of side-scan sonar characteristics reflecting differences in bedforms and bottom types. Sediment waves indicative of a mobile substrate are common both on and between banks. Maximum sediment wave development occurs on bank flanks and outer limits. The effects of wave action on seabed morphology are clearly discernible in the structure and appearance of the bank crests. Grain-size data and bedform interpretations suggest a northerly sediment transport system with gravel dominant in the south of the area (Bray Bank) grading to sands in the north (Kish and Burford Banks). Sub-bottom profiling reveals a consistent upper unit overlying a hard reflector allowing unit thickness (isopachs) to be defined. No internal structures or 'hard' cores were revealed within banks. Two shipwrecks were also imaged. Relationships are drawn with models of offshore bank evolution suggesting that the Irish examples are quasi-stable dependent on a relatively consistent input of sediment and metocean variables. Banks genesis, however, may relate more to former conditions of post-glacial rapid sea-level rise and high sediment input.

Estuaries May Face Increased Parasitism as Sea Levels Rise

Invertebrates in estuaries could be at a greater risk of parasitism as climate change causes sea levels to rise. A new paper published 8 December in Proceedings of the National Academy of Sciences of the United States of America (doi:10.1073/pnas.1416747111) describes how rapid sea level rise in the Holocene affected the population of parasitic flatworms called trematodes.

Last Deglaciation Climatic Fluctuation Record by the Palaeo-Daocheng Ice Cap, Southeastern Qinghai-Tibetan Plateau

The last deglaciation, a key period for understanding present and future climate changes, has long been the hot topic for palaeoclimatological study. The Qinghai-Tibetan Plateau (QTP) is often a target study area for understanding hemispheric, or even global environment changes. The glacial landforms on the QTP provide a unique perspective for its climate change. In order to investigate the onset of the last deglaciation at the QTP and its regional correlation, the terrestrial cosmogenic nuclides (TCN) 10Be and 26Al surface exposure dating was chosen to date the roche moutonnee, the polished surface and the moraine debris located at the palaeo-Daocheng Ice Cap (p-DIC), southeastern QTP. Our results show that the onset of the last deglaciation is at about 19 ka, followed by another warming event occurring around 15 ka in the p-DIC area. These timings agree well with other records, e.g. equivalent with a rapid sea level rise at 19 ka and the onset of Bolling warming event at about 15 ka. Thus, our new data can provide good reveal constraint on the climate evolution at the QTP.

Sea-level changes in Iceland and the influence of the North Atlantic Oscillation during the last half millennium

We present a new, diatom-based sea-level reconstruction for Iceland spanning the last ∼500 years, and investigate the possible mechanisms driving the sea-level changes. A sea-level reconstruction from near the Icelandic low pressure system is important as it can improve understanding of ocean–atmosphere forcing on North Atlantic sea-level variability over multi-decadal to centennial timescales. Our reconstruction is from Viðarhólmi salt marsh in Snæfellsnes in western Iceland, a site from where we previously obtained a 2000-yr record based upon less precise sea-level indicators (salt-marsh foraminifera). The 20th century part of our record is corroborated by tide-gauge data from Reykjavik. Overall, the new reconstruction shows ca 0.6 m rise of relative sea level during the last four centuries, of which ca 0.2 m occurred during the 20th century. Low-amplitude and high-frequency sea-level variability is super-imposed on the pre-industrial long-term rising trend of 0.65 m per 1000 years. Most of the relative sea-level rise occurred in three distinct periods: AD 1620–1650, AD 1780–1850 and AD 1950–2000, with maximum rates of ∼3 ± 2 mm/yr during the latter two of these periods. Maximum rates were achieved at the end of large shifts (from negative to positive) of the winter North Atlantic Oscillation (NAO) Index as reconstructed from proxy data. Instrumental data demonstrate that a strong and sustained positive NAO (a deep Icelandic Low) generates setup on the west coast of Iceland resulting in rising sea levels. There is no strong evidence that the periods of rapid sea-level rise were caused by ocean mass changes, glacial isostatic adjustment or regional steric change. We suggest that wind forcing plays an important role in causing regional-scale coastal sea-level variability in the North Atlantic, not only on (multi-)annual timescales, but also on multi-decadal to centennial timescales.