The timing of Mediterranean sapropel deposition relative to insolation, sea-level and African monsoon changes

NASA Astrophysics Data System (ADS)

Grant, Katharine; Grimm, Rosina; Mikolajewicz, Uwe; Marino, Gianluca; Rohling, Eelco

2016-04-01

The periodic deposition of organic rich layers or 'sapropels' in eastern Mediterranean sediments can be linked to orbital-driven changes in the strength and location of (east) African monsoon precipitation. Sapropels are therefore an extremely useful tool for establishing orbital chronologies, and for providing insights about African monsoon variability on long timescales. However, the link between sapropel formation, insolation variations, and African monsoon 'maxima' is not straightforward because other processes (notably, sea-level rise) may have contributed to their deposition, and because there are uncertainties about monsoon-sapropel phase relationships. For example, different phasings are observed between Holocene and early Pleistocene sapropels, and between proxy records and model simulations. To address these issues, we have established geochemical and ice-volume-corrected planktonic foraminiferal stable isotope records for sapropels S1, S3, S4, and S5 in core LC21 from the southern Aegean Sea. The records have a radiometrically constrained chronology that has already been synchronised with the Red Sea relative sea-level record, and this allows us to examine in detail the timing of sapropel deposition relative to insolation, sea-level, and African monsoon changes. Our records suggest that the onset of sapropel deposition and monsoon run-off was near synchronous, yet insolation-sapropel/monsoon phasings varied, whereby monsoon/sapropel onset was relatively delayed (with respect to insolation maxima) after glacial terminations. We suggest that large meltwater discharges into the North Atlantic modified the timing of sapropel deposition by delaying the timing of peak African monsoon run-off. Hence, the previous assumption of a systematic 3-kyr lag between insolation maxima and sapropel midpoints may lead to overestimated insolation-sapropel phasings. We also surmise that both monsoon run-off and sea-level rise were important buoyancy-forcing mechanisms for the studied sapropels, and their relative influences differed per sapropel case. For instance, sea-level rise was clearly important for sapropel S1, whereas monsoon forcing was likely more important for sapropel S5.

Coastal-storm Inundation and Sea-level Rise in New Zealand Scott A. Stephens and Rob Bell

NASA Astrophysics Data System (ADS)

Stephens, S. A.; Bell, R.

2016-12-01

Coastal-storm inundation is a growing problem in New Zealand. It happens occasionally, when the combined forces of weather and sea line up, causing inundation of low-elevation land, coastal erosion, and rivers and stormwater systems to back up causing inland flooding. This becomes a risk where we have placed buildings and infrastructure too close to the coast. Coastal-storm inundation is not a new problem, it has happened historically, but it is becoming more frequent as the sea level continues to rise. From analyses of historic extreme sea-level events, we show how the different sea-level components, such as tide and storm surge, contribute to extreme sea-level and how these components vary around New Zealand. Recent sea-level analyses reveal some large storm surges, bigger than previously reported, and we show the type of weather patterns that drive them, and how this leads to differences in storm surge potential between the east and west coasts. Although large and damaging storm-tides have occurred historically, we show that there is potential for considerably larger elevations to be reached in the "perfect storm", and we estimate the likelihood of such extreme events occurring. Sea-level rise (SLR) will greatly increase the frequency, depth and consequences of coastal-storm inundation in the future. We show an application of a new method to determine the increasing frequency of extreme sea-levels with SLR, one which integrates the extreme tail with regularly-occurring high tides. We present spatial maps of several extreme sea-level threshold exceedance statistics for a case study at Mission Bay, Auckland, New Zealand. The maps show how the local community is likely to face decision points at various SLR thresholds, and we conclude that coastal hazard assessments should ideally use several SLR scenarios and time windows within the next 100 years or more to support the decision-making process for future coastal adaptation and when response options will be needed. In tandem, coastal hazard assessments should also provide information on SLR values linked to expected inundation frequency or depth. This can be linked to plausible timeframes for SLR thresholds to determine when critical decision points for adaptation might be reached, and we show how this might be achieved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slunge, Daniel, E-mail: daniel.slunge@economics.gu.se; Tran, Trang Thi Huyen, E-mail: trang2k@yahoo.com

Building on new institutional theory, this paper develops an analytical framework for analyzing constraints to the institutionalization of strategic environmental assessment (SEA) at four different institutional levels. The framework is tested in an empirical analysis of the environmental assessment system in Vietnam, which is a frontrunner among developing countries regarding the introduction and use of SEA. Building on interviews with Vietnamese and international experts, as well as an extensive literature review, we identify institutional constraints which challenge the effective use of SEA in Vietnam. We conclude that commonly identified constraints, such as inadequate training, technical guidelines, baseline data and financialmore » resources, are strongly linked to constraints at higher institutional levels, such as incentives to not share information between ministries and severe restrictions on access to information and public participation. Without a thorough understanding of these institutional constraints, there is a risk that attempts to improve the use of SEA are misdirected. Thus, a careful institutional analysis should guide efforts to introduce and improve the use of SEA in Vietnam and other developing countries. The analytical framework for analyzing constraints to institutionalization of SEA presented in this paper represents a systematic effort in this direction. - Highlights: • A framework for analyzing constraints to institutionalizing SEA is developed • Empirical analysis of the strategic environmental assessment system in Vietnam • Constraints in the action arena linked to deeper institutional constraints • Institutional analysis needed prior to introducing SEA in developing countries.« less

Historical Sea Level in the South Pacific from Rescued Archives, Geodetic Measurements, and Satellite Altimetry

NASA Astrophysics Data System (ADS)

Aucan, J.; Merrifield, M. A.; Pouvreau, N.

2017-10-01

Automatic sea-level measurements in Nouméa, South Pacific, started in 1957 for the International Geophysical year. Data from this location exist in paper record for the 1957-1967 period, and in two distinct electronic records for the 1967-2005 and 2005-2015 period. In this study, we digitize the early record, and established a link between the two electronic records to create a unique, nearly 60 year-long instrumental sea-level record. This work creates one of the longest instrumental sea-level records in the Pacific Islands. These data are critical for the study of regional and interannual variations of sea level. This new data set is then used to infer rates of vertical movements by comparing it to (1) the entire satellite altimetric record (1993-2013) and (2) a global sea-level reconstruction (1957-2010). These inferred rates show an uplift of 1.3-1.4 mm/year, opposite to the currently accepted values of subsidence found in the geological and geodetic literature, and underlie the importance of systematic geodetic measurements at, over very near tide gauges.

Postglacial Fringing-Reef to Barrier-Reef conversion on Tahiti links Darwin's reef types

NASA Astrophysics Data System (ADS)

Blanchon, Paul; Granados-Corea, Marian; Abbey, Elizabeth; Braga, Juan C.; Braithwaite, Colin; Kennedy, David M.; Spencer, Tom; Webster, Jody M.; Woodroffe, Colin D.

2014-05-01

In 1842 Charles Darwin claimed that vertical growth on a subsiding foundation caused fringing reefs to transform into barrier reefs then atolls. Yet historically no transition between reef types has been discovered and they are widely considered to develop independently from antecedent foundations during glacio-eustatic sea-level rise. Here we reconstruct reef development from cores recovered by IODP Expedition 310 to Tahiti, and show that a fringing reef retreated upslope during postglacial sea-level rise and transformed into a barrier reef when it encountered a Pleistocene reef-flat platform. The reef became stranded on the platform edge, creating a lagoon that isolated it from coastal sediment and facilitated a switch to a faster-growing coral assemblage dominated by acroporids. The switch increased the reef's accretion rate, allowing it to keep pace with rising sea level, and transform into a barrier reef. This retreat mechanism not only links Darwin's reef types, but explains the re-occupation of reefs during Pleistocene glacio-eustacy.

SeaRISE: A Multidisciplinary Research Initiative to Predict Rapid Changes in Global Sea Level Caused by Collapse of Marine Ice Sheets

NASA Technical Reports Server (NTRS)

Bindschadler, Robert A. (Editor)

1990-01-01

The results of a workshop held to discuss the role of the polar ice sheets in global climate change are reported. The participants agreed that the most important aspect of the ice sheets' involvement in climate change is the potential of marine ice sheets to cause a rapid change in global sea level. To address this concern, a research initiative is called for that considers the full complexity of the coupled atmosphere-ocean-cryosphere-lithosphere system. This initiative, called SeaRISE (Sea-level Response to Ice Sheet Evolution) has the goal of predicting the contribution of marine ice sheets to rapid changes in global sea level in the next decade to few centuries. To attain this goal, a coordinated program of multidisciplinary investigations must be launched with the linked objectives of understanding the current state, internal dynamics, interactions, and history of this environmental system. The key questions needed to satisfy these objectives are presented and discussed along with a plan of action to make the SeaRISE project a reality.

Albian to Santonian carbon isotope excursions and faunal extinctions in the Canadian Western Interior Sea: Recognition of eustatic sea-level controls on a forebulge setting

NASA Astrophysics Data System (ADS)

Schröder-Adams, Claudia J.; Herrle, Jens O.; Tu, Qiang

2012-12-01

The forebulge region of the Cretaceous Canadian Western Interior Sea (CWIS) was susceptible to subaerial exposure and marine erosion during sea level lowstands. The middle Albian to Santonian record as cored at Cold Lake, east-central Alberta, Canada documents numerous disconformities that are expressed in bioclastic concentration horizons and faunal extinctions and turnovers. Detailed comparison between a newly established δ13Corg. record measured on bulk sediment at Cold Lake and a combined δ13Ccarb. reference curve based on the Cretaceous English chalk and SE France hemipelagic marlstones highlights missing positive and negative δ13C excursions at the CWIS forebulge and thus missing sections that precisely corroborate with sequence boundaries. Disconformable boundaries correlate closely with global sea-level lowstands as established for the Cretaceous North Atlantic suggesting a pronounced eustatic influence on the CWIS forebulge setting. Sequence boundaries occur in the uppermost Middle Albian, lowermost Upper Albian, Albian/Cenomanian boundary, Cenomanian/Turonian boundary, middle Turonian to lower Coniacian and uppermost Middle Santonian, each followed by a positive δ13C excursion. Oceanic anoxic events 1d, 2 and 3 are recognized and linked to major faunal and floral assemblage changes. Of these the Albian/Cenomanian biotic turnover is the most severe in the CWIS marked by the total loss of Albian benthic foraminifera species. Causes of this benthic extinction might be linked to a period of anoxia (OAE 1d) during the latest Albian followed by sea-level controlled basin restriction.

Cross-linking staphylococcal enterotoxin A bound to major histocompatibility complex class I is required for TNF-alpha secretion

NASA Technical Reports Server (NTRS)

Wright, A. D.; Chapes, S. K.

1999-01-01

The mechanism of how superantigens function to activate cells has been linked to their ability to bind and cross-link the major histocompatibility complex class II (MHCII) molecule. Cells that lack the MHCII molecule also respond to superantigens, however, with much less efficiency. Therefore, the purpose of this study was to confirm that staphylococcal enterotoxin A (SEA) could bind the MHCI molecule and to test the hypothesis that cross-linking SEA bound to MHCII-deficient macrophages would induce a more robust cytokine response than without cross-linking. We used a capture enzyme-linked immunosorbent assay and an immunprecipitation assay to directly demonstrate that MHCI molecules bind SEA. Directly cross-linking MHCI using monoclonal antibodies or cross-linking bound SEA with an anti-SEA antibody or biotinylated SEA with avidin increased TNF-alpha and IL-6 secretion by MHCII(-/-) macrophages. The induction of a vigorous macrophage cytokine response by SEA/anti-SEA cross-linking of MHCI offers a mechanism to explain how MHCI could play an important role in superantigen-mediated pathogenesis. Copyright 1999 Academic Press.

Sea-level rise and archaeological site destruction: An example from the southeastern United States using DINAA (Digital Index of North American Archaeology).

PubMed

Anderson, David G; Bissett, Thaddeus G; Yerka, Stephen J; Wells, Joshua J; Kansa, Eric C; Kansa, Sarah W; Myers, Kelsey Noack; DeMuth, R Carl; White, Devin A

2017-01-01

The impact of changing climate on terrestrial and underwater archaeological sites, historic buildings, and cultural landscapes can be examined through quantitatively-based analyses encompassing large data samples and broad geographic and temporal scales. The Digital Index of North American Archaeology (DINAA) is a multi-institutional collaboration that allows researchers online access to linked heritage data from multiple sources and data sets. The effects of sea-level rise and concomitant human population relocation is examined using a sample from nine states encompassing much of the Gulf and Atlantic coasts of the southeastern United States. A 1 m rise in sea-level will result in the loss of over >13,000 recorded historic and prehistoric archaeological sites, as well as over 1000 locations currently eligible for inclusion on the National Register of Historic Places (NRHP), encompassing archaeological sites, standing structures, and other cultural properties. These numbers increase substantially with each additional 1 m rise in sea level, with >32,000 archaeological sites and >2400 NRHP properties lost should a 5 m rise occur. Many more unrecorded archaeological and historic sites will also be lost as large areas of the landscape are flooded. The displacement of millions of people due to rising seas will cause additional impacts where these populations resettle. Sea level rise will thus result in the loss of much of the record of human habitation of the coastal margin in the Southeast within the next one to two centuries, and the numbers indicate the magnitude of the impact on the archaeological record globally. Construction of large linked data sets is essential to developing procedures for sampling, triage, and mitigation of these impacts.

Sea-level rise and archaeological site destruction: An example from the southeastern United States using DINAA (Digital Index of North American Archaeology)

PubMed Central

Wells, Joshua J.; Kansa, Eric C.; Kansa, Sarah W.; Myers, Kelsey Noack; DeMuth, R. Carl; White, Devin A.

2017-01-01

The impact of changing climate on terrestrial and underwater archaeological sites, historic buildings, and cultural landscapes can be examined through quantitatively-based analyses encompassing large data samples and broad geographic and temporal scales. The Digital Index of North American Archaeology (DINAA) is a multi-institutional collaboration that allows researchers online access to linked heritage data from multiple sources and data sets. The effects of sea-level rise and concomitant human population relocation is examined using a sample from nine states encompassing much of the Gulf and Atlantic coasts of the southeastern United States. A 1 m rise in sea-level will result in the loss of over >13,000 recorded historic and prehistoric archaeological sites, as well as over 1000 locations currently eligible for inclusion on the National Register of Historic Places (NRHP), encompassing archaeological sites, standing structures, and other cultural properties. These numbers increase substantially with each additional 1 m rise in sea level, with >32,000 archaeological sites and >2400 NRHP properties lost should a 5 m rise occur. Many more unrecorded archaeological and historic sites will also be lost as large areas of the landscape are flooded. The displacement of millions of people due to rising seas will cause additional impacts where these populations resettle. Sea level rise will thus result in the loss of much of the record of human habitation of the coastal margin in the Southeast within the next one to two centuries, and the numbers indicate the magnitude of the impact on the archaeological record globally. Construction of large linked data sets is essential to developing procedures for sampling, triage, and mitigation of these impacts. PMID:29186200

Parasites and Holocene sea-level rise: Recurrent upsurges in trematode infestation linked to repeated flooding events in the Adriatic Sea

NASA Astrophysics Data System (ADS)

Scarponi, Daniele; Azzarone, Michele; Kowalewski, Michał; Huntley, John Warren

2017-04-01

The accelerating increase in global temperature and concomitant sea level rise may result in an increased prevalence (i.e. infestation frequency) of many pathogens and parasites. Using the Holocene brackish deposits of the Po Plain, we evaluate this issue from a historical perspective by documenting temporal changes in trematode infestation of mollusk hosts during high-frequency (102-103 yrs) sea-level fluctuations that took place over the most recent millennia. During that time interval, the dominant bivalve species, Abra segmentum, was frequently infested by trematodes. Median body size was significantly larger in infested individuals (p = 2.21*10-34), likely reflecting accumulation of parasites with ontogenetic age. Prevalence estimates were significantly elevated (p < 0.01) in samples of A. segmentum associated with flooding surfaces and significantly depressed (p < 0.01) in intervening samples. In contrast, temporal trends in host body size, host availability, salinity, diversity, turnover, and community structure did not correlate significantly with parasite prevalence. The results reported here reinforce the recently proposed hypothesis that increasing trematode prevalence is linked to flooding events, a pattern now documented in shallow marine and estuarine settings on two continents, in both modern and fossil taxa. Consequently, the ongoing anthropogenic warming and sea-level rise is expected to trigger a significant upsurge in trematode prevalence, resulting in suppressed fecundity of common benthic organisms and negative impacts on marine ecosystems and ecosystem services.

Sea level and turbidity controls on mangrove soil surface elevation change

USGS Publications Warehouse

Lovelock, Catherine E.; Fernanda Adame, Maria; Bennion, Vicki; Hayes, Matthew; Reef, Ruth; Santini, Nadia; Cahoon, Donald R.

2015-01-01

Increases in sea level are a threat to seaward fringing mangrove forests if levels of inundation exceed the physiological tolerance of the trees; however, tidal wetlands can keep pace with sea level rise if soil surface elevations can increase at the same pace as sea level rise. Sediment accretion on the soil surface and belowground production of roots are proposed to increase with increasing sea level, enabling intertidal habitats to maintain their position relative to mean sea level, but there are few tests of these predictions in mangrove forests. Here we used variation in sea level and the availability of sediments caused by seasonal and inter-annual variation in the intensity of La Nina-El Nino to assess the effects of increasing sea level on surface elevation gains and contributing processes (accretion on the surface, subsidence and root growth) in mangrove forests. We found that soil surface elevation increased with mean sea level (which varied over 250 mm during the study) and with turbidity at sites where fine sediment in the water column is abundant. In contrast, where sediments were sandy, rates of surface elevation gain were high, but not significantly related to variation in turbidity, and were likely to be influenced by other factors that deliver sand to the mangrove forest. Root growth was not linked to soil surface elevation gains, although it was associated with reduced shallow subsidence, and therefore may contribute to the capacity of mangroves to keep pace with sea level rise. Our results indicate both surface (sedimentation) and subsurface (root growth) processes can influence mangrove capacity to keep pace with sea level rise within the same geographic location, and that current models of tidal marsh responses to sea level rise capture the major feature of the response of mangroves where fine, but not coarse, sediments are abundant.

Predicting East African spring droughts using Pacific and Indian Ocean sea surface temperature indices

USGS Publications Warehouse

Funk, Christopher C.; Hoell, Andrew; Shukla, Shraddhanand; Blade, Ileana; Liebmann, Brant; Roberts, Jason B.; Robertson, Franklin R.

2014-01-01

In southern Ethiopia, Eastern Kenya, and southern Somalia poor boreal spring rains in 1999, 2000, 2004, 2007, 2008, 2009 and 2011 contributed to severe food insecurity and high levels of malnutrition. Predicting rainfall deficits in this region on seasonal and decadal time frames can help decision makers support disaster risk reduction while guiding climate-smart adaptation and agricultural development. Building on recent research that links more frequent droughts to a stronger Walker Circulation, warming in the Indo-Pacific warm pool, and an increased western Pacific sea surface temperature (SST) gradient, we explore the dominant modes of East African rainfall variability, links between these modes and sea surface temperatures, and a simple index-based monitoring-prediction system suitable for drought early warning.

Effects of El Niño-Southern Oscillation on sea level anomalies along the Gulf of Mexico coast

NASA Astrophysics Data System (ADS)

Kennedy, Andrew J.; Griffin, Melissa L.; Morey, Steven L.; Smith, Shawn R.; O'Brien, James J.

2007-05-01

Analyses of daily sea level data show the impacts of El Niño-Southern Oscillation (ENSO) in the Gulf of Mexico (GOM). Data from three stations (St. Petersburg, Florida, Pensacola, Florida, and Galveston, Texas), all of which have at least 50 years of daily observations, are processed to identify the interannual signals. Although low frequency (interannual) signals in the sea level anomaly time series are not clearly evident, a low frequency modulation of the extreme anomaly events (upper 10% or lower 10% of the distributions) is identified. Results show that sea level variability is seasonally dependent at all stations, with maximum variability in the winter months. In the eastern GOM, low sea level events in the winter months are more frequent during El Niño (warm phase) conditions when compared to a neutral ENSO phase. This is consistent with ENSO-related changes in the location where extratropical atmospheric low pressure systems form and in the tracks of these weather systems. The impacts of tropical systems in the summer through early fall months on coastal sea level in the GOM are shown by infrequent extreme high and low anomalies coinciding with individual storms. However, the number of storms affecting the data record from a particular sea level station is too small to confirm ENSO-related variability. Statistical methods are employed to demonstrate a significant link between extreme sea level anomalies in the GOM and ENSO during the October to March period.

Improvement of global and regional mean sea level derived from satellite altimetry multi missions

NASA Astrophysics Data System (ADS)

Ablain, M.; Faugere, Y.; Larnicol, G.; Picot, N.; Cazenave, A.; Benveniste, J.

2012-04-01

With the satellite altimetry missions, the global mean sea level (GMSL) has been calculated on a continual basis since January 1993. 'Verification' phases, during which the satellites follow each other in close succession (Topex/Poseidon--Jason-1, then Jason-1--Jason-2), help to link up these different missions by precisely determining any bias between them. Envisat, ERS-1 and ERS-2 are also used, after being adjusted on these reference missions, in order to compute Mean Sea Level at high latitudes (higher than 66°N and S), and also to improve spatial resolution by combining all these missions together. The global mean sea level (MSL) deduced from TOPEX/Poseidon, Jason-1 and Jason-2 provide a global rate of 3.2 mm from 1993 to 2010 applying the post glacial rebound (MSL aviso website http://www.jason.oceanobs.com/msl). Besides, the regional sea level trends bring out an inhomogeneous repartition of the ocean elevation with local MSL slopes ranging from + 8 mm/yr to - 8 mm/year. A study published in 2009 [Ablain et al., 2009] has shown that the global MSL trend unceratainty was estimated at +/-0.6 mm/year with a confidence interval of 90%. The main sources of errors at global and regional scales are due to the orbit calculation and the wet troposphere correction. But others sea-level components have also a significant impact on the long-term stability of MSL as for instance the stability of instrumental parameters and the atmospheric corrections. Thanks to recent studies performed in the frame of the SALP project (supported by CNES) and Sea-level Climate Change Initiative project (supported by ESA), strong improvements have been provided for the estimation of the global and regional MSL trends. In this paper, we propose to describe them; they concern the orbit calculation thanks to new gravity fields, the atmospheric corrections thanks to ERA-interim reanalyses, the wet troposphere corrections thanks to the stability improvement, and also empirical corrections allowing us to link regional time series together better. These improvements are described at global and regional scale for all the altimetry missions.

An improved empirical dynamic control system model of global mean sea level rise and surface temperature change

NASA Astrophysics Data System (ADS)

Wu, Qing; Luu, Quang-Hung; Tkalich, Pavel; Chen, Ge

2018-04-01

Having great impacts on human lives, global warming and associated sea level rise are believed to be strongly linked to anthropogenic causes. Statistical approach offers a simple and yet conceptually verifiable combination of remotely connected climate variables and indices, including sea level and surface temperature. We propose an improved statistical reconstruction model based on the empirical dynamic control system by taking into account the climate variability and deriving parameters from Monte Carlo cross-validation random experiments. For the historic data from 1880 to 2001, we yielded higher correlation results compared to those from other dynamic empirical models. The averaged root mean square errors are reduced in both reconstructed fields, namely, the global mean surface temperature (by 24-37%) and the global mean sea level (by 5-25%). Our model is also more robust as it notably diminished the unstable problem associated with varying initial values. Such results suggest that the model not only enhances significantly the global mean reconstructions of temperature and sea level but also may have a potential to improve future projections.

Analysis of the most recent data of Cascais Tide Gauge

NASA Astrophysics Data System (ADS)

Antunes, Carlos; Taborda, Rui; Mendes, Virgílio B.

2010-05-01

In order to meet international standards and to integrate sea level changes and tsunami monitoring networks, Cascais tide gauge, one of the oldest in the world, has been upgraded in 2003 with new acoustic equipment with digital data acquisition, temperature and air-pressure sensors, and internet connection for real time data. The new tide gauge is located very close to the old analogical gauge, which is still working. Datum links between both gauges and the permanent GPS station of Cascais were made and height differences between gauges and the GPS station have been monitored to verify site stability and to estimate the absolute vertical velocity of the site, and therefore, the absolute sea level changes. Tide gauge data from 2000 to 2009 has been analyzed and relative and absolute sea level rise rates have been estimated. The estimation of sea level rise rate with the short baseline of 10 years is made with the daily mean sea level data corrected from the inverse barometric effect. The relative sea level trend is obtained from a 60-day moving average run over the corrected daily mean sea level. The estimated rate has shown greater stability in contrast to the analysis of daily mean sea level raw data, which shows greater variability and uncertainty. Our results show a sea level rise rate of 2.6 mm/year (± 0.3 mm/year), higher than previous rates (2.1 mm/year for 1990 decade and 1.6 mm/year from 1920 to 2000), which is compatible with a sea level rise acceleration scenario. From the analysis of Cascais GPS data, for the period 1990.0 to 2010.0 we obtain an uplift rate of 0.3 mm/year leading to an absolute sea level rise of 2.9 mm/year for Cascais, under the assumption, as predicted by the ICE-5G model, that Cascais has no vertical displacement caused by the post-glacial isostatic adjustment.

Marshes to mudflats—Effects of sea-level rise on tidal marshes along a latitudinal gradient in the Pacific Northwest

USGS Publications Warehouse

Thorne, Karen M.; Dugger, Bruce D.; Buffington, Kevin J.; Freeman, Chase M.; Janousek, Christopher N.; Powelson, Katherine W.; Gutenspergen, Glenn R.; Takekawa, John Y.

2015-11-17

In the Pacific Northwest, coastal wetlands support a wealth of ecosystem services including habitat provision for wildlife and fisheries and flood protection. The tidal marshes, mudflats, and shallow bays of coastal estuaries link marine, freshwater, and terrestrial habitats, and provide economic and recreational benefits to local communities. Climate change effects such as sea-level rise are altering these habitats, but we know little about how these areas will change over the next 50–100 years. Our study examined the effects of sea-level rise on nine tidal marshes in Washington and Oregon between 2012 and 2015, with the goal of providing scientific data to support future coastal planning and conservation. We compiled physical and biological data, including coastal topography, tidal inundation, vegetation structure, as well as recent and historical sediment accretion rates, to assess and model how sea-level rise may alter these ecosystems in the future. Multiple factors, including initial elevation, marsh productivity, sediment availability, and rates of sea-level rise, affected marsh persistence. Under a low sea-level rise scenario, all marshes remained vegetated with little change in the present configuration of communities of marsh plants or gradually increased proportions of middle-, high-, or transition-elevation zones of marsh vegetation. However, at most sites, mid sea-level rise projections led to loss of habitat of middle and high marshes and a gain of low marshes. Under a high sea-level rise scenario, marshes at most sites eventually converted to intertidal mudflats. Two sites (Grays Harbor and Willapa) seemed to have the most resilience to a high rate of rise in sea-level, persisting as low marsh until at least 2110. Our main model finding is that most tidal marsh study sites are resilient to sea-level rise over the next 50–70 years, but that sea-level rise will eventually outpace marsh accretion and drown most habitats of high and middle marshes by 2110.

Global ice-sheet system interlocked by sea level

NASA Astrophysics Data System (ADS)

Denton, George H.; Hughes, Terence J.; Karlén, Wibjörn

1986-07-01

Denton and Hughes (1983, Quaternary Research20, 125-144) postulated that sea level linked a global ice-sheet system with both terrestrial and grounded marine components during late Quaternary ice ages. Summer temperature changes near Northern Hemisphere melting margins initiated sea-level fluctuations that controlled marine components in both polar hemispheres. It was further proposed that variations of this ice-sheet system amplified and transmitted Milankovitch summer half-year insolation changes between 45 and 75°N into global climatic changes. New tests of this hypothesis implicate sea level as a major control of the areal extent of grounded portions of the Antarctic Ice Sheet, thus fitting the concept of a globally interlocked ice-sheet system. But recent atmospheric modeling results ( Manabe and Broccoli, 1985, Journal of Geophysical Research90, 2167-2190) suggest that factors other than areal changes of the grounded Antarctic Ice Sheet strongly influenced Southern Hemisphere climate and terminated the last ice age simultaneously in both polar hemispheres. Atmospheric carbon dioxide linked to high-latitude oceans is the most likely candidate ( Shackleton and Pisias, 1985, Atmospheric carbon dioxide, orbital forcing, and climate. In "The Carbon Cycle and Atmospheric CO 2: Natural Variations Archean to Present" (E. T. Sundquest and W. S. Broecker, Eds.), pp. 303-318. Geophysical Monograph 32, American Geophysical Union, Washington, D.C.), but another potential influence was high-frequency climatic oscillations (2500 yr). It is postulated that variations in atmospheric carbon dioxide acted through an Antarctic ice shelf linked to the grounded ice sheet to produce and terminate Southern Hemisphere ice-age climate. It is further postulated that Milankovitch summer insolation combined with a warm high-frequency oscillation caused marked recession of Northern Hemisphere ice-sheet melting margins and the North Atlantic polar front about 14,000 14C yr B.P. This permitted renewed formation of North Atlantic Deep Water, which could well have controlled atmospheric carbon dioxide ( W. S. Broecker, D. M. Peteet, and D. Rind, 1985, Nature ( London) 315, 21-26). Combined melting and consequent sea-level rise from the three warming factors initiated irreversible collapse of the interlocked global ice-sheet system, which was at its largest but most vulnerable configuration.

Late Pleistocene Sea level on the New Jersey Margin: Implications to eustasy and deep-sea temperature

USGS Publications Warehouse

Wright, J.D.; Sheridan, R.E.; Miller, K.G.; Uptegrove, J.; Cramer, B.S.; Browning, J.V.

2009-01-01

We assembled and dated a late Pleistocene sea-level record based on sequence stratigraphy from the New Jersey margin and compared it with published records from fossil uplifted coral reefs in New Guinea, Barbados, and Araki Island, as well as a composite sea-level estimate from scaling of Red Sea isotopic values. Radiocarbon dates, amino acid racemization data, and superposition constrain the ages of large (20-80??m) sea-level falls from New Jersey that correlate with Marine Isotope Chrons (MIC) 2, 3b, 4, 5b, and 6 (the past 130??kyr). The sea-level records for MIC 1, 2, 4, 5e, and 6 are similar to those reported from New Guinea, Barbados, Araki, and the Red Sea; some differences exist among records for MIC 3. Our record consistently provides the shallowest sea level estimates for MIC3 (??? 25-60??m below present); it agrees most closely with the New Guinea record of Chappell (2002; ??? 35-70??m), but contrasts with deeper estimates provided by Araki (??? 85-95??m) and the Red Sea (50-90??m). Comparison of eustatic estimates with benthic foraminiferal ??18O records shows that the deep sea cooled ??? 2.5????C between MIC 5e and 5d (??? 120-110??ka) and that near freezing conditions persisted until Termination 1a (14-15??ka). Sea-level variations between MIC 5b and 2 (ca. 90-20??ka) follow a well-accepted 0.1???/10??m linear variation predicted by ice-growth effects on foraminiferal ??18O values. The pattern of deep-sea cooling follows a previously established hysteresis loop between two stable modes of operation. Cold, near freezing deep-water conditions characterize most of the past 130??kyr punctuated only by two warm intervals (the Holocene/MIC 1 and MIC 5e). We link these variations to changes in Northern Component Water (NCW). ?? 2009 Elsevier B.V. All rights reserved.

Morphology of a submerged insular shelves in the West Alboran Basin.

NASA Astrophysics Data System (ADS)

Lafosse, Manfred; Le Roy, Pascal; Gorini, Christian; Rabineau, Marina; d'Acremont, Elia; Rabaute, Alain

2017-04-01

The dynamic of the seafloor in the Western Mediterranean Sea reflects the variety of the natural processes shaping it. Each of the sub-surface features is the result of tectonic, sedimentary and oceanic processes and eustatic sea-level variations. This study is focused on the morphology of three flat bathymetric highs and on the continental shelf in the Alboran Sea that show a variety of detailed seabed features that we attribute to a combination of present-day Mediterranean water mass flows, Quaternary active folding and faulting, differential erosion linked to relative-sea-level variation and local hydrodynamic. Swath bathymetry and reflectivity data, 2D seismic lines of multiple resolutions (12 channels, SPARKER source, and TOPAS seismic lines) have been acquired during three successive cruises: the MARLBORO-1 (2011), the MARLBORO-2 (2012) and the SARAS (2012) surveys. Our study deciphers the seabed structure of the banks with morphometric measurements (slope gradient, plan curvature, and topographic index) and correlates these structures to the stratigraphy of surrounding shelf. We show that the competition between active folding of the Miocene units and the erosion linked to the late Quaternary lowstands is creates the topography of the banks. The elevations of the flat surfaces measured on the banks are close to -110m and -80m. They are interpreted as submerged depositional surfaces linked to glacial and post-glacial deposit and wave-ravinement erosional surfaces as observed in other Mediterranean continental shelves. The analysis of the altitudinal spacing of these marine terraces indicates a spatial pattern with varying uplift rates. Furthermore, the characterization of sub-aqueous dune patterns locally linked to potential cold carbonate seamount could reflect the influence of water-masses current on the stratigraphic organization.

Global mean sea level - Indicator of climate change

NASA Technical Reports Server (NTRS)

Robock, A.; Hansen, J.; Gornitz, V.; Lebedeff, S.; Moore, E.; Etkins, R.; Epstein, E.

1983-01-01

A critical discussion is presented on the use by Etkins and Epstein (1982) of combined surface air temperature and sea level time series to draw conclusions concerning the discharge of the polar ice sheets. It is objected by Robock that they used Northern Hemisphere land surface air temperature records which are unrepresentative of global sea surface temperature, and he suggests that externally imposed volcanic dust and CO2 forcings can adequately account for observed temperature changes over the last century, with global sea level changing in passive response to sea change as a result of thermal expansion. Hansen et al. adduce evidence for global cooling due to ice discharge that has not exceeded a few hundredths of a degree centigrade in the last century, precluding any importance of this phenomenon in the interpretation of global mean temperature trends for this period. Etkins and Epstein reply that since their 1982 report additional evidence has emerged for the hypothesis that the polar ice caps are diminishing. It is reasserted that each of the indices discussed, including global mean sea surface temperature and sea level, polar ice sheet mass balance, water mass characteristics, and the spin rate and axis of rotation displacement of the earth, are physically linked and can be systematically monitored, as is currently being planned under the auspices of the National Climate Program.

Nuisance Flooding and Relative Sea-Level Rise: the Importance of Present-Day Land Motion.

PubMed

Karegar, Makan A; Dixon, Timothy H; Malservisi, Rocco; Kusche, Jürgen; Engelhart, Simon E

2017-09-11

Sea-level rise is beginning to cause increased inundation of many low-lying coastal areas. While most of Earth's coastal areas are at risk, areas that will be affected first are characterized by several additional factors. These include regional oceanographic and meteorological effects and/or land subsidence that cause relative sea level to rise faster than the global average. For catastrophic coastal flooding, when wind-driven storm surge inundates large areas, the relative contribution of sea-level rise to the frequency of these events is difficult to evaluate. For small scale "nuisance flooding," often associated with high tides, recent increases in frequency are more clearly linked to sea-level rise and global warming. While both types of flooding are likely to increase in the future, only nuisance flooding is an early indicator of areas that will eventually experience increased catastrophic flooding and land loss. Here we assess the frequency and location of nuisance flooding along the eastern seaboard of North America. We show that vertical land motion induced by recent anthropogenic activity and glacial isostatic adjustment are contributing factors for increased nuisance flooding. Our results have implications for flood susceptibility, forecasting and mitigation, including management of groundwater extraction from coastal aquifers.

Links of the significant wave height distribution in the Mediterranean sea with the Northern Hemisphere teleconnection patterns

NASA Astrophysics Data System (ADS)

Lionello, P.; Galati, M. B.

2008-06-01

This study analyzes the link between the SWH (Significant Wave Height) distribution in the Mediterranean Sea during the second half of the 20th century and the Northern Hemisphere SLP (Sea Level Pressure) teleconnection patterns. The SWH distribution is computed using the WAM (WAve Model) forced by the surface wind fields provided by the ERA-40 reanalysis for the period 1958-2001. The time series of mid-latitude teleconnection patterns are downloaded from the NOAA web site. This study shows that several mid-latitude patterns are linked to the SWH field in the Mediterranean, especially in its western part during the cold season: East Atlantic Pattern (EA), Scandinavian Pattern (SCA), North Atlantic Oscillation (NAO), East Atlantic/West Russia Pattern (EA/WR) and East Pacific/ North Pacific Pattern (EP/NP). Though the East Atlantic pattern exerts the largest influence, it is not sufficient to characterize the dominant variability. NAO, though relevant, has an effect smaller than EA and comparable to other patterns. Some link results from possibly spurious structures. Patterns which have a very different global structure are associated to similar spatial features of the wave variability in the Mediterranean Sea. These two problems are, admittedly, shortcomings of this analysis, which shows the complexity of the response of the Mediterranean SWH to global scale SLP teleconnection patterns.

Uncovering the Anthropogenic Sea Level Change using an Improved Sea Level Reconstruction for the Indian Ocean

NASA Astrophysics Data System (ADS)

Kumar, P.; Hamlington, B.; Thompson, P. R.; Han, W.

2016-12-01

Despite having some of the world's most densely populated and vulnerable coastal regions, sea level (SL) variability in the Indian Ocean (IO) has received considerably less attention than the Pacific Ocean. Differentiating the internal variability from the long-term trend in global mean sea level (GMSL) at decadal time-scales is vital for planning and mitigation efforts in the IO region. Understanding the dynamics of internal and anthropogenic SL change is essential for understanding the dynamic pathways that link the IO basin to terrestrial climates world-wide. With a sparse pre-satellite observational record of the IO, the Indo-Pacific internal climate variability is difficult to represent accurately. However, an improved representation of pre-satellite SL variability can be achieved by using a multivariate reconstruction technique. By using cyclostationary empirical orthogonal functions (CSEOFs) that can capture time-varying spatial patterns, gaps in the historical record when observations are sparse are filled using spatial relationships from time periods when the observational network is dense. This reconstruction method combines SL data and sea surface temperature (SST) to create a SL reconstruction that spans a period from 1900 to present, long enough to study climate signals over interannual to decadal time scales. This study aims at estimating the component of SL rise that relates to anthropogenic forcing by identifying and removing the fraction related to internal variability. An improved understanding of how the internal climate variability can affect the IO SL trend and variability, will provide an insight into the future SL changes. It is also important to study links between SL and climate variability in the past to understand how SL will respond to similar climatic events in the future and if this response will be influenced by the changing climate.

Abrupt aridities in the Levant-Sahel linked with solar activities

NASA Astrophysics Data System (ADS)

Stein, M.; Kushnir, Y.

2012-04-01

Observations of 19th and 20th century precipitation in the Dead Sea watershed region display a multidecadal, anti-phase relationship to North Atlantic (NAtl) sea surface temperature (SST) variability, such that when the NAtl is relatively cold, Jerusalem experiences higher than normal precipitation and vice versa. This association is underlined by a negative correlation to precipitation in the sub-Saharan Sahel and a positive correlation to precipitation in western North America, areas that are also affected by multidecadal NAtl SST variability. These observations are consistent with broad range of Holocene hydroclimatic fluctuations from the epochal, to the millennial and centennial time scales, as displayed by the Dead Sea and Sahelian lake levels and by direct and indirect proxy indicators of NAtl SSTs. On the epochal time scale, the gradual cooling of NAtl SSTs throughout the Holocene in response to precession-driven reduction of summer insolation is associated with previously well-studied wet-to-dry transition in the Sahel and with a general increase in Dead Sea lake levels from low stands after the Younger Dryas to higher stands in the mid- to late-Holocene. On the millennial and centennial time scales there is also evidence for an antiphase relationship between Holocene variations in the Dead Sea and Sahelian lake levels and with proxy indicators of NAtl SSTs. However, the records are punctuated by abrupt lake-level drops and extensive expansion of the desert belt at ~8.1, 5.7, 3.3 and 1.4 ka cal BP, which appear to be in-phase and which occur during previously documented abrupt major cooling events in the Northern Hemisphere. We link these cooling to solar activity variations that were identified in the North Atlantic IRD and cosmogenic isotopes records.

Intensification of decadal and multi-decadal sea level variability in the western tropical Pacific during recent decades

NASA Astrophysics Data System (ADS)

Han, Weiqing; Meehl, Gerald A.; Hu, Aixue; Alexander, Michael A.; Yamagata, Toshio; Yuan, Dongliang; Ishii, Masayoshi; Pegion, Philip; Zheng, Jian; Hamlington, Benjamin D.; Quan, Xiao-Wei; Leben, Robert R.

2014-09-01

Previous studies have linked the rapid sea level rise (SLR) in the western tropical Pacific (WTP) since the early 1990s to the Pacific decadal climate modes, notably the Pacific Decadal Oscillation in the north Pacific or Interdecadal Pacific Oscillation (IPO) considering its basin wide signature. Here, the authors investigate the changing patterns of decadal (10-20 years) and multidecadal (>20 years) sea level variability (global mean SLR removed) in the Pacific associated with the IPO, by analyzing satellite and in situ observations, together with reconstructed and reanalysis products, and performing ocean and atmosphere model experiments. Robust intensification is detected for both decadal and multidecadal sea level variability in the WTP since the early 1990s. The IPO intensity, however, did not increase and thus cannot explain the faster SLR. The observed, accelerated WTP SLR results from the combined effects of Indian Ocean and WTP warming and central-eastern tropical Pacific cooling associated with the IPO cold transition. The warm Indian Ocean acts in concert with the warm WTP and cold central-eastern tropical Pacific to drive intensified easterlies and negative Ekman pumping velocity in western-central tropical Pacific, thereby enhancing the western tropical Pacific SLR. On decadal timescales, the intensified sea level variability since the late 1980s or early 1990s results from the "out of phase" relationship of sea surface temperature anomalies between the Indian and central-eastern tropical Pacific since 1985, which produces "in phase" effects on the WTP sea level variability.

Relative Sea Level Trends Along the Coast of the Bay of Bengal

NASA Astrophysics Data System (ADS)

Becker, M.; Calmant, S.; Papa, F.; Delebecque, C.; Islam, A. S.; Shum, C. K.

2016-12-01

In the coastal belt of the Bay of Bengal, the sea level rise is one of a major threat, linked to climate change, which drastically affects the livelihoods of millions of people. A comprehensive understanding of sea level trends and its variability in this region is therefore crucial and should help to anticipate the impacts of climate change and implement adaptation strategies. This region is bordered mostly by Bangladesh, India, Malaysia, Myanmar, and Thailand. Here, we revisit the sea level changes in the Bay of Bengal region from tide gauges and satellite altimetry over the period 1993-2014. The 23 monthly mean tide gauge records, used in this study, are retrieved from PSMSL (15 records) and supplemented with Bangladeshi observations (8 records). We show that, over the satellite altimetry era, the sea level interannual/decadal variability is mainly due to ocean thermal expansion variability driven by IOD/ENSO events and their low frequency modulation. We focus on relative sea level rise at major coastal cities and try to separate the climatic signal (long term trend plus interannual/decadal variability) from local effects, in particular vertical land movements. Results from GPS are analysed where available. When no such data exist, vertical land movements are deduced from the combined use of tide gauge and altimetry data. While the analysis is performed over the whole region, a particular attention is given to the low-lyingBangladesh's coastal area.

The vertical correction of point cloud strips performed over the coastal zone of changing sea level

NASA Astrophysics Data System (ADS)

Gasińska-Kolyszko, Ewa; Furmańczyk, Kazimierz

2017-10-01

The main principle of LIDAR is to measure the accurate time of the laser pulses sent from the system to the target surface. In the operation, laser pulses gradually scan the water surface and in combination with aircraft speed they should perform almost simultaneous soundings of each strip. Vectors sent from aircraft to the Sea are linked to the position of the aircraft. Coordinates of the points - X, Y, Z, are calculated at the time of each measurement. LIDAR crosses the surface of the sea while other impulses pass through the water column and, depending on the depth of the water, reflect from the seabed. Optical receiver on board of the aircraft detects pulse reflections from the seabed and sea surface. On the tidal water basins lidar strips must be adjusted by the changes in sea level. The operation should be reduced to a few hours during low water level. Typically, a surface of 20 to 30 km2 should be covered in an hour. The Baltic Sea is an inland sea, and the surveyed area is located in its South - western part, where meteorological and hydrological conditions affect the sea level changes in a short period of time. A lidar measurement of sea surface, that was done within 2 days, in the coastal zone of the Baltic Sea and the sea level measured 6 times a day at 8, 12, 16, 20, 00, 04 by a water gauge located in the port of Dziwnów (Poland) were used for this study. On the basis of the lidar data, strips were compared with each other. Calculation of time measurement was made for each single line separately. Profiles showing the variability of sea level for each neighboring and overlapping strips were generated. Differences were calculated changes in sea level were identified and on such basis, an adjustment was possible to perform. Microstation software and terrasolid application were used during the research. The latter allowed automatically and manual classification of the point cloud. A sea surface class was distinguished that way. Point cloud was adjusted to flight lines in terms of time and then compared.

Sea-level changes vs. organic productivity as controls on Early and Middle Devonian bioevents: Facies- and gamma-ray based sequence-stratigraphic correlation of the Prague Basin, Czech Republic

NASA Astrophysics Data System (ADS)

Bábek, Ondřej; Faměra, Martin; Šimíček, Daniel; Weinerová, Hedvika; Hladil, Jindřich; Kalvoda, Jiří

2018-01-01

The Devonian marine stratigraphic record is characterized by a number of bioevents - overturns in pelagic and benthic faunal assemblages, which are associated with distinct changes in lithology. The coincidence of lithologic and biotic changes can be explained by the causal link between biotic evolution, carbonate production and relative sea-level changes. To gain insight into the sea-level history of Early and Middle Devonian bioevents (the Lochkovian/Pragian Event, Basal Zlíchovian E., Daleje E., and Choteč E.) we carried out a sequence-stratigraphic analysis of carbonate-dominated successions in the Prague Basin (peri-Gondwana), a classic area of Devonian bioevents. The study is based on a basin-wide correlation of facies and field gamma-ray spectrometry (GRS) logs from 18 sections (Lochkovian to Eifelian), supported by element geochemistry and published biostratigraphic and carbon isotope data. Devonian carbonate deposition in the Prague Basin alternated between two end-member modes: an oligotrophic, homoclinal ramp (Praha and Daleje-Třebotov Formations) and a mesotrophic, distally steepened ramp (Lochkov, Zlíchov, and Choteč Formations). They show contrasting facies, particularly the absence/presence of gravity-flow deposits, allochem composition, U/Th ratios, and geochemical composition (productivity proxies such as P/Al, Si/Al, Zn/Al, TOC and stable carbon isotopes). The mesotrophic systems reflect an increased availability of nutrients on the shelf during the late Lochkovian, early Emsian (Zlíchovian), and Eifelian periods when sea surface temperature, pCO2, and silicate weathering rates were higher. The oligotrophic systems deposited during the Pragian-to-earliest Emsian and late Emsian (Dalejan) periods reflect reversed palaeoclimatic trends. We identified three depositional sequences (DS), DS1 (base of Pragian to early Emsian); DS2 (early Emsian to mid Emsian); and DS3 (mid Emsian to mid Eifelian). These sequences were integrated into a peri-Gondwana relative sea-level curve, which was then compared with the Euramerican sea-level curve of Johnson et al. (1985). The bioevents coincided with several sequence stratigraphic surfaces, representing variable limbs of the relative sea-level curve. On the other hand, their conspicuous coincidence with the switching intervals between the colder oligotrophic and warmer mesotrophic modes suggests that organic production linked to global climate was the primary control on biotic overturns, while sea-level fluctuations may have only amplified its effects.

Analysis of global impacts of sea-level rise: a case study of flooding

NASA Astrophysics Data System (ADS)

Nicholls, Robert J.

Analysis of the response to climate change and sea-level rise requires a link from climate change science to the resulting impacts and their policy implications. This paper explores the impacts of sea-level rise, particularly increased coastal flooding due to storm surges. In particular, it asks the simple question “how much will projected global sea-level rise exacerbate coastal flood problems, if ignored?” This is an important question to the intergovernmental process considering climate change. Further many countries presently ignore sea-level rise in long-term coastal planning, even though global sea levels are presently slowly rising. Using the model of Nicholls et al. [Global Environmental Change 9 (1999) S69], the analysis considers the flood impacts of sea-level rise on an “IS92a world” based on a consistent set of scenarios of global-mean sea-level rise, subsidence (where appropriate), coastal population change (usually increase), and flood defence standards (derived from GDP/capita). Two of the protection scenarios consider the possible upgrade of flood defences, but no allowance for global-mean sea-level rise is allowed to ensure consistency with the question being investigated. This model has been validated against national- and regional-scale assessments indicating that the relative results are reasonable, and the absolute results are of the right order of magnitude. The model estimates that 10 million people experienced flooding annually in 1990. It also predicts that the incidence of flooding will change without sea-level rise due to changes to the other three factors. Taking the full range of scenarios considered by 2100 the number of people flooded could be from 0.4 to 39 million/year. All the sea-level rise scenarios would cause an increase in flooding during the 21st century if measures to adapt to sea-level rise are not taken. However, there are significant uncertainties and the number of people who are estimated to experience flooding in 2100 is 16-388 million for the mid (55-cm) global-mean sea-level rise scenarios, and up to 510 million people/year for the high (96-cm) scenario. These results suggest that sea-level rise could be a significant problem if it is ignored, and hence it needs to be considered within the policy process considering climate change in terms of mitigation (reducing greenhouse gas emissions) and adaptation (improved coastal management and planning) needs.

A numerical study of the South China Sea Warm Current during winter monsoon relaxation

NASA Astrophysics Data System (ADS)

Zhang, Cong; Ding, Yang; Bao, Xianwen; Bi, Congcong; Li, Ruixiang; Zhang, Cunjie; Shen, Biao; Wan, Kai

2018-03-01

Using a Finite-Volume Community Ocean Model, we investigated the dynamic mechanism of the South China Sea Warm Current (SCSWC) in the northern South China Sea (NSCS) during winter monsoon relaxation. The model reproduces the mean surface circulation of the NSCS during winter, while model-simulated subtidal currents generally capture its current pattern. The model shows that the current over the continental shelf is generally southwestward, under a strong winter monsoon condition, but a northeastward counter-wind current usually develops between 50-and 100-m isobaths, when the monsoon relaxes. Model experiments, focusing on the wind relaxation process, show that sea level is elevated in the northwestern South China Sea (SCS), related to the persistent northeasterly monsoon. Following wind relaxation, a high sea level band builds up along the mid-shelf, and a northeastward current develops, having an obvious vertical barotropic structure. Momentum balance analysis indicates that an along-shelf pressure gradient provides the initial driving force for the SCSWC during the first few days following wind relaxation. The SCSWC subsequently reaches a steady quasi-geostrophic balance in the cross-shelf direction, mainly linked to sea level adjustment over the shelf. Lagrangian particle tracking experiments show that both the southwestward coastal current and slope current contribute to the northeastward movement of the SCSWC during winter monsoon relaxation.

Forecasting consequences of changing sea ice availability for Pacific walruses

USGS Publications Warehouse

Udevitz, Mark S.; Jay, Chadwick V.; Taylor, Rebecca; Fischbach, Anthony S.; Beatty, William S.; Noren, Shawn R.

2017-01-01

The accelerating rate of anthropogenic alteration and disturbance of environments has increased the need for forecasting effects of environmental change on fish and wildlife populations. Models linking projections of environmental change with behavioral responses and bioenergetic effects can provide a basis for these forecasts. There is particular interest in forecasting effects of projected reductions in sea ice availability on Pacific walruses (Odobenus rosmarus divergens). Declining extent of summer sea ice in the Chukchi Sea has caused Pacific walruses to increase use of coastal haulouts and decrease use of more productive offshore feeding areas. Such climate-induced changes in distribution and behavior could ultimately affect the status of the population. We developed behavioral models to relate changes in sea ice availability to adult female walrus movements and activity levels, and adapted previously developed bioenergetics models to relate those activity levels to energy requirements and the ability to meet those requirements. We then linked these models to general circulation model projections of future ice availability to forecast autumn body condition for female walruses during mid- and late-century time periods. Our results suggest that as sea ice becomes less available in the Chukchi Sea, female walruses will spend more time in the southwestern region of that sea, less time resting, and less time foraging. Median forecasted autumn body masses were 7–12% lower in future scenarios than during recent times, but posterior distributions broadly overlapped and median forecasted seasonal mass losses (15–34%) were comparable to seasonal mass losses routinely experienced by other pinnipeds. These seasonal reductions in body condition would be unlikely to result in demographic effects, but if walruses were unable to rebuild endogenous reserves while wintering in the Bering Sea, cumulative effects could have implications for reproduction and survival, ultimately affecting the status of the Pacific walrus population. Our approach provides a general framework for forecasting consequences of the broad range of environmental changes and anthropogenic disturbances that may affect bioenergetics through behavioral responses or changes in prey availability.

Gulf of Mexico Imagery - Satellite Products and Services Division/Office of

Science.gov Websites

Satellite and Product Operations Skip Navigation Link NESDIS banner image and link to NESDIS Home Page Default Office of Satellite and Product Operations banner image and link to OSPO DOC / NOAA Bleaching -- Ocean Color -- Sea/Lake Ice -- Sea Surface Height -- Sea Surface Temperatures -- Tropical

Southwest U.S. Imagery (GOES-WEST) - Satellite Services Division / Office

Science.gov Websites

of Satellite Data Processing and Distribution Skip Navigation Link NESDIS banner image and link Information Service Home Page Default Office of Satellite and Product Operations banner image and link to OSPO Color -- Sea/Lake Ice -- Sea Surface Height -- Sea Surface Temperatures -- Tropical Systems Product List

Tropical Pacific Imagery - Satellite Products and Services Division/Office

Science.gov Websites

of Satellite and Product Operations Skip Navigation Link NESDIS banner image and link to NESDIS Home Page Default Office of Satellite and Product Operations banner image and link to OSPO DOC / NOAA Bleaching -- Ocean Color -- Sea/Lake Ice -- Sea Surface Height -- Sea Surface Temperatures -- Tropical

Tropical Atlantic Imagery - Satellite Products and Services Division/Office

Science.gov Websites

of Satellite and Product Operations Skip Navigation Link NESDIS banner image and link to NESDIS Home Page Default Office of Satellite and Product Operations banner image and link to OSPO DOC / NOAA Bleaching -- Ocean Color -- Sea/Lake Ice -- Sea Surface Height -- Sea Surface Temperatures -- Tropical

Hierarchy of sedimentary discontinuity surfaces and condensed beds from the middle Paleozoic of eastern North America: Implications for cratonic sequence stratigraphy

USGS Publications Warehouse

McLaughlin, P.I.; Brett, Carlton E.; Wilson, M.A.

2008-01-01

Sedimentological analyses of middle Paleozoic epeiric sea successions in North America suggest a hierarchy of discontinuity surfaces and condensed beds of increasing complexity. Simple firmgrounds and hardgrounds, which are comparatively ephemeral features, form the base of the hierarchy. Composite hardgrounds, reworked concretions, authigenic mineral crusts and monomictic intraformational conglomerates indicate more complex histories. Polymictic intraformational conglomerates, ironstones and phosphorites form the most complex discontinuity surfaces and condensed beds. Complexity of discontinuities is closely linked to depositional environments duration of sediment starvation and degree of reworking which in turn show a relationship to stratigraphic cyclicity. A model of cratonic sequence stratigraphy is generated by combining data on the complexity and lateral distribution of discontinuities in the context of facies successions. Lowstand, early transgressive and late transgressive systems tracts are representative of sea-level rise. Early and late transgressive systems tracts are separated by the maximum starvation surface (typically a polymictic intraformational conglomerate or condensed phosphorite), deposited during the peak rate of sea-level rise. Conversely the maximum flooding surface, representing the highest stand of sea level, is marked by little to no break in sedimentation. The highstand and falling stage systems tracts are deposited during relative sea-level fall. They are separated by the forced-regression surface, a thin discontinuity surface or condensed bed developed during the most rapid rate of sea-level fall. The lowest stand of sea level is marked by the sequence boundary. In subaerially exposed areas it is occasionally modified as a rockground or composite hardground.

Extreme Sea Level Rise Event Linked to 2009-10 AMOC Downturn

NASA Astrophysics Data System (ADS)

Yin, J.

2016-02-01

The coastal sea levels along the Northeast Coast of North America show significant year-to-year fluctuations in a general upward trend. Our analysis of long-term tide gauge records along the North American east coast identified an extreme sea-level rise (SLR) event during 2009-2010. Within this relatively brief two-year period, coastal sea levels north of New York City jumped by 100 mm. This magnitude of inter-annual SLR is unprecedented in the century-long tide gauge records, with statistical methods suggesting that it was a 1-in-850 year event. We show that this extreme SLR event was a combined effect of two physical factors. First, it was partly due to an observed 30% downturn of the Atlantic meridional overturning circulation (AMOC) during 2009-2010. This AMOC slowdown caused a significant decline of the dynamic sea level gradient across the Gulf Stream and North Atlantic Current, thereby imparting a rise in coastal sea level. The second contributing factor to the extreme SLR event was due to a significant negative North Atlantic Oscillation (NAO) index. The associated easterly or northeasterly wind anomalies acted to push ocean waters towards the Northeast Coast through the Ekman transport, resulting in further rise in coastal sea levels. Sea level pressure anomalies also contributed to the extreme SLR event through the inverse barometer effect. To project future extreme sea levels along the east coast of North America during the 21st century, we make use of a suite of climate/Earth system models developed at GFDL and other modeling centers. These models included typical CMIP5-class models, as well as the newer climate models GFDL CM2.5 and CM2.6 with eddying oceans. In response to the increase in greenhouse-gas concentrations, each of these models show a reduction in the AMOC. Given the observed connection between AMOC reduction and extreme coastal sea levels, the models thus project an increase in extreme SLR frequency on interannual time scales along the Northeast Coast of North America.

Holocene sea level, a semi-empirical contemplation

NASA Astrophysics Data System (ADS)

Bittermann, K.; Kemp, A.; Vermeer, M.; Rahmstorf, S.

2017-12-01

Holocene eustatic sea level from approximately -10,000-1800 CE was characterized by an increase of about 60m, with the rate progressively slowing down until sea level almost stabilizes between 500-1800 CE. Global and northern-hemisphere temperatures rose from the last glacial termination until the `Holocene Optimum'. From ­­there, up to the start of the recent anthropogenic rise, they almost steadily decline. How are the sea-level and temperature evolutions linked? We investigate this with semi-empirical sea-level models. We found that, due to the nature of Milankovitch forcing, northern-hemisphere temperature (we used the Greenland temperature by Vinther et al., 2009) is a better model driver than global mean temperature because the evolving mass of northern-hemisphere land ice was the dominant cause of Holocene global sea-level trends. The adjustment timescale for this contribution is 1200 years (900-1500 years; 90% confidence interval). To fit the observed sea-level history, the model requires a small additional constant rate (Bittermann 2016). This rate turns out to be of the same order of magnitude as reconstructions of Antarctic sea-level contributions (Briggs et al. 2014, Golledge et al. 2014). In reality this contribution is unlikely to be constant but rather has a dominant timescale that is large compared to the time considered. We thus propose that Holocene sea level can be described by a linear combination of a temperature driven rate, which becomes negative in the late Holocene (as Northern Hemisphere ice masses are diminished), and a positive, approximately constant term (possibly from Antarctica), which starts to dominate from the middle of the Holocene until the start of industrialization. Bibliography: Bittermann, K. 2016. Semi-empirical sea-level modelling. PhD Thesis University of Potsdam. Briggs, R.D., et al. 2014. A data-constrained large ensemble analysis of Antarctic evolution since the Eemian. Quaternary science reviews, 103, 91-115. Golledge, N.R., et al. 2014. Antarctic contribution to meltwater pulse 1A from reduced Southern Ocean overturning. Nature communications, 5, 5107. Vinther, B.M., et al. 2009. Holocene thinning of the Greenland ice sheet. Nature, 461(7262), 385-388.

A coupled geomorphic and ecological model of tidal marsh evolution.

PubMed

Kirwan, Matthew L; Murray, A Brad

2007-04-10

The evolution of tidal marsh platforms and interwoven channel networks cannot be addressed without treating the two-way interactions that link biological and physical processes. We have developed a 3D model of tidal marsh accretion and channel network development that couples physical sediment transport processes with vegetation biomass productivity. Tidal flow tends to cause erosion, whereas vegetation biomass, a function of bed surface depth below high tide, influences the rate of sediment deposition and slope-driven transport processes such as creek bank slumping. With a steady, moderate rise in sea level, the model builds a marsh platform and channel network with accretion rates everywhere equal to the rate of sea-level rise, meaning water depths and biological productivity remain temporally constant. An increase in the rate of sea-level rise, or a reduction in sediment supply, causes marsh-surface depths, biomass productivity, and deposition rates to increase while simultaneously causing the channel network to expand. Vegetation on the marsh platform can promote a metastable equilibrium where the platform maintains elevation relative to a rapidly rising sea level, although disturbance to vegetation could cause irreversible loss of marsh habitat.

Sea level anomaly in the North Atlantic and seas around Europe: Long-term variability and response to North Atlantic teleconnection patterns.

PubMed

Iglesias, Isabel; Lorenzo, M Nieves; Lázaro, Clara; Fernandes, M Joana; Bastos, Luísa

2017-12-31

Sea level anomaly (SLA), provided globally by satellite altimetry, is considered a valuable proxy for detecting long-term changes of the global ocean, as well as short-term and annual variations. In this manuscript, monthly sea level anomaly grids for the period 1993-2013 are used to characterise the North Atlantic Ocean variability at inter-annual timescales and its response to the North Atlantic main patterns of atmospheric circulation variability (North Atlantic Oscillation, Eastern Atlantic, Eastern Atlantic/Western Russia, Scandinavian and Polar/Eurasia) and main driven factors as sea level pressure, sea surface temperature and wind fields. SLA variability and long-term trends are analysed for the North Atlantic Ocean and several sub-regions (North, Baltic and Mediterranean and Black seas, Bay of Biscay extended to the west coast of the Iberian Peninsula, and the northern North Atlantic Ocean), depicting the SLA fluctuations at basin and sub-basin scales, aiming at representing the regions of maximum sea level variability. A significant correlation between SLA and the different phases of the teleconnection patterns due to the generated winds, sea level pressure and sea surface temperature anomalies, with a strong variability on temporal and spatial scales, has been identified. Long-term analysis reveals the existence of non-stationary inter-annual SLA fluctuations in terms of the temporal scale. Spectral density analysis has shown the existence of long-period signals in the SLA inter-annual component, with periods of ~10, 5, 4 and 2years, depending on the analysed sub-region. Also, a non-uniform increase in sea level since 1993 is identified for all sub-regions, with trend values between 2.05mm/year, for the Bay of Biscay region, and 3.98mm/year for the Baltic Sea (no GIA correction considered). The obtained results demonstrated a strong link between the atmospheric patterns and SLA, as well as strong long-period fluctuations of this variable in spatial and temporal scales. Copyright © 2017 Elsevier B.V. All rights reserved.

Ocean impact on decadal Atlantic climate variability revealed by sea-level observations.

PubMed

McCarthy, Gerard D; Haigh, Ivan D; Hirschi, Joël J-M; Grist, Jeremy P; Smeed, David A

2015-05-28

Decadal variability is a notable feature of the Atlantic Ocean and the climate of the regions it influences. Prominently, this is manifested in the Atlantic Multidecadal Oscillation (AMO) in sea surface temperatures. Positive (negative) phases of the AMO coincide with warmer (colder) North Atlantic sea surface temperatures. The AMO is linked with decadal climate fluctuations, such as Indian and Sahel rainfall, European summer precipitation, Atlantic hurricanes and variations in global temperatures. It is widely believed that ocean circulation drives the phase changes of the AMO by controlling ocean heat content. However, there are no direct observations of ocean circulation of sufficient length to support this, leading to questions about whether the AMO is controlled from another source. Here we provide observational evidence of the widely hypothesized link between ocean circulation and the AMO. We take a new approach, using sea level along the east coast of the United States to estimate ocean circulation on decadal timescales. We show that ocean circulation responds to the first mode of Atlantic atmospheric forcing, the North Atlantic Oscillation, through circulation changes between the subtropical and subpolar gyres--the intergyre region. These circulation changes affect the decadal evolution of North Atlantic heat content and, consequently, the phases of the AMO. The Atlantic overturning circulation is declining and the AMO is moving to a negative phase. This may offer a brief respite from the persistent rise of global temperatures, but in the coupled system we describe, there are compensating effects. In this case, the negative AMO is associated with a continued acceleration of sea-level rise along the northeast coast of the United States.

Constraining coastal change: A morpho-sedimentological concept to infer sea-level oscillation

NASA Astrophysics Data System (ADS)

Mauz, Barbara; Shen, Zhixiong

2016-04-01

One of the responders to Milankovitch-scale climate changes is sea level which, in turn, is a driver of coastal change. In literature, the sedimentary sequences representing the coastal change are often linked to high sea-level stands, to intermediate sea-level positions or to regressive shorelines. We note apparent contradictions that indicate a lack of concept and inconsistent usage of sea level-related terms. To overcome this, we combine an integrated morpho-sedimentological concept for microtidal, mid-latitudinal coasts with chronologies based on Bayesian statistics. The concept regards the coastal sedimentary system as a depositional complex consisting of shallow-marine, aeolian and alluvial facies. These facies are in juxtaposition and respond simultaneously to external forcing. Bayesian statistics constrains the timing of the sequence based on optical or radiocarbon ages. Here, we present the site Hergla located on the North African coast of the central Mediterranean Sea as a case study to illustrate how the approach helps eliminating contradictions. The site has been cited frequently for confirming the hypothesis of a global two peak sea-level highstand during the last interglacial (MIS 5e). The ~2 km cliff exposure at Hergla was surveyed, mapped, logged and sampled for further describing the sediments and their depositional environment through thin section and Bayesian modelling of optical ages. Using our concept based on sequence stratigraphy tools, the section is interpreted as representing a coastal barrier with two bounding surfaces in the succession. Both surfaces mark the falling sea level of, first, MIS 5e and, second, MIS 5a and hence bound the falling stage system tract of a forced regression. Part of the deposits between the two surfaces are pulled up onto the shoulder of a small rising horst and the associated tectonic event coincided with the MIS 5a sea-level rise enhancing locally the accommodation space for a second foreshore environment. Our presentation will provide theoretical background of the concept and critically discuss the global dataset for last interglacial sea-level oscillations using both the stratigraphic record and age distributions.

Uncertainties in Future Regional Sea Level Trends: How to Deal with the Internal Climate Variability?

NASA Astrophysics Data System (ADS)

Becker, M.; Karpytchev, M.; Hu, A.; Deser, C.; Lennartz-Sassinek, S.

2017-12-01

Today, the Climate models (CM) are the main tools for forecasting sea level rise (SLR) at global and regional scales. The CM forecasts are accompanied by inherent uncertainties. Understanding and reducing these uncertainties is becoming a matter of increasing urgency in order to provide robust estimates of SLR impact on coastal societies, which need sustainable choices of climate adaptation strategy. These CM uncertainties are linked to structural model formulation, initial conditions, emission scenario and internal variability. The internal variability is due to complex non-linear interactions within the Earth Climate System and can induce diverse quasi-periodic oscillatory modes and long-term persistences. To quantify the effects of internal variability, most studies used multi-model ensembles or sea level projections from a single model ran with perturbed initial conditions. However, large ensembles are not generally available, or too small, and computationally expensive. In this study, we use a power-law scaling of sea level fluctuations, as observed in many other geophysical signals and natural systems, which can be used to characterize the internal climate variability. From this specific statistical framework, we (1) use the pre-industrial control run of the National Center for Atmospheric Research Community Climate System Model (NCAR-CCSM) to test the robustness of the power-law scaling hypothesis; (2) employ the power-law statistics as a tool for assessing the spread of regional sea level projections due to the internal climate variability for the 21st century NCAR-CCSM; (3) compare the uncertainties in predicted sea level changes obtained from a NCAR-CCSM multi-member ensemble simulations with estimates derived for power-law processes, and (4) explore the sensitivity of spatial patterns of the internal variability and its effects on regional sea level projections.

Sensitivity of the overturning circulation of the Baltic Sea to climate change, a numerical experiment

NASA Astrophysics Data System (ADS)

Hordoir, Robinson; Höglund, Anders; Pemberton, Per; Schimanke, Semjon

2018-02-01

An ocean model covering the Baltic Sea area is forced by several climate scenarios for a period extending from 1961 to 2100. The Baltic Sea overturning circulation is then analyzed. The analysis shows that this circulation decreases between the end of the 20th century and the end of the 21st century, and that the decrease is amplified in the case of the strongest greenhouse gas emission scenarios, which corresponds with the highest warming cases. The reasons behind this decrease in overturning circulation are investigated. A strong increase of thermal stratification is noticed at the level of the Baltic Sea mixed layer. Based on buoyancy flux considerations, we demonstrate that the decrease in overturning circulation coincides with the increase of thermal stratification. Evidence shows that the underlying process is linked to a smaller erosion of the halocline due to a higher shielding, itself linked with a stronger and longer seasonal thermocline. This theory works if surface wind mixing is not taken into account directly in the computation of buoyancy fluxes.

Sea, Lake, and Overland Surge from Hurricanes (SLOSH) Inundation for Categories 2 and 4

EPA Pesticide Factsheets

The file geodatabase (fgdb) contains the Sea, Lake, and Overland Surge from Hurricanes (SLOSH) Maximum of Maximums (MOM) model for hurricane categories 2 and 4. The EPA Office of Research & Development (ORD) modified the original model from NOAA to fit the model parameters for the Buzzards Bay region. The models show storm surge extent for the Mattapoisett area and therefore the flooding area was reduced to the study area. Areas of flooding that were not connected to the main water body were removed. The files in the geodatabase are:Cat2_SLR0_Int_Feet_dissolve_Mattapoisett: Current Category 2 hurricane with 0 ft sea level riseCat4_SLR0_Int_Feet_dissolve_Mattapoisett: Current Category 4 hurricane with 0 ft sea level riseCat4_SLR4_Int_Feet_dissolve_Mattapoisett: Future Category 4 hurricane with 4 feet sea level riseThe features support the Weather Ready Mattapoisett story map, which can be accessed via the following link:https://epa.maps.arcgis.com/apps/MapJournal/index.html?appid=1ff4f1d28a254cb689334799d94b74e2

Statistical analysis of the El Niño-Southern Oscillation and sea-floor seismicity in the eastern tropical Pacific.

PubMed

Guillas, Serge; Day, Simon J; McGuire, B

2010-05-28

We present statistical evidence for a temporal link between variations in the El Niño-Southern Oscillation (ENSO) and the occurrence of earthquakes on the East Pacific Rise (EPR). We adopt a zero-inflated Poisson regression model to represent the relationship between the number of earthquakes in the Easter microplate on the EPR and ENSO (expressed using the southern oscillation index (SOI) for east Pacific sea-level pressure anomalies) from February 1973 to February 2009. We also examine the relationship between the numbers of earthquakes and sea levels, as retrieved by Topex/Poseidon from October 1992 to July 2002. We observe a significant (95% confidence level) positive influence of SOI on seismicity: positive SOI values trigger more earthquakes over the following 2 to 6 months than negative SOI values. There is a significant negative influence of absolute sea levels on seismicity (at 6 months lag). We propose that increased seismicity is associated with ENSO-driven sea-surface gradients (rising from east to west) in the equatorial Pacific, leading to a reduction in ocean-bottom pressure over the EPR by a few kilopascal. This relationship is opposite to reservoir-triggered seismicity and suggests that EPR fault activity may be triggered by plate flexure associated with the reduced pressure.

Revisiting sea level changes in the North Sea during the Anthropocene

NASA Astrophysics Data System (ADS)

Jensen, Jürgen; Dangendorf, Sönke; Wahl, Thomas; Niehüser, Sebastian

2016-04-01

The North Sea is one of the best instrumented ocean basins in the world. Here we revisit sea level changes in the North Sea region from tide gauges, satellite altimetry, hydrographic profiles and ocean reanalysis data from the beginning of the 19th century to present. This includes an overview of the sea level chapter of the North Sea Climate Change Assessment (NOSCCA) complemented by results from more recent investigations. The estimates of long-term changes from tide gauge records are significantly affected by vertical land motion (VLM), which is related to both the large-scale viscoelastic response of the solid earth to ice melting since the last deglaciation and local effects. Removing VLM (estimated from various data sources such as GPS, tide gauge minus altimetry and GIA) significantly reduces the spatial variability of long-term trends in the basin. VLM corrected tide gauge records suggest a transition from relatively moderate changes in the 19th century towards modern trends of roughly 1.5 mm/yr during the 20th century. Superimposed on the long-term changes there is a considerable inter-annual to multi-decadal variability. On inter-annual timescales this variability mainly reflects the barotropic response of the ocean to atmospheric forcing with the inverted barometer effect dominating along the UK and Norwegian coastlines and wind forcing controlling the southeastern part of the basin. The decadal variability is mostly remotely forced and dynamically linked to the North Atlantic via boundary waves in response to long-shore winds along the continental slope. These findings give valuable information about the required horizontal resolution of ocean models and the necessary boundary conditions and are therefore important for the dynamical downscaling of sea level projections for the North Sea coastlines.

Quaternary incised valleys in southern Brazil coastal zone

NASA Astrophysics Data System (ADS)

Weschenfelder, Jair; Baitelli, Ricardo; Corrêa, Iran C. S.; Bortolin, Eduardo C.; dos Santos, Cristiane B.

2014-11-01

High-resolution seismic records obtained in the Rio Grande do Sul coastal zone, southern Brazil, revealed that prominent valleys and channels developed in the area before the installation of actual coastal plain. Landwards, the paleoincisions can be linked with the present courses of the main river dissecting the area. Oceanwards, they can be linked with related features previously recognized in the continental shelf and slope by means of seismic and morphostructural studies. Based mainly on seismic, core data and geologic reasoning, it can be inferred that the coastal valleys were incised during forced regression events into the coastal prism deposited during previous sea level highstand events of the Quaternary. Seismic data has revealed paleovalleys up to 10 km wide and, in some places, infilled with up to 40 m thick of sediments. The results indicated two distinct periods of cut-and-fill events in the Patos Lagoon area. The filling of the younger incision system is mainly Holocene and its onset is related to the last main regressive event of the Pleistocene, when the sea level fell about 130 m below the actual position. The older incision and filling event is related to the previous regressive-transgressive events of the Middle and Late Pleistocene. The fluvial discharge fed delta systems on the shelf edge during the sea level lowstands. The subsequent transgressions drowned the incised drainage, infilling it and closing the inlets formerly connecting the coastal river to the ocean. The incised features may have played a significant role on the basin-margin architecture, facies distribution and accommodation space during the multitude of up and down sea level events of the Quaternary.

Relative sea-level change in the central Cyclades (Greece) since the Early Bronze Age

NASA Astrophysics Data System (ADS)

Draganits, E.

2012-04-01

The Aegean is a focus of important cultural achievements in Europe since the Neolithic period. The resulting abundance of archaeological remains, many of them below sea-level represent an advantageous area for the study of local relative sea-level change. We have carried out detailed mapping of Despotiko Island (SW of Antiparos) and its surrounding. Despotiko is situated almost exactly in the center of the Cyclades (as defined nowadays), more so than Delos, and therefore is very well suited for sea-level studies of the Cyclades. This beneficial location, combined with a spacious and protected bay, additionally may explain its former importance as stepping-stone in the Aegean Sea. The island is uninhabited at present, but Early Bronze Age settlement sites and graveyards as well as a large Archaic sanctuary proof its former importance. The sanctuary is situated on a gently northeast dipping slope in the northeast part of Despotiko, in range of sight of the Órmos Despotiko. Since 1997 large parts of this important sanctuary have been excavated during several excavation campaigns. Tectonically, Despotiko, Antiparos and Paros, belong to the Attic-Cycladic Crystalline of the Central Hellenides, a stack of metamorphic tectonic nappes, mainly comprising variable types of gneiss, schist, marble and amphibolite, and tectonic slices of unmetamorphosed sediments on top, separated by low-angle normal faults from the metamorphic units below. Submerged archaeological structures at the sea bottom of the Órmos Despotiko, a Classical marble inscription from the sanctuary and partly submerged agriculture trenches at the east coast Despotiko, indicate that the relative sea-level in this area was some 3 m lower during the Early Bronze Age and still more than 1 m lower during Classical time. These values of relative sea-level rise indicate a subsidence component additional to the global sea-level rise in the investigated time period. Neglecting possible vertical tectonic movements and by means of the present sea floor bathymetric configuration the sea level reconstruction would imply the existence of an isthmus between Despotiko, Kimitiri and Antiparos linking the islands at least until Classical time. The existence of an isthmus would not only have altered the communication paths between the two islands, but Despotiko Bay would also have been even better protected from northwest winds than at present. The sea-level values from Despotiko are compared with other recent sea-level reconstructions on other islands of the Cyclades.

Linking micro- and macroevolutionary perspectives to evaluate the role of Quaternary sea-level oscillations in island diversification.

PubMed

Papadopoulou, Anna; Knowles, L Lacey

2017-12-01

With shifts in island area, isolation, and cycles of island fusion-fission, the role of Quaternary sea-level oscillations as drivers of diversification is complex and not well understood. Here, we conduct parallel comparisons of population and species divergence between two island areas of equivalent size that have been affected differently by sea-level oscillations, with the aim to understand the micro- and macroevolutionary dynamics associated with sea-level change. Using genome-wide datasets for a clade of seven Amphiacusta ground cricket species endemic to the Puerto Rico Bank (PRB), we found consistently deeper interspecific divergences and higher population differentiation across the unfragmented Western PRB, in comparison to the currently fragmented Eastern PRB that has experienced extreme changes in island area and connectivity during the Quaternary. We evaluate alternative hypotheses related to the microevolutionary processes (population splitting, extinction, and merging) that regulate the frequency of completed speciation across the PRB. Our results suggest that under certain combinations of archipelago characteristics and taxon traits, the repeated changes in island area and connectivity may create an opposite effect to the hypothesized "species pump" action of oscillating sea levels. Our study highlights how a microevolutionary perspective can complement current macroecological work on the Quaternary dynamics of island biodiversity. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

The Influence of the Terrestrial Reference Frame on Studies of Sea Level Change

NASA Astrophysics Data System (ADS)

Nerem, R. S.; Bar-Sever, Y. E.; Haines, B. J.; Desai, S.; Heflin, M. B.

2015-12-01

The terrestrial reference frame (TRF) provides the foundation for the accurate monitoring of sea level using both ground-based (tide gauges) and space-based (satellite altimetry) techniques. For the latter, tide gauges are also used to monitor drifts in the satellite instruments over time. The accuracy of the terrestrial reference frame (TRF) is thus a critical component for both types of sea level measurements. The TRF is central to the formation of geocentric sea-surface height (SSH) measurements from satellite altimeter data. The computed satellite orbits are linked to a particular TRF via the assumed locations of the ground-based tracking systems. The manner in which TRF errors are expressed in the orbit solution (and thus SSH) is not straightforward, and depends on the models of the forces underlying the satellite's motion. We discuss this relationship, and provide examples of the systematic TRF-induced errors in the altimeter derived sea-level record. The TRF is also crucial to the interpretation of tide-gauge measurements, as it enables the separation of vertical land motion from volumetric changes in the water level. TRF errors affect tide gauge measurements through GNSS estimates of the vertical land motion at each tide gauge. This talk will discuss the current accuracy of the TRF and how errors in the TRF impact both satellite altimeter and tide gauge sea level measurements. We will also discuss simulations of how the proposed Geodetic Reference Antenna in SPace (GRASP) satellite mission could reduce these errors and revolutionize how reference frames are computed in general.

Development of new geoinformation methods for modelling and prediction of sea level change over different timescales - overview of the project

NASA Astrophysics Data System (ADS)

Niedzielski, T.; Włosińska, M.; Miziński, B.; Hewelt, M.; Migoń, P.; Kosek, W.; Priede, I. G.

2012-04-01

The poster aims to provide a broad scientific audience with a general overview of a project on sea level change modelling and prediction that has just commenced at the University of Wrocław, Poland. The initiative that the project fits, called the Homing Plus programme, is organised by the Foundation for Polish Science and financially supported by the European Union through the European Regional Development Fund and the Innovative Economy Programme. There are two key research objectives of the project that complement each other. First, emphasis is put on modern satellite altimetric gridded time series from the Archiving, Validation and Interpretation of Satellite Oceanographic data (AVISO) repository. Daily sea level anomaly maps, access to which in near-real time is courtesy of AVISO, are being steadily downloaded every day to our local server in Wroclaw, Poland. These data will be processed within a general framework of modelling and prediction of sea level change in short, medium and long term. Secondly, sea level change over geological time is scrutinised in order to cover very long time scales that go far beyond a history of altimetric and tide-gauge measurements. The aforementioned approaches comprise a few tasks that aim to solve the following detailed problems. Within the first one, our objective is to seek spatio-temporal dependencies in the gridded sea level anomaly time series. Subsequently, predictions that make use of such cross-correlations shall be derived, and near-real time service for automatic update with validation will be implemented. Concurrently, (i.e. apart from spatio-temporal dependencies and their use in the process of forecasting variable sea level topography), threshold models shall be utilised for predicting the El Niño/Southern Oscillation (ENSO) signal that is normally present in sea level anomaly time series of the equatorial Pacific. Within the second approach, however, the entirely different methods are proposed. Links between sea floor topography and sea level change will be quantified, with a particular emphasis placed on the hypsometric curve and its semi-empirical modelling. Very long-term projections of sea level change will be based on testing statistical hypotheses and trend analyses, but input data will be calculated from theoretical models. Slightly apart from this topic is a notion of nonlinearity that was earlier shown to be present in gridded sea level anomaly time series. Thus, the list of intermediate tasks concludes with a need for a comprehensive interpretation of such irregularities.

Sealife: a semantic grid browser for the life sciences applied to the study of infectious diseases.

PubMed

Schroeder, Michael; Burger, Albert; Kostkova, Patty; Stevens, Robert; Habermann, Bianca; Dieng-Kuntz, Rose

2006-01-01

The objective of Sealife is the conception and realisation of a semantic Grid browser for the life sciences, which will link the existing Web to the currently emerging eScience infrastructure. The SeaLife Browser will allow users to automatically link a host of Web servers and Web/Grid services to the Web content he/she is visiting. This will be accomplished using eScience's growing number of Web/Grid Services and its XML-based standards and ontologies. The browser will identify terms in the pages being browsed through the background knowledge held in ontologies. Through the use of Semantic Hyperlinks, which link identified ontology terms to servers and services, the SeaLife Browser will offer a new dimension of context-based information integration. In this paper, we give an overview over the different components of the browser and their interplay. This SeaLife Browser will be demonstrated within three application scenarios in evidence-based medicine, literature & patent mining, and molecular biology, all relating to the study of infectious diseases. The three applications vertically integrate the molecule/cell, the tissue/organ and the patient/population level by covering the analysis of high-throughput screening data for endocytosis (the molecular entry pathway into the cell), the expression of proteins in the spatial context of tissue and organs, and a high-level library on infectious diseases designed for clinicians and their patients. For more information see http://www.biote.ctu-dresden.de/sealife.

Diffuse attenuation coefficient for downwelling irradiance at 490 nm and its spectral characteristics in the Black Sea upper layer: modeling, in situ measurements and ocean color data

NASA Astrophysics Data System (ADS)

Suslin, V. V.; Slabakova, V. K.; Churilova, T. Ya.

2017-11-01

Vertical diffuse attenuation coefficient, Kd(490), is one of the key parameter required for water quality modeling, hydrodynamic and biological processes in the sea. We showed that standard level-2 product of Kd(490) was underestimated in comparison with Kd(490) values simulated by the regional model during the diatom bloom in the Black Sea. Using data of SeaWiFS, MERIS and MODIS color scanners, a regional relationship between the model value of Kd(490) and the ratio of remote sensing reflectances has been obtained. Based on the bulgarian argo-bio-buoy dataset, the relationship between the attenuation coefficient of photosynthetically active radiation and attenuation coefficient at a wavelength of 490 nm is obtained. The simplified model, below as the S-model, of the diffuse attenuation coefficient spectrum for downwelling irradiance in the Black Sea upper layer is described. As a consequence of the S-model, the link between the depth of the euphotic zone and Kd(490) has been obtained. It is shown that the Kd(490) values, retrieved from ocean color data with using the regional link and from argo-bio-buoy measurements at depths between 6-20 m, are close to each other.

Variability of hydrological extreme events in East Asia and their dynamical control: a comparison between observations and two high-resolution global climate models

NASA Astrophysics Data System (ADS)

Freychet, N.; Duchez, A.; Wu, C.-H.; Chen, C.-A.; Hsu, H.-H.; Hirschi, J.; Forryan, A.; Sinha, B.; New, A. L.; Graham, T.; Andrews, M. B.; Tu, C.-Y.; Lin, S.-J.

2017-02-01

This work investigates the variability of extreme weather events (drought spells, DS15, and daily heavy rainfall, PR99) over East Asia. It particularly focuses on the large scale atmospheric circulation associated with high levels of the occurrence of these extreme events. Two observational datasets (APHRODITE and PERSIANN) are compared with two high-resolution global climate models (HiRAM and HadGEM3-GC2) and an ensemble of other lower resolution climate models from CMIP5. We first evaluate the performance of the high resolution models. They both exhibit good skill in reproducing extreme events, especially when compared with CMIP5 results. Significant differences exist between the two observational datasets, highlighting the difficulty of having a clear estimate of extreme events. The link between the variability of the extremes and the large scale circulation is investigated, on monthly and interannual timescales, using composite and correlation analyses. Both extreme indices DS15 and PR99 are significantly linked to the low level wind intensity over East Asia, i.e. the monsoon circulation. It is also found that DS15 events are strongly linked to the surface temperature over the Siberian region and to the land-sea pressure contrast, while PR99 events are linked to the sea surface temperature anomalies over the West North Pacific. These results illustrate the importance of the monsoon circulation on extremes over East Asia. The dependencies on of the surface temperature over the continent and the sea surface temperature raise the question as to what extent they could affect the occurrence of extremes over tropical regions in future projections.

Magmatic pulse driven by sea-level changes associated with the Messinian salinity crisis

PubMed Central

Sternai, Pietro; Caricchi, Luca; Garcia-Castellanos, Daniel; Jolivet, Laurent; Sheldrake, Tom E.; Castelltort, Sébastien

2017-01-01

Between 5 and 6 million years ago, during the so-called Messinian salinity crisis, the Mediterranean basin became a giant salt repository. The possibility of abrupt and kilometre-scale sea-level changes during this extreme event is debated. Messinian evaporites could signify either deep- or shallow-marine deposits, and ubiquitous erosional surfaces could indicate either subaerial or submarine features. Significant and fast reductions in sea level unload the lithosphere, which can increase the production and eruption of magma. Here we calculate variations in surface load associated with the Messinian salinity crisis and compile the available time constraints for pan-Mediterranean magmatism. We show that scenarios involving a kilometre-scale drawdown of sea level imply a phase of net overall lithospheric unloading at a time that appears synchronous with a magmatic pulse from the pan-Mediterranean igneous provinces. We verify the viability of a mechanistic link between unloading and magmatism using numerical modelling of decompression partial mantle melting and dike formation in response to surface load variations. We conclude that the Mediterranean magmatic record provides an independent validation of the controversial kilometre-scale evaporative drawdown and sheds new light on the sensitivity of magmatic systems to the surface forcing. PMID:29081834

Understanding Climate Change and Sea Level: A Case Study of Middle School Student Comprehension and An Evaluation of Tide Gauges off the Panama Canal in the Pacific Ocean and Caribbean Sea

NASA Astrophysics Data System (ADS)

Millan-Otoya, Juan C.

The present study had two main objectives. The first was to determine the degree of understanding of climate change, sea level and sea level rise among middle school students. Combining open-ended questions with likert-scaled questions, we identified student conceptions on these topics in 86 students from 7th and 8th grades during 2012 and 2013 before and after implementing a Curriculum Unit (CU). Additional information was obtained by adding drawings to the open-ended questions during the second year to gauge how student conceptions varied from a verbal and a visual perspective. Misconceptions were identified both pre- and post-CU among all the topics taught. Students commonly used climate and climate change as synonyms, sea level was often defined as water depth, and several students failed to understand the complexities that determine changes in sea level due to wind, tides, and changes in sea surface temperature. In general, 8th grade students demonstrated a better understanding of these topics, as reflected in fewer apparent misconceptions after the CU. No previous study had reported such improvement. This showed the value of implementing short lessons. Using Piaget's theories on cognitive development, the differences between 7th and 8th grade students reflect a transition to a more mature level which allowed students to comprehend more complex concepts that included multiple variables. The second objective was to determine if the frequency of sea level maxima not associated with tides over the last 100 years increased in two tide gauges located on the two extremes of the Panama canal, i.e. Balboa in the Pacific Ocean and Cristobal in the Caribbean Sea. These records were compared to time series of regional sea surface temperature, wind speed, atmospheric pressure, and El Nino-Southern Oscillation (ENSO), to determine if these played a role as physical drivers of sea level at either location. Neither record showed an increase in the frequency of sea level maxima events. No parameter analyzed explained variability in sea level maxima in Cristobal. There was a significant correlation between the zonal component of the wind and sea level at Balboa for the early record (r=0.153; p-value<0.05), but for the most part the p-values did not support the hypothesis of a correlation. Similarly, sea surface temperature had an effect on sea level at Balboa, but the null hypothesis that there is no correlation could not be rejected (p-value>0.05). There was a clear relationship between sea level maxima and ENSO. 70% of the years with higher counts of higher sea level events corresponded to El Nino years. A randomization test with 1000 iterations, shuffling the El Nino years, showed most of these randomizations grouped between 14-35% of the events occurring during a randomized El Nino year. In no iteration did the percentage of events that occurred during El Nino years rise above 65%. The correlation with zonal wind and the probable correlation with sea surface temperature can be linked via ENSO, since ENSO is associated with changes in the strength of the Trade Winds and positive anomalies in the sea surface temperature of the tropical Pacific Ocean.

Climate Framework for Uncertainty, Negotiation, and Distribution (FUND)

EPA Science Inventory

FUND is an Integrated Assessment model that links socioeconomic, technology, and emission scenarios with atmospheric chemistry, climate dynamics, sea level rise, and the resulting economic impacts. The model runs in time-steps of one year from 1950 to 2300, and distinguishes 16 m...

Molecular architecture and function of the SEA complex, a modulator of the TORC1 pathway.

PubMed

Algret, Romain; Fernandez-Martinez, Javier; Shi, Yi; Kim, Seung Joong; Pellarin, Riccardo; Cimermancic, Peter; Cochet, Emilie; Sali, Andrej; Chait, Brian T; Rout, Michael P; Dokudovskaya, Svetlana

2014-11-01

The TORC1 signaling pathway plays a major role in the control of cell growth and response to stress. Here we demonstrate that the SEA complex physically interacts with TORC1 and is an important regulator of its activity. During nitrogen starvation, deletions of SEA complex components lead to Tor1 kinase delocalization, defects in autophagy, and vacuolar fragmentation. TORC1 inactivation, via nitrogen deprivation or rapamycin treatment, changes cellular levels of SEA complex members. We used affinity purification and chemical cross-linking to generate the data for an integrative structure modeling approach, which produced a well-defined molecular architecture of the SEA complex and showed that the SEA complex comprises two regions that are structurally and functionally distinct. The SEA complex emerges as a platform that can coordinate both structural and enzymatic activities necessary for the effective functioning of the TORC1 pathway. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

SeaWIFS Postlaunch Technical Report Series. Volume 13; The SeaWiFS Photometer Revision for Incident Surface Measurement (SeaPRISM) Field Commissioning

NASA Technical Reports Server (NTRS)

Hooker, Stanford B. (Editor); Zibordi, Giuseppe; Berthon, Jean-Francois; Bailey, Sean W.; Pietras, Christophe M.; Firestone, Elaine R. (Editor)

2000-01-01

This report documents the scientific activities that took place at the Acqua Alta Oceanographic Tower (AAOT) in the northern Adriatic Sea off the coast of Italy from 2-6 August 1999. The ultimate objective of the field campaign was to evaluate the capabilities of a new instrument called the SeaWiFS Photometer Revision for Incident Surface Measurements (SeaPRISM). SeaPRISM is based on a CE-318 sun photometer made by CIMEL Electronique (Paris, France). The CE-318 is an automated, robotic system which measures the direct sun irradiance plus the sky radiance in the sun plane and in the almucantar plane. The data are transmitted over a satellite link, and this remote operation capability has made the device very useful for atmospheric measurements. The revision to the CE-318 that makes the instrument potentially useful for SeaWiFS calibration and validation activities is to include a capability for measuring the radiance leaving the sea surface in wavelengths suitable for the determination of chlorophyll a concentration. The initial evaluation of this new capability involved above- and in-water measurement protocols. An intercomparison of the water-leaving radiances derived from SeaPRISM and an in-water system showed the overall spectral agreement was approximately 8.6%, but the blue-green channels intercompared at the 5% level. A blue-green band ratio comparison was at the 4% level.

Dynamic Topography and Sea Level Anomalies of the Southern Ocean: Variability and Teleconnections

NASA Astrophysics Data System (ADS)

Armitage, Thomas W. K.; Kwok, Ron; Thompson, Andrew F.; Cunningham, Glenn

2018-01-01

This study combines sea surface height (SSH) estimates of the ice-covered Southern Ocean with conventional open-ocean SSH estimates from CryoSat-2 to produce monthly composites of dynamic ocean topography (DOT) and sea level anomaly (SLA) on a 50 km grid spanning 2011-2016. This data set reveals the full Southern Ocean SSH seasonal cycle for the first time; there is an antiphase relationship between sea level on the Antarctic continental shelf and the deeper basins, with coastal SSH highest in autumn and lowest in spring. As a result of this pattern of seasonal SSH variability, the barotropic component of the Antarctic Slope Current (ASC) has speeds that are regionally up to twice as fast in the autumn. Month-to-month circulation variability of the Ross and Weddell Gyres is strongly influenced by the local wind field, and is correlated with the local wind curl (Ross: -0.58; Weddell: -0.67). SSH variability is linked to both the Southern Oscillation and the Southern Annular Mode, dominant modes of southern hemisphere climate variability. In particular, during the strong 2015-2016 El Niño, a sustained negative coastal SLA of up to -6 cm, implying a weakening of the ASC, was observed in the Pacific sector of the Southern Ocean. The ability to examine sea level variability in the seasonally ice-covered regions of the Southern Ocean—climatically important regions with an acute sparsity of data—makes this new merged sea level record of particular interest to the Southern Ocean oceanography and glaciology communities.

Mid-Ocean Ridge Melt Supply and Glacial Cycles: A 3D EPR Study of Crustal Thickness, Layer 2A, and Bathymetry

NASA Astrophysics Data System (ADS)

Boulahanis, B.; Aghaei, O.; Carbotte, S. M.; Huybers, P. J.; Langmuir, C. H.; Nedimovic, M. R.; Carton, H. D.; Canales, J. P.

2017-12-01

Recent studies suggest that eustatic sea level fluctuations induced by glacial cycles in the Pleistocene may influence mantle-melting and volcanic eruptions at mid-ocean ridges (MOR), with models predicting variation in oceanic crustal thickness linked to sea level change. Previous analyses of seafloor bathymetry as a proxy for crustal thickness show significant spectral energy at frequencies linked to Milankovitch cycles of 1/23, 1/41, and 1/100 ky-1, however the effects of faulting in seafloor relief and its spectral characteristics are difficult to separate from climatic signals. Here we investigate the hypothesis of climate driven periodicity in MOR magmatism through spectral analysis, time series comparisons, and statistical characterization of bathymetry data, seismic layer 2A thickness (as a proxy for extrusive volcanism), and seafloor-to-Moho thickness (as a proxy for total magma production). We utilize information from a three-dimensional multichannel seismic study of the East Pacific Rise and its flanks from 9°36`N to 9°57`N. We compare these datasets to the paleoclimate "LR04" benthic δ18O stack. The seismic dataset covers 770 km2 and provides resolution of Moho for 92% of the imaged region. This is the only existing high-resolution 3-D image across oceanic crust, making it ideal for assessing the possibility that glacial cycles modulate magma supply at fast spreading MORs. The layer 2A grid extends 9 km (170 ky) from the ridge axis, while Moho imaging extends to a maximum of 16 km (310 ky). Initial results from the East Pacific Rise show a relationship between sea level and both crustal thickness and sea floor depth, consistent with the hypothesis that magma supply to MORs may be modulated by glacial cycles. Analysis of crustal thickness and bathymetry data reveals spectral peaks at Milankovitch frequencies of 1/100 ky-1 and 1/41 ky-1 where datasets extend sufficiently far from the ridge. The layer 2A grid does not extend sufficiently far from the ridge to be conclusive. Correlations between sea level and crustal thickness suggest a lag of 65 ky between sea level forcing and crustal thickness response. A further lag of 25 ky is observed between crustal thickness variations and seafloor depth change, which we attribute to the finite width of the crustal formation zone.

Asynchronous Patterns of East Asian Monsoon Climate Proxies during the Past 28 000 Years

NASA Astrophysics Data System (ADS)

Ruan, Y.; Li, L.; Jia, G.; He, J.; Dong, L.; Ma, X.; Shi, J.; Wang, H.

2015-12-01

The monsoon system serves as a "bridge" in the atmosphere; it connects the circulation between high and low latitudes, influencing the most densely populated regions on Earth. However, what role it played in the geological history is still elusive despite its significance. The climate of South China Sea and the ambient land masses are dominated by the East Asian monsoon, composed of the temperature-cooling East Asian winter monsoon (EAWM) and the rain-bearing East Asian summer monsoon (EASM). In this study, high-resolution sea surface temperature (SST), terrestrial input and humidity changes since ~28 ka were reconstructed based on alkenones and long chain n-alkanes records in core MD12-3428 in northern South China Sea. Our results demonstrated complex and dynamic paleoclimatic situations since the last glacial superimposed on the overall glacial-interglacial trend. During the last deglacial, the rising of the sea level can be dated back to 17 ka and ended at ~12 ka, according to the gradual decrease of long chain n-alkanes concentrations. However, the SST warming began at ~15 ka (~2 000 years after the initial sea level uplift) and achieved a relatively stable state in mid-Holocene (~6 000 years after the sea level stablization). The humidity varibility linked with EASM based on C31/C27 and ACL record indicated highly humid conditions within the Bølling/Allerød (B/A) period, followed by a rapid drying towards the glacial level during Younger Dryas (YD). EASM gradually strengthened after YD when the sea level had run up to almost the present state, and weakened after ~6 ka when sea level and SST both reached the plateau. These large fluctuations of C31/C27 and ACL implied that humidity was more sensitive to climate events since the last deglacial when compared with SST and sea level. The asynchronous patterns of East Asian monsoon climate proxies in the present work indicated the complex heat transport and atmospheric circulation between low and high latitudes.

SeaWiFS Technical Report Series. Volume 39; SeaWiFS Calibration Topics

NASA Technical Reports Server (NTRS)

Hooker, Stanford B. (Editor); Firestone, Elaine R. (Editor); Barnes, Robert A.; Yeh, Eueng-nan; Eplee, Robert E.

1996-01-01

For Earth-observing satellite instruments, it was standard to consider each instrument band to have a spectral response that is infinitely narrow, i.e., to have a response from a single wavelength. The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) bands, however, have nominal spectral bandwidths of 20 and 40nm. These bandwidths affect the SeaWiFS measurements on orbit. The effects are also linked to the manner in which the instrument was calibrated and to the spectral shape of the radiance that SeaWiFS views. Currently, SeaWiFS is calibrated such that the digital counts from each instrument band are linked to the Earth-exiting radiance at an individual center wavelength. Before launch, SeaWiFS will be recalibrated so that the digital counts from each band will be linked to the Earth-exiting radiance integrated over the spectral response of that band. In this technical memorandum, the effects of the instrument calibration and the source spectral shape on SeaWiFS measurements, including the in-band and out-of-band responses, and the center wavelengths are discussed.

Sea ice and pollution-modulated changes in Greenland ice core methanesulfonate and bromine

NASA Astrophysics Data System (ADS)

Maselli, Olivia J.; Chellman, Nathan J.; Grieman, Mackenzie; Layman, Lawrence; McConnell, Joseph R.; Pasteris, Daniel; Rhodes, Rachael H.; Saltzman, Eric; Sigl, Michael

2017-01-01

Reconstruction of past changes in Arctic sea ice extent may be critical for understanding its future evolution. Methanesulfonate (MSA) and bromine concentrations preserved in ice cores have both been proposed as indicators of past sea ice conditions. In this study, two ice cores from central and north-eastern Greenland were analysed at sub-annual resolution for MSA (CH3SO3H) and bromine, covering the time period 1750-2010. We examine correlations between ice core MSA and the HadISST1 ICE sea ice dataset and consult back trajectories to infer the likely source regions. A strong correlation between the low-frequency MSA and bromine records during pre-industrial times indicates that both chemical species are likely linked to processes occurring on or near sea ice in the same source regions. The positive correlation between ice core MSA and bromine persists until the mid-20th century, when the acidity of Greenland ice begins to increase markedly due to increased fossil fuel emissions. After that time, MSA levels decrease as a result of declining sea ice extent but bromine levels increase. We consider several possible explanations and ultimately suggest that increased acidity, specifically nitric acid, of snow on sea ice stimulates the release of reactive Br from sea ice, resulting in increased transport and deposition on the Greenland ice sheet.

Coral mortality induced by the 2015-2016 El-Niño in Indonesia: the effect of rapid sea level fall

NASA Astrophysics Data System (ADS)

Elvan Ampou, Eghbert; Johan, Ofri; Menkes, Christophe E.; Niño, Fernando; Birol, Florence; Ouillon, Sylvain; Andréfouët, Serge

2017-02-01

The 2015-2016 El-Niño and related ocean warming has generated significant coral bleaching and mortality worldwide. In Indonesia, the first signs of bleaching were reported in April 2016. However, this El Niño has impacted Indonesian coral reefs since 2015 through a different process than temperature-induced bleaching. In September 2015, altimetry data show that sea level was at its lowest in the past 12 years, affecting corals living in the bathymetric range exposed to unusual emersion. In March 2016, Bunaken Island (North Sulawesi) displayed up to 85 % mortality on reef flats dominated by Porites, Heliopora and Goniastrea corals with differential mortality rates by coral genus. Almost all reef flats showed evidence of mortality, representing 30 % of Bunaken reefs. For reef flat communities which were living at a depth close to the pre-El Niño mean low sea level, the fall induced substantial mortality likely by higher daily aerial exposure, at least during low tide periods. Altimetry data were used to map sea level fall throughout Indonesia, suggesting that similar mortality could be widespread for shallow reef flat communities, which accounts for a vast percent of the total extent of coral reefs in Indonesia. The altimetry historical records also suggest that such an event was not unique in the past two decades, therefore rapid sea level fall could be more important in the dynamics and resilience of Indonesian reef flat communities than previously thought. The clear link between mortality and sea level fall also calls for a refinement of the hierarchy of El Niño impacts and their consequences on coral reefs.

Improvement of Global and Regional Mean Sea Level Trends Derived from all Altimetry Missions.

NASA Astrophysics Data System (ADS)

Ablain, Michael; Benveniste, Jérôme; Faugere, Yannice; Larnicol, Gilles; Cazenave, Anny; Johannessen, Johnny A.; Stammer, Detlef; Timms, Gary

2012-07-01

The global mean sea level (GMSL) has been calculated on a continual basis since January 1993 using data from satellite altimetry missions. The global mean sea level (MSL) deduced from TOPEX/Poseidon, Jason-1 and Jason-2 is increasing with a global trend of 3.2 mm from 1993 to 2010 applying the post glacial rebound (MSL Aviso website http://www.jason.oceanobs.com/msl). Besides, the regional sea level trends bring out an inhomogeneous repartition of the ocean elevation with local MSL slopes ranging from +/- 8 mm/year. A study published in 2009 [Ablain et al., 2009] has shown that the global MSL trend uncertainty was estimated at +/-0.6 mm/year with a confidence interval of 90%. The main sources of errors at global and regional scales are due to the orbit calculation and the wet troposphere correction. But others sea-level components have also a significant impact on the long-term stability of MSL as for instance the stability of instrumental parameters and the atmospheric corrections. Thanks to recent studies performed in Sea Level Essential Climate Variable Project in the frame of the Climate Change Initiative, an ESA Programme, in addition to activities performed within the SALP/CNES, strong improvements have been provided for the estimation of the global and regional MSL trends. In this paper, we propose to describe them; they concern the orbit calculation thanks to new gravity fields, the atmospheric corrections thanks to ERA-interim reanalyses, the wet troposphere corrections thanks to the stability improvement, and also empirical corrections allowing us to link regional time series together better. These improvements are described at global and regional scale for all the altimetry missions.

Interactions of ice sheet evolution, sea level and GIA in a region of complex Earth structure

NASA Astrophysics Data System (ADS)

Gomez, N. A.; Chan, N. H.; Latychev, K.; Pollard, D.; Powell, E. M.

2017-12-01

Constraining glacial isostatic adjustment (GIA) is challenging in Antarctica, where the solid Earth deformation, sea level changes and ice dynamics are strongly linked on all timescales. Furthermore, Earth structure beneath the Antarctic Ice Sheet is characterized by significant lateral variability. A stable, thick craton exists in the east, while the west is underlain by a large continental rift system, with a relatively thin lithosphere and hot, low viscosity asthenosphere, as indicated by high resolution seismic tomography. This implies that in parts of the West Antarctic, the Earth's mantle may respond to surface loading on shorter than average (centennial, or even decadal) timescales. Accounting for lateral variations in viscoelastic Earth structure alters the timing and geometry of load-induced Earth deformation, which in turn impacts the timing and extent of the ice-sheet retreat via a sea-level feedback, as well as predictions of relative sea-level change and GIA. We explore the impact of laterally varying Earth structure on ice-sheet evolution, sea level change and Earth deformation in the Antarctic region since the Last Glacial Maximum using a newly developed coupled ice sheet - sea level model that incorporates 3-D variations in lithospheric thickness and mantle viscosity derived from recent seismic tomographic datasets. Our results focus on identifying the regions and time periods in which the incorporation of 3-D Earth structure is critical for accurate predictions of ice sheet evolution and interpretation of geological and geodetic observations. We also investigate the sensitivity to the regional Earth structure of the relative contributions to modern GIA predictions of Last Deglacial and more recent Holocene ice cover changes.

Tropical West Pacific Imagery - Satellite Products and Services

Science.gov Websites

Division/Office of Satellite and Product Operations Skip Navigation Link NESDIS banner image Information Service Home Page Default Office of Satellite and Product Operations banner image and link to OSPO MIRS MSPPS Ocean -- Coral Bleaching -- Ocean Color -- Sea/Lake Ice -- Sea Surface Height -- Sea Surface

Healthy coral reefs may assure coastal protection in face of climate change related sea level rise

NASA Astrophysics Data System (ADS)

Harris, D. L.; Rovere, A.; Parravicini, V.; Casella, E.; Canavesio, R.; Collin, A.

2016-12-01

Coral reefs are diverse ecosystems that support millions of people worldwide providing crucial services, of which, coastal protection is one of the most relevant. The efficiency of coral reefs in protecting coastlines and dissipating waves is directly linked to the cover of living corals and three dimensional reef structural complexity. Climate change and human impacts are leading to severe global reductions in live coral cover, posing serious concerns regarding the capacity of degraded reef systems in protecting tropical coastal regions. Although it is known that the loss of structurally complex reefs may lead to greater erosion of coastlines, this process has rarely been quantified and it is still unknown whether the maintenance of healthy reefs through conservation will be enough to guarantee coastal protection during rising sea levels. We show that a significant loss of wave dissipation and a subsequent increase in back-reef wave height (up to 5 times present wave height) could occur even at present sea level if living corals are lost and reef structural complexity is reduced. Yet we also show that healthy reefs, measured by structural complexity and efficiency of vertical reef accretion, may maintain their present capacity of wave dissipation even under rising sea levels. Our results indicate that the health of coral reefs and not sea level rise will be the major determinant of the coastal protection services provided by coral reefs and calls for investments into coral reef conservation to ensure the future protection of tropical coastal communities.

Saltwater Intrusion: Climate change mitigation or just water resources management?

NASA Astrophysics Data System (ADS)

Ferguson, G. A.; Gleeson, T.

2011-12-01

Climate change and population growth are expected to substantially increase the vulnerability of global water resources throughout the 21st century. Coastal groundwater systems are a nexus of the world's changing oceanic and hydrologic systems and a critical resource for the over one billion people living in coastal areas as well as for terrestrial and offshore ecosystems. Synthesis studies and detailed simulations predict that rising sea levels could negatively impact coastal aquifers by causing saltwater to intrude landward within coastal aquifers or by saltwater inundation of coastal regions. Saltwater intrusion caused by excessive extraction is already impacting entire island nations and globally in diverse regions such as Nile River delta in Egypt, Queensland, Australia and Long Island, USA. However, the vulnerability of coastal aquifers to sea level rise and excessive extraction has not been systematically compared. Here we show that coastal aquifers are much more vulnerable to groundwater extraction than predicted sea level rise in wide-ranging hydrogeologic conditions and population densities. Low lying areas with small hydraulic gradients are more sensitive to climate change but a review of existing coastal aquifer indicates that saltwater intrusion problems are more likely to arise where water demand is high. No cases studies were found linking saltwater intrusion to sea level rise during the past century. Humans are a key driver in the hydrology of coastal aquifers and that adapting to sea level rise at the expense of better water management is misguided.

Diagnosing and Reconstructing Real-World Hydroclimatic Dynamics from Time Sequenced Data: The Case of Saltwater Intrusion into Coastal Wetlands in Everglades National Park

NASA Astrophysics Data System (ADS)

Huffaker, R.; Munoz-Carpena, R.

2016-12-01

There are increasing calls to audit decision-support models used for environmental policy to ensure that they correspond with the reality facing policy makers. Modelers can establish correspondence by providing empirical evidence of real-world dynamic behavior that their models skillfully simulate. We present a pre-modeling diagnostic framework—based on nonlinear dynamic analysis—for detecting and reconstructing real-world environmental dynamics from observed time-sequenced data. Phenomenological (data-driven) modeling—based on machine learning regression techniques—extracts a set of ordinary differential equations governing empirically-diagnosed system dynamics from a single time series, or from multiple time series on causally-interacting variables. We apply the framework to investigate saltwater intrusion into coastal wetlands in Everglades National Park, Florida, USA. We test the following hypotheses posed in the literature linking regional hydrologic variables with global climatic teleconnections: (1) Sea level in Florida Bay drives well level and well salinity in the coastal Everglades; (2) Atlantic Multidecadal Oscillation (AMO) drives sea level, well level and well salinity; and (3) AMO and (El Niño Southern Oscillation) ENSO bi-causally interact. The thinking is that salt water intrusion links ocean-surface salinity with salinity of inland water sources, and sea level with inland water; that AMO and ENSO share a teleconnective relationship (perhaps through the atmosphere); and that AMO and ENSO both influence inland precipitation and thus well levels. Our results support these hypotheses, and we successfully construct a parsimonious phenomenological model that reproduces diagnosed nonlinear dynamics and system interactions. We propose that reconstructed data dynamics be used, along with other expert information, as a rigorous benchmark to guide specification and testing of hydrologic decision support models corresponding with real-world behavior.

Arctic sea ice area in CMIP3 and CMIP5 climate model ensembles - variability and change

NASA Astrophysics Data System (ADS)

Semenov, V. A.; Martin, T.; Behrens, L. K.; Latif, M.

2015-02-01

The shrinking Arctic sea ice cover observed during the last decades is probably the clearest manifestation of ongoing climate change. While climate models in general reproduce the sea ice retreat in the Arctic during the 20th century and simulate further sea ice area loss during the 21st century in response to anthropogenic forcing, the models suffer from large biases and the model results exhibit considerable spread. The last generation of climate models from World Climate Research Programme Coupled Model Intercomparison Project Phase 5 (CMIP5), when compared to the previous CMIP3 model ensemble and considering the whole Arctic, were found to be more consistent with the observed changes in sea ice extent during the recent decades. Some CMIP5 models project strongly accelerated (non-linear) sea ice loss during the first half of the 21st century. Here, complementary to previous studies, we compare results from CMIP3 and CMIP5 with respect to regional Arctic sea ice change. We focus on September and March sea ice. Sea ice area (SIA) variability, sea ice concentration (SIC) variability, and characteristics of the SIA seasonal cycle and interannual variability have been analysed for the whole Arctic, termed Entire Arctic, Central Arctic and Barents Sea. Further, the sensitivity of SIA changes to changes in Northern Hemisphere (NH) averaged temperature is investigated and several important dynamical links between SIA and natural climate variability involving the Atlantic Meridional Overturning Circulation (AMOC), North Atlantic Oscillation (NAO) and sea level pressure gradient (SLPG) in the western Barents Sea opening serving as an index of oceanic inflow to the Barents Sea are studied. The CMIP3 and CMIP5 models not only simulate a coherent decline of the Arctic SIA but also depict consistent changes in the SIA seasonal cycle and in the aforementioned dynamical links. The spatial patterns of SIC variability improve in the CMIP5 ensemble, particularly in summer. Both CMIP ensembles depict a significant link between the SIA and NH temperature changes. Our analysis suggests that, on average, the sensitivity of SIA to external forcing is enhanced in the CMIP5 models. The Arctic SIA variability response to anthropogenic forcing is different in CMIP3 and CMIP5. While the CMIP3 models simulate increased variability in March and September, the CMIP5 ensemble shows the opposite tendency. A noticeable improvement in the simulation of summer SIA by the CMIP5 models is often accompanied by worse results for winter SIA characteristics. The relation between SIA and mean AMOC changes is opposite in September and March, with March SIA changes being positively correlated with AMOC slowing. Finally, both CMIP ensembles demonstrate an ability to capture, at least qualitatively, important dynamical links of SIA to decadal variability of the AMOC, NAO and SLPG. SIA in the Barents Sea is strongly overestimated by the majority of the CMIP3 and CMIP5 models, and projected SIA changes are characterized by a large spread giving rise to high uncertainty.

Correspondence of Mesozoic Eustatic Sea-Level Change with Palaeoclimate Proxies: Evidence for Glacio-Eustasy?

NASA Astrophysics Data System (ADS)

Simmons, M.; Davies, A.; Gréselle, B.

2011-12-01

Large-scale changes in stratigraphic architecture and facies that are brought about by changes in relative sea-level have been the focus of much academic and industry study over the last few decades. The authors, plus numerous colleagues, have studied over 11,000 stratigraphic sections worldwide. By applying biostratigraphic and chemostratigraphic calibration in suitable locations from this dataset it is possible to demonstrate over 250 synchronous global sequence stratigraphic events in the Phanerozoic including over 100 in the Mesozoic. This then raises the question - what causes globally synchronous eustatic sea-level change? To answer this question requires an understanding of both the pace and amplitude of the observed eustatic sea-level change. In successions where duration can be deduced from orbital forcing cycles, our observed sea-level changes appear to be relatively rapid - less than 500,000 years, for example, for sea-level rises in the Late Jurassic. The amplitude of such rises is in the order of tens of metres. Such rates and amplitudes as inferred from our global model preclude tectonism as a primary driver and implicate glacio-eustacy as a key driving mechanism, even in supposed "greenhouse times". Given the clear economic importance of understanding the underlying mechanisms driving this eustatic change we have compiled records of key isotopic proxies through the entire Mesozoic in an effort to explore the relationship between global sea-level and palaeoclimate. Our research reveals a clear link between many large-scale maximum flooding events with known episodes of palaeoclimatic warming and between climatic cooling events and lowstand intervals, further implicating glacio-eustacy. In addition to the isotopic proxy evidence we have also compiled direct indicators for the occurrence of cold polar conditions, including the presence of ice sheets, in the Mesozoic (e.g. tillites, glendonites). This has been incorporated into plate tectonic reconstructions in order to explore the relationship with the presence of significant polar land masses. Both isotopic and direct evidence suggest the episodic presence of polar ice sheets for periods previously supposed as ice free and that glacio-eustacy can be suggested as a major driver of Mesozoic eustatic sea-level change.

Formation and fate of sedimentary depocentres on Southeast Asia's Sunda Shelf over the past sea-level cycle and biogeographic implications

NASA Astrophysics Data System (ADS)

Hanebuth, Till J. J.; Voris, Harold K.; Yokoyama, Yusuke; Saito, Yoshiki; Okuno, Jun'ichi

2011-01-01

Sea-level variations are the major factor controlling sedimentation as well as the biogeographic patterns at continental margins over late Quaternary times. Fluctuations on millennial time-scales produce locally complex deposits in coasts and on shelves, associated with short-term influence on species development. This article reviews the sedimentary and biogeographic history of the tropical siliciclastic Sunda Shelf as an end-member of continental shelves regarding extreme width, an enormous sediment supply, and highest biodiversity in response to rapid sea-level fluctuations. We describe particular depositional segments as part of a genetic succession of zones from land to the deep sea based on literature data, field observations, and calculation of hydro-isostatic adjustment effects on changing relative sea level. These segments are characterized by individual sedimentary processes and deposits, and by a specific potential for material storage and re-mobilization. Long-term regressive intervals led to overall sigmoidal-promoting, extremely thick, and wide succeeding units. In contrast, rapid lateral shifts of defined depocentres over long distances took place in response to short-term sea level fluctuations. Fully isolated small-scale sediment bodies formed when sea level changed at exceptionally high rates. As a result of the high availability of organic-rich sediments, mangrove and freshwater peats formed frequently over late Quaternary times. The appearance of thick, massive and widespread peats is mainly linked to time intervals of a sea-level rise at slow rates, whilst organic matter appears much more dispersely in the sediments during episodes of rapidly changing sea level. The preservation potential of the regressive units is generally high due to highest initial sediment supply, stabilizing soil formation during exposure and rapid subsidence. Preservation of depositional elements from other periods is more exceptional and either restricted to local morphological depressions or to episodes of rapid sea level change. Besides complex channel incision, an overall lowering of the sediment surface related to erosion, as deep as 20 m or more, over wide areas took place mainly during sea level lowering. The final export of shelf material is documented by enormous mass-wasting packages on the associated continental slope. From a palaeogeographic perspective, the rapid formation or disappearance of special habitat zones, such as mangrove fringes and extended mud flats, led to species establishment or truncation in distribution. In addition, the opening or closure of ocean passages, as narrow bridges allowing limited species crossing or as fully colonized corridors, had severe impact on eco-fragmentation and the expansion or contraction of species. Independent of such particular conditions, sea-level changes have been too rapid over the past climatic cycle to allow full regeneration and mature development of coast-related ecosystems.

Sea Level History in 3D: Early results of an ultra-high resolution MCS survey across IODP Expedition 313 drillsites

NASA Astrophysics Data System (ADS)

Mountain, G. S.; Kucuk, H. M.; Nedimovic, M. R.; Austin, J. A., Jr.; Fulthorpe, C.; Newton, A.; Baldwin, K.; Johnson, C.; Stanley, J. N.; Bhatnagar, T.

2015-12-01

Although globally averaged sea level is rising at roughly 3 mm/yr (and is accelerating), rates of local sea-level change measured at coastlines may differ from this number by a factor of two or more; at some locations, sea level may even be falling. This is due to local processes that can match or even reverse the global trend, making it clear that reliable predictions of future impacts of sea-level rise require a firm understanding of processes at the local level. The history of local sea-level change and shoreline response is contained in the geologic record of shallow-water sediments. We report on a continuing study of sea-level history in sediments at the New Jersey continental margin, where compaction and glacial isostatic adjustment are currently adding 2 mm/yr to the globally averaged rise. We collected 570 sq km of ultra-high resolution 3D MCS data aboard the R/V Langseth in June-July 2015; innovative recording and preliminary results are described by Nedimovic et al. in this same session. The goal was to provide regional context to coring and logging at IODP Exp 313 sites 27-29 that were drilled 750 m into the New Jersey shelf in 2009. These sites recovered a nearly continuous record of post-Eocene sediments from non-marine soils, estuaries, shoreface, delta front, pro-delta and open marine settings. Existing seismic data are good but are 2D high-resolution profiles at line spacings too wide to enable mapping of key nearshore features. The Langseth 3D survey used shallow towing of a tuned air gun array to preserve high frequencies, and twenty-four 50-m PCables each 12.5 apart provided 6.25 x 3.125 m common-midpoint bins along seventy-seven 50-km sail lines. With this especially dense spatial resolution of a pre-stack time migrated volume we expect to map rivers, incised valleys, barrier islands, inlets and bays, pro-delta clinoforms, tidal deltas, sequence boundaries, debris flow aprons, and more. Seismic attributes linked to sedimentary facies and geochronology at Exp 313 drill sites will be extended throughout the volume to map the local response to global sea-level change. These analyses will provide an unrivaled opportunity to gauge the local expression of sea-level change for much of the last 40 Ma and lead to informed predictions regarding impacts of a global rise of sea level expected to continue well into the future.

High-precision GPS autonomous platforms for sea ice dynamics and physical oceanography

NASA Astrophysics Data System (ADS)

Elosegui, P.; Wilkinson, J.; Olsson, M.; Rodwell, S.; James, A.; Hagan, B.; Hwang, B.; Forsberg, R.; Gerdes, R.; Johannessen, J.; Wadhams, P.; Nettles, M.; Padman, L.

2012-12-01

Project "Arctic Ocean sea ice and ocean circulation using satellite methods" (SATICE), is the first high-rate, high-precision, continuous GPS positioning experiment on sea ice in the Arctic Ocean. The SATICE systems collect continuous, dual-frequency carrier-phase GPS data while drifting on sea ice. Additional geophysical measurements also collected include ocean water pressure, ocean surface salinity, atmospheric pressure, snow-depth, air-ice-ocean temperature profiles, photographic imagery, and others, enabling sea ice drift, freeboard, weather, ice mass balance, and sea-level height determination. Relatively large volumes of data from each buoy are streamed over a satellite link to a central computer on the Internet in near real time, where they are processed to estimate the time-varying buoy positions. SATICE system obtains continuous GPS data at sub-minute intervals with a positioning precision of a few centimetres in all three dimensions. Although monitoring of sea ice motions goes back to the early days of satellite observations, these autonomous platforms bring out a level of spatio-temporal detail that has never been seen before, especially in the vertical axis. These high-resolution data allows us to address new polar science questions and challenge our present understanding of both sea ice dynamics and Arctic oceanography. We will describe the technology behind this new autonomous platform, which could also be adapted to other applications that require high resolution positioning information with sustained operations and observations in the polar marine environment, and present results pertaining to sea ice dynamics and physical oceanography.

The Arctic-Subarctic Sea Ice System is Entering a Seasonal Regime: Implications for Future Arctic Amplication

NASA Astrophysics Data System (ADS)

Haine, T. W. N.; Martin, T.

2017-12-01

The loss of Arctic sea ice is a conspicuous example of climate change. Climate models project ice-free conditions during summer this century under realistic emission scenarios, reflecting the increase in seasonality in ice cover. To quantify the increased seasonality in the Arctic-Subarctic sea ice system, we define a non-dimensional seasonality number for sea ice extent, area, and volume from satellite data and realistic coupled climate models. We show that the Arctic-Subarctic, i.e. the northern hemisphere, sea ice now exhibits similar levels of seasonality to the Antarctic, which is in a seasonal regime without significant change since satellite observations began in 1979. Realistic climate models suggest that this transition to the seasonal regime is being accompanied by a maximum in Arctic amplification, which is the faster warming of Arctic latitudes compared to the global mean, in the 2010s. The strong link points to a peak in sea-ice-related feedbacks that occurs long before the Arctic becomes ice-free in summer.

Arctic Climate and Atmospheric Planetary Waves

NASA Technical Reports Server (NTRS)

Cavalieri, D. J.; Haekkinen, S.

2000-01-01

Analysis of a fifty-year record (1946-1995) of monthly-averaged sea level pressure data provides a link between the phases of planetary-scale sea level pressure waves and Arctic Ocean and ice variability. Results of this analysis show: (1) a breakdown of the dominant wave I pattern in the late 1960's, (2) shifts in the mean phase of waves 1 and 2 since this breakdown, (3) an eastward shift in the phases of both waves 1 and 2 during the years of simulated cyclonic Arctic Ocean circulation relative to their phases during the years of anticyclonic circulation, (4) a strong decadal variability of wave phase associated with simulated Arctic Ocean circulation changes. Finally, the Arctic atmospheric circulation patterns that emerge when waves 1 and 2 are in their extreme eastern and western positions suggest an alternative approach to determine significant forcing patterns of sea ice and high-latitude variability.

Links between Patagonian Ice Sheet fluctuations and Antarctic dust variability during the last glacial period (MIS 4-2)

NASA Astrophysics Data System (ADS)

Kaiser, Jérôme; Lamy, Frank

2010-06-01

Antarctic and Greenland ice-core records reveal large fluctuations of dust input on both orbital and millennial time-scales with potential global climate implications. At least during glacial periods, the Antarctic dust fluctuations appear to be largely controlled by environmental changes in southern South America. We compare dust flux records from two Antarctic ice-cores to variations in the composition of the terrigenous supply at ODP Site 1233 located off southern Chile and known to record fluctuations in the extent of the northern part of the Patagonian ice-sheet (NPIS) during the last glacial period (Marine Isotope Stage, MIS, 4 to 2). Within age uncertainties, millennial-scale glacial advances (retreats) of the NPIS correlate to Antarctic dust maxima (minima). In turn, NPIS fluctuations were closely related to offshore sea surface temperature (SST) changes. This pattern suggests a causal link involving changes in temperature, in rock flour availability, in latitudinal extensions of the westerly winds and in foehn winds in the southern Pampas and Patagonia. We further suggest that the long-term trend of dust accumulation is partly linked to the sea-level related changes in the size if the Patagonian source area due to the particular morphology of the Argentine shelf. We suggest that sea-level drops at the beginning of MIS 4 and MIS 2 were important for long-term dust increases, while changes in the Patagonian dust source regions primarily control the early dust decrease during the MIS 4/3 transition and Termination 1.

GOES Composite - El Niño Support Imagery - Satellite Products and Services

Science.gov Websites

Division/Office of Satellite and Product Operations Skip Navigation Link NESDIS banner image Information Service Home Page Default Office of Satellite and Product Operations banner image and link to OSPO MIRS MSPPS Ocean -- Coral Bleaching -- Ocean Color -- Sea/Lake Ice -- Sea Surface Height -- Sea Surface

Sea level variability influencing coastal flooding in the Swan River region, Western Australia

NASA Astrophysics Data System (ADS)

Eliot, Matt

2012-02-01

Coastal flooding refers to the incidence of high water levels produced by water level fluctuations of marine origin, rather than riverine floods. An understanding of the amplitude and frequency of high water level events is essential to foreshore management and the design of many coastal and estuarine facilities. Coastal flooding events generally determine public perception of sea level phenomena, as they are commonly associated with erosion events. This investigation has explored the nature of coastal flooding events affecting the Swan River Region, Western Australia, considering water level records at four sites in the estuary and lower river, extending from the mouth of the Swan River to 40 km upstream. The analysis examined the significance of tides, storms and mean sea level fluctuations over both seasonal and inter-annual time scales. The relative timing of these processes is significant for the enhanced or reduced frequency of coastal flooding. These variations overlie net sea level rise previously reported from the coastal Fremantle record, which is further supported by changes to the distribution of high water level events at an estuarine tidal station. Seasonally, coastal flooding events observed in the Swan River region are largely restricted to the period from May to July due to the relative phases of the annual mean sea fluctuation and biannual tidal cycle. Although significant storm surge events occur outside this period, their impact is normally reduced, as they are superimposed on lower tidal and mean sea level conditions. Over inter-annual time scales tide, storminess and mean sea level produce cycles of enhanced and depressed frequency of coastal flooding. For the Swan River region, the inter-annual tidal variation is regular, dominated by the 18.6 year lunar nodal cycle. Storminess and mean sea level variations are independent and irregular, with cycles from 3 to 10 year duration. Since 1960, these fluctuations have not occurred in phase, suggesting that recent historic records may not provide a real indication of inundation risk, exclusive of factors linked to climate change. The burst-like nature of coastal flooding incidents, with respect to frequency, has implications for both public perception and coastal management effort. The result, when combined with sea level rise, produces step-like change, with short periods of frequent coastal flooding, followed by extended, slowly varying quiescent periods. This presents challenges for coastal managers to incorporate variability into projections of future management needs, and to ensure that public and political recognition of coastal flooding hazard is not downplayed during quiet periods.

Holocene sea level, a semi-empirical contemplation

NASA Astrophysics Data System (ADS)

Bittermann, Klaus; Kemp, Andrew; Vermeer, Martin; Rahmstorf, Stefan

2017-04-01

Holocene eustatic sea level from approximately -10,000-1800 CE was characterized by an increase of about 60 m, with the rate progressively slowing down until sea level almost stabilizes between 500-1800 CE. Global and northern-hemisphere temperatures rose from the last glacial termination until the 'Holocene Optimum'. From there, up to the start of the recent anthropogenic rise, they almost steadily decline. How are the sea-level and temperature evolutions linked? We investigate this with a semi-empirical sea-level model. We found that, due to the nature of Milankovitch forcing, northern-hemisphere temperature (we used the Greenland temperature by Vinther et al., 2009) is a better model driver than global mean temperature because the evolving mass of northern-hemisphere land ice was the dominant cause of Holocene global sea-level trends. The adjustment timescale for this contribution is 1200 years (900-1500 years; 90% confidence interval). To fit the observed sea-level history, the model requires a small additional constant rate (Bittermann 2016). This rate turns out to be of the same order of magnitude as reconstructions of Antarctic sea-level contributions (Briggs et al. 2014, Golledge et al. 2014). In reality this contribution is unlikely to be constant but rather has a dominant timescale that is large compared to the time considered. We thus propose that Holocene sea level can be described by a linear combination of a temperature driven rate, which becomes negative in the late Holocene (as Northern Hemisphere ice masses are diminished), and a positive, approximately constant term (possibly from Antarctica), which starts to dominate from the middle of the Holocene until the start of industrialization. Bibliography: Bittermann, K. 2016. Semi-empirical sea-level modelling. PhD Thesis University of Potsdam. Briggs, R.D., Pollard, D., & Tarasov, L. 2014. A data-constrained large ensemble analysis of Antarctic evolution since the Eemian. Quaternary science reviews, 103, 91-115. Golledge, N.R., Menviel, L., Carter, L., Fogwill, C.J., England, M.H., Cortese, G., & Levy, R.H. 2014. Antarctic contribution to meltwater pulse 1A from reduced Southern Ocean overturning. Nature communications, 5, 5107. Vinther, B.M., Buchardt, S.L., Clausen, H.B., Dahl-Jensen, D., Johnsen, S.J., Fisher, D.A., Koerner, R.M., Raynaud, D., Lipenkov, V., Andersen, K.K., Blunier, T., Rasmussen, S.O., Steffensen, J.P., & Svensson, A.M. 2009. Holocene thinning of the Greenland ice sheet. Nature, 461(7262), 385-388.

Examining spatial variability in relative sea-level in the New York City/New Jersey region during the Common Era

NASA Astrophysics Data System (ADS)

Walker, Jennifer; Clear, Jennifer; Garcia-Artola, Ane; Khan, Nicole; Shaw, Timothy; Corbett, Reide; Kemp, Andrew; Kopp, Robert; Horton, Benjamin

2017-04-01

Relative sea-level (RSL) reconstructions extend the 20th century instrumental record (tide gauge and satellite measurements) of spatial and temporal sea-level variability to provide a much longer context for recent trends and projected RSL rise. Common Era (last 2000 years) RSL reconstructions illustrate patterns of natural variability and include natural phases of climate and sea-level which will improve our knowledge basis for sea-level responses to climate changes. The northeast U.S. has exhibited varying rates in relative sea-level rise through the Common Era, primarily due to glacial isostatic adjustment. However, other factors such as ocean/atmosphere dynamics, sediment compaction, and the static equilibrium response to land ice changes, further influence the evolution of relative sea-level. The spatial variability is manifest in the tide gauge records. The tide gauge at the Battery, New York City (1856 to 2015) records a relative sea-level rise of 2.8 mm/yr whereas the tide gauge at Sandy Hook, New Jersey (1932 to 2015), 25 km southeast, records 4.1 mm/yr. Here we present a new reconstruction of RSL in northern New Jersey using geological and tide gauge data. A Common Era sea-level record from northern New Jersey fills in the spatial gap between records completed in southern New Jersey, New York City, and Connecticut. Our field study site is in Cheesequake State Park, where we observed sedimentary sequences dating back 2000 cal. yrs. BP. We use microfossil indicators preserved in salt-marsh sediments as a proxy to reconstruct RSL with decimeter precision. Salt-marsh foraminifera act as reliable RSL indicators because their modern distribution is strongly linked to tidal elevation. The recent application of microfossil-based transfer functions has enabled continuous records of RSL, extending centuries before the modern instrumental period, to be produced with a full consideration of uncertainty. We use a composite chronology of AMS 14C, pollen chrono-horizons, pollution histories, and a 137Cs spike (AD 1963) to achieve multi-decadal temporal precision. The RSL record for northern New Jersey shows a 2.4 m rise during the past 2000 years at a mean rate of 1.2 mm/yr. This compares to rates from a database of Holocene relative sea-level observations for the U.S. Atlantic coast which found a rise of 1.4 mm/yr for New Jersey and 1.3 mm/yr for New York from 4 ka BP to AD 1900 (Engelhart and Horton, 2012).

Extreme sea levels on the rise along Europe's coasts

NASA Astrophysics Data System (ADS)

Vousdoukas, Michalis I.; Mentaschi, Lorenzo; Voukouvalas, Evangelos; Verlaan, Martin; Feyen, Luc

2017-03-01

Future extreme sea levels (ESLs) and flood risk along European coasts will be strongly impacted by global warming. Yet, comprehensive projections of ESL that include mean sea level (MSL), tides, waves, and storm surges do not exist. Here, we show changes in all components of ESLs until 2100 in view of climate change. We find that by the end of this century, the 100-year ESL along Europe's coastlines is on average projected to increase by 57 cm for Representative Concentration Pathways (RCP)4.5 and 81 cm for RCP8.5. The North Sea region is projected to face the highest increase in ESLs, amounting to nearly 1 m under RCP8.5 by 2100, followed by the Baltic Sea and Atlantic coasts of the UK and Ireland. Relative sea level rise (RSLR) is shown to be the main driver of the projected rise in ESL, with increasing dominance toward the end of the century and for the high-concentration pathway. Changes in storm surges and waves enhance the effects of RSLR along the majority of northern European coasts, locally with contributions up to 40%. In southern Europe, episodic extreme events tend to stay stable, except along the Portuguese coast and the Gulf of Cadiz where reductions in surge and wave extremes offset RSLR by 20-30%. By the end of this century, 5 million Europeans currently under threat of a 100-year ESL could be annually at risk from coastal flooding under high-end warming. The presented dataset is available through this link: http://data.jrc.ec.europa.eu/collection/LISCOAST.

High-resolution IP25-based reconstruction of sea-ice variability in the western North Pacific and Bering Sea during the past 18,000 years

NASA Astrophysics Data System (ADS)

Méheust, Marie; Stein, Ruediger; Fahl, Kirsten; Max, Lars; Riethdorf, Jan-Rainer

2016-04-01

Due to its strong influence on heat and moisture exchange between the ocean and the atmosphere, sea ice is an essential component of the global climate system. In the context of its alarming decrease in terms of concentration, thickness and duration, understanding the processes controlling sea-ice variability and reconstructing paleo-sea-ice extent in polar regions have become of great interest for the scientific community. In this study, for the first time, IP25, a recently developed biomarker sea-ice proxy, was used for a high-resolution reconstruction of the sea-ice extent and its variability in the western North Pacific and western Bering Sea during the past 18,000 years. To identify mechanisms controlling the sea-ice variability, IP25 data were associated with published sea-surface temperature as well as diatom and biogenic opal data. The results indicate that a seasonal sea-ice cover existed during cold periods (Heinrich Stadial 1 and Younger Dryas), whereas during warmer intervals (Bølling-Allerød and Holocene) reduced sea ice or ice-free conditions prevailed in the study area. The variability in sea-ice extent seems to be linked to climate anomalies and sea-level changes controlling the oceanographic circulation between the subarctic Pacific and the Bering Sea, especially the Alaskan Stream injection though the Aleutian passes.

Sea ice and polar climate in the NCAR CSM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weatherly, J.W.; Briegleb, B.P.; Large, W.G.

The Climate System Model (CSM) consists of atmosphere, ocean, land, and sea-ice components linked by a flux coupler, which computes fluxes of energy and momentum between components. The sea-ice component consists of a thermodynamic formulation for ice, snow, and leads within the ice pack, and ice dynamics using the cavitating-fluid ice rheology, which allows for the compressive strength of ice but ignores shear viscosity. The results of a 300-yr climate simulation are presented, with the focus on sea ice and the atmospheric forcing over sea ice in the polar regions. The atmospheric model results are compared to analyses from themore » European Centre for Medium-Range Weather Forecasts and other observational sources. The sea-ice concentrations and velocities are compared to satellite observational data. The atmospheric sea level pressure (SLP) in CSM exhibits a high in the central Arctic displaced poleward from the observed Beaufort high. The Southern Hemisphere SLP over sea ice is generally 5 mb lower than observed. Air temperatures over sea ice in both hemispheres exhibit cold biases of 2--4 K. The precipitation-minus-evaporation fields in both hemispheres are greatly improved over those from earlier versions of the atmospheric GCM.« less

Changing flood frequencies under opposing late Pleistocene eastern Mediterranean climates.

PubMed

Ben Dor, Yoav; Armon, Moshe; Ahlborn, Marieke; Morin, Efrat; Erel, Yigal; Brauer, Achim; Schwab, Markus Julius; Tjallingii, Rik; Enzel, Yehouda

2018-05-31

Floods comprise a dominant hydroclimatic phenomenon in aridlands with significant implications for humans, infrastructure, and landscape evolution worldwide. The study of short-term hydroclimatic variability, such as floods, and its forecasting for episodes of changing climate therefore poses a dominant challenge for the scientific community, and predominantly relies on modeling. Testing the capabilities of climate models to properly describe past and forecast future short-term hydroclimatic phenomena such as floods requires verification against suitable geological archives. However, determining flood frequency during changing climate is rarely achieved, because modern and paleoflood records, especially in arid regions, are often too short or discontinuous. Thus, coeval independent climate reconstructions and paleoflood records are required to further understand the impact of climate change on flood generation. Dead Sea lake levels reflect the mean centennial-millennial hydrological budget in the eastern Mediterranean. In contrast, floods in the large watersheds draining directly into the Dead Sea, are linked to short-term synoptic circulation patterns reflecting hydroclimatic variability. These two very different records are combined in this study to resolve flood frequency during opposing mean climates. Two 700-year-long, seasonally-resolved flood time series constructed from late Pleistocene Dead Sea varved sediments, coeval with significant Dead Sea lake level variations are reported. These series demonstrate that episodes of rising lake levels are characterized by higher frequency of floods, shorter intervals between years of multiple floods, and asignificantly larger number of years that experienced multiple floods. In addition, floods cluster into intervals of intense flooding, characterized by 75% and 20% increased frequency above their respective background frequencies during rising and falling lake-levels, respectively. Mean centennial precipitation in the eastern Mediterranean is therefore coupled with drastic changes in flood frequencies. These drastic changes in flood frequencies are linked to changes in the track, depth, and frequency of mid-latitude eastern Mediterranean cyclones, determining mean climatology resulting in wetter and drier regional climatic episodes.

Variations in freshwater pathways from the Arctic Ocean into the North Atlantic Ocean

NASA Astrophysics Data System (ADS)

Wang, Zeliang; Hamilton, James; Su, Jie

2017-06-01

Understanding the mechanisms that drive exchanges between the Arctic Ocean and adjacent oceans is critical to building our knowledge of how the Arctic is reacting to a warming climate, and how potential changes in Arctic Ocean freshwater export may impact the AMOC (Atlantic Meridional Overturning Circulation). Here, freshwater pathways from the Arctic Ocean to the North Atlantic are investigated using a 1 degree global model. An EOF analysis of modeled sea surface height (SSH) demonstrates that while the second mode accounts for only 15% of the variability, the associated geostrophic currents are strongly correlated with freshwater exports through CAA (Canadian Arctic Archipelago; r = 0.75), Nares Strait (r = 0.77) and Fram Strait (r = -0.60). Separation of sea level into contributing parts allows us to show that the EOF1 is primarily a barotropic mode reflecting variability in bottom pressure equivalent sea level, while the EOF2 mode reflects changes in steric height in the Arctic Basin. This second mode is linked to momentum wind driven surface current, and dominates the Arctic Ocean freshwater exports. Both the Arctic Oscillation and Arctic Dipole atmospheric indices are shown to be linked to Arctic Ocean freshwater exports, with the forcing associated with the Arctic Dipole reflecting the out-of-phase relationship between transports through the CAA and those through Fram Strait. Finally, observed freshwater transport variation through the CAA is found to be strongly correlated with tide gauge data from the Beaufort Sea coast (r = 0.81), and with the EOF2 mode of GRACE bottom pressure data (r = 0.85) on inter-annual timescales.

Evolving Understanding of Antarctic Ice-Sheet Physics and Ambiguity in Probabilistic Sea-Level Projections

NASA Astrophysics Data System (ADS)

Kopp, Robert E.; DeConto, Robert M.; Bader, Daniel A.; Hay, Carling C.; Horton, Radley M.; Kulp, Scott; Oppenheimer, Michael; Pollard, David; Strauss, Benjamin H.

2017-12-01

Mechanisms such as ice-shelf hydrofracturing and ice-cliff collapse may rapidly increase discharge from marine-based ice sheets. Here, we link a probabilistic framework for sea-level projections to a small ensemble of Antarctic ice-sheet (AIS) simulations incorporating these physical processes to explore their influence on global-mean sea-level (GMSL) and relative sea-level (RSL). We compare the new projections to past results using expert assessment and structured expert elicitation about AIS changes. Under high greenhouse gas emissions (Representative Concentration Pathway [RCP] 8.5), median projected 21st century GMSL rise increases from 79 to 146 cm. Without protective measures, revised median RSL projections would by 2100 submerge land currently home to 153 million people, an increase of 44 million. The use of a physical model, rather than simple parameterizations assuming constant acceleration of ice loss, increases forcing sensitivity: overlap between the central 90% of simulations for 2100 for RCP 8.5 (93-243 cm) and RCP 2.6 (26-98 cm) is minimal. By 2300, the gap between median GMSL estimates for RCP 8.5 and RCP 2.6 reaches >10 m, with median RSL projections for RCP 8.5 jeopardizing land now occupied by 950 million people (versus 167 million for RCP 2.6). The minimal correlation between the contribution of AIS to GMSL by 2050 and that in 2100 and beyond implies current sea-level observations cannot exclude future extreme outcomes. The sensitivity of post-2050 projections to deeply uncertain physics highlights the need for robust decision and adaptive management frameworks.

Evolving Understanding of Antarctic Ice-Sheet Physics and Ambiguity in Probabilistic Sea-Level Projections

NASA Technical Reports Server (NTRS)

Kopp, Robert E.; DeConto, Robert M.; Bader, Daniel A.; Hay, Carling C.; Horton, Radley M.; Kulp, Scott; Oppenheimer, Michael; Pollard, David; Strauss, Benjamin

2017-01-01

Mechanisms such as ice-shelf hydrofracturing and ice-cliff collapse may rapidly increase discharge from marine-based ice sheets. Here, we link a probabilistic framework for sea-level projections to a small ensemble of Antarctic ice-sheet (AIS) simulations incorporating these physical processes to explore their influence on global-mean sea-level (GMSL) and relative sea-level (RSL). We compare the new projections to past results using expert assessment and structured expert elicitation about AIS changes. Under high greenhouse gas emissions (Representative Concentration Pathway [RCP] 8.5), median projected 21st century GMSL rise increases from 79 to 146 cm. Without protective measures, revised median RSL projections would by 2100 submerge land currently home to 153 million people, an increase of 44 million. The use of a physical model, rather than simple parameterizations assuming constant acceleration of ice loss, increases forcing sensitivity: overlap between the central 90% of simulations for 2100 for RCP 8.5 (93-243 cm) and RCP 2.6 (26-98 cm) is minimal. By 2300, the gap between median GMSL estimates for RCP 8.5 and RCP 2.6 reaches >10 m, with median RSL projections for RCP 8.5 jeopardizing land now occupied by 950 million people (versus 167 million for RCP 2.6). The minimal correlation between the contribution of AIS to GMSL by 2050 and that in 2100 and beyond implies current sea-level observations cannot exclude future extreme outcomes. The sensitivity of post-2050 projections to deeply uncertain physics highlights the need for robust decision and adaptive management frameworks.

Quantitative controls on location and architecture of carbonate depositional sequences: Upper miocene, cabo de gata region, SE Spain

USGS Publications Warehouse

Franseen, E.K.; Goldstein, R.H.; Farr, M.R.

1997-01-01

Sequence stratigraphy, pinning-point relative sea-level curves, and magnetostratigraphy provide the quantitative data necessary to understand how rates of sea-level change and different substrate paleoslopes are dominant controls on accumulation rate, carbonate depositional sequence location, and internal architecture. Five third-order (1-10 my) and fourth-order (0.1-1.0 my) upper Miocene carbonate depositional sequences (DS1A, DS1B, DS2, DS3, TCC) formed with superimposed higher-frequency sea-level cycles in an archipelago setting in SE Spain. Overall, our study indicates when areas of high substrate slope (> 15??) are in shallow water, independent of climate, the location and internal architecture of carbonate deposits are not directly linked to sea-level position but, instead, are controlled by location of gently sloping substrates and processes of bypass. In contrast, if carbonate sediments are generated where substrates of low slope ( 15.6 cm/ky to ??? 2 cm/ky and overall relative sea level rose at rates of 17-21.4 cm/ky. Higher frequency sea-level rates were about 111 to more than 260 cm/ky, producing onlapping, fining- (deepening-) upward cycles. Decreasing accumulation rates resulted from decreasing surface area for shallow-water sediment production, drowning of shallow-water substrates, and complex sediment dispersal related to the archipelago setting. Typical systems tract and parasequence development should not be expected in "bypass ramp" settings; facies of onlapping strata do not track base level and are likely to be significantly different compared to onlapping strata associated with coastal onlap. Basal and upper DS2 reef megabreccias (indicating the transition from cool to warmer climatic conditions) were eroded from steep upslope positions and redeposited downslope onto areas of gentle substrate during rapid sea-level falls (> 22.7 cm/ky) of short duration. Such rapid sea-level falls and presence of steep slopes are not conducive to formation of forced regressive systems tracts composed of down-stepping reef clinoforms. The DS3 reefal platform formed where shallow water coincided with gently sloping substrates created by earlier deposition. Slow progradation (0.39-1.45 km/my) is best explained by the lack of an extensive bank top, progressively falling sea level, and low productivity resulting from siliciclastic debris and excess nutrients shed from nearby volcanic islands. Although DS3 strata were deposited during a third-order relative sea-level cycle, a typical transgressive systems tract is not recognizable, indicating that the initial relative rise in sea level was too rapid (??? 19 cm/ky). Downstepping reefs, forming a forced regressive systems tract, were deposited during the relative sea-level fall at the end of DS3, indicating that relatively slow rates of fall (10 cm/ky or less) over favorable paleoslope conditions are conducive to generation of forced regressive systems tracts consisting of downstepping reef clinoforms. The TCC sequence consists of four shallow-water sedimentary cycles that were deposited during a 400 ky to 100 ky time span. Such shallow-water cycles, typical of many platforms, form only where shallow water intersects gently sloping substrates. The relative thicknesses of cycles (< 2 m to 15 m thick), magnitudes of relative sea-level fluctuations associated with each cycle (25-30 m), high rates of relative sea-level fluctuations (minimum of 25-120 cm/ky), and the widespread distribution of similar TCC cycles in the Mediterranean and elsewhere are supportive of a glacio-eustatic

Quantitative controls on location and architecture of carbonate depositional sequences: upper miocene, cabo de gata region, se Spain

USGS Publications Warehouse

Franseen, E.K.; Goldstein, R.H.; Farr, M.R.

1998-01-01

Sequence stratigraphy, pinning-point relative sea-level curves, and magnetostratigraphy provide the quantitative data necessary to understand how rates of sea-level change and different substrate paleoslopes are dominant controls on accumulation rate, carbonate depositional sequence location, and internal architecture. Five third-order (1-10 my) and fourth-order (0.1-1.0 my) upper Miocene carbonate depositional sequences (DS1A, DS1B, DS2, DS3, TCC) formed with superimposed higher-frequency sea-level cycles in an archipelago setting in SE Spain. Overall, our study indicates when areas of high substrate slope (> 15??) are in shallow water, independent of climate, the location and internal architecture of carbonate deposits are not directly linked to sea-level position but, instead, are controlled by location of gently sloping substrates and processes of bypass. In contrast, if carbonate sediments are generated where substrates of low slope ( 15.6 cm/ky to ??? 2 cm/ky and overall relative sea level rose at rates of 17-21.4 cm/ky. Higher frequency sea-level rates were about 111 to more than 260 cm/ky, producing onlapping, fining- (deepening-) upward cycles. Decreasing accumulation rates resulted from decreasing surface area for shallow-water sediment production, drowning of shallow-water substrates, and complex sediment dispersal related to the archipelago setting. Typical systems tract and parasequence development should not be expected in "bypass ramp" settings; facies of onlapping strata do not track base level and are likely to be significantly different compared to onlapping strata associated with coastal onlap. Basal and upper DS2 reef megabreccias (indicating the transition from cool to warmer climatic conditions) were eroded from steep upslope positions and redeposited downslope onto areas of gentle substrate during rapid sea-level falls (> 22.7 cm/ky) of short duration. Such rapid sea-level falls and presence of steep slopes are not conducive to formation of forced regressive systems tracts composed of downstepping reef clinoforms. The DS3 reefal platform formed where shallow water coincided with gently sloping substrates created by earlier deposition. Slow progradation (0.39-1.45 km/my) is best explained by the lack of an extensive bank top, progressively falling sea level, and low productivity resulting from siliciclastic debris and excess nutrients shed from nearby volcanic islands. Although DS3 strata were deposited during a third-order relative sea-level cycle, a typical transgresse??e systems tract is not recognizable, indicating that the initial relative rise in sea level was too rapid (??? 19 cm/ky). Downstepping reefs, forming a forced regressive systems tract, were deposited during the relative sea-level fall at the end of DS3, indicating that relatively slow rates of fall (10 cm/ky or less) over favorable paleoslope conditions are conducive to generation of forced regressive systems tracts consisting of downstepping reef clinoforms. The TCC sequence consists of four shallow -water sedimentary cycles that were deposited during a 400 ky to 100 ky time span. Such shallow-water cycles, typical of many platforms, form only where shallow water intersects gently sloping substrates. The relative thicknesses of cycles (< 2 m to 15 m thick), magnitudes of relative sea-level fluctuations associated with each cycle (25-30 m), high rates of relative sea-level fluctuations (minimum of 25-120 cm/ky), and the widespread distribution of similar TCC cycles in the Mediterranean and elsewhere are supportive of a glacio-eustati

Sea Ice Characteristics and the Open-Linked Data World

NASA Astrophysics Data System (ADS)

Khalsa, S. J. S.; McGuinness, D. L.; Duerr, R.; Pulsifer, P. L.; Fox, P. A.; Thompson, C.; Yan, R.

2014-12-01

The audience for sea ice data sets has broadened dramatically over the past several decades. Initially the National Snow and Ice Data Center (NSIDC) sea ice products were used primarily by sea ice specialists. However, now they are in demand by researchers in many different domains and some are used by the public. This growth in the number and type of users has presented challenges to content providers aimed particularly at supporting interdisciplinary and multidisciplinary data use. In our experience, it is generally insufficient to simply make the data available as originally formatted. New audiences typically need data in different forms; forms that meet their needs, that work with their specific tools. Moreover, simple data reformatting is rarely enough. The data needs to be aggregated, transformed or otherwise converted into forms that better serve the needs of the new audience. The Semantic Sea Ice Interoperability Initiative (SSIII) is an NSF-funded research project aimed at making sea ice data more useful to more people using semantic technologies. The team includes domain and science data experts as well as knowledge representation and linked data experts. Beginning with a series of workshops involving members of the operations, sea ice research and modeling communities, as well as members of local communities in Alaska, a suite of ontologies describing the physical characteristics of sea ice have been developed and used to provide one of NSIDC's data sets, the operational Arctic sea ice charts obtained from the Canadian Ice Center, as open-linked data. These data extend nearly a decade into the past and can now be queried either directly through a publicly available SPARQL end point (for those who are familiar with open-linked data) or through a simple Open Geospatial Consortium (OGC) standards map-based query tool. Questions like "What were the characteristics (i.e., sea ice concentration, form and stage of development) of the sea ice in the region surrounding my ship/polar bear on date X?" can now be answered. This service may be of interest within the broad polar community - especially those who already are familiar with either open-linked data or OGC services. We seek feedback, collaborators, and users.

Noiseonomics: the relationship between ambient noise levels in the sea and global economic trends.

PubMed

Frisk, George V

2012-01-01

In recent years, the topic of noise in the sea and its effects on marine mammals has attracted considerable attention from both the scientific community and the general public. Since marine mammals rely heavily on acoustics as a primary means of communicating, navigating, and foraging in the ocean, any change in their acoustic environment may have an impact on their behavior. Specifically, a growing body of literature suggests that low-frequency, ambient noise levels in the open ocean increased approximately 3.3 dB per decade during the period 1950-2007. Here we show that this increase can be attributed primarily to commercial shipping activity, which in turn, can be linked to global economic growth. As a corollary, we conclude that ambient noise levels can be directly related to global economic conditions. We provide experimental evidence supporting this theory and discuss its implications for predicting future noise levels based on global economic trends.

Carbon choices determine US cities committed to futures below sea level

PubMed Central

Strauss, Benjamin H.; Kulp, Scott; Levermann, Anders

2015-01-01

Anthropogenic carbon emissions lock in long-term sea-level rise that greatly exceeds projections for this century, posing profound challenges for coastal development and cultural legacies. Analysis based on previously published relationships linking emissions to warming and warming to rise indicates that unabated carbon emissions up to the year 2100 would commit an eventual global sea-level rise of 4.3–9.9 m. Based on detailed topographic and population data, local high tide lines, and regional long-term sea-level commitment for different carbon emissions and ice sheet stability scenarios, we compute the current population living on endangered land at municipal, state, and national levels within the United States. For unabated climate change, we find that land that is home to more than 20 million people is implicated and is widely distributed among different states and coasts. The total area includes 1,185–1,825 municipalities where land that is home to more than half of the current population would be affected, among them at least 21 cities exceeding 100,000 residents. Under aggressive carbon cuts, more than half of these municipalities would avoid this commitment if the West Antarctic Ice Sheet remains stable. Similarly, more than half of the US population-weighted area under threat could be spared. We provide lists of implicated cities and state populations for different emissions scenarios and with and without a certain collapse of the West Antarctic Ice Sheet. Although past anthropogenic emissions already have caused sea-level commitment that will force coastal cities to adapt, future emissions will determine which areas we can continue to occupy or may have to abandon. PMID:26460051

Carbon choices determine US cities committed to futures below sea level.

PubMed

Strauss, Benjamin H; Kulp, Scott; Levermann, Anders

2015-11-03

Anthropogenic carbon emissions lock in long-term sea-level rise that greatly exceeds projections for this century, posing profound challenges for coastal development and cultural legacies. Analysis based on previously published relationships linking emissions to warming and warming to rise indicates that unabated carbon emissions up to the year 2100 would commit an eventual global sea-level rise of 4.3-9.9 m. Based on detailed topographic and population data, local high tide lines, and regional long-term sea-level commitment for different carbon emissions and ice sheet stability scenarios, we compute the current population living on endangered land at municipal, state, and national levels within the United States. For unabated climate change, we find that land that is home to more than 20 million people is implicated and is widely distributed among different states and coasts. The total area includes 1,185-1,825 municipalities where land that is home to more than half of the current population would be affected, among them at least 21 cities exceeding 100,000 residents. Under aggressive carbon cuts, more than half of these municipalities would avoid this commitment if the West Antarctic Ice Sheet remains stable. Similarly, more than half of the US population-weighted area under threat could be spared. We provide lists of implicated cities and state populations for different emissions scenarios and with and without a certain collapse of the West Antarctic Ice Sheet. Although past anthropogenic emissions already have caused sea-level commitment that will force coastal cities to adapt, future emissions will determine which areas we can continue to occupy or may have to abandon.

MHC Class II Activation and Interferon-γ Mediate the Inhibition of Neutrophils and Eosinophils by Staphylococcal Enterotoxin Type A (SEA).

PubMed

Ferreira-Duarte, Ana P; Pinheiro-Torres, Anelize S; Anhê, Gabriel F; Condino-Neto, Antônio; Antunes, Edson; DeSouza, Ivani A

2017-01-01

Staphylococcal enterotoxins are classified as superantigens that act by linking T-cell receptor with MHC class II molecules, which are expressed on classical antigen-presenting cells (APC). Evidence shows that MHC class II is also expressed in neutrophils and eosinophils. This study aimed to investigate the role of MHC class II and IFN-γ on chemotactic and adhesion properties of neutrophils and eosinophils after incubation with SEA. Bone marrow (BM) cells obtained from BALB/c mice were resuspended in culture medium, and incubated with SEA (3-30 ng/ml; 1-4 h), after which chemotaxis and adhesion were evaluated. Incubation with SEA significantly reduced the chemotactic and adhesive responses in BM neutrophils activated with IL-8 (200 ng/ml). Likewise, SEA significantly reduced the chemotactic and adhesive responses of BM eosinophils activated with eotaxin (300 ng/ml). The inhibitory effects of SEA on cell chemotaxis and adhesion were fully prevented by prior incubation with an anti-MHC class II blocking antibody (2 μg/ml). SEA also significantly reduced the intracellular Ca 2+ levels in IL-8- and eotaxin-activated BM cells. No alterations of MAC-1, VLA4, and LFA-1α expressions were observed after SEA incubation. In addition, SEA elevated by 3.5-fold ( P < 0.05) the INF-γ levels in BM cells. Incubation of BM leukocytes with IFN-γ (10 ng/ml, 2 h) reduced both neutrophil and eosinophil chemotaxis and adhesion, which were prevented by prior incubation with anti-MHC class II antibody (2 μg/ml). In conclusion, SEA inhibits neutrophil and eosinophil by MHC class II-dependent mechanism, which may be modulated by concomitant release of IFN-γ.

Sea Level Change due to Time-Dependent Long-Wavelength Dynamic Topography Inferred from Plate Tectonic Reconstructions

NASA Astrophysics Data System (ADS)

Conrad, Clinton P.; Steinberger, Bernhard; Torsvik, Trond H.

2017-04-01

Earth's surface is deflected vertically by stresses associated with convective mantle flow. Although dynamic topography is important for both sea level change and continental uplift and subsidence, the time history of dynamic topography is difficult to constrain because the time-dependence of mantle flow is not known. However, the motions of the tectonic plates contain information about the mantle flow patterns that drive them. In particular, we show that the longest wavelengths of mantle flow are tightly linked to the dipole and quadrupole moments (harmonic degrees 1 and 2) of plate motions. This coupling allows us to infer patterns of long-wavelength mantle flow, and the associated dynamic topography, from tectonic plate motions. After calibrating this linkage using models of present-day mantle flow, we can use reconstructions of global plate motions to infer the basic patterns of long-wavelength dynamic topography back to 250 Ma. We find relatively stable dynamic uplift persists above large-scale mantle upwelling beneath Africa and the Central Pacific. Regions of major downwelling encircled the periphery of these stable upwellings, alternating between primarily east-west and north-south orientations. The amplitude of long-wavelength dynamic topography was likely largest in the Cretaceous, when global plate motions were fastest. Continental motions over this time-evolving dynamic topography predict patterns of continental uplift and subsidence that are confirmed by geological observations of continental surfaces relative to sea level. Net uplift or subsidence of the global seafloor can also induce eustatic sea level changes. We infer that dispersal of the Pangean supercontinent away from stable upwelling beneath Africa may have exposed the seafloor to an increasingly larger area of growing positive dynamic topography during the Mesozoic. This net uplift of the seafloor caused 60 m of sea level rise during the Triassic and Jurassic, ceasing in the Cenozoic once continents fully override degree-2 downwellings. These sea level changes represent a significant component of the estimated 200 m of sea level variations during the Phanerozoic, which exhibit a similar temporal pattern.

Abrupt Bølling warming and ice saddle collapse contributions to the Meltwater Pulse 1a rapid sea level rise: North American MWP1a Contribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gregoire, Lauren J.; Otto-Bliesner, Bette; Valdes, Paul J.

Elucidating the source(s) of Meltwater Pulse 1a, the largest rapid sea level rise caused by ice melt (14-18 m in less than 340 years, 14,600 years ago), is important for understanding mechanisms of rapid ice melt and the links with abrupt climate change. Here we quantify how much and by what mechanisms the North American ice sheet could have contributed to Meltwater Pulse 1a, by driving an ice sheet model with two transient climate simulations of the last 21,000 years. Ice sheet perturbed physics ensembles were run to account for model uncertainties, constraining ice extent and volume with reconstructions ofmore » 21,000 years ago to present. We determine that the North American ice sheet produced 3-4 m global mean sea level rise in 340 years due to the abrupt Bølling warming, but this response is amplified to 5-6 m when it triggers the ice sheet saddle collapse.« less

Abrupt Bølling warming and ice saddle collapse contributions to the Meltwater Pulse 1a rapid sea level rise: North American MWP1a Contribution

DOE PAGES

Gregoire, Lauren J.; Otto-Bliesner, Bette; Valdes, Paul J.; ...

2016-08-23

Elucidating the source(s) of Meltwater Pulse 1a, the largest rapid sea level rise caused by ice melt (14-18 m in less than 340 years, 14,600 years ago), is important for understanding mechanisms of rapid ice melt and the links with abrupt climate change. Here we quantify how much and by what mechanisms the North American ice sheet could have contributed to Meltwater Pulse 1a, by driving an ice sheet model with two transient climate simulations of the last 21,000 years. Ice sheet perturbed physics ensembles were run to account for model uncertainties, constraining ice extent and volume with reconstructions ofmore » 21,000 years ago to present. We determine that the North American ice sheet produced 3-4 m global mean sea level rise in 340 years due to the abrupt Bølling warming, but this response is amplified to 5-6 m when it triggers the ice sheet saddle collapse.« less

Deep-Sea Microbes: Linking Biogeochemical Rates to -Omics Approaches

NASA Astrophysics Data System (ADS)

Herndl, G. J.; Sintes, E.; Bayer, B.; Bergauer, K.; Amano, C.; Hansman, R.; Garcia, J.; Reinthaler, T.

2016-02-01

Over the past decade substantial progress has been made in determining deep ocean microbial activity and resolving some of the enigmas in understanding the deep ocean carbon flux. Also, metagenomics approaches have shed light onto the dark ocean's microbes but linking -omics approaches to biogeochemical rate measurements are generally rare in microbial oceanography and even more so for the deep ocean. In this presentation, we will show by combining metagenomics, -proteomics and biogeochemical rate measurements on the bulk and single-cell level that deep-sea microbes exhibit characteristics of generalists with a large genome repertoire, versatile in utilizing substrate as revealed by metaproteomics. This is in striking contrast with the apparently rather uniform dissolved organic matter pool in the deep ocean. Combining the different -omics approaches with metabolic rate measurements, we will highlight some major inconsistencies and enigmas in our understanding of the carbon cycling and microbial food web structure in the dark ocean.

Possible connections of the opposite trends in Arctic and Antarctic sea-ice cover.

PubMed

Yu, Lejiang; Zhong, Shiyuan; Winkler, Julie A; Zhou, Mingyu; Lenschow, Donald H; Li, Bingrui; Wang, Xianqiao; Yang, Qinghua

2017-04-05

Sea ice is an important component of the global climate system and a key indicator of climate change. A decreasing trend in Arctic sea-ice concentration is evident in recent years, whereas Antarctic sea-ice concentration exhibits a generally increasing trend. Various studies have investigated the underlying causes of the observed trends for each region, but possible linkages between the regional trends have not been studied. Here, we hypothesize that the opposite trends in Arctic and Antarctic sea-ice concentration may be linked, at least partially, through interdecadal variability of the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). Although evaluation of this hypothesis is constrained by the limitations of the sea-ice cover record, preliminary statistical analyses of one short-term and two long-term time series of observed and reanalysis sea-ice concentrations data suggest the possibility of the hypothesized linkages. For all three data sets, the leading mode of variability of global sea-ice concentration is positively correlated with the AMO and negatively correlated with the PDO. Two wave trains related to the PDO and the AMO appear to produce anomalous surface-air temperature and low-level wind fields in the two polar regions that contribute to the opposite changes in sea-ice concentration.

Possible connections of the opposite trends in Arctic and Antarctic sea-ice cover

PubMed Central

Yu, Lejiang; Zhong, Shiyuan; Winkler, Julie A.; Zhou, Mingyu; Lenschow, Donald H.; Li, Bingrui; Wang, Xianqiao; Yang, Qinghua

2017-01-01

Sea ice is an important component of the global climate system and a key indicator of climate change. A decreasing trend in Arctic sea-ice concentration is evident in recent years, whereas Antarctic sea-ice concentration exhibits a generally increasing trend. Various studies have investigated the underlying causes of the observed trends for each region, but possible linkages between the regional trends have not been studied. Here, we hypothesize that the opposite trends in Arctic and Antarctic sea-ice concentration may be linked, at least partially, through interdecadal variability of the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). Although evaluation of this hypothesis is constrained by the limitations of the sea-ice cover record, preliminary statistical analyses of one short-term and two long-term time series of observed and reanalysis sea-ice concentrations data suggest the possibility of the hypothesized linkages. For all three data sets, the leading mode of variability of global sea-ice concentration is positively correlated with the AMO and negatively correlated with the PDO. Two wave trains related to the PDO and the AMO appear to produce anomalous surface-air temperature and low-level wind fields in the two polar regions that contribute to the opposite changes in sea-ice concentration. PMID:28378830

Identifying Climate Model Teleconnection Mechanisms Between Arctic Sea Ice Loss and Mid-Latitude Winter Storms

NASA Astrophysics Data System (ADS)

Kravitz, B.; Mills, C.; Rasch, P. J.; Wang, H.; Yoon, J. H.

2016-12-01

The role of Arctic amplification, including observed decreases in sea ice concentration, thickness, and extent, with potential for exciting downstream atmospheric responses in the mid-latitudes, is a timely issue. We identify the role of the regionality of autumn sea ice loss on downstream mid-latitude responses using engineering methodologies adapted to climate modeling, which allow for multiple Arctic sea regions to be perturbed simultaneously. We evaluate downstream responses in various climate fields (e.g., temperature, precipitation, cloud cover) associated with perturbations in the Beaufort/Chukchi Seas and the Kara/Barents Seas. Simulations suggest that the United States response is primarily linked to sea ice changes in the Beaufort/Chukchi Seas, whereas Eurasian response is primarily due to Kara/Barents sea ice coverage changes. Downstream effects are most prominent approximately 6-10 weeks after the initial perturbation (sea ice loss). Our findings suggest that winter mid-latitude storms (connected to the so-called "Polar Vortex") are linked to sea ice loss in particular areas, implying that further sea ice loss associated with climate change will exacerbate these types of extreme events.

The influence of global sea surface temperature variability on the large-scale land surface temperature

NASA Astrophysics Data System (ADS)

Tyrrell, Nicholas L.; Dommenget, Dietmar; Frauen, Claudia; Wales, Scott; Rezny, Mike

2015-04-01

In global warming scenarios, global land surface temperatures () warm with greater amplitude than sea surface temperatures (SSTs), leading to a land/sea warming contrast even in equilibrium. Similarly, the interannual variability of is larger than the covariant interannual SST variability, leading to a land/sea contrast in natural variability. This work investigates the land/sea contrast in natural variability based on global observations, coupled general circulation model simulations and idealised atmospheric general circulation model simulations with different SST forcings. The land/sea temperature contrast in interannual variability is found to exist in observations and models to a varying extent in global, tropical and extra-tropical bands. There is agreement between models and observations in the tropics but not the extra-tropics. Causality in the land-sea relationship is explored with modelling experiments forced with prescribed SSTs, where an amplification of the imposed SST variability is seen over land. The amplification of to tropical SST anomalies is due to the enhanced upper level atmospheric warming that corresponds with tropical moist convection over oceans leading to upper level temperature variations that are larger in amplitude than the source SST anomalies. This mechanism is similar to that proposed for explaining the equilibrium global warming land/sea warming contrast. The link of the to the dominant mode of tropical and global interannual climate variability, the El Niño Southern Oscillation (ENSO), is found to be an indirect and delayed connection. ENSO SST variability affects the oceans outside the tropical Pacific, which in turn leads to a further, amplified and delayed response of.

Stratigraphic architecture of back-filled incised-valley systems: Pennsylvanian-Permian lower Cutler beds, Utah, USA

NASA Astrophysics Data System (ADS)

Wakefield, Oliver J. W.; Mountney, Nigel P.

2013-12-01

The Pennsylvanian to Permian lower Cutler beds collectively form the lowermost stratigraphic unit of the Cutler Group in the Paradox Basin, southeast Utah. The lower Cutler beds represent a tripartite succession comprising lithofacies assemblages of aeolian, fluvial and shallow-marine origin, in near equal proportion. The succession results from a series of transgressive-regressive cycles, driven by repeated episodes of climatic variation and linked changes in relative sea-level. Relative sea-level changes created a number of incised-valleys, each forming through fluvial incision during lowered base-level. Aeolian dominance during periods of relative sea-level lowstand aids incised-valley identification as the erosive bounding surface juxtaposes incised-valley infill against stacked aeolian faces. Relative sea-level rises resulted in back-flooding of the incised-valleys and their infill via shallow-marine and estuarine processes. Back-flooded valleys generated marine embayments within which additional local accommodation was exploited. Back-filling is characterised by a distinctive suite of lithofacies arranged into a lowermost, basal fill of fluvial channel and floodplain architectural elements, passing upwards into barform elements with indicators of tidal influence, including inclined heterolithic strata and reactivation surfaces. The incised-valley fills are capped by laterally extensive and continuous marine limestone elements that record the drowning of the valleys and, ultimately, flooding and accumulation across surrounding interfluves (transgressive surface). Limestone elements are characterised by an open-marine fauna and represent the preserved expression of maximum transgression.

Geological and climatic changes in quaternary shaped the evolutionary history of Calibrachoa heterophylla, an endemic South-Atlantic species of petunia

PubMed Central

2013-01-01

Background The glacial and interglacial cycles that characterized the Quaternary greatly affected the distribution and genetic diversity of plants. In the Neotropics, few phylogeographic studies have focused on coastal species outside of the Atlantic Rainforest. Climatic and sea level changes during the Quaternary played an important role in the evolutionary history of many organisms found in coastal regions. To contribute to a better understanding of plant evolution in this environment in Southern South America, we focused on Calibrachoa heterophylla (Solanaceae), an endemic and vulnerable wild petunia species from the South Atlantic Coastal Plain (SACP). Results We assessed DNA sequences from two cpDNA intergenic spacers and analyzed them using a phylogeographic approach. The present phylogeographic study reveals the influence of complex geologic and climatic events on patterns of genetic diversification. The results indicate that C. heterophylla originated inland and subsequently colonized the SACP; the data show that the inland haplogroup is more ancient than the coastal one and that the inland was not affected by sea level changes in the Quaternary. The major diversification of C. heterophylla that occurred after 0.4 Myr was linked to sea level oscillations in the Quaternary, and any diversification that occurred before this time was obscured by marine transgressions that occurred before the coastal sand barrier’s formation. Results of the Bayesian skyline plot showed a recent population expansion detected in C. heterophylla seems to be related to an increase in temperature and humidity that occurred at the beginning of the Holocene. Conclusions The geographic clades have been formed when the coastal plain was deeply dissected by paleochannels and these correlate very well with the distributional limits of the clades. The four major sea transgressions formed a series of four sand barriers parallel to the coast that progressively increased the availability of coastal areas after the regressions and that may have promoted the geographic structuring of genetic diversity observed today. The recent population expansion for the entire species may be linked with the event of marine regression after the most recent sea transgression at ~5 kya. PMID:23987105

Contemporary genetic structure and postglacial demographic history of the black scorpionfish, Scorpaena porcus, in the Mediterranean and the Black Seas.

PubMed

Boissin, E; Micu, D; Janczyszyn-Le Goff, M; Neglia, V; Bat, L; Todorova, V; Panayotova, M; Kruschel, C; Macic, V; Milchakova, N; Keskin, Ç; Anastasopoulou, A; Nasto, I; Zane, L; Planes, S

2016-05-01

Understanding the distribution of genetic diversity in the light of past demographic events linked with climatic shifts will help to forecast evolutionary trajectories of ecosystems within the current context of climate change. In this study, mitochondrial sequences and microsatellite loci were analysed using traditional population genetic approaches together with Bayesian dating and the more recent approximate Bayesian computation scenario testing. The genetic structure and demographic history of a commercial fish, the black scorpionfish, Scorpaena porcus, was investigated throughout the Mediterranean and Black Seas. The results suggest that the species recently underwent population expansions, in both seas, likely concomitant with the warming period following the Last Glacial Maximum, 20 000 years ago. A weak contemporaneous genetic differentiation was identified between the Black Sea and the Mediterranean Sea. However, the genetic diversity was similar for populations of the two seas, suggesting a high number of colonizers entered the Black Sea during the interglacial period and/or the presence of a refugial population in the Black Sea during the glacial period. Finally, within seas, an east/west genetic differentiation in the Adriatic seems to prevail, whereas the Black Sea does not show any structured spatial genetic pattern of its population. Overall, these results suggest that the Black Sea is not that isolated from the Mediterranean, and both seas revealed similar evolutionary patterns related to climate change and changes in sea level. © 2016 John Wiley & Sons Ltd.

Combining GRACE and Altimetry to solve for present day mass changes and GIA

NASA Astrophysics Data System (ADS)

Rietbroek, R.; Lück, C.; Uebbing, B.; Kusche, J.; King, M. A.

2017-12-01

Past and present day sea level rise is closely linked to geoid and surface deformation changes from the ongoing glacial isostatic adjustment (GIA). Sea level, as detected by radar altimetry, senses the radial deformation of the ocean floor as mantle material slowly flows back to the locations of the former glacial domes. This manifests itself as a net subsidence when averaged over the entire ocean, but can regionally be seen as an uplift for locations close to the former ice sheets. Furthermore, mass driven sea level as derived from GRACE, is even more sensitive to GIA induced mass redistribution in the solid Earth. Consequently, errors in GIA corrections, most notably errors in mantle viscosity and ice histories, have a different leverage on regional sea level estimates from GRACE and altimetry. In this study, we discuss the abilities of a GRACE-altimetry combination to co-estimate GIA corrections together with present day contributors to sea level, rather than simply prescribing a GIA correction from a model. The data is combined in a joint inversion scheme which makes use of spatial patterns to parameterize present day loading effects and GIA. We show that the GRACE-altimetry combination requires constraints, but generally steers the Antarctic GIA signal towards a weaker present day signal in Antarctica compared to a ICE5-G(VM2) derived model. Furthermore, in light of the aging GRACE mission, we show sensitivity studies of how well one could estimate GIA corrections when using other low earth orbiters such as SWARM or CHAMP. Finally, we show whether the Antarctic GNSS station network may be useful in separating GIA from present day mass signals in this type of inversion schemes.

Certified reference materials for testing of the presence/absence of Staphylococcus aureus enterotoxin A (SEA) in cheese.

PubMed

Zeleny, Reinhard; Nia, Yacine; Schimmel, Heinz; Mutel, Isabelle; Hennekinne, Jacques-Antoine; Emteborg, Håkan; Charoud-Got, Jean; Auvray, Frédéric

2016-08-01

Staphylococcal enterotoxins (SEs) account for a substantial number of food-poisoning outbreaks. European legislation (Commission Regulation 1441/2007) stipulates the reference procedure for SE analysis in milk and dairy products, which is based on extraction, dialysis concentration and immunochemical detection using one of two approved assays (VIDAS(®) SET2, Ridascreen(®) SET Total). However, certified reference materials (CRMs) are lacking to support laboratories in performing reliable detection of Staphylococcus aureus enterotoxin A (SEA) in relevant matrices at sub-nanogram per gram levels. The certification of a set of three reference materials (blank and two SEA-containing materials) for testing of the presence/absence of SEA in cheese is described. The reference procedure was applied in an intercomparison with 15 laboratories, and results were reported in a qualitative manner (presence or absence of SEA in the sample). No false-negative or false-positive results were obtained. The certified values were stated as diagnostic specificity (blank material) or diagnostic sensitivity (SEA-containing materials) and were 100 % in all cases. Stability studies demonstrated suitable material stability when stored cooled or frozen. An in-house study on the recovery of SEA in the cheese materials using a double-sandwich enzyme-linked immunosorbent assay (ELISA) revealed comparable recovery values of around 45 % at the two spiking levels and in both the SEA-containing CRMs as well as blank CRM freshly spiked prior to analysis. The values were also comparable over time and among different analysts. The materials provide valuable support to laboratories for method validation and method performance verification and will increase the reliability of measuring SEA in cheese.

A Possible Link Between Winter Arctic Sea Ice Decline and a Collapse of the Beaufort High?

NASA Astrophysics Data System (ADS)

Petty, Alek A.

2018-03-01

A new study by Moore et al. (2018, https://doi.org/10.1002/2017GL076446) highlights a collapse of the anticyclonic "Beaufort High" atmospheric circulation over the western Arctic Ocean in the winter of 2017 and an associated reversal of the sea ice drift through the southern Beaufort Sea (eastward instead of the predominantly westward circulation). The authors linked this to the loss of sea ice in the Barents Sea, anomalous warming over the region, and the intrusion of low-pressure cyclones along the eastern Arctic. In this commentary we discuss the significance of this observation, the challenges associated with understanding these possible linkages, and some of the alternative hypotheses surrounding the impacts of winter Arctic sea ice loss.

Integrated stratigraphy of the Ammer section, Northern Alpine Foreland Basin, Germany: examining the age and origin of the earliest deposits in the Paratethys

NASA Astrophysics Data System (ADS)

van der boon, Annique; Beniest, Anouk; Ciurej, Agnieszka; Gaździcka, Elzbieta; Grothe, Arjen; Sachsenhofer, Reinhard; Langereis, Cor; Krijgsman, Wout

2017-04-01

The Northern Alpine Foreland Basin (NAFB) was an arm of the epicontinental Paratethys Sea during the Oligocene. The Oligocene and Miocene deposits in the Paratethys are linked to a long-term phase of episodically oxygen-poor conditions. This led to the deposition of organic-rich shales over millions of years, which nowadays make up the most important part of the source rocks of the Paratethys. At the Eocene-Oligocene transition (EOT), global sea-level dropped by an estimated 70 meters. Both this eustatic sea-level drop and large scale tectonic movements are inferred as mechanisms for restriction of connections to the global ocean and consecutive basin isolation in the Paratethys. Discriminating sea-level effects from tectonic processes requires accurate dating of Oligocene deposits. Here, we use an integrated stratigraphic approach, combining different biostratigraphic techniques with magnetostratigraphy and organic geochemistry, to determine the age of the Tonmergel formation along the Ammer River in southern Germany. The Tonmergel formation is usually interpreted as the equivalent of the Paratethys Lower Oligocene organic-rich shales. The age of deposits (typically mapped as Oligocene) in this region is currently under debate, as some studies suggest they might be late Eocene in age. The absence of marker species for biostratigraphic zones, the scarcity of ash layers and the lack of formally defined boundaries of nannoplankton zones around the Eocene-Oligocene interval (e.g. the NP19-20/NP21 boundary) further obstruct accurate dating. Here we present the results of our magnetostratigraphy, biostratigraphy and organic geochemistry and interpret whether any lithological changes can be linked to climate forcing or tectonic processes. Based on the combined results of our study we provide several options for the age of these earliest Paratethys deposits, and discuss our preferred option.

Southern Ocean Climate and Sea Ice Anomalies Associated with the Southern Oscillation

NASA Technical Reports Server (NTRS)

Kwok, R.; Comiso, J. C.

2001-01-01

The anomalies in the climate and sea ice cover of the Southern Ocean and their relationships with the Southern Oscillation (SO) are investigated using a 17-year of data set from 1982 through 1998. We correlate the polar climate anomalies with the Southern Oscillation index (SOI) and examine the composites of these anomalies under the positive (SOI > 0), neutral (0 > SOI > -1), and negative (SOI < -1) phases of SOL The climate data set consists of sea-level pressure, wind, surface air temperature, and sea surface temperature fields, while the sea ice data set describes its extent, concentration, motion, and surface temperature. The analysis depicts, for the first time, the spatial variability in the relationship of the above variables and the SOL The strongest correlation between the SOI and the polar climate anomalies are found in the Bellingshausen, Amundsen and Ross sea sectors. The composite fields reveal anomalies that are organized in distinct large-scale spatial patterns with opposing polarities at the two extremes of SOI, and suggest oscillating climate anomalies that are closely linked to the SO. Within these sectors, positive (negative) phases of the SOI are generally associated with lower (higher) sea-level pressure, cooler (warmer) surface air temperature, and cooler (warmer) sea surface temperature in these sectors. Associations between these climate anomalies and the behavior of the Antarctic sea ice cover are clearly evident. Recent anomalies in the sea ice cover that are apparently associated with the SOI include: the record decrease in the sea ice extent in the Bellingshausen Sea from mid- 1988 through early 199 1; the relationship between Ross Sea SST and ENSO signal, and reduced sea ice concentration in the Ross Sea; and, the shortening of the ice season in the eastern Ross Sea, Amundsen Sea, far western Weddell Sea, and the lengthening of the ice season in the western Ross Sea, Bellingshausen Sea and central Weddell Sea gyre over the period 1988-1994. Four ENSO episodes over the last 17 years contributed to a negative mean in the SOI (-0.5). In each of these episodes, significant retreats in the Bellingshausen/Amundsen Sea were observed providing direct confirmation of the impact of SO on the Antarctic sea ice cover.

Evaporation estimates from the Dead Sea and their implications on its water balance

NASA Astrophysics Data System (ADS)

Oroud, Ibrahim M.

2011-12-01

The Dead Sea (DS) is a terminal hypersaline water body situated in the deepest part of the Jordan Valley. There is a growing interest in linking the DS to the open seas due to severe water shortages in the area and the serious geological and environmental hazards to its vicinity caused by the rapid level drop of the DS. A key issue in linking the DS with the open seas would be an accurate determination of evaporation rates. There exist large uncertainties of evaporation estimates from the DS due to the complex feedback mechanisms between meteorological forcings and thermophysical properties of hypersaline solutions. Numerous methods have been used to estimate current and historical (pre-1960) evaporation rates, with estimates differing by ˜100%. Evaporation from the DS is usually deduced indirectly using energy, water balance, or pan methods with uncertainty in many parameters. Accumulated errors resulting from these uncertainties are usually pooled into the estimates of evaporation rates. In this paper, a physically based method with minimum empirical parameters is used to evaluate historical and current evaporation estimates from the DS. The more likely figures for historical and current evaporation rates from the DS were 1,500-1,600 and 1,200-1,250 mm per annum, respectively. Results obtained are congruent with field observations and with more elaborate procedures.

Future increases in Arctic precipitation linked to local evaporation and sea-ice retreat.

PubMed

Bintanja, R; Selten, F M

2014-05-22

Precipitation changes projected for the end of the twenty-first century show an increase of more than 50 per cent in the Arctic regions. This marked increase, which is among the highest globally, has previously been attributed primarily to enhanced poleward moisture transport from lower latitudes. Here we use state-of-the-art global climate models to show that the projected increases in Arctic precipitation over the twenty-first century, which peak in late autumn and winter, are instead due mainly to strongly intensified local surface evaporation (maximum in winter), and only to a lesser degree due to enhanced moisture inflow from lower latitudes (maximum in late summer and autumn). Moreover, we show that the enhanced surface evaporation results mainly from retreating winter sea ice, signalling an amplified Arctic hydrological cycle. This demonstrates that increases in Arctic precipitation are firmly linked to Arctic warming and sea-ice decline. As a result, the Arctic mean precipitation sensitivity (4.5 per cent increase per degree of temperature warming) is much larger than the global value (1.6 to 1.9 per cent per kelvin). The associated seasonally varying increase in Arctic precipitation is likely to increase river discharge and snowfall over ice sheets (thereby affecting global sea level), and could even affect global climate through freshening of the Arctic Ocean and subsequent modulations of the Atlantic meridional overturning circulation.

Enhanced East Pacific Rise hydrothermal activity during the last two glacial terminations

NASA Astrophysics Data System (ADS)

Lund, D. C.; Asimow, P. D.; Farley, K. A.; Rooney, T. O.; Seeley, E.; Jackson, E. W.; Durham, Z. M.

2016-01-01

Mid-ocean ridge magmatism is driven by seafloor spreading and decompression melting of the upper mantle. Melt production is apparently modulated by glacial-interglacial changes in sea level, raising the possibility that magmatic flux acts as a negative feedback on ice-sheet size. The timing of melt variability is poorly constrained, however, precluding a clear link between ridge magmatism and Pleistocene climate transitions. Here we present well-dated sedimentary records from the East Pacific Rise that show evidence of enhanced hydrothermal activity during the last two glacial terminations. We suggest that glacial maxima and lowering of sea level caused anomalous melting in the upper mantle and that the subsequent magmatic anomalies promoted deglaciation through the release of mantle heat and carbon at mid-ocean ridges.

Identification of Quantitative Trait Loci for Resistance to RSIVD in Red Sea Bream (Pagrus major).

PubMed

Sawayama, Eitaro; Tanizawa, Shiho; Kitamura, Shin-Ichi; Nakayama, Kei; Ohta, Kohei; Ozaki, Akiyuki; Takagi, Motohiro

2017-12-01

Red sea bream iridoviral disease (RSIVD) is a major viral disease in red sea bream farming in Japan. Previously, we identified one candidate male individual of red sea bream that was significantly associated with convalescent individuals after RSIVD. The purpose of this study is to identify the quantitative trait loci (QTL) linked to the RSIVD-resistant trait for future marker-assisted selection (MAS). Two test families were developed using the candidate male in 2014 (Fam-2014) and 2015 (Fam-2015). These test families were challenged with RSIV, and phenotypes were evaluated. Then, de novo genome sequences of red sea bream were obtained through next-generation sequencing, and microsatellite markers were searched and selected for linkage map construction. One immune-related gene, MHC class IIβ, was also used for linkage map construction. Of the microsatellite markers searched, 148 and 197 were mapped on 23 and 27 linkage groups in the female and male linkage maps, respectively, covering approximately 65% of genomes in both sexes. One QTL linked to an RSIVD-resistant trait was found in linkage group 2 of the candidate male in Fam-2014, and the phenotypic variance of the QTL was 31.1%. The QTL was closely linked to MHC class IIβ. Moreover, the QTL observed in Fam-2014 was also significantly linked to an RSIVD-resistant trait in the candidate male of Fam-2015. Our results suggest that the RSIVD-resistant trait in the candidate male was controlled by one major QTL closely linked to the MHC class IIβ gene and could be useful for MAS of red sea bream.

Effects of sea-ice extent and krill or salp dominance on the Antarctic food web

NASA Astrophysics Data System (ADS)

Loeb, V.; Siegel, V.; Holm-Hansen, O.; Hewitt, R.; Fraser, W.; Trivelpiece, W.; Trivelpiece, S.

1997-06-01

Krill (Euphausia superba) provide a direct link between primary producers and higher trophic levels in the Antarctic marine food web. The pelagic tunicate Salpa thompsoni can also be important during spring and summer through the formation of extensive and dense blooms. Although salps are not a major dietary item for Antarctic vertebrate predators,, their blooms can affect adult krill reproduction and survival of krill larvae. Here we provide data from 1995 and 1996 that support hypothesized relationships between krill, salps and region-wide sea-ice conditions,. We have assessed salp consumption as a proportion of net primary production, and found correlations between herbivore densities and integrated chlorophyll-a that indicate that there is a degree of competition between krill and salps. Our analysis of the relationship between annual sea-ice cover and a longer time series of air temperature measurements, indicates a decreased frequency of winters with extensive sea-ice development over the last five decades. Our data suggest that decreased krill availability may affect the levels of their vertebrate predators. Regional warming and reduced krill abundance therefore affect the marine food web and krill resource management.

Cosmogenic Secondary Radiation from a Nearby Supernova

NASA Astrophysics Data System (ADS)

Overholt, Andrew

2017-01-01

Increasing evidence has been found for multiple supernovae within 100 pc of the solar system. Supernovae produce large amounts of cosmic rays which upon striking Earth's atmosphere, produce a cascade of secondary particles. Among these cosmic ray secondaries are neutrons and muons, which penetrate far within the atmosphere to sea level and even below sea level. Muons and neutrons are both forms of ionizing radiation which have been linked to increases in cancer, congenital malformations, and other maladies. This work focuses on the impact of muons, as they penetrate into ocean water to impact the lowest levels of the aquatic food chain. We have used monte carlo simulations (CORSIKA, MCNPx, and FLUKA) to determine the ionizing radiation dose due to cosmic ray secondaries. This information shows that although most astrophysical events do not supply the necessary radiation flux to prove dangerous; there may be other impacts such as an increase to mutation rate.

Sea ice roughness: the key for predicting Arctic summer ice albedo

NASA Astrophysics Data System (ADS)

Landy, J.; Ehn, J. K.; Tsamados, M.; Stroeve, J.; Barber, D. G.

2017-12-01

Although melt ponds on Arctic sea ice evolve in stages, ice with smoother surface topography typically allows the pond water to spread over a wider area, reducing the ice-albedo and accelerating further melt. Building on this theory, we simulated the distribution of meltwater on a range of statistically-derived topographies to develop a quantitative relationship between premelt sea ice surface roughness and summer ice albedo. Our method, previously applied to ICESat observations of the end-of-winter sea ice roughness, could account for 85% of the variance in AVHRR observations of the summer ice-albedo [Landy et al., 2015]. Consequently, an Arctic-wide reduction in sea ice roughness over the ICESat operational period (from 2003 to 2008) explained a drop in ice-albedo that resulted in a 16% increase in solar heat input to the sea ice cover. Here we will review this work and present new research linking pre-melt sea ice surface roughness observations from Cryosat-2 to summer sea ice albedo over the past six years, examining the potential of winter roughness as a significant new source of sea ice predictability. We will further evaluate the possibility for high-resolution (kilometre-scale) forecasts of summer sea ice albedo from waveform-level Cryosat-2 roughness data in the landfast sea ice zone of the Canadian Arctic. Landy, J. C., J. K. Ehn, and D. G. Barber (2015), Albedo feedback enhanced by smoother Arctic sea ice, Geophys. Res. Lett., 42, 10,714-10,720, doi:10.1002/2015GL066712.

Southern Ocean Climate and Sea Ice Anomalies Associated with the Southern Oscillation.

NASA Astrophysics Data System (ADS)

Kwok, R.; Comiso, J. C.

2002-03-01

The anomalies in the climate and sea ice cover of the Southern Ocean and their relationships with the Southern Oscillation (SO) are investigated using a 17-yr dataset from 1982 to 1998. The polar climate anomalies are correlated with the Southern Oscillation index (SOI) and the composites of these anomalies are examined under the positive (SOI > 0), neutral (0 > SOI > 1), and negative (SOI < 1) phases of SOI. The climate dataset consists of sea level pressure, wind, surface air temperature, and sea surface temperature fields, while the sea ice dataset describes its extent, concentration, motion, and surface temperature. The analysis depicts, for the first time, the spatial variability in the relationship of the above variables with the SOI. The strongest correlation between the SOI and the polar climate anomalies are found in the Bellingshausen, Amundsen, and Ross Seas. The composite fields reveal anomalies that are organized in distinct large-scale spatial patterns with opposing polarities at the two extremes of SOI, and suggest oscillations that are closely linked to the SO. Within these sectors, positive (negative) phases of the SOI are generally associated with lower (higher) sea level pressure, cooler (warmer) surface air temperature, and cooler (warmer) sea surface temperature in these sectors. Associations between these climate anomalies and the behavior of the Antarctic sea ice cover are evident. Recent anomalies in the sea ice cover that are clearly associated with the SOI include the following: the record decrease in the sea ice extent in the Bellingshausen Sea from mid-1988 to early 1991; the relationship between Ross Sea SST and the ENSO signal, and reduced sea ice concentration in the Ross Sea; and the shortening of the ice season in the eastern Ross Sea, Amundsen Sea, far western Weddell Sea and lengthening of the ice season in the western Ross Sea, Bellinghausen Sea, and central Weddell Sea gyre during the period 1988-94. Four ENSO episodes over the last 17 years contributed to a negative mean in the SOI (0.5). In each of these episodes, significant retreats in ice cover of the Bellingshausen and Amundsen Seas were observed showing a unique association of this region of the Antarctic with the Southern Oscillation.

Glacial cycles drive variations in the production of oceanic crust

NASA Astrophysics Data System (ADS)

Crowley, J. W.; Katz, R. F.; Langmuir, C. H.; Huybers, P. J.

2013-12-01

Changes in sea level accompanying glacial cycles affect the static pressure within the asthenosphere; these variations could modulate melting rates beneath the mid-ocean ridge system as well as crustal thickness. These effects can be investigated and quantified using models of ridges based on conservation of mass, momentum, energy, and composition for two phases (magma & mantle) and two thermodynamic components (enriched & depleted). The models predict that the sensitivity of crustal thickness to oscillations in sea-level depends on the period of oscillation, the spreading rate of the ridge, and the assumed permeability scale of the melting regime. In contrast to previous studies (Huybers & Langmuir, 2009 and Lund & Asimow, 2011), the new results indicate that effects are larger for ridges with faster spreading rates. They also show that the dominant period of variations in crustal thickness changes with spreading rate and permeability. Sea-level variations with periods in the range of 10 ky - 100 ky can result in significant changes in crustal thickness that are orders of magnitude larger than the sea-level variations that drive them. Accurately modelling this process requires the inclusion of two previously unaccounted for processes: (1) determining the volume of the melting regime that is consistent with the ridge spreading rate and (2) properly treating the transport of melt. These enable us to capture the non-linear dependencies on spreading rate and other model parameters. Spectral analysis of bathymetry at two ridge segments that have a symmetric bathymetric signal and hence are undisturbed by off-axis volcanism or ridge jumps reveals the presence of variability at frequencies associated with precession, obliquity, and the 100 ky glacial/inter-glacial variability. Furthermore, the faster spreading ridge has larger amplitude responses to changes in sea level and shows a proportionately greater response at higher frequencies. These observations reinforce the possible links among climate cycles at the surface, mantle melting at depth and the crustal fabric of the sea floor.

High mortality of Red Sea zooplankton under ambient solar radiation.

PubMed

Al-Aidaroos, Ali M; El-Sherbiny, Mohsen M O; Satheesh, Sathianeson; Mantha, Gopikrishna; Agustī, Susana; Carreja, Beatriz; Duarte, Carlos M

2014-01-01

High solar radiation along with extreme transparency leads to high penetration of solar radiation in the Red Sea, potentially harmful to biota inhabiting the upper water column, including zooplankton. Here we show, based on experimental assessments of solar radiation dose-mortality curves on eight common taxa, the mortality of zooplankton in the oligotrophic waters of the Red Sea to increase steeply with ambient levels of solar radiation in the Red Sea. Responses curves linking solar radiation doses with zooplankton mortality were evaluated by exposing organisms, enclosed in quartz bottles, allowing all the wavelengths of solar radiation to penetrate, to five different levels of ambient solar radiation (100%, 21.6%, 7.2%, 3.2% and 0% of solar radiation). The maximum mortality rates under ambient solar radiation levels averaged (±standard error of the mean, SEM) 18.4±5.8% h(-1), five-fold greater than the average mortality in the dark for the eight taxa tested. The UV-B radiation required for mortality rates to reach ½ of maximum values averaged (±SEM) 12±5.6 h(-1)% of incident UVB radiation, equivalent to the UV-B dose at 19.2±2.7 m depth in open coastal Red Sea waters. These results confirm that Red Sea zooplankton are highly vulnerable to ambient solar radiation, as a consequence of the combination of high incident radiation and high water transparency allowing deep penetration of damaging UV-B radiation. These results provide evidence of the significance of ambient solar radiation levels as a stressor of marine zooplankton communities in tropical, oligotrophic waters. Because the oligotrophic ocean extends across 70% of the ocean surface, solar radiation can be a globally-significant stressor for the ocean ecosystem, by constraining zooplankton use of the upper levels of the water column and, therefore, the efficiency of food transfer up the food web in the oligotrophic ocean.

Spring fasting behavior in a marine apex predator provides an index of ecosystem productivity

USGS Publications Warehouse

Rode, Karyn D.; Wilson, Ryan R.; Douglas, David C.; Muhlenbruch, Vanessa L; Atwood, Todd C.; Regehr, Eric V.; Richardson, Evan; Pilfold, Nicholas; Derocher, Andrew E.; Durner, George M.; Stirling, Ian; Amstrup, Steven C.; St Martin, Michelle; Pagano, Anthony M.; Simac, Kristin

2018-01-01

The effects of declining Arctic sea ice on local ecosystem productivity are not well understood but have been shown to vary inter-specifically, spatially, and temporally. Because marine mammals occupy upper trophic levels in Arctic food webs, they may be useful indicators for understanding variation in ecosystem productivity. Polar bears (Ursus maritimus) are apex predators that primarily consume benthic and pelagic-feeding ice-associated seals. As such, their productivity integrates sea ice conditions and the ecosystem supporting them. Declining sea ice availability has been linked to negative population effects for polar bears but does not fully explain observed population changes. We examined relationships between spring foraging success of polar bears and sea ice conditions, prey productivity, and general patterns of ecosystem productivity in the Beaufort and Chukchi Seas (CSs). Fasting status (≥7 days) was estimated using serum urea and creatinine levels of 1,448 samples collected from 1,177 adult and subadult bears across three subpopulations. Fasting increased in the Beaufort Sea between 1983–1999 and 2000–2016 and was related to an index of ringed seal body condition. This change was concurrent with declines in body condition of polar bears and observed changes in the diet, condition and/or reproduction of four other vertebrate consumers within the food chain. In contrast, fasting declined in CS polar bears between periods and was less common than in the two Beaufort Sea subpopulations consistent with studies demonstrating higher primary productivity and maintenance or improved body condition in polar bears, ringed seals, and bearded seals despite recent sea ice loss in this region. Consistency between regional and temporal variation in spring polar bear fasting and food web productivity suggests that polar bears may be a useful indicator species. Furthermore, our results suggest that spatial and temporal ecological variation is important in affecting upper trophic-level productivity in these marine ecosystems.

Spring fasting behavior in a marine apex predator provides an index of ecosystem productivity.

PubMed

Rode, Karyn D; Wilson, Ryan R; Douglas, David C; Muhlenbruch, Vanessa; Atwood, Todd C; Regehr, Eric V; Richardson, Evan S; Pilfold, Nicholas W; Derocher, Andrew E; Durner, George M; Stirling, Ian; Amstrup, Steven C; St Martin, Michelle; Pagano, Anthony M; Simac, Kristin

2018-01-01

The effects of declining Arctic sea ice on local ecosystem productivity are not well understood but have been shown to vary inter-specifically, spatially, and temporally. Because marine mammals occupy upper trophic levels in Arctic food webs, they may be useful indicators for understanding variation in ecosystem productivity. Polar bears (Ursus maritimus) are apex predators that primarily consume benthic and pelagic-feeding ice-associated seals. As such, their productivity integrates sea ice conditions and the ecosystem supporting them. Declining sea ice availability has been linked to negative population effects for polar bears but does not fully explain observed population changes. We examined relationships between spring foraging success of polar bears and sea ice conditions, prey productivity, and general patterns of ecosystem productivity in the Beaufort and Chukchi Seas (CSs). Fasting status (≥7 days) was estimated using serum urea and creatinine levels of 1,448 samples collected from 1,177 adult and subadult bears across three subpopulations. Fasting increased in the Beaufort Sea between 1983-1999 and 2000-2016 and was related to an index of ringed seal body condition. This change was concurrent with declines in body condition of polar bears and observed changes in the diet, condition and/or reproduction of four other vertebrate consumers within the food chain. In contrast, fasting declined in CS polar bears between periods and was less common than in the two Beaufort Sea subpopulations consistent with studies demonstrating higher primary productivity and maintenance or improved body condition in polar bears, ringed seals, and bearded seals despite recent sea ice loss in this region. Consistency between regional and temporal variation in spring polar bear fasting and food web productivity suggests that polar bears may be a useful indicator species. Furthermore, our results suggest that spatial and temporal ecological variation is important in affecting upper trophic-level productivity in these marine ecosystems. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Distribution and Origin of Multiple Bottom Simulating Reflectors in the Danube Deep-Sea Fan, Black Sea

NASA Astrophysics Data System (ADS)

Zander, T.; Berndt, C.; Haeckel, M.; Klaucke, I.; Bialas, J.; Klaeschen, D.

2015-12-01

The sedimentary succession of the anoxic, deep Black Sea Basin is an ideal location for organic matter preservation and microbial methane generation. In the depth range of the gas hydrate stability zone (GHSZ) methane gas forms methane hydrates and presumably large accumulations of gas hydrate exist in porous sediments, such as those encountered on the Danube deep-sea fan. High-resolution P-Cable 3D seismic data reveals the character and distribution of up to four stacked bottom simulating reflectors (BSR) within the channel-levee systems of the Danube deep-sea fan. These anomalous BSRs were first described by Popescu et al. (2006). The geological processes that lead to multiple BSRs are still poorly understood. The theoretical base of the GHSZ calculated from regional temperature gradients and salinity data is in agreement with the shallowest BSR in the area. We have tested two hypotheses that may explain the formation of the lower BSRs. The first hypothesis is that the lower BSRs are formed by overpressure compartments. Large amounts of free gas below the BSRs are trapped in the pore space increasing the pressure above hydrostatic condition up to a level where gas hydrates are stable again. The second hypothesis is that the lower BSRs are linked to the growth of the Danube fan. Sediment deposits from the outer levee of the youngest channel cover the area hosting multiple BSRs. The youngest channel developed during the last sea level lowstand that is correlated with the Neo-Euxinian that started 23,000 yrs. BP. We propose that the rapid sediment loading during sea level lowstands is a key factor for the preservation of paleo-BSRs in the study area. References Popescu, I., De Batist, M., Lericolais, G., Nouzé, H., Poort, J., Panin, N., Versteeg, W., Gillet, H., 2006. Multiple bottom-simulating reflections in the Black Sea: Potential proxies of past climate conditions. Marine Geology 227, 163-176.

Linking sea level rise and socioeconomic indicators under the Shared Socioeconomic Pathways

NASA Astrophysics Data System (ADS)

Nauels, Alexander; Rogelj, Joeri; Schleussner, Carl-Friedrich; Meinshausen, Malte; Mengel, Matthias

2017-11-01

In order to assess future sea level rise and its societal impacts, we need to study climate change pathways combined with different scenarios of socioeconomic development. Here, we present sea level rise (SLR) projections for the Shared Socioeconomic Pathway (SSP) storylines and different year-2100 radiative forcing targets (FTs). Future SLR is estimated with a comprehensive SLR emulator that accounts for Antarctic rapid discharge from hydrofracturing and ice cliff instability. Across all baseline scenario realizations (no dedicated climate mitigation), we find 2100 median SLR relative to 1986-2005 of 89 cm (likely range: 57-130 cm) for SSP1, 105 cm (73-150 cm) for SSP2, 105 cm (75-147 cm) for SSP3, 93 cm (63-133 cm) for SSP4, and 132 cm (95-189 cm) for SSP5. The 2100 sea level responses for combined SSP-FT scenarios are dominated by the mitigation targets and yield median estimates of 52 cm (34-75 cm) for FT 2.6 Wm-2, 62 cm (40-96 cm) for FT 3.4 Wm-2, 75 cm (47-113 cm) for FT 4.5 Wm-2, and 91 cm (61-132 cm) for FT 6.0 Wm-2. Average 2081-2100 annual SLR rates are 5 mm yr-1 and 19 mm yr-1 for FT 2.6 Wm-2 and the baseline scenarios, respectively. Our model setup allows linking scenario-specific emission and socioeconomic indicators to projected SLR. We find that 2100 median SSP SLR projections could be limited to around 50 cm if 2050 cumulative CO2 emissions since pre-industrial stay below 850 GtC, with a global coal phase-out nearly completed by that time. For SSP mitigation scenarios, a 2050 carbon price of 100 US2005 tCO2 -1 would correspond to a median 2100 SLR of around 65 cm. Our results confirm that rapid and early emission reductions are essential for limiting 2100 SLR.

An interannual link between Arctic sea-ice cover and the North Atlantic Oscillation

NASA Astrophysics Data System (ADS)

Caian, Mihaela; Koenigk, Torben; Döscher, Ralf; Devasthale, Abhay

2018-01-01

This work investigates links between Arctic surface variability and the phases of the winter (DJF) North Atlantic Oscillation (NAO) on interannual time-scales. The analysis is based on ERA-reanalysis and model data from the EC-Earth global climate model. Our study emphasizes a mode of sea-ice cover variability that leads the NAO index by 1 year. The mechanism of this leading is based on persistent surface forcing by quasi-stationary meridional thermal gradients. Associated thermal winds lead a slow adjustment of the pressure in the following winter, which in turn feeds-back on the propagation of sea-ice anomalies. The pattern of the sea-ice mode leading NAO has positive anomalies over key areas of South-Davis Strait-Labrador Sea, the Barents Sea and the Laptev-Ohkostsk seas, associated to a high pressure anomaly over the Canadian Archipelago-Baffin Bay and the Laptev-East-Siberian seas. These anomalies create a quasi-annular, quasi-steady, positive gradient of sea-ice anomalies about coastal line (when leading the positive NAO phase) and force a cyclonic vorticity anomaly over the Arctic in the following winter. During recent decades in spite of slight shifts in the modes' spectral properties, the same leading mechanism remains valid. Encouraging, actual models appear to reproduce the same mechanism leading model's NAO, relative to model areas of persistent surface forcing. This indicates that the link between sea-ice and NAO could be exploited as a potential skill-source for multi-year prediction by addressing the key problem of initializing the phase of the NAO/AO (Arctic Oscillation).

Magnetic Affinity Enzyme-Linked Immunoassay for Diagnosis of Schistosomiasis Japonicum in Persons with Low-Intensity Infection

PubMed Central

Yu, Qin; Yang, Hai; Feng, Youmei; Zhu, Yanhong; Yang, Xiangliang

2012-01-01

Most schistosome-endemic areas in China are characterized by low-intensity infections that are independent of prevalence. To establish an effective diagnostic method, we developed a magnetic affinity enzyme-linked immunoassay based on soluble egg antigens (SEA-MEIA) for diagnosing schistosomiasis in persons with low-intensity infection with Schistosoma japonicum by comparing it with a conventional enzyme-linked immunosorbent assay (ELISA). Our results showed that the SEA-MEIA had a higher sensitivity and greater precision in the diagnosis of low-intensity S. japonicum infections than the ELISA. In addition, when we used Pearson's correlation in associating SEA-MEIA with ELISA, a significant correlation existed between the two assays (r = 0.845, P < 0.001). Our data indicated that SEA-MEIA, with a higher sensitivity and greater ease of performance, would be valuable for diagnosis of schistosomiasis japonicum in persons with low-intensity infections. PMID:22869635

Measurement of fog and haze extinction characteristics and availability evaluation of free space optical link under the sea surface environment.

PubMed

Wu, Xiaojun; Wang, Hongxing; Song, Bo

2015-02-10

Fog and haze can lead to changes in extinction characteristics. Therefore, the performance of the free space optical link is highly influenced by severe weather conditions. Considering the influential behavior of weather conditions, a state-of-the-art solution for the observation of fog and haze over the sea surface is presented in this paper. A Mie scattering laser radar, with a wavelength of 532 nm, is used to observe the weather conditions of the sea surface environment. The horizontal extinction coefficients and visibilities are obtained from the observation data, and the results are presented in the paper. The changes in the characteristics of extinction coefficients and visibilities are analyzed based on both the short-term (6 days) severe weather data and long-term (6 months) data. Finally, the availability performance of the free space optical communication link is evaluated under the sea surface environment.

Remarkable link between projected uncertainties of Arctic sea-ice decline and winter Eurasian climate

NASA Astrophysics Data System (ADS)

Cheung, Hoffman H. N.; Keenlyside, Noel; Omrani, Nour-Eddine; Zhou, Wen

2018-01-01

We identify that the projected uncertainty of the pan-Arctic sea-ice concentration (SIC) is strongly coupled with the Eurasian circulation in the boreal winter (December-March; DJFM), based on a singular value decomposition (SVD) analysis of the forced response of 11 CMIP5 models. In the models showing a stronger sea-ice decline, the Polar cell becomes weaker and there is an anomalous increase in the sea level pressure (SLP) along 60°N, including the Urals-Siberia region and the Iceland low region. There is an accompanying weakening of both the midlatitude westerly winds and the Ferrell cell, where the SVD signals are also related to anomalous sea surface temperature warming in the midlatitude North Atlantic. In the Mediterranean region, the anomalous circulation response shows a decreasing SLP and increasing precipitation. The anomalous SLP responses over the Euro-Atlantic region project on to the negative North Atlantic Oscillation-like pattern. Altogether, pan-Arctic SIC decline could strongly impact the winter Eurasian climate, but we should be cautious about the causality of their linkage.

Linkages between atmospheric blocking, sea ice export through Fram Strait and the Atlantic Meridional Overturning Circulation

PubMed Central

Ionita, M.; Scholz, P.; Lohmann, G.; Dima, M.; Prange, M.

2016-01-01

As a key persistent component of the atmospheric dynamics, the North Atlantic blocking activity has been linked to extreme climatic phenomena in the European sector. It has also been linked to Atlantic multidecadal ocean variability, but its potential links to rapid oceanic changes have not been investigated. Using a global ocean-sea ice model forced with atmospheric reanalysis data, here it is shown that the 1962–1966 period of enhanced blocking activity over Greenland resulted in anomalous sea ice accumulation in the Arctic and ended with a sea ice flush from the Arctic into the North Atlantic Ocean through Fram Strait. This event induced a significant decrease of Labrador Sea water surface salinity and an abrupt weakening of the Atlantic Meridional Overturning Circulation (AMOC) during the 1970s. These results have implications for the prediction of rapid AMOC changes and indicate that an important part of the atmosphere-ocean dynamics at mid- and high latitudes requires a proper representation of the Fram Strait sea ice transport and of the synoptic scale variability such as atmospheric blocking, which is a challenge for current coupled climate models. PMID:27619955

Linkages between atmospheric blocking, sea ice export through Fram Strait and the Atlantic Meridional Overturning Circulation.

PubMed

Ionita, M; Scholz, P; Lohmann, G; Dima, M; Prange, M

2016-09-13

As a key persistent component of the atmospheric dynamics, the North Atlantic blocking activity has been linked to extreme climatic phenomena in the European sector. It has also been linked to Atlantic multidecadal ocean variability, but its potential links to rapid oceanic changes have not been investigated. Using a global ocean-sea ice model forced with atmospheric reanalysis data, here it is shown that the 1962-1966 period of enhanced blocking activity over Greenland resulted in anomalous sea ice accumulation in the Arctic and ended with a sea ice flush from the Arctic into the North Atlantic Ocean through Fram Strait. This event induced a significant decrease of Labrador Sea water surface salinity and an abrupt weakening of the Atlantic Meridional Overturning Circulation (AMOC) during the 1970s. These results have implications for the prediction of rapid AMOC changes and indicate that an important part of the atmosphere-ocean dynamics at mid- and high latitudes requires a proper representation of the Fram Strait sea ice transport and of the synoptic scale variability such as atmospheric blocking, which is a challenge for current coupled climate models.

All That Unplowed Sea

ERIC Educational Resources Information Center

MOSAIC, 1975

1975-01-01

Hunting and gathering at sea may fast be approaching their productive limits. Aquaculture - farming at sea - linked to conservation represents the sea's promise. If the system works, it might prove to be the key to supplying large amounts of food and fresh water at no cost in nonrenewable energy resources. (BT)

Arctic Sea Ice Export Through Fram Strait and Atmospheric Planetary Waves

NASA Technical Reports Server (NTRS)

Cavalieri, Donald J.; Koblinsky, Chester (Technical Monitor)

2001-01-01

A link is found between the variability of Arctic sea ice export through Ram Strait and the phase of the longest atmospheric planetary wave (zonal wave 1) in SLP for the period 1958-1997. Previous studies have identified a link between From Strait ice export and the North Atlantic Oscillation (NAO), but this link has been described as unstable because of a lack of consistency over time scales longer than the last two decades. Inconsistent and low correlations are also found between From Strait ice export and the Arctic Oscillation (AD) index. This paper shows that the phase of zonal wave 1 explains 60% - 70% of the simulated From Strait ice export variance over the Goodyear period 1958 - 1997. Unlike the NAB and AD links, these high variances are consistent for both the first and second halves of the Goodyear period. This consistency is attributed to the sensitivity of the wave I phase at high latitudes to the presence of secondary low pressure systems in the Barents Sea that serve to drive sea ice southward through From Strait. These results provide further evidence that the phase of zonal wave 1 in SLP at high latitudes drives regional as well as hemispheric low frequency Arctic Ocean and sea ice variability.

Long-term increases in young-of-the-year growth of Arctic cisco Coregonus autumnalis and environmental influences

USGS Publications Warehouse

von Biela, Vanessa R.; Zimmerman, Christian E.; Moulton, L. L.

2011-01-01

Arctic cisco Coregonus autumnalis young-of-year (YOY) growth was used as a proxy to examine the long-term response of a high-latitude fish population to changing climate from 1978 to 2004. YOY growth increased over time (r2 = 0·29) and was correlated with monthly averages of the Arctic oscillation index, air temperature, east wind speed, sea-ice concentration and river discharge with and without time lags. Overall, the most prevalent correlates to YOY growth were sea-ice concentration lagged 1 year (significant correlations in 7 months; r2 = 0·14-0·31) and Mackenzie River discharge lagged 2 years (significant correlations in 8 months; r2 = 0·13-0·50). The results suggest that decreased sea-ice concentrations and increased river discharge fuel primary production and that life cycles of prey species linking increased primary production to fish growth are responsible for the time lag. Oceanographic studies also suggest that sea ice concentration and fluvial inputs from the Mackenzie River are key factors influencing productivity in the Beaufort Sea. Future research should assess the possible mechanism relating sea ice concentration and river discharge to productivity at upper trophic levels.

Linking Monsoon Activity with River-Derived Sediment Deposition in the northern South China Sea

NASA Astrophysics Data System (ADS)

Ge, Q.; Xue, Z. G.; Liu, P.; Chu, F.

2016-02-01

Sediments retrieved from a gravity core were analyzed to examine the connection between East Asian Monsoon (EAM) and river-derived sediment deposition on the continental slope in the South China Sea since the Last Glacial Maximum. Combined clay mineralogy and grain size index analysis provided evidence of the sources of fine-grained sediment as well as for rebuilding the history of paleo-EAM. A shift of sediment source from the Pearl River to southwestern Taiwanese rivers was identified during the Holocene. The 4-8μm grain size fraction, as an environmental sensitive component and thus the EAM proxy, indicated the local deposition environment is mainly controlled by sea-level variations. And during the Holocene, the East Asian summer monsoon exhibited an in-phase relationship with East Asian winter monsoon, both following variations of the insolation intensity.

Noiseonomics: The relationship between ambient noise levels in the sea and global economic trends

PubMed Central

Frisk, George V.

2012-01-01

In recent years, the topic of noise in the sea and its effects on marine mammals has attracted considerable attention from both the scientific community and the general public. Since marine mammals rely heavily on acoustics as a primary means of communicating, navigating, and foraging in the ocean, any change in their acoustic environment may have an impact on their behavior. Specifically, a growing body of literature suggests that low-frequency, ambient noise levels in the open ocean increased approximately 3.3 dB per decade during the period 1950–2007. Here we show that this increase can be attributed primarily to commercial shipping activity, which in turn, can be linked to global economic growth. As a corollary, we conclude that ambient noise levels can be directly related to global economic conditions. We provide experimental evidence supporting this theory and discuss its implications for predicting future noise levels based on global economic trends. PMID:22666540

Assessment of Hammocks (Petenes) Resilience to Sea Level Rise Due to Climate Change in Mexico

PubMed Central

Posada Vanegas, Gregorio; de Jong, Bernardus H. J.

2016-01-01

There is a pressing need to assess resilience of coastal ecosystems against sea level rise. To develop appropriate response strategies against future climate disturbances, it is important to estimate the magnitude of disturbances that these ecosystems can absorb and to better understand their underlying processes. Hammocks (petenes) coastal ecosystems are highly vulnerable to sea level rise linked to climate change; their vulnerability is mainly due to its close relation with the sea through underground drainage in predominantly karstic soils. Hammocks are biologically important because of their high diversity and restricted distribution. This study proposes a strategy to assess resilience of this coastal ecosystem when high-precision data are scarce. Approaches and methods used to derive ecological resilience maps of hammocks are described and assessed. Resilience models were built by incorporating and weighting appropriate indicators of persistence to assess hammocks resilience against flooding due to climate change at “Los Petenes Biosphere Reserve”, in the Yucatán Peninsula, Mexico. According to the analysis, 25% of the study area is highly resilient (hot spots), whereas 51% has low resilience (cold spots). The most significant hot spot clusters of resilience were located in areas distant to the coastal zone, with indirect tidal influence, and consisted mostly of hammocks surrounded by basin mangrove and floodplain forest. This study revealed that multi-criteria analysis and the use of GIS for qualitative, semi-quantitative and statistical spatial analyses constitute a powerful tool to develop ecological resilience maps of coastal ecosystems that are highly vulnerable to sea level rise, even when high-precision data are not available. This method can be applied in other sites to help develop resilience analyses and decision-making processes for management and conservation of coastal areas worldwide. PMID:27611802

Shelfal sediment transport by undercurrents forces turbidity current activity during high sea level, Chile continental margin

NASA Astrophysics Data System (ADS)

Bernhardt, Anne; Hebbeln, Dierk; Regenberg, Marcus; Lückge, Andreas; Strecker, Manfred. R.

2016-04-01

Understanding the links between terrigenous sediment supply and marine transport and depositional processes along tectonically active margins is essential to decipher turbidite successions as potential archives of climatic and seismic forcings and to comprehend timing and quantity of marine clastic deposition. Sequence stratigraphic models predict coarse-grained terrigenous sediment delivery to deep-marine sites mainly during sea-level fall and lowstand. Marine clastic deposition during periods of transgression and highstand has been attributed to the continued geomorphic connectivity between terrestrial sediment sources and marine sinks (e.g., rivers connected to submarine canyons) often facilitated by narrow shelves, high sediment supply causing delta migration to the shelf edge, and/or abrupt increases in sediment supply due to climatic variability or catastrophic events. To decipher the controls on Holocene highstand turbidite deposition, we analyzed twelve sediment cores of spatially disparate, coeval Holocene turbidite systems along the Chile margin (29-40°S) with changing climatic and geomorphic characteristics but uniform changes of sea level. Intraslope basins in north-central Chile (29-33°S) offshore a narrow to absent shelf record a shut-off of turbidite activity during the Holocene. In contrast, core sites in south-central Chile (36-40°S) offshore a wide continental shelf have repeatedly experienced turbidite deposition during sea-level highstand conditions, even though most of the depocenters are not connected via canyons to sediment sources. The interplay of stable high sediment supply related to strong onshore precipitation in combination with a wide shelf, over which undercurrents move sediment towards the shelf edge, appears to control Holocene turbidite sedimentation and sediment export to the deep sea.

Disentangling sea-surface temperature and anthropogenic aerosol influences on recent trends in South Asian monsoon rainfall

NASA Astrophysics Data System (ADS)

Patil, Nitin; Venkataraman, Chandra; Muduchuru, Kaushik; Ghosh, Subimal; Mondal, Arpita

2018-05-01

Recent studies point to combined effects of changes in regional land-use, anthropogenic aerosol forcing and sea surface temperature (SST) gradient on declining trends in the South Asian monsoon (SAM). This study attempted disentangling the effects produced by changes in SST gradient from those by aerosol levels in an atmospheric general circulation model. Two pairs of transient ensemble simulations were made, for a 40-year period from 1971 to 2010, with evolving versus climatological SSTs and with anthropogenic aerosol emissions fixed at 1971 versus 2010, in each case with evolution of the other forcing element, as well as GHGs. Evolving SST was linked to a widespread feedback on increased surface temperature, reduced land-sea thermal contrast and a weakened Hadley circulation, with weakening of cross-equatorial transport of moisture transport towards South Asia. Increases in anthropogenic aerosol levels (1971 versus 2010), led to an intensification of drying in the peninsular Indian region, through several regional pathways. Aerosol forcing induced north-south asymmetries in temperature and sea-level pressure response, and a cyclonic circulation in the Bay of Bengal, leading to an easterly flow, which opposes the monsoon flow, suppressing moisture transport over peninsular India. Further, aerosol induced decreases in convection, vertically integrated moisture flux convergence, evaporation flux and cloud fraction, in the peninsular region, were spatially congruent with reduced convective and stratiform rainfall. Overall, evolution of SST acted through a weakening of cross-equatorial moisture flow, while increases in aerosol levels acted through suppression of Arabian Sea moisture transport, as well as, of convection and vertical moisture transport, to influence the suppression of SAM rainfall.

Assessment of Hammocks (Petenes) Resilience to Sea Level Rise Due to Climate Change in Mexico.

PubMed

Hernández-Montilla, Mariana C; Martínez-Morales, Miguel Angel; Posada Vanegas, Gregorio; de Jong, Bernardus H J

2016-01-01

There is a pressing need to assess resilience of coastal ecosystems against sea level rise. To develop appropriate response strategies against future climate disturbances, it is important to estimate the magnitude of disturbances that these ecosystems can absorb and to better understand their underlying processes. Hammocks (petenes) coastal ecosystems are highly vulnerable to sea level rise linked to climate change; their vulnerability is mainly due to its close relation with the sea through underground drainage in predominantly karstic soils. Hammocks are biologically important because of their high diversity and restricted distribution. This study proposes a strategy to assess resilience of this coastal ecosystem when high-precision data are scarce. Approaches and methods used to derive ecological resilience maps of hammocks are described and assessed. Resilience models were built by incorporating and weighting appropriate indicators of persistence to assess hammocks resilience against flooding due to climate change at "Los Petenes Biosphere Reserve", in the Yucatán Peninsula, Mexico. According to the analysis, 25% of the study area is highly resilient (hot spots), whereas 51% has low resilience (cold spots). The most significant hot spot clusters of resilience were located in areas distant to the coastal zone, with indirect tidal influence, and consisted mostly of hammocks surrounded by basin mangrove and floodplain forest. This study revealed that multi-criteria analysis and the use of GIS for qualitative, semi-quantitative and statistical spatial analyses constitute a powerful tool to develop ecological resilience maps of coastal ecosystems that are highly vulnerable to sea level rise, even when high-precision data are not available. This method can be applied in other sites to help develop resilience analyses and decision-making processes for management and conservation of coastal areas worldwide.

Spatial and temporal operation of the Scotia Sea ecosystem: a review of large-scale links in a krill centred food web

PubMed Central

Murphy, E.J; Watkins, J.L; Trathan, P.N; Reid, K; Meredith, M.P; Thorpe, S.E; Johnston, N.M; Clarke, A; Tarling, G.A; Collins, M.A; Forcada, J; Shreeve, R.S; Atkinson, A; Korb, R; Whitehouse, M.J; Ward, P; Rodhouse, P.G; Enderlein, P; Hirst, A.G; Martin, A.R; Hill, S.L; Staniland, I.J; Pond, D.W; Briggs, D.R; Cunningham, N.J; Fleming, A.H

2006-01-01

The Scotia Sea ecosystem is a major component of the circumpolar Southern Ocean system, where productivity and predator demand for prey are high. The eastward-flowing Antarctic Circumpolar Current (ACC) and waters from the Weddell–Scotia Confluence dominate the physics of the Scotia Sea, leading to a strong advective flow, intense eddy activity and mixing. There is also strong seasonality, manifest by the changing irradiance and sea ice cover, which leads to shorter summers in the south. Summer phytoplankton blooms, which at times can cover an area of more than 0.5 million km2, probably result from the mixing of micronutrients into surface waters through the flow of the ACC over the Scotia Arc. This production is consumed by a range of species including Antarctic krill, which are the major prey item of large seabird and marine mammal populations. The flow of the ACC is steered north by the Scotia Arc, pushing polar water to lower latitudes, carrying with it krill during spring and summer, which subsidize food webs around South Georgia and the northern Scotia Arc. There is also marked interannual variability in winter sea ice distribution and sea surface temperatures that is linked to southern hemisphere-scale climate processes such as the El Niño–Southern Oscillation. This variation affects regional primary and secondary production and influences biogeochemical cycles. It also affects krill population dynamics and dispersal, which in turn impacts higher trophic level predator foraging, breeding performance and population dynamics. The ecosystem has also been highly perturbed as a result of harvesting over the last two centuries and significant ecological changes have also occurred in response to rapid regional warming during the second half of the twentieth century. This combination of historical perturbation and rapid regional change highlights that the Scotia Sea ecosystem is likely to show significant change over the next two to three decades, which may result in major ecological shifts. PMID:17405210

Physical and biochemical properties of the euphausiids Thysanoessa inermis, Thysanoessa raschii, and Thysanoessa longipes in the eastern Bering Sea

NASA Astrophysics Data System (ADS)

Harvey, H. Rodger; Pleuthner, Rachel L.; Lessard, Evelyn J.; Bernhardt, Megan J.; Tracy Shaw, C.

2012-06-01

Euphausiids are an integral part of the Bering Sea ecosystem, linking primary production to upper level trophic levels as both consumers and prey. Species native to this region extend over a range of geographic provinces and serve as a critical component of the movement of energy through the food web. As one facet of the BEST-BSIERP Bering Sea program, we determined the proximate composition and essential allometric relationships of multiple species of euphausiids collected over three years in the eastern Bering Sea. Three euphausiid species were examined: Thysanoessa inermis, Thysanoessa raschii, and Thysanoessa longipes. While the three species were similar with respect to size, T. inermis had the highest average wet and dry weights per size class, as well as highest carbon and caloric concentrations. Among the three species, T. inermis and T. longipes had similar lipid concentrations, with T. longipes showing higher average lipid concentrations. Empirical equations were developed to describe fundamental relationships between length, weight, PC/PN, and calorie and lipid content for the three species over the full range of sizes encountered in the study area. Such relationships increase our understanding of how euphausiids contribute to the carbon budget and energy input in the eastern Bering Sea system and help to define realistic parameters for ongoing and future modeling efforts.

50 CFR 648.126 - Protection of threatened and endangered sea turtles.

Code of Federal Regulations, 2011 CFR

2011-10-01

... sea turtles. 648.126 Section 648.126 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT... sea turtles. Link to an amendment published at 76 FR 60635, Sept. 29, 2011. This section supplements existing regulations issued to regulate incidental take of sea turtles under authority of the Endangered...

Allergen analysis of sea urchin roe using sera from five patients.

PubMed

Tanaka, Kenichi; Kondo, Yasuto; Inuo, Chisato; Nakajima, Yoichi; Tsuge, Ikuya; Doi, Satoru; Yanagihara, Shigeto; Yoshikawa, Tetsushi; Urisu, Atsuo

2014-01-01

Sea urchin roe can cause anaphylactic reactions the first time they are consumed; therefore, careful clinical attention should be paid to their effects. However, no previous study has examined the allergens in sea urchin roe using sera from more than one patient. We attempted to identify sea urchin allergens using sera from 5 patients with sea urchin allergies. We enrolled 5 patients with relevant medical histories, positive results on a skin prick test and/or a food challenge test, and high levels of sea urchin-specific IgE in an enzyme-linked immunosorbent assay. We performed SDS-PAGE, immunoblotting, immunoblot inhibition, and N-terminal amino acid sequence detection. Ten protein bands ranging from 18 to 170 kDa were detected in more than 2 patients' sera. In immunoblotting, the protein band for the 170-kDa major yolk protein was recognized by 4 of the 5 sera. Furthermore, the reaction between IgE and the protein band for egg cortical vesicle protein (18 kDa) was inhibited by the addition of salmon roe extract. Major yolk protein was confirmed to be one of the main allergens in sea urchin roe. In addition, egg cortical vesicle protein (18 kDa) was demonstrated to be an important protein for cross-reactivity with salmon roe. © 2014 S. Karger AG, Basel.

A biogeographic network reveals evolutionary links between deep-sea hydrothermal vent and methane seep faunas

PubMed Central

2016-01-01

Deep-sea hydrothermal vents and methane seeps are inhabited by members of the same higher taxa but share few species, thus scientists have long sought habitats or regions of intermediate character that would facilitate connectivity among these habitats. Here, a network analysis of 79 vent, seep, and whale-fall communities with 121 genus-level taxa identified sedimented vents as a main intermediate link between the two types of ecosystems. Sedimented vents share hot, metal-rich fluids with mid-ocean ridge-type vents and soft sediment with seeps. Such sites are common along the active continental margins of the Pacific Ocean, facilitating connectivity among vent/seep faunas in this region. By contrast, sedimented vents are rare in the Atlantic Ocean, offering an explanation for the greater distinction between its vent and seep faunas compared with those of the Pacific Ocean. The distribution of subduction zones and associated back-arc basins, where sedimented vents are common, likely plays a major role in the evolutionary and biogeographic connectivity of vent and seep faunas. The hypothesis that decaying whale carcasses are dispersal stepping stones linking these environments is not supported. PMID:27974524

Trophic structure of coastal Antarctic food webs associated with changes in sea ice and food supply.

PubMed

Norkko, A; Thrush, S F; Cummings, V J; Gibbs, M M; Andrew, N L; Norkko, J; Schwarz, A M

2007-11-01

Predicting the dynamics of ecosystems requires an understanding of how trophic interactions respond to environmental change. In Antarctic marine ecosystems, food web dynamics are inextricably linked to sea ice conditions that affect the nature and magnitude of primary food sources available to higher trophic levels. Recent attention on the changing sea ice conditions in polar seas highlights the need to better understand how marine food webs respond to changes in such broad-scale environmental drivers. This study investigated the importance of sea ice and advected primary food sources to the structure of benthic food webs in coastal Antarctica. We compared the isotopic composition of several seafloor taxa (including primary producers and invertebrates with a variety of feeding modes) that are widely distributed in the Antarctic. We assessed shifts in the trophic role of numerically dominant benthic omnivores at five coastal Ross Sea locations. These locations vary in primary productivity and food availability, due to their different levels of sea ice cover, and proximity to polynyas and advected primary production. The delta15N signatures and isotope mixing model results for the bivalves Laternula elliptica and Adamussium colbecki and the urchin Sterechinus neumeyeri indicate a shift from consumption of a higher proportion of detritus at locations with more permanent sea ice in the south to more freshly produced algal material associated with proximity to ice-free water in the north and east. The detrital pathways utilized by many benthic species may act to dampen the impacts of large seasonal fluctuations in the availability of primary production. The limiting relationship between sea ice distribution and in situ primary productivity emphasizes the role of connectivity and spatial subsidies of organic matter in fueling the food web. Our results begin to provide a basis for predicting how benthic ecosystems will respond to changes in sea ice persistence and extent along environmental gradients in the high Antarctic.

Reconstructing Late Holocene Relative Sea-level Changes on the Gulf Coast of Florida

NASA Astrophysics Data System (ADS)

Gerlach, M. J.; Engelhart, S. E.; Kemp, A.; Moyer, R. P.; Smoak, J. M.; Bernhardt, C. E.

2015-12-01

Little is known about late Holocene relative sea-level (RSL) along the Gulf Coast of Florida. A RSL reconstruction from this region is needed to fill a spatial gap in sea-level records which can be used to support coastal management, contribute geologic data for Earth-Ice models estimating late Holocene land-level change and serve as the basis for which future projections of sea-level rise must be superimposed. Further, this dataset is crucial to understanding the presence/absence and non-synchronous timing of small sea-level oscillations (e.g. rise at ~ 1000 A.D.; fall at ~ 1400 A.D.) during the past 2000 years on the Atlantic and Gulf Coasts of the United States that may be linked to climate anomalies. We present the results of a high-resolution RSL reconstruction based on the sediment record of two salt marshes on the eastern margin of the Gulf of Mexico. Two ~1.3m cores primarily composed of Juncus roemeranius peat reveal RSL changes over the past ~2000 years in the southern end of Tampa Bay and in Charlotte Harbor, Florida. Two study sites were used to isolate localized factors affecting RSL at either location. Lithostratigraphic analysis at both sites identifies a transition from sandy-silt layers into salt-marsh peat at the bottom of each core. The two records show continuous accumulation of salt-marsh peat with Juncus roemeranius macrofossils and intermittent sand horizons likely reflecting inundation events. We used vertically zoned assemblages of modern foraminifera to assign the indicative meaning. The high marsh is dominated by Ammoastuta inepta, Haplophragmoides wilberti, and Arenoparella mexicana, with low marsh and tidal flats identified by Ammobaculites spp. and Miliammina fusca. Chronologies for these study sites were established using AMS radiocarbon dating of in-situ plant macrofossils, Cs137, Pb210 and pollen and pollution chronohorizons. Our regional RSL curve will add additional data for constraining the mechanisms causing RSL change.

Parasites in the Wadden Sea food web

NASA Astrophysics Data System (ADS)

Thieltges, David W.; Engelsma, Marc Y.; Wendling, Carolin C.; Wegner, K. Mathias

2013-09-01

While the free-living fauna of the Wadden Sea has received much interest, little is known on the distribution and effects of parasites in the Wadden Sea food web. However, recent studies on this special type of trophic interaction indicate a high diversity of parasites in the Wadden Sea and suggest a multitude of effects on the hosts. This also includes effects on specific predator-prey relationships and the general structure of the food web. Focussing on molluscs, a major group in the Wadden Sea in terms of biomass and abundance and an important link between primary producers and predators, we review existing studies and exemplify the ecological role of parasites in the Wadden Sea food web. First, we give a brief inventory of parasites occurring in the Wadden Sea, ranging from microparasites (e.g. protozoa, bacteria) to macroparasites (e.g. helminths, parasitic copepods) and discuss the effects of spatial scale on heterogeneities in infection levels. We then demonstrate how parasites can affect host population dynamics by acting as a strong mortality factor, causing mollusc mass mortalities. In addition, we will exemplify how parasites can mediate the interaction strength of predator-prey relationships and affect the topological structure of the Wadden Sea food web as a whole. Finally, we highlight some ongoing changes regarding parasitism in the Wadden Sea in the course of global change (e.g. species introduction, climate change) and identify important future research questions to entangle the role of parasites in the Wadden Sea food web.

Impact of relative sea level and rapid climate changes on the architecture and lithofacies of the Holocene Rhone subaqueous delta (Western Mediterranean Sea)

NASA Astrophysics Data System (ADS)

Fanget, Anne-Sophie; Berné, Serge; Jouet, Gwénaël; Bassetti, Maria-Angela; Dennielou, Bernard; Maillet, Grégoire M.; Tondut, Mathieu

2014-05-01

The modern Rhone delta in the Gulf of Lions (NW Mediterranean) is a typical wave-dominated delta that developed after the stabilization of relative sea level following the last deglacial sea-level rise. Similar to most other deltas worldwide, it displays several stacked parasequences and lobes that reflect the complex interaction between accommodation, sediment supply and autogenic processes on the architecture of a wave-dominated delta. The interpretation of a large set of newly acquired very high-resolution seismic and sedimentological data, well constrained by 14C dates, provides a refined three-dimensional image of the detailed architecture (seismic bounding surfaces, sedimentary facies) of the Rhone subaqueous delta, and allows us to propose a scenario for delta evolution during the last deglaciation and Holocene. The subaqueous delta consists of “parasequence-like” depositional wedges, a few metres to 20-30 m in thickness. These wedges first back-stepped inland toward the NW in response to combined global sea-level rise and overall westward oceanic circulation, at a time when sediment supply could not keep pace with rapid absolute (eustatic) sea-level rise. At the Younger Dryas-Preboreal transition, more rapid sea-level rise led to the formation of a major flooding surface (equivalent to a wave ravinement surface). After stabilization of global sea level in the mid-Holocene, accommodation became the leading factor in controlling delta architecture. An eastward shift of depocentres occurred, probably favoured by higher subsidence rate within the thick Messinian Rhone valley fill. The transition between transgressive (backstepping geometry) and regressive (prograding geometry) (para)sequences resulted in creation of a Maximum Flooding Surface (MFS) that differs from a “classical” MFS described in the literature. It consists of a coarse-grained interval incorporating reworked shoreface material within a silty clay matrix. This distinct lithofacies results from condensation/erosion, which appears as an important process even within supply-dominated deltaic systems, due to avulsion of distributaries. The age of the MFS varies along-strike between ca. 7.8 and 5.6 kyr cal. BP in relation to the position of depocentres and climatically-controlled sediment supply. The last rapid climate change of the Holocene, the Little Ice Age (1250-1850 AD), had a distinct stratigraphic influence on the architecture and lithofacies of the Rhone subaqueous delta through the progradation of two deltaic lobes. In response to changes in sediment supply linked to rapid climate changes (and to anthropic factors), the Rhone delta evolved from wave-dominated to fluvial dominated, and then wave dominated again.

Connecting marine productivity to sea-spray via microscale biological processes: phytoplancton demise and viral infection

NASA Astrophysics Data System (ADS)

Facchini, C.; O'Dowd, C. D. D.; Danovaro, R.

2015-12-01

The processes that link phytoplankton biomass and productivity to the organic matter enrichment in sea spray aerosol are far from being elucidated and modelling predictions remain highly uncertain at the moment. While some studies have asserted that the enrichment of OM in sea spray aerosol is independent on marine productivity, others, have shown significant correlation with phytoplankton biomass and productivity (Chl-a retrieved by satellites). We present here new results illustrating a clear link between OM mass-fraction enrichment in sea spray (OMss) and both phytoplankton-biomass and Net Primary Productivity (NPP). We suggest that the OM enrichment of sea spray through the demise of the bloom, driven by nanoscale biological processes (such as viral infections), which determine the release of celldebris, exudates and other colloidal material. This OM, through processes, leads to enrichment in sea-spray, thus demonstrating an important coupling between biologically-drive plankton bloom termination, marine productivity and sea-spraymodification with potentially significant climate impacts.

Holocene aggradation of the Dry Tortugas coral reef ecosystem

USGS Publications Warehouse

Brock, J.C.; Palaseanu-Lovejoy, M.; Poore, R.Z.; Nayegandhi, A.; Wright, C.W.

2010-01-01

Radiometric age dating of reef cores acquired at the Dry Tortugas coral reef ecosystem (DTCRE) was merged with lidar topographic mapping to examine Holocene reef development linked to spatial variation in growth and erosion under the control of sea level. Analysis of variance of lidar topography confirmed the presence of three distinct terraces on all three major DTCRE banks (Loggerhead Bank, Garden Bank, and Pulaski Bank). Reef building on the middle terrace (T2) began atop Pleistocene edifices on Loggerhead Bank by 8.0 ka (thousands of years ago) and on Garden Bank by 7.2 ka at elevations of about −16.0 m and −11.9 m, respectively, relative to present mean sea level. Following this initiation at different elevations, T2 aggraded vertically on both banks at different rates during the early Holocene under foundering conditions until a highstand at 5.2 ka, resulting in a 2.21 m offset in present mean T2 elevation between these banks. Initiation of an upper terrace (T1) occurred on both Loggerhead Bank and Garden Bank in association with sea-level fall to a lowstand at near 4.8 ka. This upper terrace initiated on Garden Bank at about 5.0 ka and then grew upward at rate of 2.5 mm year−1 until approximately 3.8 ka. On Loggerhead Bank, the upper T1 terrace formed after 4.5 ka at a higher vertical aggradation rate of 4.1 mm year−1, but at a lower elevation than on Garden Bank. Terrace T1 aggraded on Loggerhead Bank below the elevation of lowstands during late Holocene sea-level oscillation, and consequently erosion on Loggerhead Bank was minimal and likely limited to the crest of the upper terrace. In contrast, after 3.8 ka terrace T1 on Garden Bank likely tracked sea level and consequently underwent erosion when sea level fell to second, third and fourth lowstands at 3.3, 1.1, and 0.3 ka.

Temporal Dynamics of Top Predators Interactions in the Barents Sea

PubMed Central

Durant, Joël M.; Skern-Mauritzen, Mette; Krasnov, Yuri V.; Nikolaeva, Natalia G.; Lindstrøm, Ulf; Dolgov, Andrey

2014-01-01

The Barents Sea system is often depicted as a simple food web in terms of number of dominant feeding links. The most conspicuous feeding link is between the Northeast Arctic cod Gadus morhua, the world's largest cod stock which is presently at a historical high level, and capelin Mallotus villosus. The system also holds diverse seabird and marine mammal communities. Previous diet studies may suggest that these top predators (cod, bird and sea mammals) compete for food particularly with respect to pelagic fish such as capelin and juvenile herring (Clupea harengus), and krill. In this paper we explored the diet of some Barents Sea top predators (cod, Black-legged kittiwake Rissa tridactyla, Common guillemot Uria aalge, and Minke whale Balaenoptera acutorostrata). We developed a GAM modelling approach to analyse the temporal variation diet composition within and between predators, to explore intra- and inter-specific interactions. The GAM models demonstrated that the seabird diet is temperature dependent while the diet of Minke whale and cod is prey dependent; Minke whale and cod diets depend on the abundance of herring and capelin, respectively. There was significant diet overlap between cod and Minke whale, and between kittiwake and guillemot. In general, the diet overlap between predators increased with changes in herring and krill abundances. The diet overlap models developed in this study may help to identify inter-specific interactions and their dynamics that potentially affect the stocks targeted by fisheries. PMID:25365430

50 CFR 635.29 - Transfer at sea.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 8 2010-10-01 2010-10-01 false Transfer at sea. 635.29 Section 635.29..., DEPARTMENT OF COMMERCE ATLANTIC HIGHLY MIGRATORY SPECIES Management Measures § 635.29 Transfer at sea. Link... tuna, blue marlin, white marlin, or swordfish at sea in the Atlantic Ocean, regardless of where the...

50 CFR 648.106 - Sea Turtle conservation.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 10 2011-10-01 2011-10-01 false Sea Turtle conservation. 648.106 Section... Summer Flounder Fisheries § 648.106 Sea Turtle conservation. Link to an amendment published at 76 FR 60629, Sept. 29, 2011. Sea turtle regulations are found at 50 CFR parts 222 and 223. [64 FR 57595, Oct...

50 CFR 648.13 - Transfers at sea.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 10 2011-10-01 2011-10-01 false Transfers at sea. 648.13 Section 648.13... sea. Link to an amendment published at 76 FR 60615, Sept. 29, 2011. (a) Only vessels issued a Loligo... receiving vessel possesses a written receipt for any small-mesh multispecies purchased at sea. (c) All...

Terrestrial biomarkers in the sediment of the East Sea (Japan Sea) since the MIS 11: implications for paleoproductivity and paleoclimatic changes

NASA Astrophysics Data System (ADS)

Hyun, S.; Suh, Y. J.; Woo, K. S.; Ikehara, M.

2014-12-01

Terrestrial biomarkers such as n-alkanes and cholesterol were analyzed to infer the variations of paleoproductivity and the corresponding paleoclimatologic information from the sediment of the Korean Plateau, East Sea (Japan Sea) since the Marine Isotope Stage (MIS) 11 (ca. 400 ka). Previous studies of SST variation have shown that glacial-interglacial scale changes were quite variable with the maximum range of 26oC in MIS 7, and the minimum range of 12oC during MIS 2 and 6. The distribution of terrestrial n-alkanes signatures is characterized by the occurrence of high odd number frequency with a minor contribution of specific compound (nC27 only). Average Chain Length (ACL) and Carbon Preferences Index (CPI), both of which are derived from n-alkane combination, show similar shifting between glacial and interglacial periods. This suggests that paleovegetation communities had been changed in responding to paleoclimatological variations, and the input amount of terrestrial compound was strongly linked with paleoclimatologic changes. In particular, depleted values of δ13Corg during MIS 2, 8 and 10 were coincident with lower nitrogen isotope values indicating local paleoceanographic effects such as paleoproductivity changes. Decoupling between δ13Corg and δ15Norg during MIS 1, 3, 5, 7 and coupling of the two during MIS 8 and 11 can be observed, which appear to be interpreted as local productivity changes. In particular, high abundance of cholesterol and C21 n-alkanes, which were derived from diatom, increased during interglacial periods. Therefore, alkenones, SST and n-alkanes signatures coincide with δ13Corg and δ15Norg variations during glacial-interglacial cycles and further strongly associated with cholesterol abundance suggesting that the paleoenvironmental conditions in East Sea during glacial-interglacial periods were sensitive not only to global climate changes but also to local paleceanographic variations. Surface water circulation around the Korea Plateau associated with eustatic sea-level changes may have been linked with paleoproductivity changes, at least on the Korea Plateau of the East Sea (Japan Sea) since the last MIS 11.

Food-web traits of the North Aegean Sea ecosystem (Eastern Mediterranean) and comparison with other Mediterranean ecosystems

NASA Astrophysics Data System (ADS)

Tsagarakis, K.; Coll, M.; Giannoulaki, M.; Somarakis, S.; Papaconstantinou, C.; Machias, A.

2010-06-01

A mass-balance trophic model was built to describe the food-web traits of the North Aegean Sea (Strymonikos Gulf and Thracian Sea, Greece, Eastern Mediterranean) during the mid-2000s and to explore the impacts of fishing. This is the first food-web model representing the Aegean Sea, and results were presented and discussed in comparison to other previous ecosystems modelled from the western and the central areas of the basin (South Catalan and North-Central Adriatic Seas). Forty functional groups were defined, covering the entire trophic spectrum from lower to higher trophic levels. Emphasis was placed on commercial invertebrates and fish. The potential ecological role of the invasive ctenophore, Mnemiopsis leidyi, and several vulnerable groups (e.g., dolphins) was also explored. Results confirmed the spatial productivity patterns known for the Mediterranean Sea showing, for example, that the total biomass is highest in N.C. Adriatic and lowest in N. Aegean Sea. Accordingly, food-web flows and several ecosystem indicators like the mean transfer efficiency were influenced by these patterns. Nevertheless, all three systems shared some common features evidencing similarities of Mediterranean Sea ecosystems such as dominance of the pelagic fraction in terms of flows and strong benthic-pelagic coupling of zooplankton and benthic invertebrates through detritus. The importance of detritus highlighted the role of the microbial food-web, which was indirectly considered through detritus dynamics. Ciliates, mesozooplankton and several benthic invertebrate groups were shown as important elements of the ecosystem linking primary producers and detritus with higher trophic levels in the N. Aegean Sea. Adult anchovy was shown as the most important fish group in terms of production, consumption and overall effect on the rest of the ecological groups in the model, in line with results from the Western Mediterranean Sea. The five fishing fleets considered (both artisanal and industrial) had high impacts on vulnerable species and numerous targeted groups given the multispecies nature of the fisheries in the N. Aegean Sea. Several exploitation indices highlighted that the N. Aegean Sea ecosystem was highly exploited and unlikely to be sustainably fished, similarly to other Mediterranean marine ecosystems.

Mortality of sea lions along the central California coast linked to a toxic diatom bloom.

PubMed

Scholin, C A; Gulland, F; Doucette, G J; Benson, S; Busman, M; Chavez, F P; Cordaro, J; DeLong, R; De Vogelaere, A; Harvey, J; Haulena, M; Lefebvre, K; Lipscomb, T; Loscutoff, S; Lowenstine, L J; Marin, R; Miller, P E; McLellan, W A; Moeller, P D; Powell, C L; Rowles, T; Silvagni, P; Silver, M; Spraker, T; Trainer, V; Van Dolah, F M

2000-01-06

Over 400 California sea lions (Zalophus californianus) died and many others displayed signs of neurological dysfunction along the central California coast during May and June 1998. A bloom of Pseudo-nitzschia australis (diatom) was observed in the Monterey Bay region during the same period. This bloom was associated with production of domoic acid (DA), a neurotoxin that was also detected in planktivorous fish, including the northern anchovy (Engraulis mordax), and in sea lion body fluids. These and other concurrent observations demonstrate the trophic transfer of DA resulting in marine mammal mortality. In contrast to fish, blue mussels (Mytilus edulus) collected during the DA outbreak contained no DA or only trace amounts. Such findings reveal that monitoring of mussel toxicity alone does not necessarily provide adequate warning of DA entering the food web at levels sufficient to harm marine wildlife and perhaps humans.

The Dynamics and Characteristics of Aeolian Dust in Dryland Central Asia: Possible Impacts on Respiratory Health in the Aral Sea Basin

NASA Astrophysics Data System (ADS)

Wiggs, G. F.; O'Hara, S.; Wegerdt, J.; van der Meer, J.; Small, I.; Hubbard, R.

2003-12-01

Over the last 40 years over 36,000 km2 of the former Aral Sea bed have been exposed creating a potentially significant aeolian dust source. It is widely believed, but little researched, that increased dust storm activity in the region has had a major impact on human health. In this paper we report the findings of a study into the link between dust exposure and respiratory health amongst children in the Autonomous Republic of Karakalpakstan, located on the southern shore of the Aral Sea. Data were collected over a 12 month period at 16 sites located within a broad transect running north to south through Karakalpakstan. At each site monthly measurements of dust deposition were undertaken linked with daily meteorological data at 6 stations. At 3 sites weekly measurements of PM10 were also carried out. Approximately 100 children (aged 7-10 years) were randomly selected within 5 km of each dust trap site and data were collected on their respiratory health and environmental exposures. Lung function data were also collected using a handheld spirometer. A linear regression model was used to predict lung function for the children incorporating variables for Forced Expiratory Volume in one second (FEV1), age, gender, height and weight and we estimated the impact of dust deposition rates on the odds of having abnormal lung function using logistic regression. The findings indicate that dust deposition rates across the region are high with sites located near the former shore of the sea being the worst affected. For these northerly regions the former Aral Sea bed is the most likely source of dust. The situation for the rest of the country seems to be far more complex. In these regions it appears that local sources (agricultural fields, abandoned irrigation grounds, overgrazed dunes, and unpaved roads) and more distant sources to the south and south-west represent significant sediment providers, particularly in the early summer when agricultural fields are ploughed. We found some evidence of a dose-related impact of dust levels on lung function. These associations were statistically significant for all measures of dust exposure but were most marked for levels of winter dust exposure and level of PM2.5 exposure. The results from this study suggest that aeolian dust dynamics in the region are spatially and temporally highly variable and, counter to local and regional perceptions, the former bed of the Aral Sea does not appear to be the only significant source. Nevertheless, there is also evidence of a dose-related impact of airborne dust on the risk of having abnormally low lung function in children living in the Aral Sea Area.

Probabilistic 21st and 22nd Century Sea-Level Projections at a Global Network of Tide-Gauge Sites

NASA Technical Reports Server (NTRS)

Kopp, Robert E.; Horton, Radley M.; Little, Christopher M.; Mitrovica, Jerry X.; Oppenheimer, Michael; Rasmussen, D. J.; Strauss, Benjamin H.; Tebaldi, Claudia

2014-01-01

Sea-level rise due to both climate change and non-climatic factors threatens coastal settlements, infrastructure, and ecosystems. Projections of mean global sea-level (GSL) rise provide insufficient information to plan adaptive responses; local decisions require local projections that accommodate different risk tolerances and time frames and that can be linked to storm surge projections. Here we present a global set of local sea-level (LSL) projections to inform decisions on timescales ranging from the coming decades through the 22nd century. We provide complete probability distributions, informed by a combination of expert community assessment, expert elicitation, and process modeling. Between the years 2000 and 2100, we project a very likely (90% probability) GSL rise of 0.5–1.2?m under representative concentration pathway (RCP) 8.5, 0.4–0.9?m under RCP 4.5, and 0.3–0.8?m under RCP 2.6. Site-to-site differences in LSL projections are due to varying non-climatic background uplift or subsidence, oceanographic effects, and spatially variable responses of the geoid and the lithosphere to shrinking land ice. The Antarctic ice sheet (AIS) constitutes a growing share of variance in GSL and LSL projections. In the global average and at many locations, it is the dominant source of variance in late 21st century projections, though at some sites oceanographic processes contribute the largest share throughout the century. LSL rise dramatically reshapes flood risk, greatly increasing the expected number of “1-in-10” and “1-in-100” year events.

Probabilistic 21st and 22nd century sea-level projections at a global network of tide-gauge sites

NASA Astrophysics Data System (ADS)

Kopp, Robert E.; Horton, Radley M.; Little, Christopher M.; Mitrovica, Jerry X.; Oppenheimer, Michael; Rasmussen, D. J.; Strauss, Benjamin H.; Tebaldi, Claudia

2014-08-01

Sea-level rise due to both climate change and non-climatic factors threatens coastal settlements, infrastructure, and ecosystems. Projections of mean global sea-level (GSL) rise provide insufficient information to plan adaptive responses; local decisions require local projections that accommodate different risk tolerances and time frames and that can be linked to storm surge projections. Here we present a global set of local sea-level (LSL) projections to inform decisions on timescales ranging from the coming decades through the 22nd century. We provide complete probability distributions, informed by a combination of expert community assessment, expert elicitation, and process modeling. Between the years 2000 and 2100, we project a very likely (90% probability) GSL rise of 0.5-1.2 m under representative concentration pathway (RCP) 8.5, 0.4-0.9 m under RCP 4.5, and 0.3-0.8 m under RCP 2.6. Site-to-site differences in LSL projections are due to varying non-climatic background uplift or subsidence, oceanographic effects, and spatially variable responses of the geoid and the lithosphere to shrinking land ice. The Antarctic ice sheet (AIS) constitutes a growing share of variance in GSL and LSL projections. In the global average and at many locations, it is the dominant source of variance in late 21st century projections, though at some sites oceanographic processes contribute the largest share throughout the century. LSL rise dramatically reshapes flood risk, greatly increasing the expected number of "1-in-10" and "1-in-100" year events.

Astrochronology of the Anisian stage (Middle Triassic) at the Guandao reference section, South China

NASA Astrophysics Data System (ADS)

Li, Mingsong; Huang, Chunju; Hinnov, Linda; Chen, Weizhe; Ogg, James; Tian, Wei

2018-01-01

A high-precision global timescale for the Early and Middle Triassic is the key to understanding the nature, pattern and rates of biotic recovery following the end-Permian mass extinction. The Guandao section of Guizhou Province of South China is an important reference section for the magnetic polarity pattern, conodont datums, geochemical anomalies and interpreted temperature history through the Anisian (Middle Triassic). We analyzed the high-resolution gamma-ray and magnetic susceptibility series from the complete Anisian stage. Intensity variations are indicative of fluctuating terrestrial clay influxes showing strong signals that match predicted astronomical solutions for eccentricity and precession. Astronomical tuning of these series to interpreted 405-kyr long-eccentricity cycles yields a 5.3 Myr duration for the Anisian at Guandao. When combined with the astrochronology of the Early Triassic, then the projected age of the Anisian-Ladinian boundary relative to the base-Triassic date of 251.9 Ma is 241.5 ± 0.1 Ma. This provides a 10-Myr reference timescale for other key geological events, including conodont zones, geomagnetic polarity chrons, rates of marine carbon- and oxygen isotope excursions and global sea-level changes, that were associated with the repeated biotic crises and recovery episodes after the end-Permian mass extinction. The middle Anisian humid phase in ca. 244-244.5 Ma was probably a global event, which may have been linked to the middle Anisian warming event and sea-level change. Sea-level fluctuations at Guandao generally correlate with those in western Tethyan and Boreal regions in time, confirming sea-level changes during the Anisian were of eustatic origin.

Supercontinent break-up: Causes and consequences

NASA Astrophysics Data System (ADS)

Li, Z. X.

2014-12-01

Supercontinent break-up has most commonly been linked to plume or superplume events, and/or supercontinent thermal insulation, but precise mechanisms are yet to be worked out. Even less know is if and what roles other factors may play. Key factors likely include gravitational force due to the continental superswell driven by both the lower-mantle superplume and continental thermal insulation, mental convention driven by the superplume and individual plumes atop the superplume, assisted by thermal/magmatic weakening of the supercontinent interior (both plume heat and thermal insulation heat). In addition, circum-supercontinent slab downwelling may not only drive the formation of the antipodal superplumes (thus the break-up of the supercontinent), the likely roll-back of the subduction system would also create extension within the supercontinent, facilitating supercontinent break-up. Consequences of supercontinent break-up include long-term sea-level rise, climatic changes due to changes in ocean circulation pattern and carbon cycle, and biodiversification. It has long been demonstrated that the existence of the supercontinent Pangea corresponds to a long-term sea-level drop, whereas the break-up of the supercontinent corresponds to a long-term sea-level rise (170 m higher than it is today). A recent analysis of Neoproterozoic sedimentary facies illustrates that the time of Neoproterozoic supercontinent Rodinia corresponds to a low in the percentage of deep marine facies occurrence, whereas the time of Rodinia break-up corresponds to a significantly higher percentage of deep marine facies occurrence. The long-tern sea-level drop during supercontinent times were likely caused by both plume/superplume dynamic topography and an older mean age of the oceanic crust, whereas long-tern sea-level rise during supercontinent break-up (720-580 Ma for Rodinia and Late Jurassic-Cretaceous for Pangea) likely corresponds to an younger mean age of the oceanic crust, massive plume-induced magmatism in the oceans, and perhaps the effect of continents drifting away from a weakening sub-supercontinent superplume.

50 CFR 635.30 - Possession at sea and landing.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 8 2010-10-01 2010-10-01 false Possession at sea and landing. 635.30....30 Possession at sea and landing. Link to an amendment published at 75 FR 57702, Sept. 22, 2010. (a... Atlantic coastal port, including ports in the Gulf of Mexico and Caribbean Sea, must have all fins and...

50 CFR 648.74 - Shucking at sea.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 10 2011-10-01 2011-10-01 false Shucking at sea. 648.74 Section 648.74... Clam and Ocean Quahog Fisheries § 648.74 Shucking at sea. Link to an amendment published at 76 FR 60623... ocean quahogs at sea if he/she determines that an observer carried aboard the vessel can measure...

Measurements of sea ice mass redistribution during ice deformation event in Arctic winter

NASA Astrophysics Data System (ADS)

Itkin, P.; Spreen, G.; King, J.; Rösel, A.; Skourup, H.; Munk Hvidegaard, S.; Wilkinson, J.; Oikkonen, A.; Granskog, M. A.; Gerland, S.

2016-12-01

Sea-ice growth during high winter is governed by ice dynamics. The highest growth rates are found in leads that open under divergent conditions, where exposure to the cold atmosphere promotes thermodynamic growth. Additionally ice thickens dynamically, where convergence causes rafting and ridging. We present a local study of sea-ice growth and mass redistribution between two consecutive airborne measurements, on 19 and 24 April 2015, during the N-ICE2015 expedition in the area north of Svalbard. Between the two overflights an ice deformation event was observed. Airborne laser scanner (ALS) measurements revisited the same sea-ice area of approximately 3x3 km. By identifying the sea surface within the ALS measurements as a reference the sea ice plus snow freeboard was obtained with a spatial resolution of 5 m. By assuming isostatic equilibrium of level floes, the freeboard heights can be converted to ice thickness. The snow depth is estimated from in-situ measurements. Sea ice thickness measurements were made in the same area as the ALS measurements by electromagnetic sounding from a helicopter (HEM), and with a ground-based device (EM31), which allows for cross-validation of the sea-ice thickness estimated from all 3 procedures. Comparison of the ALS snow freeboard distributions between the first and second overflight shows a decrease in the thin ice classes and an increase of the thick ice classes. While there was no observable snowfall and a very low sea-ice growth of older level ice during this period, an autonomous buoy array deployed in the surroundings of the area measured by the ALS shows first divergence followed by convergence associated with shear. To quantify and link the sea ice deformation with the associated sea-ice thickness change and mass redistribution we identify over 100 virtual buoys in the ALS data from both overflights. We triangulate the area between the buoys and calculate the strain rates and freeboard change for each individual triangle. From the freeboard change we calculate the sea ice volume change. Our results show exemplary sea-ice mass redistribution caused by sea ice dynamics during winter conditions in the Arctic, which can be used to estimate sea-ice growth due to deformation processes in a wider region, and ultimately to distinguish between thermodynamic and dynamic ice growth processes.

Increased threat of tropical cyclones and coastal flooding to New York City during the anthropogenic era.

PubMed

Reed, Andra J; Mann, Michael E; Emanuel, Kerry A; Lin, Ning; Horton, Benjamin P; Kemp, Andrew C; Donnelly, Jeffrey P

2015-10-13

In a changing climate, future inundation of the United States' Atlantic coast will depend on both storm surges during tropical cyclones and the rising relative sea levels on which those surges occur. However, the observational record of tropical cyclones in the North Atlantic basin is too short (A.D. 1851 to present) to accurately assess long-term trends in storm activity. To overcome this limitation, we use proxy sea level records, and downscale three CMIP5 models to generate large synthetic tropical cyclone data sets for the North Atlantic basin; driving climate conditions span from A.D. 850 to A.D. 2005. We compare pre-anthropogenic era (A.D. 850-1800) and anthropogenic era (A.D.1970-2005) storm surge model results for New York City, exposing links between increased rates of sea level rise and storm flood heights. We find that mean flood heights increased by ∼1.24 m (due mainly to sea level rise) from ∼A.D. 850 to the anthropogenic era, a result that is significant at the 99% confidence level. Additionally, changes in tropical cyclone characteristics have led to increases in the extremes of the types of storms that create the largest storm surges for New York City. As a result, flood risk has greatly increased for the region; for example, the 500-y return period for a ∼2.25-m flood height during the pre-anthropogenic era has decreased to ∼24.4 y in the anthropogenic era. Our results indicate the impacts of climate change on coastal inundation, and call for advanced risk management strategies.

Increased threat of tropical cyclones and coastal flooding to New York City during the anthropogenic era

PubMed Central

Reed, Andra J.; Mann, Michael E.; Emanuel, Kerry A.; Lin, Ning; Horton, Benjamin P.; Kemp, Andrew C.; Donnelly, Jeffrey P.

2015-01-01

In a changing climate, future inundation of the United States’ Atlantic coast will depend on both storm surges during tropical cyclones and the rising relative sea levels on which those surges occur. However, the observational record of tropical cyclones in the North Atlantic basin is too short (A.D. 1851 to present) to accurately assess long-term trends in storm activity. To overcome this limitation, we use proxy sea level records, and downscale three CMIP5 models to generate large synthetic tropical cyclone data sets for the North Atlantic basin; driving climate conditions span from A.D. 850 to A.D. 2005. We compare pre-anthropogenic era (A.D. 850–1800) and anthropogenic era (A.D.1970–2005) storm surge model results for New York City, exposing links between increased rates of sea level rise and storm flood heights. We find that mean flood heights increased by ∼1.24 m (due mainly to sea level rise) from ∼A.D. 850 to the anthropogenic era, a result that is significant at the 99% confidence level. Additionally, changes in tropical cyclone characteristics have led to increases in the extremes of the types of storms that create the largest storm surges for New York City. As a result, flood risk has greatly increased for the region; for example, the 500-y return period for a ∼2.25-m flood height during the pre-anthropogenic era has decreased to ∼24.4 y in the anthropogenic era. Our results indicate the impacts of climate change on coastal inundation, and call for advanced risk management strategies. PMID:26417111

Predicting the persistence of coastal wetlands to global change stressors

USGS Publications Warehouse

Guntenspergen, G.; McKee, K.; Cahoon, D.; Grace, J.; Megonigal, P.

2006-01-01

Despite progress toward understanding the response of coastal wetlands to increases in relative sea-level rise and an improved understanding of the effect of elevated CO2 on plant species allocation patterns, we are limited in our ability to predict the response of coastal wetlands to the effects associated with global change. Static simulations of the response of coastal wetlands to sea-level rise using LIDAR and GIS lack the biological and physical feedback mechanisms present in such systems. Evidence from current research suggests that biotic processes are likely to have a major influence on marsh vulnerability to future accelerated rates of sea-level rise and the influence of biotic processes likely varies depending on hydrogeomorphic setting and external stressors. We have initiated a new research approach using a series of controlled mesocosm and field experiments, landscape scale studies, a comparative network of brackish coastal wetland monitoring sites and a suite of predictive models that address critical questions regarding the vulnerability of coastal brackish wetland systems to global change. Specifically, this research project evaluates the interaction of sea level rise and elevated CO2 concentrations with flooding, nutrient enrichment and disturbance effects. The study is organized in a hierarchical structure that links mesocosm, field, landscape and biogeographic levels so as to provide important new information that recognizes that coastal wetland systems respond to multiple interacting drivers and feedback effects controlling wetland surface elevation, habitat stability and ecosystem function. We also present a new statistical modelling technique (Structural Equation Modelling) that synthesizes and integrates our environmental and biotic measures in a predictive framework that forecasts ecosystem change and informs managers to consider adaptive shifts in strategies for the sustainable management of coastal wetlands.

Indonesian Throughflow variability over the last glacial cycle (Invited)

NASA Astrophysics Data System (ADS)

Holbourn, A. E.; Kuhnt, W.; Regenberg, M.; Xu, J.; Hendrizan, M.; Schröder, J.

2013-12-01

The transfer of surface and intermediate waters from the Pacific Ocean to the Indian Ocean through the Indonesian archipelago (Indonesian Throughflow: ITF) strongly influences the heat and freshwater budgets of tropical water masses, in turn affecting global climate. Key areas for monitoring past ITF variations through this critical gateway are the narrow passages through the Makassar Strait and Flores Sea and the main outflow area within the Timor Sea. Here, we integrate high-resolution sea surface temperature and salinity reconstructions (based on paired planktic foraminiferal Mg/Ca and δ18O) with X-ray fluorescence runoff data and benthic isotopes from marine sediment cores retrieved in these regions during several cruises with RV'Sonne' and RV'Marion Dufresne'. Our results show that high latitude climate variability strongly influenced ITF intensity on millennial to centennial timescales as well as on longer glacial-interglacial timescales. Marked declines in ITF strength occurred during Heinrich events and the Younger Dryas, most likely related to slowdown of the global thermohaline circulation during colder northern hemisphere climate spells, when deep water production decreased and the deep ocean became more stratified. Additionally, the surface component of the ITF strongly reflects regional windstress and rainfall patterns, and thus the spatial extent and intensity of the tropical convection over the Indonesian archipelago. Our runoff and salinity estimates reveal that the development of the tropical convection was intricately linked to the latitudinal migration of the Inter Tropical Convergence Zone (ITCZ). In particular, our data show that the Australian monsoon intensified during the major deglacial atmospheric CO2 rise through the Younger Dryas and earliest Holocene (12.9-10 ka). This massive intensification of the Australian monsoon coincided with a southward shift of the ITCZ, linked to southern hemisphere warming and enhanced greenhouse forcing over the Australian continent. However, the development of the monsoon was asynchronous over the region, which we relate to changes in landmass exposure during deglacial sea-level rise. Thus, we find that sea-level exerted a major control on ITF properties through the last glacial termination by altering gateway configuration and precipitation-evaporation budgets over the Indonesian archipelago.

Predicting habitat distribution to conserve seagrass threatened by sea level rise

NASA Astrophysics Data System (ADS)

Saunders, M. I.; Baldock, T.; Brown, C. J.; Callaghan, D. P.; Golshani, A.; Hamylton, S.; Hoegh-guldberg, O.; Leon, J. X.; Lovelock, C. E.; Lyons, M. B.; O'Brien, K.; Mumby, P.; Phinn, S. R.; Roelfsema, C. M.

2013-12-01

Sea level rise (SLR) over the 21st century will cause significant redistribution of valuable coastal habitats. Seagrasses form extensive and highly productive meadows in shallow coastal seas support high biodiversity, including economically valuable and threatened species. Predictive habitat models can inform local management actions that will be required to conserve seagrass faced with multiple stressors. We developed novel modelling approaches, based on extensive field data sets, to examine the effects of sea level rise and other stressors on two representative seagrass habitats in Australia. First, we modelled interactive effects of SLR, water clarity and adjacent land use on estuarine seagrass meadows in Moreton Bay, Southeast Queensland. The extent of suitable seagrass habitat was predicted to decline by 17% by 2100 due to SLR alone, but losses were predicted to be significantly reduced through improvements in water quality (Fig 1a) and by allowing space for seagrass migration with inundation. The rate of sedimentation in seagrass strongly affected the area of suitable habitat for seagrass in sea level rise scenarios (Fig 1b). Further research to understand spatial, temporal and environmental variability of sediment accretion in seagrass is required. Second, we modelled changes in wave energy distribution due to predicted SLR in a linked coral reef and seagrass ecosystem at Lizard Island, Great Barrier Reef. Scenarios where the water depth over the coral reef deepened due to SLR and minimal reef accretion, resulted in larger waves propagating shoreward, changing the existing hydrodynamic conditions sufficiently to reduce area of suitable habitat for seagrass. In a scenario where accretion of the coral reef was severely compromised (e.g. warming, acidification, overfishing), the probability of the presence of seagrass declined significantly. Management to maintain coral health will therefore also benefit seagrasses subject to SLR in reef environments. Further disentangling direct and indirect effects of climate change on seagrass will be necessary to inform management of these valuable coastal ecosystems. Models such as these will be important sources of information for management agencies, which require specific information on the likely impacts of sea level rise in coastal areas.

Error Characterization of Altimetry Measurements at Climate Scales

NASA Astrophysics Data System (ADS)

Ablain, Michael; Larnicol, Gilles; Faugere, Yannice; Cazenave, Anny; Meyssignac, Benoit; Picot, Nicolas; Benveniste, Jerome

2013-09-01

Thanks to studies performed in the framework of the SALP project (supported by CNES) since the TOPEX era and more recently in the framework of the Sea- Level Climate Change Initiative project (supported by ESA), strong improvements have been provided on the estimation of the global and regional mean sea level over the whole altimeter period for all the altimetric missions. Thanks to these efforts, a better characterization of altimeter measurements errors at climate scales has been performed and presented in this paper. These errors have been compared to user requirements in order to know if scientific goals are reached by altimeter missions. The main issue of this paper is the importance to enhance the link between altimeter and climate communities to improve or refine user requirements, to better specify future altimeter system for climate applications but also to reprocess older missions beyond their original specifications.

Long-term increases in young-of-the-year growth of Arctic cisco Coregonus autumnalis and environmental influences

USGS Publications Warehouse

Von Biela, V.R.; Zimmerman, C.E.; Moulton, L.L.

2011-01-01

Arctic cisco Coregonus autumnalis young-of-year (YOY) growth was used as a proxy to examine the long-term response of a high-latitude fish population to changing climate from 1978 to 2004. YOY growth increased over time (r2 = 0??29) and was correlated with monthly averages of the Arctic oscillation index, air temperature, east wind speed, sea-ice concentration and river discharge with and without time lags. Overall, the most prevalent correlates to YOY growth were sea-ice concentration lagged 1 year (significant correlations in 7 months; r2 = 0??14-0??31) and Mackenzie River discharge lagged 2 years (significant correlations in 8 months; r2 = 0??13-0??50). The results suggest that decreased sea-ice concentrations and increased river discharge fuel primary production and that life cycles of prey species linking increased primary production to fish growth are responsible for the time lag. Oceanographic studies also suggest that sea ice concentration and fluvial inputs from the Mackenzie River are key factors influencing productivity in the Beaufort Sea. Future research should assess the possible mechanism relating sea ice concentration and river discharge to productivity at upper trophic levels. Journal of Fish Biology ?? 2010 The Fisheries Society of the British Isles. No claim to original US government works.

Large-scale impacts of sea star wasting disease (SSWD) on intertidal sea stars and implications for recovery

PubMed Central

Burnaford, Jennifer L.; Ambrose, Richard F.; Antrim, Liam; Bohlmann, Heath; Blanchette, Carol A.; Engle, John M.; Fradkin, Steven C.; Gaddam, Rani; Harley, Christopher D. G.; Miner, Benjamin G.; Murray, Steven N.; Smith, Jayson R.; Whitaker, Stephen G.; Raimondi, Peter T.

2018-01-01

Disease outbreaks can have substantial impacts on wild populations, but the often patchy or anecdotal evidence of these impacts impedes our ability to understand outbreak dynamics. Recently however, a severe disease outbreak occurred in a group of very well-studied organisms–sea stars along the west coast of North America. We analyzed nearly two decades of data from a coordinated monitoring effort at 88 sites ranging from southern British Columbia to San Diego, California along with 2 sites near Sitka, Alaska to better understand the effects of sea star wasting disease (SSWD) on the keystone intertidal predator, Pisaster ochraceus. Quantitative surveys revealed unprecedented declines of P. ochraceus in 2014 and 2015 across nearly the entire geographic range of the species. The intensity of the impact of SSWD was not uniform across the affected area, with proportionally greater population declines in the southern regions relative to the north. The degree of population decline was unrelated to pre-outbreak P. ochraceus density, although these factors have been linked in other well-documented disease events. While elevated seawater temperatures were not broadly linked to the initial emergence of SSWD, anomalously high seawater temperatures in 2014 and 2015 might have exacerbated the disease’s impact. Both before and after the onset of the SSWD outbreak, we documented higher recruitment of P. ochraceus in the north than in the south, and while some juveniles are surviving (as evidenced by transition of recruitment pulses to larger size classes), post-SSWD survivorship is lower than during pre-SSWD periods. In hindsight, our data suggest that the SSWD event defied prediction based on two factors found to be important in other marine disease events, sea water temperature and population density, and illustrate the importance of surveillance of natural populations as one element of an integrated approach to marine disease ecology. Low levels of SSWD-symptomatic sea stars are still present throughout the impacted range, thus the outlook for population recovery is uncertain. PMID:29558484

Linking benthic biodiversity and environmental conditions at the sea floor combining statistical and mechanistic modeling. Case study on the Black Sea's northwestern shelf.

NASA Astrophysics Data System (ADS)

Drion, Roxanne; Capet, Arthur; Gregoire, Marilaure

2014-05-01

The preservation of the health and biodiversity of benthic ecosystems is a crucial priority in order to achieve the Good Environmental Status (GES) of marine waters. The multiple pressures acting on the ocean, and in particular, on the coastal zone may prevent the maintenance of biodiversity either directly (e.g. trawling, dredging) or indirectly by modifying environmental conditions at the sea floor (e.g. eutrophication, pollution, acidification, warming). The management of the GES of the benthos in a changing environment and the definition of management strategies (e.g. nutrient reduction) that would preserve GES require tools able to predict the modifications of environmental conditions and to link these modifications to the status of the benthic system. Coupled biogeochemical-circulation models provide a large amount of information on physical (e.g. currents, salinity, temperature, shear stress) and biochemical conditions (e.g. oxygen, inorganic nutrients, sinking detritus) but cannot provide an information on species richness. We propose to link these aspects by applying canonical ordination techniques (e.g. Redundancy Analysis, CoInertia Analysis) on a large data set on macrobenthos collected on the Black Sea's north-western shelf with in-situ sediment data (e.g. granulometry, carbon and nitrogen content, C/N ratio, CaCO3 content) and bottom conditions (e.g. shear stress, level of oxygen stress, flux of organic matter to the sediments) provided by a three dimensional model. Beyond taxonomic description, the analysis is performed on the functional composition of the macrobenthos: A trait-based approach is used to assess the functional composition of the macrobenthos by associating the considered species to a list of biological, ecological and behavioral traits. This approach allows to appraise how local conditions determine the functional and taxonomical diversity and provides a mean to evaluate the impact of habitat alteration on the ecological role of benthic assemblages. A particular attention is given to the influence of seasonal hypoxia on benthic biotopes composition.

Acoustic and optical variations during rapid downward motion episodes in the deep north-western Mediterranean Sea

NASA Astrophysics Data System (ADS)

van Haren, H.; Taupier-Letage, I.; Aguilar, J. A.; Albert, A.; Anghinolfi, M.; Anton, G.; Anvar, S.; Ardid, M.; Assis Jesus, A. C.; Astraatmadja, T.; Aubert, J.-J.; Auer, R.; Baret, B.; Basa, S.; Bazzotti, M.; Bertin, V.; Biagi, S.; Bigongiari, C.; Bou-Cabo, M.; Bouwhuis, M. C.; Brown, A.; Brunner, J.; Busto, J.; Camarena, F.; Capone, A.; Carminati, G.; Carr, J.; Castel, D.; Castorina, E.; Cavasinni, V.; Cecchini, S.; Charvis, Ph.; Chiarusi, T.; Circella, M.; Coniglione, R.; Costantini, H.; Cottini, N.; Coyle, P.; Curtil, C.; de Bonis, G.; Decowski, M. P.; Dekeyser, I.; Deschamps, A.; Distefano, C.; Donzaud, C.; Dornic, D.; Drouhin, D.; Eberl, T.; Emanuele, U.; Ernenwein, J.-P.; Escoffier, S.; Fehr, F.; Flaminio, V.; Fratini, K.; Fritsch, U.; Fuda, J.-L.; Giacomelli, G.; Gómez-González, J. P.; Graf, K.; Guillard, G.; Halladjian, G.; Hallewell, G.; Heijboer, A. J.; Hello, Y.; Hernández-Rey, J. J.; Hößl, J.; de Jong, M.; Kalantar-Nayestanaki, N.; Kalekin, O.; Kappes, A.; Katz, U.; Kooijman, P.; Kopper, C.; Kouchner, A.; Kretschmer, W.; Lahmann, R.; Lamare, P.; Lambard, G.; Larosa, G.; Laschinsky, H.; Lefèvre, D.; Lelaizant, G.; Lim, G.; Lo Presti, D.; Loehner, H.; Loucatos, S.; Lucarelli, F.; Lyons, K.; Mangano, S.; Marcelin, M.; Margiotta, A.; Martinez-Mora, J. A.; Maurin, G.; Mazure, A.; Melissas, M.; Montaruli, T.; Morganti, M.; Moscoso, L.; Motz, H.; Naumann, C.; Neff, M.; Ostasch, R.; Palioselitis, G.; Păvălaş, G. E.; Payre, P.; Petrovic, J.; Piattelli, P.; Picot-Clemente, N.; Picq, C.; Pillet, R.; Popa, V.; Pradier, T.; Presani, E.; Racca, C.; Radu, A.; Reed, C.; Riccobene, G.; Richardt, C.; Rujoiu, M.; Russo, G. V.; Salesa, F.; Schoeck, F.; Schuller, J.-P.; Shanidze, R.; Simeone, F.; Spurio, M.; Steijger, J. J. M.; Stolarczyk, Th.; Tamburini, C.; Tasca, L.; Toscano, S.; Vallage, B.; van Elewyck, V.; Vecchi, M.; Vernin, P.; Wijnker, G.; de Wolf, E.; Yepes, H.; Zaborov, D.; Zornoza, J. D.; Zúñiga, J.

2011-08-01

An Acoustic Doppler Current Profiler (ADCP) was moored at the deep-sea site of the ANTARES neutrino telescope near Toulon, France, thus providing a unique opportunity to compare high-resolution acoustic and optical observations between 70 and 170 m above the sea bed at 2475 m. The ADCP measured downward vertical currents of magnitudes up to 0.03 m s-1 in late winter and early spring 2006. In the same period, observations were made of enhanced levels of acoustic reflection, interpreted as suspended particles including zooplankton, by a factor of about 10 and of horizontal currents reaching 0.35 m s-1. These observations coincided with high light levels detected by the telescope, interpreted as increased bioluminescence. During winter 2006 deep dense-water formation occurred in the Ligurian subbasin, thus providing a possible explanation for these observations. However, the 10-20 days quasi-periodic episodes of high levels of acoustic reflection, light and large vertical currents continuing into the summer are not direct evidence of this process. It is hypothesized that the main process allowing for suspended material to be moved vertically later in the year is local advection, linked with topographic boundary current instabilities along the rim of the 'Northern Current'.

SLIVISU, an Interactive Visualisation Framework for Analysis of Geological Sea-Level Indicators

NASA Astrophysics Data System (ADS)

Klemann, V.; Schulte, S.; Unger, A.; Dransch, D.

2011-12-01

Flanking data analysis in earth system sciences by advanced visualisation tools is a striking feature due to rising complexity, amount and variety of available data. With respect to sea-level indicators (SLIs), their analysis in earth-system applications, such as modelling and simulation on regional or global scales, demands the consideration of large amounts of data - we talk about thousands of SLIs - and, so, to go ahead of analysing single sea-level curves. On the other hand, a gross analysis by means of statistical methods is hindered by the often heterogeneous and individual character of the single SLIs, i.e., the spatio-temporal context and often heterogenous information is difficult to handle or to represent in an objective way. Therefore a concept of integrating automated analysis and visualisation is mandatory. This is provided by visual analytics. As an implementation of this concept, we present the visualisation framework SLIVISU, developed at GFZ, which bases on multiple linked views and provides a synoptic analysis of observational data, model configurations, model outputs and results of automated analysis in glacial isostatic adjustment. Starting as a visualisation tool for an existing database of SLIs, it now serves as an analysis tool for the evaluation of model simulations in studies of glacial-isostatic adjustment.

Fishing for biodiversity: Novel methanopterin-linked C1 transfergenes deduced from the Sargasso Sea metagenome

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalyuzhnaya, Marina G.; Nercessian, Olivier; Lapidus, Alla

2004-07-01

The recently generated database of microbial genes from anoligotrophic environment populated by a calculated 1,800 of major phylotypes (the Sargasso Sea metagenome) presents a great source for expanding local databases of genes indicative of a specific function. In this paper we analyze the Sargasso Sea metagenome in terms of the presence of methanopterin-linked C1 transfer genes that are signature for methylotrophy. We conclude that more than 10 phylotypes possessing genes of interest are present in this environment, and a few of these are relatively abundant species. The sequences representative of the major phylotypes do not appear to belong to anymore » known microbial group capable of methanopterin-linked C1 transfer. Instead, they separate from all known sequences on phylogenetic trees, pointing towards their affiliation with a novel microbial phylum. These data imply a broader distribution of methanopterin-linked functions in the microbial world than previously known.« less

Show Me The Data! Data Visualizations Make Climate Change & Climate Impacts Real

NASA Astrophysics Data System (ADS)

Turrin, M.; Ryan, W. B. F.; Porter, D. F.

2016-12-01

Today's learner is technology proficient. Whether we reference K12, undergraduate, or life long learners we expect that they are not only comfortable interacting with a range of digital media, from computer, to tablet, to a smart phone, but that they expect it. Technology is a central part of how most of us spend large portions of our day; connecting, communicating, recreating and learning. So why would we expect that today's learners would prefer to read about climate change and climate impacts from plain text? As educators we must embrace cutting edge methods and materials to engage our students and learners, meeting them where they are most comfortable. `Polar Explorer: Sea Level' is an app that uses interactive data maps to engage the users in the story of changing sea level. Designed for a general audience this free app (http://www.polarexplorer.org) is a great resource for life-long learners, teachers, students and the curious public. Built around a series of questions that are structured like book chapters, users select from a range of choices like: What is sea level? Why does sea level change? Where is it changing now? What about the polar regions? What about in the past? Who is vulnerable? Each section moves the user through layers of maps that address causes, impacts, future predictions and special vulnerabilities of a rising sea level. Users can select any pathway to build a story that captures their attention as they interact with the data and move through different layers of the app. Each map is interactive and supported by information 'snippits', audio clips and a link to further information. A series of `quests' are available for the app. Each quest is a story with a main science theme at its center that leads a planned excursion through a series of map layers while revealing a story in the data. The combination of physical science in what and where is sea level changing, with human impacts in the `who is vulnerable', builds a series of stories with a personal connection for the app user. Follow a quest to learn why sea level is falling on the Scandinavian coastline, or where you would find the highest mountain peak in Greenland or Antarctica. Users are encouraged to create their own quests and submit them to a shared repository. This app was developed as part of the PoLAR partnership supported by NSF (DUE-1239783).

Characterizing and minimizing the effects of noise in tide gauge time series: relative and geocentric sea level rise around Australia

NASA Astrophysics Data System (ADS)

Burgette, Reed J.; Watson, Christopher S.; Church, John A.; White, Neil J.; Tregoning, Paul; Coleman, Richard

2013-08-01

We quantify the rate of sea level rise around the Australian continent from an analysis of tide gauge and Global Positioning System (GPS) data sets. To estimate the underlying linear rates of sea level change in the presence of significant interannual and decadal variability (treated here as noise), we adopt and extend a novel network adjustment approach. We simultaneously estimate time-correlated noise as well as linear model parameters and realistic uncertainties from sea level time series at individual gauges, as well as from time-series differences computed between pairs of gauges. The noise content at individual gauges is consistent with a combination of white and time-correlated noise. We find that the noise in time series from the western coast of Australia is best described by a first-order Gauss-Markov model, whereas east coast stations generally exhibit lower levels of time-correlated noise that is better described by a power-law process. These findings suggest several decades of monthly tide gauge data are needed to reduce rate uncertainties to <0.5 mm yr-1 for undifferenced single site time series with typical noise characteristics. Our subsequent adjustment strategy exploits the more precise differential rates estimated from differenced time series from pairs of tide gauges to estimate rates among the network of 43 tide gauges that passed a stability analysis. We estimate relative sea level rates over three temporal windows (1900-2011, 1966-2011 and 1993-2011), accounting for covariance between time series. The resultant adjustment reduces the rate uncertainty across individual gauges, and partially mitigates the need for century-scale time series at all sites in the network. Our adjustment reveals a spatially coherent pattern of sea level rise around the coastline, with the highest rates in northern Australia. Over the time periods beginning in 1900, 1966 and 1993, we find weighted average rates of sea level rise of 1.4 ± 0.6, 1.7 ± 0.6 and 4.6 ± 0.8 mm yr-1, respectively. While the temporal pattern of the rate estimates is consistent with acceleration in sea level rise, it may not be significant, as the uncertainties for the shorter analysis periods may not capture the full range of temporal variation. Analysis of the available continuous GPS records that have been collected within 80 km of Australian tide gauges suggests that rates of vertical crustal motion are generally low, with the majority of sites showing motion statistically insignificant from zero. A notable exception is the significant component of vertical land motion that contributes to the rapid rate of relative sea level change (>4 mm yr-1) at the Hillarys site in the Perth area. This corresponds to crustal subsidence that we estimate in our GPS analysis at a rate of -3.1 ± 0.7 mm yr-1, and appears linked to groundwater withdrawal. Uncertainties on the rates of vertical displacement at GPS sites collected over a decade are similar to what we measure in several decades of tide gauge data. Our results motivate continued observations of relative sea level using tide gauges, maintained with high-accuracy terrestrial and continuous co-located satellite-based surveying.

Path homogeneity along a horizontal line-of-sight path during the FESTER experiment: first results

NASA Astrophysics Data System (ADS)

Gunter, W. H.; Maritz, B.; Koago, M.; Wainman, C. K.; Gardener, M. E.; February, F.; van Eijk, A. M. J.

2016-10-01

The First European South African Experiment (FESTER) was conducted over about a 10 month period at the Institute of Maritime Technology (IMT) in False Bay, South Africa. One of the important goals was the establishment of the air-sea temperature difference (ASTD) homogeneity along the main propagation link atmospheric path since it is a basic assumption for most of the atmospheric turbulence models (caused by refractive index variations). The ASTD was measured from a small scientific work boat (called Sea Lab) moving along a straight in- and outbound track along the main propagation link path. The air temperature on-board was measured using standard weather sensors, while the sea surface temperature was measured using a long wavelength infrared radiometer, which was compared to the bulk sea temperature half a meter below the sea surface. This was obtained by an under water temperature sensor mounted on a `surfboard' that was towed alongside Sea Lab. Vertical water temperature profiles were also measured along the main propagation path in order to determine the depth of the surface mixed layer and thermocline using a Conductivity Temperature Depth profiler (CTD). First results investigated the ASTD variation along the horizontal line-of-sight path used by the principal electro-optic transmission link monitoring equipment (i.e. scintillometer and multi-spectral radiometer-transmissometer system).

Release strategies for rehabilitated sea otters

USGS Publications Warehouse

DeGange, Anthony R.; Ballachey, Brenda E.; Bayha, Keith; Williams, Terrie M.; Davis, Randall W.

1995-01-01

According to the U.S. Fish and Wildlife Services’ (USFWS) Response Plan for sea otters (USFWS, in preparation), in the event of an oil spill, the decision to release sea otters from rehabilitation centers following treatment will be linked to the decision on whether to capture sea otters for treatment. Assuming a scenario similar to the Exxon Valdez oil spill (EVOS), once the decision to capture sea otters is made, the ultimate goal is to return as many sea otters to the wild as possible, even though the rescue may not be expected to produce results significant at the population level. The decision by the USFWS to proceed with capture, rehabilitation, and release will be made on a case-by-case basis (USFWS, in preparation). Many factors will influence the decision. Perhaps the most important factors in deciding when and where to release sea otters are the location and availability of suitable release sites and verification that the otters are free of diseases that might be transmitted to the wild population.Alternative release strategies for sea otters will be contained in the sea otter response portion of the USFWS’s oil spill contingency plans for Alaska and California that are being developed as required by the Oil Pollution Act of 1990. Public review of these plans before they are implemented will help to reduce public concern about the survival of rehabilitated otters, their biological effect on the release area, and the potential introduction or spread of disease into the wild sea otter population.The objective of this chapter is to review alternative strategies for the disposition of rehabilitated sea otters. Our assumption is that returning as many animals to the wild as possible, whether it be for humanitarian or biological reasons, is the ultimate goal of this effort (Figure 10.1).

Astaxanthin dynamics in Baltic Sea mesozooplankton communities

NASA Astrophysics Data System (ADS)

Snoeijs, Pauline; Häubner, Norbert

2014-01-01

The red pigment astaxanthin is a powerful antioxidant, which occurs in eggs and body tissues of crustaceans and fish. It is produced by crustaceans from algal carotenoids. In a two-year field study we assessed natural concentrations and dynamics of astaxanthin in mesozooplankton communities in the brackish Baltic Sea area. Astaxanthin levels varied between 0.37 and 36 ng L- 1. They increased with salinity along the Baltic Sea gradient and were linked to zooplankton biomass and phytoplankton community composition. Astaxanthin concentrations showed typical seasonal patterns and varied from 0.2 to 5.1 ng ind- 1, 0.2 to 3.4 ng (μg C)- 1 and 6 to 100 ng mm- 3. These concentrations were inversely related to water temperature and strongly linked to zooplankton community composition. Communities dominated by the calanoid copepods Temora longicornis, Pseudocalanus acuspes and Eurytemora spp. generally held the highest concentrations. With increasing cladocerans:copepods biomass ratios community astaxanthin concentrations decreased and with higher relative biomass of Acartia spp. the proportion of astaxanthin diesters decreased. Diesters prevailed in the cold season and they are thought to improve the antioxidant protection of storage lipids during winter. Climate change causes higher temperature and lower salinity in the Baltic Sea proper. This modifies zooplankton community composition, but not necessarily into a community with lower concentrations of astaxanthin since T. longicornis (high concentrations) has been reported to increase with higher temperature. However, decreased astaxanthin production in the ecosystem is expected if a basin-wide increase in the cladocerans:copepods biomass ratios would occur with further climate change.

Midwater Bioluminescence Assessment in the West Alboran Gyre (Mediterranean Sea)

DTIC Science & Technology

1991-09-01

of bioluminescence.I KEYWORDS I ALBORAN SEA JOHNSON-SEA-LINK BATHYPHOTOMETER MEDUSAE BIOLUMINESCENCE SEWARD JOHNSON I RV CTENOPHORES SIPHONOPHORES ...30 C tenophores................................................................ 32 Siphonophores ...good, however, for ctenophores, salps, siphonophores and medusae. Table 2 Specimen No. Genus, Spec!es Taxon I 1896 12 Sappharina sp. Copepod 1896 32b

Mechanisms of interannual- to decadal-scale winter Labrador Sea ice variability

NASA Astrophysics Data System (ADS)

Close, S.; Herbaut, C.; Houssais, M.-N.; Blaizot, A.-C.

2017-12-01

The variability of the winter sea ice cover of the Labrador Sea region and its links to atmospheric and oceanic forcing are investigated using observational data, a coupled ocean-sea ice model and a fully-coupled model simulation drawn from the CMIP5 archive. A consistent series of mechanisms associated with high sea ice cover are found amongst the various data sets. The highest values of sea ice area occur when the northern Labrador Sea is ice covered. This region is found to be primarily thermodynamically forced, contrasting with the dominance of mechanical forcing along the eastern coast of Baffin Island and Labrador, and the growth of sea ice is associated with anomalously fresh local ocean surface conditions. Positive fresh water anomalies are found to propagate to the region from a source area off the southeast Greenland coast with a 1 month transit time. These anomalies are associated with sea ice melt, driven by the enhanced offshore transport of sea ice in the source region, and its subsequent westward transport in the Irminger Current system. By combining sea ice transport through the Denmark Strait in the preceding autumn with the Greenland Blocking Index and the Atlantic Multidecadal Oscillation Index, strong correlation with the Labrador Sea ice area of the following winter is obtained. This relationship represents a dependence on the availability of sea ice to be melted in the source region, the necessary atmospheric forcing to transport this offshore, and a further multidecadal-scale link with the large-scale sea surface temperature conditions.

Launch and on-orbit checkout of Aquarius/SAC-D Observatory: an international remote sensing satellite mission measuring sea surface salinity

NASA Astrophysics Data System (ADS)

Sen, Amit; Caruso, Daniel; Durham, David; Falcon, Carlos

2011-11-01

The Aquarius/SAC-D observatory was launch in June 2011 from Vandenberg Air Force Base (VAFB), in California, USA. This mission is the fourth joint earth-observation endeavor between NASA and CONAE. The primary objective of the Aquarius/SAC-D mission is to investigate the links between global water cycle, ocean circulation and climate by measuring Sea Surface Salinity (SSS). Over the last year, the observatory successfully completed system level environmental and functional testing at INPE, Brazil and was transported to VAFB for launch operations. This paper will present the challenges of this mission, the system, the preparation of the spacecraft, instruments, testing, launch, inorbit checkout and commissioning of this Observatory in space.

Links between the Amundsen Sea Low and sea ice in the Ross Sea: seasonal and interannual relationships

NASA Astrophysics Data System (ADS)

Raphael, Marilyn N.; Holland, Marika M.; Landrum, Laura; Hobbs, William R.

2018-05-01

Previous studies have shown that sea ice extent in the Southern Ocean is influenced by the intensity and location of the Amundsen Sea Low (ASL), through their effect on the meridional winds. However, the inhomogeneous nature of the influence of the ASL on sea ice as well as its influence during critical periods of the sea ice annual cycle is not clear. In this study, we do a spatio-temporal analysis of links between the ASL and the sea ice during the advance and retreat periods of the ice over the period 1979-2013 focusing on the role of the meridional and zonal winds. We use the ERA-Interim monthly-averaged 500 mb geopotential height and 10 m wind data along with monthly Passive Microwave Sea Ice Concentrations (SIC) to examine the seasonal and interannual relationships between the ASL and SIC in the Ross-Amundsen sea ice sector. To characterize the state of the ASL we use indices that describe its location and its intensity. We show that the ASL has preferred locations and intensities during ice advance and retreat seasons. The strength and direction of the influence of the ASL are not spatially homogeneous and can change from advance to retreat season and there are strong significant relationships between the characteristics of the ASL and SIC, within and across seasons and interannually.

Coastal zone - Terra (and aqua) incognita - Integrated Coastal Zone Management in the Black Sea

NASA Astrophysics Data System (ADS)

Kosyan, R. D.; Velikova, V. N.

2016-02-01

In the Black Sea coastal states (Bulgaria, Georgia, Romania, Russian Federation, Turkey, and Ukraine), Integrated Coastal Zone Management (ICZM) has no properly established legal and institutional framework. The term "coastal zone" is undefined in national (reportedly with the exception of Bulgaria) and regional legislative documents. The interface between science and policy within ICZM remains poorly developed. Policies for streamlining efforts have been ill-managed and decisions taken in functional zoning and the balanced use and protection of coastal zones have often been shown to be incorrect. The observed proliferation of consultative committees and councils has not been much helpful, public participation has been widely neglected. Illegal practices are in place, and coastal developments continue being largely unsustainable. These problems are often explained by the low awareness of ICZM benefits, and hence, a shortage of political good will, but also by the lack of appropriate Black Sea scientific research, which would ensure a fundamental knowledge-base. There are hundreds of organizations involved in collection of data and information of relevance for ICZM, although there is a distinct lack of coordination. Consequently, there is a substantial overlap of activities, whilst important scientific and policy questions remain unanswered. We review the status of ICZM or mismanagement (ICZmisM) in the Black Sea region, building links between environmental problems and policy measures in response, and providing appropriate examples. Recommendations are put forward with regard to major gaps in ICZM at levels of its theoretical development and practical implementation within the region. The review is intended to remind of major disastrous consequences of present complacency and laissez-faire in the management of the Black Sea. This paper calls for urgent implementation of ICZM in the Black Sea at national and regional levels.

A linked hydrodynamic and water quality model for the Salton Sea

USGS Publications Warehouse

Chung, E.G.; Schladow, S.G.; Perez-Losada, J.; Robertson, Dale M.

2008-01-01

A linked hydrodynamic and water quality model was developed and applied to the Salton Sea. The hydrodynamic component is based on the one-dimensional numerical model, DLM. The water quality model is based on a new conceptual model for nutrient cycling in the Sea, and simulates temperature, total suspended sediment concentration, nutrient concentrations, including PO4-3, NO3-1 and NH4+1, DO concentration and chlorophyll a concentration as functions of depth and time. Existing water temperature data from 1997 were used to verify that the model could accurately represent the onset and breakup of thermal stratification. 1999 is the only year with a near-complete dataset for water quality variables for the Salton Sea. The linked hydrodynamic and water quality model was run for 1999, and by adjustment of rate coefficients and other water quality parameters, a good match with the data was obtained. In this article, the model is fully described and the model results for reductions in external phosphorus load on chlorophyll a distribution are presented. ?? 2008 Springer Science+Business Media B.V.

Ecosystem Models as Support to Eutrophication Management in the North Atlantic Ocean (EMoSEM)

NASA Astrophysics Data System (ADS)

Lacroix, Geneviève; Billen, Gilles; Desmit, Xavier; Garnier, Josette; Gypens, Nathalie; Lancelot, Christiane; Lenhart, Hermann; Los, Hans; Mateus, Marcos; Ménesguen, Alain; Neves, Ramiro; Troost, Tineke; van der Molen, Johan

2013-04-01

One of the leading challenges in marine science and governance is to improve scientific guidance of management measures to mitigate eutrophication nuisances in the EU seas. Existing approaches do not integrate the eutrophication process in space (continuum river-ocean) and in time (past, present and future status). A strong need remains for (i) knowledge/identification of all the processes that control eutrophication and its consequences, (ii) consistent and harmonized reference levels assigned to each eutrophication-related indicator, (iii) identification of the main rivers directly or indirectly responsible for eutrophication nuisances in specific areas, (iv) an integrated transboundary approach and (v) realistic and scientific-based nutrient reduction scenarios. The SEAS-ERA project EMoSEM aims to develop and combine the state-of-the-art modelling tools describing the river-ocean continuum in the North-East Atlantic (NEA) continental seas. This will allow to link the eutrophication nuisances in specific marine regions to anthropogenic inputs, trace back their sources up to the watersheds, then test nutrient reduction options that might be implemented in these watersheds, and propose consistent indicators and reference levels to assess the Good Environmental Status (GES). At the end, EMoSEM will deliver coupled river-coastal-sea mathematical models and will provide guidance to end-users (policy- and decision makers) for assessing and combating eutrophication problems in the NEA continental waters.

Abrupt drainage cycles of the Fennoscandian Ice Sheet

PubMed Central

Soulet, Guillaume; Ménot, Guillemette; Bayon, Germain; Rostek, Frauke; Ponzevera, Emmanuel; Toucanne, Samuel; Lericolais, Gilles; Bard, Edouard

2013-01-01

Continental ice sheets are a key component of the Earth’s climate system, but their internal dynamics need to be further studied. Since the last deglaciation, the northern Eurasian Fennoscandian Ice Sheet (FIS) has been connected to the Black Sea (BS) watershed, making this basin a suitable location to investigate former ice-sheet dynamics. Here, from a core retrieved in the BS, we combine the use of neodymium isotopes, high-resolution elemental analysis, and biomarkers to trace changes in sediment provenance and river runoff. We reveal cyclic releases of meltwater originating from Lake Disna, a proglacial lake linked to the FIS during Heinrich Stadial 1. Regional interactions within the climate–lake–FIS system, linked to changes in the availability of subglacial water, led to abrupt drainage cycles of the FIS into the BS watershed. This phenomenon raised the BS water level by ∼100 m until the sill of the Bosphorus Strait was reached, flooding the vast northwestern BS shelf and deeply affecting the hydrology and circulation of the BS and, probably, of the Marmara and Aegean Seas. PMID:23569264

Abrupt drainage cycles of the Fennoscandian Ice Sheet.

PubMed

Soulet, Guillaume; Ménot, Guillemette; Bayon, Germain; Rostek, Frauke; Ponzevera, Emmanuel; Toucanne, Samuel; Lericolais, Gilles; Bard, Edouard

2013-04-23

Continental ice sheets are a key component of the Earth's climate system, but their internal dynamics need to be further studied. Since the last deglaciation, the northern Eurasian Fennoscandian Ice Sheet (FIS) has been connected to the Black Sea (BS) watershed, making this basin a suitable location to investigate former ice-sheet dynamics. Here, from a core retrieved in the BS, we combine the use of neodymium isotopes, high-resolution elemental analysis, and biomarkers to trace changes in sediment provenance and river runoff. We reveal cyclic releases of meltwater originating from Lake Disna, a proglacial lake linked to the FIS during Heinrich Stadial 1. Regional interactions within the climate-lake-FIS system, linked to changes in the availability of subglacial water, led to abrupt drainage cycles of the FIS into the BS watershed. This phenomenon raised the BS water level by ∼100 m until the sill of the Bosphorus Strait was reached, flooding the vast northwestern BS shelf and deeply affecting the hydrology and circulation of the BS and, probably, of the Marmara and Aegean Seas.

What have we learned? A review of the literature on children's health and the environment in the Aral Sea area.

PubMed

Crighton, Eric James; Barwin, Lynn; Small, Ian; Upshur, Ross

2011-04-01

To review the published literature examining the impacts of the Aral Sea disaster on children's health. A systematic review of the English language literature. The literature search uncovered 26 peer-reviewed articles and four major reports published between 1994 and 2008. Anemia, diarrheal diseases, and high body burdens of toxic contaminants were identified as being among the significant health problems for children. These problems are associated either directly with the environmental disaster or indirectly via the deterioration of the region's economy and social and health care services. While links between persistent organic pollutant exposures and body burdens are clear, health impacts remain poorly understood. No clear evidence for the link between dust exposure and respiratory function was identified. While important questions about the nature of the child health and environment relationships remain to be answered, the literature unequivocally illustrates the seriousness of the public health tragedy and provides sufficient evidence to justify immediate action. Regrettably, international awareness of the crisis continues to be poor, and the level of action addressing the situation is wholly inadequate.

Assessing economic impact of storm surge under projected sea level rise scenarios

NASA Astrophysics Data System (ADS)

Del Angel, D. C.; Yoskowitz, D.

2017-12-01

Global sea level is expected to rise 0.2-2m by the year 2100. Rising sea level is expected to have a number of impacts such as erosion, saltwater intrusion, and decline in coastal wetlands; all which have direct and indirect socio-economic impact to coastal communities. By 2050, 25% of the world's population will reside within flood-prone areas. These statistics raise a concern for the economic cost that sea level and flooding has on the growing coastal communities. Economic cost of storm surge inundation and rising seas may include loss or damage to public facilities and infrastructure that may become temporarily inaccessible, as well as disruptions to business and services. This goal of this project is to assess economic impacts of storms under four SLR scenarios including low, intermediate-low, intermediate-high, and high (0.2m, 0.5m, 1.2m and 2m, respectively) in the Northern Gulf of Mexico region. To assess flooding impact on communities from storm surge, this project utilizes HAZUS-MH software - a Geographic Information System (GIS)-based modeling tool developed by the Federal Emergency Management Agency - to estimate physical, economic, and social impacts of natural disasters such as floods, earthquakes and hurricanes. The HAZUS database comes integrated with aggregate and site specific inventory which includes: demographic data, general building stock, agricultural statistics, vehicle inventory, essential facilities, transportation systems, utility systems (among other sensitive facilities). User-defined inundation scenarios will serve to identify assets at risk and damage estimates will be generated using the Depth Damage Function included in the HAZUS software. Results will focus on 3 communities in the Gulf and highlight changes in storm flood impact. This approach not only provides a method for economic impact assessment but also begins to create a link between ecosystem services and natural and nature-based features such as wetlands, beaches and dunes. Results from this analysis can provide actionable information needed for policy development and planning for coastal communities.

A Dynamic Flood Inundation Model Framework to Assess Coastal Flood Risk in a Changing Climate

NASA Astrophysics Data System (ADS)

Bilskie, M. V.; Hagen, S. C.; Passeri, D. L.; Alizad, K.; Medeiros, S. C.; Irish, J. L.

2015-12-01

Coastal regions around the world are susceptible to a variety of natural disasters causing extreme inundation. It is anticipated that the vulnerability of coastal cities will increase due to the effects of climate change, and in particular sea level rise (SLR). A novel framework was developed to generate a suite of physics-based storm surge models that include projections of coastal floodplain dynamics under climate change scenarios: shoreline erosion/accretion, dune morphology, salt marsh migration, and population dynamics. First, the storm surge inundation model was extensively validated for present day conditions with respect to astronomic tides and hindcasts of Hurricane Ivan (2004), Dennis (2005), Katrina (2005), and Isaac (2012). The model was then modified to characterize the future outlook of the landscape for four climate change scenarios for the year 2100 (B1, B2, A1B, and A2), and each climate change scenario was linked to a sea level rise of 0.2 m, 0.5 m, 1.2 m, and 2.0 m. The adapted model was then used to simulate hurricane storm surge conditions for each climate scenario using a variety of tropical cyclones as the forcing mechanism. The collection of results shows the intensification of inundation area and the vulnerability of the coast to potential future climate conditions. The methodology developed herein to assess coastal flooding under climate change can be performed across any coastal region worldwide, and results provide awareness of regions vulnerable to extreme flooding in the future. Note: The main theme behind this work is to appear in a future Earth's Future publication. Bilskie, M. V., S. C. Hagen, S. C. Medeiros, and D. L. Passeri (2014), Dynamics of sea level rise and coastal flooding on a changing landscape, Geophysical Research Letters, 41(3), 927-934. Parris, A., et al. (2012), Global Sea Level Rise Scenarios for the United States National Climate AssessmentRep., 37 pp. Passeri, D. L., S. C. Hagen, M. V. Bilskie, and S. C. Medeiros (2014), On the significance of incorporating shoreline changes for evaluating coastal hydrodynamics under sea level rise scenarios, Natural Hazards, 1599-1617. Passeri, D. L., S. C. Hagen, S. C. Medeiros, M. V. Bilskie, K. Alizad, and D. Wang (2015), The dynamic effects of sea level rise on low gradient coastal landscapes: a review, Earth's Future, 3.

Interactive Sea Level Rise App & Online Viewer Offers Deep Dive Into Climate

NASA Astrophysics Data System (ADS)

Turrin, M.; Porter, D. F.; Ryan, W. B. F.; Pfirman, S. L.

2015-12-01

Climate has captured the attention of the public but its complexity can cause interested individuals to turn to opinion pieces, news articles or blogs for information. These platforms often oversimplify or present heavily interpreted or personalized perspectives. Data interactives are an extremely effective way to explore complex geoscience topics like climate, opening windows of understanding for the user that have previously been closed. Layering data onto maps through programs like GeoMapApp and the Earth Observer App has allowed users to dig directly into science data, but with only limited scaffolding. The interactive 'Polar Explorer: Sea Level Explorer App' provides a richly layered introduction to a range of topics connected to sea level rise. Each map is supported with a pop up and a short audio file of supplementary material, and an information page that includes the data source and links for further reading. This type of learning platform works well for both the formal and informal learning environment. Through science data displayed as map visualizations the user is invited into topics through an introductory question, such as "Why does sea level change?" After clicking on that question the user moves to a second layer of questions exploring the role of the ocean, the atmosphere, the contribution from the world's glaciers, world's ice sheets and other less obvious considerations such as the role of post-glacial rebound, or the mining of groundwater. Each question ends in a data map, or series of maps, that offer opportunities to interact with the topic. Under the role of the ocean 'Internal Ocean Temperature' offers the user a chance to touch to see temperature values spatially over the world's ocean, or to click through a data series starting at the ocean surface and diving to 5000 meters of depth showing how temperature changes with depth. Other sections, like the role of deglaciation of North America, allow the user to click and see change through time as the Laurentide ice sheet retreated, from 18,000 to 5,000 years ago, changing sea level as it melted. Interacting with the range of topics and the different data layers allows the user to see first hand how climate and sea level have changed through time and how it has, and does, vary around the world.

Early to Middle Holocene sea level fluctuation, coastal progradation and the Neolithic occupation in the Yaojiang Valley of southern Hangzhou Bay, Eastern China

NASA Astrophysics Data System (ADS)

Liu, Yan; Sun, Qianli; Fan, Daidu; Dai, Bin; Ma, Fuwei; Xu, Lichen; Chen, Jing; Chen, Zhongyuan

2018-06-01

The Yaojiang Valley (YJV) of southern Hangzhou Bay was the birthplace of the well-known Hemudu Culture (HC), one of the representatives of Neolithic civilization in eastern China. To explore the magnitude of natural environmental effects on the HC trajectory, the palaeo-embayment setting of the YJV was studied in detail for the first time in terms of 3D Holocene strata supported by a series of new radiocarbon-dated cores. The results indicated that the local relative sea level rose rapidly during the Early Holocene in the YJV, reached its maximum flooding surface ca. 7900 cal yr BP, and then remained stable ca. 7900-7600 cal yr BP. Thereupon, an estuary stretching inland was first formed by marine transgression, and then, it was transformed to an alluvial-coastal plain by regressive progradation. The alluvial plain was initiated in the foothills and then spread towards the valley centre after sea level stabilization ca. 7600 cal yr BP. Accompanying these natural environmental changes, the earliest arrivals of foragers in the valley occurred no later than ca. 7000 cal yr BP. They engaged in rice farming and fostered the HC for approximately two millennia from ca. 7000-5000 cal yr BP as more lands developed from coastal progradation. The rise and development of the HC are closely associated with the sea level-induced landscape changes in the YJV in the Early-Middle Holocene, but the enigmatic exodus of the HC people after ca. 5000 cal yr BP is still contentious and possibly linked with the rapid waterlogging and deterioration of this setting in such a low-lying coastal plain as well as with associated social reasons.

Deposition of a saline giant in the Mississippian Windsor Group, Nova Scotia, and the nascent Late Paleozoic Ice Age

NASA Astrophysics Data System (ADS)

MacNeil, Laura A.; Pufahl, Peir K.; James, Noel P.

2018-01-01

Saline giants are vast marine evaporite deposits that currently have no modern analogues and remain one of the most enigmatic of chemical sedimentary rocks. The Mississippian Windsor Group (ca. 345 Ma), Maritimes Basin, Atlantic Canada is a saline giant that consists of two evaporite-rich sedimentary sequences that are subdivided into five subzones. Sequence 1 is composed almost entirely of thick halite belonging to Subzone A (Osagean). Sequence 2 is in unconformable contact and comprised of stacked carbonate-evaporite peritidal cycles of Subzones B through E (Meramecian). Subzone B, the focus of research herein, documents the transition from wholly evaporitic to open marine conditions and thus, preserves an exceptional window into the processes forming saline giants. Lithofacies stacking patterns in Subzone B reveal that higher-order fluctuations in relative sea level produced nine stacked parasequences interpreted to reflect high frequency glacioeustatic oscillations during the onset of the Late Paleozoic Ice Age. Each parasequence reflects progradation of intertidal and sabkha sediments over subtidal carbonate and evaporite deposits. Dissimilarities in cycle composition between sub-basins imply the development of contrasting brine chemistries from differing recharge rates with the open ocean. What the Windsor Group shows is that evaporite type is ostensibly linked to the amplitude and frequency of sea level rise and fall during deposition. True saline giants, like the basinwide evaporites of Sequence 1, apparently require low amplitude, long frequency changes in sea level to promote the development of stable brine pools that are only periodically recharged with seawater. By contrast, the high amplitude, short frequency glacioeustatic variability in sea level that controlled the accumulation of peritidal evaporites in Subzone B produce smaller, subeconomic deposits with more complex facies relationships.

Climate change and temperature-linked hatchling mortality at a globally important sea turtle nesting site.

PubMed

Laloë, Jacques-Olivier; Cozens, Jacquie; Renom, Berta; Taxonera, Albert; Hays, Graeme C

2017-11-01

The study of temperature-dependent sex determination (TSD) in vertebrates has attracted major scientific interest. Recently, concerns for species with TSD in a warming world have increased because imbalanced sex ratios could potentially threaten population viability. In contrast, relatively little attention has been given to the direct effects of increased temperatures on successful embryonic development. Using 6603 days of sand temperature data recorded across 6 years at a globally important loggerhead sea turtle rookery-the Cape Verde Islands-we show the effects of warming incubation temperatures on the survival of hatchlings in nests. Incorporating published data (n = 110 data points for three species across 12 sites globally), we show the generality of relationships between hatchling mortality and incubation temperature and hence the broad applicability of our findings to sea turtles in general. We use a mechanistic approach supplemented by empirical data to consider the linked effects of warming temperatures on hatchling output and on sex ratios for these species that exhibit TSD. Our results show that higher temperatures increase the natural growth rate of the population as more females are produced. As a result, we project that numbers of nests at this globally important site will increase by approximately 30% by the year 2100. However, as incubation temperatures near lethal levels, the natural growth rate of the population decreases and the long-term survival of this turtle population is threatened. Our results highlight concerns for species with TSD in a warming world and underline the need for research to extend from a focus on temperature-dependent sex determination to a focus on temperature-linked hatchling mortalities. © 2017 John Wiley & Sons Ltd.

Highly variable Pliocene sea surface conditions in the Norwegian Sea

NASA Astrophysics Data System (ADS)

Bachem, Paul E.; Risebrobakken, Bjørg; De Schepper, Stijn; McClymont, Erin L.

2017-09-01

The Pliocene was a time of global warmth with small sporadic glaciations, which transitioned towards the larger-scale Pleistocene glacial-interglacial variability. Here, we present high-resolution records of sea surface temperature (SST) and ice-rafted debris (IRD) in the Norwegian Sea from 5.32 to 3.14 Ma, providing evidence that the Pliocene surface conditions of the Norwegian Sea underwent a series of transitions in response to orbital forcing and gateway changes. Average SSTs are 2 °C above the regional Holocene mean, with notable variability on millennial to orbital timescales. Both gradual changes and threshold effects are proposed for the progression of regional climate towards the Late Pliocene intensification of Northern Hemisphere glaciation. Cooling from 4.5 to 4.3 Ma may be linked to the onset of poleward flow through the Bering Strait. This cooling was further intensified by a period of cool summers due to weak obliquity forcing. A 7 °C warming of the Norwegian Sea at 4.0 Ma suggests a major increase in northward heat transport from the North Atlantic, leading to an enhanced zonal SST gradient in the Nordic Seas, which may be linked to the expansion of sea ice in the Arctic and Nordic Seas. A warm Norwegian Sea and enhanced zonal temperature gradient between 4.0 and 3.6 Ma may have been a priming factor for increased glaciation around the Nordic Seas due to enhanced evaporation and precipitation at high northern latitudes.

Modelling the impacts of a dipole-like climatic state over the Arctic

NASA Astrophysics Data System (ADS)

Pasha Karami, Mehdi; de Vernal, Anne; Hu, Xianmin; Myers, Paul G.

2015-04-01

The Arctic dipole anomaly (ADA) features a pattern with opposite sea-level pressure anomalies over the Canadian Archipelago and the Barents Sea. Changes in the predominance of Arctic atmospheric circulation modes and the shift towards a dipole mode in the past decade played a role in the summer sea ice loss and sea ice-freshwater export from the Arctic to the North Atlantic. Reconstruction of sea ice cover variations during Holocene also suggests opposite anomalies in the Barents Sea versus either the western Arctic or the Fram Strait area similar to the ADA pattern. It is vital to study such physical processes that cause dramatic changes in the Arctic sea ice recalling the link between the ADA and the current climate change. Here we focus on the question of how a persistent ADA-like state affects the Arctic sea ice distribution and its outflow to the Atlantic Ocean. For this purpose, an eddy-permitting regional configuration of the NEMO coupled ocean/sea-ice model is used. The regional domain covers the Arctic Ocean and the Northern-Hemisphere Atlantic, with a horizontal resolution of 1/4 degree at the equator (ANHA4). For the present-day simulations, boundary conditions are obtained by taking the average over the years with a positive ADA and those with a negative ADA. In the Holocene scenario, global climate model data are used to force our regional model. To exclude the role of Bering Strait and the heat flux from the Pacific Ocean, we repeat the experiments with a closed Bering Strait since a nearly closed Bering configuration was possible for the Early Holocene. The model results are compared with the paleoclimate data from Arctic and subarctic seas.

Marine aerosol source regions to Prince of Wales Icefield, Ellesmere Island, and influence from the tropical Pacific, 1979-2001

NASA Astrophysics Data System (ADS)

Criscitiello, Alison S.; Marshall, Shawn J.; Evans, Matthew J.; Kinnard, Christophe; Norman, Ann-Lise; Sharp, Martin J.

2016-08-01

Using a coastal ice core collected from Prince of Wales (POW) Icefield on Ellesmere Island, we investigate source regions of sea ice-modulated chemical species (methanesulfonic acid (MSA) and chloride (Cl-)) to POW Icefield and the influence of large-scale atmospheric variability on the transport of these marine aerosols (1979-2001). Our key findings are (1) MSA in the POW Icefield core is derived primarily from productivity in the sea ice zone of Baffin Bay and the Labrador Sea, with influence from waters within the North Water (NOW) polynya, (2) sea ice formation processes within the NOW polynya may be a significant source of sea-salt aerosols to the POW core site, in addition to offshore open water source regions primarily in Hudson Bay, and (3) the tropical Pacific influences the source and transport of marine aerosols to POW Icefield through its remote control on regional winds and sea ice variability. Regression analyses during times of MSA deposition reveal sea level pressure (SLP) anomalies favorable for opening of the NOW polynya and subsequent oceanic dimethyl sulfide production. Regression analyses during times of Cl- deposition reveal SLP anomalies that indicate a broader oceanic region of sea-salt sources to the core site. These results are supported by Scanning Multichannel Microwave Radiometer- and Special Sensor Microwave/Imager-based sea ice reconstructions and air mass transport density analyses and suggest that the marine biogenic record may capture local polynya variability, while sea-salt transport to the site from larger offshore source regions in Baffin Bay is likely. Regression analyses show a link to tropical dynamics via an atmospheric Rossby wave.

Inhibition of peroxisome proliferator-activated receptor γ: a potential link between chronic maternal hypoxia and impaired fetal growth

PubMed Central

Julian, Colleen G.; Yang, Ivana V.; Browne, Vaughn A.; Vargas, Enrique; Rodriguez, Carmelo; Pedersen, Brent S.; Moore, Lorna G.; Schwartz, David A.

2014-01-01

Chronic exposure to hypoxia raises the risk of pregnancy disorders characterized by maternal vascular dysfunction and diminished fetal growth. In an effort to identify novel pathways for these hypoxia-related effects, we assessed gene expression profiles of peripheral blood mononuclear cells (PBMCs) obtained from 43 female, high-altitude or sea-level residents in the nonpregnant state or during pregnancy (20 or 36 wk). Hypoxia-related fetal growth restriction becomes apparent between 25 and 29 wk of gestation and continues until delivery. Our sampling strategy was designed to capture changes occurring before (20 wk) and during (36 wk) the time frame of slowed fetal growth. PBMC gene expression profiles were generated using human gene expression microarrays and compared between altitudes. Biological pathways were identified using pathway analysis. Modest transcriptional differences were observed between altitudes in the nonpregnant state. Of the genes that were differentially expressed at high altitude vs. sea level during pregnancy (20 wk: 59 probes mapped to 41 genes; 36 wk: 985 probes mapped to 700 genes), several are of pathological relevance for fetal growth restriction. In particular, transcriptional changes were consistent with the negative regulation of peroxisome proliferator-activated receptor γ (PPARγ) at high altitude; such effects were accompanied by reduced birth weight (P <0.05) and head circumference (P <0.01) at high altitude vs. sea level. Our findings indicate that chronic exposure to hypoxia during pregnancy alters maternal gene expression patterns in general and, in particular, expression of key genes involved in metabolic homeostasis that have been proposed to play a role in the pathophysiology of fetal growth restriction.—Julian, C. G., Yang, I. V., Browne, V. A., Vargas, E., Rodriguez, C., Pedersen, B. S., Moore, L. G., Schwartz, D. A. Inhibition of peroxisome proliferator-activated receptor γ: a potential link between chronic maternal hypoxia and impaired fetal growth. PMID:24307415

Indonesia: Domestic Politics, Strategic Dynamics, and American Interests

DTIC Science & Technology

2006-04-03

including some 6,000 occupied islands, which straddles the equator. Key sea lanes linking the Indian Ocean and the Southwest Pacific pass through Indonesia...percentage of world trade transits the strategically important straits of Malacca which link the Indian Ocean littoral to the South China Sea and the larger...the epicenter of the Indian Ocean earthquake. This disaster led to a massive international relief effort in which the United States played a leading

Greenland coastal air temperatures linked to Baffin Bay and Greenland Sea ice conditions during autumn through regional blocking patterns

NASA Astrophysics Data System (ADS)

Ballinger, Thomas J.; Hanna, Edward; Hall, Richard J.; Miller, Jeffrey; Ribergaard, Mads H.; Høyer, Jacob L.

2018-01-01

Variations in sea ice freeze onset and regional sea surface temperatures (SSTs) in Baffin Bay and Greenland Sea are linked to autumn surface air temperatures (SATs) around coastal Greenland through 500 hPa blocking patterns, 1979-2014. We find strong, statistically significant correlations between Baffin Bay freeze onset and SSTs and SATs across the western and southernmost coastal areas, while weaker and fewer significant correlations are found between eastern SATs, SSTs, and freeze periods observed in the neighboring Greenland Sea. Autumn Greenland Blocking Index values and the incidence of meridional circulation patterns have increased over the modern sea ice monitoring era. Increased anticyclonic blocking patterns promote poleward transport of warm air from lower latitudes and local warm air advection onshore from ocean-atmosphere sensible heat exchange through ice-free or thin ice-covered seas bordering the coastal stations. Temperature composites by years of extreme late freeze conditions, occurring since 2006 in Baffin Bay, reveal positive monthly SAT departures that often exceed 1 standard deviation from the 1981-2010 climate normal over coastal areas that exhibit a similar spatial pattern as the peak correlations.

Sea ice, rain-on-snow and tundra reindeer nomadism in Arctic Russia

PubMed Central

Kumpula, Timo; Meschtyb, Nina; Laptander, Roza; Macias-Fauria, Marc; Zetterberg, Pentti; Verdonen, Mariana; Kim, Kwang-Yul; Boisvert, Linette N.; Stroeve, Julienne C.; Bartsch, Annett

2016-01-01

Sea ice loss is accelerating in the Barents and Kara Seas (BKS). Assessing potential linkages between sea ice retreat/thinning and the region's ancient and unique social–ecological systems is a pressing task. Tundra nomadism remains a vitally important livelihood for indigenous Nenets and their large reindeer herds. Warming summer air temperatures have been linked to more frequent and sustained summer high-pressure systems over West Siberia, Russia, but not to sea ice retreat. At the same time, autumn/winter rain-on-snow (ROS) events have become more frequent and intense. Here, we review evidence for autumn atmospheric warming and precipitation increases over Arctic coastal lands in proximity to BKS ice loss. Two major ROS events during November 2006 and 2013 led to massive winter reindeer mortality episodes on the Yamal Peninsula. Fieldwork with migratory herders has revealed that the ecological and socio-economic impacts from the catastrophic 2013 event will unfold for years to come. The suggested link between sea ice loss, more frequent and intense ROS events and high reindeer mortality has serious implications for the future of tundra Nenets nomadism. PMID:27852939

Sea ice, rain-on-snow and tundra reindeer nomadism in Arctic Russia.

PubMed

Forbes, Bruce C; Kumpula, Timo; Meschtyb, Nina; Laptander, Roza; Macias-Fauria, Marc; Zetterberg, Pentti; Verdonen, Mariana; Skarin, Anna; Kim, Kwang-Yul; Boisvert, Linette N; Stroeve, Julienne C; Bartsch, Annett

2016-11-01

Sea ice loss is accelerating in the Barents and Kara Seas (BKS). Assessing potential linkages between sea ice retreat/thinning and the region's ancient and unique social-ecological systems is a pressing task. Tundra nomadism remains a vitally important livelihood for indigenous Nenets and their large reindeer herds. Warming summer air temperatures have been linked to more frequent and sustained summer high-pressure systems over West Siberia, Russia, but not to sea ice retreat. At the same time, autumn/winter rain-on-snow (ROS) events have become more frequent and intense. Here, we review evidence for autumn atmospheric warming and precipitation increases over Arctic coastal lands in proximity to BKS ice loss. Two major ROS events during November 2006 and 2013 led to massive winter reindeer mortality episodes on the Yamal Peninsula. Fieldwork with migratory herders has revealed that the ecological and socio-economic impacts from the catastrophic 2013 event will unfold for years to come. The suggested link between sea ice loss, more frequent and intense ROS events and high reindeer mortality has serious implications for the future of tundra Nenets nomadism. © 2016 The Authors.

Microplastic pollution in the Greenland Sea: Background levels and selective contamination of planktivorous diving seabirds.

PubMed

Amélineau, F; Bonnet, D; Heitz, O; Mortreux, V; Harding, A M A; Karnovsky, N; Walkusz, W; Fort, J; Grémillet, D

2016-12-01

Microplastics have been reported everywhere around the globe. With very limited human activities, the Arctic is distant from major sources of microplastics. However, microplastic ingestions have been found in several Arctic marine predators, confirming their presence in this region. Nonetheless, existing information for this area remains scarce, thus there is an urgent need to quantify the contamination of Arctic marine waters. In this context, we studied microplastic abundance and composition within the zooplankton community off East Greenland. For the same area, we concurrently evaluated microplastic contamination of little auks (Alle alle), an Arctic seabird feeding on zooplankton while diving between 0 and 50 m. The study took place off East Greenland in July 2005 and 2014, under strongly contrasted sea-ice conditions. Among all samples, 97.2% of the debris found were filaments. Despite the remoteness of our study area, microplastic abundances were comparable to those of other oceans, with 0.99 ± 0.62 m -3 in the presence of sea-ice (2005), and 2.38 ± 1.11 m -3 in the nearby absence of sea-ice (2014). Microplastic rise between 2005 and 2014 might be linked to an increase in plastic production worldwide or to lower sea-ice extents in 2014, as sea-ice can represent a sink for microplastic particles, which are subsequently released to the water column upon melting. Crucially, all birds had eaten plastic filaments, and they collected high levels of microplastics compared to background levels with 9.99 and 8.99 pieces per chick meal in 2005 and 2014, respectively. Importantly, we also demonstrated that little auks took more often light colored microplastics, rather than darker ones, strongly suggesting an active contamination with birds mistaking microplastics for their natural prey. Overall, our study stresses the great vulnerability of Arctic marine species to microplastic pollution in a warming Arctic, where sea-ice melting is expected to release vast volumes of trapped debris. Copyright © 2016 Elsevier Ltd. All rights reserved.

Long-distance swimming by polar bears (Ursus maritimus) of the southern Beaufort Sea during years of extensive open water

USGS Publications Warehouse

2014-01-01

Polar bears (Ursus maritimus Phipps, 1774) depend on sea ice for catching marine mammal prey. Recent sea-ice declines have been linked to reductions in body condition, survival, and population size. Reduced foraging opportunity is hypothesized to be the primary cause of sea-ice-linked declines, but the costs of travel through a deteriorated sea-ice environment also may be a factor. We used movement data from 52 adult female polar bears wearing Global Positioning System (GPS) collars, including some with dependent young, to document long-distance swimming (>50 km) by polar bears in the southern Beaufort and Chukchi seas. During 6 years (2004-2009), we identified 50 long-distance swims by 20 bears. Swim duration and distance ranged from 0.7 to 9.7 days (mean = 3.4 days) and 53.7 to 687.1 km (mean = 154.2 km), respectively. Frequency of swimming appeared to increase over the course of the study. We show that adult female polar bears and their cubs are capable of swimming long distances during periods when extensive areas of open water are present. However, long-distance swimming appears to have higher energetic demands than moving over sea ice. Our observations suggest long-distance swimming is a behavioral response to declining summer sea-ice conditions.

The Evolution History of South China Sea: a Synthesis of Recent Geophysical, Geological, and Geochemical Results

NASA Astrophysics Data System (ADS)

Xue, M.; Li, L.; Chen, L.

2016-12-01

South China Sea (SCS) is located in the continental margin of Eurasia plate, where different geological blocks/tectonic plates interact. The dynamic mechanism of the formation of South China Sea (SCS) has been debated for decades. In this study, we first synthesize our geophysical results obtained in South China Sea, including an updated 3D velocity model from surface tomography using surrounding land stations and regional earthquakes, and shear wave splitting results obtained at surrounding land stations and OBS, using local, regional, and teleseismic earthquakes. The observed splitting results in South China Sea are complex: the fast polarization direction beneath the central basin is approximately NE-SW, nearly parallel to the extinct ridge in the central basin of SCS; however, the fast axis within the slab is trench-parallel outside the ridge subduction region. In 3D velocity models, subducting slabs are observed as dipping high velocity anomalies, and discontinuous low velocities are observed above the subduction slab, as well as in the basin. How the splitting observations are connected with the velocity models? How observations are linked to one another? How are the observations in central basin linked with surrounding region? We are aiming to link these observations themselves as well as with newly published results from geophysics, geochemistry, and geology in this region. Such a synthesis will improve our understanding about the evolution of South China Sea and facilitate new ideas.

Late Quaternary tephrostratigraphy of Baegdusan and Ulleung volcanoes using marine sediments in the Japan Sea/East Sea

NASA Astrophysics Data System (ADS)

Lim, Chungwan; Toyoda, Kazuhiro; Ikehara, Ken; Peate, David W.

2013-07-01

Only Ulleung and Baegdusan volcanoes have produced alkaline tephras in the Japan Sea/East Sea during the Quaternary. Little is known about their detailed tephrostratigraphy, except for the U-Oki and B-Tm tephras. Trace element analysis of bulk sediments can be used to identify alkaline cryptotephra because of the large compositional contrast. Five sediment cores spanning the interval between the rhyolitic AT (29.4 ka) and Aso-4 (87 ka) tephras were analyzed using an INAA scanning method. Source volcanoes for the five detected alkaline cryptotephra were identified from major element analyses of hand-picked glass shards: Ulleung (U-Ym, and the newly identified U-Sado), and Baegdusan (B-J, and the newly identified B-Sado and B-Ym). The eruption ages of the U-Ym, U-Sado, B-J, B-Sado, and B-Ym tephras are estimated to be 38 ka, 61 ka, 26 ka, 51 ka, 68-69 ka, and 86 ka, respectively, based on correlations with regional-scale TL (thinly laminated) layer stratigraphy (produced by basin-wide changes in bottom-water oxygen levels in response to millennium-scale paleoclimate variations). This study has allowed construction of an alkaline tephrostratigraphical framework for the late Quaternary linked to global environmental changes in the Japan Sea/East Sea, and improves our knowledge of the eruptive histories of Ulleung and Baegdusan volcanoes.

Long-term increases in young-of-the-year growth of Arctic cisco Coregonus autumnalis and environmental influences.

PubMed

von Biela, V R; Zimmerman, C E; Moulton, L L

2011-01-01

Arctic cisco Coregonus autumnalis young-of-year (YOY) growth was used as a proxy to examine the long-term response of a high-latitude fish population to changing climate from 1978 to 2004. YOY growth increased over time (r² = 0·29) and was correlated with monthly averages of the Arctic oscillation index, air temperature, east wind speed, sea-ice concentration and river discharge with and without time lags. Overall, the most prevalent correlates to YOY growth were sea-ice concentration lagged 1 year (significant correlations in 7 months; r² = 0·14-0·31) and Mackenzie River discharge lagged 2 years (significant correlations in 8 months; r² = 0·13-0·50). The results suggest that decreased sea-ice concentrations and increased river discharge fuel primary production and that life cycles of prey species linking increased primary production to fish growth are responsible for the time lag. Oceanographic studies also suggest that sea ice concentration and fluvial inputs from the Mackenzie River are key factors influencing productivity in the Beaufort Sea. Future research should assess the possible mechanism relating sea ice concentration and river discharge to productivity at upper trophic levels. Journal of Fish Biology © 2010 The Fisheries Society of the British Isles. No claim to original US government works.

Absolute Sea-level Changes Derived from Integrated Geodetic Datasets (1955-2016) in the Caribbean Sea

NASA Astrophysics Data System (ADS)

Yang, L.; Wang, G.; Liu, H.

2017-12-01

Rising sea level has important direct impacts on coastal and island regions such as the Caribbean where the influence of sea-level rise is becoming more apparent. The Caribbean Sea is a semi-enclosed sea adjacent to the landmasses of South and Central America to the south and west, and the Greater Antilles and the Lesser Antilles separate it from the Atlantic Ocean to the north and east. The work focus on studying the relative and absolute sea-level changes by integrating tide gauge, GPS, and satellite altimetry datasets (1955-2016) within the Caribbean Sea. Further, the two main components of absolute sea-level change, ocean mass and steric sea-level changes, are respectively studied using GRACE, temperature, and salinity datasets (1955-2016). According to the analysis conducted, the sea-level change rates have considerable temporal and spatial variations, and estimates may be subject to the techniques used and observation periods. The average absolute sea-level rise rate is 1.8±0.3 mm/year for the period from 1955 to 2015 according to the integrated tide gauge and GPS observations; the average absolute sea-level rise rate is 3.5±0.6 mm/year for the period from 1993 to 2016 according to the satellite altimetry observations. This study shows that the absolute sea-level change budget in the Caribbean Sea is closed in the periods from 1955 to 2016, in which ocean mass change dominates the absolute sea-level rise. The absolute sea-level change budget is also closed in the periods from 2004 to 2016, in which steric sea-level rise dominates the absolute sea-level rise.

Future loss of Arctic sea-ice cover could drive a substantial decrease in California's rainfall.

PubMed

Cvijanovic, Ivana; Santer, Benjamin D; Bonfils, Céline; Lucas, Donald D; Chiang, John C H; Zimmerman, Susan

2017-12-05

From 2012 to 2016, California experienced one of the worst droughts since the start of observational records. As in previous dry periods, precipitation-inducing winter storms were steered away from California by a persistent atmospheric ridging system in the North Pacific. Here we identify a new link between Arctic sea-ice loss and the North Pacific geopotential ridge development. In a two-step teleconnection, sea-ice changes lead to reorganization of tropical convection that in turn triggers an anticyclonic response over the North Pacific, resulting in significant drying over California. These findings suggest that the ability of climate models to accurately estimate future precipitation changes over California is also linked to the fidelity with which future sea-ice changes are simulated. We conclude that sea-ice loss of the magnitude expected in the next decades could substantially impact California's precipitation, thus highlighting another mechanism by which human-caused climate change could exacerbate future California droughts.

Exponential decline of deep-sea ecosystem functioning linked to benthic biodiversity loss.

PubMed

Danovaro, Roberto; Gambi, Cristina; Dell'Anno, Antonio; Corinaldesi, Cinzia; Fraschetti, Simonetta; Vanreusel, Ann; Vincx, Magda; Gooday, Andrew J

2008-01-08

Recent investigations suggest that biodiversity loss might impair the functioning and sustainability of ecosystems. Although deep-sea ecosystems are the most extensive on Earth, represent the largest reservoir of biomass, and host a large proportion of undiscovered biodiversity, the data needed to evaluate the consequences of biodiversity loss on the ocean floor are completely lacking. Here, we present a global-scale study based on 116 deep-sea sites that relates benthic biodiversity to several independent indicators of ecosystem functioning and efficiency. We show that deep-sea ecosystem functioning is exponentially related to deep-sea biodiversity and that ecosystem efficiency is also exponentially linked to functional biodiversity. These results suggest that a higher biodiversity supports higher rates of ecosystem processes and an increased efficiency with which these processes are performed. The exponential relationships presented here, being consistent across a wide range of deep-sea ecosystems, suggest that mutually positive functional interactions (ecological facilitation) can be common in the largest biome of our biosphere. Our results suggest that a biodiversity loss in deep-sea ecosystems might be associated with exponential reductions of their functions. Because the deep sea plays a key role in ecological and biogeochemical processes at a global scale, this study provides scientific evidence that the conservation of deep-sea biodiversity is a priority for a sustainable functioning of the worlds' oceans.

Techniques for integrating the animations, multimedia, and interactive features of NASA’s climate change website, Climate Change: NASA’s Eyes on the Earth, into the classroom to advance climate literacy and encourage interest in STEM disciplines

NASA Astrophysics Data System (ADS)

Tenenbaum, L. F.; Jackson, R.; Greene, M.

2009-12-01

I developed a variety of educational content for the "Climate Change: NASA’s Eyes on the Earth" website, notably an interactive feature for the "Key Indicators: Ice Mass Loss" link that includes photo pair images of glaciers around the world, changes in Arctic sea ice extent videos, Greenland glacial calving time lapse videos, and Antarctic ice shelf break up animations, plus news pieces and a Sea Level Quiz. I integrated these resources and other recent NASA and JPL climate and oceanography data and information into climate change components of Oceanography Lab exercises, Oceanography lectures and Introduction to Environmental Technology courses. I observed that using these Internet interactive features in the classroom greatly improved student participation, topic comprehension, scientific curiosity and interest in Earth and climate science across diverse student populations. Arctic Sea Ice Extent Summer 2007 Credit: NASA

Pan–ice-sheet glacier terminus change in East Antarctica reveals sensitivity of Wilkes Land to sea-ice changes

PubMed Central

Miles, Bertie W. J.; Stokes, Chris R.; Jamieson, Stewart S. R.

2016-01-01

The dynamics of ocean-terminating outlet glaciers are an important component of ice-sheet mass balance. Using satellite imagery for the past 40 years, we compile an approximately decadal record of outlet-glacier terminus position change around the entire East Antarctic Ice Sheet (EAIS) marine margin. We find that most outlet glaciers retreated during the period 1974–1990, before switching to advance in every drainage basin during the two most recent periods, 1990–2000 and 2000–2012. The only exception to this trend was in Wilkes Land, where the majority of glaciers (74%) retreated between 2000 and 2012. We hypothesize that this anomalous retreat is linked to a reduction in sea ice and associated impacts on ocean stratification, which increases the incursion of warm deep water toward glacier termini. Because Wilkes Land overlies a large marine basin, it raises the possibility of a future sea level contribution from this sector of East Antarctica. PMID:27386519

Pan-ice-sheet glacier terminus change in East Antarctica reveals sensitivity of Wilkes Land to sea-ice changes.

PubMed

Miles, Bertie W J; Stokes, Chris R; Jamieson, Stewart S R

2016-05-01

The dynamics of ocean-terminating outlet glaciers are an important component of ice-sheet mass balance. Using satellite imagery for the past 40 years, we compile an approximately decadal record of outlet-glacier terminus position change around the entire East Antarctic Ice Sheet (EAIS) marine margin. We find that most outlet glaciers retreated during the period 1974-1990, before switching to advance in every drainage basin during the two most recent periods, 1990-2000 and 2000-2012. The only exception to this trend was in Wilkes Land, where the majority of glaciers (74%) retreated between 2000 and 2012. We hypothesize that this anomalous retreat is linked to a reduction in sea ice and associated impacts on ocean stratification, which increases the incursion of warm deep water toward glacier termini. Because Wilkes Land overlies a large marine basin, it raises the possibility of a future sea level contribution from this sector of East Antarctica.

Global sea turtle conservation successes

PubMed Central

Mazaris, Antonios D.; Schofield, Gail; Gkazinou, Chrysoula; Almpanidou, Vasiliki; Hays, Graeme C.

2017-01-01

We document a tendency for published estimates of population size in sea turtles to be increasing rather than decreasing across the globe. To examine the population status of the seven species of sea turtle globally, we obtained 299 time series of annual nesting abundance with a total of 4417 annual estimates. The time series ranged in length from 6 to 47 years (mean, 16.2 years). When levels of abundance were summed within regional management units (RMUs) for each species, there were upward trends in 12 RMUs versus downward trends in 5 RMUs. This prevalence of more upward than downward trends was also evident in the individual time series, where we found 95 significant increases in abundance and 35 significant decreases. Adding to this encouraging news for sea turtle conservation, we show that even small sea turtle populations have the capacity to recover, that is, Allee effects appear unimportant. Positive trends in abundance are likely linked to the effective protection of eggs and nesting females, as well as reduced bycatch. However, conservation concerns remain, such as the decline in leatherback turtles in the Eastern and Western Pacific. Furthermore, we also show that, often, time series are too short to identify trends in abundance. Our findings highlight the importance of continued conservation and monitoring efforts that underpin this global conservation success story. PMID:28948215

Reply to Comment on ``Emergence of Complex Societies After Sea Level Stabilized''

NASA Astrophysics Data System (ADS)

Day, John W.; Gunn, Joel D.; Folan, William J.; Yáñez-Arancibia, Alejandro; Horton, Benjamin P.

2007-10-01

Washington [this issue] raised a number of interesting points that serve to clarify the origins of civilizations on continental margins. We linked the initial development of civilizations to coastal margin productivity [Day et al., 2007]. Washington argues that a number of early civilizations were not related to marine productivity, but rather were centered around the exploitation and cultivation of riparian grains. However, we defined coastal margins to include upwellings, estuaries, and lower floodplains affected by coastal water levels. Thus, the Nile, Mesopotamia, Indus, Mississippi, and Yellow societies were influenced by coastal margin productivity.

Bridging groundwater models and decision support with a Bayesian network

USGS Publications Warehouse

Fienen, Michael N.; Masterson, John P.; Plant, Nathaniel G.; Gutierrez, Benjamin T.; Thieler, E. Robert

2013-01-01

Resource managers need to make decisions to plan for future environmental conditions, particularly sea level rise, in the face of substantial uncertainty. Many interacting processes factor in to the decisions they face. Advances in process models and the quantification of uncertainty have made models a valuable tool for this purpose. Long-simulation runtimes and, often, numerical instability make linking process models impractical in many cases. A method for emulating the important connections between model input and forecasts, while propagating uncertainty, has the potential to provide a bridge between complicated numerical process models and the efficiency and stability needed for decision making. We explore this using a Bayesian network (BN) to emulate a groundwater flow model. We expand on previous approaches to validating a BN by calculating forecasting skill using cross validation of a groundwater model of Assateague Island in Virginia and Maryland, USA. This BN emulation was shown to capture the important groundwater-flow characteristics and uncertainty of the groundwater system because of its connection to island morphology and sea level. Forecast power metrics associated with the validation of multiple alternative BN designs guided the selection of an optimal level of BN complexity. Assateague island is an ideal test case for exploring a forecasting tool based on current conditions because the unique hydrogeomorphological variability of the island includes a range of settings indicative of past, current, and future conditions. The resulting BN is a valuable tool for exploring the response of groundwater conditions to sea level rise in decision support.

Size, diet, and condition of age-0 Pacific cod (Gadus macrocephalus) during warm and cool climate states in the eastern Bering sea

NASA Astrophysics Data System (ADS)

Farley, Edward V.; Heintz, Ron A.; Andrews, Alex G.; Hurst, Thomas P.

2016-12-01

The revised Oscillating Control Hypothesis for the Bering Sea suggests that recruitment of groundfish is linked to climatic processes affecting seasonal sea ice that, in turn, drives the quality and quantity of prey available to young fish for growth and energy storage during their critical life history stages. We test this notion for age-0 (juvenile) Pacific cod (Gadus macrocephalus) by examining the variability in size, diet, and energetic condition during warm (2003-2005), average (2006), and cool (2007-2011) climate states in the eastern Bering Sea. Juvenile cod stomachs contained high proportions of age-0 walleye pollock (by wet weight) during years with warm sea temperatures with a shift to euphausiids and large copepods during years with cool sea temperatures. Juvenile cod were largest during years with warm sea temperatures and smallest during years with cool sea temperatures. However, energetic status (condition) of juvenile cod was highest during years with cool sea temperatures. This result is likely linked to the shift to high quality, lipid-rich prey found in greater abundance on the shelf and in the stomach contents of juvenile cod during cool years. Our examination of juvenile cod size, diet, and energetic status provided results that are similar to those from studies on juvenile pollock, suggesting that the common mechanisms regulating gadid recruitment on the eastern Bering Sea shelf are climate state, prey quality and quantity, and caloric density of gadids prior to winter.

Evidence for a novel marine harmful algal bloom: Cyanotoxin (Microcystin) transfer from land to sea otters

USGS Publications Warehouse

Miller, Melissa A.; Kudela, Raphael M.; Mekebri, Abdu; Crane, Dave; Oates, Stori C.; Tinker, M. Timothy; Staedler, Michelle; Miller, Woutrina A.; Toy-Choutka, Sharon; Dominik, Clare; Hardin, Dane; Langlois, Gregg; Murray, Michael; Ward, Kim; Jessup, David A.

2010-01-01

"Super-blooms" of cyanobacteria that produce potent and environmentally persistent biotoxins (microcystins) are an emerging global health issue in freshwater habitats. Monitoring of the marine environment for secondary impacts has been minimal, although microcystin-contaminated freshwater is known to be entering marine ecosystems. Here we confirm deaths of marine mammals from microcystin intoxication and provide evidence implicating land-sea flow with trophic transfer through marine invertebrates as the most likely route of exposure. This hypothesis was evaluated through environmental detection of potential freshwater and marine microcystin sources, sea otter necropsy with biochemical analysis of tissues and evaluation of bioaccumulation of freshwater microcystins by marine invertebrates. Ocean discharge of freshwater microcystins was confirmed for three nutrient-impaired rivers flowing into the Monterey Bay National Marine Sanctuary, and microcystin concentrations up to 2,900 ppm (2.9 million ppb) were detected in a freshwater lake and downstream tributaries to within 1 km of the ocean. Deaths of 21 southern sea otters, a federally listed threatened species, were linked to microcystin intoxication. Finally, farmed and free-living marine clams, mussels and oysters of species that are often consumed by sea otters and humans exhibited significant biomagnification (to 107 times ambient water levels) and slow depuration of freshwater cyanotoxins, suggesting a potentially serious environmental and public health threat that extends from the lowest trophic levels of nutrient-impaired freshwater habitat to apex marine predators. Microcystin-poisoned sea otters were commonly recovered near river mouths and harbors and contaminated marine bivalves were implicated as the most likely source of this potent hepatotoxin for wild otters. This is the first report of deaths of marine mammals due to cyanotoxins and confirms the existence of a novel class of marine "harmful algal bloom" in the Pacific coastal environment; that of hepatotoxic shellfish poisoning (HSP), suggesting that animals and humans are at risk from microcystin poisoning when consuming shellfish harvested at the land-sea interface.

Evidence for a Novel Marine Harmful Algal Bloom: Cyanotoxin (Microcystin) Transfer from Land to Sea Otters

PubMed Central

Miller, Melissa A.; Kudela, Raphael M.; Mekebri, Abdu; Crane, Dave; Oates, Stori C.; Tinker, M. Timothy; Staedler, Michelle; Miller, Woutrina A.; Toy-Choutka, Sharon; Dominik, Clare; Hardin, Dane; Langlois, Gregg; Murray, Michael; Ward, Kim; Jessup, David A.

2010-01-01

“Super-blooms” of cyanobacteria that produce potent and environmentally persistent biotoxins (microcystins) are an emerging global health issue in freshwater habitats. Monitoring of the marine environment for secondary impacts has been minimal, although microcystin-contaminated freshwater is known to be entering marine ecosystems. Here we confirm deaths of marine mammals from microcystin intoxication and provide evidence implicating land-sea flow with trophic transfer through marine invertebrates as the most likely route of exposure. This hypothesis was evaluated through environmental detection of potential freshwater and marine microcystin sources, sea otter necropsy with biochemical analysis of tissues and evaluation of bioaccumulation of freshwater microcystins by marine invertebrates. Ocean discharge of freshwater microcystins was confirmed for three nutrient-impaired rivers flowing into the Monterey Bay National Marine Sanctuary, and microcystin concentrations up to 2,900 ppm (2.9 million ppb) were detected in a freshwater lake and downstream tributaries to within 1 km of the ocean. Deaths of 21 southern sea otters, a federally listed threatened species, were linked to microcystin intoxication. Finally, farmed and free-living marine clams, mussels and oysters of species that are often consumed by sea otters and humans exhibited significant biomagnification (to 107 times ambient water levels) and slow depuration of freshwater cyanotoxins, suggesting a potentially serious environmental and public health threat that extends from the lowest trophic levels of nutrient-impaired freshwater habitat to apex marine predators. Microcystin-poisoned sea otters were commonly recovered near river mouths and harbors and contaminated marine bivalves were implicated as the most likely source of this potent hepatotoxin for wild otters. This is the first report of deaths of marine mammals due to cyanotoxins and confirms the existence of a novel class of marine “harmful algal bloom” in the Pacific coastal environment; that of hepatotoxic shellfish poisoning (HSP), suggesting that animals and humans are at risk from microcystin poisoning when consuming shellfish harvested at the land-sea interface. PMID:20844747

Vertebrate community on an ice-age Caribbean island

PubMed Central

Steadman, David W.; Albury, Nancy A.; Kakuk, Brian; Mead, Jim I.; Soto-Centeno, J. Angel; Singleton, Hayley M.; Franklin, Janet

2015-01-01

We report 95 vertebrate taxa (13 fishes, 11 reptiles, 63 birds, 8 mammals) from late Pleistocene bone deposits in Sawmill Sink, Abaco, The Bahamas. The >5,000 fossils were recovered by scuba divers on ledges at depths of 27–35 m below sea level. Of the 95 species, 39 (41%) no longer occur on Abaco (4 reptiles, 31 birds, 4 mammals). We estimate that 17 of the 39 losses (all of them birds) are linked to changes during the Pleistocene–Holocene Transition (PHT) (∼15–9 ka) in climate (becoming more warm and moist), habitat (expansion of broadleaf forest at the expense of pine woodland), sea level (rising from −80 m to nearly modern levels), and island area (receding from ∼17,000 km2 to 1,214 km2). The remaining 22 losses likely are related to the presence of humans on Abaco for the past 1,000 y. Thus, the late Holocene arrival of people probably depleted more populations than the dramatic physical and biological changes associated with the PHT. PMID:26483484

Destabilisation of an Arctic ice cap triggered by a hydro-thermodynamic feedback to summer-melt

NASA Astrophysics Data System (ADS)

Dunse, T.; Schellenberger, T.; Kääb, A.; Hagen, J. O.; Schuler, T. V.; Reijmer, C. H.

2014-05-01

Mass loss from glaciers and ice sheets currently accounts for two-thirds of the observed global sea-level rise and has accelerated since the 1990s, coincident with strong atmospheric warming in the Polar Regions. Here we present continuous GPS measurements and satellite synthetic aperture radar based velocity maps from the Austfonna ice cap, Svalbard, that demonstrate strong links between surface-melt and multiannual ice-flow acceleration. We identify a hydro-thermodynamic feedback that successively mobilizes stagnant ice regions, initially frozen to their bed, thereby facilitating fast basal motion over an expanding area. By autumn 2012, successive destabilization of the marine terminus escalated in a surge of the ice cap's largest drainage basin, Basin-3. The resulting iceberg discharge of 4.2 ± 1.6 Gt a-1 over the period April 2012 to May 2013 triples the calving loss from the entire ice cap. After accounting for the terminus advance, the related sea-level rise contribution of 7.2 ± 2.6 Gt a-1 matches the recent annual ice-mass loss from the entire Svalbard archipelago. Our study highlights the importance of dynamic glacier wastage and illuminates mechanisms that may trigger a sustained increase in dynamic glacier wastage or the disintegration of ice-sheets in response to climate warming, which is acknowledged but not quantified in global projections of sea-level rise.

Correlation of sea level falls interpreted from atoll stratigraphy with turbidites in adjacent basins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lincoln, J.M.

Past sea levels can be derived from any atoll subsurface sediments deposited at or near sea level by determining the ages of deposition and correcting the present depths to the sediments for subsidence of the underlying edifice since the times of deposition. A sea level curve constructed by this method consists of discontinuous segments, each corresponding to a period of rising relative sea level and deposition of a discrete sedimentary package. Discontinuities in the sea level curve derived by this method correspond to relative sea level falls and stratigraphic hiatuses in the atoll subsurface. During intervals of relative sea levelmore » fall an atoll emerges to become a high limestone island. Sea level may fluctuate several times during a period of atoll emergence to become a high limestone island. Sea level may fluctuate several times during a period of atoll emergence without depositing sediments on top of the atoll. Furthermore, subaerial erosion may remove a substantial part of the depositional record of previous sea level fluctuations. For these reasons the authors must look to the adjacent basins to complement the incomplete record of sea level change recorded beneath atolls. During lowstands of sea level, faunas originally deposited near sea level on an atoll may be eroded and redeposited as turbidites in deep adjacent basins. Three such turbidites penetrated during deep-sea drilling at Sites 462 and 315 in the central Pacific correlate well with a late Tertiary sea level curve based on biostratigraphic ages and {sup 87}Sr/{sup 86}Sr chronostratigraphy for core from Enewetak Atoll in the northern Marshall Islands. Further drilling of the archipelagic aprons adjacent to atolls will improve the sea level history that may be inferred from atoll stratigraphy.« less

Effect of tidal overwash on the embryonic development of leatherback turtles in French Guiana.

PubMed

Caut, Stéphane; Guirlet, Elodie; Girondot, Marc

2010-05-01

In marine turtles, the physical conditions experienced by eggs during incubation affect embryonic development. In the leatherback, hatching success is known to be low in relation to other marine turtles as a result of high embryonic mortality. Moreover, the hatching success on Yalimapo in French Guiana, one major nesting beach for this species, is lower compared to other nesting sites. We assessed the rate of leatherback turtle embryonic mortality in order to investigate the tolerance of leatherback turtle clutches laid on Yalimapo beach to tidal overwash, and we highlight causes of poor hatching success. Of the 89 nests studied, 27 were overlapped by tide at least once during the incubation period (of which five nests were lost by erosion). The hatching success was on average significantly lower in overwashed nests than in non-overwashed, highlighting the existence of embryonic developmental arrest linked to tidal inundation. The stages of developmental arrest and their proportion are linked with time, frequency and level of overwash events. In the context of global warming and associated sea-level rise, understanding the detrimental effect of tidal inundation on the development of marine turtle nests is of interest in nesting sites where turtles are likely to be forced to nest closer to the tide line, thus exposing their nests to greater risk of nest overlap with sea and tidal inundation. Copyright 2009 Elsevier Ltd. All rights reserved.

Reef-scale modeling of coral calcification responses to ocean acidification and sea-level rise

NASA Astrophysics Data System (ADS)

Nakamura, Takashi; Nadaoka, Kazuo; Watanabe, Atsushi; Yamamoto, Takahiro; Miyajima, Toshihiro; Blanco, Ariel C.

2018-03-01

To predict coral responses to future environmental changes at the reef scale, the coral polyp model (Nakamura et al. in Coral Reefs 32:779-794, 2013), which reconstructs coral responses to ocean acidification, flow conditions and other factors, was incorporated into a reef-scale three-dimensional hydrodynamic-biogeochemical model. This coupled reef-scale model was compared to observations from the Shiraho fringing reef, Ishigaki Island, Japan, where the model accurately reconstructed spatiotemporal variation in reef hydrodynamic and geochemical parameters. The simulated coral calcification rate exhibited high spatial variation, with lower calcification rates in the nearshore and stagnant water areas due to isolation of the inner reef at low tide, and higher rates on the offshore side of the inner reef flat. When water is stagnant, bottom shear stress is low at night and thus oxygen diffusion rate from ambient water to the inside of the coral polyp limits respiration rate. Thus, calcification decreases because of the link between respiration and calcification. A scenario analysis was conducted using the reef-scale model with several pCO2 and sea-level conditions based on IPCC (Climate change 2013: the physical science basis. Contribution of working group I to the fifth assessment report of the intergovernmental panel on climate change, Cambridge University Press, Cambridge, 2013) scenarios. The simulation indicated that the coral calcification rate decreases with increasing pCO2. On the other hand, sea-level rise increases the calcification rate, particularly in the nearshore and the areas where water is stagnant at low tide under present conditions, as mass exchange, especially oxygen exchange at night, is enhanced between the corals and their ambient seawater due to the reduced stagnant period. When both pCO2 increase and sea-level rise occur concurrently, the calcification rate generally decreases due to the effects of ocean acidification. However, the calcification rate in some inner-reef areas will increase because the positive effects of sea-level rise offset the negative effects of ocean acidification, and total calcification rate will be positive only under the best-case scenario (RCP 2.6).

Oxygen, ecology, and the Cambrian radiation of animals

NASA Astrophysics Data System (ADS)

Sperling, Erik A.; Frieder, Christina A.; Raman, Akkur V.; Girguis, Peter R.; Levin, Lisa A.; Knoll, Andrew H.

2013-08-01

The Proterozoic-Cambrian transition records the appearance of essentially all animal body plans (phyla), yet to date no single hypothesis adequately explains both the timing of the event and the evident increase in diversity and disparity. Ecological triggers focused on escalatory predator-prey "arms races" can explain the evolutionary pattern but not its timing, whereas environmental triggers, particularly ocean/atmosphere oxygenation, do the reverse. Using modern oxygen minimum zones as an analog for Proterozoic oceans, we explore the effect of low oxygen levels on the feeding ecology of polychaetes, the dominant macrofaunal animals in deep-sea sediments. Here we show that low oxygen is clearly linked to low proportions of carnivores in a community and low diversity of carnivorous taxa, whereas higher oxygen levels support more complex food webs. The recognition of a physiological control on carnivory therefore links environmental triggers and ecological drivers, providing an integrated explanation for both the pattern and timing of Cambrian animal radiation.

Natural and anthropogenic influences on depositional architecture of the Ural Delta, Kazakhstan, northern Caspian Sea, during the past 70 years

NASA Astrophysics Data System (ADS)

Scarelli, Frederico M.; Cantelli, Luigi; Barboza, Eduardo G.; Gabbianelli, Giovanni

2017-05-01

This paper focuses on the Ural Delta in the northern zone of the Caspian Sea, an area with particular characteristics, where intense influence from anthropogenic and natural factors exists, which acts on the fragile delta system. We built a database to integrate the data from the published sources, bathymetric survey, and recent images in the geographical information system (GIS) environment. The results were linked to the Caspian Sea level (CSL) curve, which had many variations, changing the Ural Delta system's dynamics and in its architecture. In addition, the anthropogenic changes contribute to shaping the actual Ural Delta architecture. Through the link between the results and CSL, we reconstructed an evolution model for the Ural Delta system for the last century and identified three different architectures for the Ural Delta, determined by the energy that acted on the system in the last century and by the anthropogenic changes. This work identifies six different delta phases, which are shaped by CSL changes during the last 70 years and by anthropogenic changes. The delta phases recognized are: i) a Lobate Delta phase, shaped during high CSL before 1935; ii) Natural Elongate Delta 1935-1950 formed during rapid CSL fall; iii) Anthropogenic Elongate Delta 1950-1966, formed during rapid CSL fall and after the Ural-Caspian Sea canal construction, which modified the sedimentary deposition on the delta; iv) Anthropogenic Elongate Delta 1966-1982 shaped during low CSL phase; v) Anthropogenic Elongate Delta 1982-1996 formed during a rapid CSL rise phase; and vi) Anthropogenic Elongate Delta 1996-2009 shaped during high CSL that represent the last phase and actual Ural Delta architecture.

Sink or link? The bacterial role in benthic carbon cycling in the Arabian Sea's oxygen minimum zone

NASA Astrophysics Data System (ADS)

Pozzato, L.; Van Oevelen, D.; Moodley, L.; Soetaert, K.; Middelburg, J. J.

2013-11-01

The bacterial loop, the consumption of dissolved organic matter (DOM) by bacteria and subsequent transfer of bacterial carbon to higher trophic levels, plays a prominent role in pelagic food webs. However, its role in sedimentary ecosystems is not well documented. Here we present the results of isotope tracer experiments performed under in situ oxygen conditions in sediments from inside and outside the Arabian Sea's oxygen minimum zone (OMZ) to study the importance of the microbial loop in this setting. Particulate organic matter, added as phytodetritus, was processed by bacteria, protozoa and metazoans, while dissolved organic matter was processed only by bacteria and there was very little, if any, transfer to higher trophic levels within the 7 day experimental period. This lack of significant transfer of bacterial-derived carbon to metazoan consumers indicates that the bacterial loop is rather inefficient, in sediments both inside and outside the OMZ. Moreover, metazoans directly consumed labile particulate organic matter resources and thus competed with bacteria for phytodetritus.

Sink or link? The bacterial role in benthic carbon cycling in the Arabian sea oxygen minimum zone

NASA Astrophysics Data System (ADS)

Pozzato, L.; Van Oevelen, D.; Moodley, L.; Soetaert, K.; Middelburg, J. J.

2013-06-01

The bacterial loop, the consumption of dissolved organic matter (DOM) by bacteria and subsequent transfer of bacterial carbon to higher trophic levels, plays a prominent role in pelagic aquatic food webs. However, its role in sedimentary ecosystems is not well documented. Here we present the results of isotope tracer experiments performed under in situ oxygen conditions in sediments from inside and outside the Arabian Sea Oxygen Minimum Zone (OMZ) to study the importance of the microbial loop in this setting. Particulate organic matter, added as phytodetritus, was processed by bacteria, protozoa and metazoans, while dissolved organic matter was processed only by bacteria and there was very little, if any, transfer to higher trophic levels within the experimental period. This lack of significant transfer of bacterial-derived carbon to metazoan consumers indicates that the bacterial loop is rather inefficient in these sediments. Moreover, metazoans directly consume labile particulate organic matter resources and thus compete with bacteria for phytodetritus.

Antarctic sea ice control on ocean circulation in present and glacial climates

PubMed Central

Ferrari, Raffaele; Jansen, Malte F.; Adkins, Jess F.; Burke, Andrea; Stewart, Andrew L.; Thompson, Andrew F.

2014-01-01

In the modern climate, the ocean below 2 km is mainly filled by waters sinking into the abyss around Antarctica and in the North Atlantic. Paleoproxies indicate that waters of North Atlantic origin were instead absent below 2 km at the Last Glacial Maximum, resulting in an expansion of the volume occupied by Antarctic origin waters. In this study we show that this rearrangement of deep water masses is dynamically linked to the expansion of summer sea ice around Antarctica. A simple theory further suggests that these deep waters only came to the surface under sea ice, which insulated them from atmospheric forcing, and were weakly mixed with overlying waters, thus being able to store carbon for long times. This unappreciated link between the expansion of sea ice and the appearance of a voluminous and insulated water mass may help quantify the ocean’s role in regulating atmospheric carbon dioxide on glacial–interglacial timescales. Previous studies pointed to many independent changes in ocean physics to account for the observed swings in atmospheric carbon dioxide. Here it is shown that many of these changes are dynamically linked and therefore must co-occur. PMID:24889624

Antarctic sea ice control on ocean circulation in present and glacial climates.

PubMed

Ferrari, Raffaele; Jansen, Malte F; Adkins, Jess F; Burke, Andrea; Stewart, Andrew L; Thompson, Andrew F

2014-06-17

In the modern climate, the ocean below 2 km is mainly filled by waters sinking into the abyss around Antarctica and in the North Atlantic. Paleoproxies indicate that waters of North Atlantic origin were instead absent below 2 km at the Last Glacial Maximum, resulting in an expansion of the volume occupied by Antarctic origin waters. In this study we show that this rearrangement of deep water masses is dynamically linked to the expansion of summer sea ice around Antarctica. A simple theory further suggests that these deep waters only came to the surface under sea ice, which insulated them from atmospheric forcing, and were weakly mixed with overlying waters, thus being able to store carbon for long times. This unappreciated link between the expansion of sea ice and the appearance of a voluminous and insulated water mass may help quantify the ocean's role in regulating atmospheric carbon dioxide on glacial-interglacial timescales. Previous studies pointed to many independent changes in ocean physics to account for the observed swings in atmospheric carbon dioxide. Here it is shown that many of these changes are dynamically linked and therefore must co-occur.

North Atlantic variability and its links to European climate over the last 3000 years.

PubMed

Moffa-Sánchez, Paola; Hall, Ian R

2017-11-23

The subpolar North Atlantic is a key location for the Earth's climate system. In the Labrador Sea, intense winter air-sea heat exchange drives the formation of deep waters and the surface circulation of warm waters around the subpolar gyre. This process therefore has the ability to modulate the oceanic northward heat transport. Recent studies reveal decadal variability in the formation of Labrador Sea Water. Yet, crucially, its longer-term history and links with European climate remain limited. Here we present new decadally resolved marine proxy reconstructions, which suggest weakened Labrador Sea Water formation and gyre strength with similar timing to the centennial cold periods recorded in terrestrial climate archives and historical records over the last 3000 years. These new data support that subpolar North Atlantic circulation changes, likely forced by increased southward flow of Arctic waters, contributed to modulating the climate of Europe with important societal impacts as revealed in European history.

Antarctic Climate Variability: Covariance of Ozone and Sea Ice in Atmosphere - Ocean Coupled Model Simulations

NASA Astrophysics Data System (ADS)

Jrrar, Amna; Abraham, N. Luke; Pyle, John A.; Holland, David

2014-05-01

Changes in sea ice significantly modulate climate change because of its high reflective and insulating nature. While Arctic Sea Ice Extent (SIE) shows a negative trend. Antarctic SIE shows a weak but positive trend, estimated at 0.127 x 106 km2 per decade. The trend results from large regional cancellations, more ice in the Weddell and the Ross seas, and less ice in the Amundsen - Bellingshausen seas. A number of studies had demonstrated that stratospheric ozone depletion has had a major impact on the atmospheric circulation, causing a positive trend in the Southern Annular Mode (SAM), which has been linked to the observed positive trend in autumn sea ice in the Ross Sea. However, other modelling studies show that models forced with prescribed ozone hole simulate decreased sea ice in all regions comparative to a control run. A recent study has also shown that stratospheric ozone recovery will mitigate Antarctic sea ice loss. To verify this assumed relationship, it is important first to investigate the covariance between ozone's natural (dynamical) variability and Antarctic sea ice distribution in pre-industrial climate, to estimate the trend due to natural variability. We investigate the relationship between anomalous Antarctic ozone years and the subsequent changes in Antarctic sea ice distribution in a multidecadal control simulation using the AO-UMUKCA model. The model has a horizontal resolution of 3.75 X 2.5 degrees in longitude and latitude; and 60 hybrid height levels in the vertical, from the surface up to a height of 84 km. The ocean component is the NEMO ocean model on the ORCA2 tripolar grid, and the sea ice model is CICE. We evaluate the model's performance in terms of sea ice distribution, and we calculate sea ice extent trends for composites of anomalously low versus anomalously high SH polar ozone column. We apply EOF analysis to the seasonal anomalies of sea ice concentration, MSLP, and Z 500, and identify the leading climate modes controlling the variability of Antarctic sea ice in each case, and study their relationship with SH polar ozone column.

Prolonged effect of the stratospheric pathway in linking Barents-Kara Sea sea ice variability to the midlatitude circulation in a simplified model

NASA Astrophysics Data System (ADS)

Zhang, Pengfei; Wu, Yutian; Smith, Karen L.

2018-01-01

To better understand the dynamical mechanism that accounts for the observed lead-lag correlation between the early winter Barents-Kara Sea (BKS) sea ice variability and the later winter midlatitude circulation response, a series of experiments are conducted using a simplified atmospheric general circulation model with a prescribed idealized near-surface heating over the BKS. A prolonged effect is found in the idealized experiments following the near-surface heating and can be explicitly attributed to the stratospheric pathway and the long time scale in the stratosphere. The analysis of the Eliassen-Palm flux shows that, as a result of the imposed heating and linear constructive interference, anomalous upward propagating planetary-scale waves are excited and weaken the stratospheric polar vortex. This stratospheric response persists for approximately 1-2 months accompanied by downward migration to the troposphere and the surface. This downward migration largely amplifies and extends the low-level jet deceleration in the midlatitudes and cold air advection over central Asia. The idealized model experiments also suggest that the BKS region is the most effective in affecting the midlatitude circulation than other regions over the Arctic.

Multiscale Geoarchaeological Approaches from the Laurentine Shore, Castelporziano, Lazio, Italy

NASA Astrophysics Data System (ADS)

Bicket, A. R.; Rendell, H. M.; Claridge, A.; Rose, P.; Brown, F. S. J.

2009-04-01

The relationship between the meso-scale record of human activity during the Roman period and the larger-scale coastal development of the Tiber Delta (ca. 20 ka) is investigated using the archaeological and sedimentary record from a large aquaculture pond and its wider meso- to macro-scale geomorphological setting. The position of the pond is adjacent to the Roman period shoreline, known as the Laurentine Shore on the southern, distal flank of the Tiber delta, Lazio Italy, within what is now the Castelporziano Estate. The pond is thought to have been constructed in the wet dune slack behind the active coastal foredune. Magnetometer survey and excavation of the archaeological structures around this pond have shown them to be substantial features ca. 80m in length with high-status Imperial Roman architecture and with evidence for water management. Sedimentological analysis of sediment cores from within the ponds are supplemented with diatom analysis to assess the period of pre-construction, use and abandonment of this aquaculture pond. Diatom analysis suggests a relatively short period of use and it is argued that abandonment of the aquaculture structures may be linked to both alkali groundwater conditions and the dynamism of the coastal zone preventing effective management. Optical luminescence dating of the archaeological sediments and the post-abandonment dunes that bury part of the site suggest that the aquaculture pond was abandoned ca. 100 years prior to final abandonment of the Roman settlement. This case-study also highlights the implications for meso-scale investigations of human/environment relationships utilising relatively low-sensitivity sedimentary records without high-resolution proxy records. D-GPS survey in conjunction with a high-quality DEM has permitted important archaeological remains to be understood relative to sea level; a key variable for examining the formation and development of the dune ridge record. These surveys have also permitted the effective mapping of dune ridges, from aerial photography, under the extremely dense vegetation that hinders easy access across much of the site. The D-GPS georeferenced DEM has been linked to the diatom analysis of a cored salt marsh to peat sediment transition providing valuable biostratigraphic information for deriving an accurate measurement of the Roman period sea level (Lambeck et al., 2004a). This measurement is in line with published literature from nearby coastal sites, ca. - 1.3m RSL (Lambeck et al., 2004b). Understanding the sites geomorphological development in the context of eustatic sea level is a key consideration for issues of sand supply driving dune formation, linked ultimately to the development of the Tiber Delta since the Last Glacial Maximum and throughout the Holocene. On this larger spatial scale, the archaeological sites described within the Laurentine Shore, built upon the Roman period coastline, are now preserved several hundred metres inland of the contemporary shoreline. The development of the shoreline can now be investigated within the macro-scale progradation of the Tiber delta relative to eustatic sea level rise. Archaeological excavations since the 1980's have provided a rich record of high status villas, and also the supporting infrastructure of a village settlement (vicus), roads, aqueduct and the large aquaculture ponds. The dominant geomorphological features on the site are preserved coastal dune ridges. Sampling was undertaken along an alongshore transect and three inland transects. This sampling regime focuses upon the contemporary deposition of sands on the beach and the phases of dune formation, preservation and alteration recorded by the relict dune crests in relation to the archaeological record. A campaign of optical dating of the relict dune crests has provided a Late Pleistocene and Holocene record of sandsheet and dune formation linked to delta progradation that permits the larger spatial- and temporal-scale context of the archaeological record to be discussed. Sedimentary petrology techniques allow the provenance and transportation dynamics of both the sand-sized and dust-sized sediments to be assessed. Furthermore this approach also enables an investigation of carbonate and iron oxide diagenetic cements, which are an important product of the long-term in situ weathering of the dune ridges' mineralogical assemblages, but is also a feature of short-term weathering of archaeological contexts. This work has implications for locations of interest to geoarchaeological surveys. There are also important implications for the mineralogy, provenance and preservation of luminescent minerals; and some form mineralogical/provenance analysis is recommended for all optical dating studies as a result. In summary, the geoarchaeological approach undertaken at Castelporziano allows the meso-scale human/environment interactions to be considered within the broader temporal scales of the late Quaternary. It also permits consideration within the macro-spatial scales of the Tiber Delta's development during the last 15-20ka within the context of eustatic sea level rise. REFERENCES LAMBECK, K., ANTONIOLI, F., PURCELL, A. & SILENZI, S. (2004a) Sea-level change along the Italian coast for the past 10,000 yr. Quaternary Science Reviews, 23, 1567-1598. LAMBECK, K., ANZIDEI, M., ANTONIOLI, F., BENINI, A. & ESPOSITO, A. (2004b) Sea level in Roman time in the Central Mediterranean and implications for recent change. Earth and Planetary Science Letters, 224, 563-575.

Sea-level Fingerprinting, Vertical Crustal Motion from GIA, and Projections of Relative Sea-level Change in the Canadian Arctic

NASA Astrophysics Data System (ADS)

James, Thomas; Simon, Karen; Forbes, Donald; Dyke, Arthur; Mazzotti, Stephane

2010-05-01

We present projections of relative sea-level rise in the 21st century for communities in the Canadian Arctic. First, for selected communities, we determine the sea-level fingerprinting response from Antarctica, Greenland, and mountain glaciers and ice caps. Then, for various published projections of global sea-level change in the 21st century, we determine the local amount of "absolute" sea-level change. We next determine the vertical land motion arising from glacial isostatic adjustment (GIA) and incorporate this into the estimates of absolute sea-level change to obtain projections of relative sea-level change. The sea-level fingerprinting effect is especially important in the Canadian Arctic owing to proximity to Arctic ice caps and especially to the Greenland ice sheet. Its effect is to reduce the range of projected relative sea-level change compared to the range of global sea-level projections. Vertical crustal motion is assessed through empirically derived regional isobases, the Earth's predicted response to ice-sheet loading and unloading by the ICE-5G ice sheet reconstruction, and Global Positioning System vertical velocities. Owing to the large rates of crustal uplift from glacial isostatic adjustment across a large region of central Arctic Canada, many communities are projected to experience relative sea-level fall despite projections of global sea-level rise. Where uplift rates are smaller, such as eastern Baffin Island and the western Canadian Arctic, sea-level is projected to rise.

Projecting Future Sea Level Rise for Water Resources Planning in California

NASA Astrophysics Data System (ADS)

Anderson, J.; Kao, K.; Chung, F.

2008-12-01

Sea level rise is one of the major concerns for the management of California's water resources. Higher water levels and salinity intrusion into the Sacramento-San Joaquin Delta could affect water supplies, water quality, levee stability, and aquatic and terrestrial flora and fauna species and their habitat. Over the 20th century, sea levels near San Francisco Bay increased by over 0.6ft. Some tidal gauge and satellite data indicate that rates of sea level rise are accelerating. Sea levels are expected to continue to rise due to increasing air temperatures causing thermal expansion of the ocean and melting of land-based ice such as ice on Greenland and in southeastern Alaska. For water planners, two related questions are raised on the uncertainty of future sea levels. First, what is the expected sea level at a specific point in time in the future, e.g., what is the expected sea level in 2050? Second, what is the expected point of time in the future when sea levels will exceed a certain height, e.g., what is the expected range of time when the sea level rises by one foot? To address these two types of questions, two factors are considered: (1) long term sea level rise trend, and (2) local extreme sea level fluctuations. A two-step approach will be used to develop sea level rise projection guidelines for decision making that takes both of these factors into account. The first step is developing global sea level rise probability distributions for the long term trends. The second step will extend the approach to take into account the effects of local astronomical tides, changes in atmospheric pressure, wind stress, floods, and the El Niño/Southern Oscillation. In this paper, the development of the first step approach is presented. To project the long term sea level rise trend, one option is to extend the current rate of sea level rise into the future. However, since recent data indicate rates of sea level rise are accelerating, methods for estimating sea level rise that account for this acceleration are needed. One such method is an empirical relationship between air temperatures and global sea levels. The air temperature-sea level rise relationship was applied to the 12 climate change projections selected by the California Climate Action Team to estimate future sea levels. The 95% confidence level developed from the historical data was extrapolated to estimate the uncertainties in the future projections. To create sea level rise trend probability distributions, a lognormal probability distribution and a generalized extreme value probability distribution are used. Parameter estimations for these distributions are subjective and inevitably involve uncertainties, which will be improved as more research is conducted in this area.

Hydroclimatic variability in the Levant during the early last glacial (∼ 117-75 ka) derived from micro-facies analyses of deep Dead Sea sediments

NASA Astrophysics Data System (ADS)

Neugebauer, I.; Schwab, M. J.; Waldmann, N. D.; Tjallingii, R.; Frank, U.; Hadzhiivanova, E.; Naumann, R.; Taha, N.; Agnon, A.; Enzel, Y.; Brauer, A.

2015-08-01

The new sediment record from the deep Dead Sea basin (ICDP core 5017-1) provides a unique archive for hydroclimatic variability in the Levant. Here, we present high-resolution sediment facies analysis and elemental composition by μXRF scanning of core 5017-1 to trace lake levels and responses of the regional hydroclimatology during the time interval from ca 117-75 ka, i.e. the transition between the last interglacial and the onset of the last glaciation. We distinguished six major micro-facies types and interpreted these and their alterations in the core in terms of relative lake level changes. The two end-member facies for highest and lowest lake levels are (a) up to several meters thick, greenish sediments of alternating aragonite and detrital marl laminae (aad) and (b) thick halite facies, respectively. Intermediate lake levels are characterised by detrital marls with varying amounts of aragonite, gypsum or halite, reflecting lower-amplitude, shorter-term variability. Two intervals of pronounced lake level drops occurred at ∼110-108 ± 5 and ∼93-87 ± 7 ka. They likely coincide with stadial conditions in the central Mediterranean (Melisey I and II pollen zones in Monticchio) and low global sea levels during MIS 5d and 5b. However, our data do not support the current hypothesis of an almost complete desiccation of the Dead Sea during the earlier of these lake level low stands based on a recovered gravel layer. Based on new petrographic analyses, we propose that, although it was a low stand, this well-sorted gravel layer may be a vestige of a thick turbidite that has been washed out during drilling rather than an in-situ beach deposit. Two intervals of higher lake stands at ∼108-93 ± 6 and ∼87-75 ± 7 ka correspond to interstadial conditions in the central Mediterranean, i.e. pollen zones St. Germain I and II in Monticchio, and GI 24 + 23 and 21 in Greenland, as well as to sapropels S4 and S3 in the Mediterranean Sea. These apparent correlations suggest a close link of the climate in the Levant to North Atlantic and Mediterranean climates during the time of the build-up of Northern Hemisphere ice shields in the early last glacial period.

Hydrodynamic Restoration to Vulnerable Marsh Ecosystems to Improve Response to Sea Level Rise

NASA Astrophysics Data System (ADS)

Orescanin, M. M.; Hamilton, R. P., Jr.

2016-12-01

Rising sea levels pose imminent threats to low-lying marsh ecosystems owing to delicate balances between water levels, salinity, and sediment transport. Further complications arise from human modifications to these low-lying coastal areas that modify topography, thus altering tidal exchanges. The Milford Neck Conservation Area, near Milford, DE, is a salt marsh system on Delaware Bay that has undergone morphological modifications owing to both human activity and natural processes resulting in damage to the surrounding marsh habitats. A century-old abandoned canal acted as a physical barrier to any tidal exchange for upland marsh for decades, allowing land at low elevations to be dry and used for agricultural activities. However, a breach to the system in the 1980s created a link to Delaware Bay that flooded salt hay fields, creating a large area of open water. Owing to tidal restrictions in the system, it has been difficult to transport sufficient sediment and water into the system to promote natural marsh growth. At the same time, the eroding barrier beach increases vulnerability to sea level rise and storms of increasing severity and frequency, and places upland forest at risk of episodic salt intrusion. To increase the effectiveness of this area as a barrier to sea level rise, it is necessary to increase marsh resiliency. Hydrodynamic measurements collected during fall 2015 and spring/summer 2016 show tidal choking in the system that limits exchange of salt water from Delaware Bay and prevents drainage from storm runoff. Numerical model results using the hydrodynamic model, CMS-flow, confirm tidal choking in this system and suggest localized areas are responsible for the most significant reduction in tidal exchange between the marsh and Delaware Bay. Analysis of hypsometry of the area combined with potential for improving tidal flushing suggest the possibility of restoring close to 400 acres of open water and damaged marsh.

Ontogenetic, spatial and temporal variation in trophic level and diet of Chukchi Sea fishes

NASA Astrophysics Data System (ADS)

Marsh, Jennifer M.; Mueter, Franz J.; Iken, Katrin; Danielson, Seth

2017-01-01

Climate warming and increasing development are expected to alter the ecosystem of the Chukchi Sea, including its fish communities. As a component of the Arctic Ecosystem Integrated Survey, we assessed the ontogenetic, spatial and temporal variability of the trophic level and diet of key fish species in the Chukchi Sea using N and C stable isotopes. During August and September of 2012 and 2013, 16 common fish species and two primary, invertebrate consumers were collected from surface, midwater and bottom trawls within the eastern Chukchi Sea. Linear mixed-effects models were used to detect possible variation in the relationship between body length and either δ13C or δ15N values among water masses and years for 13 fish species with an emphasis on Arctic cod (Boreogadus saida). We also examined the fish community isotopic niche space, trophic redundancy, and trophic separation within each water mass as measures of resiliency of the fish food web. Ontogenetic shifts in trophic level and diet were observed for most species and these changes tended to vary by water mass. As they increased in length, most fish species relied more on benthic prey with the exception of three forage fish species (walleye pollock, Gadus chalcogrammus, capelin, Mallotus villosus, and Pacific sandlance, Ammodytes hexapterus). Species that exhibited interannual differences in diet and trophic level were feeding at lower trophic levels and consumed a more pelagic diet in 2012 when zooplankton densities were higher. Fish communities occupied different isotopic niche spaces depending on water mass association. In more northerly Arctic waters, the fish community occupied the smallest isotopic niche space and relied heavily on a limited range of intermediate δ13C prey, whereas in warmer, nutrient-rich Bering Chukchi Summer Water, pelagic prey was important. In the warmest, Pacific-derived coastal water, fish consumed both benthic and pelagic prey. Examining how spatial gradients in trophic position are linked to environmental drivers can provide insight into potential fish community shifts with a changing climate.

Contemporary Arctic Sea Level

NASA Astrophysics Data System (ADS)

Cazenave, A. A.

2017-12-01

During recent decades, the Arctic region has warmed at a rate about twice the rest of the globe. Sea ice melting is increasing and the Greenland ice sheet is losing mass at an accelerated rate. Arctic warming, decrease in the sea ice cover and fresh water input to the Arctic ocean may eventually impact the Arctic sea level. In this presentation, we review our current knowledge of contemporary Arctic sea level changes. Until the beginning of the 1990s, Arctic sea level variations were essentially deduced from tide gauges located along the Russian and Norwegian coastlines. Since then, high inclination satellite altimetry missions have allowed measuring sea level over a large portion of the Arctic Ocean (up to 80 degree north). Measuring sea level in the Arctic by satellite altimetry is challenging because the presence of sea ice cover limits the full capacity of this technique. However adapted processing of raw altimetric measurements significantly increases the number of valid data, hence the data coverage, from which regional sea level variations can be extracted. Over the altimetry era, positive trend patterns are observed over the Beaufort Gyre and along the east coast of Greenland, while negative trends are reported along the Siberian shelf. On average over the Arctic region covered by satellite altimetry, the rate of sea level rise since 1992 is slightly less than the global mea sea level rate (of about 3 mm per year). On the other hand, the interannual variability is quite significant. Space gravimetry data from the GRACE mission and ocean reanalyses provide information on the mass and steric contributions to sea level, hence on the sea level budget. Budget studies show that regional sea level trends over the Beaufort Gyre and along the eastern coast of Greenland, are essentially due to salinity changes. However, in terms of regional average, the net steric component contributes little to the observed sea level trend. The sea level budget in the Arctic indicates a dominant mass contribution, especially in the Greenland, Norwegian, and Barents Seas sector.

Successes and Challenges in Linking Observations and Modeling of Marine and Terrestrial Cryospheric Processes

NASA Astrophysics Data System (ADS)

Herzfeld, U. C.; Hunke, E. C.; Trantow, T.; Greve, R.; McDonald, B.; Wallin, B.

2014-12-01

Understanding of the state of the cryosphere and its relationship to other components of the Earth system requires both models of geophysical processes and observations of geophysical properties and processes, however linking observations and models is far from trivial. This paper looks at examples from sea ice and land ice model-observation linkages to examine some approaches, challenges and solutions. In a sea-ice example, ice deformation is analyzed as a key process that indicates fundamental changes in the Arctic sea ice cover. Simulation results from the Los Alamos Sea-Ice Model CICE, which is also the sea-ice component of the Community Earth System Model (CESM), are compared to parameters indicative of deformation as derived from mathematical analysis of remote sensing data. Data include altimeter, micro-ASAR and image data from manned and unmanned aircraft campaigns (NASA OIB and Characterization of Arctic Sea Ice Experiment, CASIE). The key problem to linking data and model results is the derivation of matching parameters on both the model and observation side.For terrestrial glaciology, we include an example of a surge process in a glacier system and and example of a dynamic ice sheet model for Greenland. To investigate the surge of the Bering Bagley Glacier System, we use numerical forward modeling experiments and, on the data analysis side, a connectionist approach to analyze crevasse provinces. In the Greenland ice sheet example, we look at the influence of ice surface and bed topography, as derived from remote sensing data, on on results from a dynamic ice sheet model.

Prey choice and habitat use drive sea otter pathogen exposure in a resource-limited coastal system

USGS Publications Warehouse

Johnson, Christine K.; Tinker, M. Tim; Estes, James A.; Conrad, Patricia A.; Staedler, Michelle M.; Miller, Melissa A.; Jessup, David A.; Mazet, Jonna A.K.

2014-01-01

The processes promoting disease in wild animal populations are highly complex, yet identifying these processes is critically important for conservation when disease is limiting a population. By combining field studies with epidemiologic tools, we evaluated the relationship between key factors impeding southern sea otter (Enhydra lutris nereis) population growth: disease and resource limitation. This threatened population has struggled to recover despite protection, so we followed radio-tagged sea otters and evaluated infection with 2 disease-causing protozoal pathogens, Toxoplasma gondii and Sarcocystis neurona, to reveal risks that increased the likelihood of pathogen exposure. We identified patterns of pathogen infection that are linked to individual animal behavior, prey choice, and habitat use. We detected a high-risk spatial cluster of S. neurona infections in otters with home ranges in southern Monterey Bay and a coastal segment near San Simeon and Cambria where otters had high levels of infection with T. gondii. We found that otters feeding on abalone, which is the preferred prey in a resource-abundant marine ecosystem, had a very low risk of infection with either pathogen, whereas otters consuming small marine snails were more likely to be infected with T. gondii. Individual dietary specialization in sea otters is an adaptive mechanism for coping with limited food resources along central coastal California. High levels of infection with protozoal pathogens may be an adverse consequence of dietary specialization in this threatened species, with both depleted resources and disease working synergistically to limit recovery.

Subjective emotional over-arousal to neutral social scenes in paranoid schizophrenia.

PubMed

Haralanova, Evelina; Haralanov, Svetlozar; Beraldi, Anna; Möller, Hans-Jürgen; Hennig-Fast, Kristina

2012-02-01

From the clinical practice and some experimental studies, it is apparent that paranoid schizophrenia patients tend to assign emotional salience to neutral social stimuli. This aberrant cognitive bias has been conceptualized to result from increased emotional arousal, but direct empirical data are scarce. The aim of the present study was to quantify the subjective emotional arousal (SEA) evoked by emotionally non-salient (neutral) compared to emotionally salient (negative) social stimuli in schizophrenia patients and healthy controls. Thirty male inpatients with paranoid schizophrenia psychosis and 30 demographically matched healthy controls rated their level of SEA in response to neutral and negative social scenes from the International Affective Picture System and the Munich Affective Picture System. Schizophrenia patients compared to healthy controls had an increased overall SEA level. This relatively higher SEA was evoked only by the neutral but not by the negative social scenes. To our knowledge, the present study is the first designed to directly demonstrate subjective emotional over-arousal to neutral social scenes in paranoid schizophrenia. This finding might explain previous clinical and experimental data and could be viewed as the missing link between the primary neurobiological and secondary psychological mechanisms of paranoid psychotic-symptom formation. Furthermore, despite being very short and easy to perform, the task we used appeared to be sensitive enough to reveal emotional dysregulation, in terms of emotional disinhibition/hyperactivation in paranoid schizophrenia patients. Thus, it could have further research and clinical applications, including as a neurobehavioral probe for imaging studies.

A cross-assessment of CCI-ECVs and RCSM simulations over the Mediterranean area

NASA Astrophysics Data System (ADS)

D'Errico, Miriam; Planton, Serge; Nabat, Pierre

2017-04-01

A first objective of this study, conducted in the framework of the Climate Modelling Users Group (CMUG), one of the projects of the European Space Agency Climate Change Initiative (ESA CCI) program, is a cross-assessment of simulations of a Med-CORDEX regional climate system model (CNRM-RCSM5) and a sub-set of atmosphere, marine and surface interrelated Satellite-Derived Essential Climate Variables (CCI-ECVs) (i.e. sea surface temperature, sea level, aerosols and soil moisture content) over the Mediterranean area. The consistency between the model and the CCI-ECVs is evaluated through the analysis of a climate specific event that can be observed with the CCI-ECVs, in atmospheric reanalysis and reproduced in the RCSM simulations. In this presentation we focus on the July 2006 heat wave that affected the western part of the Mediterranean continental and marine area. The application of a spectral nudging method using ERA-Interim reanalysis in our simulation allows to reproduce this event with a proper chronology. As a result we show that the consistency between the simulated model aerosol optical depth and the ECV products (being produced by the ESA Aerosol CCI project consortium) depends on the choice of the algorithm used to infer the variable from the satellite observations. In particular the heat wave main characteristics become consistent between the model and the satellite-derived observations for sea surface temperature, soil moisture and sea level. The link between the atmospheric circulation and the aerosols distribution is also investigated.

Linking a sea level pressure anomaly dipole over North America to the central Pacific El Niño

NASA Astrophysics Data System (ADS)

Ding, Ruiqiang; Li, Jianping; Tseng, Yu-heng; Sun, Cheng; Zheng, Fei

2017-08-01

This study demonstrates the close connection between the north-south dipole pattern of sea level pressure anomalies over northeastern North America to the western tropical North Atlantic, referred to as the North American dipole (NAD), and the central Pacific (CP)-type El Niño a year later. In contrast to other ENSO precursors, such as the North Pacific Oscillation (NPO) and Pacific-North America (PNA) pattern, the NAD appears more closely related to the CP-type El Niño than to the eastern Pacific (EP)-type El Niño, indicating that the NAD may serve as a unique precursor for the CP El Niño. The wintertime NAD induces sea surface temperature anomalies in the northern tropical Atlantic (NTA), which subsequently play an important role in developing the CP El Niño-like pattern in the tropical Pacific over the course of the following year. It appears that the NAD influence on CP El Niño involves air-sea interaction over several major basins, including the subtropical/tropical Pacific and the NTA. Additional analysis indicates that the correlation of either the NAD index or the NPO index with the CP El Niño state a year later depends on the status of the other index. When the wintertime NAD index is of the opposite sign to the simultaneous NPO index, the correlation of the NAD or NPO index with the Niño4 index becomes much weaker.

Prey choice and habitat use drive sea otter pathogen exposure in a resource-limited coastal system

PubMed Central

Johnson, Christine K.; Tinker, Martin T.; Estes, James A.; Conrad, Patricia A.; Staedler, Michelle; Miller, Melissa A.; Jessup, David A.; Mazet, Jonna A. K.

2009-01-01

The processes promoting disease in wild animal populations are highly complex, yet identifying these processes is critically important for conservation when disease is limiting a population. By combining field studies with epidemiologic tools, we evaluated the relationship between key factors impeding southern sea otter (Enhydra lutris nereis) population growth: disease and resource limitation. This threatened population has struggled to recover despite protection, so we followed radio-tagged sea otters and evaluated infection with 2 disease-causing protozoal pathogens, Toxoplasma gondii and Sarcocystis neurona, to reveal risks that increased the likelihood of pathogen exposure. We identified patterns of pathogen infection that are linked to individual animal behavior, prey choice, and habitat use. We detected a high-risk spatial cluster of S. neurona infections in otters with home ranges in southern Monterey Bay and a coastal segment near San Simeon and Cambria where otters had high levels of infection with T. gondii. We found that otters feeding on abalone, which is the preferred prey in a resource-abundant marine ecosystem, had a very low risk of infection with either pathogen, whereas otters consuming small marine snails were more likely to be infected with T. gondii. Individual dietary specialization in sea otters is an adaptive mechanism for coping with limited food resources along central coastal California. High levels of infection with protozoal pathogens may be an adverse consequence of dietary specialization in this threatened species, with both depleted resources and disease working synergistically to limit recovery. PMID:19164513

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Probabilistic assessment of sea level during the last interglacial stage.

PubMed

Kopp, Robert E; Simons, Frederik J; Mitrovica, Jerry X; Maloof, Adam C; Oppenheimer, Michael

2009-12-17

With polar temperatures approximately 3-5 degrees C warmer than today, the last interglacial stage (approximately 125 kyr ago) serves as a partial analogue for 1-2 degrees C global warming scenarios. Geological records from several sites indicate that local sea levels during the last interglacial were higher than today, but because local sea levels differ from global sea level, accurately reconstructing past global sea level requires an integrated analysis of globally distributed data sets. Here we present an extensive compilation of local sea level indicators and a statistical approach for estimating global sea level, local sea levels, ice sheet volumes and their associated uncertainties. We find a 95% probability that global sea level peaked at least 6.6 m higher than today during the last interglacial; it is likely (67% probability) to have exceeded 8.0 m but is unlikely (33% probability) to have exceeded 9.4 m. When global sea level was close to its current level (>or=-10 m), the millennial average rate of global sea level rise is very likely to have exceeded 5.6 m kyr(-1) but is unlikely to have exceeded 9.2 m kyr(-1). Our analysis extends previous last interglacial sea level studies by integrating literature observations within a probabilistic framework that accounts for the physics of sea level change. The results highlight the long-term vulnerability of ice sheets to even relatively low levels of sustained global warming.

The relationship between Arabian Sea upwelling and Indian Monsoon revisited in a high resolution ocean simulation

NASA Astrophysics Data System (ADS)

Yi, Xing; Hünicke, Birgit; Tim, Nele; Zorita, Eduardo

2018-01-01

Studies based on sediment records, sea-surface temperature and wind suggest that upwelling along the western coast of Arabian Sea is strongly affected by the Indian summer Monsoon. We examine this relationship directly in an eddy-resolving global ocean simulation STORM driven by atmospheric reanalysis over the last 61 years. With its very high spatial resolution (10 km), STORM allows us to identify characteristics of the upwelling system. We analyse the co-variability between upwelling and meteorological and oceanic variables from 1950 to 2010. The analysis reveals high interannual correlations between coastal upwelling and along-shore wind-stress (r = 0.73) as well as with sea-surface temperature (r = -0.83). However, the correlation between the upwelling and the Monsoon is small. We find an atmospheric circulation pattern different from the one that drives the Monsoon as the main modulator of the upwelling variability. In spite of this, the patterns of temperature anomalies that are either linked to Arabian Sea upwelling or to the Monsoon are spatially quite similar, although the physical mechanisms of these links are different. In addition, no long-term trend is detected in our modelled upwelling in the Arabian Sea.

Two Sea-Level Challenges

NASA Astrophysics Data System (ADS)

Galvin, C.

2008-12-01

"No place on the sandy ocean shores of the world has been shown to be eroding because of sea level rise." This statement appeared nearly 19 years ago in bold print at the top of the page in a brief article published in Shore and Beach (Galvin,1990). The term "sea level rise" was defined in 1990 as follows: "In this statement, "sea level rise" has the meaning that the average person on the street usually attaches to that term. That is, sea level is rising; not, as in some places like the Mississippi River delta, land level is sinking." While still a subject of controversy, it is now (2008) increasingly plausible (Tornqvist et al,2008) that damage from Hurricane Katrina was significantly worse on the Mississippi River delta because floodwaters exploited wetlands and levees whose elevations had been lowered by decades of compaction in the underlying soil. (1) "Sea level" commonly appears in the literature as "relative sea level rise", occurring that way in 711 publications between 1980 and 2009 (GeoRef database on 8 Sep 08). "Relative sea level rise" does not appear in the 2005 AGI Glossary. The nearest Glossary term is "relative change in sea level", but that term occurs in only 12 publications between 1980 and 2009. The Glossary defines this term in a sequence stratigraphy sense, which infers that "relative sea level rise" is the sum of bottom subsidence and eustatic sea level rise. In plain English, "relative sea level rise" means "water depth increase". For present day coastal environments, "relative sea level rise" is commonly used where eustatic sea level rise is less than subsidence, that is, where the magnitude of actual sea level rise is smaller than the magnitude of subsidence. In that situation, "relative sea level rise" misleads both the average person and the scientist who is not a coastal geologist. Thus, the first challenge is to abandon "relative sea level rise" in favor of "water depth increase", in order that the words accurately descibe what happens. It would further clarify popular understanding if the term "actual sea level rise" were used in place of "eustatic sea level rise". (2)Geologists have approximated the the practice of paleontologists and biologists in establishing type examples of important geological features. This is a useful practice. A graduate geologist holds in mind clear conceptions of "beach cusps", "drumlin fields", "birdfoot deltas", and "igneous sills" based on seeing field examples accepted by professional geologists as representative of these features. However, although publications frequently report that sea level rise erodes a particular beach, no one identifies a type beach where that cause has been proven to produce the alleged effect. At the type beach, it is necessary to show that sea level is rising, and that the beach erodes primarily from this sea level rise, rather than from interrupted longshore transport. Thus, the second challenge is to identify a type ocean beach proven to erode because of sea level rise.

Management-focused approach to investigating coastal water-quality drivers and impacts in the Baltic Sea

NASA Astrophysics Data System (ADS)

Vigouroux, G.; Destouni, G.; Chen, Y.; Bring, A.; Jönsson, A.; Cvetkovic, V.

2017-12-01

Coastal areas link human-driven conditions on land with open sea conditions, and include crucial and vulnerable ecosystems that provide a variety of ecosystem services. Eutrophication is a common problem that is not least observed in the Baltic Sea, where coastal water quality is influenced both by land-based nutrient loading and by partly eutrophic open sea conditions. Robust and adaptive management of coastal systems is essential and necessitates integration of large scale catchment-coastal-marine systems as well as consideration of anthropogenic drivers and impacts, and climate change. To address this coastal challenge, relevant methodological approaches are required for characterization of coupled land, local coastal, and open sea conditions under an adaptive management framework for water quality. In this paper we present a new general and scalable dynamic characterization approach, developed for and applied to the Baltic Sea and its coastal areas. A simple carbon-based water quality model is implemented, dividing the Baltic Sea into main management basins that are linked to corresponding hydrological catchments on land, as well as to each other though aggregated three-dimensional marine hydrodynamics. Relevant hydrodynamic variables and associated water quality results have been validated on the Baltic Sea scale and show good accordance with available observation data and other modelling approaches. Based on its scalability, this methodology is further used on coastal zone scale to investigate the effects of hydrodynamic, hydro-climatic and nutrient load drivers on water quality and management implications for coastal areas in the Baltic Sea.

Reconstruction of Local Sea Levels at South West Pacific Islands—A Multiple Linear Regression Approach (1988-2014)

NASA Astrophysics Data System (ADS)

Kumar, V.; Melet, A.; Meyssignac, B.; Ganachaud, A.; Kessler, W. S.; Singh, A.; Aucan, J.

2018-02-01

Rising sea levels are a critical concern in small island nations. The problem is especially serious in the western south Pacific, where the total sea level rise over the last 60 years has been up to 3 times the global average. In this study, we aim at reconstructing sea levels at selected sites in the region (Suva, Lautoka—Fiji, and Nouméa—New Caledonia) as a multilinear regression (MLR) of atmospheric and oceanic variables. We focus on sea level variability at interannual-to-interdecadal time scales, and trend over the 1988-2014 period. Local sea levels are first expressed as a sum of steric and mass changes. Then a dynamical approach is used based on wind stress curl as a proxy for the thermosteric component, as wind stress curl anomalies can modulate the thermocline depth and resultant sea levels via Rossby wave propagation. Statistically significant predictors among wind stress curl, halosteric sea level, zonal/meridional wind stress components, and sea surface temperature are used to construct a MLR model simulating local sea levels. Although we are focusing on the local scale, the global mean sea level needs to be adjusted for. Our reconstructions provide insights on key drivers of sea level variability at the selected sites, showing that while local dynamics and the global signal modulate sea level to a given extent, most of the variance is driven by regional factors. On average, the MLR model is able to reproduce 82% of the variance in island sea level, and could be used to derive local sea level projections via downscaling of climate models.

The deep-sea hub of the ANTARES neutrino telescope

NASA Astrophysics Data System (ADS)

Anghinolfi, M.; Calzas, A.; Dinkespiler, B.; Cuneo, S.; Favard, S.; Hallewell, G.; Jaquet, M.; Musumeci, M.; Papaleo, R.; Raia, G.; Valdy, P.; Vernin, P.

2006-11-01

The ANTARES neutrino telescope, currently under construction at 2500 m depth off the French Mediterranean coast, will contain 12 detection lines, powered and read out through a deep-sea junction box (JB) hub. Electrical energy from the shore station is distributed through a transformer with multiple secondary windings and a plugboard with 16 deep sea-mateable electro-optic connectors. Connections are made to the JB outputs using manned or remotely operated submersible vehicles. The triply redundant power management and slow control system is based on two identical AC-powered systems, communicating with the shore through 160 Mb/s fibre G-links and a third battery-powered system using a slower link. We describe the power and slow control systems of the underwater hub.

Nano-tags for neonates and ocean-mediated swimming behaviours linked to rapid dispersal of hatchling sea turtles

PubMed Central

Scott, Rebecca; Biastoch, Arne; Roder, Christian; Stiebens, Victor A.; Eizaguirre, Christophe

2014-01-01

Dispersal during juvenile life stages drives the life-history evolution and dynamics of many marine vertebrate populations. However, the movements of juvenile organisms, too small to track using conventional satellite telemetry devices, remain enigmatic. For sea turtles, this led to the paradigm of the ‘lost years' since hatchlings disperse widely with ocean currents. Recently, advances in the miniaturization of tracking technology have permitted the application of nano-tags to track cryptic organisms. Here, the novel use of acoustic nano-tags on neonate loggerhead turtle hatchlings enabled us to witness first-hand their dispersal and behaviour during their first day at sea. We tracked hatchlings distances of up to 15 km and documented their rapid transport (up to 60 m min−1) with surface current flows passing their natal areas. Tracking was complemented with laboratory observations to monitor swimming behaviours over longer periods which highlighted (i) a positive correlation between swimming activity levels and body size and (ii) population-specific swimming behaviours (e.g. nocturnal inactivity) suggesting local oceanic conditions drive the evolution of innate swimming behaviours. Knowledge of the swimming behaviours of small organisms is crucial to improve the accuracy of ocean model simulations used to predict the fate of these organisms and determine resultant population-level implications into adulthood. PMID:25339720

Acceleration of Sea Level Rise Over Malaysian Seas from Satellite Altimeter

NASA Astrophysics Data System (ADS)

Hamid, A. I. A.; Din, A. H. M.; Khalid, N. F.; Omar, K. M.

2016-09-01

Sea level rise becomes our concern nowadays as a result of variously contribution of climate change that cause by the anthropogenic effects. Global sea levels have been rising through the past century and are projected to rise at an accelerated rate throughout the 21st century. Due to this change, sea level is now constantly rising and eventually will threaten many low-lying and unprotected coastal areas in many ways. This paper is proposing a significant effort to quantify the sea level trend over Malaysian seas based on the combination of multi-mission satellite altimeters over a period of 23 years. Eight altimeter missions are used to derive the absolute sea level from Radar Altimeter Database System (RADS). Data verification is then carried out to verify the satellite derived sea level rise data with tidal data. Eight selected tide gauge stations from Peninsular Malaysia, Sabah and Sarawak are chosen for this data verification. The pattern and correlation of both measurements of sea level anomalies (SLA) are evaluated over the same period in each area in order to produce comparable results. Afterwards, the time series of the sea level trend is quantified using robust fit regression analysis. The findings clearly show that the absolute sea level trend is rising and varying over the Malaysian seas with the rate of sea level varies and gradually increase from east to west of Malaysia. Highly confident and correlation level of the 23 years measurement data with an astonishing root mean square difference permits the absolute sea level trend of the Malaysian seas has raised at the rate 3.14 ± 0.12 mm yr-1 to 4.81 ± 0.15 mm yr-1 for the chosen sub-areas, with an overall mean of 4.09 ± 0.12 mm yr-1. This study hopefully offers a beneficial sea level information to be applied in a wide range of related environmental and climatology issue such as flood and global warming.

EVAPORITE MICROBIAL FILMS, MATS, MICROBIALITES AND STROMATOLITES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brigmon, R; Penny Morris, P; Garriet Smith, G

2008-01-28

Evaporitic environments are found in a variety of depositional environments as early as the Archean. The depositional settings, microbial community and mineralogical composition vary significantly as no two settings are identical. The common thread linking all of the settings is that evaporation exceeds precipitation resulting in elevated concentrations of cations and anions that are higher than in oceanic systems. The Dead Sea and Storrs Lake are examples of two diverse modern evaporitic settings as the former is below sea level and the latter is a coastal lake on an island in the Caribbean. Each system varies in water chemistry asmore » the Dead Sea dissolved ions originate from surface weathered materials, springs, and aquifers while Storrs Lake dissolved ion concentration is primarily derived from sea water. Consequently some of the ions, i.e., Sr, Ba are found at significantly lower concentrations in Storrs Lake than in the Dead Sea. The origin of the dissolved ions are ultimately responsible for the pH of each system, alkaline versus mildly acidic. Each system exhibits unique biogeochemical properties as the extreme environments select certain microorganisms. Storrs Lake possesses significant biofilms and stromatolitic deposits and the alkalinity varies depending on rainfall and storm activity. The microbial community Storrs Lake is much more diverse and active than those observed in the Dead Sea. The Dead Sea waters are mildly acidic, lack stromatolites, and possess a lower density of microbial populations. The general absence of microbial and biofilm fossilization is due to the depletion of HCO{sub 3} and slightly acidic pH.« less

A search for scale in sea-level studies

USGS Publications Warehouse

Larsen, C.E.; Clark, I.

2006-01-01

Many researchers assume a proportional relationship among the atmospheric CO2 concentration, temperature, and sea level. Thus, the rate of sea-level rise should increase in concert with the documented exponential increase in CO2. Although sea surface temperature has increased in places over the past century and short-term sea level rose abruptly during the 1990s, it is difficult to demonstrate a proportional relationship using existing geologic or historic records. Tide gauge records in the United States cover too short a time interval to verify acceleration in the rate of sea-level rise, although multicentury tide gauge and staff records from the Netherlands and Sweden suggest a mid-19th-century acceleration in sea-level rise. Reconstructions of sea-level changes for the past 1000 years derived using benthic foraminifer data from salt marshes along the East Coast of the United States suggest an increased rate of relative sea-level rise beginning in the 1600s. Geologic records of relative sea-level rise for the past 6000 years are available for several sites along the US East Coast from 14C-dated basal peat below salt marshes and estuarine sediments. When these three scales of sea-level variation are integrated, adjusted for postglacial isostatic movement, and replotted, the range of variation in sea level suggested by basal peat ages is within ??1 meter of the long-term trend. The reconstruction from Long Island Sound data shows a linear rise in sea level beginning in the mid-1600s at a rate consistent with the historic record of mean high water. Long-term tide gauge records from Europe and North America show similar trends since the mid-19th century. There is no clear proportional exponential increase in the rate of sea-level rise. If proportionality exists among sea level, atmospheric CO2, and temperature, there may be a significant time lag before an anthropogenic increase in the rate of sea-level rise occurs.

Variability and change of sea level and its components in the Indo-Pacific region during the altimetry era

NASA Astrophysics Data System (ADS)

Wu, Quran; Zhang, Xuebin; Church, John A.; Hu, Jianyu

2017-03-01

Previous studies have shown that regional sea level exhibits interannual and decadal variations associated with the modes of climate variability. A better understanding of those low-frequency sea level variations benefits the detection and attribution of climate change signals. Nonetheless, the contributions of thermosteric, halosteric, and mass sea level components to sea level variability and trend patterns remain unclear. By focusing on signals associated with dominant climate modes in the Indo-Pacific region, we estimate the interannual and decadal fingerprints and trend of each sea level component utilizing a multivariate linear regression of two adjoint-based ocean reanalyses. Sea level interannual, decadal, and trend patterns primarily come from thermosteric sea level (TSSL). Halosteric sea level (HSSL) is of regional importance in the Pacific Ocean on decadal time scale and dominates sea level trends in the northeast subtropical Pacific. The compensation between TSSL and HSSL is identified in their decadal variability and trends. The interannual and decadal variability of temperature generally peak at subsurface around 100 m but that of salinity tend to be surface-intensified. Decadal temperature and salinity signals extend deeper into the ocean in some regions than their interannual equivalents. Mass sea level (MassSL) is critical for the interannual and decadal variability of sea level over shelf seas. Inconsistencies exist in MassSL trend patterns among various estimates. This study highlights regions where multiple processes work together to control sea level variability and change. Further work is required to better understand the interaction of different processes in those regions.

Development and carbon sequestration of tropical peat domes in south-east Asia: links to post-glacial sea-level changes and Holocene climate variability

NASA Astrophysics Data System (ADS)

Dommain, René; Couwenberg, John; Joosten, Hans

2011-04-01

Tropical peatlands of SE-Asia represent a significant terrestrial carbon reservoir of an estimated 65 Gt C. In this paper we present a comprehensive data synthesis of radiocarbon dated peat profiles and 31 basal dates of ombrogenous peat domes from the lowlands of Peninsular Malaysia, Sumatra and Borneo and integrate our peatland data with records of past sea-level and climate change in the region. Based on their developmental features three peat dome regions were distinguished: inland Central Kalimantan (Borneo), Kutai basin (Borneo) and coastal areas across the entire region. With the onset of the Holocene the first peat domes developed in Central Kalimantan as a response to rapid post-glacial sea-level rise over the Sunda Shelf and intensification of the Asian monsoon. Peat accumulation rates in Central Kalimantan strongly declined after 8500 cal BP in close relation to the lowering rate of the sea-level rise and possibly influenced by the regional impact of the 8.2 ka event. Peat growth in Central Kalimantan apparently ceased during the Late Holocene in association with amplified El Niño activity as exemplified by several truncated peat profiles. Peat domes from the Kutai basin are all younger than ˜8300 cal BP. Peat formation and rates of peat accumulation were driven by accretion rates of the Mahakam River and seemingly independent of climate. Most coastal peat domes, the largest expanse of SE-Asian peatlands, initiated between 7000 and 4000 cal BP as a consequence of a Holocene maximum in regional rainfall and the stabilisation and subsequent regression of the sea-level. These boundary conditions induced the highest rates of peat accumulation of coastal peat domes. The Late Holocene sea-level regression led to extensive new land availability that allowed for continued coastal peat dome formation until the present. The time weighted mean Holocene peat accumulation rate is 0.54 mm yr -1 for Central Kalimantan, 1.89 mm yr -1 for Kutai and 1.77 mm yr -1 for coastal domes of Sumatra and Borneo. The mean Holocene carbon sequestration rates amount to 31.3 g C m -2 yr -1 for Central Kalimantan and 77.0 g C m -2 yr -1 for coastal sites, which makes coastal peat domes of south-east Asia the spatially most efficient terrestrial ecosystem in terms of long term carbon sequestration.

Linking mercury exposure to habitat and feeding behaviour in Beaufort Sea beluga whales

NASA Astrophysics Data System (ADS)

Loseto, L. L.; Stern, G. A.; Deibel, D.; Connelly, T. L.; Prokopowicz, A.; Lean, D. R. S.; Fortier, L.; Ferguson, S. H.

2008-12-01

Mercury (Hg) levels in the Beaufort Sea beluga population have been increasing since the 1990's. Ultimately, it is the Hg content of prey that determines beluga Hg levels. However, the Beaufort Sea beluga diet is not understood, and little is known about the diet Hg sources in their summer habitat. During the summer, they segregate into social groups based on habitat use leading to the hypothesis that they may feed in different food webs explaining Hg dietary sources. Methyl mercury (MeHg) and total mercury (THg) levels were measured in the estuarine-shelf, Amundsen Gulf and epibenthic food webs in the western Canadian Arctic collected during the Canadian Arctic Shelf Exchange Study (CASES) to assess their dietary Hg contribution. To our knowledge, this is the first study to report MeHg levels in estuarine fish and epibenthic invertebrates from the Arctic Ocean. Although the Mackenzie River is a large source of Hg, the estuarine-shelf prey items had the lowest MeHg levels, ranging from 0.1 to 0.27 μg/g dry weight (dw) in arctic cisco ( Coregonus autumnalis) and saffron cod ( Eleginus gracilis) respectively. Highest MeHg levels occurred in fourhorn sculpin ( Myoxocephalus quadricornis) (0.5 μg/g dw) from the epibenthic food web. Beluga hypothesized to feed in the epibenthic and Amundsen Gulf food webs had the highest Hg levels matching with high Hg levels in associated food webs, and estuarine-shelf belugas had the lowest Hg levels (2.6 μg/g dw), corresponding with the low food web Hg levels, supporting the variation in dietary Hg uptake. The trophic level transfer of Hg was similar among the food webs, highlighting the importance of Hg sources at the bottom of the food web as well as food web length. We propose that future biomagnification studies incorporate predator behaviour with food web structure to assist in the evaluation of dietary Hg sources.

Cretaceous shelf-sea chalk deposits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hattin, D.E.

1988-01-01

The word ''chalk'' is linked etymologically to the Cretaceous, but chalky facies neither dominate that system nor are confined to it. As used commonly, the term ''chalk'' refers to a variety of marine limestone that is white to light gray very fine grained, soft and friable, porous, and composed predominantly of calcitic skeletal remains, especially those derived from coccolithophores. No simple definition suffices to embrace all Cretaceous chalks, which include sandy, marly, shelly, phospatic, glauconitic, dolomitic, pyritic and organic-rich lithotypes. Most of the world's exposed Cretaceous chalk deposits were formed at shelf depths rather than in the deep sea. Cretaceousmore » shelf-sea chalks are developed most extensively in northern Europe, the U.S. Gulf Coastal Plain and Western Interior, and the Middle East, with lesser occurrences alo in Australia. Most Cretaceous shelf-sea chalks formed in the temperature zones, and in relatively deep water. Cretaceous chalks deposited on well-oxygenated sea floors are bioturbated and massive where deficient in terrigenous detritus, or bioturbated and rhythmically interbedded with argillaceous units where influx of terrigenous detritus varied systematically with climate changes. Accumulation of sufficient pelagic mud to form vast deposits of Cretaceous shelf-sea chalk required (1) sustained high productivity of calareous plankton, (2) extensive development of stable shelf and continental platform environments, (3) highstands of seal level, (4) deficiency of aragonitic skeletal material in chalk-forming sediments, and (5) low rates of terrigenous detrital influx. These conditions were met at different times in different places, even within the same general region.« less

Links between atmosphere, ocean, and cryosphere from two decades of microseism observations on the Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Anthony, Robert E.; Aster, Richard C.; McGrath, Daniel

2017-01-01

The lack of landmasses, climatological low pressure, and strong circumpolar westerly winds between the latitudes of 50°S to 65°S produce exceptional storm-driven wave conditions in the Southern Ocean. This combination makes the Antarctic Peninsula one of Earth's most notable regions of high-amplitude wave activity and thus, ocean-swell-driven microseism noise in both the primary (direct wave-coastal region interactions) and secondary (direct ocean floor forcing due to interacting wave trains) period bands. Microseism observations are examined across 23 years (1993-2015) from Palmer Station (PMSA), on the west coast of the Antarctic Peninsula, and from East Falkland Island (EFI). These records provide a spatially integrative measure of both Southern Ocean wave amplitudes and the interactions between ocean waves and the solid Earth in the presence of sea ice, which can reduce wave coupling with the continental shelf. We utilize a spatiotemporal correlation-based approach to illuminate how the distribution of sea ice influences seasonal microseism power. We characterize primary and secondary microseism power due to variations in sea ice and find that primary microseism energy is both more sensitive to sea ice and more capable of propagating across ocean basins than secondary microseism energy. During positive phases of the Southern Annular Mode, sea ice is reduced in the Bellingshausen Sea and overall storm activity in the Drake Passage increases, thus strongly increasing microseism power levels.

Sea Grant Extension Crucial Link to Coastal Resources.

ERIC Educational Resources Information Center

Stumbos, John

1997-01-01

University of California Sea Grant Extension Program provides training and technical assistance to fishers, farmers, planners, and conservationists on projects such as coastal ecosystem health, marine environmental protection, fisheries management, aquaculture, salmon habitat restoration, and controlling nonpoint-source pollution; supports…

Patterns of ecological specialization among microbial populations in the Red Sea and diverse oligotrophic marine environments

PubMed Central

Thompson, Luke R; Field, Chris; Romanuk, Tamara; Ngugi, David; Siam, Rania; El Dorry, Hamza; Stingl, Ulrich

2013-01-01

Large swaths of the nutrient-poor surface ocean are dominated numerically by cyanobacteria (Prochlorococcus), cyanobacterial viruses (cyanophage), and alphaproteobacteria (SAR11). How these groups thrive in the diverse physicochemical environments of different oceanic regions remains poorly understood. Comparative metagenomics can reveal adaptive responses linked to ecosystem-specific selective pressures. The Red Sea is well-suited for studying adaptation of pelagic-microbes, with salinities, temperatures, and light levels at the extreme end for the surface ocean, and low nutrient concentrations, yet no metagenomic studies have been done there. The Red Sea (high salinity, high light, low N and P) compares favorably with the Mediterranean Sea (high salinity, low P), Sargasso Sea (low P), and North Pacific Subtropical Gyre (high light, low N). We quantified the relative abundance of genetic functions among Prochlorococcus, cyanophage, and SAR11 from these four regions. Gene frequencies indicate selection for phosphorus acquisition (Mediterranean/Sargasso), DNA repair and high-light responses (Red Sea/Pacific Prochlorococcus), and osmolyte C1 oxidation (Red Sea/Mediterranean SAR11). The unexpected connection between salinity-dependent osmolyte production and SAR11 C1 metabolism represents a potentially major coevolutionary adaptation and biogeochemical flux. Among Prochlorococcus and cyanophage, genes enriched in specific environments had ecotype distributions similar to nonenriched genes, suggesting that inter-ecotype gene transfer is not a major source of environment-specific adaptation. Clustering of metagenomes using gene frequencies shows similarities in populations (Red Sea with Pacific, Mediterranean with Sargasso) that belie their geographic distances. Taken together, the genetic functions enriched in specific environments indicate competitive strategies for maintaining carrying capacity in the face of physical stressors and low nutrient availability. PMID:23789085

Patterns of ecological specialization among microbial populations in the Red Sea and diverse oligotrophic marine environments.

PubMed

Thompson, Luke R; Field, Chris; Romanuk, Tamara; Ngugi, David; Siam, Rania; El Dorry, Hamza; Stingl, Ulrich

2013-06-01

Large swaths of the nutrient-poor surface ocean are dominated numerically by cyanobacteria (Prochlorococcus), cyanobacterial viruses (cyanophage), and alphaproteobacteria (SAR11). How these groups thrive in the diverse physicochemical environments of different oceanic regions remains poorly understood. Comparative metagenomics can reveal adaptive responses linked to ecosystem-specific selective pressures. The Red Sea is well-suited for studying adaptation of pelagic-microbes, with salinities, temperatures, and light levels at the extreme end for the surface ocean, and low nutrient concentrations, yet no metagenomic studies have been done there. The Red Sea (high salinity, high light, low N and P) compares favorably with the Mediterranean Sea (high salinity, low P), Sargasso Sea (low P), and North Pacific Subtropical Gyre (high light, low N). We quantified the relative abundance of genetic functions among Prochlorococcus, cyanophage, and SAR11 from these four regions. Gene frequencies indicate selection for phosphorus acquisition (Mediterranean/Sargasso), DNA repair and high-light responses (Red Sea/Pacific Prochlorococcus), and osmolyte C1 oxidation (Red Sea/Mediterranean SAR11). The unexpected connection between salinity-dependent osmolyte production and SAR11 C1 metabolism represents a potentially major coevolutionary adaptation and biogeochemical flux. Among Prochlorococcus and cyanophage, genes enriched in specific environments had ecotype distributions similar to nonenriched genes, suggesting that inter-ecotype gene transfer is not a major source of environment-specific adaptation. Clustering of metagenomes using gene frequencies shows similarities in populations (Red Sea with Pacific, Mediterranean with Sargasso) that belie their geographic distances. Taken together, the genetic functions enriched in specific environments indicate competitive strategies for maintaining carrying capacity in the face of physical stressors and low nutrient availability.

Polygenetic Karsted Hardground Omission Surfaces in Lower Silurian Neritic Limestones: a Signature of Early Paleozoic Calcite Seas

NASA Astrophysics Data System (ADS)

James, Noel P.; Desrochers, André; Kyser, Kurt T.

2015-04-01

Exquisitely preserved and well-exposed rocky paleoshoreline omission surfaces in Lower Silurian Chicotte Formation limestones on Anticosti Island, Quebec, are interpreted to be the product of combined marine and meteoric diagenesis. The different omission features include; 1) planar erosional bedding tops, 2) scalloped erosional surfaces, 3) knobs, ridges, and swales at bedding contacts, and 4) paleoscarps. An interpretation is proposed that relates specific omission surface styles to different diagenetic-depositional processes that took place in separate terrestrial-peritidal-shallow neritic zones. Such processes were linked to fluctuations in relative sea level with specific zones of diagenesis such as; 1) karst corrosion, 2) peritidal erosion, 3) subtidal seawater flushing and cementation, and 4) shallow subtidal deposition. Most surfaces are interpreted to have been the result of initial extensive shallow-water synsedimentary lithification that were, as sea level fell, altered by exposure and subaerial corrosion, only to be buried by sediments as sea level rose again. This succession was repeated several times resulting in a suite of recurring polyphase omission surfaces through many meters of stratigraphic section. Synsedimentary cloudy marine cements are well preserved and are thus interpreted to have been calcitic originally. Aragonite components are rare and thought to have to have been dissolved just below the Silurian seafloor. Large molluscs that survived such seafloor removal were nonetheless leached and the resultant megamoulds were filled with synsedimentary calcite cement. These Silurian inner neritic-strandline omission surfaces are temporally unique. They are part of a suite of marine omission surfaces that are mostly found in early Paleozoic neritic carbonate sedimentary rocks. These karsted hardgrounds formed during a calcite-sea time of elevated marine carbonate saturation and extensive marine cement precipitation. The contemporaneous greenhouse atmosphere was supercharged with CO2 leading to profound surface karst under strongly acid rain. Younger peritidal omission surfaces, although potentially formed during aragonite or calcite sea times, would have been subject to very different terrestrial diagenetic process with lower atmospheric pCO2 values but increasingly complex biogenic soils producing dissimilar alteration features.

Strategic environmental assessment for sustainability: A review of a decade of academic research

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, Lisa, E-mail: lisa.white@usask.ca; Noble, Bram F., E-mail: b.noble@usask.ca

This paper examines the strategic environmental assessment (SEA)–sustainability relationship over the past decade, from 2000 to 2010, focusing in particular on the incorporation of sustainability in SEA. A total of 86 papers from the academic literature containing the terms ‘sustainability’ or ‘sustainable development’ and ‘strategic environmental assessment’ were identified and reviewed. Several common themes emerged by which SEA can support sustainability, including providing a framework to support decision making for sustainability; setting sustainability objectives, ensuring the consideration of ‘more sustainable’ alternatives, and integrating sustainability criteria in PPP development; and promoting sustainability outcomes through tiering and institutional learning. At the samemore » time, our review identified many underlying barriers that challenge SEA for sustainability, including the variable interpretations of the scope of sustainability in SEA; the limited use of assessment criteria directly linked to sustainability objectives; and challenges for decision-makers in operationalizing sustainability in SEA and adapting PPP development decision-making processes to include sustainability issues. To advance SEA for sustainability there is a need to better define the scope of sustainability in SEA; clarify how to operationalize the different approaches to sustainability in SEA, as opposed to simply describing those approaches; provide guidance on how to operationalize broad sustainability goals through assessment criteria in SEA; and understand better how to facilitate institutional learning regarding sustainability through SEA application. -- Highlights: ► There is significant potential for SEA to support sustainability in PPP development. ► However, there are still many barriers in place that challenge SEA for sustainability. ► The scope and approaches to sustainability in SEA must be better defined and described. ► Guidance is needed to link impact assessment criteria to sustainability objectives. ► Focus on how to facilitate institutional learning regarding sustainability is required.« less

Current state and future perspectives on coupled ice-sheet - sea-level modelling

NASA Astrophysics Data System (ADS)

de Boer, Bas; Stocchi, Paolo; Whitehouse, Pippa L.; van de Wal, Roderik S. W.

2017-08-01

The interaction between ice-sheet growth and retreat and sea-level change has been an established field of research for many years. However, recent advances in numerical modelling have shed new light on the precise interaction of marine ice sheets with the change in near-field sea level, and the related stability of the grounding line position. Studies using fully coupled ice-sheet - sea-level models have shown that accounting for gravitationally self-consistent sea-level change will act to slow down the retreat and advance of marine ice-sheet grounding lines. Moreover, by simultaneously solving the 'sea-level equation' and modelling ice-sheet flow, coupled models provide a global field of relative sea-level change that is consistent with dynamic changes in ice-sheet extent. In this paper we present an overview of recent advances, possible caveats, methodologies and challenges involved in coupled ice-sheet - sea-level modelling. We conclude by presenting a first-order comparison between a suite of relative sea-level data and output from a coupled ice-sheet - sea-level model.

Robustness of observation-based decadal sea level variability in the Indo-Pacific Ocean

NASA Astrophysics Data System (ADS)

Nidheesh, A. G.; Lengaigne, M.; Vialard, J.; Izumo, T.; Unnikrishnan, A. S.; Meyssignac, B.; Hamlington, B.; de Boyer Montegut, C.

2017-07-01

We examine the consistency of Indo-Pacific decadal sea level variability in 10 gridded, observation-based sea level products for the 1960-2010 period. Decadal sea level variations are robust in the Pacific, with more than 50% of variance explained by decadal modulation of two flavors of El Niño-Southern Oscillation (classical ENSO and Modoki). Amplitude of decadal sea level variability is weaker in the Indian Ocean than in the Pacific. All data sets indicate a transmission of decadal sea level signals from the western Pacific to the northwest Australian coast through the Indonesian throughflow. The southern tropical Indian Ocean sea level variability is associated with decadal modulations of ENSO in reconstructions but not in reanalyses or in situ data set. The Pacific-independent Indian Ocean decadal sea level variability is not robust but tends to be maximum in the southwestern tropical Indian Ocean. The inconsistency of Indian Ocean decadal variability across the sea level products calls for caution in making definitive conclusions on decadal sea level variability in this basin.

Diatom-inferred hydrological changes and Holocene geomorphic transitioning of Africa's largest estuarine system, Lake St Lucia

NASA Astrophysics Data System (ADS)

Gomes, M.; Humphries, M. S.; Kirsten, K. L.; Green, A. N.; Finch, J. M.; de Lecea, A. M.

2017-06-01

The diverse lagoons and coastal lakes along the east coast of South Africa occupy incised valleys that were flooded during the rise and subsequent stabilisation of relative sea-level during the Holocene. Sedimentary deposits contained within these waterbodies provide an opportunity to investigate complex hydrological and sedimentological processes, and examine sea-level controls governing system geomorphic evolution. In this paper, we combine diatom and sulfur isotope analyses from two sediment cores extracted from the northern sub-basins of Lake St Lucia, a large shallow estuarine lake that is today largely isolated from direct ocean influence behind a Holocene-Pleistocene barrier complex. Analyses allow the reconstruction of hydrological changes associated with the geomorphic development of the system over the mid-to late Holocene. The sedimentary sequences indicate that St Lucia was a shallow, partially enclosed estuary/embayment dominated by strong tidal flows prior to ∼6200 cal. BP. Infilling was initiated when sea-level rise slowed and stabilised around present day levels, resulting in the accumulation of fine-grained sediment behind an emergent proto-barrier. Diatom assemblages, dominated by marine benthic and epiphytic species, reveal a system structured by marine water influx and characterised by marsh and tidal flat habitats until ∼4550 cal. BP. A shift in the biological community at ∼4550 cal. BP is linked to the development of a back-barrier water body that supported a brackish community. Marine planktonics and enrichments in δ34S suggest recurrent, large-scale barrier inundation events during this time, coincident with a mid-Holocene sea-level highstand. Periodic marine incursions associated with episodes of enhanced storminess and overwash remained prevalent until ∼1200 cal. BP, when further barrier construction ultimately isolated the northern basins from the ocean. This study provides the first reconstruction of the palaeohydrological environment at Lake St Lucia and highlights the long-term geomorphic controls that have shaped the recent evolution and natural dynamics of the system. Unlike most coastal lake systems, this system is particularly effective as an archive of geomorphological change. Systems driven by back-barrier modifications, such as Lake St Lucia, highlight how geomorphological changes driven by sediment-supply, climate and sea level can be distributed unevenly over several isolated back-barrier basins.

Immunostimulation of Salmo salar L., and its effect on Lepeophtheirus salmonis (Krøyer) P-glycoprotein mRNA expression following subsequent emamectin benzoate exposure.

PubMed

Igboeli, O O; Purcell, S L; Wotton, H; Poley, J; Burka, J F; Fast, M D

2013-03-01

Control of sea lice, Lepeophtheirus salmonis, on farmed Atlantic salmon, Salmo salar, relies heavily on chemotherapeutants. However, reduced efficacy of many treatments and need for integrated sea lice management plans require innovative strategies. Resistance to emamectin benzoate (EMB), a major sea lice parasiticide, has been linked with P-glycoprotein (P-gp) expression. We hypothesized that host immunostimulation would complement EMB treatment outcome. Lepeophtheirus salmonis-infected Atlantic salmon were fed immunostimulatory or control feeds. Sea lice were collected for 24-h EMB bioassays 1 and 2 weeks prior to commencement of EMB treatment of the fish. Two weeks after cessation of immunostimulant-treated feed, EMB was administered at 150 μg kg(-1) fish biomass for 7 days. The bioassay revealed stage, gender and immunostimulant-related differences in EMB EC(50) . Sea lice attached to salmon with a history of immunostimulation exhibited significantly greater survival than those on control feeds, despite similar levels of EMB in host tissues. Lepeophtheirus salmonis from salmon with a history of immunostimulation also exhibited higher P-gp mRNA expression as well as greater survivability compared to controls. Administration of immunostimulants prior to EMB treatment caused increased expression of P-gp mRNA which could have consequently caused decreased efficacy of the parasiticide. © 2013 Blackwell Publishing Ltd.

Individual reactions to viewing preferred video representations of the natural environment: A comparison of mental and physical reactions.

PubMed

Tsutsumi, Masae; Nogaki, Hiroshi; Shimizu, Yoshihisa; Stone, Teresa Elizabeth; Kobayashi, Toshio

2017-01-01

Globally, awareness of the vital link between health and the natural environment is growing. This pilot study, based on the idea of "forest bathing," or shinrin-yoku, the mindful use of all five senses to engage with nature in a natural environment, was initiated in order to determine whether stimulation by viewing an individual's preferred video of sea or forest had an effect on relaxation. The participants were 12 healthy men in their twenties and they were divided into two groups based on their preference for sea or forest scenery by using the Visual Analogue Scale. The participants watched 90 min DVDs of sea with natural sounds and forest with natural sounds while their heart rate variability and Bispectral Index System value were measured by using MemCalc/Tawara and a Bispectral Index System monitor. The participants were divided into two groups of six based on their preference for sea or forest scenery and each indicator was compared between them. Significant differences in a decrease in heart rate, increase in high frequency, and sustained arousal level were observed while viewing the preferred video. These results indicated that the viewing individual's preferred video of sea or forest had a relaxation effect. This study suggests that individual preferences should be taken into consideration for video relaxation therapy. © 2016 Japan Academy of Nursing Science.

Messinian deep-water turbidites and glacioeustatic sea-level changes in the North Atlantic: Linkage to the Mediterranean Salinity Crisis

NASA Astrophysics Data System (ADS)

Zhang, Jijun; Scott, David B.

1996-06-01

Our benthic foraminiferal data clearly indicate eight layers of deep-water turbidites during the Messinian (MTL 1-8) and one in the early Pliocene (PTL 1) in Ocean Drilling Program Leg 105, Site 646B. These deep-water tuibidite deposits are characterized by highly concentrated agglutinated marsh benthic foraminifera (e.g., Trochammina cf. squamata, Ammotium sp. A, Miliammina fusca), rounded quartz, polished thick-walled benthic foraminifera, wood fragments, plant seeds, plant fruit, and highly concentrated mica and are interbedded with sediments containing deep-water benthic faunas. We suggest these turbidites deposited during sea-level low stands (˜80-100 m below sea level), and their ages are tentatively correlated to 6.59, 6.22, 6.01, 5.89, 5.75, 5.7, 5.65, 5.60, and 5.55 Ma, respectively, based on the Messinian oxygen isotope enrichments at Site 552A of Deep Sea Drilling Project Leg 81. The turbidites layers during the late Messinian, coeval with frequent climate changes suggested by six oxygen enrichment excursions of Site 552A, may have been in part linked to the late Messinian evaporite deposits in the Mediterranean Basin. The most profound climate changes at 5.75 and 5.55 Ma may have been related to the Lower and Upper Evaporites in the Mediterranean Basin. An electronic supplement of this material may be obtained on adiskette or Anonymous FTP from KOSMOS .AGU.ORG, (LOGIN toAGU's FTP account using ANONYMOUS as the username and GUESTas the password. Go to the right directory by typing CD APEND. TypeLS to see what files are available. Type GET and the name of the file toget it. Finally, type EXIT to leave the system. (Paper 96PA00572,Messinian deep-water turbidites and glacioeustatic sea-level changes inthe North Atlantic: Linkage to the Mediterranean Salinity Crisis, JijunZhang and David B. Scott). Diskette may be ordered from AmericanGeophysical Union, 2000 Florida Avenue, N.W., Washington, D.C.20009; $15.00. Payment must accompany order.

Study on process design of partially-balanced, hydraulically lifting vertical ship lift

NASA Astrophysics Data System (ADS)

Xin, Shen; Xiaofeng, Xu; Lu, Zhang; Bing, Zhu; Fei, Li

2017-11-01

The hub ship lift in Panjin is the first navigation structure in China for the link between the inland and open seas, which adopts a novel partially-balanced, hydraulically lifting ship lift; it can meet such requirements as fast and sharp water level change in open sea, large draft of a yacht, and launching of a ship reception chamber; its balancing weight system can effectively reduce the load of the primary lifting cylinder, and optimize the force distribution of the ship reception chamber. The paper provides an introduction to main equipment, basic principles, main features and system composition of a ship lift. The unique power system and balancing system of the completed ship lift has offered some experience for the construction of the tourism-type ship lifts with a lower lifting height.

Annually resolved ice core records of tropical climate variability over the past ~1800 years.

PubMed

Thompson, L G; Mosley-Thompson, E; Davis, M E; Zagorodnov, V S; Howat, I M; Mikhalenko, V N; Lin, P-N

2013-05-24

Ice cores from low latitudes can provide a wealth of unique information about past climate in the tropics, but they are difficult to recover and few exist. Here, we report annually resolved ice core records from the Quelccaya ice cap (5670 meters above sea level) in Peru that extend back ~1800 years and provide a high-resolution record of climate variability there. Oxygen isotopic ratios (δ(18)O) are linked to sea surface temperatures in the tropical eastern Pacific, whereas concentrations of ammonium and nitrate document the dominant role played by the migration of the Intertropical Convergence Zone in the region of the tropical Andes. Quelccaya continues to retreat and thin. Radiocarbon dates on wetland plants exposed along its retreating margins indicate that it has not been smaller for at least six millennia.

Short Lived Climate Pollutants cause a Long Lived Effect on Sea-level Rise: Analyzing climate metrics for sea-level rise

NASA Astrophysics Data System (ADS)

Sterner, E.; Johansson, D. J.

2013-12-01

Climate change depends on the increase of several different atmospheric pollutants. While long term global warming will be determined mainly by carbon dioxide, warming in the next few decades will depend to a large extent on short lived climate pollutants (SLCP). Reducing emissions of SLCPs could contribute to lower the global mean surface temperature by 0.5 °C already by 2050 (Shindell et al. 2012). Furthermore, the warming effect of one of the most potent SLCPs, black carbon (BC), may have been underestimated in the past. Bond et al. (2013) presents a new best estimate of the total BC radiative forcing (RF) of 1.1 W/m2 (90 % uncertainty bounds of 0.17 to 2.1 W/m2) since the beginning of the industrial era. BC is however never emitted alone and cooling aerosols from the same sources offset a majority of this RF. In the wake of calls for mitigation of SLCPs it is important to study other aspects of the climate effect of SLCPs. One key impact of climate change is sea-level rise (SLR). In a recent study, the effect of SLCP mitigation scenarios on SLR is examined. Hu et al (2013) find a substantial effect on SLR from mitigating SLCPs sharply, reducing SLR by 22-42% by 2100. We choose a different approach focusing on emission pulses and analyse a metric based on sea level rise so as to further enlighten the SLR consequences of SLCPs. We want in particular to understand the time dynamics of SLR impacts caused by SLCPs compared to other greenhouse gases. The most commonly used physical based metrics are GWP and GTP. We propose and evaluate an additional metric: The global sea-level rise potential (GSP). The GSP is defined as the sea level rise after a time horizon caused by an emissions pulse of a forcer to the sea level rise after a time horizon caused by an emissions pulse of a CO2. GSP is evaluated and compared to GWP and GTP using a set of climate forcers chosen to cover the whole scale of atmospheric perturbation life times (BC, CH4, N2O, CO2 and SF6). The study utilizes an upwelling diffusion energy balance model and focuses on the thermosteric part of sea-level rise. Example GSP results are 244, 15 and 278 for BC, CH4 and N2O for a time horizon of 100 years. Compare GWP and GTP values of 405, 24 and 288 as well as 62, 4.5 and 252. The main result of the study is that no climate forcer is in any absolute sense short lived when it comes to Sea Level impacts. All of the examined climate forcers have considerable influence on the thermosteric SLR, and the closely linked ocean heat content, on the time scale of centuries. The reason for this is that heat, once it has been induced by the climate drivers and warmed the surface ocean, is transported down into the slowly mixing oceans. References: Shindell, D. et al. Simultaneously mitigating near-term climate change and improving human health and food security. Science 335, 183-189 (2012). Bond, T. C. et al. Bounding the role of black carbon in the climate system: A scientific assessment. Journal of Geophysical Research: Atmospheres 118 5380-5552 (2013). Hu, A., Xu, Y., Tebaldi, C., Washington, W. M. & Ramanathan, V. Mitigation of short-lived climate pollutants slows sea-level rise. Nature Climate Change 3, 730-734 (2013).

North Atlantic teleconnection patterns signature on sea level from satellite altimetry

NASA Astrophysics Data System (ADS)

Iglesias, Isabel; Lázaro, Clara; Joana Fernandes, M.; Bastos, Luísa

2015-04-01

Presently, satellite altimetry record is long enough to appropriately study inter-annual signals in sea level anomaly and ocean surface circulation, allowing the association of teleconnection patterns of low-frequency variability with the response of sea level. The variability of the Atlantic Ocean at basin-scale is known to be complex in space and time, with the dominant mode occurring on annual timescales. However, interannual and decadal variability have already been documented in sea surface temperature. Both modes are believed to be linked and are known to influence sea level along coastal regions. The analysis of the sea level multiannual variability is thus essential to understand the present climate and its long-term variability. While in the open-ocean sea level anomaly from satellite altimetry currently possesses centimetre-level accuracy, satellite altimetry measurements become invalid or of lower accuracy along the coast due to the invalidity of the wet tropospheric correction (WTC) derived from on-board microwave radiometers. In order to adequately analyse long-term changes in sea level in the coastal regions, satellite altimetry measurements can be recovered by using an improved WTC computed from recent algorithms that combine wet path delays from all available observations (remote sensing scanning imaging radiometers, GNSS stations, microwave radiometers on-board satellite altimetry missions and numerical weather models). In this study, a 20-year (1993-2013) time series of multi-mission satellite altimetry (TOPEX/Poseidon, Jason-1, OSTM/Jason-2, ERS-1/2, ENVISAT, CryoSat-2 and SARAL), are used to characterize the North Atlantic (NA) long-term variability on sea level at basin-scale and analyse its response to several atmospheric teleconnections known to operate on the NA. The altimetry record was generated using an improved coastal WTC computed from either the GNSS-derived path Delay or the Data Combination methodologies developed by University of Porto (Fernandes et al., 2010; Fernandes et al., 2013). Regular 0.25°x0.25° latitude-longitude grids were generated at a 10-day interval for the NA Ocean (60°W-5°W, 5°N-60°N) using optimal interpolation with a realistic space-time correlation function (Lázaro et al., 2013). These grids are used to inspect the response of sea level anomalies to several teleconnection patterns as well as the NA variability on annual and longer timescales. The teleconnection patterns selected are the ones that have influence on the NA basin: North Atlantic Oscillation, East Atlantic pattern, East Atlantic/Western Russia pattern, Scandinavia pattern, Western Mediterranean Oscillation index, El Niño Southern Oscillation, Tropical North Atlantic Index, and Atlantic Multidecadal Oscillation. Acknowledgments: RAIA tec (0688-RAIATEC-1-P) project. The RAIA Coastal Observatory has been funded by the Programa Operativo de Cooperación Transfronteriza España-Portugal (POCTEP 2007-2013). References: Fernandes M.J., C. Lázaro, A.L. Nunes, N. Pires, L. Bastos, V.B. Mendes (2010). GNSS-derived Path Delay: an approach to compute the wet tropospheric correction for coastal altimetry. IEEE Geosci. Rem. Sens Lett., Vol. 7, NO. 3, 596 - 600, doi: 10.1109/LGRS.2010.2042425. Lázaro, C., M. J. Juliano, M. J. Fernandes (2013): Semi-automatic determination of the Azores Current axis using satellite altimetry: application to the study of the current variability during 1995-2006. Advances in Space Research, Vol. 51(11), pp. 2155-2170, doi:10.1016/j.asr.2012.12.021. Fernandes, M. J., A.L. Nunes, C. Lázaro (2013). Analysis and Inter-Calibration of Wet Path Delay Datasets to Compute the Wet Tropospheric Correction for CryoSat-2 over Ocean. Remote Sensing, 5, 4977-5005.

Integrating Thematic Web Portal Capabilities into the NASA Earthdata Web Infrastructure

NASA Technical Reports Server (NTRS)

Wong, Minnie; Baynes, Kathleen E.; Huang, Thomas; McLaughlin, Brett

2015-01-01

This poster will present the process of integrating thematic web portal capabilities into the NASA Earth data web infrastructure, with examples from the Sea Level Change Portal. The Sea Level Change Portal will be a source of current NASA research, data and information regarding sea level change. The portal will provide sea level change information through articles, graphics, videos and animations, an interactive tool to view and access sea level change data and a dashboard showing sea level change indicators.

A new Arctic 25-year Altimetric Sea-level Record (1992-2016) and Initial look at Arctic Sea Level Budget Closure

NASA Astrophysics Data System (ADS)

Andersen, O. B.; Passaro, M.; Benveniste, J.; Piccioni, G.

2016-12-01

A new initiative within the ESA Sea Level Climate Change initiative (SL-cci) framework to improve the Arctic sea level record has been initiated as a combined effort to reprocess and retrack past altimetry to create a 25-year combined sea level record for sea level research studies. One of the objectives is to retracked ERS-2 dataset for the high latitudes based on the ALES retracking algorithm through adapting the ALES retracker for retracking of specular surfaces (leads). Secondly a reprocessing using tailored editing to Arctic Conditions will be carried out also focusing on the merging of the multi-mission data. Finally an effort is to combine physical and empirical retracked sea surface height information to derive an experimental spatio-temporal enhanced sea level product for high latitude. The first results in analysing Arctic Sea level variations on annual inter-annual scales for the 1992-2015 from a preliminar version of this dataset is presented. By including the GRACE water storage estimates and NOAA halo- and thermo-steric sea level variatios since 2002 a preliminary attempt to close the Arctic Sea level budget is presented here. Closing the Arctic sea level budget is by no mean trivial as both steric data and satellite altimetry is both sparse temporally and limited geographically.

The lactate paradox revisited in lowlanders during acclimatization to 4100 m and in high-altitude natives

PubMed Central

van Hall, G; Lundby, C; Araoz, M; Calbet, J A L; Sander, M; Saltin, B

2009-01-01

Chronic hypoxia has been proposed to induce a closer coupling in human skeletal muscle between ATP utilization and production in both lowlanders (LN) acclimatizing to high altitude and high-altitude natives (HAN), linked with an improved match between pyruvate availability and its use in mitochondrial respiration. This should result in less lactate being formed during exercise in spite of the hypoxaemia. To test this hypothesis six LN (22–31 years old) were studied during 15 min warm up followed by an incremental bicycle exercise to exhaustion at sea level, during acute hypoxia and after 2 and 8 weeks at 4100 m above sea level (El Alto, Bolivia). In addition, eight HAN (26–37 years old) were studied with a similar exercise protocol at altitude. The leg net lactate release, and the arterial and muscle lactate concentrations were elevated during the exercise in LN in acute hypoxia and remained at this higher level during the acclimatization period. HAN had similar high values; however, at the moment of exhaustion their muscle lactate, ADP and IMP content and Cr/PCr ratio were higher than in LN. In conclusion, sea-level residents in the course of acclimatization to high altitude did not exhibit a reduced capacity for the active muscle to produce lactate. Thus, the lactate paradox concept could not be demonstrated. High-altitude natives from the Andes actually exhibit a higher anaerobic energy production than lowlanders after 8 weeks of acclimatization reflected by an increased muscle lactate accumulation and enhanced adenine nucleotide breakdown. PMID:19139048

The complex reality of sea-level rise in an atoll nation

NASA Astrophysics Data System (ADS)

Donner, S. D.

2012-12-01

Sea-level rise famously poses an existential threat to island nations like Kiribati, Tuvalu and the Maldives. Yet as the global mean sea-level rises, the response of any one location at any given time will depend on the natural variability in regional sea-level and other impact of local human activities on coastal processes. As with climate warming, the state of an individual shoreline or the extent of flooding on a given day is not proof of a sea-level trend, nor is a global sea-level trend a good predictor of individual flooding or erosion events. Failure to consider the effect of natural variability and local human activity on coastal processes often leads to misattribution of flooding events and even some long-term shoreline changes to global sea level rise. Moreover, unverified attribution of individual events or changes to specific islets to sea level rise can inflame or invite scepticism of the strong scientific evidence for an accelerating increase in the global sea level due to the impacts of human activity on the climate system. This is particularly important in developing nations like Kiribati, which are depending on international financial support to adapt to rising sea levels. In this presentation, I use gauge data and examples from seven years of field work in Tarawa Atoll, the densely populated capital of Kiribati, to examine the complexity of local sea level and shoreline change in one of the world's most vulnerable countries. First, I discuss how the combination of El Nino-driven variability in sea-level and the astronomical tidal cycle leads to flooding and erosion events which can be mistaken for evidence of sea-level rise. Second, I show that human modification to shorelines has redirected sediment supply, leading, in some cases, to expansion of islets despite rising sea levels. Taken together, the analysis demonstrates the challenge of attributing particular coastal events to global mean sea-level rise and the impact on decision-making. The presentation concludes with a discussion of the implications for attribution research, discourse about sea-level rise, and adaptation planning.

Multi-linear regression of sea level in the south west Pacific as a first step towards local sea level projections

NASA Astrophysics Data System (ADS)

Kumar, Vandhna; Meyssignac, Benoit; Melet, Angélique; Ganachaud, Alexandre

2017-04-01

Rising sea levels are a critical concern in small island nations. The problem is especially serious in the western south Pacific, where the total sea level rise over the last 60 years is up to 3 times the global average. In this study, we attempt to reconstruct sea levels at selected sites in the region (Suva, Lautoka, Noumea - Fiji and New Caledonia) as a mutiple-linear regression of atmospheric and oceanic variables. We focus on interannual-to-decadal scale variability, and lower (including the global mean sea level rise) over the 1979-2014 period. Sea levels are taken from tide gauge records and the ORAS4 reanalysis dataset, and are expressed as a sum of steric and mass changes as a preliminary step. The key development in our methodology is using leading wind stress curl as a proxy for the thermosteric component. This is based on the knowledge that wind stress curl anomalies can modulate the thermocline depth and resultant sea levels via Rossby wave propagation. The analysis is primarily based on correlation between local sea level and selected predictors, the dominant one being wind stress curl. In the first step, proxy boxes for wind stress curl are determined via regions of highest correlation. The proportion of sea level explained via linear regression is then removed, leaving a residual. This residual is then correlated with other locally acting potential predictors: halosteric sea level, the zonal and meridional wind stress components, and sea surface temperature. The statistically significant predictors are used in a multi-linear regression function to simulate the observed sea level. The method is able to reproduce between 40 to 80% of the variance in observed sea level. Based on the skill of the model, it has high potential in sea level projection and downscaling studies.

Rapid climatic signal propagation from source to sink in a southern California sediment-routing system

USGS Publications Warehouse

Covault, J.A.; Romans, B.W.; Fildani, A.; McGann, M.; Graham, S.A.

2010-01-01

Terrestrial source areas are linked to deep-sea basins by sediment-routing systems, which only recently have been studied with a holistic approach focused on terrestrial and submarine components and their interactions. Here we compare an extensive piston-core and radiocarbon-age data set from offshore southern California to contemporaneous Holocene climate proxies in order to test the hypothesis that climatic signals are rapidly propagated from source to sink in a spatially restricted sediment-routing system that includes the Santa Ana River drainage basin and the Newport deep-sea depositional system. Sediment cores demonstrate that variability in rates of Holocene deep-sea turbidite deposition is related to complex ocean-atmosphere interactions, including enhanced magnitude and frequency of the North American monsoon and El Ni??o-Southern Oscillation cycles, which increased precipitation and fluvial discharge in southern California. This relationship is evident because, unlike many sediment-routing systems, the Newport submarine canyon-and-channel system was consistently linked tothe Santa Ana River,which maintained sediment delivery even during Holocene marine transgression and highstand. Results of this study demonstrate the efficiency of sediment transport and delivery through a spatially restricted, consistently linked routing system and the potential utility of deep-sea turbidite depositional trends as paleoclimate proxies in such settings. ?? 2010 by The University of Chicago.

The Adriatic Sea: A Long-Standing Laboratory for Sea Level Studies

NASA Astrophysics Data System (ADS)

Vilibić, Ivica; Šepić, Jadranka; Pasarić, Mira; Orlić, Mirko

2017-10-01

The paper provides a comprehensive review of all aspects of Adriatic Sea level research covered by the literature. It discusses changes occurring over millennial timescales and documented by a variety of natural and man-made proxies and post-glacial rebound models; mean sea level changes occurring over centennial to annual timescales and measured by modern instruments; and daily and higher-frequency changes (with periods ranging from minutes to a day) that are contributing to sea level extremes and are relevant for present-day flooding of coastal areas. Special tribute is paid to the historic sea level studies that shaped modern sea level research in the Adriatic, followed by a discussion of existing in situ and remote sensing observing systems operating in the Adriatic area, operational forecasting systems for Adriatic storm surges, as well as warning systems for tsunamis and meteotsunamis. Projections and predictions of sea level and related hazards are also included in the review. Based on this review, open issues and research gaps in the Adriatic Sea level studies are identified, as well as the additional research efforts needed to fill the gaps. The Adriatic Sea, thus, remains a laboratory for coastal sea level studies for semi-enclosed, coastal and marginal seas in the world ocean.

The Bering Sea Project Archive: a Prototype for Improved Discovery and Access

NASA Astrophysics Data System (ADS)

Stott, D.; Mayernik, M. S.; Daniels, M. D.; Moore, J. A.; Williams, S. F.; Allison, J.

2015-12-01

The Bering Sea Project was a research program from 2007 through 2012 that sought to understand the impacts of climate change and dynamic sea ice cover on the eastern Bering Sea ecosystem. More than 100 scientists engaged in field data collection, original research, and ecosystem modeling to link climate, physical oceanography, plankton, fishes, seabirds, marine mammals, humans, traditional knowledge and economic outcomes. Over the six-year period of the program hundreds of multidisciplinary datasets coming from a variety of instrumentation and measurement platforms within thirty-one categories of research were processed and curated by the National Center for Atmospheric Research (NCAR) Earth Observing Laboratory (EOL). For the investigator proposing a field project, the researcher performing synthesis, or the modeler seeking data for verification, the easy discovery and access to the most relevant data is of prime importance. The heterogeneous products of oceanographic field programs such as the Bering Sea Project challenge the ability of researchers to identify which data sets, people, or tools might be relevant to their research, and to understand how certain data, instruments, or methods were used to produce particular results.EOL, as a partner in the NSF funded EarthCollab project, is using linked open data to permit the direct interlinking of information and data across platforms and projects. We are leveraging an existing open-source semantic web application, VIVO, to address connectivity gaps across distributed networks of researchers and resources and identify relevant content, independent of location. We will present our approach in connecting ontologies and integrating them within the VIVO system, using the Bering Sea Project datasets as a case study, and will provide insight into how the geosciences can leverage linked data to produce more coherent methods of information and data discovery across large multi-disciplinary projects.

The impact of half-a-degree Celsius upon the spatial pattern of future sea-level change.

NASA Astrophysics Data System (ADS)

Jackson, Luke

2017-04-01

It has been shown that the global thermal expansion of sea level and ocean dynamics are linearly related to global temperature change. On this basis one can estimate the difference in local sea-level change between a 1.5°C and 2.0°C world. The mitigation scenario RCP 2.6 shows an end-of-century global temperature range of 0.9 to 2.3°C (median 1.6°C). Additional sea-level components, such as mass changes in ice sheets, glaciers and land-water storage have unique spatial patterns that contribute to sea-level change and will be indirectly affected by global temperature change. We project local sea-level change for RCP 2.6 using sub-sets of models in the CMIP5 archive that follow different global temperature pathways. The method used to calculate local sea-level change is probabilistic and combines the normalised spatial patterns of sea-level components with global average projections of individual sea-level components.

Sea-level rise caused by climate change and its implications for society

PubMed Central

MIMURA, Nobuo

2013-01-01

Sea-level rise is a major effect of climate change. It has drawn international attention, because higher sea levels in the future would cause serious impacts in various parts of the world. There are questions associated with sea-level rise which science needs to answer. To what extent did climate change contribute to sea-level rise in the past? How much will global mean sea level increase in the future? How serious are the impacts of the anticipated sea-level rise likely to be, and can human society respond to them? This paper aims to answer these questions through a comprehensive review of the relevant literature. First, the present status of observed sea-level rise, analyses of its causes, and future projections are summarized. Then the impacts are examined along with other consequences of climate change, from both global and Japanese perspectives. Finally, responses to adverse impacts will be discussed in order to clarify the implications of the sea-level rise issue for human society. PMID:23883609

Incorporating Sediment Compaction Into a Gravitationally Self-consistent Model for Global Sea-level Change

NASA Astrophysics Data System (ADS)

Ferrier, K.; Mitrovica, J. X.

2015-12-01

In sedimentary deltas and fans, sea-level changes are strongly modulated by the deposition and compaction of marine sediment. The deposition of sediment and incorporation of water into the sedimentary pore space reduces sea level by increasing the elevation of the seafloor, which reduces the thickness of sea-water above the bed. In a similar manner, the compaction of sediment and purging of water out of the sedimentary pore space increases sea level by reducing the elevation of the seafloor, which increases the thickness of sea water above the bed. Here we show how one can incorporate the effects of sediment deposition and compaction into the global, gravitationally self-consistent sea-level model of Dalca et al. (2013). Incorporating sediment compaction requires accounting for only one additional quantity that had not been accounted for in Dalca et al. (2013): the mean porosity in the sediment column. We provide a general analytic framework for global sea-level changes including sediment deposition and compaction, and we demonstrate how sea level responds to deposition and compaction under one simple parameterization for compaction. The compaction of sediment generates changes in sea level only by changing the elevation of the seafloor. That is, sediment compaction does not affect the mass load on the crust, and therefore does not generate perturbations in crustal elevation or the gravity field that would further perturb sea level. These results have implications for understanding sedimentary effects on sea-level changes and thus for disentangling the various drivers of sea-level change. ReferencesDalca A.V., Ferrier K.L., Mitrovica J.X., Perron J.T., Milne G.A., Creveling J.R., 2013. On postglacial sea level - III. Incorporating sediment redistribution. Geophysical Journal International, doi: 10.1093/gji/ggt089.

Reef productivity and preservation during the Late Neogene

NASA Astrophysics Data System (ADS)

Husson, Laurent; Pastier, Anne-Morwenn; Schmitt, Anais; Sarr, Anta-Clarisse; Elliot, Mary; Pedoja, Kevin; Bezos, Antoine

2016-04-01

During the glacial-interglacials cycles that prevailed during Plio-Pleistocence times, the pace of sea level oscillations exerts a major control on coral reef growth and expansion. We designed a numerical model to quantify reef productivity and carbonate preservation that accounts for sea level oscillations, reef growth, erosion and subsequent geomorphological carving. We carried out a parametric study of a variety of processes (reef growth, erosion, local slope, uplift and subsidence, relative sea level, etc) towards a probabilistic analysis of reef productivity and carbonate production. We further test the effect of the frequency and amplitude of sea level oscillations using sea level curves derived from both the 18O isotope record of past sea level change and synthetic sinusoidal sea level curves. Over a typical climate cycle, our model simulations confirm that the rate of sea level change is the primary controlling factor of reef production, as it modifies the productivity by several orders of magnitude. Most importantly, reef productivity increases during periods of sea level rise, and decreases during sea level stands, while conversely, the morphology records the opposite in a misleading fashion: Reef terraces expand during sea level stands due to the joint effects of erosion and patient reef growth at a stationary level until the accommodation space is filled up. On the long-term, over the Plio-Pleistocene period, vertical ground motion also significantly alters the production: moderate uplift or subsidence can boost reef productivity up to tenfold with respect to a stationary coastline. Last, the amplitude and frequency of the sea level oscillations (typically 40 kyrs vs. 100 kyrs periods) moderately impact reef productivity. These results can be ultimately converted into estimates of carbonate production and carbon sequestration during the Late Neogene, provided relative sea level is documented in the tectonically agitated intertropical zone.

Response of Cenozoic turbidite system to tectonic activity and sea-level change off the Zambezi Delta

NASA Astrophysics Data System (ADS)

Castelino, Jude A.; Reichert, Christian; Jokat, Wilfried

2017-09-01

Submarine fans and turbidite systems are important and sensitive features located offshore from river deltas that archive tectonic events, regional climate, sea level variations and erosional process. Very little is known about the sedimentary structure of the 1800 km long and 400 km wide Mozambique Fan, which is fed by the Zambezi and spreads out into the Mozambique Channel. New multichannel seismic profiles in the Mozambique Basin reveal multiple feeder systems of the upper fan that have been active concurrently or consecutively since Late Cretaceous. We identify two buried, ancient turbidite systems off Mozambique in addition to the previously known Zambezi-Channel system and another hypothesized active system. The oldest part of the upper fan, located north of the present-day mouth of the Zambezi, was active from Late Cretaceous to Eocene times. Regional uplift caused an increased sediment flux that continued until Eocene times, allowing the fan to migrate southwards under the influence of bottom currents. Following the mid-Oligocene marine regression, the Beira High Channel-levee complex fed the Mozambique Fan from the southwest until Miocene times, reworking sediments from the shelf and continental slope into the distal abyssal fan. Since the Miocene, sediments have bypassed the shelf and upper fan region through the Zambezi Valley system directly into the Zambezi Channel. The morphology of the turbidite system off Mozambique is strongly linked to onshore tectonic events and the variations in sea level and sediment flux.

Climatic-eustatic control of Holocene nearshore parasequence development, southeastern Texas coast

USGS Publications Warehouse

Morton, Robert A.; Kindinger, Jack G.; Flocks, James G.; Stewart, Laura B.

1999-01-01

Sediment cores, seismic profiles, radiocarbon dates, and faunal assemblages were used to interpret the depositional setting and geological evolution of the southeastern Texas coast during the last glacio-eustatic cycle. Discrete lithofacies and biofacies zones in the ebb-dominated Sabine Lake estuary and adjacent chenier plain record alternating periods of rapid marine flooding and gradual shoaling related to linked climatic/eustatic fluctuations. Monospecific zones of the mollusks Rangia cuneata and Crassostrea virginica, respectively, indicate high fresh water outflow followed by invasion of marine water, whereas intervening organic-rich zones record bayhead delta deposition. High-frequency parasequence stacking patterns within the valley fill and across the adjacent interfluve reflect an initial rapid rise in sea level about 9 ka that flooded abandoned alluvial terraces and caused onlap of Holocene marsh in the incised valley. The rapid rise was followed by slowly rising and oscillating sea level that filled the deepest portions of the incised valleys with fluvially dominated estuarine deposits, and then a maximum highstand (+1 m msl) about 5 ka that flooded the former subaerial coastal plain between the incised valleys and constructed the highest beach ridges. Between 3.5 and 1.5 ka, sea level oscillated and gradually fell, causing a forced regression and rapid progradation of both the chenier plain and accretionary barrier islands. The only significant sands in the valley fill are (1) falling-stage and lowstand-fluvial sediments between the basal sequence boundary and transgressive surface unconformity, and (2) highstand beach-ridge sediments of the chenier plain.

First echinoderm trehalase from a tropical sea cucumber (Holothuria leucospilota): Molecular cloning and mRNA expression in different tissues, embryonic and larval stages, and under a starvation challenge.

PubMed

Huo, Da; Jiang, Xiao; Wu, Xiaofen; Ren, Chunhua; Yu, Zonghe; Liu, Jinshang; Li, Hongmei; Ruan, Yao; Wen, Jin; Chen, Ting; Hu, Chaoqun

2018-04-29

Trehalases are a group of enzymes that catalyse the conversion of trehalose to glucose, and they are observed in most organisms. In this study, the first echinoderm trehalase, designated Hl-Tre, was identified from a tropical sea cucumber, Holothuria leucospilota. The full-length cDNA of H. leucospilota trehalase (Hl-Tre) is 2461 bp in length with an open reading frame (ORF) of 1788 bp that encodes a 595-amino-acid protein with a deduced molecular weight of 67.95 KDa. The Hl-Tre protein contains a signal peptide at the N-terminal and a functional trehalase domain, which includes the signature motifs 1 and 2. The mRNA expression of Hl-Tre was ubiquitously detected in all selected tissues, with the highest level being detected in the intestine. By in situ hybridization (ISH), the positive Hl-Tre signals were observed in the brush borders of the intestinal mucosa. In embryonic and larval stages, the transcript levels of Hl-Tre decreased during embryonic development and increased after the pentactula stage. After a challenge of starvation, the intestinal Hl-Tre mRNA levels were observed to be first decreased and partially recovered thereafter. Overall, our study provided the first evidence for trehalase in echinoderms and showed that this enzyme was potentially linked to a trehalose metabolic pathway in sea cucumbers. Copyright © 2017. Published by Elsevier B.V.

A near uniform basin-wide sea level fluctuation over the Japan/East Sea: A semienclosed sea with multiple straits

NASA Astrophysics Data System (ADS)

Kim, Seung-Bum; Fukumori, Ichiro

2008-06-01

Sea level of the Japan/East Sea observed by the TOPEX/Poseidon (T/P) satellite altimeter is analyzed using a 1/4°-resolution ocean general circulation model. A significant fraction of the Japan/East Sea sea level variability is found to be spatially uniform with periods ranging from 20 d to a year. The model simulation is consistent with T/P records in terms of the basin-wide sea level fluctuation's spectral energy and coherence. The simulation indicates that the changes are barotropic in nature and controlled, notably at high frequencies, by the net mass transport through the straits of the Japan/East Sea driven by winds in the vicinity of the Korea/Tsushima and Soya Straits. A series of barotropic simulations suggest that the sea level fluctuations are the result of a dynamic balance at the straits among near-strait winds, friction, and geostrophic control. The basin-wide sea level response is a linear superposition of changes due to winds near the individual straits. In particular, a basin-wide sea level response can be established by winds near either one of the straits alone. For the specific geometry and winds, winds near the Soya Strait have a larger impact on the Japan/East Sea mean sea level than those near the Korea/Tsushima Strait.

Sea Level Trend and Variability in the Straits of Singapore and Malacca

NASA Astrophysics Data System (ADS)

Luu, Q.; Tkalich, P.

2013-12-01

The Straits of Singapore and Malacca (SSM) connect the Andaman Sea located northeast of the Indian Ocean to the South China Sea, the largest marginal sea situated in the tropical Pacific Ocean. Consequently, sea level in the SSM is assumed to be governed by various regional phenomena associated with the adjacent parts of Indian and Pacific Oceans. At annual scale sea level variability is dominant by the Asian monsoon. Interannual sea level signals are modulated by the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). In the long term, regional sea level is driven by the global climate change. However, relative impacts of these multi-scale phenomena on regional sea level in the SSM are yet to be quantified. In present study, publicly available tide gauge records and satellite altimetry data are used to derive long-term sea level trend and variability in SSM. We used the data from research-quality stations, including four located in the Singapore Strait (Tanjong Pagar, Raffles Lighthouse, Sultan Shoal and Sembawang) and seven situated in the Malacca Strait (Kelang, Keling, Kukup, Langkawji, Lumut, Penang and Ko Taphao Noi), each one having 25-39 year data up to the year 2011. Harmonic analysis is performed to filter out astronomic tides from the tide gauge records when necessary; and missing data are reconstructed using identified relationships between sea level and the governing phenomena. The obtained sea level anomalies (SLAs) and reconstructed mean sea level are then validated against satellite altimetry data from AVISO. At multi-decadal scale, annual measured sea level in the SSM is varying with global mean sea level, rising for the period 1984-2009 at the rate 1.8-2.3 mm/year in the Singapore Strait and 1.1-2.8 mm/year in the Malacca Strait. Interannual regional sea level drops are associated with El Niño events, while the rises are correlated with La Niña episodes; both variations are in the range of ×5 cm with correlation coefficient of -0.7 (in correspondence with the Multivariate ENSO Index). The IOD modulates interannual sea level variability only in the Malacca Strait in the range of ×3 cm with a correlation coefficient of -0.6 (with respect to the Dipole Mode Index). At annual scale, SLAs in the SSM are mainly monsoon-driven; of the order of 20 cm. Mean sea level in the Singapore Strait reach the peak during northeast monsoon and trough during southwest monsoon; while these in the Malacca Strait are highest at middle of both monsoons and lowest during their transitional monsoonal seasons. Global and regional signals are quantitatively captured in the SSM. In comparison with the global sea level trends, SSM sea level rise are larger for recent decades 1984-2009. Taking into account the rough estimate of land subsidence rates in Singapore (2006-2011) and Peninsular Malaysia (1994-2004), the trend of absolute sea level rise in SSM follows regional tendency. At interannual scale, ENSO modulates sea level variabilities in the entire SSM region, while IOD affects the Malacca Strait only. At annual scale, sea level responds differently to the Asian monsoon: quasi-periodic cycles are observed twice a year in the Malacca Strait, but once a year in the Singapore Strait. Such behavior implies that the narrow channel constriction between the Singapore and Malacca Straits may be a reason of different variability of sea level in the domains.

Peat Archives in the Hudson River Estuary… Marsh Formation, Carbon Storage and Release, and Resilience

NASA Astrophysics Data System (ADS)

Peteet, D. M.; Corbett, E. J.; Nichols, J. E.; Kenna, T. C.; Chang, C.

2017-12-01

We target deep peat stores (at least 8 meters) of carbon in the lower Hudson Estuary, which formed as the glacial fjord became an estuary with mid-Holocene sea level rise. These deep marshes play an extremely important role in the estuary health and stability in a changing climate. Never before have we faced the threats to coastal marshes that we are facing today, and the resulting sedimentation rates, inorganic/organic component histories, pollen, macrofossil, isotopic, and XRF data reveal critical information about past vegetation and climate change. Long-term shifts in organic/inorganic storage appear to be linked to drought, as watershed erosion results in more sand, silt and clay in the marshes. Climatic shifts often result in regional watershed shifts in vegetation, both locally and regionally. Understanding how these marshes are linked to human impact (disturbance, invasive species, higher nitrogen, heavy metal pollution, dams) over the last four centuries is critical to providing management of these key ecosystems, and their preservation as sea level rises. Quantification of processes that cause carbon degradation and release from these wetlands to the estuary is also key to this investigation. Peat loss would contribute to heavy metal pollution in the estuary as well as carbon loss. Young investigators from secondary schools in New York City participated in much of the fieldwork as part of the NASA/GISS NYC Research Initiative and the LDEO Secondary School Field Research Carbon Team.

The flooding of the San Matías Gulf: The Northern Patagonia sea-level curve

NASA Astrophysics Data System (ADS)

Isla, Federico Ignacio

2013-12-01

Northern Patagonia is characterised by tectonic depressions below present sea level. Some of them are today flooded by the sea; others remain emerged although they are at altitudes of - 50 m (Bajo del Gualicho), - 35 m (Salinas Grandes) and - 7 m (Salina La Piedra). San Matías Gulf also was such an emerged depression below contemporary mean sea level during the Late Pleistocene. It flooded between 11,500 and 11,000 years ago, when the sea level surpassed the sill of the gulf (today 50 m below mean sea level) during postglacial sea-level rise. In those days, shrublands extended on the slopes of the tectonic depression. In-situ pieces of woods dredged from the bottom of the gulf at depths of 70 m gave a conventional age of 11,310 ± 150 years BP. We used the wood, together with dated shells from the continental shelf, and shells and organic matter dated from the San Blas, Negro and Chubut coastal plains to construct a sea-level curve. Sea level rise surpassed the present level somewhat before 6000 years BP, reaching a maximum stand of + 6 m. It has since gently diminished towards present sea level.

Ice Age Sea Level Change on a Dynamic Earth

NASA Astrophysics Data System (ADS)

Austermann, J.; Mitrovica, J. X.; Latychev, K.; Rovere, A.; Moucha, R.

2014-12-01

Changes in global mean sea level (GMSL) are a sensitive indicator of climate variability during the current ice age. Reconstructions are largely based on local sea level records, and the mapping to GMSL is computed from simulations of glacial isostatic adjustment (GIA) on 1-D Earth models. We argue, using two case studies, that resolving important, outstanding issues in ice age paleoclimate requires a more sophisticated consideration of mantle structure and dynamics. First, we consider the coral record from Barbados, which is widely used to constrain global ice volume changes since the Last Glacial Maximum (LGM, ~21 ka). Analyses of the record using 1-D viscoelastic Earth models have estimated a GMSL change since LGM of ~120 m, a value at odds with analyses of other far field records, which range from 130-135 m. We revisit the Barbados case using a GIA model that includes laterally varying Earth structure (Austermann et al., Nature Geo., 2013) and demonstrate that neglecting this structure, in particular the high-viscosity slab in the mantle linked to the subduction of the South American plate, has biased (low) previous estimates of GMSL change since LGM by ~10 m. Our analysis brings the Barbados estimate into accord with studies from other far-field sites. Second, we revisit estimates of GMSL during the mid-Pliocene warm period (MPWP, ~3 Ma), which was characterized by temperatures 2-3°C higher than present. The ice volume deficit during this period is a source of contention, with estimates ranging from 0-40 m GMSL equivalent. We argue that refining estimates of ice volume during MPWP requires a correction for mantle flow induced dynamic topography (DT; Rowley et al., Science, 2013), a signal neglected in previous studies of ice age sea level change. We present estimates of GIA- and DT-corrected elevations of MPWP shorelines from the U.S. east coast, Australia and South Africa in an attempt to reconcile these records with a single GMSL value.

Comparing salt tolerance of beet cultivars and their halophytic ancestor: consequences of domestication and breeding programmes

PubMed Central

Rozema, Jelte; Cornelisse, Danny; Zhang, Yuancheng; Li, Hongxiu; Bruning, Bas; Katschnig, Diana; Broekman, Rob; Ji, Bin; van Bodegom, Peter

2015-01-01

Salt tolerance of higher plants is determined by a complex set of traits, the timing and rate of evolution of which are largely unknown. We compared the salt tolerance of cultivars of sugar beet and their ancestor, sea beet, in hydroponic studies and evaluated whether traditional domestication and more recent breeding have changed salt tolerance of the cultivars relative to their ancestor. Our comparison of salt tolerance of crop cultivars is based on values of the relative growth rate (RGR) of the entire plant at various salinity levels. We found considerable salt tolerance of the sea beet and slightly, but significantly, reduced salt tolerance of the sugar beet cultivars. This indicates that traditional domestication by selection for morphological traits such as leaf size, beet shape and size, enhanced productivity, sugar content and palatability slightly affected salt tolerance of sugar beet cultivars. Salt tolerance among four sugar beet cultivars, three of which have been claimed to be salt tolerant, did not differ. We analysed the components of RGR to understand the mechanism of salt tolerance at the whole-plant level. The growth rate reduction at higher salinity was linked with reduced leaf area at the whole-plant level (leaf area ratio) and at the individual leaf level (specific leaf area). The leaf weight fraction was not affected by increased salinity. On the other hand, succulence and leaf thickness and the net assimilation per unit of leaf area (unit leaf rate) increased in response to salt treatment, thus partially counteracting reduced capture of light by lower leaf area. This compensatory mechanism may form part of the salt tolerance mechanism of sea beet and the four studied sugar beet cultivars. Together, our results indicate that domestication of the halophytic ancestor sea beet slightly reduced salt tolerance and that breeding for improved salt tolerance of sugar beet cultivars has not been effective. PMID:25492122

Predicting relative sea level changes at the aftermath of Marinoan (635 Ma) Snowball meltdown

NASA Astrophysics Data System (ADS)

Irie, Y.; Nakada, M.; Okuno, J.; Bao, H.

2016-12-01

Earth system recovery from a Snowball state constitutes one of the best tests of the resilience of life on planet Earth. A distinct and probably brief relative sea level (RSL) drop has been identified in the cap dolostones deposited in a general transgression sequence at the aftermath of Marinoan Snowball meltdown in South China and other late Neoproterozoic blocks. However, the magnitude and duration or the very existence of this RSL drop event can vary at different geographical sites because of spatial and temporal variations in sea level due to glacial isostatic adjustment (GIA) even for tectonically stable areas. An accurate prediction of this drop can in turn help us infer independently the rate of dynamic recovery of the Earth system from a Snowball state, e.g. the timing and duration of the Marinoan 17O depletion (MOSD) event that was also closely linked to the rise and drawdown of atmospheric O2 and CO2, respectively. Here we model the RSL changes by considering all GIA-related relaxation processes. We evaluated the RSL to the sea level at 10 Myr after the complete glacial meltdown and tested slightly different paleogeographic configurations. Our modeling results show that the RSL drop occurs in the syn-deglacial phase (melting phase) for the inland regions and in the post-deglacial phase (time after the complete melting) for continental margins. The RSL drop in the post-deglacial phase is mainly determined by the relaxation processes with a timescale of longer than 20 kyr. The predicted RSL change in South China for lower mantle viscosity of 1022-1023 Pa s and a syn-deglacial time of <100 kyr is consistent with the observationally inferred RSL change regardless of uncertainties on the length of the continental shelf or the paleogeography of South China. A comparison between our model predicted and sedimentary-record inferred RSL change in South China put an independent constraint on the duration of the MOSD event at 70 kyr or shorter.

Land-Sea Correlation of Holocene Records in NW Iberian Peninsula

NASA Astrophysics Data System (ADS)

Gonzalez-Alvare, R.; Costas, S.; Bernardez, P.; Frances, G.; Alejo, I.

2005-12-01

Holocene climate fluctuations in the temperate region of the Northeast Atlantic have been established by comparing marine and terrestrial proxies. This work is based on suction-cores collected in the Cies Islands lagoon (NW Spain) and vibro-cores from the adjacent continental shelf. The lower Holocene marine record (9400-7000 yr BP) consists on sandy transgressive facies overlying fluvial Pleistocene deposits. During this time the continental shelf was dominated by high energy processes linked to the progressive and fast sea level rise. The rate of sea level rise sharply decelerated at 7000 yr BP and a high productive marine environment was fully established, as revealed by planktonic foraminifera assemblages and biogeochemical markers. In the terrestrial areas, peat deposits were formed beginning around 6000 yr BP in the deeper parts of the paleo-relief that was developed above the granitic basement. The peat was deposited in a fresh-water shallow coastal lake under warm and humid conditions that are brought about by prevailing SW winds. From 4800 yr BP, a progressive rainfall decrease provoked the lowering of the lake level and a weaker fluvial influence on the adjacent shelf. The prevailing eastern winds caused significantly drier conditions between 4000 and 3200 yr BP. During this period the coastal lake dried and the peat layer was covered by aeolian deposits. At the continental shelf a strong stratification of the water column induced a fall in the productivity. The end of this period is marked by the increase of storm regimes caused by a shift to prevailing SW winds. The last 3000 years are characterized by humid and warm conditions, and the enhancement of upwelling regime and terrestrial sediment supply. In Cies Islands, a sand barrier-lagoon complex was developed as a consequence of both the sea level rise and the inundation of the lower areas in the island.

The distribution of 4-nonylphenol in marine organisms of North American Pacific Coast estuaries.

PubMed

Diehl, Jennifer; Johnson, Sarah E; Xia, Kang; West, Amy; Tomanek, Lars

2012-04-01

One of the chemical breakdown products of nonylphenol ethoxylates, 4-nonylphenol (4-NP), accumulates in organisms and is of concern as an environmental pollutant due to its endocrine disrupting effects. We measured 4-NP levels in the seawater, sediment, and twelve organisms within the California estuary, Morro Bay, and examined biomagnification of 4-NP using stable isotope abundances (δ(15)N and δ(13)C) to quantify trophic position. 4-NP concentrations in organisms from Morro Bay included 25000±8600 ng g(-1) lw in liver of California sea lion, 14000±5600 ng g(-1) lw in liver of harbor porpoise, 138000±55000 ng g(-1) lw in liver of sea otters, 15700±3600 ng g(-1) lw in liver of seabirds, 36100±6100 ng g(-1) lw in arrow goby fish, 62800±28400 ng g(-1) lw in oysters, and 12700±1300 ng g(-1) lw in mussels. 4-NP levels generally showed a pattern of trophic dilution among organisms in Morro Bay, with exceptions of biomagnification observed between three trophic links: mussel to sea otter (BMF 10.9), oyster to sea otter (BMF 2.2), and arrow goby to staghorn sculpin (BMF 2.7). Our examination of other west coast estuaries of USA and Canada revealed that mean 4-NP concentrations in gobies and mussels from Morro Bay were significantly higher than those from a more urbanized estuary, San Francisco Bay (goby: 11100±3800 ng g(-1) lw) and from a remote estuary, Bamfield Inlet, Canada (goby: 9000±900 ng g(-1) lw, mussel: 6100±700 ng g(-1) lw). Relative to other estuaries worldwide, 4-NP levels in seawater (0.42±0.16 μg L(-1)) and sediment (53±14 ng g(-1) dw) of Morro Bay are low, but gobies and oysters have higher 4-NP levels than comparable fauna. Copyright © 2012 Elsevier Ltd. All rights reserved.

Glacier-surge mechanisms promoted by a hydro-thermodynamic feedback to summer melt

NASA Astrophysics Data System (ADS)

Dunse, T.; Schellenberger, T.; Hagen, J. O.; Kääb, A.; Schuler, T. V.; Reijmer, C. H.

2015-02-01

Mass loss from glaciers and ice sheets currently accounts for two-thirds of the observed global sea-level rise and has accelerated since the 1990s, coincident with strong atmospheric warming in the polar regions. Here we present continuous GPS measurements and satellite synthetic-aperture-radar-based velocity maps from Basin-3, the largest drainage basin of the Austfonna ice cap, Svalbard. Our observations demonstrate strong links between surface-melt and multiannual ice-flow acceleration. We identify a hydro-thermodynamic feedback that successively mobilizes stagnant ice regions, initially frozen to their bed, thereby facilitating fast basal motion over an expanding area. By autumn 2012, successive destabilization of the marine terminus escalated in a surge of Basin-3. The resulting iceberg discharge of 4.2±1.6 Gt a-1 over the period April 2012 to May 2013 triples the calving loss from the entire ice cap. With the seawater displacement by the terminus advance accounted for, the related sea-level rise contribution amounts to 7.2±2.6 Gt a-1. This rate matches the annual ice-mass loss from the entire Svalbard archipelago over the period 2003-2008, highlighting the importance of dynamic mass loss for glacier mass balance and sea-level rise. The active role of surface melt, i.e. external forcing, contrasts with previous views of glacier surges as purely internal dynamic instabilities. Given sustained climatic warming and rising significance of surface melt, we propose a potential impact of the hydro-thermodynamic feedback on the future stability of ice-sheet regions, namely at the presence of a cold-based marginal ice plug that restricts fast drainage of inland ice. The possibility of large-scale dynamic instabilities such as the partial disintegration of ice sheets is acknowledged but not quantified in global projections of sea-level rise.

Sea level rise under the Shared Socioeconomic Pathways (SSPs)

NASA Astrophysics Data System (ADS)

Schleussner, C. F.; Nauels, A.; Rogelj, J.; Mengel, M.; Meinshausen, M.

2017-12-01

In order to assess future sea level rise and its impacts, we need to study climate change pathways combined with different scenarios of socioeconomic development. Here, we present Sea Level Rise (SLR) projections for the Shared Socioeconomic Pathway (SSP) storylines and different year-2100 radiative Forcing Targets (FTs). Future SLR is estimated with a comprehensive SLR emulator that accounts for latest research on additional Antarctic rapid discharge dynamics from hydrofracturing and ice cliff instability. Across all baseline scenario realizations (no dedicated climate mitigation), we find 2100 median SLR relative to 1986-2005 of 102 cm (likely range: 77 to 135 cm) for SSP1, 118 cm (90 to 151 cm) for SSP2, 118 cm (91 to 149 cm) for SSP3, 107 cm (81 to 137 cm) for SSP4, and 144 cm (112 to 184 cm) for SSP5. The 2100 sea level responses for combined SSP-FT scenarios is dominated by the mitigation targets and yield median estimates of 68 cm (56 to 87 cm) for FT 2.6 Wm-2, 76 cm (61 to 107 cm) for FT 3.4 Wm-2, 90 cm (68 to 120 cm) for FT 4.5 Wm-2, and 105 cm (79 to 136 cm) for FT 6.0 Wm-2. Average 2081-2100 annual rates of SLR are 6 mm/yr and 19 mm/yr for the FT 2.6 Wm-2 and the baseline scenarios, respectively. Our model setup allows linking scenario-specific emission and socioeconomic indicators to projected SLR. For limiting median 2100 SSP SLR projections to below 80 cm, we find that 2050 cumulative CO2 emissions since pre-industrial should not exceed around 860 GtC, with the global coal phase-out nearly completed. For SSP mitigation scenarios, the median 2050 carbon price of 90 US$2005 tCO2-1 would correspond to a median 2100 SLR of around 80 cm. Our results confirm that rapid and early emission reductions are essential for limiting 2100 SLR.

Structural analysis and anticoagulant activities of two sulfated polysaccharides from the sea cucumber Holothuria coluber.

PubMed

Yang, Wenjiao; Cai, Ying; Yin, Ronghua; Lin, Lisha; Li, Zhongkun; Wu, Mingyi; Zhao, Jinhua

2018-05-01

Sulfated polysaccharides such as fucosylated glycosaminoglycan and fucan sulfate from echinoderm possess complex chemical structure and various biological activities. The two sulfated polysaccharides were purified from the low-value sea cucumber Holothuria coluber. Their physicochemical properties and chemical structures were analyzed and characterized by chemical and instrumental methods. Structural analysis clarified that the sea cucumber fucosylated glycosaminoglycan contains a chondroitin sulfate-like backbone and fucosyl branches with four various sulfation patterns. The fucan sulfate with molecular weight of 64.6 kDa comprises a central core of regular α(1 → 4)-linked tetrasaccharide repeating units, each of which is linked by a 4-O-sulfated fucose residue. Anticoagulant assays indicated that these sulfated polysaccharides possessed strong APTT prolonging activities and intrinsic factor Xase inhibitory activities, both of which decreased with the reduction of their molecular weights. Our results expand knowledge on the structural types of sulfated polysaccharides from sea cucumbers and further illustrate their functionality. Copyright © 2018. Published by Elsevier B.V.

Buoyant Outflows in the Presence of Ccomplex Topography

DTIC Science & Technology

2010-09-30

of the flow exchange through the Dardanelles Strait on the Aegean Sea coastal flows, cross-shelf exchanges and basin -wide eddy field; e) examine...enhance the predictive capability of operational Navy models, by developing and testing a methodology to link the Mediterranean and Black Sea basins ...in the Aegean Sea through the Dardanelles Strait was shown to have a significant impact on the basin -wide circulation, with implications on the

Egypt and Red Sea

NASA Technical Reports Server (NTRS)

1982-01-01

A panaramic view of eastern Egypt, The Red Sea and Saudi Arabia beyond (24.0N, 33.0E). In this desert country, where water is life, the high Aswan Dam and the impounded waters of the Nile River in the foreground assure water availability into the next century. The Red Sea beyond, part of the Suez Canal seaway, serves as a commercial link to the world and separates Egypt from Saudi Arabia.

Increasing value of wilderness: Protecting cultural heritage

Treesearch

Herbert O. Anungazuk

2002-01-01

The land and the sea have been direct links to survival to a hardy group of people in the northern extremes of the Earth. Each group is separate to its own domain, and their land and sea differ even if the distance between them is not great. The rules of the land and the sea are unwritten, and they have been presented to the new generations by Elders through the...

Spatial-temporal analysis of sea level changes in China seas and neighboring oceans by merged altimeter data

NASA Astrophysics Data System (ADS)

Xu, Yao; Zhou, Bin; Yu, Zhifeng; Lei, Hui; Sun, Jiamin; Zhu, Xingrui; Liu, Congjin

2017-01-01

The knowledge of sea level changes is critical important for social, economic and scientific development in coastal areas. Satellite altimeter makes it possible to observe long term and large scale dynamic changes in the ocean, contiguous shelf seas and coastal zone. In this paper, 1993-2015 altimeter data of Topex/Poseidon and its follow-on missions is used to get a time serious of continuous and homogeneous sea level anomaly gridding product. The sea level rising rate is 0.39 cm/yr in China Seas and the neighboring oceans, 0.37 cm/yr in the Bo and Yellow Sea, 0.29 cm/yr in the East China Sea and 0.40 cm/yr in the South China Sea. The mean sea level and its rising rate are spatial-temporal non-homogeneous. The mean sea level shows opposite characteristics in coastal seas versus open oceans. The Bo and Yellow Sea has the most significant seasonal variability. The results are consistent with in situ data observation by the Nation Ocean Agency of China. The coefficient of variability model is introduced to describe the spatial-temporal variability. Results show that the variability in coastal seas is stronger than that in open oceans, especially the seas off the entrance area of the river, indicating that the validation of altimeter data is less reasonable in these seas.

Understanding extreme sea levels for coastal impact and adaptation analysis

NASA Astrophysics Data System (ADS)

Wahl, T.; Haigh, I. D.; Nicholls, R. J.; Arns, A.; Hinkel, J.; Dangendorf, S.; Slangen, A.

2016-12-01

Coastal impact and adaptation assessments require detailed knowledge on extreme sea levels, because increasing damage due to extreme events, such as storm surges and tropical cyclones, is one of the major consequences of sea level rise and climate change. In fact, the IPCC has highlighted in its AR4 report that "societal impacts of sea level change primarily occur via the extreme levels rather than as a direct consequence of mean sea level changes". Over the last few decades, substantial research efforts have been directed towards improved understanding of past and future mean sea level; different scenarios were developed with process-based or semi-empirical models and used for coastal impact assessments at various spatial scales to guide coastal management and adaptation efforts. The uncertainties in future sea level rise are typically accounted for by analyzing the impacts associated with a range of scenarios leading to a vertical displacement of the distribution of extreme sea-levels. And indeed most regional and global studies find little or no evidence for changes in storminess with climate change, although there is still low confidence in the results. However, and much more importantly, there is still a limited understanding of present-day extreme sea-levels which is largely ignored in most impact and adaptation analyses. The two key uncertainties stem from: (1) numerical models that are used to generate long time series of extreme sea-levels. The bias of these models varies spatially and can reach values much larger than the expected sea level rise; but it can be accounted for in most regions making use of in-situ measurements; (2) Statistical models used for determining present-day extreme sea-level exceedance probabilities. There is no universally accepted approach to obtain such values for flood risk assessments and while substantial research has explored inter-model uncertainties for mean sea level, we explore here, for the first time, inter-model uncertainties for extreme sea-levels at large spatial scales and compare them to the uncertainties in mean sea level projections.

A Poor Relationship Between Sea Level and Deep-Water Sand Delivery

NASA Astrophysics Data System (ADS)

Harris, Ashley D.; Baumgardner, Sarah E.; Sun, Tao; Granjeon, Didier

2018-08-01

The most commonly cited control on delivery of sand to deep water is the rate of relative sea-level fall. The rapid rate of accommodation loss on the shelf causes sedimentation to shift basinward. Field and experimental numerical modeling studies have shown that deep-water sand delivery can occur during any stage of relative sea level position and across a large range of values of rate of relative sea-level change. However, these studies did not investigate the impact of sediment transport efficiency on the relationship between rate of relative sea-level change and deep-water sand delivery rate. We explore this relationship using a deterministic nonlinear diffusion-based numerical stratigraphic forward model. We vary across three orders of magnitude the diffusion coefficient value for marine settings, which controls sediment transport efficiency. We find that the rate of relative sea-level change can explain no more than 1% of the variability in deep-water sand delivery rates, regardless of sediment transport efficiency. Model results show a better correlation with relative sea level, with up to 55% of the variability in deep water sand delivery rates explained. The results presented here are consistent with studies of natural settings which suggest stochastic processes such as avulsion and slope failure, and interactions among such processes, may explain the remaining variance. Relative sea level is a better predictor of deep-water sand delivery than rate of relative sea-level change because it is the sea-level fall itself which promotes sand delivery, not the rate of the fall. We conclude that the poor relationship between sea level and sand delivery is not an artifact of the modeling parameters but is instead due to the inadequacy of relative sea level and the rate of relative sea-level change to fully describe the dimensional space in which depositional systems reside. Subsequently, sea level itself is unable to account for the interaction of multiple processes that contribute to sand delivery to deep water.

Flooded! An Investigation of Sea-Level Rise in a Changing Climate

ERIC Educational Resources Information Center

Gillette, Brandon; Hamilton, Cheri

2011-01-01

Explore how melting ice sheets affect global sea levels. Sea-level rise (SLR) is a rise in the water level of the Earth's oceans. There are two major kinds of ice in the polar regions: sea ice and land ice. Land ice contributes to SLR and sea ice does not. This article explores the characteristics of sea ice and land ice and provides some hands-on…

Grain-size based sea-level reconstruction in the south Bohai Sea during the past 135 kyr

NASA Astrophysics Data System (ADS)

Yi, Liang; Chen, Yanping

2013-04-01

Future anthropogenic sea-level rise and its impact on coastal regions is an important issue facing human civilizations. Due to the short nature of the instrumental record of sea-level change, development of proxies for sea-level change prior to the advent of instrumental records is essential to reconstruct long-term background sea-level changes on local, regional and global scales. Two of the most widely used approaches for past sea-level changes are: (1) exploitation of dated geomorphologic features such as coastal sands (e.g. Mauz and Hassler, 2000), salt marsh (e.g. Madsen et al., 2007), terraces (e.g. Chappell et al., 1996), and other coastal sediments (e.g. Zong et al., 2003); and (2) sea-level transfer functions based on faunal assemblages such as testate amoebae (e.g. Charman et al., 2002), foraminifera (e.g. Chappell and Shackleton, 1986; Horton, 1997), and diatoms (e.g. Horton et al., 2006). While a variety of methods has been developed to reconstruct palaeo-changes in sea level, many regions, including the Bohai Sea, China, still lack detailed relative sea-level curves extending back to the Pleistocene (Yi et al., 2012). For example, coral terraces are absent in the Bohai Sea, and the poor preservation of faunal assemblages makes development of a transfer function for a relative sea-level reconstruction unfeasible. In contrast, frequent alternations between transgression and regression has presumably imprinted sea-level change on the grain size distribution of Bohai Sea sediments, which varies from medium silt to coarse sand during the late Quaternary (IOCAS, 1985). Advantages of grainsize-based relative sea-level transfer function approaches are that they require smaller sample sizes, allowing for replication, faster measurement and higher spatial or temporal resolution at a fraction of the cost of detail micro-palaeontological analysis (Yi et al., 2012). Here, we employ numerical methods to partition sediment grain size using a combined database of marine surface and core samples, and to quantitatively reconstruct sea-level variation since the late Pleistocene in the south Bohai Sea, China. New insights into regional relative sea-level changes since the late Pleistocene are obtained (Yi et al., 2012): (1) The grain size of surface and core samples can be mathematically partitioned using the Weibull distribution into four components. These four components with differing modal sizes and percentages could be interpreted as a long-term suspension component, which only settles under low turbulence conditions, sortable silt and very fine sand components transported by suspension during greater turbulence and bedload transport component, respectively. (2) Through regression and rigorous verification techniques, the reference water level could be reconstructed from sediment grain size. The reconstruction quantitatively extends the regional relative sea-level history to the late Pleistocene, providing a comparatively long dataset to evaluate regional sea-level variability. (3) We find no evidence of a sea-level high stand during MIS3 but rather a substantial regression during 70-30 cal kyr BP and potentially exposed land during 38-20 cal kyr BP. These results for the south Bohai Sea are in good agreement with published global sea-level records for the late Pleistocene, implying similarities between local and global sea-level patterns. Therefore, it is concluded that grain-size based sea-level reconstruction provide results that are comparable to other reconstruction methods and demonstrates great potential application for future works. (The data was shared on http://hurricane.ncdc.noaa.gov/) References Chappell, J., Omura, A., Esat, T., McCulloch, M., Pandolfi, J., Ota, Y., Pillans, B., 1996. Reconciliation of late Quaternary sea levels derived from coral terraces at Huon Peninsula with deep sea oxygen isotope records. Earth and Planetary Science Letters 141, 227-236. Chappell, J., Shackleton, N.J., 1986. Oxygen isotopes and sea level. Nature 324, 137-140. Charman, D.J., Roe, H.M., Roland Gehrels, W., 2002. Modern distribution of saltmarsh testate amoebae: regional variability of zonation and response to environmental variables. Journal of Quaternary Science 17, 387-409. Horton, B.P., 1997. Quantification of the indicative meaning of a range of Holocene sea-level index points from the western North Sea, Department of Geography. University of Durham, Durham City, UK, p. 509. Horton, B.P., Corbett, R., Culver, S.J., Edwards, R.J., Hillier, C., 2006. Modern saltmarsh diatom distributions of the Outer Banks, North Carolina, and the development of a transfer function for high resolution reconstructions of sea level. Estuarine, Coastal and Shelf Science 69, 381-394. IOCAS (Institute of Oceanology, Chinese Academy of Sciences), 1985. Bohai Sea Geology. Science Press, Beijing, China. Madsen, A.T., Murray, A.S., Andersen, T.J., Pejrup, M., 2007. Temporal changes of accretion rates on an estuarine salt marsh during the late Holocene -Reflection of local sea level changes? The Wadden Sea, Denmark. Marine Geology 242, 221-233. Mauz, B., Hassler, U., 2000. Luminescence chronology of Late Pleistocene raised beaches in southern Italy: new data of relative sea-level changes. Marine Geology 170, 187-203. Yi, L., Yu, H.J., Ortiz, J.D., Xu, X.Y., Qiang, X.K., Huang, H.J., Shi, X., Deng, C.L., 2012. A reconstruction of late Pleistocene relative sea level in the south Bohai Sea, China, based on sediment grain-size analysis. Sedimentary Geology 281, 88-100. Zong, Y., Shennan, I., Combellick, R.A., Hamilton, S.L., Rutherford, M.M., 2003. Microfossil evidence for land movements associated with the AD 1964 Alaska earthquake. The Holocene 13, 7-20.

Timing of Quaternary Marine Terrace Formation and Uplift Rates in the Eastern Pontides, NE Turkey

NASA Astrophysics Data System (ADS)

Softa, M.; Spencer, J. Q. G.; Emre, T.; Sözbilir, H.; Turan, M.

2016-12-01

Quaternary records of marine terraces formation are indispensable tool for the better understanding sea-level changes in the coastal region of Pontides. Time of the marine terraces with linked to date of the depositional of its are very crucial to know for active tectonic evolution in this study area. The ages of the marine terraces are not well known in the coastal region of Trabzon and Rize. In the coastal region of eastern Pontides, we have identified three marine terrace levels. Using the optically stimulated dating we show that these three sedimentation period were formed during the at 8.3 ± 2.5 ka, 42 ± 1.8 ka and 78.3 ± 6.1 ka. These ages correspond to marine isotopic stages (MIS) or substages (MISS) 1, 3 and 5a sea level, respectively. The apparent vertical movement is ranging from 1.0 mm/yr to 0.59 mm/yr that obtained from marine terraces in the northeastern of Pontides. We will present timing of the marine terrace formation and vertical movement in the coastal region of Trabzon and Rize. Key words: OSL dating, vertical movement, marine terraces, active tectonic, eastern Pontides.

Mud Banks along the southwest coast of India are not too muddy for plankton.

PubMed

Jyothibabu, R; Balachandran, K K; Jagadeesan, L; Karnan, C; Arunpandi, N; Naqvi, S W A; Pandiyarajan, R S

2018-02-07

Considering Alappuzha Mud Bank in the southern Kerala coast as a typical case of biologically productive Mud Banks that form along the southwest coast of India during the Southwest Monsoon (June - September), the present study addresses several pertinent missing links between the physical environment in Mud Banks and their influence on plankton stock. This study showed that very strong coastal upwelling prevails in the entire study domain during the Southwest Monsoon, which manifests itself in the form of significantly cool, hypoxic and nitrate-rich waters surfacing near the coast. The upwelled water persisting throughout the Southwest Monsoon period was found to have fuelled the exceptionally high phytoplankton stock in the entire study area, including the Mud Bank region. Having accepted that Mud Banks are special because of the calm sea surface conditions and relatively high turbidity level in the water column around them, the present study showed that except at points close to the sea bottom, turbidity level in the Alappuzha Mud Bank was below the critical level to inhibit the plankton stock. The suspended sediments that form in the Mud Bank occasionally could be attributed to the disturbance of the bottom fluid muddy layer and their vertical spurts.

Climate related sea-level variations over the past two millennia

PubMed Central

Kemp, Andrew C.; Horton, Benjamin P.; Donnelly, Jeffrey P.; Mann, Michael E.; Vermeer, Martin; Rahmstorf, Stefan

2011-01-01

We present new sea-level reconstructions for the past 2100 y based on salt-marsh sedimentary sequences from the US Atlantic coast. The data from North Carolina reveal four phases of persistent sea-level change after correction for glacial isostatic adjustment. Sea level was stable from at least BC 100 until AD 950. Sea level then increased for 400 y at a rate of 0.6 mm/y, followed by a further period of stable, or slightly falling, sea level that persisted until the late 19th century. Since then, sea level has risen at an average rate of 2.1 mm/y, representing the steepest century-scale increase of the past two millennia. This rate was initiated between AD 1865 and 1892. Using an extended semiempirical modeling approach, we show that these sea-level changes are consistent with global temperature for at least the past millennium. PMID:21690367

Long-term sea level trends: Natural or anthropogenic?

NASA Astrophysics Data System (ADS)

Becker, M.; Karpytchev, M.; Lennartz-Sassinek, S.

2014-08-01

Detection and attribution of human influence on sea level rise are important topics that have not yet been explored in depth. We question whether the sea level changes (SLC) over the past century were natural in origin. SLC exhibit power law long-term correlations. By estimating Hurst exponent through Detrended Fluctuation Analysis and by applying statistics of Lennartz and Bunde, we search the lower bounds of statistically significant external sea level trends in longest tidal records worldwide. We provide statistical evidences that the observed SLC, at global and regional scales, is beyond its natural internal variability. The minimum anthropogenic sea level trend (MASLT) contributes to the observed sea level rise more than 50% in New York, Baltimore, San Diego, Marseille, and Mumbai. A MASLT is about 1 mm/yr in global sea level reconstructions that is more than half of the total observed sea level trend during the XXth century.

Quantitative analysis of Paratethys sea level change during the Messinian Salinity Crisis

NASA Astrophysics Data System (ADS)

de la Vara, Alba; Meijer, Paul; van Baak, Christiaan; Marzocchi, Alice; Grothe, Arjen

2016-04-01

At the time of the Messinian Salinity Crisis in the Mediterranean Sea (i.e., the Pontian stage of the Paratethys), the Paratethys sea level dropped also. Evidence found in the sedimentary record of the Black Sea and the Caspian Sea has been interpreted to indicate that a sea level fall occurred between 5.6 and 5.5 Ma. Estimates for the magnitude of the fall range between tens of meters to more than 1500 m. The purpose of this study is to provide quantitative insight into the sensitivity of the water level of the Black Sea and the Caspian Sea to the hydrologic budget, for the case that the Paratethys is disconnected from the Mediterranean. Using a Late Miocene bathymetry based on a palaeographic map by Popov et al. (2004) we quantify the fall in sea level, the mean salinity, and the time to reach equilibrium for a wide range of negative hydrologic budgets. By combining our results with (i) estimates derived from a recent global Late Miocene climate simulation and (ii) reconstructed basin salinities, we are able to rule out a drop in sea level of the order of 1000 m in the Caspian Sea during this time period. In the Black Sea, however, such a large sea level fall cannot be fully discarded.

Sea level budget in the Arctic during the satellite altimetry era

NASA Astrophysics Data System (ADS)

Carret, Alice; Cazenave, Anny; Meyssignac, Benoît; Prandi, Pierre; Ablain, Michael; Andersen, Ole; Blazquez, Alejandro

2016-04-01

Studying sea level variations in the Arctic region is challenging because of data scarcity. Here we present results of the sea level budget in the Arctic (up to 82°N) during the altimetry era. We first investigate closure of the sea level budget since 2002 using altimetry data from Envisat and Cryosat for estimating sea level, temperature and salinity data from the ORAP5 reanalysis and GRACE space gravimetry to estimate the steric and mass components. Two altimetry sea level data sets are considered (from DTU and CLS), based on Envisat waveforms retracking. Regional sea level trends seen in the altimetric map, in particular over the Beaufort Gyre and along the eastern coast of Greenland are of steric origin. However, in terms of regional average, the steric component contributes very little to the observed sea level trend, suggesting a dominant mass contribution in the Arctic region. This is confirmed by GRACE-based ocean mass time series that agree very well with the altimetry-based sea level time series. Direct estimate of the mass component is not possible prior to GRACE. Thus we estimated the mass contribution over the whole altimetry era from the difference between altimetry-based sea level and the ORAP5 steric component. Finally we compared altimetry-based coastal sea level with tide gauge records available along Norwegian, Greenland and Siberian coastlines and investigated whether the Arctic Oscillation that was the main driver of coastal sea level in the Arctic during the past decades still plays a dominant role or if other factors (e.g., of anthropogenic origin) become detectable.

Generalized Cauchy model of sea level fluctuations with long-range dependence

NASA Astrophysics Data System (ADS)

Li, Ming; Li, Jia-Yue

2017-10-01

This article suggests the contributions with two highlights. One is to propose a novel model of sea level fluctuations (sea level for short), which is called the generalized Cauchy (GC) process. It provides a new outlook for the description of local and global behaviors of sea level from a view of fractal in that the fractal dimension D that measures the local behavior of sea level and the Hurst parameter H which characterizes the global behavior of sea level are independent of each other. The other is to show that sea level appears multi-fractal in both spatial and time. Such a meaning of multi-fractal is new in the sense that a pair of fractal parameters (D, H) of sea level is varying with measurement sites and time. This research exhibits that the ranges of D and H of sea level, in general, are 1 ≤ D < 2 and 0 . 5 < H < 1, respectively but D is independent of H. With respect to the global behavior of sea level, we shall show that H > 0 . 96 for all data records at all measurement sites, implying that strong LRD may be a general phenomenon of sea level. On the other side, regarding with the local behavior, we will reveal that there appears D = 1 or D ≈ 1 for data records at a few stations and at some time, but D > 0 . 96 at most stations and at most time, meaning that sea level may appear highly local irregularity more frequently than weak local one.

Inception of a global atlas of Holocene sea levels

NASA Astrophysics Data System (ADS)

Khan, Nicole; Rovere, Alessio; Engelhart, Simon; Horton, Benjamin

2017-04-01

Determining the rates, mechanisms and geographic variability of sea-level change is a priority science question for the next decade of ocean research. To address these research priorities, the HOLocene SEA-level variability (HOLSEA) working group is developing the first standardized global synthesis of Holocene relative sea-level data to: (1) estimate the magnitudes and rates of global mean sea-level change during the Holocene; and (2) identify trends in spatial variability and decipher the processes responsible for geographic differences in relative sea-level change. Here we present the preliminary efforts of the working group to compile the database, which includes sea-level index points and limiting data from a range of different indicators across seven continents from the Last Glacial Maximum to present. We follow a standard protocol that incorporates full consideration of vertical and temporal uncertainty for each sea-level index point, including uncertainties associated with the relationship of each indicator to past sea-level and the methods used to date each indicator. We describe the composition of the global database, identify gaps in data availability, and highlight our effort to create an online platform to access the data. These data will be made available in a special issue of Quaternary Science Reviews and archived on NOAA's National Centers for Environmental Information (NCEI) in early 2018. We also invite researchers who collect or model Holocene sea-level data to participate. Long-term, this effort will enhance predictions of 21st century sea-level rise, and provide a vital contribution to the assessment of natural hazards with respect to sea-level rise and coastal response.

Sea-level and deep-sea-temperature variability over the past 5.3 million years.

PubMed

Rohling, E J; Foster, G L; Grant, K M; Marino, G; Roberts, A P; Tamisiea, M E; Williams, F

2014-04-24

Ice volume (and hence sea level) and deep-sea temperature are key measures of global climate change. Sea level has been documented using several independent methods over the past 0.5 million years (Myr). Older periods, however, lack such independent validation; all existing records are related to deep-sea oxygen isotope (δ(18)O) data that are influenced by processes unrelated to sea level. For deep-sea temperature, only one continuous high-resolution (Mg/Ca-based) record exists, with related sea-level estimates, spanning the past 1.5 Myr. Here we present a novel sea-level reconstruction, with associated estimates of deep-sea temperature, which independently validates the previous 0-1.5 Myr reconstruction and extends it back to 5.3 Myr ago. We find that deep-sea temperature and sea level generally decreased through time, but distinctly out of synchrony, which is remarkable given the importance of ice-albedo feedbacks on the radiative forcing of climate. In particular, we observe a large temporal offset during the onset of Plio-Pleistocene ice ages, between a marked cooling step at 2.73 Myr ago and the first major glaciation at 2.15 Myr ago. Last, we tentatively infer that ice sheets may have grown largest during glacials with more modest reductions in deep-sea temperature.

Future Earth Coasts: The Mississippi and Yangtze Rivers as Examples

NASA Astrophysics Data System (ADS)

D'Elia, C.; Xu, K.; Chen, Z.; Day, J.; Le Tissier, M.

2016-02-01

Deltas and estuaries are productive and fertile links between the land and the sea. Deltas occupy only about 5% of the Earth's surface but sustain over a half billion people all around the world. Many river deltas are endangered because of extensive dam and levee construction, declining sediment supply, groundwater withdrawal, relative sea level rise and severe coastal erosion, leading to a variety of threats to natural, economic and social systems. About 630 million people now live at an elevation of 10 m or less above mean sea level, and maintaining sustainable land with a rising sea will be a challenging problem for many major deltaic coasts and cities in the next century. Stemming from 20 years of LOICZ (Land-Ocean Interactions in the Coastal Zone), Future Earth Coasts is a new global initiative that seeks to enable the scientific and social scientific communities to build knowledge through collaborative processes to better understand and address the profound and urgent changes occurring in vulnerable coastal zones. The topics of this comparative study are the Mississippi and Yangtze (Changjiang) Rivers, the largest in the United States and China, respectively. We use these two rivers as examples to evaluate current conditions and catalyze future discussion. The Mississippi and Yangtze both have had long-term observations of physical and biological processes that affect human activities, making it possible to quantify both natural and anthropogenic impacts. We also consider the limits to concept of sustainability for the Earth's biosphere and human civilization, and emphasize biophysical constraints and demographic challenges.

Effects of ocean acidification and diet on thickness and carbonate elemental composition of the test of juvenile sea urchins.

PubMed

Asnaghi, Valentina; Mangialajo, Luisa; Gattuso, Jean-Pierre; Francour, Patrice; Privitera, Davide; Chiantore, Mariachiara

2014-02-01

Continuous anthropogenic CO2 emissions to the atmosphere and uptake by the oceans will cause a reduction of seawater pH and saturation state (Ω) of CaCO3 minerals from which marine calcifiers build their shells and skeletons. Sea urchins use the most soluble form of calcium carbonate, high-magnesium calcite, to build their skeleton, spines and grazing apparatus. In order to highlight the effects of increased pCO2 on the test thickness and carbonate elemental composition of juvenile sea urchins and potential differences in their responses linked to the diet, we performed a laboratory experiment on juvenile Paracentrotus lividus, grazing on calcifying (Corallina elongata) and non-calcifying (Cystoseira amentacea, Dictyota dichotoma) macroalgae, under different pH (corresponding to pCO2 values of 390, 550, 750 and 1000 μatm). Results highlighted the importance of the diet in determining sea urchin size irrespectively of the pCO2 level, and the relevance of macroalgal diet in modulating urchin Mg/Ca ratio. The present study provides relevant clues both in terms of the mechanism of mineral incorporation and in terms of bottom-up processes (algal diet) affecting top-down ones (fish predation) in rocky subtidal communities. Copyright © 2013 Elsevier Ltd. All rights reserved.

The role of atmospheric circulation patterns on short-term sea-level fluctuations along the eastern seaboard of the US

NASA Astrophysics Data System (ADS)

Sheridan, S. C.; Lee, C. C.; Pirhalla, D.; Ransi, V.

2017-12-01

Sea-level fluctuations over time are a product of short-term weather events, as well as long-term secular trends in sea-level rise. With sea-levl rise, these fluctuations increasingly have substantial impacts upon coastal ecosystems and impact society through coastal flooding events. In this research, we assess the impact of short-term events, combined with sea-level rise, through synoptic climatological analysis, exploring whether circulation pattern identification can be used to enhance probabilistic forecasts of flood likelihood. Self-organizing maps (SOMs) were created for two discrete atmospheric variables: 700-hPa geopotential height (700z) and sea-level pressure (SLP). For each variable, a SOM array of patterns was created based on data spanning 25°-50°N and 60°-90°W for the period 1979-2014. Sea-level values were derived from tidal gauges between Cape May, New Jersey and Charleston, South Carolina, along the mid-Atlantic coast of the US. Both anomalous sea-level values, as well as nuisance flood occurrence (defined using the local gauge threshold), were assessed. Results show the impacts of both the inverted barometer effect as well as surface wind forcing on sea levels. With SLP, higher sea levels are associated with either patterns that were indicative of on-shore flow or cyclones. At 700z, ridges situated along the east coast are associated with higher sea levels. As the SOM matrix arranges atmospheric patterns in a continuum, the nodes of each SOM show a clear spatial pattern in terms of anomalous sea level, including some significant sea-level anomalies associated with relatively ambiguous pressure patterns. Further, multi-day transitions are also analyzed, showing rapidly deepening cyclones, or persistent onshore flow, can be associated with the greatest likelihood of nuisance floods. Results are weaker with 700z than SLP; however, in some cases, it is clear that the mid-tropospheric circulation can modulate the connection between sea-level anomalies and surface circulation.

Improving sea level simulation in Mediterranean regional climate models

NASA Astrophysics Data System (ADS)

Adloff, Fanny; Jordà, Gabriel; Somot, Samuel; Sevault, Florence; Arsouze, Thomas; Meyssignac, Benoit; Li, Laurent; Planton, Serge

2017-08-01

For now, the question about future sea level change in the Mediterranean remains a challenge. Previous climate modelling attempts to estimate future sea level change in the Mediterranean did not meet a consensus. The low resolution of CMIP-type models prevents an accurate representation of important small scales processes acting over the Mediterranean region. For this reason among others, the use of high resolution regional ocean modelling has been recommended in literature to address the question of ongoing and future Mediterranean sea level change in response to climate change or greenhouse gases emissions. Also, it has been shown that east Atlantic sea level variability is the dominant driver of the Mediterranean variability at interannual and interdecadal scales. However, up to now, long-term regional simulations of the Mediterranean Sea do not integrate the full sea level information from the Atlantic, which is a substantial shortcoming when analysing Mediterranean sea level response. In the present study we analyse different approaches followed by state-of-the-art regional climate models to simulate Mediterranean sea level variability. Additionally we present a new simulation which incorporates improved information of Atlantic sea level forcing at the lateral boundary. We evaluate the skills of the different simulations in the frame of long-term hindcast simulations spanning from 1980 to 2012 analysing sea level variability from seasonal to multidecadal scales. Results from the new simulation show a substantial improvement in the modelled Mediterranean sea level signal. This confirms that Mediterranean mean sea level is strongly influenced by the Atlantic conditions, and thus suggests that the quality of the information in the lateral boundary conditions (LBCs) is crucial for the good modelling of Mediterranean sea level. We also found that the regional differences inside the basin, that are induced by circulation changes, are model-dependent and thus not affected by the LBCs. Finally, we argue that a correct configuration of LBCs in the Atlantic should be used for future Mediterranean simulations, which cover hindcast period, but also for scenarios.

Sea-level rise caused by climate change and its implications for society.

PubMed

Mimura, Nobuo

2013-01-01

Sea-level rise is a major effect of climate change. It has drawn international attention, because higher sea levels in the future would cause serious impacts in various parts of the world. There are questions associated with sea-level rise which science needs to answer. To what extent did climate change contribute to sea-level rise in the past? How much will global mean sea level increase in the future? How serious are the impacts of the anticipated sea-level rise likely to be, and can human society respond to them? This paper aims to answer these questions through a comprehensive review of the relevant literature. First, the present status of observed sea-level rise, analyses of its causes, and future projections are summarized. Then the impacts are examined along with other consequences of climate change, from both global and Japanese perspectives. Finally, responses to adverse impacts will be discussed in order to clarify the implications of the sea-level rise issue for human society.(Communicated by Kiyoshi HORIKAWA, M.J.A.).

Regional characteristics of the effects of the El Niño-Southern Oscillation on the sea level in the China Sea

NASA Astrophysics Data System (ADS)

Wang, Hui; Liu, Kexiu; Wang, Aimei; Feng, Jianlong; Fan, Wenjing; Liu, Qiulin; Xu, Yao; Zhang, Zengjian

2018-05-01

Based on coastal tide level, satellite altimetry, and sea surface temperature (SST) data of offshore areas of China's coast and the equatorial Pacific Ocean, the regional characteristics of the effects of the El Niño-Southern Oscillation (ENSO) on the sea level in the China Sea were investigated. Singular value decomposition results show a significant teleconnection between the sea level in the China Sea and the SST of the tropical Pacific Ocean; the correlation coefficient decreases from south to north. Data from tide gauges along China's coast show that the seasonal sea-level variations are significantly correlated with the ENSO. In addition, China's coast was divided into three regions based on distinctive regional characteristics. Results obtained show that the annual amplitude of sea level was low during El Niño developing years, and especially so during the El Niño year. The ENSO intensity determined the response intensity of the annual amplitude of the sea level. The response region (amplitude) was relatively large for strong ENSO intensities. Significant oscillation periods at a timescale of 4-7 years existed in the sea level of the three regions. The largest amplitude of oscillation was 1.5 cm, which was the fluctuation with the 7-year period in the South China Sea. The largest amplitude of oscillation in the East China Sea was about 1.3 cm. The amplitude of oscillation with the 6-year period in the Bohai Sea and Yellow Sea was the smallest (less than 1 cm).

Increased Surface Wind Speeds Follow Diminishing Arctic Sea Ice

NASA Astrophysics Data System (ADS)

Mioduszewski, J.; Vavrus, S. J.; Wang, M.; Holland, M. M.; Landrum, L.

2017-12-01

Projections of Arctic sea ice through the end of the 21st century indicate the likelihood of a strong reduction in ice area and thickness in all seasons, leading to a substantial thermodynamic influence on the overlying atmosphere. This is likely to have an effect on winds over the Arctic Basin, due to changes in atmospheric stability and/or baroclinicity. Prior research on future Arctic wind changes is limited and has focused mainly on the practical impacts on wave heights in certain seasons. Here we attempt to identify patterns and likely mechanisms responsible for surface wind changes in all seasons across the Arctic, particularly those associated with sea ice loss in the marginal ice zone. Sea level pressure, near-surface (10 m) and upper-air (850 hPa) wind speeds, and lower-level dynamic and thermodynamic variables from the Community Earth System Model Large Ensemble Project (CESM-LE) were analyzed for the periods 1971-2000 and 2071-2100 to facilitate comparison between a present-day and future climate. Mean near-surface wind speeds over the Arctic Ocean are projected to increase by late century in all seasons but especially during autumn and winter, when they strengthen by up to 50% locally. The most extreme wind speeds in the 90th percentile change even more, increasing in frequency by over 100%. The strengthened winds are closely linked to decreasing lower-tropospheric stability resulting from the loss of sea ice cover and consequent surface warming (locally over 20 ºC warmer in autumn and winter). A muted pattern of these future changes is simulated in CESM-LE historical runs from 1920-2005. The enhanced winds near the surface are mostly collocated with weaker winds above the boundary layer during autumn and winter, implying more vigorous vertical mixing and a drawdown of high-momentum air.The implications of stronger future winds include increased coastal hazards and the potential for a positive feedback with sea ice by generating higher winds and greater wave activity. Our findings suggest that increasing winds, along with retreating sea ice and thawing permafrost, represent another important contributor to the growing problem of Arctic coastal erosion.

Quantifying and Projecting Relative Sea-Level Rise At The Regional Scale: The Bangladesh Sea-Level Project (BanD-AID)

NASA Astrophysics Data System (ADS)

Shum, C. K.; Kuo, C. Y.; Guo, J.; Shang, K.; Tseng, K. H.; Wan, J.; Calmant, S.; Ballu, V.; Valty, P.; Kusche, J.; Hossain, F.; Khan, Z. H.; Rietbroek, R.; Uebbing, B.

2014-12-01

The potential for accelerated sea-level rise under anthropogenic warming is a significant societal problem, in particular in world's coastal deltaic regions where about half of the world's population resides. Quantifying geophysical sources of sea-level rise with the goal of improved projection at local scales remains a complex and challenging interdisciplinary research problem. These processes include ice-sheet/glacier ablations, steric sea-level, solid Earth uplift or subsidence due to GIA, tectonics, sediment loading or anthropogenic causes, hydrologic imbalance, and human processes including water retention in reservoirs and aquifer extraction. The 2013 IPCC AR5 concluded that the observed and explained geophysical causes of global geocentric sea-level rise, 1993-2010, is closer towards closure. However, the discrepancy reveals that circa 1.3→37.5% of the observed sea-level rise remains unexplained. This relatively large discrepancy is primarily attributable to the wide range of estimates of respective contributions of Greenland and Antarctic ice-sheets and mountain/peripheral glaciers to sea-level rise. Understanding and quantifying the natural and anthropogenic processes governing solid Earth (land, islands and sea-floor) uplift or subsidence at the regional and local scales remain elusive to enable addressing coastal vulnerability due to relative sea-level rise hazards, such as the Bangladesh Delta. This study focuses on addressing coastal vulnerability of Bangladesh, a Belmont Forum/IGFA project, BanD-AID (http://Belmont-SeaLevel.org). Sea-level rise, along with tectonic, sediment load and groundwater extraction induced land uplift/subsidence, have exacerbated Bangladesh's coastal vulnerability, affecting 150 million people in one of the world's most densely populated regions. Here we present preliminary results using space geodetic observations, including satellite radar and laser altimetry, GRACE gravity, tide gauge, hydrographic, and GPS/InSAR observed land subsidence, and via fingerprint sea-level adjustment and reconstructed sea-level approaches, for improved quantification of major contributions to, and the projection of relative sea-level rise at the Bangladesh delta, towards addressing its coastal vulnerability and sustainability.

Space Geodesy: The Cross-Disciplinary Earth science (Vening Meinesz Medal Lecture)

NASA Astrophysics Data System (ADS)

Shum, C. K.

2012-04-01

Geodesy during the onset of the 21st Century is evolving into a transformative cross-disciplinary Earth science field. The pioneers before or after the discipline Geodesy was defined include Galileo, Descartes, Kepler, Newton, Euler, Bernoulli, Kant, Laplace, Airy, Kelvin, Jeffreys, Chandler, Meinesz, Kaula, and others. The complicated dynamic processes of the Earth system manifested by interactions between the solid Earth and its fluid layers, including ocean, atmosphere, cryosphere and hydrosphere, and their feedbacks are linked with scientific problems such as global sea-level rise resulting from natural and anthropogenic climate change. Advances in the precision and stability of geodetic and fundamental instrumentations, including clocks, satellite or quasar tracking sensors, altimetry and lidars, synthetic aperture radar interferometry (InSAR), InSAR altimetry, gravimetry and gradiometry, have enabled accentuate and transformative progress in cross-disciplinary Earth sciences. In particular, advances in the measurement of the gravity with modern free-fall methods have reached accuracies of 10-9 g (~1 μGal or 10 nm/s2) or better, allowing accurate measurements of height changes at ~3 mm relative to the Earth's center of mass, and mass transports within the Earth interior or its geophysical fluids, enabling global quantifications of climate-change signals. These contemporary space geodetic and in situ sensors include, but not limited to, satellite radar and laser altimetry/lidars, GNSS/SLR/VLBI/DORIS, InSAR, spaceborne gravimetry from GRACE (Gravity Recovery And Climate Experiment twin-satellite mission) and gradiometry from GOCE (Global Ocean Circulation Experiment), tide gauges, and hydrographic data (XBT/MBT/Argo). The 2007 Intergovernmental Panel for Climate Change (IPCC) study, the Fourth Assessment Report (AR4), substantially narrowed the discrepancy between observation and the known geophysical causes of sea-level rise, but significant uncertainties remain, notably in the discrepancies of contributions from the ice-reservoirs (ice-sheet and mountain glaciers/ice caps) and our knowledge in the solid Earth glacial isostatic adjustment (GIA), to the present-day and 20th Century global sea-level rise. Here we report our use of contemporary space geodetic observations and novel methodologies to address a few of the open Earth science questions, including the potential quantifications of the major geophysical contributions to or causing present-day global sea-level rise, and the subsequent narrowing of the current sea-level budget discrepancy.

Environment and Climate Changes during the Holocene: Inferred from Sedimentary Record/Proxies of a Paleodelta Region, Southwest Coast of India

NASA Astrophysics Data System (ADS)

Allu, N. C.; Prakash, V.; Gautam, P. K.; Bera, S. K.

2014-12-01

This work explains the sedimentation history and environment and climate changes during the Holocene along the southwest coast of India. The area is characterized by various landforms such as lagoons, barrier islands, beach ridges, paleostrandlines, alluvial plains, marshy lands and flood plains. Paleodelta, located at the mouth of the modern Periyar River is an important geomorphic marker. A borehole of 40 m depth was drilled in the paleodelta and sediment samples were recovered at different depth intervals. Paleoclimate and paleo-environment were inferred based on geochronology, textural and geotechnical parameters, clay minerals, and pollen analysis results. The bottom of the borehole represents an age of ~ 12 ka BP. Sediments exhibit coarsening texture upwards of the borehole, with fine mud and peat intercalations at the bottom. Six litho facies - muddy sand, sand, sandy mud, silty sand, sandy silt, and mud - were recorded. Geotechnical properties comprising moisture content, organic carbon, plasticity index record high values, whereas low bulk density associated with a low critical shear stress, are recorded. An increase in illite and to a lesser degree smectite with concomitant decrease in kaolinite is observed. Sediment texture represents a major change of depositional environment from marine to fluvial sedimentary facies during the major sea level fall i.e., after 7 ka B.P. The present sea level attained during 4-5 ka B.P; major rise of sea level has taken place from 7-11 ka BP and regression during 7 - 5 ka B.P. These transgression and regression phases introduced the changes in the environment of deposition. The monsoon was dynamic and more intense after the major fall of sea level causing the fluctuations in the fluvial facies. Upward coarsening of grain size in the borehole indicates change in sediment deposition due to increased hydrodynamic conditions and strong fluvial action, which can be linked to marine regression. Geotechnical properties suggest textural changes and sedimentary facies. An upward increase in smectite and kaolinite and decreasing illite supports major fall in sea level and also the aridity. Pollen record of sediment strata supports the paleo-environment dominated by the presence of semi-evergreen type of mangrove plants during mid- to early-Holocene times.

The effect of sudden ice sheet melt on ocean circulation and surface climate

NASA Astrophysics Data System (ADS)

Ivanovic, R. F.; Gregoire, L. J.; Wickert, A. D.; Valdes, P. J.; Burke, A.

2017-12-01

Collapse of ice sheets can cause significant sea-level rise and widespread climate change. Around 14.6 thousand years ago, global mean sea level rose by 15 m in less than 350 years during an event known as Meltwater Pulse 1a. Ice sheet modelling and sea-level fingerprinting has suggested that approximately half of this 50 mm yr-1 sea level rise may have come from a North American ice Saddle Collapse that drained into the Arctic and Atlantic Oceans. However, dating uncertainties make it difficult to determine the sequence of events and their drivers, leaving many fundamental questions. For example, was melting from the northern ice sheets responsible for the Older-Dryas or other global-scale cooling events, or did a contribution from Antarctica counteract the climatic effects? What was the role of the abrupt Bølling Warming? And how were all these signals linked to changes in Atlantic Ocean overturning circulation?To address these questions, we examined the effect of the North American ice Saddle Collapse using a high resolution network drainage model coupled to an atmosphere-ocean-vegetation General Circulation Model. Here, we present the quantitative routing estimates of the consequent meltwater discharge and its impact on climate. We also tested a suite of more idealised meltwater forcing scenarios to examine the global influence of Arctic versus Antarctic ice melt. The results show that 50% of the Saddle Collapse meltwater pulse was routed via the Mackenzie River into the Arctic Ocean, and 50% was discharged directly into the Atlantic/Gulf of Mexico. This meltwater flux, equivalent to a total of 7.3 m of sea-level rise, caused a strong (6 Sv) weakening of Atlantic Meridional Overturning Circulation (AMOC) and widespread Northern Hemisphere cooling of 1-5 °C. The greatest cooling is in the Arctic (5-10 °C in the winter), but there is also significant winter warming over eastern North America (1-3 °C). We propose that this robust submillennial mechanism was triggered by the Bølling Warming, ending the warm event and/or causing the Older Dryas cooling. Furthermore, we find that AMOC is most sensitive to meltwater discharged to the Arctic Ocean and that high-latitude northern melt overwhelms any opposing influence of Antarctic melt, which would otherwise cause northern warming.

Sea-level rise: towards understanding local vulnerability

NASA Astrophysics Data System (ADS)

Rahmstorf, Stefan

2012-06-01

Projections of global sea-level rise into the future have become more pessimistic over the past five years or so. A global rise by more than one metre by the year 2100 is now widely accepted as a serious possibility if greenhouse gas emissions continue unabated. That is witnessed by the scientific assessments that were made since the last IPCC report was published in 2007. The Delta Commission of the Dutch government projected up to 1.10 m as a 'high-end' scenario (Vellinga et al 2009). The Scientific Committee on Antarctic Research (SCAR) projected up to 1.40 m (Scientific Committee on Antarctic Research 2009), and the Arctic Monitoring and Assessment Programme (AMAP) gives a range of 0.90-1.60 m in its 2011 report (Arctic Monitoring and Assessment Programme 2011). And recently the US Army Corps of Engineers recommends using a 'low', an 'intermediate' and a 'high' scenario for global sea-level rise when planning civil works programmes, with the high one corresponding to a 1.50 m rise by 2100 (US Army Corps of Engineers 2011). This more pessimistic view is based on a number of observations, most importantly perhaps the fact that sea level has been rising at least 50% faster in the past decades than projected by the IPCC (Rahmstorf et al 2007, IPCC 2007). Also, the rate of rise (averaged over two decades) has accelerated threefold, from around 1 mm yr-1 at the start of the 20th century to around 3 mm yr-1 over the past 20 years (Church and White 2006), and this rate increase closely correlates with global warming (Rahmstorf et al 2011). The IPCC projections, which assume almost no further acceleration in the 20th century, thus look less plausible. And finally the observed net mass loss of the two big continental ice sheets (Van den Broeke et al 2011) calls into question the assumption that ice accumulation in Antarctica would largely balance ice loss from Greenland in the course of further global warming (IPCC 2007). With such a serious sea-level rise on the horizon, experts are increasingly looking at its potential impacts on coasts to facilitate local adaptation planning. This is a more complex issue than one might think, because different stretches of coast can be affected in very different ways. First of all, the sea-level response to global warming will not be globally uniform, since factors like changes in ocean currents (Levermann et al 2005) and the changing gravitational pull of continental ice (Mitrovica et al 2001) affect the local rise. Secondly, superimposed on the climatic trend is natural variability in sea level, which regionally can be as large as the climatic signal on multi-decadal timescales. Over the past decades, sea level has dropped in sizable parts of the world ocean, although it has of course risen in global mean (IPCC 2007). Thirdly, local land uplift or subsidence affects the local sea-level change relative to the coast, both for natural reasons (post-glacial isostatic adjustment centred on regions that were covered by ice sheets during the last ice age) and artificial ones (e.g., extraction of water or oil as in the Gulf of Mexico). Finally, local vulnerability to sea-level rise depends on many factors. Two interesting new studies in this journal (Tebaldi et al 2012, Strauss et al 2012) make important steps towards understanding sea-level vulnerability along the coasts of the United States, with methods that could also be applied elsewhere. The first, by Strauss and colleagues, merges high-resolution topographic data and a newly available tidal model together with population and housing data in order to estimate what land area and population would be at risk given certain increments in sea level. The results are mapped and tabulated at county and city level. They reveal the 'hot spots' along the US coast where sea-level rise is of the highest concern because of large populations living near the high-tide line: New York City and Long Island; the New Jersey shore; the Norfolk, Virginia, area; near Charleston, South Carolina; coastal cities across Florida, especially its southeast and the Tampa area; New Orleans; the San Francisco Bay Area and San Joaquin Delta; and greater Los Angeles. Overall, 3.7 million people across the US are estimated to live within 1 m of the present high-tide line. The second paper, by Tebaldi et al, specifically looks at storm surges and how their frequency is expected to change along the US coastline in the coming four decades due to rising sea levels. They first estimate future local sea-level rise relative to the land by combining the observed local trend of the past fifty years with a future acceleration due to global warming as estimated by a semi-empirical model (Vermeer and Rahmstorf 2009). Then they use past storm surge statistics for many different locations and shift the return level curves according to the projected sea-level rise. The authors find that by mid-century, in some locations what is now a once-per-century flooding event could become an annual event. Those are exceptional places—but at about a third of the sites investigated, a century flood could become a once-per-decade flood. Of course, many of these events need not have dramatic impacts: in fact, locations where rare floods are quite small in amplitude (and hence presumably modest in their impacts) are precisely those where the return period decreases most dramatically. In a place where the once-per-century flood is only 50 cm higher than the annual flood, a typical 30 cm rise in sea level makes a bigger difference than one in a place where the century flood is 2 m higher than the annual flood. Nevertheless, the expected large changes in return periods and return levels of storm surges clearly demonstrate that accounting for accelerating sea-level rise is vital in the planning and design of coastal infrastructure. But most importantly, these studies highlight the fact that the modern world, with many millions of people living right by the coast, is highly vulnerable to even modest sea-level rise. Losing just 1% of the present continental ice would raise sea level globally by about 75 cm—a tiny amount in the perspective of palaeoclimate history, e.g. the 120 m rise at the end of the last ice age, but a large amount in terms of impacts on human society. We should do everything we can to limit global warming and thereby sea-level rise to a manageable level. References Arctic Monitoring and Assessment Programme 2011 Snow, Water, Ice and Permafrost in the Arctic (Oslo: AMAP) Church J A and White N J 2006 A 20th century acceleration in global sea-level rise Geophys. Res. Lett. 33 L01602 IPCC 2007 Climate Change 2007: The Physical Science Basis. The Fourth Assessment Report of the Intergovernmental Panel on Climate Change ed S Solomon et al (Cambridge: Cambridge University Press) Levermann A, Griesel A, Hofmann M, Montoya M and Rahmstorf S 2005 Dynamic sea level changes following changes in the thermohaline circulation Clim. Dyn. 24 347-54 Mitrovica J X, Tamisiea M E, Davis J L and Milne G A 2001 Recent mass balance of polar ice sheets inferred from patterns of global sea-level change Nature 409 1026-9 Rahmstorf S, Cazenave A, Church J A, Hansen J E, Keeling R F, Parker D E and Somerville C J 2007 Recent climate observations compared to projections Science 316 709 Rahmstorf S, Perrette M and Vermeer M 2011 Testing the robustness of semi-empirical sea level projections Clim. Dyn. at press (doi:10.1007/s00382-011-1226-7) Scientific Committee on Antarctic Research 2009 Antarctic Climate Change and the Environment (Cambridge: Scott Polar Research Institute) Strauss B, Ziemlinski R, Weiss J and Overpeck J T 2012 Tidally-adjusted estimates of topographic vulnerability to sea level rise and flooding for the contiguous United States Environ. Res. Lett. 7 014033 Tebaldi C, Strauss B and Zervas C 2012 Modelling sea level rise impacts on storm surges along US coasts Environ. Res. Lett. 7 014032 US Army Corps of Engineers 2011 Sea-Level Change Considerations for Civil Works Programs (Washington, DC: Department of the Army) Van den Broeke M R, Bamber J, Lenaerts J and Rignot E 2011 Ice sheets and sea level: thinking outside the box Sur. Geophys. 32 495-505 Vellinga P, Katsman C A, Sterl A and Beersma J J 2009 Exploring high-end climate change scenarios for flood protection of the Netherlands International Scientific Assessment Carried out at the Request of the Delta Committee (De Bilt: KNMI) Vermeer M and Rahmstorf S 2009 Global sea level linked to global temperature Proc. Natl Acad. Sci. USA 106 21527-32

Sea-level change during the last 2500 years in New Jersey, USA

USGS Publications Warehouse

Kemp, Andrew C.; Horton, Benjamin P.; Vane, Christopher H.; Bernhardt, Christopher E.; Corbett, D. Reide; Engelhart, Simon E.; Anisfeld, Shimon C.; Parnell, Andrew C.; Cahill, Niamh

2013-01-01

Relative sea-level changes during the last ∼2500 years in New Jersey, USA were reconstructed to test if late Holocene sea level was stable or included persistent and distinctive phases of variability. Foraminifera and bulk-sediment δ13C values were combined to reconstruct paleomarsh elevation with decimeter precision from sequences of salt-marsh sediment at two sites using a multi-proxy approach. The additional paleoenvironmental information provided by bulk-sediment δ13C values reduced vertical uncertainty in the sea-level reconstruction by about one third of that estimated from foraminifera alone using a transfer function. The history of sediment deposition was constrained by a composite chronology. An age–depth model developed for each core enabled reconstruction of sea level with multi-decadal resolution. Following correction for land-level change (1.4 mm/yr), four successive and sustained (multi-centennial) sea-level trends were objectively identified and quantified (95% confidence interval) using error-in-variables change point analysis to account for age and sea-level uncertainties. From at least 500 BC to 250 AD, sea-level fell at 0.11 mm/yr. The second period saw sea-level rise at 0.62 mm/yr from 250 AD to 733 AD. Between 733 AD and 1850 AD, sea level fell at 0.12 mm/yr. The reconstructed rate of sea-level rise since ∼1850 AD was 3.1 mm/yr and represents the most rapid period of change for at least 2500 years. This trend began between 1830 AD and 1873 AD. Since this change point, reconstructed sea-level rise is in agreement with regional tide-gauge records and exceeds the global average estimate for the 20th century. These positive and negative departures from background rates demonstrate that the late Holocene sea level was not stable in New Jersey.

Oxygen, ecology, and the Cambrian radiation of animals

PubMed Central

Sperling, Erik A.; Frieder, Christina A.; Raman, Akkur V.; Girguis, Peter R.; Levin, Lisa A.; Knoll, Andrew H.

2013-01-01

The Proterozoic-Cambrian transition records the appearance of essentially all animal body plans (phyla), yet to date no single hypothesis adequately explains both the timing of the event and the evident increase in diversity and disparity. Ecological triggers focused on escalatory predator–prey “arms races” can explain the evolutionary pattern but not its timing, whereas environmental triggers, particularly ocean/atmosphere oxygenation, do the reverse. Using modern oxygen minimum zones as an analog for Proterozoic oceans, we explore the effect of low oxygen levels on the feeding ecology of polychaetes, the dominant macrofaunal animals in deep-sea sediments. Here we show that low oxygen is clearly linked to low proportions of carnivores in a community and low diversity of carnivorous taxa, whereas higher oxygen levels support more complex food webs. The recognition of a physiological control on carnivory therefore links environmental triggers and ecological drivers, providing an integrated explanation for both the pattern and timing of Cambrian animal radiation. PMID:23898193

Paleocene-Eocene and Plio-Pleistocene sea-level changes as "species pumps" in Southeast Asia: Evidence from Althepus spiders.

PubMed

Li, Fengyuan; Li, Shuqiang

2018-05-17

Sea-level change has been viewed as a primary driver in the formation of biodiversity. Early studies confirmed that Plio-Pleistocene sea-level changes led to the isolation and subsequent genetic differentiation of Southeast (SE) Asian organisms over short geological timescales. However, long-time consequences of sea-level fluctuations remain unclear. Herein, we analyze the evolutionary history of Althepus (spiders) whose distribution encompasses Indo-Burma and the Sunda shelf islands to understand how sea-level changes over shallow and deep timescales effected their history. Our integrative analyses, including phylogeny, divergence times, ancestral area reconstruction and diversification dynamics, reveal an intricate pattern of diversification, probably triggered by sea-level fluctuations during the Paleocene-Eocene and Plio-Pleistocene. The timing of one early divergence between the Indo-Burmese and Sundaic species coincides with late Paleocene and early Eocene high global sea levels, which induced the formation of inland seaways in the Thai-Malay Peninsula. Subsequent lowered sea levels could have provided a land bridge for its dispersal colonization across the Isthmus of Kra. Analyses suggest that Plio-Pleistocene sea-level rises contributed to recent divergence of many species. Thus, our findings cannot reject the hypothesis that sea-level changes during the Paleocene-Eocene and Plio-Pleistocene played a major role in generating biodiversity in SE Asia; sea-level changes can act as "species pumps". Copyright © 2018 Elsevier Inc. All rights reserved.

The impact of climate change on coastal ecosystems: chapter 6

USGS Publications Warehouse

Burkett, Virginia; Woodroffe, Colin D.; Nicholls, Robert J.; Forbes, Donald L.

2014-01-01

In this chapter we stress two important features of coasts and coastal ecosystems. First, these are dynamic systems which continually undergo adjustments, especially through erosion and re-deposition, in response to a range of processes. Many coastal ecosystems adjust naturally at a range of time scales and their potential for response is examined partly by reconstructing how such systems have coped with natural changes of climate and sea level in the geological past. Second, coasts have changed profoundly through the 20th Century due to the impacts of human development (such as urbanisation, port and industrial expansion, shore protection, and the draining and conversion of coastal wetlands), with these development-related drivers closely linked to a growing global population and economy. It remains a challenge to isolate the impacts of climate change and sea-level rise from either the natural trajectory of shoreline change, or the accelerated pathway resulting from other human-related stressors. There exists a danger of overstating the importance of climate change, or overlooking significant interactions of climate change with other drivers.

A 17-My-old whale constrains onset of uplift and climate change in east Africa

NASA Astrophysics Data System (ADS)

Wichura, Henry; Jacobs, Louis L.; Lin, Andrew; Polcyn, Michael J.; Manthi, Fredrick K.; Winkler, Dale A.; Strecker, Manfred R.; Clemens, Matthew

2015-03-01

Timing and magnitude of surface uplift are key to understanding the impact of crustal deformation and topographic growth on atmospheric circulation, environmental conditions, and surface processes. Uplift of the East African Plateau is linked to mantle processes, but paleoaltimetry data are too scarce to constrain plateau evolution and subsequent vertical motions associated with rifting. Here, we assess the paleotopographic implications of a beaked whale fossil (Ziphiidae) from the Turkana region of Kenya found 740 km inland from the present-day coastline of the Indian Ocean at an elevation of 620 m. The specimen is ∼17 My old and represents the oldest derived beaked whale known, consistent with molecular estimates of the emergence of modern strap-toothed whales (Mesoplodon). The whale traveled from the Indian Ocean inland along an eastward-directed drainage system controlled by the Cretaceous Anza Graben and was stranded slightly above sea level. Surface uplift from near sea level coincides with paleoclimatic change from a humid environment to highly variable and much drier conditions, which altered biotic communities and drove evolution in east Africa, including that of primates.

Construction and maintenance of the Ganges-Brahmaputra-Meghna delta: linking process, morphology, and stratigraphy.

PubMed

Wilson, Carol A; Goodbred, Steven L

2015-01-01

We present a review of the processes, morphology, and stratigraphy of the Ganges-Brahmaputra-Meghna delta (GBMD), including insights gained from detailed elevation data. The review shows that the GBMD is best characterized as a composite system, with different regions having morphologic and stratigraphic attributes of an upland fluvial fan delta; a lowland, backwater-reach delta; a downdrift tidal delta plain; and an offshore subaqueous-delta clinoform. These distinct areas of upland and lowland fluvial reaches and tidal dominance vary in time and space, and we distinguish late-Holocene phases of delta construction, maintenance, and decline similar to delta-lobe cycling in other systems. The overall stability of the GBMD landform, relative to many deltas, reflects the efficient, widespread dispersal of sediment by the large monsoon discharge and high-energy tides that affect this region. However, we do identify portions of the delta that are in decline and losing elevation relative to sea level owing to insufficient sediment delivery. These areas, some of which are well inland of the coast, represent those most at risk to the continued effect of sea-level rise.

Long and short-term atmospheric radiation analyses based on coupled measurements at high altitude remote stations and extensive air shower modeling

NASA Astrophysics Data System (ADS)

Hubert, G.; Federico, C. A.; Pazianotto, M. T.; Gonzales, O. L.

2016-02-01

In this paper are described the ACROPOL and OPD high-altitude stations devoted to characterize the atmospheric radiation fields. The ACROPOL platform, located at the summit of the Pic du Midi in the French Pyrenees at 2885 m above sea level, exploits since May 2011 some scientific equipment, including a BSS neutron spectrometer, detectors based on semiconductor and scintillators. In the framework of a IEAv and ONERA collaboration, a second neutron spectrometer was simultaneously exploited since February 2015 at the summit of the Pico dos Dias in Brazil at 1864 m above the sea level. The both high station platforms allow for investigating the long period dynamics to analyze the spectral variation of cosmic-ray- induced neutron and effects of local and seasonal changes, but also the short term dynamics during solar flare events. This paper presents long and short-term analyses, including measurement and modeling investigations considering the both high altitude stations data. The modeling approach, based on ATMORAD computational platform, was used to link the both station measurements.

A 17-My-old whale constrains onset of uplift and climate change in east Africa

PubMed Central

Wichura, Henry; Lin, Andrew; Polcyn, Michael J.; Manthi, Fredrick K.; Winkler, Dale A.; Strecker, Manfred R.; Clemens, Matthew

2015-01-01

Timing and magnitude of surface uplift are key to understanding the impact of crustal deformation and topographic growth on atmospheric circulation, environmental conditions, and surface processes. Uplift of the East African Plateau is linked to mantle processes, but paleoaltimetry data are too scarce to constrain plateau evolution and subsequent vertical motions associated with rifting. Here, we assess the paleotopographic implications of a beaked whale fossil (Ziphiidae) from the Turkana region of Kenya found 740 km inland from the present-day coastline of the Indian Ocean at an elevation of 620 m. The specimen is ∼17 My old and represents the oldest derived beaked whale known, consistent with molecular estimates of the emergence of modern strap-toothed whales (Mesoplodon). The whale traveled from the Indian Ocean inland along an eastward-directed drainage system controlled by the Cretaceous Anza Graben and was stranded slightly above sea level. Surface uplift from near sea level coincides with paleoclimatic change from a humid environment to highly variable and much drier conditions, which altered biotic communities and drove evolution in east Africa, including that of primates. PMID:25775586

Hydroclimatic variability in the Levant during the early last glacial (˜ 117-75 ka) derived from micro-facies analyses of deep Dead Sea sediments

NASA Astrophysics Data System (ADS)

Neugebauer, I.; Schwab, M. J.; Waldmann, N. D.; Tjallingii, R.; Frank, U.; Hadzhiivanova, E.; Naumann, R.; Taha, N.; Agnon, A.; Enzel, Y.; Brauer, A.

2016-01-01

The new sediment record from the deep Dead Sea basin (ICDP core 5017-1) provides a unique archive for hydroclimatic variability in the Levant. Here, we present high-resolution sediment facies analysis and elemental composition by micro-X-ray fluorescence (µXRF) scanning of core 5017-1 to trace lake levels and responses of the regional hydroclimatology during the time interval from ca. 117 to 75 ka, i.e. the transition between the last interglacial and the onset of the last glaciation. We distinguished six major micro-facies types and interpreted these and their alterations in the core in terms of relative lake level changes. The two end-member facies for highest and lowest lake levels are (a) up to several metres thick, greenish sediments of alternating aragonite and detrital marl laminae (aad) and (b) thick halite facies, respectively. Intermediate lake levels are characterised by detrital marls with varying amounts of aragonite, gypsum or halite, reflecting lower-amplitude, shorter-term variability. Two intervals of pronounced lake level drops occurred at ˜ 110-108 ± 5 and ˜ 93-87 ± 7 ka. They likely coincide with stadial conditions in the central Mediterranean (Melisey I and II pollen zones in Monticchio) and low global sea levels during Marine Isotope Stage (MIS) 5d and 5b. However, our data do not support the current hypothesis of an almost complete desiccation of the Dead Sea during the earlier of these lake level low stands based on a recovered gravel layer. Based on new petrographic analyses, we propose that, although it was a low stand, this well-sorted gravel layer may be a vestige of a thick turbidite that has been washed out during drilling rather than an in situ beach deposit. Two intervals of higher lake stands at ˜ 108-93 ± 6 and ˜ 87-75 ± 7 ka correspond to interstadial conditions in the central Mediterranean, i.e. pollen zones St. Germain I and II in Monticchio, and Greenland interstadials (GI) 24+23 and 21 in Greenland, as well as to sapropels S4 and S3 in the Mediterranean Sea. These apparent correlations suggest a close link of the climate in the Levant to North Atlantic and Mediterranean climates during the time of the build-up of Northern Hemisphere ice shields in the early last glacial period.

Potentiometric surface and water-level difference maps of selected confined aquifers in Southern Maryland and Maryland’s Eastern Shore, 1975-2015

USGS Publications Warehouse

Curtin, Stephen E.; Staley, Andrew W.; Andreasen, David C.

2016-01-01

Key Results This report presents potentiometric-surface maps of the Aquia and Magothy aquifers and the Upper Patapsco, Lower Patapsco, and Patuxent aquifer systems using water levels measured during September 2015. Water-level difference maps are also presented for these aquifers. The water-level differences in the Aquia aquifer are shown using groundwater-level data from 1982 and 2015, while the water-level differences are shown for the Magothy aquifer using data from 1975 and 2015. Water-level difference maps for both the Upper Patapsco and Lower Patapsco aquifer systems are shown using data from 1990 and 2015. The water-level differences in the Patuxent aquifer system are shown using groundwater-level data from 2007 and 2015. The potentiometric surface maps show water levels ranging from 53 feet above sea level to 164 feet below sea level in the Aquia aquifer, from 86 feet above sea level to 106 feet below sea level in the Magothy aquifer, from 115 feet above sea level to 115 feet below sea level in the Upper Patapsco aquifer system, from 106 feet above sea level to 194 feet below sea level in the Lower Patapsco aquifer system, and from 165 feet above sea level to 171 feet below sea level in the Patuxent aquifer system. Water levels have declined by as much as 116 feet in the Aquia aquifer since 1982, 99 feet in the Magothy aquifer since 1975, 66 and 83 feet in the Upper Patapsco and Lower Patapsco aquifer systems, respectively, since 1990, and 80 feet in the Patuxent aquifer system since 2007.

Relative influences of the metocean forcings on the drifting ice pack and estimation of internal ice stress gradients in the Labrador Sea

NASA Astrophysics Data System (ADS)

Turnbull, I. D.; Torbati, R. Z.; Taylor, R. S.

2017-07-01

Understanding the relative influences of the metocean forcings on the drift of sea ice floes is a crucial component to the overall characterization of an ice environment and to developing an understanding of the factors controlling the ice dynamics. In addition, estimating the magnitude of the internal stress gradients on drifting sea ice floes generated by surrounding ice cover is important for modeling operations, informing the design of offshore structures and vessels in ice environments, and for the proper calibration of Discrete Element Models (DEM) of fields of drifting ice floes. In the spring of 2015 and 2016, four sea ice floes offshore Makkovik, Labrador were tagged with satellite-linked ice tracking buoys along with one satellite-linked weather station on each floe to transmit wind speed and direction. Twenty satellite-linked Lagrangian surface ocean current tracking buoys were also deployed in the open water adjacent to the targeted ice floes. In this paper, the dynamics of the four ice floes are explored in terms of the relative proportions which were forced by the wind, current, sea surface topography, Coriolis, and internal stress gradients. The internal ice stress gradients are calculated as residuals between the observed accelerations of the floes as measured by the tracking buoys and the sums of the other metocean forcings. Results show that internal ice stress gradients accounted for up to 50% of the observed forcing on the floes, and may have reached up to around 0.19 kPa.

Decadal-timescale changes of the Atlantic overturning circulation and climate in a coupled climate model with a hybrid-coordinate ocean component

NASA Astrophysics Data System (ADS)

Persechino, A.; Marsh, R.; Sinha, B.; Megann, A. P.; Blaker, A. T.; New, A. L.

2012-08-01

A wide range of statistical tools is used to investigate the decadal variability of the Atlantic Meridional Overturning Circulation (AMOC) and associated key variables in a climate model (CHIME, Coupled Hadley-Isopycnic Model Experiment), which features a novel ocean component. CHIME is as similar as possible to the 3rd Hadley Centre Coupled Model (HadCM3) with the important exception that its ocean component is based on a hybrid vertical coordinate. Power spectral analysis reveals enhanced AMOC variability for periods in the range 15-30 years. Strong AMOC conditions are associated with: (1) a Sea Surface Temperature (SST) anomaly pattern reminiscent of the Atlantic Multi-decadal Oscillation (AMO) response, but associated with variations in a northern tropical-subtropical gradient; (2) a Surface Air Temperature anomaly pattern closely linked to SST; (3) a positive North Atlantic Oscillation (NAO)-like pattern; (4) a northward shift of the Intertropical Convergence Zone. The primary mode of AMOC variability is associated with decadal changes in the Labrador Sea and the Greenland Iceland Norwegian (GIN) Seas, in both cases linked to the tropical activity about 15 years earlier. These decadal changes are controlled by the low-frequency NAO that may be associated with a rapid atmospheric teleconnection from the tropics to the extratropics. Poleward advection of salinity anomalies in the mixed layer also leads to AMOC changes that are linked to processes in the Labrador Sea. A secondary mode of AMOC variability is associated with interannual changes in the Labrador and GIN Seas, through the impact of the NAO on local surface density.

Sea-Level Projections from the SeaRISE Initiative

NASA Technical Reports Server (NTRS)

Nowicki, Sophie; Bindschadler, Robert

2011-01-01

SeaRISE (Sea-level Response to Ice Sheet Evolution) is a community organized modeling effort, whose goal is to inform the fifth IPCC of the potential sea-level contribution from the Greenland and Antarctic ice sheets in the 21st and 22nd century. SeaRISE seeks to determine the most likely ice sheet response to imposed climatic forcing by initializing an ensemble of models with common datasets and applying the same forcing to each model. Sensitivity experiments were designed to quantify the sea-level rise associated with a change in: 1) surface mass balance, 2) basal lubrication, and 3) ocean induced basal melt. The range of responses, resulting from the multi-model approach, is interpreted as a proxy of uncertainty in our sea-level projections. http://websrv.cs .umt.edu/isis/index.php/SeaRISE_Assessment.

Steric and mass-induced Mediterranean sea level trends from 14 years of altimetry data

NASA Astrophysics Data System (ADS)

Criado-Aldeanueva, Francisco; Del Río Vera, Jorge; García-Lafuente, Jesús

2008-02-01

Long-term series of almost 14 years of altimetry data (1992-2005) have been analysed along with Sea Surface Temperature (SST) and temperature and salinity profiles to investigate sea level trends over the Mediterranean Sea. Although sea level variations are mainly driven by the steric contribution, the mass-induced component plays some role in modulating its oscillation. A spatially averaged positive trend of 2.1 ± 0.6 mm/year has been observed, but a change in sign in 2001 seems to appear. Steric effects (mainly on thermal origin) account for ˜ 55% of sea level trend. Although Mediterranean Sea is a semi-enclosed basin, this value is comparable to that reported for the global ocean. Sea level rise is particularly important in the Levantine basin south of Crete with values up to 10 ± 1 mm/year. Other areas of sea level rise are localised throughout the Levantine basin and in the Adriatic and Alboran Seas, with more moderate values. Sea level drop areas are localised in the Algerian basin, between the Balearic Islands and the African coasts and, particularly, in the Ionian basin. In this area, negative trends as high as - 10 ± 0.8 mm/year are detected mainly due to the mass-induced contribution, which suggests decadal changes of surface circulation. The inferred sea level trends have been correlated with North Atlantic Oscillation (NAO) indices and a low but significant correlation has been detected between sea level in the Levantine and Balearic basins and NAO index.

The sea-level fingerprints of ice-sheet collapse during interglacial periods

NASA Astrophysics Data System (ADS)

Hay, Carling; Mitrovica, Jerry X.; Gomez, Natalya; Creveling, Jessica R.; Austermann, Jacqueline; E. Kopp, Robert

2014-03-01

Studies of sea level during previous interglacials provide insight into the stability of polar ice sheets in the face of global climate change. Commonly, these studies correct ancient sea-level highstands for the contaminating effect of isostatic adjustment associated with past ice age cycles, and interpret the residuals as being equivalent to the peak eustatic sea level associated with excess melting, relative to present day, of ancient polar ice sheets. However, the collapse of polar ice sheets produces a distinct geometry, or fingerprint, of sea-level change, which must be accounted for to accurately infer peak eustatic sea level from site-specific residual highstands. To explore this issue, we compute fingerprints associated with the collapse of the Greenland Ice Sheet, West Antarctic Ice Sheet, and marine sectors of the East Antarctic Ice Sheet in order to isolate regions that would have been subject to greater-than-eustatic sea-level change for all three cases. These fingerprints are more robust than those associated with modern melting events, when applied to infer eustatic sea level, because: (1) a significant collapse of polar ice sheets reduces the sensitivity of the computed fingerprints to uncertainties in the geometry of the melt regions; and (2) the sea-level signal associated with the collapse will dominate the signal from steric effects. We evaluate these fingerprints at a suite of sites where sea-level records from interglacial marine isotopes stages (MIS) 5e and 11 have been obtained. Using these results, we demonstrate that previously discrepant estimates of peak eustatic sea level during MIS5e based on sea-level markers in Australia and the Seychelles are brought into closer accord.

Sea-level responses to sediment transport over the last ice age cycle

NASA Astrophysics Data System (ADS)

Ferrier, K.; Mitrovica, J. X.

2013-12-01

Sea-level changes over the last ice age cycle were instrumental in steering Earth's topographic evolution. These sea-level variations were driven by changes in surface mass loads, including not only ice and ocean mass variations but also the transfer of rock from eroding mountains to sedimentary deposits. Here we use an extended numerical model of ice age sea level (Dalca et al., 2013) to explore how sediment erosion and deposition affected global sea-level variations over the last ice age cycle. The model takes histories of ice and sediment loads as inputs, and it computes gravitationally self-consistent sea level responses by accounting for the deformational, gravitational, and rotational perturbations in the Earth's viscoelastic form. In these model simulations, we use published estimates of erosion rates, sedimentation rates, and ice sheet variations to constrain sediment and ice loading since the Last Interglacial. We explore sea-level responses to several erosional and depositional scenarios, and in each we quantify the relative contributions of crustal deformation and gravitational perturbation to the computed sea-level change. We also present a case study to illustrate the effects that sediment transfer can have on sea level at the regional scale. In particular, we focus on the region surrounding the Indus River, where fluvial sediment fluxes are among the highest on Earth. Preliminary model results suggest that sediment fluxes from Asia to the ocean are large enough to produce a significant response in sea level along the northeastern coast of the Arabian Sea. Moreover, they suggest that modeled sea-level histories are sensitive to the timing and spatial distribution of sediment erosion and deposition. For instance, sediment deposition along the continental shelf - which may have been the primary site of Indus River sediment deposition during the Holocene - produces a different sea-level response than sediment deposition on the deep-sea Indus Fan, where most of the Indus sediment may have been deposited during the glacial period preceding the Holocene. These simulations highlight the role that massive continent-to-ocean sediment fluxes can play in driving sea-level patterns over thousands of years. References: Dalca A.V., Ferrier K.L., Mitrovica J.X., Perron J.T., Milne G.A., Creveling J.R., 2013. On postglacial sea level - III: Incorporating sediment redistribution. Geophys. J. Int., doi: 10.1093/gji/ggt089.

Aeromagnetic evidence for a major strike-slip fault zone along the boundary between the Weddell Sea Rift and East Antarctica

NASA Astrophysics Data System (ADS)

Jordan, T. A.; Ferraccioli, F.; Ross, N.; Siegert, M. J.; Corr, H.; Leat, P. T.; Bingham, R. G.; Rippin, D. M.; le Brocq, A.

2012-04-01

The >500 km wide Weddell Sea Rift was a major focus for Jurassic extension and magmatism during the early stages of Gondwana break-up, and underlies the Weddell Sea Embayment, which separates East Antarctica from a collage of crustal blocks in West Antarctica. Here we present new aeromagnetic data combined with airborne radar and gravity data collected during the 2010-11 field season over the Institute and Moeller ice stream in West Antarctica. Our interpretations identify the major tectonic boundaries between the Weddell Sea Rift, the Ellsworth-Whitmore Mountains block and East Antarctica. Digitally enhanced aeromagnetic data and gravity anomalies indicate the extent of Proterozoic basement, Middle Cambrian rift-related volcanic rocks, Jurassic granites, and post Jurassic sedimentary infill. Two new joint magnetic and gravity models were constructed, constrained by 2D and 3D magnetic depth-to-source estimates to assess the extent of Proterozoic basement and the thickness of major Jurassic intrusions and post-Jurassic sedimentary infill. The Jurassic granites are modelled as 5-8 km thick and emplaced at the transition between the thicker crust of the Ellsworth-Whitmore Mountains block and the thinner crust of the Weddell Sea Rift, and within the Pagano Fault Zone, a newly identified ~75 km wide left-lateral strike-slip fault system that we interpret as a major tectonic boundary between East and West Antarctica. We also suggest a possible analogy between the Pagano Fault Zone and the Dead Sea transform. In this scenario the Jurassic Pagano Fault Zone is the kinematic link between extension in the Weddell Sea Rift and convergence across the Pacific margin of West Antarctica, as the Dead Sea transform links Red Sea extension to compression within the Zagros Mountains.

Direct evidence of warm water access to the Totten Glacier sub-ice shelf cavity

NASA Astrophysics Data System (ADS)

Orsi, A. H.; Rintoul, S. R.; Silvano, A.; van Wijk, E.; Pena-Molino, B.; Rosenberg, M. A.

2015-12-01

The Totten Glacier holds enough ice to raise global sea level by 3.5 m, is thinning according to (some) satellite data, and is grounded well below sea level on a retrograde bed and hence is potentially unstable. Basal melt driven by ocean heat flux has been linked to ice shelf thinning elsewhere in Antarctica, but no oceanographic measurements had been made near the Totten. In January 2015 the RSV Aurora Australis was the first ship to reach the Totten calving front. Observations from ship-board CTD, moorings and profiling floats provide direct confirmation that warm water reaches the ice shelf cavity. Warm water is present near the sea floor at every station deeper than 300 m depth, with maximum temperatures at mid-shelf >0.5°C. Mooring data confirm that the warm water is present year-round. A deep (>1100 m) channel at the calving front allows warm water (-0.4°C, >2°C above the local freezing point) to access the ice shelf cavity. The contrast between the oceanographic conditions near the Totten and near the Mertz Glacier is stark, although they are separated by only 30 degrees of longitude. East Antarctic ice shelves have often been assumed to behave in a similar manner and to be invulnerable to ocean change; these measurements suggest these assumptions need to be reconsidered.

Paleoclimatic signature in terrestrial flood deposits.

PubMed

Koltermann, C E; Gorelick, S M

1992-06-26

Large-scale process simulation was used to reconstruct the geologic evolution during the past 600,000 years of an alluvial fan in northern California. In order to reproduce the sedimentary record, the simulation accounted for the dynamics of river flooding, sedimentation, subsidence, land movement that resulted from faulting, and sea level changes. Paleoclimatic trends induced fluctuations in stream flows and dominated the development of the sedimentary deposits. The process simulation approach serves as a quantitative means to explore the genesis of sedimentary architecture and its link to past climatic conditions and fault motion.

The global topography mission gains momentum

USGS Publications Warehouse

Farr, Tom; Evans, Diane; Zebker, Howard; Harding, David; Bufton, Jack; Dixon, Timothy; Vetrella, S.; Gesch, Dean B.

1995-01-01

An accurate description of the surface elevation of the Earth is of fundamental importance to many branches of Earth science. Continental topographic data are required for studies of hydrology, ecology, glaciology, geomorphology, and atmospheric circulation. For example, in hydrologic and terrestrial ecosystem studies, topography exerts significant control on intercepted solar radiation, water runoff and subsurface water inventory, microclimate, vegetation type and distribution, and soil development. The topography of the polar ice caps and mountain glaciers directly reflects ice-flow dynamics and is closely linked to global climate and sea level change.

An Ongoing Shift in Pacific Ocean Sea Level

NASA Astrophysics Data System (ADS)

Cheon, S. H.; Hamlington, B.; Thompson, P. R.; Merrifield, M. A.; Nerem, R. S.; Leben, R. R.; Kim, K. Y.

2016-12-01

According to the satellite altimeter data, local sea level trends have shown considerable diversity spatially as well as temporally. In particular, dramatic changes in sea level in the Pacific have been observed throughout the altimeter record, with high trends in the western tropical Pacific (WTP) and comparatively lower trends in the eastern Pacific. In recent years, however, a shift appears to be occurring, with falling trends in the (WTP) and rising trends in the eastern tropical and northeastern Pacific (ETP and NEP). From a planning perspective, it is important to figure out whether these sharp changes are part of a short-term shift or the beginning of a longer-term change in sea level. In this study, we distinguish the origins of the recent shift in Pacific Ocean sea level. Cyclostationary empirical orthogonal function (CSEOF) analysis is applied to separate the properties of the recent sea level change in the Pacific Ocean. From the CSEOF analysis results, we point out two dominant modes of sea level shift in the Pacific Ocean. The first mode is related to the biennial oscillation associated with El Nino-Southern Oscillation (ENSO) and the other is related to lower-frequency variability with a strong signal in the northern Pacific. Considering a relatively high correlation between recent sea level change and the low-frequency mode, we suggest that the low-frequency mode has played a dominant role in the sea level shift in the Pacific Ocean. Using a reconstructed sea level dataset, we examine the variability of this low-frequency mode in the past, and find similar periods of dramatic sea level change in the Pacific. Based on the sea level record of the last five years and according to the analysis, we conclude that in the coming decades, higher sea level trends off the U.S. West Coast should be expected, while reduced trends in the WTP will likely be observed.

Effects of sediment transport and deposition on crustal loading, Earth's gravitational field, and sea level

NASA Astrophysics Data System (ADS)

Ferrier, K.; Mitrovica, J. X.; Perron, T.; Milne, G. A.; Wickert, A. D.

2012-12-01

Spatial patterns in static sea level are controlled by the interplay between the history of ice mass variations and the associated deformational, gravitational and rotational perturbations in the Earth's state. Over the last decade, there has been a renewed effort to extend classic treatments of ice-age sea-level change (Farrell and Clark, 1976) to incorporate effects such as shoreline migration due to the local onlap or offlap of seawater and changes in the extent of grounded, marine-based ice, as well as feedbacks between sea level and the orientation of Earth's rotation axis. To date, the impact of sediment transport - whether in the context of glacial processes, or other processes such as fluvial deposition - has not been incorporated into a gravitationally self-consistent sea-level theory. Here we briefly summarize the main elements of a new sea-level theory that includes sediment transport, and we apply this new theory to investigate crustal deformation and sea-level changes driven by sediment deposition on the Mississippi fan in the Gulf of Mexico. The calculations incorporate sediment transport from the start of the last glacial cycle through to the present and are constrained to conserve sediment and ocean mass. We compare relative sea level histories predicted with and without sediment transport at sites in and around the Gulf of Mexico, and we quantify the relative impacts of gravitational and deformational effects of sediment deposition. We also explore the extent to which sea-level changes associated with sediment transport impact the interpretation of paleo-sea-level records. Our new sea-level formulation provides an important component of a comprehensive coupling between sediment transfer and sea level on local, regional and global spatial scales, and on time scales extending from decades to tens of thousands of years. References: Farrell, W.E., and Clark, J.A., 1976. On postglacial sea level: Geophysical Journal of the Royal Astronomical Society, v. 46, p. 647-667.

A fractal analysis of quaternary, Cenozoic-Mesozoic, and Late Pennsylvanian sea level changes

NASA Technical Reports Server (NTRS)

Hsui, Albert T.; Rust, Kelly A.; Klein, George D.

1993-01-01

Sea level changes are related to both climatic variations and tectonic movements. The fractal dimensions of several sea level curves were compared to a modern climatic fractal dimension of 1.26 established for annual precipitation records. A similar fractal dimension (1.22) based on delta(O-18/O-16) in deep-sea sediments has been suggested to characterize climatic change during the past 2 m.y. Our analysis indicates that sea level changes over the past 150,000 to 250,000 years also exhibit comparable fractal dimensions. Sea level changes for periods longer than about 30 m.y. are found to produce fractal dimensions closer to unity and Missourian (Late Pennsylvanian) sea level changes yield a fractal dimension of 1.41. The fact that these sea level curves all possess fractal dimensions less than 1.5 indicates that sea level changes exhibit nonperiodic, long-run persistence. The different fractal dimensions calculated for the various time periods could be the result of a characteristic overprinting of the sediment recored by prevailing processes during deposition. For example, during the Quaternary, glacio-eustatic sea level changes correlate well with the present climatic signature. During the Missourian, however, mechanisms such as plate reorganization may have dominated, resulting in a significantly different fractal dimension.

Consequences of sea level variability and sea level rise for Cuban territory

NASA Astrophysics Data System (ADS)

Hernández, M.; Martínez, C. A.; Marzo, O.

2015-03-01

The objective of the present paper was to determine a first approximation of coastal zone flooding by 2100, taking into account the more persistent processes of sea level variability and non-accelerated linear sea level rise estimation to assess the main impacts. The annual linear rate of mean sea level rise in the Cuban archipelago, obtained from the longest tide gauge records, has fluctuated between 0.005 cm/year at Casilda and 0.214 cm/year at Siboney. The main sea level rise effects for the Cuban coastal zone due to climate change and global warming are shown. Monthly and annual mean sea level anomalies, some of which are similar to or higher than the mean sea level rise estimated for halfway through the present century, reinforce the inland seawater penetration due to the semi-daily high tide. The combination of these different events will result in the loss of goods and services, and require expensive investments for adaption.

Indo-Pacific sea level variability during recent decades

NASA Astrophysics Data System (ADS)

Yamanaka, G.; Tsujino, H.; Nakano, H.; Urakawa, S. L.; Sakamoto, K.

2016-12-01

Decadal variability of sea level in the Indo-Pacific region is investigated using a historical OGCM simulation. The OGCM driven by the atmospheric forcing removing long-term trends clearly exhibits decadal sea level variability in the Pacific Ocean, which is associated with eastern tropical Pacific thermal anomalies. During the period of 1977-1987, the sea level anomalies are positive in the eastern equatorial Pacific and show deviations from a north-south symmetric distribution, with strongly negative anomalies in the western tropical South Pacific. During the period of 1996-2006, in contrast, the sea level anomalies are negative in the eastern equatorial Pacific and show a nearly north-south symmetric pattern, with positive anomalies in both hemispheres. Concurrently, sea level anomalies in the south-eastern Indian Ocean vary with those in the western tropical Pacific. These sea level variations are closely related to large-scale wind fields. Indo-Pacific sea level distributions are basically determined by wind anomalies over the equatorial region as well as wind stress curl anomalies over the off-equatorial region.

Landslides: Geomorphology and Sea Cliff Hazard Potential, Santa Barbara - Isla Vista, California J.F. Klath and E.A. Keller

NASA Astrophysics Data System (ADS)

Klath, J. F.; Keller, E. A.

2015-12-01

Coastal areas are often characterized by high population densities in an ever changing, dynamic environment. The world's coasts are often dominated by steeply sloping sea cliffs, the morphology of which reflects rock type, wave erosion, and surface erosion, as well as human activities such changing vegetation, urban runoff, and construction of coastal defenses. The Santa Barbara and Goleta area, with over 17 km of sea cliffs and beaches, extends from Santa Barbara Point west to the hamlet of Isla Vista. A deeper understanding of the local geology and the physical processes generating slope failure and, thus, landward cliff retreat is important for general public safety, as well as future development and planning. Our research objective includes assessment of landslide hazard potential through investigation of previous landslides and how these events relate to various physical variables and characteristics within the surrounding bedrock. How does landslide frequency, volume, and type relate to varying local bedrock and structure? Two geologic formations dominate the sea cliffs of the Santa Barbara area: Monterey shale (upper, middle, and lower) and Monterey Sisquoc shale. Geology varies from hard cemented shale and diatomaceous, low specific gravity shale to compaction shale. Variations in landslide characteristics are linked closely to the geology of a specific site that affects how easily rock units are weathered and eroded by wave erosion, naturally occurring oil and water seeps, burnt shale events, and landslide type and frequency on steeply dipped bedding planes/daylighting beds. Naturally occurring features linked to human processes often weaken bedrock and, thus, increase the likelihood of landslides. We categorize landslide frequency, type, and triggers; location of beach access, drainage pipes, and water; and oil and tar seeps in order to develop suggestions to minimize landslide potential. Lastly, using previously published erosion cliff retreat rates and sea level rise estimates, a map displaying likely position of the coastline by 2100 will be created. This information will be useful to the county of Santa Barbara, California when considering future development and hazard mitigation plans.

Regional Sea Level Scenarios for Coastal Risk Management: Managing the Uncertainty of Future Sea Level Change and Extreme Water Levels for Department of Defense Coastal Sites Worldwide

DTIC Science & Technology

2016-04-01

SERDP NOAA USACE Ocean MANAGING THE UNCERTAINTY OF FUTURE SEA LEVEL CHANGE AND EXTREME WATER LEVELS FOR DEPARTMENT OF DEFENSE COASTAL SITES...WORLDWIDE APRIL 2016 REGIONAL SEA LEVEL SCENARIOS FOR COASTAL RISK MANAGEMENT: COVER PHOTOS, FROM LEFT TO RIGHT: - Overwash of the island of Roi-Namur on...J.A., S. Gill, J. Obeysekera, W. Sweet, K. Knuuti, and J. Marburger. 2016. Regional Sea Level Scenarios for Coastal Risk Management: Managing the

GGOS Focus Area 3: Understanding and Forecasting Sea-Level Rise and Variability

NASA Astrophysics Data System (ADS)

Schöne, Tilo; Shum, Ck; Tamisiea, Mark; Woodworth, Philip

2017-04-01

Sea level and its change have been measured for more than a century. Especially for coastal nations, deltaic regions, and coastal-oriented industries, observations of tides, tidal extremes, storm surges, and sea level rise at the interannual or longer scales have substantial impacts on coastal vulnerability towards resilience and sustainability of world's coastal regions. To date, the observed global sea level rise is largely associated with climate related changes. To find the patterns and fingerprints of those changes, and to e.g., separate the land motion from sea level signals, different monitoring techniques have been developed. Some of them are local, e.g., tide gauges, while others are global, e.g., satellite altimetry. It is well known that sea level change and land vertical motion varies regionally, and both signals need to be measured in order to quantify relative sea level at the local scale. The Global Geodetic Observing System (GGOS) and its services contribute in many ways to the monitoring of the sea level. These includes tide gauge observations, estimation of gravity changes, satellite altimetry, InSAR/Lidar, GNSS-control of tide gauges, providing ground truth sites for satellite altimetry, and importantly the maintenance of the International Reference Frame. Focus Area 3 (Understanding and Forecasting Sea-Level Rise and Variability) of GGOS establishes a platform and a forum for researchers and authorities dealing with estimating global and local sea level changes in a 10- to 30-year time span, and its project to the next century or beyond. It presents an excellent opportunity to emphasize the global, through to regional and local, importance of GGOS to a wide range of sea-level related science and practical applications. Focus Area 3 works trough demonstration projects to highlight the value of geodetic techniques to sea level science and applications. Contributions under a call for participation (http://www.ggos.org/Applications/theme3_SL.html) are welcome. The present status of GGOS Focus Area 3 will be highlighted. http://www.ggos-portal.org/lang_en/GGOS-Portal/EN/Themes/SeaLevel/seaLevel.html

Climate change impacts on tropical cyclones and extreme sea levels in the South Pacific — A regional assessment

NASA Astrophysics Data System (ADS)

Walsh, Kevin J. E.; McInnes, Kathleen L.; McBride, John L.

2012-01-01

This paper reviews the current understanding of the effect of climate change on extreme sea levels in the South Pacific region. This region contains many locations that are vulnerable to extreme sea levels in the current climate, and projections indicate that this vulnerability will increase in the future. The recent publication of authoritative statements on the relationship between global warming and global sea level rise, tropical cyclones and the El Niño-Southern Oscillation phenomenon has motivated this review. Confident predictions of global mean sea level rise are modified by regional differences in the steric (density-related) component of sea level rise and changing gravitational interactions between the ocean and the ice sheets which affect the regional distribution of the eustatic (mass-related) contribution to sea level rise. The most extreme sea levels in this region are generated by tropical cyclones. The intensity of the strongest tropical cyclones is likely to increase, but many climate models project a substantial decrease in tropical cyclone numbers in this region, which may lead to an overall decrease in the total number of intense tropical cyclones. This projection, however, needs to be better quantified using improved high-resolution climate model simulations of tropical cyclones. Future changes in ENSO may lead to large regional variations in tropical cyclone incidence and sea level rise, but these impacts are also not well constrained. While storm surges from tropical cyclones give the largest sea level extremes in the parts of this region where they occur, other more frequent high sea level events can arise from swell generated by distant storms. Changes in wave climate are projected for the tropical Pacific due to anthropogenically-forced changes in atmospheric circulation. Future changes in sea level extremes will be caused by a combination of changes in mean sea level, regional sea level trends, tropical cyclone incidence and wave climate. Recommendations are given for research to increase understanding of the response of these factors to climate change. Implications of the results for adaptation research are also discussed.

Eustatic control of turbidites and winnowed turbidites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shanmugam, G.; Moiola, R.J.

1982-05-01

Global changes in sea level, primarily the results of tectonism and glaciation, control deep-sea sedimentation. During periods of low sea level the frequency of turbidity currents is greatly increased. Episodes of low sea level also cause vigorous contour currents, which winnow away the fines of turbidites. In the rock record, the occurrence of most turbidites and winnowed turbidities closely corresponds to global lowstands of paleo-sea level. This observation may be useful in predicting the occurrence of deep-sea reservoir facies in the geologic record.

Integrated Science Investigations of the Salton Sea, California, USA

NASA Astrophysics Data System (ADS)

Barnum, D.

2006-12-01

The Salton Sea is the latest waterbody to be formed by Colorado River floodwaters within the Salton Trough. Over the past 100 years, floodwaters have been replaced by agricultural drainage water and municipal discharges so that today, most of the water reaching the Salton Sea is agricultural drainwater flowing down the New, Alamo and Whitewater Rivers. An evaporation of about 6 feet per year and inputs of more than 4 million tons of salt per year have increased salinity of the waters of the Salton Sea. The current salinity level of approximately 46 parts per thousand is about 25% more saline than ocean water. Diverting water from the Imperial Valley agricultural lands to urban Southern California, and anticipated loss of inflows from Mexico and increasing water conservation activities will result in less water flowing into the Salton Sea. A Restoration Program is being conducted to evaluate the effects of diminished inflows on the Salton Sea Ecosystem and recommend alternatives to avoid or minimize those effects. The Salton Sea has become increasingly important as habitat for migratory birds because of wetland losses. California has lost approximately 91% of interior wetland acreage from pre-settlement until the mid-1980's. The Salton Sea provides critical habitat linking distant wetlands of Pacific and Central Flyways to wintering habitats in Mexico and Central and South America. More than 400 species of birds have been observed in the Salton Sea Ecosystem. Large percentages of the populations for several bird species such as the endangered Yuma Clapper Rail, the Eared Grebe, Snowy Plover and American White Pelican utilize the Salton Sea. Approximately 20 species of conservation concern utilize the Salton Sea ecosystem. Fish-eating birds such as Great Blue Herons, California Brown Pelicans, Double-crested Cormorants and several species of egrets are highly dependent upon the fishery of the Salton Sea. The Salton Sea fishery is now primarily comprised of tilapia. However, as recently as 2001 the fishery was comprised of tilapia and 3 species of salt water fish, and was described as one of the most productive fisheries in the world. The loss of the fishery has significant consequences for the fish-eating birds and a productive sport fishing industry. Arresting salinity as a means for sustaining the fishery of the Salton Sea is a major focus for the Salton Sea Restoration Project. Other issues affecting restoration include selenium, hydrogen sulfide generating sediments, air quality issues associated with the amount of the current Salton Sea that will become dry, loss of migratory bird habitat as the lake level recedes, and loss of invertebrate communities. The USGS Salton Sea Science Office is working with state, local and tribal governments, academic institutions, and other federal agencies to develop integrated plans for evaluating nutrient dynamics, contaminants for migratory birds and human health, evaluations of various restoration alternatives, avian population dynamics, air quality related studies including sediment characterization of the Salton Sea lake bed and emissions data analysis, larval fish abundance and distribution data analysis, salinity tolerance limits for fish, and wetland habitat restoration.

Potentiometric Surface of the Lower Patapsco Aquifer in Southern Maryland, September 2007

USGS Publications Warehouse

Curtin, Stephen E.; Andreasen, David C.; Staley, Andrew W.

2009-01-01

This report presents a map showing the potentiometric surface of the lower Patapsco aquifer in the Patapsco Formation of Early Cretaceous age in Southern Maryland during September 2007. The map is based on water-level measurements in 65 wells. The highest measured water level was 111 feet above sea level near the northwestern boundary and outcrop area of the aquifer in northern Prince George's County. From this area, the potentiometric surface declined towards well fields at Severndale and Arnold. The measured ground-water levels were 87 feet below sea level at Severndale, and 42 feet below sea level at Arnold. There was also a cone of depression covering a large area in Charles County that includes Waldorf, La Plata, Indian Head, and the Morgantown power plant. The ground-water levels measured were as low as 219 feet below sea level at Waldorf, 187 feet below sea level at La Plata, 106 feet below sea level at Indian Head, and 89 feet below sea level at the Morgantown power plant.

Observed mean sea level changes around the North Sea coastline from 1800 to present

NASA Astrophysics Data System (ADS)

Wahl, T.; Haigh, I. D.; Woodworth, P. L.; Albrecht, F.; Dillingh, D.; Jensen, J.; Nicholls, R. J.; Weisse, R.; Wöppelmann, G.

2013-09-01

This paper assesses historic changes in mean sea level around the coastline of the North Sea, one of the most densely populated coasts in the world. Typically, such analyses have been conducted at a national level, and detailed geographically wider analyses have not been undertaken for about 20 years. We analyse long records (up to 200 years) from 30 tide gauge sites, which are reasonably uniformly distributed along the coastline, and: (1) calculate relative sea level trends; (2) examine the inter-annual and decadal variations; (3) estimate regional geocentric (sometimes also referred to as 'absolute') sea level rise throughout the 20th century; and (4) assess the evidence for regional acceleration of sea-level rise. Relative sea level changes are broadly consistent with known vertical land movement patterns. The inter-annual and decadal variability is partly coherent across the region, but with some differences between the Inner North Sea and the English Channel. Data sets from various sources are used to provide estimates of the geocentric sea level changes. The long-term geocentric mean sea level trend for the 1900 to 2011 period is estimated to be 1.5 ± 0.1 mm/yr for the entire North Sea region. The trend is slightly higher for the Inner North Sea (i.e. 1.6 ± 0.1 mm/yr), and smaller but not significantly different on the 95% confidence level for the English Channel (i.e. 1.2 ± 0.1 mm/yr). The uncertainties in the estimates of vertical land movement rates are still large, and the results from a broad range of approaches for determining these rates are not consistent. Periods of sea level rise acceleration are detected at different times throughout the last 200 years and are to some extent related to air pressure variations. The recent rates of sea level rise (i.e. over the last two to three decades) are high compared to the long-term average, but are comparable to those which have been observed at other times in the late 19th and 20th century.

Sea Level Changes: Determination and Effects

NASA Astrophysics Data System (ADS)

Woodworth, P. L.; Pugh, D. T.; DeRonde, J. G.; Warrick, R. G.; Hannah, J.

The measurement of sea level is of fundamental importance to a wide range of research in climatology, oceanography, geology and geodesy. This volume attempts to cover many aspects of the field. The volume opens with a description by Bolduc and Murty of one of the products stemming from the development of tide gauge networks in the northern and tropical Atlantic. This work is relevant to the growth of the Global Sea Level Observing System (GLOSS), the main goal of which is to provide the world with an efficient, coherent sea level monitoring system for océanographie and climatological research. The subsequent four papers present results from the analysis of existing tide gauge data, including those datasets available from the Permanent Service for Mean Sea Level and the TOGA Sea Level Center. Two of the four, by Wroblewski and by Pasaric and Orlic, are concerned with European sea level changes, while Yu Jiye et al. discuss inter-annual changes in the Pacific, and Wang Baocan et al. describe variability in the Changjiang estuary in China. The papers by El- Abd and A wad, on Red Sea levels, are the only contributions to the volume from the large research community of geologists concerned with sea level changes.

Seasonal Sea-Level Variations in San Francisco Bay in Response to Atmospheric Forcing, 1980

USGS Publications Warehouse

Wang, Jingyuan; Cheng, R.T.; Smith, P.C.

1997-01-01

The seasonal response of sea level in San Francisco Bay (SFB) to atmospheric forcing during 1980 is investigated. The relations between sea-level data from the Northern Reach, Central Bay and South Bay, and forcing by local wind stresses, sea level pressure (SLP), runoff and the large scale sea level pressure field are examined in detail. The analyses show that the sea-level elevations and slopes respond to the along-shore wind stress T(V) at most times of the year, and to the cross-shore wind stress T(N) during two transition periods in spring and autumn. River runoff raises the sea-level elevation during winter. It is shown that winter precipitation in the SFB area is mainly attributed to the atmospheric circulation associated with the Alcutian Low, which transports the warm, moist air into the Bay area. A multiple linear regression model is employed to estimate the independent contributions of barometric pressure and wind stress to adjusted sea level. These calculations have a simple dynamical interpretation which confirms the importance of along-shore wind to both sea level and north-south slope within the Bay.

Coastal barrier stratigraphy for Holocene high-resolution sea-level reconstruction

PubMed Central

Costas, Susana; Ferreira, Óscar; Plomaritis, Theocharis A.; Leorri, Eduardo

2016-01-01

The uncertainties surrounding present and future sea-level rise have revived the debate around sea-level changes through the deglaciation and mid- to late Holocene, from which arises a need for high-quality reconstructions of regional sea level. Here, we explore the stratigraphy of a sandy barrier to identify the best sea-level indicators and provide a new sea-level reconstruction for the central Portuguese coast over the past 6.5 ka. The selected indicators represent morphological features extracted from coastal barrier stratigraphy, beach berm and dune-beach contact. These features were mapped from high-resolution ground penetrating radar images of the subsurface and transformed into sea-level indicators through comparison with modern analogs and a chronology based on optically stimulated luminescence ages. Our reconstructions document a continuous but slow sea-level rise after 6.5 ka with an accumulated change in elevation of about 2 m. In the context of SW Europe, our results show good agreement with previous studies, including the Tagus isostatic model, with minor discrepancies that demand further improvement of regional models. This work reinforces the potential of barrier indicators to accurately reconstruct high-resolution mid- to late Holocene sea-level changes through simple approaches. PMID:27929122

Separating decadal global water cycle variability from sea level rise.

PubMed

Hamlington, B D; Reager, J T; Lo, M-H; Karnauskas, K B; Leben, R R

2017-04-20

Under a warming climate, amplification of the water cycle and changes in precipitation patterns over land are expected to occur, subsequently impacting the terrestrial water balance. On global scales, such changes in terrestrial water storage (TWS) will be reflected in the water contained in the ocean and can manifest as global sea level variations. Naturally occurring climate-driven TWS variability can temporarily obscure the long-term trend in sea level rise, in addition to modulating the impacts of sea level rise through natural periodic undulation in regional and global sea level. The internal variability of the global water cycle, therefore, confounds both the detection and attribution of sea level rise. Here, we use a suite of observations to quantify and map the contribution of TWS variability to sea level variability on decadal timescales. In particular, we find that decadal sea level variability centered in the Pacific Ocean is closely tied to low frequency variability of TWS in key areas across the globe. The unambiguous identification and clean separation of this component of variability is the missing step in uncovering the anthropogenic trend in sea level and understanding the potential for low-frequency modulation of future TWS impacts including flooding and drought.

Coastal barrier stratigraphy for Holocene high-resolution sea-level reconstruction.

PubMed

Costas, Susana; Ferreira, Óscar; Plomaritis, Theocharis A; Leorri, Eduardo

2016-12-08

The uncertainties surrounding present and future sea-level rise have revived the debate around sea-level changes through the deglaciation and mid- to late Holocene, from which arises a need for high-quality reconstructions of regional sea level. Here, we explore the stratigraphy of a sandy barrier to identify the best sea-level indicators and provide a new sea-level reconstruction for the central Portuguese coast over the past 6.5 ka. The selected indicators represent morphological features extracted from coastal barrier stratigraphy, beach berm and dune-beach contact. These features were mapped from high-resolution ground penetrating radar images of the subsurface and transformed into sea-level indicators through comparison with modern analogs and a chronology based on optically stimulated luminescence ages. Our reconstructions document a continuous but slow sea-level rise after 6.5 ka with an accumulated change in elevation of about 2 m. In the context of SW Europe, our results show good agreement with previous studies, including the Tagus isostatic model, with minor discrepancies that demand further improvement of regional models. This work reinforces the potential of barrier indicators to accurately reconstruct high-resolution mid- to late Holocene sea-level changes through simple approaches.

An improved and homogeneous altimeter sea level record from the ESA Climate Change Initiative

NASA Astrophysics Data System (ADS)

Legeais, Jean-François; Ablain, Michaël; Zawadzki, Lionel; Zuo, Hao; Johannessen, Johnny A.; Scharffenberg, Martin G.; Fenoglio-Marc, Luciana; Joana Fernandes, M.; Baltazar Andersen, Ole; Rudenko, Sergei; Cipollini, Paolo; Quartly, Graham D.; Passaro, Marcello; Cazenave, Anny; Benveniste, Jérôme

2018-02-01

Sea level is a very sensitive index of climate change since it integrates the impacts of ocean warming and ice mass loss from glaciers and the ice sheets. Sea level has been listed as an essential climate variable (ECV) by the Global Climate Observing System (GCOS). During the past 25 years, the sea level ECV has been measured from space by different altimetry missions that have provided global and regional observations of sea level variations. As part of the Climate Change Initiative (CCI) program of the European Space Agency (ESA) (established in 2010), the Sea Level project (SL_cci) aimed to provide an accurate and homogeneous long-term satellite-based sea level record. At the end of the first phase of the project (2010-2013), an initial version (v1.1) of the sea level ECV was made available to users (Ablain et al., 2015). During the second phase of the project (2014-2017), improved altimeter standards were selected to produce new sea level products (called SL_cci v2.0) based on nine altimeter missions for the period 1993-2015 (https://doi.org/10.5270/esa-sea_level_cci-1993_2015-v_2.0-201612; Legeais and the ESA SL_cci team, 2016c). Corresponding orbit solutions, geophysical corrections and altimeter standards used in this v2.0 dataset are described in detail in Quartly et al. (2017). The present paper focuses on the description of the SL_cci v2.0 ECV and associated uncertainty and discusses how it has been validated. Various approaches have been used for the quality assessment such as internal validation, comparisons with sea level records from other groups and with in situ measurements, sea level budget closure analyses and comparisons with model outputs. Compared with the previous version of the sea level ECV, we show that use of improved geophysical corrections, careful bias reduction between missions and inclusion of new altimeter missions lead to improved sea level products with reduced uncertainties on different spatial and temporal scales. However, there is still room for improvement since the uncertainties remain larger than the GCOS requirements (GCOS, 2011). Perspectives on subsequent evolution are also discussed.

Potentiometric Surface of the Lower Patapsco Aquifer in Southern Maryland, September 2009

USGS Publications Warehouse

Curtin, Stephen E.; Andreasin, David C.; Staley, Andrew W.

2010-01-01

This report presents a map showing the potentiometric surface of the lower Patapsco aquifer in the Patapsco Formation of Early Cretaceous age in Southern Maryland during September 2009. The map is based on water-level measurements in 64 wells. The highest measured water level was 110 feet above sea level near the northwestern boundary and outcrop area of the aquifer in northern Prince George's County. From this area, the potentiometric surface declined towards well fields at Severndale, Broad Creek, and Arnold. The measured groundwater levels were 99 feet below sea level at Severndale, 50 feet below sea level at Broad Creek, and 36 feet below sea level at Arnold. There was also a cone of depression in Charles County that includes Waldorf, La Plata, Indian Head, and the Morgantown power plant. The groundwater levels measured were as low as 215 feet below sea level at Waldorf, 149 feet below sea level at La Plata, 121 feet below sea level at Indian Head, and 96 feet below sea level at the Morgantown power plant. The map also shows well yield in gallons per day for 2008 at wells or well fields.

Sea level response to ENSO along the central California coast: How the 1997-1998 event compares with the historic record

USGS Publications Warehouse

Ryan, H.F.; Noble, M.

2002-01-01

Long-term monthly sea level and sea surface temperature (SST) anomalies from central California show that during winter months, positive anomalies are associated with El Nin??o events and the negative ones with La Nin??a events. There is no significant impact on monthly mean anomalies associated with Pacific decadal oscillations, although there is a tendency for more extreme events and greater variance during positive decadal oscillations. The very strong 1997-1998 El Nin??o was analyzed with respect to the long-term historic record to assess the forcing mechanisms for sea level and SST. Beginning in the spring of 1997, we observed several long-period (> 30days) fluctuations in daily sea level with amplitudes of over 10 cm at San Francisco, California. Fluctuations of poleward long-period alongshore wind stress anomalies (AWSA) are coherent with the sea level anomalies. However, the wind stress cannot entirely account for the observed sea level signals. The sea level fluctuations are also correlated with sea level fluctuations observed further south at Los Angeles and Tumaco, Columbia, which showed a poleward phase propagation of the sea level signal. We suggest that the sea level fluctuations were, to a greater degree, forced by the passage of remotely generated and coastally trapped waves that were generated along the equator and propagated to the north along the west coast of North America. However, both local and remote AWSA can significantly modulate the sea level signals. The arrival of coastally trapped waves began in the spring of 1997, which is earlier than previous strong El Nin??o events such as the 1982-1983 event. Published by Elsevier Science Ltd.

Coastal marsh response to historical and future sea-level acceleration

USGS Publications Warehouse

Kirwan, M.; Temmerman, S.

2009-01-01

We consider the response of marshland to accelerations in the rate of sea-level rise by utilizing two previously described numerical models of marsh elevation. In a model designed for the Scheldt Estuary (Belgium-SW Netherlands), a feedback between inundation depth and suspended sediment concentrations allows marshes to quickly adjust their elevation to a change in sea-level rise rate. In a model designed for the North Inlet Estuary (South Carolina), a feedback between inundation and vegetation growth allows similar adjustment. Although the models differ in their approach, we find that they predict surprisingly similar responses to sea-level change. Marsh elevations adjust to a step change in the rate of sea-level rise in about 100 years. In the case of a continuous acceleration in the rate of sea-level rise, modeled accretion rates lag behind sea-level rise rates by about 20 years, and never obtain equilibrium. Regardless of the style of acceleration, the models predict approximately 6-14 cm of marsh submergence in response to historical sea-level acceleration, and 3-4 cm of marsh submergence in response to a projected scenario of sea-level rise over the next century. While marshes already low in the tidal frame would be susceptible to these depth changes, our modeling results suggest that factors other than historical sea-level acceleration are more important for observations of degradation in most marshes today.

Projecting future sea level

USGS Publications Warehouse

Cayan, Daniel R.; Bromirski, Peter; Hayhoe, Katharine; Tyree, Mary; Dettinger, Mike; Flick, Reinhard

2006-01-01

California’s coastal observations and global model projections indicate that California’s open coast and estuaries will experience increasing sea levels over the next century. Sea level rise has affected much of the coast of California, including the Southern California coast, the Central California open coast, and the San Francisco Bay and upper estuary. These trends, quantified from a small set of California tide gages, have ranged from 10–20 centimeters (cm) (3.9–7.9 inches) per century, quite similar to that estimated for global mean sea level. So far, there is little evidence that the rate of rise has accelerated, and the rate of rise at California tide gages has actually flattened since 1980, but projections suggest substantial sea level rise may occur over the next century. Climate change simulations project a substantial rate of global sea level rise over the next century due to thermal expansion as the oceans warm and runoff from melting land-based snow and ice accelerates. Sea level rise projected from the models increases with the amount of warming. Relative to sea levels in 2000, by the 2070–2099 period, sea level rise projections range from 11–54 cm (4.3–21 in) for simulations following the lower (B1) greenhouse gas (GHG) emissions scenario, from 14–61 cm (5.5–24 in) for the middle-upper (A2) emission scenario, and from 17–72 cm (6.7–28 in) for the highest (A1fi) scenario. In addition to relatively steady secular trends, sea levels along the California coast undergo shorter period variability above or below predicted tide levels and changes associated with long-term trends. These variations are caused by weather events and by seasonal to decadal climate fluctuations over the Pacific Ocean that in turn affect the Pacific coast. Highest coastal sea levels have occurred when winter storms and Pacific climate disturbances, such as El Niño, have coincided with high astronomical tides. This study considers a range of projected future global sea level rises in examining possible impacts at California coastal and estuarine stations. Two climate models and three scenarios considered in this scenarios study provide a set of possible future weather and short-period climate fluctuations, and a range of potential long-term sea level rise values. A range of mean sea level rise was considered in combination with weather and El Niño fluctuations extracted from two global climate models and two GHG emissions scenarios. The mean sea level rise values, determined from a survey of several climate models, range from approximately 10–80 cm (3.9–31 in) between 2000 and 2100. The middle to higher end of this range would substantially exceed the historical rate of sea level rise of 15–20 cm (5.9–7.9 in)per century observed at San Francisco and San Diego during the last 100 years. Gradual sea level rise progressively worsens the impacts of high tides and the surge and waves associated with storms. The potential for impacts of future sea level rise was assessed from the occurrence of hourly sea level extremes. The occurrence of extreme events follows a sharply escalating pattern as the magnitude of future sea level rise increases. The confluence of Low barometric pressures from storms and the presence large waves at the same time substantially increases the likelihood of high, damaging sea levels along the California coast. Similarly, astronomical tides and disturbances in sea level that are caused by weather and climate fluctuations are x transmitted into the San Francisco Bay and Delta, and on into the lower reaches of the Sacramento River. In addition to elevating Bay and Delta sea levels directly through inverse barometer and wind effects, storms may generate heavy precipitation and high fresh water runoff and cause floods in the Sacramento/San Joaquin Delta, increasing the potential for inundation of levees and other structures. There may also be increased risk of levee failure due to the hydraulics and geometry of these structures. Rising sea levels from climate change will increase the frequency and duration of extreme high water levels, causing historical coastal and San Francisco Bay/Delta structure design criteria to be exceeded.

Timescales for detecting a significant acceleration in sea level rise

PubMed Central

Haigh, Ivan D.; Wahl, Thomas; Rohling, Eelco J.; Price, René M.; Pattiaratchi, Charitha B.; Calafat, Francisco M.; Dangendorf, Sönke

2014-01-01

There is observational evidence that global sea level is rising and there is concern that the rate of rise will increase, significantly threatening coastal communities. However, considerable debate remains as to whether the rate of sea level rise is currently increasing and, if so, by how much. Here we provide new insights into sea level accelerations by applying the main methods that have been used previously to search for accelerations in historical data, to identify the timings (with uncertainties) at which accelerations might first be recognized in a statistically significant manner (if not apparent already) in sea level records that we have artificially extended to 2100. We find that the most important approach to earliest possible detection of a significant sea level acceleration lies in improved understanding (and subsequent removal) of interannual to multidecadal variability in sea level records. PMID:24728012

MHC class II DRB diversity predicts antigen recognition and is associated with disease severity in California sea lions naturally infected with Leptospira interrogans

USGS Publications Warehouse

Acevedo-Whitehouse, Karina; Gulland, Frances; Bowen, Lizabeth

2018-01-01

We examined the associations between California sea lion MHC class II DRB (Zaca-DRB) configuration and diversity, and leptospirosis. As Zaca-DRB gene sequences are involved with antigen presentation of bacteria and other extracellular pathogens, we predicted that they would play a role in determining responses to these pathogenic spirochaetes. Specifically, we investigated whether Zaca-DRB diversity (number of genes) and configuration (presence of specific genes) explained differences in disease severity, and whether higher levels of Zaca-DRB diversity predicted the number of specific Leptospira interrogans serovars that a sea lion's serum would react against. We found that serum from diseased sea lions with more Zaca-DRB loci reacted against a wider array of serovars. Specific Zaca-DRB loci were linked to reactions with particular serovars. Interestingly, sea lions with clinical manifestation of leptospirosis that had higher numbers of Zaca-DRB loci were less likely to recover from disease than those with lower diversity, and those that harboured Zaca-DRB.C or –G were 4.5 to 5.3 times more likely to die from leptospirosis, regardless of the infective serovars. We propose that for leptospirosis, a disadvantage of having a wider range of antigen presentation might be increased disease severity due to immunopathology. Ours is the first study to examine the importance of Zaca-DRB diversity for antigen detection and disease severity following natural exposure to infective leptospires.

Origin of marginal basins of the NW Pacific and their plate tectonic reconstructions

NASA Astrophysics Data System (ADS)

Xu, Junyuan; Ben-Avraham, Zvi; Kelty, Tom; Yu, Ho-Shing

2014-03-01

Geometry of basins can indicate their tectonic origin whether they are small or large. The basins of Bohai Gulf, South China Sea, East China Sea, Japan Sea, Andaman Sea, Okhotsk Sea and Bering Sea have typical geometry of dextral pull-apart. The Java, Makassar, Celebes and Sulu Seas basins together with grabens in Borneo also comprise a local dextral, transform-margin type basin system similar to the central and southern parts of the Shanxi Basin in geometry. The overall configuration of the Philippine Sea resembles a typical sinistral transpressional "pop-up" structure. These marginal basins except the Philippine Sea basin generally have similar (or compatible) rift history in the Cenozoic, but there do be some differences in the rifting history between major basins or their sub-basins due to local differences in tectonic settings. Rifting kinematics of each of these marginal basins can be explained by dextral pull-apart or transtension. These marginal basins except the Philippine Sea basin constitute a gigantic linked, dextral pull-apart basin system.

Reconciliation of late Quaternary sea levels derived from coral terraces at Huon Peninsula with deep sea oxygen isotope records

NASA Astrophysics Data System (ADS)

Chappell, John; Omura, Akio; Esat, Tezer; McCulloch, Malcolm; Pandolfi, John; Ota, Yoko; Pillans, Brad

1996-06-01

A major discrepancy between the Late Quaternary sea level changes derived from raised coral reef terraces at the Huon Peninsula in Papua New Guinea and from oxygen isotopes in deep sea cores is resolved. The two methods agree closely from 120 ka to 80 ka and from 20 ka to 0 ka (ka = 1000 yr before present), but between 70 and 30 ka the isotopic sea levels are 20-40 m lower than the Huon Peninsula sea levels derived in earlier studies. New, high precision U-series age measurements and revised stratigraphic data for Huon Peninsula terraces aged between 30 and 70 ka now give similar sea levels to those based on deep sea oxygen isotope data planktonic and benthic δ 18O data. Using the sea level and deep sea isotopic data, oxygen isotope ratios are calculated for the northern continental ice sheets through the last glacial cycle and are consistent with results from Greenland ice cores. The record of ice volume changes through the last glacial cycle now appears to be reasonably complete.

The characteristics and controlling factor of the multi-stage eogenetic karst in the Longwangmiao Foramtion in Lower Cambrian, western Central Yangtze Block, SW China

NASA Astrophysics Data System (ADS)

Lu, C.

2017-12-01

This study utilized field outcrops, thin sections, geochemical data, and GR logging curves to investigate the development model of paleokarst within the Longwangmiao Formation in the Lower Cambrian, western Central Yangtze Block, SW China. The Longwangmiao Formation, which belongs to a third-order sequence, consists of four forth-order sequences and is located in the uppermost part of the Lower Cambrian. The vertical variations of the δ13C and δ18O values indicate the existence of multi-stage eogenetic karst events. The eogenetic karst event in the uppermost part of the Longwangmiao Formation is recognized by the dripstones developed within paleocaves, vertical paleoweathering crust with four zones (bedrock, a weak weathering zone, an intense weathering zone and a solution collapsed zone), two generations of calcsparite cement showing bright luminescence and a zonation from nonluminescent to bright to nonluminescent, two types breccias (matrix-rich clast-supported chaotic breccia and matrix-supported chaotic breccia) and rundkarren. The episodic variations of stratiform dissolution vugs and breccias in vertical, and facies-controlled dissolution and filling features indicated the development of multi-stages eogenetic karst. The development of the paleokarst model is controlled by multi-level sea-level changes. The long eccentricity cycle dictates the fluctuations of the forth-order sea-level, generating multi-stage eogenetic karst events. The paleokarst model is an important step towards better understanding the link between the probably orbitally forced sea-level oscillations and eogenetic karst in the Lower Cambrian. According to this paleokarst model, hydrocarbon exploration should focus on both the karst highlands and the karst transitional zone.

Effects of eustatic sea-level change, ocean dynamics, and nutrient utilization on atmospheric pCO2 and seawater composition over the last 130 000 years: a model study

NASA Astrophysics Data System (ADS)

Wallmann, K.; Schneider, B.; Sarnthein, M.

2016-02-01

We have developed and employed an Earth system model to explore the forcings of atmospheric pCO2 change and the chemical and isotopic evolution of seawater over the last glacial cycle. Concentrations of dissolved phosphorus (DP), reactive nitrogen, molecular oxygen, dissolved inorganic carbon (DIC), total alkalinity (TA), 13C-DIC, and 14C-DIC were calculated for 24 ocean boxes. The bi-directional water fluxes between these model boxes were derived from a 3-D circulation field of the modern ocean (Opa 8.2, NEMO) and tuned such that tracer distributions calculated by the box model were consistent with observational data from the modern ocean. To model the last 130 kyr, we employed records of past changes in sea-level, ocean circulation, and dust deposition. According to the model, about half of the glacial pCO2 drawdown may be attributed to marine regressions. The glacial sea-level low-stands implied steepened ocean margins, a reduced burial of particulate organic carbon, phosphorus, and neritic carbonate at the margin seafloor, a decline in benthic denitrification, and enhanced weathering of emerged shelf sediments. In turn, low-stands led to a distinct rise in the standing stocks of DIC, TA, and nutrients in the global ocean, promoted the glacial sequestration of atmospheric CO2 in the ocean, and added 13C- and 14C-depleted DIC to the ocean as recorded in benthic foraminifera signals. The other half of the glacial drop in pCO2 was linked to inferred shoaling of Atlantic meridional overturning circulation and more efficient utilization of nutrients in the Southern Ocean. The diminished ventilation of deep water in the glacial Atlantic and Southern Ocean led to significant 14C depletions with respect to the atmosphere. According to our model, the deglacial rapid and stepwise rise in atmospheric pCO2 was induced by upwelling both in the Southern Ocean and subarctic North Pacific and promoted by a drop in nutrient utilization in the Southern Ocean. The deglacial sea-level rise led to a gradual decline in nutrient, DIC, and TA stocks, a slow change due to the large size and extended residence times of dissolved chemical species in the ocean. Thus, the rapid deglacial rise in pCO2 can be explained by fast changes in ocean dynamics and nutrient utilization whereas the gradual pCO2 rise over the Holocene may be linked to the slow drop in nutrient and TA stocks that continued to promote an ongoing CO2 transfer from the ocean into the atmosphere.

Annual variation of parasite communities of deep-sea macrourid fishes from the western Mediterranean Sea and their relationship with fish diet and histopathological alterations

NASA Astrophysics Data System (ADS)

Constenla, M.; Montero, F. E.; Padrós, F.; Cartes, J. E.; Papiol, V.; Carrassón, M.

2015-10-01

Parasite communities of three abundant benthopelagic macrourid species (Hymenocephalus italicus, Nezumia aequalis and Trachyrincus scabrus) of the upper slope from the western Mediterranean were analysed seasonally. Histopathological, dietary and environmental information (temperature, salinity, O2 and turbidity) were also obtained. The three fish hosts shared only three parasite species (the nematodes Raphidascaris macrouri and Hysterothylacium aduncum and the acanthocephalan Echinorhynchus trachyrinci). H. italicus, the most benthopelagic fish, showed low parasite richness and diversity. The highest total mean abundance of parasites was found in spring for H. italicus and T. scabrus, coinciding with the highest prevalence/abundance of the majority of parasites whereas parasites of N. aequalis exhibited the highest richness, mean abundance and diversity in winter. Parasites related with benthic or infaunal preys were linked to autumn and summer samples off Besós (Barcelona). Some parasites were also linked to high turbidity, which may be due to higher abundances of the intermediate hosts, such as near-bottom zooplaktonic or suprabenthic preys. Few histopathological alterations (e.g. cysts of unknown aetiology) were observed restricted to the two most benthic-feeding fish species inhabiting more closely the near-bottom/sediment level, especially in autumn.

SWH trends and links to large scale teleconnection patterns in the Mediterranean Sea

NASA Astrophysics Data System (ADS)

Lionello, P.; Pino, C.; Galati, M. B.

2010-09-01

This study analyzes the SWH field in the Mediterranean Sea using a multidecadal simulations (1958-2001) carried out using the WAM (WAve Model) forced by the REMO-HIPOCAS wind fields. The simulations are validated against satellite altimeter data. Several mid-latitude patterns are linked to the SWH field in the Mediterranean. Considering the mean monthly SWH values, EA (Eastern Atlantic pattern) exerts the largest influence, while NAO and other patterns have a smaller but comparable effect. Severe SWH conditions have been characterized using the 95percentile of daily SWH maxima. NAO is important mainly for high SWH conditions in winter with significant correlation in December, January and March, but also EA, SCA (SCAndinavian) and EA-WR (Eastern Atlantic-Western Russia) play an important role. In general, both SWH high and mean values are modulated by several patterns, with an important variability in space and at monthly level so that no single pattern can be attributed a dominant role along the whole annual cycle and all the mentioned patterns are important for at least few months in the year. Significant trends of SWH are present only in sparse areas and suggest mostly a minor decrease of storm intensity, The statistics of extremes and high SWH values is substantially steady during the second half of the 20th century.

Pressure adaptation is linked to thermal adaptation in salt-saturated marine habitats.

PubMed

Alcaide, María; Stogios, Peter J; Lafraya, Álvaro; Tchigvintsev, Anatoli; Flick, Robert; Bargiela, Rafael; Chernikova, Tatyana N; Reva, Oleg N; Hai, Tran; Leggewie, Christian C; Katzke, Nadine; La Cono, Violetta; Matesanz, Ruth; Jebbar, Mohamed; Jaeger, Karl-Erich; Yakimov, Michail M; Yakunin, Alexander F; Golyshin, Peter N; Golyshina, Olga V; Savchenko, Alexei; Ferrer, Manuel

2015-02-01

The present study provides a deeper view of protein functionality as a function of temperature, salt and pressure in deep-sea habitats. A set of eight different enzymes from five distinct deep-sea (3040-4908 m depth), moderately warm (14.0-16.5°C) biotopes, characterized by a wide range of salinities (39-348 practical salinity units), were investigated for this purpose. An enzyme from a 'superficial' marine hydrothermal habitat (65°C) was isolated and characterized for comparative purposes. We report here the first experimental evidence suggesting that in salt-saturated deep-sea habitats, the adaptation to high pressure is linked to high thermal resistance (P value = 0.0036). Salinity might therefore increase the temperature window for enzyme activity, and possibly microbial growth, in deep-sea habitats. As an example, Lake Medee, the largest hypersaline deep-sea anoxic lake of the Eastern Mediterranean Sea, where the water temperature is never higher than 16°C, was shown to contain halopiezophilic-like enzymes that are most active at 70°C and with denaturing temperatures of 71.4°C. The determination of the crystal structures of five proteins revealed unknown molecular mechanisms involved in protein adaptation to poly-extremes as well as distinct active site architectures and substrate preferences relative to other structurally characterized enzymes. © 2014 Society for Applied Microbiology and John Wiley & Sons Ltd.

Seasonal and interannual variability of fast ice extent in the southeastern Laptev Sea between 1999 and 2013

NASA Astrophysics Data System (ADS)

Selyuzhenok, V.; Krumpen, T.; Mahoney, A.; Janout, M.; Gerdes, R.

2015-12-01

Along with changes in sea ice extent, thickness, and drift speed, Arctic sea ice regime is characterized by a decrease of fast ice season and reduction of fast ice extent. The most extensive fast ice cover in the Arctic develops in the southeastern Laptev Sea. Using weekly operational sea ice charts produced by Arctic and Antarctic Research Institute (AARI, Russia) from 1999 to 2013, we identified five main key events that characterize the annual evolution of fast ice in the southeastern Laptev Sea. Linking the occurrence of the key events with the atmospheric forcing, bathymetry, freezeup, and melt onset, we examined the processes driving annual fast ice cycle. The analysis revealed that fast ice in the region is sensitive to thermodynamic processes throughout a season, while the wind has a strong influence only on the first stages of fast ice development. The maximal fast ice extent is closely linked to the bathymetry and local topography and is primarily defined by the location of shoals, where fast ice is likely grounded. The annual fast ice cycle shows significant changes over the period of investigation, with tendencies toward later fast ice formation and earlier breakup. These tendencies result in an overall decrease of the fast ice season by 2.8 d/yr, which is significantly higher than previously reported trends.

Age related prostate-specific antigen reference range among men in south-East Caspian Sea.

PubMed

Mansourian, A R; Ghaemi, E O; Ahmadi, A R; Marjani, A; Moradi, A; Saifi, A

2007-05-01

The purpose of this study was to describe the distribution of serum prostate specific antigen (PSA) and to determine age-specific reference range in a population of Persian men. Venous blood samples were taken from 287 men, from Gorgan located in the North of Iran, South-East of Caspian Sea, aged 15 > or = 80 year. The serum PSA levels was measured using Enzyme-linked Immunosorbant-Assay (ELISA) technique and age-specific range for PSA level was determined. The serum prostate-specific antigen level for six age group of 15-40 years, 41-50 years, 51-60 years, 61-70 years, 71-80 years and >80 years were mainly in the range of 0-2.5 ng mL(-1), for 76.6%, 2.6-4 ng mL(-1) for 9.1% and as whole 85.7% of all men in this study had < or = 4 ng mL(-1), 8.7 and 5.6% all men of six age group had PSA level of 4.1-10 ng mL(-1) and >10 ng mL(-1), respectively. The findings of present study indicated that a large proportion (76.6%) men in this region have a lower PSA level of 0-2.5 ng mL(-1) and only 9.1% of men have PSA level of 2.6-4 ng mL(-1). It is therefore concluded that acceptable reference range of 0-4 ng mL(-1) for PSA level require further reassessment.

MIS 5e sea level: up to what point can we use literature reviews to answer the most pressing questions on the Last Interglacial ice sheets?

NASA Astrophysics Data System (ADS)

Rovere, A.; Raymo, M. E.

2014-12-01

During MIS 5e (between ~128 and 116 kyr BP) greenhouse gas concentrations were comparable to pre-industrial levels, summer insolation was higher by ~10% at high latitudes and polar temperatures in both hemispheres were about 3-5 °C warmer than today. Sea level (SL) at this time has been a subject of numerous studies (and some debate) with ~1000 sites with MIS 5e sea level markers recognized worldwide. Recently, Kopp et al. (Nature, 2009) and Dutton & Lambeck (Science, 2012) analyzed worldwide datasets of sea level markers pertaining to the last interglacial. After accounting for GIA, they reached similar conclusions that eustatic (i.e., globally averaged) sea level (ESL) was between +5 and +9.4 m above modern during MIS 5e. Furthermore, Kopp et al. (Nature, 2009; GJI, 2013) suggest that sea level was not uniform during the LIG, but instead underwent at least two rapid oscillations including a rapid late 5e rise first proposed by Hearty et al. (QSR, 2007) and later by O'Leary et al. (Nat. Geo., 2013). Investigating the temporal and geographic variability of MIS 5e sea level opens new lines of research, in particular the possibility to fingerprint (Hay et al., QSR, 2014) the source of the proposed rapid ice sheet collapse near the end of the Last Interglacial. In this presentation we ask: can we use a database of published sea level estimates for this purpose? To answer this question, we built a relative sea level (RSL) database using RSLcalc 2.0; this is a relational database specifically designed to review relative sea level data points while keeping all the relevant information contained in the original publications. RSlcalc allows to estimate the measurement error (on the actual elevation of the SL feature), the error on the indicative range (the elevation range occupied by a sea level indicator) as well as the reference water level (the relationship between the marker and the former sea level). We show that the majority of published data have an accuracy of few meters at best and, in most cases, are not precise enough for sea level fingerprinting. We conclude that the use of topographic-grade survey techniques is paramount in the study of paleo-sea levels and that revisiting known sites using such techniques is a priority for the understanding of polar ice volume and sea level changes during past interglacials

A 6,700 years sea-level record based on French Polynesian coral reefs

NASA Astrophysics Data System (ADS)

Hallmann, Nadine; Camoin, Gilbert; Eisenhauer, Anton; Vella, Claude; Samankassou, Elias; Botella, Albéric; Milne, Glenn; Fietzke, Jan; Dussouillez, Philippe

2015-04-01

Sea-level change during the Mid- to Late Holocene has a similar amplitude to the sea-level rise that is likely to occur before the end of the 21st century providing a unique opportunity to study the coastal response to sea-level change and to reveal an important baseline of natural climate variability prior to the industrial revolution. Mid- to Late Holocene relative sea-level change in French Polynesia was reconstructed using coral reef records from ten islands, which represent ideal settings for accurate sea-level studies because: 1) they can be regarded as tectonically stable during the relevant period (slow subsidence), 2) they are located far from former ice sheets (far-field), 3) they are characterized by a low tidal amplitude, and 4) they cover a wide range of latitudes which produces significantly improved constraints on GIA (Glacial Isostatic Adjustment) model parameters. Absolute U/Th dating of in situ coral colonies and their accurate positioning via GPS RTK (Real Time Kinematic) measurements is crucial for an accurate reconstruction of sea-level change. We focus mainly on the analysis of coral microatolls, which are sensitive low-tide recorders, as their vertical accretion is limited by the mean low water springs level. Growth pattern analysis allows the reconstruction of low-amplitude, high-frequency sea-level changes on centennial to sub-decadal time scales. A sea-level rise of less than 1 m is recorded between 6 and 3-3.5 ka, and is followed by a gradual fall in sea level that started around 2.5 ka and persisted until the past few centuries. The reconstructed sea-level curve therefore extends the Tahiti sea-level curve [Deschamps et al., 2012, Nature, 483, 559-564], and is in good agreement with a geophysical model tuned to fit far-field deglacial records [Bassett et al., 2005, Science, 309, 925-928].

Sea level history in Beringia during the past 250,000 years

USGS Publications Warehouse

Hopkins, D.M.

1973-01-01

This paper attempts to relate current knowledge of sea-level history in Beringia to the Broecker-van Donk "Termination" concept of climatic and sea-level history. The Einahnuhtan transgression is thought to represent Termination III, which according to Broecker and van Donk, took place about 225,000 y.a. The Kotzebuan transgression is thought to represent a positive fluctuation that modulated the generally falling sea level during the ensuing 100,000 yr. Sea level probably fell to about -135 m in the Bering Sea area during the maximum phase of the penultimate glaciation. The two Pelukian shorelines probably represent Termination II (about 125,000 yr BP in the Broecker-van Donk chronology) and one of the two positive fluctuations that modulated the generally falling sea level of early Wisconsinan time, about 105,000 and 80,000 y.a. according to Broecker and van Donk. Another positive modulation brought sea level to at least -20 m, about 30,000 y.a. Sea level evidently fell to between -90 and -100 m during the late Wisconsinan regression, but a substantial part of the outer Bering shelf remained submerged. Submerged shoreline features at -38m, -30 m, -24 to -20 m, and -12 to -10 m represent stillstands or slight regressions that modulated Termination I, the late Wisconsinan, and early Holocene recovery of sea level. ?? 1973.

Polar ice-sheet contributions to sea level during past warm periods

NASA Astrophysics Data System (ADS)

Dutton, A.

2015-12-01

Recent sea-level rise has been dominated by thermal expansion and glacier loss, but the contribution from mass loss from the Greenland and Antarctic ice sheets is expected to exceed other contributions under future sustained warming. Due to limitations of existing ice sheet models and the lack of relevant analogues in the historical record, projecting the timing and magnitude of polar ice sheet mass loss in the future remains challenging. One approach to improving our understanding of how polar ice-sheet retreat will unfold is to integrate observations and models of sea level, ice sheets, and climate during past intervals of warmth when the polar ice sheets contributed to higher sea levels. A recent review evaluated the evidence of polar ice sheet mass loss during several warm periods, including interglacials during the mid-Pliocene warm period, Marine Isotope Stage (MIS) 11, 5e (Last Interglacial), and 1 (Holocene). Sea-level benchmarks of ice-sheet retreat during the first of these three periods, when global mean climate was ~1 to 3 deg. C warmer than preindustrial, are useful for understanding the long-term potential for future sea-level rise. Despite existing uncertainties in these reconstructions, it is clear that our present climate is warming to a level associated with significant polar ice-sheet loss in the past, resulting in a conservative estimate for a global mean sea-level rise of 6 meters above present (or more). This presentation will focus on identifying the approaches that have yielded significant advances in terms of past sea level and ice sheet reconstruction as well as outstanding challenges. A key element of recent advances in sea-level reconstructions is the ability to recognize and quantify the imprint of geophysical processes, such as glacial isostatic adjustment (GIA) and dynamic topography, that lead to significant spatial variability in sea level reconstructions. Identifying specific ice-sheet sources that contributed to higher sea levels is a challenge that is currently hindered by limited field evidence at high latitudes. Finally, I will explore the concept of how increasing the quantity and quality of paleo sea level and ice sheet reconstructions can lead to improved quantification of contemporary changes in ice sheets and sea level.

Anthropogenic sea level rise and adaptation in the Yangtze estuary

NASA Astrophysics Data System (ADS)

Cheng, H.; Chen, J.; Chen, Z.; Ruan, R.; Xu, G.; Zeng, G.; Zhu, J.; Dai, Z.; Gu, S.; Zhang, X.; Wang, H.

2016-02-01

Sea level rise is a major projected threat of climate change. There are regional variations in sea level changes, depending on both naturally the tectonic subsidence, geomorphology, naturally changing river inputs and anthropogenic driven forces as artificial reservoir water impoundment within the watershed and urban land subsidence driven by ground water depletion in the river delta. Little is known on regional sea level fall in response to the channel erosion due to the sediment discharge decline by reservoir interception in the upstream watershed, and water level rise driven by anthropogenic measures as the land reclamation, deep waterway regulation and fresh water reservoir construction to the sea level change in estuaries. Changing coastal cities are situated in the delta regions expected to be threatened in various degrees. Shanghai belongs to those cities. Here we show that the anthropogenic driven sea level rise in the Yangtze estuary from the point of view of the continuous hydrodynamic system consisted of river catchment, estuary and coastal sea. Land subsidence is cited as 4 mm/a (2011-2030). Scour depth of the estuarine channel by upstream engineering as Three Gauge Dam is estimated at 2-10 cm (2011-2030). The rise of water level by deep waterway and land reclamation is estimated at 8-10 cm (2011-2030). The relative sea level rise will be speculated about 10 -16 cm (2011-2030), which these anthropogenic sea level changes will be imposed into the absolute sea level rise 2 mm/a and tectonic subsidence 1 mm/a measured in 1990s. The action guideline to the sea level rise strategy in the Shanghai city have been proposed to the Shanghai government as (1) recent actions (2012-2015) to upgrade the city water supply and drainage engineering and protective engineering; (2) interim actions (2016-2020) to improve sea level monitoring and early warning system, and then the special, city, regional planning considering sea level rise; (3) long term actions (2021-2030) to implement both the safety and the transformation and development of the city.

Reconstructing Mid- to Late Holocene sea-level change from coral microatolls, French Polynesia

NASA Astrophysics Data System (ADS)

Hallmann, Nadine; Camoin, Gilbert; Eisenhauer, Anton; Botella, Alberic; Milne, Glenn; Vella, Claude; Samankassou, Elias; Pothin, Virginie; Dussouillez, Philippe; Fleury, Jules; Fietzke, Jan

2017-04-01

Coral microatolls are sensitive low-tide recorders, as their vertical accretion is limited by the mean low water springs level, and can be considered therefore as high-precision recorders of sea-level change. They are of pivotal importance to resolving the rates and amplitudes of millennial-to-century scale changes during periods of relative climate stability such as the Mid- to Late Holocene, which serves as an important baseline of natural variability prior to the industrial revolution. It provides therefore a unique opportunity to study coastal response to sea-level rise, even if the rates of sea-level rise during the Mid- to Late Holocene were lower than the current rates and those expected in the near future. Mid- to Late Holocene relative sea-level change in French Polynesia was reconstructed based on the coupling between absolute U/Th dating of in situ coral microatolls and their precise positioning via GPS RTK (Real Time Kinematic) measurements. The twelve studied islands represent ideal settings for accurate sea-level studies because: 1) they can be regarded as tectonically stable during the relevant period (slow subsidence), 2) they are located far from former ice sheets (far-field), 3) they are characterized by a low tidal amplitude, and 4) they cover a wide range of latitudes which produces significantly improved constraints on GIA (Glacial Isostatic Adjustment) model parameters. A step-like sea-level rise is evidenced between 6 and 3.9 ka leading to a short sea-level highstand of about a meter in amplitude between 3.9 and 3.6 ka. A sea-level fall, at an average rate of 0.3 mm.yr-1, is recorded between 3.6 and 1.2 ka when sea level approached its present position. In addition, growth pattern analysis of coral microatolls allows the reconstruction of low-amplitude, high-frequency sea-level change on centennial to sub-decadal time scales. The reconstructed sea-level curve extends the Tahiti last deglacial sea-level curve [Deschamps et al., 2012, Nature, 483, 559-564], and is in good agreement with a geophysical model tuned to fit far-field deglacial records [Bassett et al., 2005, Science, 309, 925-928].

Precise mean sea level measurements using the Global Positioning System

NASA Technical Reports Server (NTRS)

Kelecy, Thomas M.; Born, George H.; Parke, Michael E.; Rocken, Christian

1994-01-01

This paper describes the results of a sea level measurement test conducted off La Jolla, California, in November of 1991. The purpose of this test was to determine accurate sea level measurements using a Global Positioning System (GPS) equipped buoy. These measurements were intended to be used as the sea level component for calibration of the ERS 1 satellite altimeter. Measurements were collected on November 25 and 28 when the ERS 1 satellite overflew the calibration area. Two different types of buoys were used. A waverider design was used on November 25 and a spar design on November 28. This provided the opportunity to examine how dynamic effects of the measurement platform might affect the sea level accuracy. The two buoys were deployed at locations approximately 1.2 km apart and about 15 km west of a reference GPS receiver located on the rooftop of the Institute of Geophysics and Planetary Physics at the Scripps Institute of Oceanography. GPS solutions were computed for 45 minutes on each day and used to produce two sea level time series. An estimate of the mean sea level at both locations was computed by subtracting tide gage data collected at the Scripps Pier from the GPS-determined sea level measurements and then filtering out the high-frequency components due to waves and buoy dynamics. In both cases the GPS estimate differed from Rapp's mean altimetric surface by 0.06 m. Thus, the gradient in the GPS measurements matched the gradient in Rapp's surface. These results suggest that accurate sea level can be determined using GPS on widely differing platforms as long as care is taken to determine the height of the GPS antenna phase center above water level. Application areas include measurement of absolute sea level, of temporal variations in sea level, and of sea level gradients (dominantly the geoid). Specific applications would include ocean altimeter calibration, monitoring of sea level in remote regions, and regional experiments requiring spatial and temporal resolution higher than that available from altimeter data.

Spatial variations in feeding habits and trophic levels of two small pelagic fish species in the central Mediterranean Sea.

PubMed

Rumolo, P; Bonanno, A; Barra, M; Fanelli, E; Calabrò, M; Genovese, S; Ferreri, R; Mazzola, S; Basilone, G

2016-04-01

Trophic ecology of adults of European sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) was examined and compared among various regions of central Mediterranean Sea. Carbon and nitrogen stable isotope analyses (δ(13)C and δ(15)N) were adopted as a tool to determine changes in feeding behaviour of adults of sardines and anchovies. In the study period (summer) a clear geographical pattern was recognized in the isotopic composition of both species, with an increasing trend northward. The highest variations in isotopic signal were linked to the geographical positions of the samples and, especially, between pairs of areas: South Sicily/South Campania and Gulf of Gaeta/South Elba. Higher isotope values were found in the anchovies and sardines caught in northern Tyrrhenian Sea, while lower values were mostly estimated in the southern region. Higher carbon and nitrogen isotopes may reflect a more coastal behaviour of both species, being (13)C-enriched source from benthic primary producers in addition to phytoplankton. Variations in the nitrogen isotope ratio may reflect not only differences in the trophic level of prey species, but also variations in the baseline level of food webs. Our results support the hypothesis that feeding behaviour of both species is directly or indirectly influenced by local factors, or by resource partitioning based on zooplankton size. Findings can supply knowledge needed for improving fish stock management and promoting plans able to take into account also local ecosystem analysis. Copyright © 2016 Elsevier Ltd. All rights reserved.

SRAC

Science.gov Websites

links at each of these sites. General Links AgriNet-Texas A&M Agricultural Program - Agricultural University Extension National Agricultural Statistics Service (NASS) 2013 NASS Census of Aquaculture National Agricultural Library National Fisheries Institute National Sea Grant Netvet North Central Regional Aquaculture

Assessing Flood Risk Under Sea Level Rise and Extreme Sea Levels Scenarios: Application to the Ebro Delta (Spain)

NASA Astrophysics Data System (ADS)

Sayol, J. M.; Marcos, M.

2018-02-01

This study presents a novel methodology to estimate the impact of local sea level rise and extreme surges and waves in coastal areas under climate change scenarios. The methodology is applied to the Ebro Delta, a valuable and vulnerable low-lying wetland located in the northwestern Mediterranean Sea. Projections of local sea level accounting for all contributions to mean sea level changes, including thermal expansion, dynamic changes, fresh water addition and glacial isostatic adjustment, have been obtained from regionalized sea level projections during the 21st century. Particular attention has been paid to the uncertainties, which have been derived from the spread of the multi-model ensemble combined with seasonal/inter-annual sea level variability from local tide gauge observations. Besides vertical land movements have also been integrated to estimate local relative sea level rise. On the other hand, regional projections over the Mediterranean basin of storm surges and wind-waves have been used to evaluate changes in extreme events. The compound effects of surges and extreme waves have been quantified using their joint probability distributions. Finally, offshore sea level projections from extreme events superimposed to mean sea level have been propagated onto a high resolution digital elevation model of the study region in order to construct flood hazards maps for mid and end of the 21st century and under two different climate change scenarios. The effect of each contribution has been evaluated in terms of percentage of the area exposed to coastal hazards, which will help to design more efficient protection and adaptation measures.

PHYSIOLOGICAL ECOLOGY OF CLOSTRIDIUM GLYCOLICUM RD-1, AN AEROTOLERANT ACETOGEN ISOLATED FROM SEA GRASS ROOTS

EPA Science Inventory

An anaerobic, H2-utilizing bacterium, strain RD-1, was isolated from the highest growth-positive dilution series of a root homogenate prepared from the sea grass Halodule wrightii. Cells of RD-1 were gram-positive, spore-forming, motile rods that were linked by connecting filamen...

On the relationship between sea level and Spartina alterniflora production

USGS Publications Warehouse

Kirwan, Matthew L.; Christian, Robert R.; Blum, Linda K.; Brinson, Mark M.

2012-01-01

A positive relationship between interannual sea level and plant growth is thought to stabilize many coastal landforms responding to accelerating rates of sea level rise. Numerical models of delta growth, tidal channel network evolution, and ecosystem resilience incorporate a hump-shaped relationship between inundation and plant primary production, where vegetation growth increases with sea level up to an optimum water depth or inundation frequency. In contrast, we use decade-long measurements of Spartina alterniflora biomass in seven coastal Virginia (USA) marshes to demonstrate that interannual sea level is rarely a primary determinant of vegetation growth. Although we find tepid support for a hump-shaped relationship between aboveground production and inundation when marshes of different elevation are considered, our results suggest that marshes high in the intertidal zone and low in relief are unresponsive to sea level fluctuations. We suggest existing models are unable to capture the behavior of wetlands in these portions of the landscape, and may underestimate their vulnerability to sea level rise because sea level rise will not be accompanied by enhanced plant growth and resultant sediment accumulation.

Committed sea-level rise under the Paris Agreement and the legacy of delayed mitigation action.

PubMed

Mengel, Matthias; Nauels, Alexander; Rogelj, Joeri; Schleussner, Carl-Friedrich

2018-02-20

Sea-level rise is a major consequence of climate change that will continue long after emissions of greenhouse gases have stopped. The 2015 Paris Agreement aims at reducing climate-related risks by reducing greenhouse gas emissions to net zero and limiting global-mean temperature increase. Here we quantify the effect of these constraints on global sea-level rise until 2300, including Antarctic ice-sheet instabilities. We estimate median sea-level rise between 0.7 and 1.2 m, if net-zero greenhouse gas emissions are sustained until 2300, varying with the pathway of emissions during this century. Temperature stabilization below 2 °C is insufficient to hold median sea-level rise until 2300 below 1.5 m. We find that each 5-year delay in near-term peaking of CO 2 emissions increases median year 2300 sea-level rise estimates by ca. 0.2 m, and extreme sea-level rise estimates at the 95th percentile by up to 1 m. Our results underline the importance of near-term mitigation action for limiting long-term sea-level rise risks.

Understanding the interactions between Social Capital, climate change, and community resilience in Gulf of Mexico coastal counties

NASA Astrophysics Data System (ADS)

Young, C.; Blomberg, B.; Kolker, A.; Nguyen, U.; Page, C. M.; Sherchan, S. P.; Tobias, V. D.; Wu, H.

2017-12-01

Coastal communities in the Gulf of Mexico are facing new and complex challenges as their physical environment is altered by climate warming and sea level rise. To effectively prepare for environmental changes, coastal communities must build resilience in both physical structures and social structures. One measure of social structure resilience is how much social capital a community possesses. Social capital is defined as the connections among individuals which result in networks with shared norms, values and understandings that facilitate cooperation within or among groups. Social capital exists in three levels; bonding, bridging and linking. Bonding social capital is a measure of the strength of relationships amongst members of a network who are similar in some form. Bridging social capital is a measure of relationships amongst people who are dissimilar in some way, such as age, education, or race/ethnicity. Finally Linking social capital measures the extent to which individuals build relationships with institutions and individuals who have relative power over them (e.g local government, educational institutions). Using census and American Community Survey data, we calculated a Social Capital index value for bonding, bridging and linking for 60 Gulf of Mexico coastal counties for the years 2000, and 2010 to 2015. To investigate the impact of social capital on community resilience we coupled social capital index values with physical datasets of land-use/land cover, sea level change, climate, elevation and surface water quality for each coastal county in each year. Preliminary results indicate that in Gulf of Mexico coastal counties, increased bonding social capital results in decreased population change. In addition, we observed a multi-year time lag in the effect of increased bridging social capital on population stability, potentially suggesting key linkages between the physical and social environment in this complex coupled-natural human system. This transdisciplinary study integrated physical and social open science data and provides a better understanding on how increased social capital improves resilience to changes in the physical environment. Thus, by investing in social capital, local governments may have a low cost and non-structural way of increasing community resilience.

Future sea level rise constrained by observations and long-term commitment.

PubMed

Mengel, Matthias; Levermann, Anders; Frieler, Katja; Robinson, Alexander; Marzeion, Ben; Winkelmann, Ricarda

2016-03-08

Sea level has been steadily rising over the past century, predominantly due to anthropogenic climate change. The rate of sea level rise will keep increasing with continued global warming, and, even if temperatures are stabilized through the phasing out of greenhouse gas emissions, sea level is still expected to rise for centuries. This will affect coastal areas worldwide, and robust projections are needed to assess mitigation options and guide adaptation measures. Here we combine the equilibrium response of the main sea level rise contributions with their last century's observed contribution to constrain projections of future sea level rise. Our model is calibrated to a set of observations for each contribution, and the observational and climate uncertainties are combined to produce uncertainty ranges for 21st century sea level rise. We project anthropogenic sea level rise of 28-56 cm, 37-77 cm, and 57-131 cm in 2100 for the greenhouse gas concentration scenarios RCP26, RCP45, and RCP85, respectively. Our uncertainty ranges for total sea level rise overlap with the process-based estimates of the Intergovernmental Panel on Climate Change. The "constrained extrapolation" approach generalizes earlier global semiempirical models and may therefore lead to a better understanding of the discrepancies with process-based projections.

Sea-level Variation Along the Suez Canal

NASA Astrophysics Data System (ADS)

Eid, F. M.; Sharaf El-Din, S. H.; Alam El-Din, K. A.

1997-05-01

The variation of sea level at 11 stations distributed along the Suez Canal was studied during the period from 1980 to 1986. The ranges of variation in daily mean sea level at Port Said and Port Tawfik are about 60 and 120 cm, respectively. The minimum range of daily variation is at Kantara (47 cm). The fluctuations of the monthly mean sea level between the two ends of the Suez Canal vary from one season to another. From July to December, the sea level at Port Said is higher than that at Port Tawfik, with the maximum difference (10·5 cm) in September. During the rest of the year, the mean sea level at Port Tawfik is higher than that at Port Said, with the maximum difference (31·5 cm) in March. The long-term variations of the annual mean sea level at both Port Said and Port Tawfik for the period from 1923 to 1986 showed a positive trend. The sea level at Port Said increased by about 27·8 cm century -1while it increased by only 9·1 cm century -1at Port Tawfik. This indicates that the difference between sea level at Port Said and Port Tawfik has decreased with time.

Future sea level rise constrained by observations and long-term commitment

PubMed Central

Mengel, Matthias; Levermann, Anders; Frieler, Katja; Robinson, Alexander; Marzeion, Ben; Winkelmann, Ricarda

2016-01-01

Sea level has been steadily rising over the past century, predominantly due to anthropogenic climate change. The rate of sea level rise will keep increasing with continued global warming, and, even if temperatures are stabilized through the phasing out of greenhouse gas emissions, sea level is still expected to rise for centuries. This will affect coastal areas worldwide, and robust projections are needed to assess mitigation options and guide adaptation measures. Here we combine the equilibrium response of the main sea level rise contributions with their last century's observed contribution to constrain projections of future sea level rise. Our model is calibrated to a set of observations for each contribution, and the observational and climate uncertainties are combined to produce uncertainty ranges for 21st century sea level rise. We project anthropogenic sea level rise of 28–56 cm, 37–77 cm, and 57–131 cm in 2100 for the greenhouse gas concentration scenarios RCP26, RCP45, and RCP85, respectively. Our uncertainty ranges for total sea level rise overlap with the process-based estimates of the Intergovernmental Panel on Climate Change. The “constrained extrapolation” approach generalizes earlier global semiempirical models and may therefore lead to a better understanding of the discrepancies with process-based projections. PMID:26903648

Sea level oscillations over minute timescales: a global perspective

NASA Astrophysics Data System (ADS)

Vilibic, Ivica; Sepic, Jadranka

2016-04-01

Sea level oscillations occurring over minutes to a few hours are an important contributor to sea level extremes, and a knowledge on their behaviour is essential for proper quantification of coastal marine hazards. Tsunamis, meteotsunamis, infra-gravity waves and harbour oscillations may even dominate sea level extremes in certain areas and thus pose a great danger for humans and coastal infrastructure. Aside for tsunamis, which are, due to their enormous impact to the coastlines, a well-researched phenomena, the importance of other high-frequency oscillations to the sea level extremes is still underrated, as no systematic long-term measurements have been carried out at a minute timescales. Recently, Intergovernmental Oceanographic Commission (IOC) established Sea Level Monitoring Facility portal (http://www.ioc-sealevelmonitoring.org), making 1-min sea level data publicly available for several hundred tide gauge sites in the World Ocean. Thereafter, a global assessment of oscillations over tsunami timescales become possible; however, the portal contains raw sea level data only, being unchecked for spikes, shifts, drifts and other malfunctions of instruments. We present a quality assessment of these data, estimates of sea level variances and contributions of high-frequency processes to the extremes throughout the World Ocean. This is accompanied with assessment of atmospheric conditions and processes which generate intense high-frequency oscillations.

Analysis of Sea Level Rise in Singapore Strait

NASA Astrophysics Data System (ADS)

Tkalich, Pavel; Luu, Quang-Hung

2013-04-01

Sea level in Singapore Strait is governed by various scale phenomena, from global to local. Global signals are dominated by the climate change and multi-decadal variability and associated sea level rise; at regional scale seasonal sea level variability is caused by ENSO-modulated monsoons; locally, astronomic tides are the strongest force. Tide gauge records in Singapore Strait are analyzed to derive local sea level trend, and attempts are made to attribute observed sea level variability to phenomena at various scales, from global to local. It is found that at annual scale, sea level anomalies in Singapore Strait are quasi-periodic, of the order of ±15 cm, the highest during northeast monsoon and the lowest during southwest monsoon. Interannual regional sea level falls are associated with El Niño events, while the rises are related to La Niña episodes; both variations are in the range of ±9 cm. At multi-decadal scale, sea level in Singapore Strait has been rising at the rate 1.2-1.9 mm/year for the period 1975-2009, 2.0±0.3 mm/year for 1984-2009, and 1.3-4.7 mm/year for 1993-2009. When compared with the respective global trends of 2.0±0.3, 2.4, and 2.8±0.8 mm/year, Singapore Strait sea level rise trend was weaker at the earlier period and stronger at the recent decade.

Keep up or drown: adjustment of western Pacific coral reefs to sea-level rise in the 21st century

PubMed Central

van Woesik, R.; Golbuu, Y.; Roff, G.

2015-01-01

Since the Mid-Holocene, some 5000 years ago, coral reefs in the Pacific Ocean have been vertically constrained by sea level. Contemporary sea-level rise is releasing these constraints, providing accommodation space for vertical reef expansion. Here, we show that Porites microatolls, from reef-flat environments in Palau (western Pacific Ocean), are ‘keeping up’ with contemporary sea-level rise. Measurements of 570 reef-flat Porites microatolls at 10 locations around Palau revealed recent vertical skeletal extension (78±13 mm) over the last 6–8 years, which is consistent with the timing of the recent increase in sea level. We modelled whether microatoll growth rates will potentially ‘keep up’ with predicted sea-level rise in the near future, based upon average growth, and assuming a decline in growth for every 1°C increase in temperature. We then compared these estimated extension rates with rates of sea-level rise under four Representative Concentration Pathways (RCPs). Our model suggests that under low–mid RCP scenarios, reef-coral growth will keep up with sea-level rise, but if greenhouse gas concentrations exceed 670 ppm atmospheric CO2 levels and with +2.2°C sea-surface temperature by 2100 (RCP 6.0 W m−2), our predictions indicate that Porites microatolls will be unable to keep up with projected rates of sea-level rise in the twenty-first century. PMID:26587277

The effect of regional sea level atmospheric pressure on sea level variations at globally distributed tide gauge stations with long records

NASA Astrophysics Data System (ADS)

Iz, H. Bâki

2018-05-01

This study provides additional information about the impact of atmospheric pressure on sea level variations. The observed regularity in sea level atmospheric pressure depends mainly on the latitude and verified to be dominantly random closer to the equator. It was demonstrated that almost all the annual and semiannual sea level variations at 27 globally distributed tide gauge stations can be attributed to the regional/local atmospheric forcing as an inverted barometric effect. Statistically significant non-linearities were detected in the regional atmospheric pressure series, which in turn impacted other sea level variations as compounders in tandem with the lunar nodal forcing, generating lunar sub-harmonics with multidecadal periods. It was shown that random component of regional atmospheric pressure tends to cluster at monthly intervals. The clusters are likely to be caused by the intraannual seasonal atmospheric temperature changes,which may also act as random beats in generating sub-harmonics observed in sea level changes as another mechanism. This study also affirmed that there are no statistically significant secular trends in the progression of regional atmospheric pressures, hence there was no contribution to the sea level trends during the 20th century by the atmospheric pressure.Meanwhile, the estimated nonuniform scale factors of the inverted barometer effects suggest that the sea level atmospheric pressure will bias the sea level trends inferred from satellite altimetry measurements if their impact is accounted for as corrections without proper scaling.

The social values at risk from sea-level rise

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graham, Sonia, E-mail: sonia.graham@unimelb.edu.au; Barnett, Jon, E-mail: jbarn@unimelb.edu.au; Fincher, Ruth, E-mail: r.fincher@unimelb.edu.au

Analysis of the risks of sea-level rise favours conventionally measured metrics such as the area of land that may be subsumed, the numbers of properties at risk, and the capital values of assets at risk. Despite this, it is clear that there exist many less material but no less important values at risk from sea-level rise. This paper re-theorises these multifarious social values at risk from sea-level rise, by explaining their diverse nature, and grounding them in the everyday practices of people living in coastal places. It is informed by a review and analysis of research on social values frommore » within the fields of social impact assessment, human geography, psychology, decision analysis, and climate change adaptation. From this we propose that it is the ‘lived values’ of coastal places that are most at risk from sea-level rise. We then offer a framework that groups these lived values into five types: those that are physiological in nature, and those that relate to issues of security, belonging, esteem, and self-actualisation. This framework of lived values at risk from sea-level rise can guide empirical research investigating the social impacts of sea-level rise, as well as the impacts of actions to adapt to sea-level rise. It also offers a basis for identifying the distribution of related social outcomes across populations exposed to sea-level rise or sea-level rise policies.« less

The land-ice contribution to 21st-century dynamic sea level rise

NASA Astrophysics Data System (ADS)

Howard, T.; Ridley, J.; Pardaens, A. K.; Hurkmans, R. T. W. L.; Payne, A. J.; Giesen, R. H.; Lowe, J. A.; Bamber, J. L.; Edwards, T. L.; Oerlemans, J.

2014-06-01

Climate change has the potential to influence global mean sea level through a number of processes including (but not limited to) thermal expansion of the oceans and enhanced land ice melt. In addition to their contribution to global mean sea level change, these two processes (among others) lead to local departures from the global mean sea level change, through a number of mechanisms including the effect on spatial variations in the change of water density and transport, usually termed dynamic sea level changes. In this study, we focus on the component of dynamic sea level change that might be given by additional freshwater inflow to the ocean under scenarios of 21st-century land-based ice melt. We present regional patterns of dynamic sea level change given by a global-coupled atmosphere-ocean climate model forced by spatially and temporally varying projected ice-melt fluxes from three sources: the Antarctic ice sheet, the Greenland Ice Sheet and small glaciers and ice caps. The largest ice melt flux we consider is equivalent to almost 0.7 m of global mean sea level rise over the 21st century. The temporal evolution of the dynamic sea level changes, in the presence of considerable variations in the ice melt flux, is also analysed. We find that the dynamic sea level change associated with the ice melt is small, with the largest changes occurring in the North Atlantic amounting to 3 cm above the global mean rise. Furthermore, the dynamic sea level change associated with the ice melt is similar regardless of whether the simulated ice fluxes are applied to a simulation with fixed CO2 or under a business-as-usual greenhouse gas warming scenario of increasing CO2.

Reply to comment by E. Bard et al. on "Younger Dryas sea level and meltwater pulse 1B recorded in Barbados reef crest coral Acropora palmata" by N. A. Abdul et al.

NASA Astrophysics Data System (ADS)

Mortlock, Richard A.; Abdul, Nicole A.; Wright, James D.; Fairbanks, Richard G.

2016-12-01

Abdul et al. (2016) presented a detailed record of sea level at Barbados (13.9-9 kyr B.P.) tightly constraining the timing and amplitude during the Younger Dryas and Meltwater Pulse 1B (MWP-1B) based on U-Th dated reef crest coral species Acropora palmata. The Younger Dryas slow stand and the large (14 m) rapid sea level jump are not resolved in the Tahiti record. Tahiti sea level estimates are remarkably close to the Barbados sea level curve between 13.9 and 11.6 kyr but fall below the Barbados sea level curve for a few thousand years following MWP-1B. By 9 kyr the Tahiti sea level estimates again converge with the Barbados sea level curve. Abdul et al. (2016) concluded that Tahiti reefs at the core sites did not keep up with intervals of rapidly rising sea level during MWP-1B. We counter Bard et al. (2016) by showing (1) that there is no evidence for a hypothetical fault in Oistins Bay affecting one of the Barbados coring locations, (2) that the authors confuse the rare occurrences of A. palmata at depths >5 m with the "thickets" of A. palmata fronds representing the reef-crest facies, and (3) that uncertainties in depth habitat proxies largely account for differences in Barbados and Tahiti sea level differences curves with A. palmata providing the most faithful proxy. Given the range in Tahiti paleodepth uncertainties at the cored sites, the most parsimonious explanation remains that Tahiti coralgal ridges did not keep up with the sea level rise of MWP-1B.

Earth's Constant Mean Elevation: Implication for Long-Term Sea Level and Controlled by Ocean Lithosphere Dynamics in a Pitman World

NASA Astrophysics Data System (ADS)

Rowley, David

2017-04-01

On a spherical Earth, the mean elevation ( -2440m) would be everywhere at a mean Earth radius from the center. This directly links an elevation at the surface to physical dimensions of the Earth, including surface area and volume that are at most very slowly evolving components of the Earth system. Earth's mean elevation thus provides a framework within which to consider changes in heights of Earth's solid surface as a function of time. In this paper the focus will be on long-term, non-glacially controlled sea level. Long-term sea level has long been argued to be largely controlled by changes in ocean basin volume related to changes in area-age distribution of oceanic lithosphere. As generally modeled by Pitman (1978) and subsequent workers, the age-depth relationship of oceanic lithosphere, including both the ridge depth and coefficients describing the age-depth relationship are assumed constant. This paper examines the consequences of adhering to these assumptions when placed within the larger framework of maintaining a constant mean radius of the Earth. Self-consistent estimates of long-term sea level height and changes in mean depth of the oceanic crust are derived from the assumption that the mean elevation and corresponding mean radius are unchanging aspects of Earth's shorter-term evolution. Within this context, changes in mean depth of the oceanic crust, corresponding with changes in mean age of the oceanic lithosphere, acting over the area of the oceanic crust represent a volume change that is required to be balanced by a compensating equal but opposite volume change under the area of the continental crust. Models of paleo-cumulative hypsometry derived from a starting glacial isostatic adjustment (GIA)-corrected ice-free hypsometry that conserve mean elevation provide a basis for understanding how these compensating changes impact global hypsometry and particularly estimates of global mean shoreline height. Paleo-shoreline height and areal extent of flooding can be defined as the height and corresponding cumulative area of the solid surface of the Earth at which the integral of area as a function of elevation, from the maximum depth upwards, equals the volume of ocean water filling it with respect to cumulative paleo-hypsometry. Present height of the paleo-shoreline is the height on the GIA-corrected cumulative hypsometry at an area equal to the areal extent of flooding. Paleogeographic estimates of global extent of ocean flooding from the Middle Jurassic to end Eocene, when combined with conservation of mean elevation and ocean water volume allow an explicit estimate of the paleo-height and present height of the paleo-shoreline. The best-fitting estimate of present height of the paleo-shoreline, equivalent to a long-term "eustatic" sea level curve, implies very modest (25±22m) changes in long-term sea level above the ice-free sea level height of +40m. These, in turn, imply quite limited changes in mean depth of the oceanic crust (15±11m), and mean age of the oceanic lithosphere ( 62.1±2.4 my) since the Middle Jurassic.

Coastal Hazards Maps: Actionable Information for Communities Facing Sea-Level Rise (Invited)

NASA Astrophysics Data System (ADS)

Gibeaut, J. C.; Barraza, E.

2010-12-01

Barrier islands along the U.S. Gulf coast remain under increasing pressure from development. This development and redevelopment is occurring despite recent hurricanes, ongoing erosion, and sea-level rise. To lessen the impacts of these hazards, local governments need information in a form that is useful for informing the public, making policy, and enforcing development rules. We recently completed the Galveston Island Geohazards Map for the city of Galveston, Texas and are currently developing maps for the Mustang and South Padre Island communities. The maps show areas that vary in their susceptibility to, and function for, mitigating the effects of geological processes, including sea-level rise, land subsidence, erosion and storm-surge flooding and washover. The current wetlands, beaches and dunes are mapped as having the highest geohazard potential both in terms of their exposure to hazardous conditions and their mitigating effects of those hazards for the rest of the island. These existing “critical environments” are generally protected under existing regulations. Importantly, however, the mapping recognizes that sea-level rise and shoreline retreat are changing the island; therefore, 60-year model projections of the effects of these changes are incorporated into the map. The areas that we project will become wetlands, beaches and dunes in the next 60 years are not protected. These areas are the most difficult to deal with from a policy point of view, yet we must address what happens there if real progress is to be made in how we live with sea-level rise. The geohazards maps draw on decades of geological knowledge of how barrier islands behave and put it in a form that is intuitive to the public and directly useful to planners. Some of the “messages” in the map include: leave salt marshes alone and give them room to migrate inland as sea level rises; set back and move development away from the shoreline to provide space for beaches and protective dunes to form; and steer away from particularly low and unprotected areas subject to flooding and washover. Probably most barrier island stakeholders have heard these messages before. The difference a map makes is that it is a tangible link from our knowledge to the issues on the ground. To increase the likelihood that the maps will be considered, we took some practical approaches. The projections for change incorporated into the maps do not include effects of increasing rates of sea-level rise as projected by global climate change studies. It would be a shame if our efforts to improve how we live along the shore were caught up in the ongoing debate of global warming and the mapping results neutralized. Instead, all we are asking is for people to look at what we have observed during the past 50 to 100 years, project that just 60 years into the future, add more people to the islands and then realize we need to start doing things differently. Furthermore, the projections are made for just 60 years because this is a timescale people often plan for in their personal lives, and because it is a period where our methods for projection are most reliable.

Recent increases in Arctic freshwater flux affects Labrador Sea convection and Atlantic overturning circulation

NASA Astrophysics Data System (ADS)

Yang, Qian; Dixon, Timothy H.; Myers, Paul G.; Bonin, Jennifer; Chambers, Don; van den Broeke, M. R.

2016-01-01

The Atlantic Meridional Overturning Circulation (AMOC) is an important component of ocean thermohaline circulation. Melting of Greenland's ice sheet is freshening the North Atlantic; however, whether the augmented freshwater flux is disrupting the AMOC is unclear. Dense Labrador Sea Water (LSW), formed by winter cooling of saline North Atlantic water and subsequent convection, is a key component of the deep southward return flow of the AMOC. Although LSW formation recently decreased, it also reached historically high values in the mid-1990s, making the connection to the freshwater flux unclear. Here we derive a new estimate of the recent freshwater flux from Greenland using updated GRACE satellite data, present new flux estimates for heat and salt from the North Atlantic into the Labrador Sea and explain recent variations in LSW formation. We suggest that changes in LSW can be directly linked to recent freshening, and suggest a possible link to AMOC weakening.

Recent increases in Arctic freshwater flux affects Labrador Sea convection and Atlantic overturning circulation.

PubMed

Yang, Qian; Dixon, Timothy H; Myers, Paul G; Bonin, Jennifer; Chambers, Don; van den Broeke, M R

2016-01-22

The Atlantic Meridional Overturning Circulation (AMOC) is an important component of ocean thermohaline circulation. Melting of Greenland's ice sheet is freshening the North Atlantic; however, whether the augmented freshwater flux is disrupting the AMOC is unclear. Dense Labrador Sea Water (LSW), formed by winter cooling of saline North Atlantic water and subsequent convection, is a key component of the deep southward return flow of the AMOC. Although LSW formation recently decreased, it also reached historically high values in the mid-1990s, making the connection to the freshwater flux unclear. Here we derive a new estimate of the recent freshwater flux from Greenland using updated GRACE satellite data, present new flux estimates for heat and salt from the North Atlantic into the Labrador Sea and explain recent variations in LSW formation. We suggest that changes in LSW can be directly linked to recent freshening, and suggest a possible link to AMOC weakening.

Combining Probability Distributions of Wind Waves and Sea Level Variations to Assess Return Periods of Coastal Floods

NASA Astrophysics Data System (ADS)

Leijala, U.; Bjorkqvist, J. V.; Pellikka, H.; Johansson, M. M.; Kahma, K. K.

2017-12-01

Predicting the behaviour of the joint effect of sea level and wind waves is of great significance due to the major impact of flooding events in densely populated coastal regions. As mean sea level rises, the effect of sea level variations accompanied by the waves will be even more harmful in the future. The main challenge when evaluating the effect of waves and sea level variations is that long time series of both variables rarely exist. Wave statistics are also highly location-dependent, thus requiring wave buoy measurements and/or high-resolution wave modelling. As an initial approximation of the joint effect, the variables may be treated as independent random variables, to achieve the probability distribution of their sum. We present results of a case study based on three probability distributions: 1) wave run-up constructed from individual wave buoy measurements, 2) short-term sea level variability based on tide gauge data, and 3) mean sea level projections based on up-to-date regional scenarios. The wave measurements were conducted during 2012-2014 on the coast of city of Helsinki located in the Gulf of Finland in the Baltic Sea. The short-term sea level distribution contains the last 30 years (1986-2015) of hourly data from Helsinki tide gauge, and the mean sea level projections are scenarios adjusted for the Gulf of Finland. Additionally, we present a sensitivity test based on six different theoretical wave height distributions representing different wave behaviour in relation to sea level variations. As these wave distributions are merged with one common sea level distribution, we can study how the different shapes of the wave height distribution affect the distribution of the sum, and which one of the components is dominating under different wave conditions. As an outcome of the method, we obtain a probability distribution of the maximum elevation of the continuous water mass, which enables a flexible tool for evaluating different risk levels in the current and future climate.

Ice2sea - the future glacial contribution to sea-level rise

NASA Astrophysics Data System (ADS)

Vaughan, D. G.; Ice2sea Consortium

2009-04-01

The melting of continental ice (glaciers, ice caps and ice sheets) is a substantial source of current sea-level rise, and one that is accelerating more rapidly than was predicted even a few years ago. Indeed, the most recent report from Intergovernmental Panel on Climate Change highlighted that the uncertainty in projections of future sea-level rise is dominated by uncertainty concerning continental ice, and that understanding of the key processes that will lead to loss of continental ice must be improved before reliable projections of sea-level rise can be produced. Such projections are urgently required for effective sea-defence management and coastal adaptation planning. Ice2sea is a consortium of European institutes and international partners seeking European funding to support an integrated scientific programme to improve understanding concerning the future glacial contribution to sea-level rise. This includes improving understanding of the processes that control, past, current and future sea-level rise, and generation of improved estimates of the contribution of glacial components to sea-level rise over the next 200 years. The programme will include targeted studies of key processes in mountain glacier systems and ice caps (e.g. Svalbard), and in ice sheets in both polar regions (Greenland and Antarctica) to improve understanding of how these systems will respond to future climate change. It will include fieldwork and remote sensing studies, and develop a suite of new, cross-validated glacier and ice-sheet model. Ice2sea will deliver these results in forms accessible to scientists, policy-makers and the general public, which will include clear presentations of the sources of uncertainty. Our aim is both, to provide improved projections of the glacial contribution to sea-level rise, and to leave a legacy of improved tools and techniques that will form the basis of ongoing refinements in sea-level projection. Ice2sea will provide exciting opportunities for many early-career glaciologists and ice-modellers in a variety of host institutes.

Revisiting global mean sea level budget closure : Preliminary results from an integrative study within ESA's Climate Change Initiative -Sea level Budget Closure-Climate Change Initiative

NASA Astrophysics Data System (ADS)

Palanisamy, H.; Cazenave, A. A.

2017-12-01

The global mean sea level budget is revisited over two time periods: the entire altimetry era, 1993-2015 and the Argo/GRACE era, 2003-2015 using the version '0' of sea level components estimated by the SLBC-CCI teams. The SLBC-CCI is an European Space Agency's project on sea level budget closure using CCI products. Over the entire altimetry era, the sea level budget was performed as the sum of steric and mass components that include contributions from total land water storage, glaciers, ice sheets (Greenland and Antarctica) and total water vapor content. Over the Argo/GRACE era, it was performed as the sum of steric and GRACE based ocean mass. Preliminary budget analysis performed over the altimetry era (1993-2015) results in a trend value of 2.83 mm/yr. On comparison with the observed altimetry-based global mean sea level trend over the same period (3.03 ± 0.5 mm/yr), we obtain a residual of 0.2 mm/yr. In spite of a residual of 0.2 mm/yr, the sea level budget result obtained over the altimetry era is very promising as this has been performed using the version '0' of the sea level components. Furthermore, uncertainties are not yet included in this study as uncertainty estimation for each sea level component is currently underway. Over the Argo/GRACE era (2003-2015), the trend estimated from the sum of steric and GRACE ocean mass amounts to 2.63 mm/yr while that observed by satellite altimetry is 3.37 mm/yr, thereby leaving a residual of 0.7 mm/yr. Here an ensemble GRACE ocean mass data (mean of various available GRACE ocean mass data) was used for the estimation. Using individual GRACE data results in a residual range of 0.5 mm/yr -1.1 mm/yr. Investigations are under way to determine the cause of the vast difference between the observed sea level and the sea level obtained from steric and GRACE ocean mass. One main suspect is the impact of GRACE data gaps on sea level budget analysis due to lack of GRACE data over several months since 2011. The current action plan of the project is to work on an accurate closure of the sea level budget using both the above performed methodologies. We also intend to provide a standardized uncertainty estimation and to correctly identify the causes leading to sea level budget non-closure if that is the case.

Bald eagles and sea otters in the Aleutian Archipelago: indirect effects of trophic cascades.

USGS Publications Warehouse

Anthony, R.G.; Estes, J.A.; Ricca, M.A.; Miles, A.K.; Forsman, E.D.

2008-01-01

Because sea otters (Enhydra lutris) exert a wide array of direct and indirect effects on coastal marine ecosystems throughout their geographic range, we investigated the potential influence of sea otters on the ecology of Bald Eagles (Haliaeetus leucocephalus) in the Aleutian Islands, Alaska, USA. We studied the diets, productivity, and density of breeding Bald Eagles on four islands during 1993–1994 and 2000–2002, when sea otters were abundant and scarce, respectively. Bald Eagles depend on nearshore marine communities for most of their prey in this ecosystem, so we predicted that the recent decline in otter populations would have an indirect negative effect on diets and demography of Bald Eagles. Contrary to our predictions, we found no effects on density of breeding pairs on four islands from 1993–1994 to 2000–2002. In contrast, diets and diet diversity of Bald Eagles changed considerably between the two time periods, likely reflecting a change in prey availability resulting from the increase and subsequent decline in sea otter populations. The frequency of sea otter pups, rock greenling (Hexagammus lagocephalus), and smooth lumpsuckers (Aptocyclus ventricosus) in the eagle's diet declined with corresponding increases in Rock Ptarmigan (Lagopus mutus), Glaucous-winged Gulls (Larus glaucescens), Atka mackerel (Pleurogrammus monopterygius), and various species of seabirds during the period of the recent otter population decline. Breeding success and productivity of Bald Eagles also increased during this time period, which may be due to the higher nutritional quality of avian prey consumed in later years. Our results provide further evidence of the wide-ranging indirect effects of sea otter predation on nearshore marine communities and another apex predator, the Bald Eagle. Although the indirect effects of sea otters are widely known, this example is unique because the food-web pathway transcended five species and several trophic levels in linking one apex predator to another.

A joint analysis of sea-level and meteorological data over the past 19th and 20th century on the Charente-Maritime French Atlantic coast

NASA Astrophysics Data System (ADS)

Gouriou, Thomas; Wöppelmann, Guy

2010-05-01

A systematic survey of the historical French archives was initiated in 2004 to search for ancient sea level observations. Long term sea-level records are invaluable to study trends in sea level components in the context of climate change due to global warming. A large amount of records have been discovered, notably on the Charente-Maritime French Atlantic coast: fort Enet (1859-1873) and fort Boyard (1873-1909), a few kilometres apart. These two historical data sets include meteorological observations in addition to the sea-level heights: sea-level pressure, air temperature, wind direction and speed, and sometimes daily indications on the local climatic conditions. Sea-level heights were measured with a "Chazallon" type of float tide gauge and whereas the sea-level pressures were measured with a "Fortin" mercury barometer. The historical data sets are now in computer-accessible form. They were manually checked for consistency, and compared to nearby data sets (e.g. Brest, Hadley centre Sea Level Pressure data set HadSLP2). We will present the data sets, the composite time series that were built for the period 1859-1909, and the joint sea level and meteorological data analysis which proved worthwhile. The pressure data were indeed of particular interest (7 observations per day, from 6.00am to 9.00pm between 1859 and 1909). First, examining the inverse barometer (IB) effect was demonstrated to be a good means to check the sea-level data sets (Woodworth 2006). If the data sets were of poor quality, then the sea-level height and air pressure monthly mean time series would show low or no correlation. Conversely, if both data sets were of good quality, there would be a high negative correlation between the local sea-level heights and sea-level pressure changes. Second, a linear regression between the two parameters (sea level and atmospheric pressure) would be giving a regression coefficient of approximately -1 cm/mbar under static assumption. Any departure from this relationship is indicative of wind-driven dynamical processes. As will be shown, the Charente-Maritime French Atlantic coast is a particular environment subject to westward winds with a complex coastline and bathymetry (islands, shallow waters). Last but not least, our data archeology exercise will provide additional evidence to the intriguing relation that was first noted by Miller and Douglas (2007) between sea level on the eastern boundary of the North Atlantic and the strength of the gyre-scale circulation, as represented by air pressure in the centre of the gyre, on multi-decadal and century-timescales.

Global mean temperature indicators linked to warming levels avoiding climate risks

NASA Astrophysics Data System (ADS)

Pfleiderer, Peter; Schleussner, Carl-Friedrich; Mengel, Matthias; Rogelj, Joeri

2018-06-01

International climate policy uses global mean temperature rise limits as proxies for societally acceptable levels of climate change. These limits are informed by risk assessments which draw upon projections of climate impacts under various levels of warming. Here we illustrate that indicators used to define limits of warming and those used to track the evolution of the Earth System under climate change are not directly comparable. Depending on the methodological approach, differences can be time-variant and up to 0.2 °C for a warming of 1.5 °C above pre-industrial levels. This might lead to carbon budget overestimates of about 10 years of continued year-2015 emissions, and about a 10% increase in estimated 2100 sea-level rise. Awareness of this definitional mismatch is needed for a more effective communication between scientists and decision makers, as well as between the impact and physical climate science communities.

Sea level rise and variability around Peninsular Malaysia

NASA Astrophysics Data System (ADS)

Tkalich, Pavel; Luu, Quang-Hung; Tay, Tze-Wei

2014-05-01

Peninsular Malaysia is bounded from the west by Malacca Strait and the Andaman Sea, both connected to the Indian Ocean, and from the east by South China Sea being largest marginal sea in the Pacific Basin. As a result, sea level along Peninsular Malaysia coast is assumed to be governed by various regional phenomena associated with the adjacent parts of the Indian and Pacific Oceans. At annual scale, sea level anomalies (SLAs) are generated by the Asian monsoon; interannual sea level variability is determined by the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD); whilst long term sea level trend is coordinated by the global climate change. To quantify the relative impacts of these multi-scale phenomena on sea level trend and variability surrounding the Peninsular Malaysia, long-term tide gauge record and satellite altimetry are used. During 1984-2011, relative sea level rise (SLR) rates in waters of Malacca Strait and eastern Peninsular Malaysia are found to be 2.4 ± 0.8 mm/yr and 2.7 ± 0.6 mm/yr, respectively. Discounting for their vertical land movements (0.8 ± 2.6 mm/yr and 0.9 ± 2.2 mm/yr, respectively), their pure SLR rates are 1.6 ± 3.4 mm/yr and 1.8 ± 2.8 mm/yr, respectively, which are lower than the global tendency. At interannual scale, ENSO affects sea level over the Malaysian east coast in the range of ± 5 cm with very high correlation coefficient. Meanwhile, IOD modulates sea level anomalies in the Malacca Strait in the range of ± 2 cm with high correlation coefficient. Interannual regional sea level drops are associated with El Niño events and positive phases of the IOD index; while the rises are correlated with La Niña episodes and the negative periods of the IOD index. Seasonally, SLAs are mainly monsoon-driven, in the order of 10-25 cm. Geographically, sea level responds differently to the monsoon: two cycles per year are observed in the Malacca Strait, presumably due to South Asian - Indian Monsoon; while single annual cycle is noted in the remaining region, mostly due to East Asian - Western Pacific Monsoon. These results imply that a narrow topographic constriction off Singapore may separate different modes of annual and interannual sea level variability along coastline of Peninsular Malaysia.

Regional Sea Level Changes Projected by the NASA/GISS Atmosphere-Ocean Model

NASA Technical Reports Server (NTRS)

Russell, Gary L.; Gornitz, Vivien; Miller, James R.

1999-01-01

Sea level has been rising for the past century, and inhabitants of the Earth's coastal regions will want to understand and predict future sea level changes. In this study we present results from new simulations of the Goddard Institute for Space Studies (GISS) global atmosphere-ocean model from 1950 to 2099. Model results are compared with observed sea level changes during the past 40 years at 17 coastal stations around the world. Using observed levels of greenhouse gases between 1950 and 1990 and a compounded 0.5% annual increase in Co2 after 1990, model projections show that global sea level measured from 1950 will rise by 61 mm in the year 2000, by 212 mm in 2050, and by 408 mm in 2089. By 2089, two thirds of the global sea level rise will be due to thermal expansion and one third will be due to ocean mass changes. The spatial distribution of sea level rise is different than that projected by rigid lid ocean models.

Late Holocene SST and primary productivity variations in the northeastern Arabian Sea as a recorder for winter monsoon variability

NASA Astrophysics Data System (ADS)

Böll, Anna; Gaye, Birgit; Lückge, Andreas

2014-05-01

Variability in the oceanic environment of the Arabian Sea region is strongly influenced by the seasonal monsoon cycle of alternating wind directions. Strong south-westerly winds during the summer monsoon induce upwelling of nutrient rich waters along the coast off Somalia, Oman and southwest India, which result in high rates of primary production. In the northeastern Arabian Sea off Pakistan on the other hand, primary production and sea surface temperatures are linked to northeast monsoonal winds that cool the sea surface and drive convective mixing and high surface ocean productivity during the winter season. In this study, we analyzed alkenone-derived sea surface temperature (SST) variations and proxies of primary productivity (organic carbon and δ15N) in a well-laminated sediment core from the Pakistan continental margin to establish the first high-resolution record of winter monsoon variability for the late Holocene. Over the last 2400 years reconstructed SST in the northeastern Arabian Sea decreased whereas productivity increased, imaging a long-term trend of northeast monsoon strengthening in response to insolation-induced southward migration of the Intertropical Convergence Zone. The comparison of our winter monsoon record with records of summer monsoon intensity suggests that summer and winter monsoon strength was essentially anti-correlated over the late Holocene throughout the Asian monsoon system. In addition, SST variations recorded off Pakistan match very well with Northern Hemisphere temperature records supporting the growing body of evidence that Asian climate is linked to Northern Hemisphere climate change. It reveals a consistent pattern of increased summer monsoon activity in the northeastern Arabian Sea during northern hemispheric warm periods (Medieval Warm Period, Roman Warm Period) and strengthened winter monsoon activity during hemispheric colder periods (Little Ice Age).

Caribbean coral growth influenced by anthropogenic aerosol emissions

NASA Astrophysics Data System (ADS)

Kwiatkowski, Lester; Cox, Peter M.; Economou, Theo; Halloran, Paul R.; Mumby, Peter J.; Booth, Ben B. B.; Carilli, Jessica; Guzman, Hector M.

2013-05-01

Coral growth rates are highly dependent on environmental variables such as sea surface temperature and solar irradiance. Multi-decadal variability in coral growth rates has been documented throughout the Caribbean over the past 150-200 years, and linked to variations in Atlantic sea surface temperatures. Multi-decadal variability in sea surface temperatures in the North Atlantic, in turn, has been linked to volcanic and anthropogenic aerosol forcing. Here, we examine the drivers of changes in coral growth rates in the western Caribbean between 1880 and 2000, using previously published coral growth chronologies from two sites in the region, and a numerical model. Changes in coral growth rates over this period coincided with variations in sea surface temperature and incoming short-wave radiation. Our model simulations show that variations in the concentration of anthropogenic aerosols caused variations in sea surface temperature and incoming radiation in the second half of the twentieth century. Before this, variations in volcanic aerosols may have played a more important role. With the exception of extreme mass bleaching events, we suggest that neither climate change from greenhouse-gas emissions nor ocean acidification is necessarily the driver of multi-decadal variations in growth rates at some Caribbean locations. Rather, the cause may be regional climate change due to volcanic and anthropogenic aerosol emissions.

Parasites of the deep-sea fish Mora moro (Risso, 1810) from the NW Mediterranean Sea and relationship with fish diet and enzymatic biomarkers

NASA Astrophysics Data System (ADS)

Dallarés, Sara; Constenla, María; Padrós, Francesc; Cartes, Joan E.; Solé, Montse; Carrassón, Maite

2014-10-01

Specimens of Mora moro were collected in two seasons and three localities of the Balearic Sea (NW Mediterranean Sea) and parasitological, dietary (to prey-species level), enzymatic and histological data were obtained, alongside with environmental information (T, S, O2). The relationships among fish parasite load, condition indices, diet, enzymatic activity of muscular acetylcholinesterase (AChE) and lactate dehydrogenase (LDH), intensity of splenic melano-macrophage centres (MMC) and hepatic granulomas were tested. M. moro showed a rich and abundant parasite fauna, and was a new host record for 17 out of the 18 different endoparasite taxa found. Significant differences were detected among locality-season groups, in turn related to different environmental variables, for Anisakidae gen. sp., Anisakis Type II and Tetraphyllidea fam. gen. sp.; thus, they are proposed as potentially useful as biological tags for geographical discrimination of M. moro in the NW Mediterranean Sea. Detailed relationships were found between parasite taxa and prey ingested (e.g. Anisakidae gen. sp. related with meso-bathypelagic crustaceans; Anisakis Type I with benthopelagic squids). Most parasites were linked to samples with highest levels of near-bottom O2, which is consistent with direct relationships found between near-bottom O2 and zooplankton biomass in the Balearic Basin. Total parasite abundance and the abundance of Tetraphyllidea fam. gen. sp. showed a significant relationship with the activity of AChE and the abundance of Anisakis Type II with LDH. AChE was associated with hepatosomatic index (HSI) and condition factor (K); LDH with gonadosomatic index (GSI), K and fish total length (TL). LDH activity showed differences among sampling groups. Splenic MMC and hepatic granulomas were not associated with fish parasite load. A positive relationship was found between MMC area and fish TL and LDH activity.

Isotopic signatures, foraging habitats and trophic relationships between fish and seasnakes on the coral reefs of New Caledonia

NASA Astrophysics Data System (ADS)

Brischoux, F.; Bonnet, X.; Cherel, Y.; Shine, R.

2011-03-01

A predator's species, sex and body size can influence the types of prey that it consumes, but why? Do such dietary divergences result from differences in foraging habitats, or reflect differential ability to locate, capture or ingest different types of prey? That question is difficult to answer if foraging occurs in places that preclude direct observation. In New Caledonia, amphibious sea kraits ( Laticauda laticaudata and L. saintgironsi) mostly eat eels—but the species consumed differ between snake species and vary with snake body size and sex. Because the snakes capture eels within crevices on the sea floor, it is not possible to observe snake foraging on any quantitative basis. We used stable isotopes to investigate habitat-divergence and ontogenetic shifts in feeding habits of sympatric species of sea kraits. Similarities in δ15 N (~10.5‰) values suggest that the two snake species occupy similar trophic levels in the coral-reef foodweb. However, δ13C values differed among the eight eel species consumed by snakes, as well as between the two snake species, and were linked to habitat types. Specifically, δ13C differed between soft- vs. hard-substrate eel species, and consistently differed between the soft-bottom forager L. laticaudata (~ -14.7‰) and the hard-bottom forager L. saintgironsi (~ -12.5‰). Differences in isotopic signatures within and between the two sea krait species and their prey were consistent with the hypothesis of habitat-based dietary divergence. Isotopic composition varied with body size within each of the snake species and varied with body size within some eel species, reflecting ontogenetic shifts in feeding habits of both the sea kraits and their prey. Our results support the findings of previous studies based on snake stomach contents, indicating that further studies could usefully expand these isotopic analyses to a broader range of trophic levels, fish species and spatial scales.

Cyclone trends constrain monsoon variability during Late Oligocene sea level highstands (Kachchh Basin, NW India)

NASA Astrophysics Data System (ADS)

Reuter, M.; Piller, W. E.; Harzhauser, M.; Kroh, A.

2013-01-01

Important concerns about the consequences of climate change for India are the potential impact on tropical cyclones and the monsoon. Herein we present a sequence of fossil shell beds from the shallow-marine Maniyara Fort Formation (Kachcch Basin) as an indicator of tropical cyclone activity along the NW Indian coast during the Late Oligocene warming period (~27-24 Ma). Direct proxies providing information about the atmospheric circulation dynamics over the Indian subcontinent at this time are important since it corresponds to a major climate reorganization in Asia that ends up with the establishment of the modern Asian monsoon system in the Early Miocene. The vast shell concentrations comprise a mixture of parautochthonous and allochthonous assemblages indicating storm-generated sediment transport from deep to shallow water during third-order sea level highstands. Three distinct skeletal assemblages were distinguished each recording a relative storm wave base depth. (1) A shallow storm wave base is shown by nearshore mollusks, corals and Clypeaster echinoids; (2) an intermediate storm wave base depth is indicated by lepidocyclind foraminifers, Eupatagus echinoids and corallinaceans; and (3) a deep storm wave base is represented by an Amussiopecten-Schizaster echinoid assemblage. Vertical changes in these skeletal associations give evidence of gradually increasing tropical cyclone intensity in line with third-order sea level rise. The intensity of cyclones over the Arabian Sea is primarily linked to the strength of the Indian monsoon. Therefore and since the topographic boundary conditions for the Indian monsoon already existed in the Late Oligocene, the longer-term cyclone trends were interpreted to reflect monsoon variability during the initiation of the Asian monsoon system. Our results imply an active monsoon over the Eastern Tethys at ~26 Ma followed by a period of monsoon weakening during the peak of the Late Oligocene global warming (~24 Ma).

Eustatic sea level fluctuations induced by polar wander

NASA Technical Reports Server (NTRS)

Sabadini, Roberto; Doglioni, Carlo; Yuen, David A.

1990-01-01

It is shown here that polar wander of a viscoelastic, stratified earth can induce global sea level fluctuations comparable to the short-term component in eustatic sea-level curves. The sign of these fluctuations, which are very sensitive to the rheological stratification, depends on the geographical location of the observation point; rises and falls in sea level can thus be coeval in different parts of the world. This finding is a distinct contrast to the main assumption underlying the reconstruction of eustatic curves, namely that global sea-level events produce the same depositional sequence everywhere. It is proposed that polar wander should be added to the list of geophysical mechanisms that can control the third-order cycles in sea level.

Holocene environmental change along the southern Cape coast of South Africa - Insights from the Eilandvlei sediment record spanning the last 8.9 kyr

NASA Astrophysics Data System (ADS)

Wündsch, Michael; Haberzettl, Torsten; Cawthra, Hayley C.; Kirsten, Kelly L.; Quick, Lynne J.; Zabel, Matthias; Frenzel, Peter; Hahn, Annette; Baade, Jussi; Daut, Gerhard; Kasper, Thomas; Meadows, Michael E.; Mäusbacher, Roland

2018-04-01

This study investigates Holocene sediments from Eilandvlei, a coastal lake located within the Wilderness embayment at the southern Cape coast of South Africa. The evolution of the present estuarine/coastal lake system is reconstructed based on seismic data as well as a multi-proxy approach on a 30.5 m sediment core spanning the last 8.9 kyr. Geochemical (Ca, TOC/S, Br/TOC) and micropalaeontological data (diatoms, foraminifera) reflect changes in the degree of marine influence at the core site. The embayment likely developed via distinct phases of connectivity to the Indian Ocean caused by sea level changes and dune progradation. Marine conditions prevailed at the core site from 8900 to 4700 cal BP. The rapid sea level rise during the early Holocene caused the inundation of a palaeovalley that most likely had formed at lower sea levels during the Pleistocene. Towards the mid-Holocene the sea level exceeded its present height around 7500 cal BP creating a marine embayment. At 4700 cal BP, the embayment became distinctly more disconnected from the ocean turning into a lagoon system that persisted until 1200 cal BP. Subsequently, the marine influence further decreased and the present estuarine/coastal lake system was established. Grain size and geochemical data (Fe, Si/Al, chemical index of alteration (CIA)) further reflect changes in the deposition of terrigenous sediments at the core site. While the sedimentation of fine-grained (<16 μm), iron-rich and highly weathered material is linked to periods of increased river discharge and rainfall, high amounts of deposited quartz (31-250 μm, high Si/Al) point to relatively dry and/or windy conditions during which increased aeolian transport of dune sands occurred. The proxies indicate reduced river discharge and hence possibly drier climatic conditions than today from 8900 to 7900 cal BP and 6400 to 3000 cal BP. In contrast, the periods between 7900-6400 cal BP and 3000 cal BP-present were likely characterized by high river discharge and thus, generally more rainfall. The reconstructed palaeoclimatic variations are discussed within the context of e.g., shifts in the position of the Antarctic sea ice extent and the mid-latitude westerly wind belt as well as changes in the El Niño-Southern Oscillation (ENSO).

Roles of Sea Level and Climate Change in the Development of Holocene Deltaic Sequences in the Yellow Sea

NASA Astrophysics Data System (ADS)

Liu, J.; Milliman, J. D.

2002-12-01

Both post-glacial sea-level and climatic changes are preserved in the the shallow, low gradient, sediment-dominated Yellow Sea. As a result of rapid flooding during melt-water pulse (MWP) 1A, 14.3-14.1 ka BP, sea level reached the southern edge of the North Yellow Sea (NYS), and after MWP-1B (11.6-11.4 ka BP) sea level entered the Bohai Sea. The first major Yellow River-derived deltaic deposit formed in the NYS during decelerated transgression following MWP-1B and increased river discharge in response to re-intensification of the summer monsoon about 11 ka cal BP. A second subaqueous delta formed in the South Yellow Sea about 9-7 ka BP during decelerated transgression after MWP-1C flooding and in response to the southern shift of the Yellow River mouth. The modern subaqueous and subaerial deltas in the west Bahai Gulf and (to a lesser extent) along the Jiangus coast have formed during the modern sea-level highstand. These changing Holocene patterns are most clearly illustrated by a short film clip.

SeaDataNet : Pan-European infrastructure for marine and ocean data management - Project objectives, structure and components

NASA Astrophysics Data System (ADS)

Maudire, G.; Maillard, C.; Fichaut, M.; Manzella, G.; Schaap, D. M. A.

2009-04-01

SeaDataNet : Pan-European infrastructure for marine and ocean data management Project objectives, structure and components G. Maudire (1), C. Maillard (1), G. Manzella (2), M. Fichaut (1), D.M.A. Schaap (3), E. Iona (4) and the SeaDataNet consortium. (1) IFREMER, Brest, France (Gilbert.Maudire@ifremer.fr), (2) ENEA, La Spezia, Italy, (3) Mariene Informatie Service 'MARIS', Voorburg, The Netherlands, (4) Hellenic Centre for Marine Research-HCMR, Anavyssos, Greece. Since a large part of the earth population lives near the oceans or carries on activities directly or indirectly linked to the seas (fishery and aquaculture, exploitation of sea bottom resources, international shipping, tourism), knowledge of oceans is of primary importance for security and economy. However, observation and monitoring of the oceans remains difficult and expensive even if real improvements have been achieved using research vessels and submersibles, satellites and automatic observatories like buoys, floats and seafloor observatories transmitting directly to the shore using global transmission systems. More than 600 governmental or private organizations are active in observation of seas bordering Europe, but European oceanographic data are fragmented, not always validated and not always easily accessible. That highlights the need of international collaboration to tend toward a comprehensive view of ocean mechanisms, resources and changes. SeaDataNet is an Integrated research Infrastructure Initiative (I3) in European Union Framework Program 6 (2006 - 2011) to provide the data management system adapted both to the fragmented observation systems and to the users need for an integrated access to data, meta-data, products and services. Its major objectives are to: - encourage long-term archiving at national level to secure ocean data taking into account that all the observations made in the variable oceanic environment can never be remade if they are lost; - promote best practices for data management, taking benefits of the development of international initiatives and standards on data quality insurance, data descriptions (metadata and common vocabulary) and interoperability. Software tools are developed or adapted accordingly to support these practices and the adoption of standards; - establish online services to facilitate data discovery, data requests, data visualisation and data download for the users; - process data sets of reference like ocean climatologies at a regional basin scale to provide comprehensive data sets Sustainability of the provided services is researched by a balance between the activities mostly undertaken at National level by the National Oceanographic data centres or some thematic data centres and the effort done at the Pan-European level by the project. The SeaDataNet consortium brings now together a unique group of 49 partners from major oceanographic institutes of 35 countries. Taking in account that valuable work on ocean data management must be done at basin level, most of countries bordering Black Sea, Mediterranean Sea, North-East Atlantic, North Sea, Baltic Sea and Artic Sea are part of the project. Capacity building of consortium members is necessary to meet project objectives and a comprehensive training program is conducted both for data management and for IT technologies which are necessary to establish such a distributed system: databases management, XML language, web portal and services, GIS technologies. SeaDataNet Partners: IFREMER (France), MARIS (Netherlands), HCMR/HNODC (Greece), ULg (Belgium), OGS (Italy),NERC/BODC (UK), BSH/DOD (Germany), SMHI (Sweden), IEO (Spain), RIHMI/WDC (Russia), IOC (International), ENEA (Italy), INGV (Italy), METU (Turkey), CLS (France), AWI (Germany), IMR (Norway), NERI (Denmark), ICES (International), EC-DG JRC (International), MI (Ireland), IHPT (Portugal), RIKZ (Netherlands), RBINS/MUMM (Belgium), VLIZ (Belgium), MRI (Iceland), FIMR (Finland ), IMGW (Poland), MSI (Estonia), IAE/UL (Latvia), CMR (Lithuania), SIO/RAS (Russia), MHI/DMIST (Ukraine), IO/BAS (Bulgaria), NIMRD (Romania), TSU (Georgia), INRH (Morocco), IOF (Croatia), PUT (Albania), NIB (Slovenia), UoM (Malta), OC/UCY (Cyprus), IOLR (Israel), NCSR/NCMS (Lebanon), CNR-ISAC (Italy), ISMAL (Algeria), INSTM (Tunisia)

Sea level and shoreline reconstructions for the Red Sea: isostatic and tectonic considerations and implications for hominin migration out of Africa

NASA Astrophysics Data System (ADS)

Lambeck, Kurt; Purcell, Anthony; Flemming, Nicholas. C.; Vita-Finzi, Claudio; Alsharekh, Abdullah M.; Bailey, Geoffrey N.

2011-12-01

The history of sea level within the Red Sea basin impinges on several areas of research. For archaeology and prehistory, past sea levels of the southern sector define possible pathways of human dispersal out of Africa. For tectonics, the interglacial sea levels provide estimates of rates for vertical tectonics. For global sea level studies, the Red Sea sediments contain a significant record of changing water chemistry with implications on the mass exchange between oceans and ice sheets during glacial cycles. And, because of its geometry and location, the Red Sea provides a test laboratory for models of glacio-hydro-isostasy. The Red Sea margins contain incomplete records of sea level for the Late Holocene, for the Last Glacial Maximum, for the Last Interglacial and for earlier interglacials. These are usually interpreted in terms of tectonics and ocean volume changes but it is shown here that the glacio-hydro-isostatic process is an additional important component with characteristic spatial variability. Through an iterative analysis of the Holocene and interglacial evidence a separation of the tectonic, isostatic and eustatic contributions is possible and we present a predictive model for palaeo-shorelines and water depths for a time interval encompassing the period proposed for migrations of modern humans out of Africa. Principal conclusions include the following. (i) Late Holocene sea level signals evolve along the length of the Red Sea, with characteristic mid-Holocene highstands not developing in the central part. (ii) Last Interglacial sea level signals are also location dependent and, in the absence of tectonics, are not predicted to occur more than 1-2 m above present sea level. (iii) For both periods, Red Sea levels at 'expected far-field' elevations are not necessarily indicative of tectonic stability and the evidence points to a long-wavelength tectonic uplift component along both the African and Arabian northern and central sides of the Red Sea. (iv) The observational evidence is consistent with tectonic and isostatic processes both operating over the past 300,000 years without requiring changes in the time averaged (over a few thousand years) tectonic rates. (v) Recent bathymetric data for the Bab al Mandab region have been compiled to confirm the location and depth of the sill controlling flow in and out of the Red Sea. Throughout the last 400,000 years the Red Sea has remained open to the Gulf of Aden with cross sectional areas at times of glacial maxima about 2% of that today. (vi) The minimum channel widths connecting the Red Sea to the Gulf of Aden at times of lowstand occur south of the Hanish Sill. The channels are less than 4 km wide and remain narrow for as long as local sea levels are below -50 m. This occurs for a number of sustained periods during the last two glacial cycles and earlier. (vii) Periods suitable for crossing between Africa and Arabia without requiring seaworthy boats or seafaring skills occurred periodically throughout the Pleistocene, particularly at times of favourable environmental climatic conditions that occurred during times of sea level lowstand.

The Caribbean conundrum of Holocene sea level.

NASA Astrophysics Data System (ADS)

Jackson, Luke; Mound, Jon

2014-05-01

In the tropics, pre-historic sea-level curve reconstruction is often problematic because it relies upon sea-level indicators whose vertical relationship to the sea surface is poorly constrained. In the Caribbean, fossil corals, mangrove peats and shell material dominate the pre-historic indicator record. The common approach to reconstruction involves the use of modern analogues to these indicators to establish a fixed vertical habitable range. The aim of these reconstructions is to find spatial variability in the Holocene sea level in an area gradually subsiding (< 1.2 mm yr-1) due the water loading following the deglaciation of the Laurentide ice sheet. We construct two catalogues: one of published Holocene sea-level indicators and the other of published, modern growth rates, abundance and coverage of mangrove and coral species for different depths. We use the first catalogue to calibrate 14C ages to give a probabilistic age range for each indicator. We use the second catalogue to define a depth probability distribution function (pdf) for mangroves and each coral species. The Holocene indicators are grouped into 12 sub-regions around the Caribbean. For each sub-region we apply our sea-level reconstruction, which involves stepping a fixed-length time window through time and calculating the position (and rate) of sea-level (change) using a thousand realisations of the time/depth pdfs to define an envelope of probable solutions. We find that the sub-regional relative sea-level curves display spatio-temporal variability including a south-east to north-west 1500 year lag in the arrival of Holocene sea level to that of the present day. We demonstrate that these variations are primarily due to glacial-isostatic-adjustment induced sea-level change and that sub-regional variations (where sufficient data exists) are due to local uplift variability.

Sea level hazards: Altimetric monitoring of tsunamis and sea level rise

NASA Astrophysics Data System (ADS)

Hamlington, Benjamin Dillon

Whether on the short timescale of an impending tsunami or the much longer timescale of climate change-driven sea level rise, the threat stemming from rising and inundating ocean waters is a great concern to coastal populations. Timely and accurate observations of potentially dangerous changes in sea level are vital in determining the precautionary steps that need to be taken in order to protect coastal communities. While instruments from the past have provided in situ measurements of sea level at specific locations across the globe, satellites can be used to provide improved spatial and temporal sampling of the ocean in addition to producing more accurate measurements. Since 1993, satellite altimetry has provided accurate measurements of sea surface height (SSH) with near-global coverage. Not only have these measurements led to the first definitive estimates of global mean sea level rise, satellite altimetry observations have also been used to detect tsunami waves in the open ocean where wave amplitudes are relatively small, a vital step in providing early warning to those potentially affected by the impending tsunami. The use of satellite altimetry to monitor two specific sea level hazards is examined in this thesis. The first section will focus on the detection of tsunamis in the open ocean for the purpose of providing early warning to coastal inhabitants. The second section will focus on estimating secular trends using satellite altimetry data with the hope of improving our understanding of future sea level change. Results presented here will show the utility of satellite altimetry for sea level monitoring and will lay the foundation for further advancement in the detection of the two sea level hazards considered.

MIS 5e relative sea-level changes in the Mediterranean Sea: Contribution of isostatic disequilibrium

NASA Astrophysics Data System (ADS)

Stocchi, Paolo; Vacchi, Matteo; Lorscheid, Thomas; de Boer, Bas; Simms, Alexander R.; van de Wal, Roderik S. W.; Vermeersen, Bert L. A.; Pappalardo, Marta; Rovere, Alessio

2018-04-01

Sea-level indicators dated to the Last Interglacial, or Marine Isotope Stage (MIS) 5e, have a twofold value. First, they can be used to constrain the melting of Greenland and Antarctic Ice Sheets in response to global warming scenarios. Second, they can be used to calculate the vertical crustal rates at active margins. For both applications, the contribution of glacio- and hydro-isostatic adjustment (GIA) to vertical displacement of sea-level indicators must be calculated. In this paper, we re-assess MIS 5e sea-level indicators at 11 Mediterranean sites that have been generally considered tectonically stable or affected by mild tectonics. These are found within a range of elevations of 2-10 m above modern mean sea level. Four sites are characterized by two separate sea-level stands, which suggest a two-step sea-level highstand during MIS 5e. Comparing field data with numerical modeling we show that (i) GIA is an important contributor to the spatial and temporal variability of the sea-level highstand during MIS 5e, (ii) the isostatic imbalance from the melting of the MIS 6 ice sheet can produce a >2.0 m sea-level highstand, and (iii) a two-step melting phase for the Greenland and Antarctic Ice Sheets reduces the differences between observations and predictions. Our results show that assumptions of tectonic stability on the basis of the MIS 5e records carry intrinsically large uncertainties, stemming either from uncertainties in field data and GIA models. The latter are propagated to either Holocene or Pleistocene sea-level reconstructions if tectonic rates are considered linear through time.

The contribution to future flood risk in the Severn Estuary from extreme sea level rise due to ice sheet mass loss

NASA Astrophysics Data System (ADS)

Quinn, N.; Bates, P. D.; Siddall, M.

2013-12-01

The rate at which sea levels will rise in the coming century is of great interest to decision makers tasked with developing mitigation policies to cope with the risk of coastal inundation. Accurate estimates of future sea levels are vital in the provision of effective policy. Recent reports from UK Climate Impacts Programme (UKCIP) suggest that mean sea levels in the UK may rise by as much as 80 cm by 2100; however, a great deal of uncertainty surrounds model predictions, particularly the contribution from ice sheets responding to climatic warming. For this reason, the application of semi-empirical modelling approaches for sea level rise predictions has increased of late, the results from which suggest that the rate of sea level rise may be greater than previously thought, exceeding 1 m by 2100. Furthermore, studies in the Red Sea indicate that rapid sea level rise beyond 1m per century has occurred in the past. In light of such research, the latest UKCIP assessment has included a H++ scenario for sea level rise in the UK of up to 1.9 m which is defined as improbable but, crucially, physically plausible. The significance of such low-probability sea level rise scenarios upon the estimation of future flood risk is assessed using the Somerset levels (UK) as a case study. A simple asymmetric probability distribution is constructed to include sea level rise scenarios of up to 1.9 m by 2100 which are added to a current 1:200 year event water level to force a two-dimensional hydrodynamic model of coastal inundation. From the resulting ensemble predictions an estimation of risk by 2100 is established. The results indicate that although the likelihood of extreme sea level rise due to rapid ice sheet mass loss is low, the resulting hazard can be large, resulting in a significant (27%) increase to the projected annual risk. Furthermore, current defence construction guidelines for the coming century in the UK are expected to account for 95% of the sea level rise distribution presented in this research, while the larger, low probability scenarios beyond this level are estimated to contribute a residual annual risk of approximately £0.45 million. These findings clearly demonstrate that uncertainty in future sea level rise is a vital component of coastal flood risk, and therefore, needs to be accounted for by decision makers when considering mitigation policies related to coastal flooding.

Observed Arctic sea-ice loss directly follows anthropogenic CO2 emission.

PubMed

Notz, Dirk; Stroeve, Julienne

2016-11-11

Arctic sea ice is retreating rapidly, raising prospects of a future ice-free Arctic Ocean during summer. Because climate-model simulations of the sea-ice loss differ substantially, we used a robust linear relationship between monthly-mean September sea-ice area and cumulative carbon dioxide (CO 2 ) emissions to infer the future evolution of Arctic summer sea ice directly from the observational record. The observed linear relationship implies a sustained loss of 3 ± 0.3 square meters of September sea-ice area per metric ton of CO 2 emission. On the basis of this sensitivity, Arctic sea ice will be lost throughout September for an additional 1000 gigatons of CO 2 emissions. Most models show a lower sensitivity, which is possibly linked to an underestimation of the modeled increase in incoming longwave radiation and of the modeled transient climate response. Copyright © 2016, American Association for the Advancement of Science.

Growing the Anatolian plateau: Coupled tectonic deformation and lithospheric slab dynamics

NASA Astrophysics Data System (ADS)

Schildgen, T. F.; Cosentino, D.; Yildirim, C.; Echtler, H.; Strecker, M. R.

2011-12-01

The Anatolian plateau marks the western end of the high topography associated with collision of the African and Arabian plates with Eurasia. The Eastern and Central Anatolian plateaus have been considered separate entities, with crustal shortening in the east resulting in a 1.5- to 2.5-km high and more rugged plateau compared to the strike-slip bounded, 1- to 1.5-km high, relatively undeformed plateau in the west. Uplift mechanisms for the Eastern Anatolian plateau have been discussed for decades, and a mounting body of evidence supports an important role of both crustal shortening and lithospheric slab dynamics. In contrast, fewer studies have been focused on Central Anatolia. Our recent data constraining the timing, magnitude, pattern, and style of uplift in Central Anatolia helps not only to elucidate details of what may be an early stage in orogenic plateau development, but also highlights ways in which the two plateau realms may be closely linked. Approaches to determining paleoaltimetry in Central Anatolia differ from those in other major orogenic plateaus, as its modest elevations and low Neogene exhumation imply that stable isotope and thermochronological methods have limited applicability. Nonetheless, sedimentary basins within the plateau interior, preserved along the high-relief margins, and in basins flanking the plateau archive the deformation and uplift history, particularly where the uplifted strata include fossil-rich marine sediments. Combined with manifestations of river incision in response to surface uplift, these deposits offer one of the world's best-constrained records of long-term, km-scale surface uplift. However, assessing uplift along the plateau margins is complex, because the timing of the 1 to 1.5 km lowering of sea level in the Mediterranean and Black seas during the Messinian Salinity Crisis overlaps with the onset of regional surface uplift. Although a number of major questions remain concerning the relative timing of uplift of Eastern and Central Anatolia, how sea-level lowering and climate change affected records interpreted as an uplift signal, and to what extent upper mantle processes can be linked to surface uplift patterns, both the Central and Eastern Anatolia appear to have been impacted by lithospheric slab dynamics. Specifically, uplift of the southern margin of Central Anatolia starting between 7 and 5.45 Ma appears to postdate uplift of Eastern Anatolia, which may be explained by slab break-off and tearing that initiated in the east and subsequently propagated westward. In contrast to the processes forcing plateau uplift along the southern flank, we link growth of the northern margin of Central Anatolia to westward extrusion of the Anatolian microplate and the restraining bend in the North Anatolian Fault. These disparate underlying mechansims may be linked if the evolution of the subducting lithospheric slab helped to initiate westward extrusion of Central Anatolia.

Mortality sensitivity in life-stage simulation analysis: A case study of southern sea otters

USGS Publications Warehouse

Gerber, L.R.; Tinker, M.T.; Doak, D.F.; Estes, J.A.; Jessup, David A.

2004-01-01

Currently, there are no generally recognized approaches for linking detailed mortality and pathology data to population-level analyses of extinction risk. We used a combination of analytical and simulation-based analyses to examine 20 years of age- and sex-specific mortality data for southern sea otters (Enhydra lutris), and we applied results to project the efficacy of alternative conservation strategies. Population recovery of the southern sea otter has been slow (rate of population increase ?? = 1.05) compared to other recovering populations (?? = 1.17-1.20), and the population declined (?? = 0.975) between 1995 and 1999. Age-based Leslie matrices were developed to explore explanations for the slow recovery and recent decline in the southern sea other population. An elasticity analysis was performed to predict effects of proportional changes in stage-specific reproductive or survival rates on the rate of population increase. A life-stage simulation analysis (LSA) was developed to evaluate the impact of changing age- and cause-specific mortality rates on ??. The information used to develop these models was derived from death assemblage, pathology, and live population census data to examine the sensitivity of sea otter population growth to different sources of mortality (e.g., disease and starvation, direct human take [fisheries, gun shot, boat strike, oil pollution], mating trauma and intraspecific aggression, shark bites, and unknown). We used resampling simulations to generate random combinations of vital rates for a large number of matrix replicates and drew on these to estimate potential effects of mortality sources on population growth (??). Our analyses suggest management actions that are likely and unlikely to promote recovery of the southern sea otter and more broadly indicate a methodology to better utilize cause-of-death data in conservation decision-making.

Doubling of coastal flooding frequency within decades due to sea-level rise

USGS Publications Warehouse

Vitousek, Sean; Barnard, Patrick L.; Fletcher, Charles H.; Frazer, Neil; Erikson, Li; Storlazzi, Curt D.

2017-01-01

Global climate change drives sea-level rise, increasing the frequency of coastal flooding. In most coastal regions, the amount of sea-level rise occurring over years to decades is significantly smaller than normal ocean-level fluctuations caused by tides, waves, and storm surge. However, even gradual sea-level rise can rapidly increase the frequency and severity of coastal flooding. So far, global-scale estimates of increased coastal flooding due to sea-level rise have not considered elevated water levels due to waves, and thus underestimate the potential impact. Here we use extreme value theory to combine sea-level projections with wave, tide, and storm surge models to estimate increases in coastal flooding on a continuous global scale. We find that regions with limited water-level variability, i.e., short-tailed flood-level distributions, located mainly in the Tropics, will experience the largest increases in flooding frequency. The 10 to 20 cm of sea-level rise expected no later than 2050 will more than double the frequency of extreme water-level events in the Tropics, impairing the developing economies of equatorial coastal cities and the habitability of low-lying Pacific island nations.

Diet compositions and trophic guild structure of the eastern Chukchi Sea demersal fish community

NASA Astrophysics Data System (ADS)

Whitehouse, George A.; Buckley, Troy W.; Danielson, Seth L.

2017-01-01

Fishes are an important link in Arctic marine food webs, connecting production of lower trophic levels to apex predators. We analyzed 1773 stomach samples from 39 fish species collected during a bottom trawl survey of the eastern Chukchi Sea in the summer of 2012. We used hierarchical cluster analysis of diet dissimilarities on 21 of the most well sampled species to identify four distinct trophic guilds: gammarid amphipod consumers, benthic invertebrate generalists, fish and shrimp consumers, and zooplankton consumers. The trophic guilds reflect dominant prey types in predator diets. We used constrained analysis of principal coordinates (CAP) to determine if variation within the composite guild diets could be explained by a suite of non-diet variables. All CAP models explained a significant proportion of the variance in the diet matrices, ranging from 7% to 25% of the total variation. Explanatory variables tested included latitude, longitude, predator length, depth, and water mass. These results indicate a trophic guild structure is present amongst the demersal fish community during summer in the eastern Chukchi Sea. Regular monitoring of the food habits of the demersal fish community will be required to improve our understanding of the spatial, temporal, and interannual variation in diet composition, and to improve our ability to identify and predict the impacts of climate change and commercial development on the structure and functioning of the Chukchi Sea ecosystem.

Interannual sea level variability in the Pearl River Estuary and its response to El Niño-Southern Oscillation

NASA Astrophysics Data System (ADS)

Wang, Linlin; Li, Qiang; Mao, Xian-zhong; Bi, Hongsheng; Yin, Peng

2018-03-01

The South China coast, especially the Pearl River Estuary (PRE) region, is prosperous and densely populated, but vulnerable to sea level changes. Sea level anomalies (SLA) during 1954-2012 from tide gauge station data and regional SLAs during 1993-2012 from satellite altimetry are analyzed and compare to the El Niño-Southern Oscillation (ENSO). Results show that sea level declines during El Niño events and rises during La Niña. Sea level in the PRE responds to ENSO with 3-month lag. The ENSO can cause sea level in the PRE to fluctuate from -8.70 to 8.11 cm. Sea level cycles of 3 and 5 years are related to ENSO. The ENSO mechanism affecting sea level in the PRE was analyzed by identifying dominant regional and local forces. Weak/strong SLAs in most El Niño/La Niña events may be attributed to less/more seawater transport driven by anomalously weak/strong north winds and local anomalously high/low sea level pressure. Wind-driven coastal current is the predominant factor. It generated coastal seawater volume transport along a 160 km wide cross section to decrease by 21.07% in a typical El Niño period (January 2010) and increase by 44.03% in a typical La Niña period (January 2011) as compared to an ENSO neutral situation (January 2013). Results of sea level rise and its potential mechanism provide insight for disaster protection during extreme El Niño/La Niña events.

Global Sea Level Rise and its Impact Estimation Model by Beach Mechanics, GDP, and Shoreline Length using Big Data Approach.

NASA Astrophysics Data System (ADS)

Xu, A. A.

2016-12-01

Existing research has shown consistent increase in global sea levels due to warming of the climate; since 1870, average global sea level has risen by about 20 cm. There are processes that scientists and coastal engineers can follow to estimate the erosion and flooding risk impacts for specific locations based on historical data. However, there are no methods available to assess the risk impacts for locations where little research has been conducted. In this study, we introduce a prototype to better predict sea level change and land loss using big data technology. Our approach combines cluster analysis and artificial intelligence to classify and calculate impacts for locations worldwide. Data from 235 locations (89 countries) on sea level change was gathered from NOAA data investigations and other research organizations, including beach profile data, shoreline length data, and GDP data. The rate of sea level rise varies from -18 to 21 mm/yr. We divide the data into 4 groups (Group A: +0 to 9mm, Group B: +10 to +20mm, Group C: -0 to -9mm, and Group D:-10 to -20mm). Our research focuses on types A and B only since both reflect increase on sea level rise. We find the correlation between the sea level rise and factors such as the economic parameter (α), sea level rise height (h), beach breaker wave (Hb), gravitational constant (g), period of wave (T), foreshore slope (i), and sand sizes (D). We conclude the sea level rise impact ($ lost) can be more scientifically and precisely predicted using our model.

Sea-level variability over the Common Era

NASA Astrophysics Data System (ADS)

Kopp, Robert; Horton, Benjamin; Kemp, Andrew; Engelhart, Simon; Little, Chris

2017-04-01

The Common Era (CE) sea-level response to climate forcing, and its relationship to centennial-timescale climate variability such as the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA), is fragmentary relative to other proxy-derived climate records (e.g. atmospheric surface temperature). However, the Atlantic coast of North America provides a rich sedimentary record of CE relative sea level with sufficient spatial and temporal resolution to inform mechanisms underlying regional and global sea level variability and their relationship to other climate proxies. This coast has a small tidal range, improving the precision of sea-level reconstructions. Coastal subsidence (from glacial isostatic adjustment, GIA) creates accommodation space that is filled by salt-marsh peat and preserves accurate and precise sea-level indicators and abundant material for radiocarbon dating. In addition to longer term GIA induced land-level change from ongoing collapse of the Laurentide forebulge, these records are ideally situated to capture climate-driven sea level changes. The western North Atlantic Ocean sea level is sensitive to static equilibrium effects from melting of the Greenland Ice Sheet, as well as large-scale changes in ocean circulation and winds. Our reconstructions reveal two distinct patterns in sea-level during the CE along the United States Atlantic coast: (1) South of Cape Hatteras, North Carolina, to Florida sea-level rise is essentially flat, with the record dominated by long-term geological processes until the onset of historic rates of rise in the late 19th century; (2) North of Cape Hatteras to Connecticut, sea level rise to maximum around 1000CE, a sea-level minimum around 1500 CE, and a long-term sea-level rise through the second half of the second millennium. The northern-intensified sea-level fall beginning 1000 is coincident with shifts toward persistent positive NAO-like atmospheric states inferred from other proxy records and is consistent with climate model simulations forced with sustained NAO-like heat fluxes. Changes in the wind-driven ocean circulation may also contribute to alongshore sea level variability over the CE. To reveal global mean sea level variability, we combine the salt-marsh data from North American Atlantic coast with tide-gauge records and other high resolution proxies from the northern and southern hemispheres. All reconstructions are from coasts that are tectonically stable and are based on four types of proxy archives (archaeological indicators, coral microatolls, salt marsh sediments and vermetid [mollusk] bioconstructions) that are best capable of capturing submeter-scale RSL changes. The database consists of reconstructions from Australasia (n = 2), Europe (n=5), Greenland (n = 3), North America (n = 6), the northern Gulf of Mexico (n = 3), the Mediterranean (n = 1), South Africa (n = 2), South America (n =2) and the South Pacific (n =3). We apply a noisy-input Gaussian process spatio-temporal modeling framework, which identifies a long-term falling global mean sea-level, interrupted in the middle of the 19th century by an acceleration yielding a 20th century rate of rise extremely likely (probability P = 0:95) faster than any previous century in the CE.

Use of the quasi-geostrophic dynamical framework to reconstruct the 3-D ocean state in a high-resolution realistic simulation of North Atlantic.

NASA Astrophysics Data System (ADS)

Fresnay, Simon; Ponte, Aurélien

2017-04-01

The quasi-geostrophic (QG) framework has been, is and will be still for years to come a cornerstone method linking observations with estimates of the ocean circulation and state. We have used here the QG framework to reconstruct dynamical variables of the 3-D ocean in a state-of-the-art high-resolution (1/60 deg, 300 vertical levels) numerical simulation of the North Atlantic (NATL60). The work was carried out in 3 boxes of the simulation: Gulf Stream, Azores and Reykjaness Ridge. In a first part, general diagnostics describing the eddying dynamics have been performed and show that the QG scaling verifies in general, at depths distant from mixed layer and bathymetric gradients. Correlations with surface observables variables (e.g. temperature, sea level) were computed and estimates of quasi-geostrophic potential vorticity (QGPV) were reconstructed by the means of regression laws. It is shown that that reconstruction of QGPV exhibits valuable skill for a restricted scale range, mainly using sea level as the variable of regression. Additional discussion is given, based on the flow balanced with QGPV. This work is part of the DIMUP project, aiming to improve our ability to operationnaly estimate the ocean state.

Ecogeomorphology of Spartina patens-dominated tidal marshes: Soil organic matter accumulation, marsh elevation dynamics, and disturbance

USGS Publications Warehouse

Cahoon, D.R.; Ford, M.A.; Hensel, P.F.; Fagherazzi, Sergio; Marani, Marco; Blum, Linda K.

2004-01-01

Marsh soil development and vertical accretion in Spartina patens (Aiton) Muhl.-dominated tidal marshes is largely dependent on soil organic matter accumulation from root-rhizome production and litter deposition. Yet there are few quantitative data sets on belowground production and the relationship between soil organic matter accumulation and soil elevation dynamics for this marsh type. Spartina patens marshes are subject to numerous stressors, including sea-level rise, water level manipulations (i.e., flooding and draining) by impoundments, and prescribed burning. These stressors could influence long-term marsh sustainability by their effect on root production, soil organic matter accumulation, and soil elevation dynamics. In this review, we summarize current knowledge on the interactions among vegetative production, soil organic matter accumulation and marsh elevation dynamics, or the ecogeomorphology, of Spartina patens-dominated tidal marshes. Additional studies are needed of belowground production/decomposition and soil elevation change (measured simultaneously) to better understand the links among soil organic matter accumulation, soil elevation change, and disturbance in this marsh type. From a management perspective, we need to better understand the impacts of disturbance stressors, both lethal and sub-lethal, and the interactive effect of multiple stressors on soil elevation dynamics in order to develop better management practices to safeguard marsh sustainability as sea level rises.

Probabilistic Estimates of Global Mean Sea Level and its Underlying Processes

NASA Astrophysics Data System (ADS)

Hay, C.; Morrow, E.; Kopp, R. E.; Mitrovica, J. X.

2015-12-01

Local sea level can vary significantly from the global mean value due to a suite of processes that includes ongoing sea-level changes due to the last ice age, land water storage, ocean circulation changes, and non-uniform sea-level changes that arise when modern-day land ice rapidly melts. Understanding these sources of spatial and temporal variability is critical to estimating past and present sea-level change and projecting future sea-level rise. Using two probabilistic techniques, a multi-model Kalman smoother and Gaussian process regression, we have reanalyzed 20th century tide gauge observations to produce a new estimate of global mean sea level (GMSL). Our methods allow us to extract global information from the sparse tide gauge field by taking advantage of the physics-based and model-derived geometry of the contributing processes. Both methods provide constraints on the sea-level contribution of glacial isostatic adjustment (GIA). The Kalman smoother tests multiple discrete models of glacial isostatic adjustment (GIA), probabilistically computing the most likely GIA model given the observations, while the Gaussian process regression characterizes the prior covariance structure of a suite of GIA models and then uses this structure to estimate the posterior distribution of local rates of GIA-induced sea-level change. We present the two methodologies, the model-derived geometries of the underlying processes, and our new probabilistic estimates of GMSL and GIA.

On the regional characteristics of past and future sea-level change (Invited)

NASA Astrophysics Data System (ADS)

Timmermann, A.; McGregor, S.

2010-12-01

Global sea-level rise due to the thermal expansion of the warming oceans and freshwater input from melting glaciers and ice-sheets is threatening to inundate low-lying islands and coast-lines worldwide. At present global mean sea level rises at 3.1 ± 0.7 mm/yr with an accelerating tendency. However, the magnitude of recent decadal sea-level trends varies greatly spatially attaining values of up to 10 mm/yr in some areas of the western tropical Pacific. Identifying the causes of recent regional sea-level trends and understanding the patterns of future projected sea-level change is of crucial importance. Using a wind-forced simplified dynamical ocean model, we show that the regional features of recent decadal and multidecadal sea-level trends in the tropical Indo-Pacific can be attributed to changes in the prevailing wind-regimes. Furthermore it is demonstrated that within an ensemble of ten state-of-the art coupled general circulation models, forced by increasing atmospheric CO2 concentrations over the next century, wind-induced re-distributions of upper-ocean water play a key role in establishing the spatial characteristics of projected regional sea-level rise. Wind-related changes in near- surface mass and heat convergence near the Solomon Islands, Tuvalu, Kiribati, the Cook Islands and French Polynesia oppose, but can not cancel the regional signal of global mean sea-level rise.

Glacial Isostatic Adjustment and Contemporary Sea Level Rise: An Overview

NASA Astrophysics Data System (ADS)

Spada, Giorgio

2017-01-01

Glacial isostatic adjustment (GIA) encompasses a suite of geophysical phenomena accompanying the waxing and waning of continental-scale ice sheets. These involve the solid Earth, the oceans and the cryosphere both on short (decade to century) and on long (millennia) timescales. In the framework of contemporary sea-level change, the role of GIA is particular. In fact, among the processes significantly contributing to contemporary sea-level change, GIA is the only one for which deformational, gravitational and rotational effects are simultaneously operating, and for which the rheology of the solid Earth is essential. Here, I review the basic elements of the GIA theory, emphasizing the connections with current sea-level changes observed by tide gauges and altimetry. This purpose is met discussing the nature of the "sea-level equation" (SLE), which represents the basis for modeling the sea-level variations of glacial isostatic origin, also giving access to a full set of geodetic variations associated with GIA. Here, the SLE is employed to characterize the remarkable geographical variability of the GIA-induced sea-level variations, which are often expressed in terms of "fingerprints". Using harmonic analysis, the spatial variability of the GIA fingerprints is compared to that of other components of contemporary sea-level change. In closing, some attention is devoted to the importance of the "GIA corrections" in the context of modern sea-level observations, based on tide gauges or satellite altimeters.

Sea Level Rise Data Discovery

NASA Astrophysics Data System (ADS)

Quach, N.; Huang, T.; Boening, C.; Gill, K. M.

2016-12-01

Research related to sea level rise crosses multiple disciplines from sea ice to land hydrology. The NASA Sea Level Change Portal (SLCP) is a one-stop source for current sea level change information and data, including interactive tools for accessing and viewing regional data, a virtual dashboard of sea level indicators, and ongoing updates through a suite of editorial products that include content articles, graphics, videos, and animations. The architecture behind the SLCP makes it possible to integrate web content and data relevant to sea level change that are archived across various data centers as well as new data generated by sea level change principal investigators. The Extensible Data Gateway Environment (EDGE) is incorporated into the SLCP architecture to provide a unified platform for web content and science data discovery. EDGE is a data integration platform designed to facilitate high-performance geospatial data discovery and access with the ability to support multi-metadata standard specifications. EDGE has the capability to retrieve data from one or more sources and package the resulting sets into a single response to the requestor. With this unified endpoint, the Data Analysis Tool that is available on the SLCP can retrieve dataset and granule level metadata as well as perform geospatial search on the data. This talk focuses on the architecture that makes it possible to seamlessly integrate and enable discovery of disparate data relevant to sea level rise.

Large Variations in Ice Volume During the Middle Eocene "Doubthouse"

NASA Astrophysics Data System (ADS)

Dawber, C. F.; Tripati, A. K.

2008-12-01

The onset of glacial conditions in the Cenozoic is widely held to have begun ~34 million years ago, coincident with the Eocene-Oligocene boundary1. Warm and high pCO2 'greenhouse' intervals such as the Eocene are generally thought to be ice-free2. Yet the sequence stratigraphic record supports the occurrence of high-frequency sea-level change of tens of meters in the Middle and Late Eocene3, and large calcite and seawater δ18O excursions (~0.5-1.0 permil) have been reported in foraminifera from open ocean sediments4. As a result, the Middle Eocene is often considered the intermediary "doubthouse". The extent of continental ice during the 'doubthouse' is controversial, with estimates of glacioeustatic sea level fall ranging from 30 to 125m2,3,5. We present a new δ18Osw reconstruction for Ocean Drilling Project (ODP) Site 1209 in the tropical Pacific Ocean. It is the first continuous high-resolution record for an open-ocean site that is not directly influenced by changes in the carbonate compensation depth, which enables us to circumvent many of the limitations of existing records. Our record shows increases of 0.8 ± 0.2 (1 s.e) permil and 1.1 ± 0.2 permil at ~44-45 and ~42-41 Ma respectively, which suggests glacioeustatic sea level variations of ~90 m during the Middle Eocene. Modelling studies have shown that fully glaciating Antarctica during the Eocene should drive a change in seawater (δ18Osw) of 0.45 permil, and lower sea level by ~55 m6. Our results therefore support significant ice storage in both the Northern and Southern Hemisphere during the Middle Eocene 'doubthouse'. 1.Miller, Kenneth G. et al., 1990, Eocene-Oligocene sea-level changes in the New Jersey coastal plain linked to the deep-sea record. Geological Society of America Bulletin 102, 331-339 2.Pagani, M. et al., 2005, Marked decline in atmospheric carbon dioxide concentrations during the Paleogene. Science 309 (5734), 600-603. 3.Browning, J., Miller, K., and Pak, D., 1996, Global implications of Eocene Greenhouse and Doubthouse sequences on the New Jersey coastal plain; the Icehouse cometh. Geology 24 (7), 639-642. 4.Tripati, A.K., Backman, J., Elderfield, H., and Ferretti, P., 2005, Eocene bipolar glaciation associated with global carbon cycle changes. Nature 436 (7049), 341-346. 5.Edgar, K.M., Wilson, P.A., Sexton, P.F., and Suganuma, Y., 2007, No extreme bipolar glaciation during the main Eocene calcite compensation shift. Nature 448 (7156), 908-911. 6.DeConto, R. and Pollard, D., 2003, Rapid Cenozoic glaciation of Antarctic induced by declining atmospheric CO2. Nature 421, 245-249.

Preface

NASA Astrophysics Data System (ADS)

Woodworth, P. L.; Pugh, D. T.; De Ronde, J. G.; Warrick, R. G.; Hannah, J.

The measurement of sea level is of fundamental importance to a wide range of research in climatology, oceanography, geology and geodesy. This volume attempts to cover many aspects of the field. The volume opens with a description by Bolduc and Murty of one of the products stemming from the development of tide gauge networks in the northern and tropical Atlantic. This work is relevant to the growth of the Global Sea Level Observing System (GLOSS), the main goal of which is to provide the world with an efficient, coherent sea level monitoring system for oceanographic and climatological research. The subsequent four papers present results from the analysis of existing tide gauge data, including those datasets available from the Permanent Service for Mean Sea Level and the TOGA Sea Level Center. Two of the four, by Wróblewski and by Pasarić and Orlić, are concerned with European sea level changes, while Yu Jiye et al. discuss inter-annual changes in the Pacific, and Wang Baocan et al. describe variability in the Changjiang estuary in China. The papers by El-Abd and A wad, on Red Sea levels, are the only contributions to the volume from the large research community of geologists concerned with sea level changes.

Sea level change: lessons from the geologic record

USGS Publications Warehouse

,

1995-01-01

Rising sea level is potentially one of the most serious impacts of climatic change. Even a small sea level rise would have serious economic consequences because it would cause extensive damage to the world's coastal regions. Sea level can rise in the future because the ocean surface can expand due to warming and because polar ice sheets and mountain glaciers can melt, increasing the ocean's volume of water. Today, ice caps on Antarctica and Greenland contain 91 and 8 percent of the world's ice, respectively. The world's mountain glaciers together contain only about 1 percent. Melting all this ice would raise sea level about 80 meters. Although this extreme scenario is not expected, geologists know that sea level can rise and fall rapidly due to changing volume of ice on continents. For example, during the last ice age, about 18,000 years ago, continental ice sheets contained more than double the modem volume of ice. As ice sheets melted, sea level rose 2 to 3 meters per century, and possibly faster during certain times. During periods in which global climate was very warm, polar ice was reduced and sea level was higher than today.

Coastline Mapping and Cultural Review to Predict Sea Level Rise Impact on Hawaiian Archeological Sites

NASA Astrophysics Data System (ADS)

Clinton, J.

2017-12-01

Much of Hawaii's history is recorded in archeological sites. Researchers and cultural practitioners have been studying and reconstructing significant archeological sites for generations. Climate change, and more specifically, sea level rise may threaten these sites. Our research records current sea levels and then projects possible consequences to these cultural monuments due to sea level rise. In this mixed methods study, research scientists, cultural practitioners, and secondary students use plane-table mapping techniques to create maps of coastlines and historic sites. Students compare historical records to these maps, analyze current sea level rise trends, and calculate future sea levels. They also gather data through interviews with community experts and kupuna (elders). If climate change continues at projected rates, some historic sites will be in danger of negative impact due to sea level rise. Knowing projected sea levels at specific sites allows for preventative action and contributes to raised awareness of the impacts of climate change to the Hawaiian Islands. Students will share results with the community and governmental agencies in hopes of inspiring action to minimize climate change. It will take collaboration between scientists and cultural communities to inspire future action on climate change.

The Red Sea during the Last Glacial Maximum: implications for sea level reconstructions

NASA Astrophysics Data System (ADS)

Gildor, H.; Biton, E.; Peltier, W. R.

2006-12-01

The Red Sea (RS) is a semi-enclosed basin connected to the Indian Ocean via a narrow and shallow strait, and surrounded by arid areas which exhibits high sensitivity to atmospheric changes and sea level reduction. We have used the MIT GCM to investigate the changes in the hydrography and circulation in the RS in response to reduced sea level, variability in the Indian monsoons, and changes in atmospheric temperature and humidity that occurred during the Last Glacial Maximum (LGM). The model results show high sensitivity to sea level reduction especially in the salinity field (increasing with the reduction in sea level) together with a mild atmospheric impact. Sea level reduction decreases the stratification, increases subsurface temperatures, and alters the circulation pattern at the Strait of Bab el Mandab, which experiences a transition from submaximal flow to maximal flow. The reduction in sea level at LGM alters the location of deep water formation which shifts to an open sea convective site in the northern part of the RS compared to present day situation in which deep water is formed from the Gulf of Suez outflow. Our main result based on both the GCM and on a simple hydraulic control model which takes into account mixing process at the Strait of Bab El Mandeb, is that sea level was reduced by only ~100 m in the Bab El Mandeb region during the LGM, i.e. the water depth at the Hanish sill (the shallowest part in the Strait Bab el Mandab) was around 34 m. This result agrees with the recent reconstruction of the LGM low stand of the sea in this region based upon the ICE-5G (VM2) model of Peltier (2004).

Discovery of Sound in the Sea (DOSITS) Website Development

DTIC Science & Technology

2013-03-04

life affect ocean sound levels? • Science of Sound > Sounds in the Sea > How will ocean acidification affect ocean sound levels? • Science of Sound...Science of Sound > Sounds in the Sea > How does shipping affect ocean sound levels? • Science of Sound > Sounds in the Sea > How does marine

Estimation of Melt Pond Fractions on First Year Sea Ice Using Compact Polarization SAR

NASA Astrophysics Data System (ADS)

Li, Haiyan; Perrie, William; Li, Qun; Hou, Yijun

2017-10-01

Melt ponds are a common feature on Arctic sea ice. They are linked to the sea ice surface albedo and transmittance of energy to the ocean from the atmosphere and thus constitute an important process to parameterize in Arctic climate models and simulations. This paper presents a first attempt to retrieve the melt pond fraction from hybrid-polarized compact polarization (CP) SAR imagery, which has wider swath and shorter revisit time than the quad-polarization systems, e.g., from RADARSAT-2 (RS-2). The co-polarization (co-pol) ratio has been verified to provide estimates of melt pond fractions. However, it is a challenge to link CP parameters and the co-pol ratio. The theoretical possibility is presented, for making this linkage with the CP parameter C22/C11 (the ratio between the elements of the coherence matrix of CP SAR) for melt pond detection and monitoring with the tilted-Bragg scattering model for the ocean surface. The empirical transformed formulation, denoted as the "compact polarization and quad-pol" ("CPQP") model, is proposed, based on 2062 RS-2 quad-pol SAR images, collocated with in situ measurements. We compared the retrieved melt pond fraction with CP parameters simulated from quad-pol SAR data with results retrieved from the co-pol ratio from quad-pol SAR observations acquired during the Arctic-Ice (Arctic-Ice Covered Ecosystem in a Rapidly Changing Environment) field project. The results are shown to be comparable for observed melt pond measurements in spatial and temporal distributions. Thus, the utility of CP mode SAR for melt pond fraction estimation on first year level ice is presented.

Intermittent sea-level acceleration

NASA Astrophysics Data System (ADS)

Olivieri, M.; Spada, G.

2013-10-01

Using instrumental observations from the Permanent Service for Mean Sea Level (PSMSL), we provide a new assessment of the global sea-level acceleration for the last ~ 2 centuries (1820-2010). Our results, obtained by a stack of tide gauge time series, confirm the existence of a global sea-level acceleration (GSLA) and, coherently with independent assessments so far, they point to a value close to 0.01 mm/yr2. However, differently from previous studies, we discuss how change points or abrupt inflections in individual sea-level time series have contributed to the GSLA. Our analysis, based on methods borrowed from econometrics, suggests the existence of two distinct driving mechanisms for the GSLA, both involving a minority of tide gauges globally. The first effectively implies a gradual increase in the rate of sea-level rise at individual tide gauges, while the second is manifest through a sequence of catastrophic variations of the sea-level trend. These occurred intermittently since the end of the 19th century and became more frequent during the last four decades.

How will coastal sea level respond to changes in natural and anthropogenic forcings by 2100?

NASA Astrophysics Data System (ADS)

Jevrejeva, S.; Moore, J.; Grinsted, A.

2010-12-01

Sea level rise is perhaps the most damaging repercussion of global warming, as 150 million people live less than one meter above current high tides .Using an inverse statistical model we examine potential response in coastal sea level to the changes in natural and anthropogenic forcings by 2100. With six IPCC radiative forcing scenarios we estimate sea level rise of 0.6-1.6 m, with confidence limits of 0.59 m and 1.8 m. Projected impacts of solar and volcanic radiative forcings account only for, at maximum, 5% of total sea level rise, with anthropogenic greenhouse gasses being the dominant forcing. As alternatives to the IPCC projections, even the most intense century of volcanic forcing from the past 1000 years would result in 10-15 cm potential reduction of sea level rise. Stratospheric injections of SO2 equivalent to a Pinatubo eruption every 4 years would effectively just delay sea level rise by 12 -20 years.

Aral Sea basin: a sea dies, a sea also rises.

PubMed

Glantz, Michael H

2007-06-01

The thesis of this article is quite different from many other theses of papers, books, and articles on the Aral Sea. It is meant to purposely highlight the reality of the situation in Central Asia: the Aral Sea that was once a thriving body of water is no more. That sea is dead. What does exist in its place are the Aral seas: there are in essence three bodies of water, one of which is being purposefully restored and its level is rising (the Little Aral), and two others which are still marginally connected, although they continue to decline in level (the Big Aral West and the Big Aral East). In 1960 the level of the sea was about 53 m above sea level. By 2006 the level had dropped by 23 m to 30 m above sea level. This was not a scenario generated by a computer model. It was a process of environmental degradation played out in real life in a matter of a few decades, primarily as a result of human activities. Despite wishes and words to the contrary, it will take a heroic global effort to save what remains of the Big Aral. It would also take a significant degree of sacrifice by people and governments in the region to restore the Big Aral to an acceptable level, given that the annual rate of flow reaching the Amudarya River delta is less than a 10th of what it was several decades ago. Conferring World Heritage status to the Aral Sea(s) could spark restoration efforts for the Big Aral.

Coral Microatolls and Their Role as Fixed Biological Indicators of Holocene Sea-Level Changes

NASA Astrophysics Data System (ADS)

Woodroffe, C. D.; Smithers, S. G.; McGregor, H. V.

2008-12-01

Corals microatolls are individual colonies of massive coral that have grown up to a level at which further upward growth is constrained by exposure at low tide, and which then continue to grow outwards, resulting in a flat-topped discoid morphology. Typically, microatolls comprise a single colony of massive Porites up to several metres in diameter. Modern microatolls are living on their outer margin but are predominantly dead on their upper surface. Microatolls are fixed biological sea-level indicators of the former upper limits to coral growth providing information on sea level at several temporal scales. Fossil microatolls have been used extensively to reconstruct broad patterns of Holocene sea-level trends in the Indo-Pacific reef province. Where they are preserved at a height above that of their living counterparts in the eastern Indian Ocean, Southeast Asia, northern Australia, and across much of the equatorial Pacific Ocean, they indicate that reef flats have experienced relatively higher sea levels in the mid- and late Holocene. Progressively lower corals have been interpreted to record the fall in sea level to its present position over millennial time scales. Large specimens of microatolls can reach several metres in diameter and contain a growth record of tens to hundreds of years; the upper surfaces of these can be used to track the pattern of sea-level variation over several decades. In this paper we explore the potential for using concentric annuli and subtle undulations preserved on microatoll upper surfaces to interpret sea-level changes over decadal to millennial time scales. We demonstrate that in the central Pacific modern microatolls preserve a surface morphology that reflects oscillations of sea level associated with El Niño. We evaluate the extent to which similar fluctuations may be recorded in the morphology of Indian Ocean microatolls, and the circumstances which promote the preservation of these morphological records of sea-level change over longer time scales. We discuss the potential to reconstruct extended records of sea-level change by using geochemical signatures preserved within microatoll skeletons to improve cross-correlations between colonies, and assess the precision with which sea level can be inferred.

Global Sea Surface Temperature: A Harmonized Multi-sensor Time-series from Satellite Observations

NASA Astrophysics Data System (ADS)

Merchant, C. J.

2017-12-01

This paper presents the methods used to obtain a new global sea surface temperature (SST) dataset spanning the early 1980s to the present, intended for use as a climate data record (CDR). The dataset provides skin SST (the fundamental measurement) and an estimate of the daily mean SST at depths compatible with drifting buoys (adjusting for skin and diurnal variability). The depth SST provided enables the CDR to be used with in situ records and centennial-scale SST reconstructions. The new SST timeseries is as independent as possible from in situ observations, and from 1995 onwards is harmonized to an independent satellite reference (namely, SSTs from the Advanced Along Track Scanning Radiometer (Advanced ATSR)). This maximizes the utility of our new estimates of variability and long-term trends in interrogating previous datasets tied to in situ observations. The new SSTs include full resolution (swath, level 2) data, single-sensor gridded data (level 3, 0.05 degree latitude-longitude grid) and a multi-sensor optimal analysis (level 4, same grid). All product levels are consistent. All SSTs have validated uncertainty estimates attached. The sensors used include all Advanced Very High Resolution Radiometers from NOAA-6 onwards and the ATSR series. AVHRR brightness temperatures (BTs) are calculated from counts using a new in-flight re-calibration for each sensor, ultimately linked through to the AATSR BT calibration by a new harmonization technique. Artefacts in AVHRR BTs linked to varying instrument temperature, orbital regime and solar contamination are significantly reduced. These improvements in the AVHRR BTs (level 1) translate into improved cloud detection and SST (level 2). For cloud detection, we use a Bayesian approach for all sensors. For the ATSRs, SSTs are derived with sufficient accuracy and sensitivity using dual-view coefficients. This is not the case for single-view AVHRR observations, for which a physically based retrieval is employed, using a hybrid maximum a posteriori / maximum likelihood retrieval, which optimises retrieval uncertainty and SST sensitivity for climate applications. Validation results will be presented along with examples of the variability and trends in SST evident in the dataset.

Common behaviour of the Adriatic and Black Seas level in the 20th century as response to a Mediterranean forcing.

NASA Astrophysics Data System (ADS)

Scarascia, Luca; Stanica, Adrian; Dinu, Irina; Lionello, Piero

2017-04-01

The Adriatic and Black Seas are two marginal seas, both connected with the Eastern Mediterranean Sea, through the Otranto and Bosporus straits respectively. This contribution aims to evidence the fraction of the interannual sea level variability that is common to the two basins, likely an effect of the common forcing produced by Mediterranean Sea. In order to identify the common signal, the effect of the main local factors (wind, inverse barometer effect, steric effects, river runoff) determining the larger fraction of the interannual sea level variability have been identified and subtracted. Using 7 and 5 tide gauge timeseries located along the Adriatic and Black Sea coasts respectively, provided by PSMSL (Permanent Service of Mean Sea Level), two seamless timeseries representing the sea level of the basins from 1900 to 2009 have been produced. The comparison with satellite data, between 1993 and 2009, confirms that these reconstructions are representative of the actual sea level in the two basins (values are 0.87 for the Adriatic and 0.72 for the Black Sea). When considering local factors, for the Adriatic Sea the annual cycle of inverse barometer effect, steric contribution due to local temperature and salinity variations, and wind set-up have been computed. For the Black Sea, the wind factor (negligible in this case) has been replaced by the Danube river contribution estimated from the available discharge data of Sulina (one of the exits of the Danube delta). After subtracting these local factors from the observed sea level of each basin, the correlation between the residual time series amounts to 0.47, suggesting the presence of a common factor acting at Mediterranean scale, which can be attributed to the effect of the large-scale circulation on the mass exchange between the Mediterranean and the two local basins. The present analysis is still unable to explain a non-negligible fraction of interannual variability of sea level of the Black Sea. This is likely, to a substantial extent, due to uncertainties of hydrographic data caused by their irregular distribution in space and time and to the lack of regular records of past river discharge for most rivers contributing to the Black Sea.

Mid- to Late Holocene Sea-Level Record in French Polynesia, South-Central Pacific

NASA Astrophysics Data System (ADS)

Hallmann, N.; Camoin, G.; Vella, C.; Eisenhauer, A.; Samankassou, E.; Botella, A.; Milne, G. A.; Fietzke, J.; Dussouillez, P.; Plaine, J.

2014-12-01

The Mid- to Late Holocene provides the opportunity to study the coastal response to sea-level change that has a similar amplitude (i.e., a few decimetres up to 1 m) to the sea-level rise that is likely to occur before the end of the current century. Furthermore, this time period provides an important baseline of natural climate variability prior to the industrial revolution. This study aims to reconstruct Mid- to Late Holocene relative sea-level change in French Polynesia by examining coral reef records from ten islands, which represent ideal settings for accurate sea-level change studies because: 1) they can be regarded as tectonically stable during the relevant period (slow subsidence), 2) they are located far from former ice sheets ('far-field'), 3) they are characterized by a low tidal amplitude, and 4) they cover a wide range of latitudes which produces significantly improved constraints on GIA (Glacial Isostatic Adjustment) model parameters. The accurate reconstruction of sea-level change relies on absolute U/Th dating of in situ coral colonies and their accurate positioning via GPS RTK (Real Time Kinematic) measurements with a vertical and horizontal precision of ± 2.5 cm and ~1 cm, respectively. We focus mainly on the analysis of coral microatolls, which are sensitive low-tide recorders, as their vertical accretion is limited by the water level. Their growth patterns allow the reconstruction of low-amplitude and high-frequency sea-level changes on centennial to sub-decadal time scales. A sea-level rise of less than ~1 m is documented between 6 and 3-3.5 ka, and is followed by a gradual fall in sea level that started around 2 ka and persisted until the past few centuries. The reconstructed sea-level curve therefore extends the Tahiti sea-level curve [Deschamps et al., 2012, Nature, 483, 559-564], and is in good agreement with a geophysical model tuned to fit far-field deglacial records [Bassett et al., 2005, Science, 309, 925-928].

Influence of ENSO on coastal flood hazard and exposure at the global-scale

NASA Astrophysics Data System (ADS)

Muis, S.; Haigh, I. D.; Guimarães Nobre, G.; Aerts, J.; Ward, P.

2017-12-01

The El Niño-Southern Oscillation (ENSO) is the dominant signal of interannual climate variability. The unusually warm (El Niño) and cold (La Niña) oceanic and atmospheric conditions in the tropical Pacific drives interannual variability in both mean and extreme sea levels, which in turn may influence the probabilities and impacts of coastal flooding. We assess the influence of ENSO on coastal flood hazard and exposure using daily timeseries from the Global Time and Surge Reanalysis (GTSR) dataset (Muis et al., 2016). As the GTSR timeseries do not include steric effects (i.e. density differences), we improve the GTSR timeseries by adding steric sea levels. Evaluation against observed sea levels shows that the including steric sea levels leads to a much better representation of the seasonal and interannual variability. We show that sea level anomalies occur during ENSO years with higher sea levels during La Niña in the South-Atlantic, Indian Ocean and the West Pacific, whereas sea levels are lower in the east Pacific. The pattern is generally inversed for El Niño. We also find an effect of ENSO in the number of people exposed to coastal flooding. Although the effect is minor at the global-scale, it may be important for flood risk management to consider at the national or sub national levels. Previous studies at the global-scale have used tide gauge observation to assess the influence of ENSO on extreme sea levels. The advantage of our approach over observations is that GTSR provides a consistent dataset with a full global coverage for the period 1979-2014. This allows us to assess ENSO's influence on sea level extremes anywhere in the world. Furthermore, it enables us to also calculate the impacts of extreme sea levels in terms of coastal flooding and exposed population. ReferencesMuis et al (2016) A global reanalysis of storm surges and extreme sea levels. Nature Communications.7:11969. doi:10.1038/ncomms11969.

Holocene relative sea-level change in Hiroshima Bay, Japan: A semi-quantitative reconstruction based on ostracodes

USGS Publications Warehouse

Yasuhara, Moriaki; Seto, Koji

2006-01-01

Holocene relative sea-level changes in Hiroshima Bay were reconstructed from fossil ostracodes from a core, using a semi-quantitative method. In Hiroshima Bay, relative sea level rose rapidly (about 25 m) between ca. 9000 cal yr BP and ca. 5800 cal yr BP, after which it gradually fell (about 5 m) to its present level. The peak in relative sea level occurred at ca. 5800 cal yr BP. The sea-level curve for Hiroshima Bay is similar to curves for tectonically stable areas of Japan (e.g., Osaka Bay). ?? by the Palaeontological Society of Japan.

Rolling Deck to Repository (R2R): Linking and Integrating Data for Oceanographic Research

NASA Astrophysics Data System (ADS)

Arko, R. A.; Chandler, C. L.; Clark, P. D.; Shepherd, A.; Moore, C.

2012-12-01

The Rolling Deck to Repository (R2R) program is developing infrastructure to ensure the underway sensor data from NSF-supported oceanographic research vessels are routinely and consistently documented, preserved in long-term archives, and disseminated to the science community. We have published the entire R2R Catalog as a Linked Data collection, making it easily accessible to encourage linking and integration with data at other repositories. We are developing the R2R Linked Data collection with specific goals in mind: 1.) We facilitate data access and reuse by providing the richest possible collection of resources to describe vessels, cruises, instruments, and datasets from the U.S. academic fleet, including data quality assessment results and clean trackline navigation. We are leveraging or adopting existing community-standard concepts and vocabularies, particularly concepts from the Biological and Chemical Oceanography Data Management Office (BCO-DMO) ontology and terms from the pan-European SeaDataNet vocabularies, and continually re-publish resources as new concepts and terms are mapped. 2.) We facilitate data citation through the entire data lifecycle from field acquisition to shoreside archiving to (ultimately) global syntheses and journal articles. We are implementing globally unique and persistent identifiers at the collection, dataset, and granule levels, and encoding these citable identifiers directly into the Linked Data resources. 3.) We facilitate linking and integration with other repositories that publish Linked Data collections for the U.S. academic fleet, such as BCO-DMO and the Index to Marine and Lacustrine Geological Samples (IMLGS). We are initially mapping datasets at the resource level, and plan to eventually implement rule-based mapping at the concept level. We work collaboratively with partner repositories to develop best practices for URI patterns and consensus on shared vocabularies. The R2R Linked Data collection is implemented as a lightweight "virtual RDF graph" generated on-the-fly from our SQL database using the D2RQ (http://d2rq.org) package. In addition to the default SPARQL endpoint for programmatic access, we are developing a Web-based interface from open-source software components that offers user-friendly browse and search.

Holocene sea level and climate change in the Black Sea: Multiple marine incursions related to freshwater discharge events

USGS Publications Warehouse

Martin, R.E.; Leorri, E.; McLaughlin, P.P.

2007-01-01

Repeated marine invasions of the Black Sea during the Holocene have been inferred by many eastern scientists as resulting from episodes of marine inflow from the Mediterranean beneath a brackish outflow from the Black Sea. We support this scenario but a fundamental question remains: What caused the repeated marine invasions? We offer an hypothesis for the repeated marine invasions of the Black Sea based on: (1) the overall similarity of sea-level curves from both tectonically quiescent and active margins of the Black Sea and their similarity to a sequence stratigraphic record from the US mid-Atlantic coast. The similarity of the records from two widely-separated regions suggests their common response to documented Holocene climate ocean-atmosphere reorganizations (coolings); (2) the fact that in the modern Black Sea, freshwater runoff from surrounding rivers dominates over evaporation, so that excess runoff might have temporarily raised Black Sea level (although the Black Sea would have remained brackish). Following the initial invasion of the Black Sea by marine Mediterranean waters (through the Marmara Sea) in the early Holocene, repeated marine incursions were modulated, or perhaps even caused, by freshwater discharge to the Black Sea. Climatic amelioration (warming) following each documented ocean-atmosphere reorganization during the Holocene likely shifted precipitation patterns in the surrounding region and caused mountain glaciers to retreat, increasing freshwater runoff above modern values and temporarily contributing to an increase of Black Sea level. Freshwater-to-brackish water discharges into the Black Sea initially slowed marine inflow but upon mixing of runoff with more marine waters beneath them and their eventual exit through the Bosphorus, marine inflow increased again, accounting for the repeated marine invasions. The magnitude of the hydrologic and sea-level fluctuations became increasingly attenuated through the Holocene, as reflected by Black Sea level curves. ?? 2006 Elsevier Ltd and INQUA.

North Sea ecosystem change from swimming crabs to seagulls

PubMed Central

Luczak, C.; Beaugrand, G.; Lindley, J. A.; Dewarumez, J-M.; Dubois, P. J.; Kirby, R. R.

2012-01-01

A recent increase in sea temperature has established a new ecosystem dynamic regime in the North Sea. Climate-induced changes in decapods have played an important role. Here, we reveal a coincident increase in the abundance of swimming crabs and lesser black-backed gull colonies in the North Sea, both in time and in space. Swimming crabs are an important food source for lesser black-backed gulls during the breeding season. Inhabiting the land, but feeding mainly at sea, lesser black-backed gulls provide a link between marine and terrestrial ecosystems, since the bottom-up influence of allochthonous nutrient input from seabirds to coastal soils can structure the terrestrial food web. We, therefore, suggest that climate-driven changes in trophic interactions in the marine food web may also have ensuing ramifications for the coastal ecology of the North Sea. PMID:22764111