Clay mineralogical record on the upper continental slope of the northwestern South China Sea since the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

CHEN, Q.; Liu, Z.; Stattegger, K.

2012-12-01

Clay mineralogy of two gravity cores (18428 and 18429) on the upper continental slope of the northwestern South China Sea was investigated in order to understand terrigenous sediment sources and to evaluate the contribution from the Red River since the Late Glacial Maximum. Planktonic foraminiferal oxygen isotope and carbonate stratigraphies suggest that Core 18428 is constrained in Holocene while Core 18429 covers the period of MIS 1-2. Clay mineral assemblages of two cores are composed mainly of smectite (18-57%) and illite (21-41%), with minor chlorite (12-21%) and kaolinite (8-26%). In despite of relatively constant values of illite crystallinity, ranging among 0.14°-0.20° Δ2θ, the time series variation in clay mineral distributions indicates a strong glacial-interglacial shift. Contents of illite, chlorite, and kaolinite (Core 18429) in the Holocene are lower than in the glacial period, and vice versa for the smectite content. The provenance analysis based on clay mineralogy suggests the Red River as a predominant sedimentary source of illite, chlorite, and kaolinite during all the depositional period of MIS 1-2. The sea level change actually controlled the variations of clay mineral assemblages on the upper slope since the Last Glacial Maximum. When the sea level was low during the last glacial period, more terrigenous sediments from the Red River could reach the continental slope in the northwestern South China Sea. However, when the sea level is closed to the present situation during the Holocene, most of Red River sediments could be trapped in the Gulf of Tonkin, instead of draining in the deep South China Sea.

Modelling sea level data from China and Malay-Thailand to estimate Holocene ice-volume equivalent sea level change

NASA Astrophysics Data System (ADS)

Bradley, Sarah L.; Milne, Glenn A.; Horton, Benjamin P.; Zong, Yongqiang

2016-04-01

This study presents a new model of Holocene ice-volume equivalent sea level (ESL), extending a previously published global ice sheet model (Bassett et al., 2005), which was unconstrained from 10 kyr BP to present. This new model was developed by comparing relative sea level (RSL) predictions from a glacial isostatic adjustment (GIA) model to a suite of Holocene sea level index points from China and Malay-Thailand. Three consistent data-model misfits were found using the Bassett et al. (2005) model: an over-prediction in the height of maximum sea level, the timing of this maximum, and the temporal variation of sea level from the time of the highstand to present. The data-model misfits were examined for a large suite of ESL scenarios and a range of earth model parameters to determine an optimum model of Holocene ESL. This model is characterised by a slowdown in melting at ∼7 kyr BP, associated with the final deglaciation of the Laurentide Ice Sheet, followed by a continued rise in ESL until ∼1 kyr BP of ∼5.8 m associated with melting from the Antarctic Ice Sheet. It was not possible to identify an earth viscosity model that provided good fits for both regions; with the China data preferring viscosity values in the upper mantle of less than 1.5 × 1020 Pa s and the Malay-Thailand data preferring greater values. We suggest that this inference of a very weak upper mantle for the China data originates from the nearby subduction zone and Hainan Plume. The low viscosity values may also account for the lack of a well-defined highstand at the China sites.

Sea level and global ice volumes from the Last Glacial Maximum to the Holocene.

PubMed

Lambeck, Kurt; Rouby, Hélène; Purcell, Anthony; Sun, Yiying; Sambridge, Malcolm

2014-10-28

The major cause of sea-level change during ice ages is the exchange of water between ice and ocean and the planet's dynamic response to the changing surface load. Inversion of ∼1,000 observations for the past 35,000 y from localities far from former ice margins has provided new constraints on the fluctuation of ice volume in this interval. Key results are: (i) a rapid final fall in global sea level of ∼40 m in <2,000 y at the onset of the glacial maximum ∼30,000 y before present (30 ka BP); (ii) a slow fall to -134 m from 29 to 21 ka BP with a maximum grounded ice volume of ∼52 × 10(6) km(3) greater than today; (iii) after an initial short duration rapid rise and a short interval of near-constant sea level, the main phase of deglaciation occurred from ∼16.5 ka BP to ∼8.2 ka BP at an average rate of rise of 12 m⋅ka(-1) punctuated by periods of greater, particularly at 14.5-14.0 ka BP at ≥40 mm⋅y(-1) (MWP-1A), and lesser, from 12.5 to 11.5 ka BP (Younger Dryas), rates; (iv) no evidence for a global MWP-1B event at ∼11.3 ka BP; and (v) a progressive decrease in the rate of rise from 8.2 ka to ∼2.5 ka BP, after which ocean volumes remained nearly constant until the renewed sea-level rise at 100-150 y ago, with no evidence of oscillations exceeding ∼15-20 cm in time intervals ≥200 y from 6 to 0.15 ka BP.

Sea level and global ice volumes from the Last Glacial Maximum to the Holocene

PubMed Central

Lambeck, Kurt; Rouby, Hélène; Purcell, Anthony; Sun, Yiying; Sambridge, Malcolm

2014-01-01

The major cause of sea-level change during ice ages is the exchange of water between ice and ocean and the planet’s dynamic response to the changing surface load. Inversion of ∼1,000 observations for the past 35,000 y from localities far from former ice margins has provided new constraints on the fluctuation of ice volume in this interval. Key results are: (i) a rapid final fall in global sea level of ∼40 m in <2,000 y at the onset of the glacial maximum ∼30,000 y before present (30 ka BP); (ii) a slow fall to −134 m from 29 to 21 ka BP with a maximum grounded ice volume of ∼52 × 106 km3 greater than today; (iii) after an initial short duration rapid rise and a short interval of near-constant sea level, the main phase of deglaciation occurred from ∼16.5 ka BP to ∼8.2 ka BP at an average rate of rise of 12 m⋅ka−1 punctuated by periods of greater, particularly at 14.5–14.0 ka BP at ≥40 mm⋅y−1 (MWP-1A), and lesser, from 12.5 to 11.5 ka BP (Younger Dryas), rates; (iv) no evidence for a global MWP-1B event at ∼11.3 ka BP; and (v) a progressive decrease in the rate of rise from 8.2 ka to ∼2.5 ka BP, after which ocean volumes remained nearly constant until the renewed sea-level rise at 100–150 y ago, with no evidence of oscillations exceeding ∼15–20 cm in time intervals ≥200 y from 6 to 0.15 ka BP. PMID:25313072

Coastal setback line for the Kyparissiakos Gulf (Ionian Sea, Greece) according to the Mediterranean ICZM protocol

NASA Astrophysics Data System (ADS)

Poulos, Serafim; George, Ghionis; Karditsa, Aikaterini

2017-04-01

The present investigation concerns the application of the Article 8-2 of the Mediterranean ICZM protocol in the environmentally sensitive coastal dune field of the central part of the Kyparissiakos Gulf (Ionian Sea, Greece). The Kyparissiakos dune field, comprising a set of coastal ecosystems of exceptional value, needs effective ICZM and, amongst all, has to consider the issue of Sea-Level Rise (SLR). The dune field consists of "parabolic" type dunes that are stable and subjected locally to human interference. It consists of four shore-parallel dune lines: the outer (and most recently formed) 1st dune line has formed during the last 500 years, the 2nd during the last 1000 years, whilst the 3rd and 4th lines have formed not later than 1600 years BP (Poulos et al., 2012). Moreover, the four dune lines (from the youngest to the oldest) lie at distances of approximately 60 m, 100 m, 200 m and 600 m from the coastline, having maximum heights of 4 m, 6 m, 10 m, and 10-12 m, respectively. The dune field, in general, is in equilibrium with the current nearshore hydrodynamics as the width of the beach zone is greater than the maximum run-up length (not included storm surge). The maximum wave run-up height (R), relative to the mean sea level, has been calculated by applying Komar's (1998) equation: R = 0.36 ṡ g0.5 ṡ S ṡ Ho0.5 ṡ T (g: acceleration of gravity; Ho: maximum offshore wave height; T: corresponding maximum wave period; S: tangential beach slope). Thus, the wave run-up due to the highest incoming waves can reach elevations of the order of 1.6m in the case of the NW waves (Ho=6m, T=9 s) and 2m in the case of W and SW waves (Ho=6.4m, T=6.4s). These elevations correspond to 25m and 40 m of tangential distances on the beach surface, which are less than the current beach width (> 60 m). However, if the maximum wave heights coincide with the maximum storm surge (0.5 m) observed in the area, wave action can reach and erode the foot of the 1st dune line. Thus, for the current sea level, the maximum wave excursion would reach the line along the foot of the 1st dune line. The application of the Barcelona 2008 protocol requires a free zone of 100 m, landwards of the maximum wave elevation, in this case reaching the 2nd dune line. If the moderate scenario of sea level rise ca. 0.4 m (IPCC, 2013) is realised, extensive erosion is expected to take place, leading to the destruction of the 1st dune line and the formation of a new shoreline close to the foot of the 2nd dune line, which might be partially destroyed and reshaped by the transgressive landward transfer of dune material. On the basis of the above, for this particular sensitive coastal environment, even the 100 m set-back line might be inadequate, even for the moderate sea level rise scenario for the year 2100.

Vulnerability assessment of the impact of sea-level rise and flooding on the Moroccan coast: The case of the Mediterranean eastern zone

NASA Astrophysics Data System (ADS)

Snoussi, Maria; Ouchani, Tachfine; Niazi, Saïda

2008-04-01

The eastern part of the Mediterranean coast of Morocco is physically and socio-economically vulnerable to accelerated sea-level rise, due to its low topography and its high ecological and touristic value. Assessment of the potential land loss by inundation has been based on empirical approaches using a minimum inundation level of 2 m and a maximum inundation level of 7 m, where scenarios for future sea-level rise range from 200 to 860 mm, with a 'best estimate' of 490 mm. The socio-economic impacts have been based on two possible alternative futures: (1) a 'worst-case' scenario, obtained by combining the 'economic development first' scenario with the maximum inundation level; and (2) a 'best-case' scenario, by combining the 'sustainability first' scenario with the minimum inundation level. Inundation analysis, based on Geographical Information Systems and a modelling approach to erosion, has identified both locations and the socioeconomic sectors that are most at risk to accelerated sea-level rise. Results indicate that 24% and 59% of the area will be lost by flooding at minimum and maximum inundation levels, respectively. The most severely impacted sectors are expected to be the residential and recreational areas, agricultural land, and the natural ecosystem. Shoreline erosion will affect 50% and 70% of the total area in 2050 and 2100, respectively. Potential strategies to ameliorate the impact of seawater inundation include: wetland preservation; beach nourishment at tourist resorts; and the afforestation of dunes. As this coast is planned to become one of the most developed tourist resorts in Morocco by 2010, measures such as building regulation, urban growth planning and development of an Integrated Coastal Zone Management Plan, are recommended for the region.

20 Years of sea-levels, accretion, and vegetation on two Long Island Sound salt marshes

EPA Science Inventory

The long-term 1939-2013 rate of RSLR (Relative Sea-Level Rise) at the New London, CT tide gauge is ~2.6 mm/yr, near the maximum rate of salt marsh accretion reported in eastern Long Island Sound salt marshes. Consistent with recent literature RSLR at New London has accelerated si...

Interhemispheric ice-sheet synchronicity during the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Weber, M. E.; Clark, P. U.; Ricken, W.; Mitrovica, J. X.; Hostetler, S. W.; Kuhn, G.

2012-04-01

The timing of the last maximum extent of the Antarctic ice sheets relative to those in the Northern Hemisphere remains poorly understood because only a few findings with robust chronologies exist for Antarctic ice sheets. We developed a chronology for the Weddell Sea sector of the East Antarctic ice sheet that, combined with ages from other Antarctic ice-sheet sectors, indicates the advance to their maximum extent at 29 -28 ka, and retreat from their maximum extent at 19 ka was nearly synchronous with Northern Hemisphere ice sheets (Weber, M.E., Clark, P. U., Ricken, W., Mitrovica, J. X., Hostetler, S. W., and Kuhn, G. (2011): Interhemispheric ice-sheet synchronicity during the Last Glacial Maximum. - Science, 334, 1265-1269, doi: 10.1126:science.1209299). As for the deglaciation, modeling studies suggest a late ice-sheet retreat starting around 14 ka BP and ending around 7 ka BP with a large impact of an unstable West Antarctic Ice Sheet (WAIS) and a small impact of a stable East Antarctic Ice Sheet (EAIS). However, the Weddell Sea sites studied here, as well as sites from the Scotia Sea, provide evidence that specifically the EAIS responded much earlier, possibly provided a significant contribution to the last sea-level rise, and was much more dynamic than previously thought. Using the results of an atmospheric general circulation we conclude that surface climate forcing of Antarctic ice mass balance would likely cause an opposite response, whereby a warming climate would increase accumulation but not surface melting. Furthermore, our new data support teleconnections involving a sea-level fingerprint forced from Northern Hemisphere ice sheets as indicated by gravitational modeling. Also, changes in North Atlantic Deepwater formation and attendant heat flux to Antarctic grounding lines may have contributed to synchronizing the hemispheric ice sheets.

Exploratory drilling and aquifer testing at the Kipahulu District, Haleakala National Park, Maui, Hawaii

USGS Publications Warehouse

Souza, W.R.

1983-01-01

An exploratory well, located at 388 feet above sea level in Kipahulu Valley on Maui, Hawaii, was completed and tested in October 1980. The 410-foot well penetrates a series of very dense basaltic lava flows of the Hana Formation. At an elevation of 10 feet above mean sea level, the well penetrated a water-bearing zone of permeable basaltic rock. Water from this zone had a head of about 76 feet above sea level. In October of 1980, the well was pump tested for 9 hours at various discharge rates up to 350 gallons per minute with a maximum drawdown of about 12 feet. Based on the test data, the well should produce water at a rate of 200 gallons per minute with a drawdown of less than 3 feet. The water level in the well was continuously monitored from October 1980 to mid-November 1981, during which period a maximum decline of 20 feet was recorded. Water level fluctuations in the well can be correlated to the flow in nearby Palikea Stream. The long-term water level in the well should stabilize at about 75 feet above sea level. Water quality was excellent. The total dissolved-solids content was 49 milligrams per liter and the chloride content was 4.2 milligrams per liter. (USGS)

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

Coralgal reef morphology records punctuated sea-level rise during the last deglaciation.

PubMed

Khanna, Pankaj; Droxler, André W; Nittrouer, Jeffrey A; Tunnell, John W; Shirley, Thomas C

2017-10-19

Coralgal reefs preserve the signatures of sea-level fluctuations over Earth's history, in particular since the Last Glacial Maximum 20,000 years ago, and are used in this study to indicate that punctuated sea-level rise events are more common than previously observed during the last deglaciation. Recognizing the nature of past sea-level rises (i.e., gradual or stepwise) during deglaciation is critical for informing models that predict future vertical behavior of global oceans. Here we present high-resolution bathymetric and seismic sonar data sets of 10 morphologically similar drowned reefs that grew during the last deglaciation and spread 120 km apart along the south Texas shelf edge. Herein, six commonly observed terrace levels are interpreted to be generated by several punctuated sea-level rise events forcing the reefs to shrink and backstep through time. These systematic and common terraces are interpreted to record punctuated sea-level rise events over timescales of decades to centuries during the last deglaciation, previously recognized only during the late Holocene.

The distribution of vesicular-arbuscular mycorrhizal fungi in India.

PubMed

Rani, R; Mukerji, K G

1990-01-01

Vesicular-arbuscular mycorrhizal fungi are widely distributed throughout the area studied including different altitudes ranging from sea level to 2500 ft above sea level. VAM fungi were recorded from 88% of the sites examined with Glomus fasciculatum and Glomus macrocarpum being the most commonly recorded. Mean species diversity was found to be maximum in the areas thickly vegetated and undisturbed.

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.

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.

Assessment of the impact of sea-level rise due to climate change on coastal groundwater discharge.

PubMed

Masciopinto, Costantino; Liso, Isabella Serena

2016-11-01

An assessment of sea intrusion into coastal aquifers as a consequence of local sea-level rise (LSLR) due to climate change was carried out at Murgia and Salento in southern Italy. The interpolation of sea-level measurements at three tide-gauge stations was performed during the period of 2000 to 2014. The best fit of measurements shows an increasing rate of LSLR ranging from 4.4mm/y to 8.8mm/y, which will result in a maximum LSLR of approximately 2m during the 22nd century. The local rate of sea-level rise matches recent 21st and 22nd century projections of mean global sea-level rise determined by other researchers, which include increased melting rates of the Greenland and Antarctic ice sheets, the effect of ocean thermal expansion, the melting of glaciers and ice caps, and changes in the quantity of stored land water. Subsequently, Ghyben-Herzberg's equation for the freshwater/saltwater interface was rewritten in order to determine the decrease in groundwater discharge due to the maximum LSLR. Groundwater flow simulations and ArcGIS elaborations of digital elevation models of the coast provided input data for the Ghyben-Herzberg calculation under the assumption of head-controlled systems. The progression of seawater intrusion due to LSLR suggests an impressive depletion of available groundwater discharge during the 22nd century, perhaps as much as 16.1% of current groundwater pumping for potable water in Salento. Copyright © 2016 Elsevier B.V. All rights reserved.

Sources and levels of ambient ocean sound near the Antarctic Peninsula.

PubMed

Dziak, Robert P; Bohnenstiehl, DelWayne R; Stafford, Kathleen M; Matsumoto, Haruyoshi; Park, Minkyu; Lee, Won Sang; Fowler, Matt J; Lau, Tai-Kwan; Haxel, Joseph H; Mellinger, David K

2015-01-01

Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Peninsula region) from 2005 to 2009 to record ambient ocean sound at frequencies of up to 125 and 500 Hz. Icequakes, which are broadband, short duration signals derived from fracturing of large free-floating icebergs, are a prominent feature of the ocean soundscape. Icequake activity peaks during austral summer and is minimum during winter, likely following freeze-thaw cycles. Iceberg grounding and rapid disintegration also releases significant acoustic energy, equivalent to large-scale geophysical events. Overall ambient sound levels can be as much as ~10-20 dB higher in the open, deep ocean of the Scotia Sea compared to the relatively shallow Bransfield Strait. Noise levels become lowest during the austral winter, as sea-ice cover suppresses wind and wave noise. Ambient noise levels are highest during austral spring and summer, as surface noise, ice cracking and biological activity intensifies. Vocalizations of blue (Balaenoptera musculus) and fin (B. physalus) whales also dominate the long-term spectra records in the 15-28 and 89 Hz bands. Blue whale call energy is a maximum during austral summer-fall in the Drake Passage and Bransfield Strait when ambient noise levels are a maximum and sea-ice cover is a minimum. Fin whale vocalizations were also most common during austral summer-early fall months in both the Bransfield Strait and Scotia Sea. The hydrophone data overall do not show sustained anthropogenic sources (ships and airguns), likely due to low coastal traffic and the typically rough weather and sea conditions of the Southern Ocean.

Sources and Levels of Ambient Ocean Sound near the Antarctic Peninsula

PubMed Central

Dziak, Robert P.; Bohnenstiehl, DelWayne R.; Stafford, Kathleen M.; Matsumoto, Haruyoshi; Park, Minkyu; Lee, Won Sang; Fowler, Matt J.; Lau, Tai-Kwan; Haxel, Joseph H.; Mellinger, David K.

2015-01-01

Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Peninsula region) from 2005 to 2009 to record ambient ocean sound at frequencies of up to 125 and 500 Hz. Icequakes, which are broadband, short duration signals derived from fracturing of large free-floating icebergs, are a prominent feature of the ocean soundscape. Icequake activity peaks during austral summer and is minimum during winter, likely following freeze-thaw cycles. Iceberg grounding and rapid disintegration also releases significant acoustic energy, equivalent to large-scale geophysical events. Overall ambient sound levels can be as much as ~10–20 dB higher in the open, deep ocean of the Scotia Sea compared to the relatively shallow Bransfield Strait. Noise levels become lowest during the austral winter, as sea-ice cover suppresses wind and wave noise. Ambient noise levels are highest during austral spring and summer, as surface noise, ice cracking and biological activity intensifies. Vocalizations of blue (Balaenoptera musculus) and fin (B. physalus) whales also dominate the long-term spectra records in the 15–28 and 89 Hz bands. Blue whale call energy is a maximum during austral summer-fall in the Drake Passage and Bransfield Strait when ambient noise levels are a maximum and sea-ice cover is a minimum. Fin whale vocalizations were also most common during austral summer-early fall months in both the Bransfield Strait and Scotia Sea. The hydrophone data overall do not show sustained anthropogenic sources (ships and airguns), likely due to low coastal traffic and the typically rough weather and sea conditions of the Southern Ocean. PMID:25875205

Marine record of late quaternary glacial-interglacial fluctuations in the Ross Sea and evidence for rapid, episodic sea level change due to marine ice sheet collapse

NASA Technical Reports Server (NTRS)

Anderson, John B.

1991-01-01

Some of the questions to be addressed by SeaRISE include: (1) what was the configuration of the West Antarctic ice sheet during the last glacial maximum; (2) What is its configuration during a glacial minimum; and (3) has it, or any marine ice sheet, undergone episodic rapid mass wasting. These questions are addressed in terms of what is known about the history of the marine ice sheet, specifically in Ross Sea, and what further studies are required to resolve these problems. A second question concerns the extent to which disintegration of marine ice sheets may result in rises in sea level that are episodic in nature and extremely rapid, as suggested by several glaciologists. Evidence that rapid, episodic sea level changes have occurred during the Holocene is also reviewed.

Predicting location-specific extreme coastal floods in the future climate by introducing a probabilistic method to calculate maximum elevation of the continuous water mass caused by a combination of water level variations and wind waves

NASA Astrophysics Data System (ADS)

Leijala, Ulpu; Björkqvist, Jan-Victor; Johansson, Milla M.; Pellikka, Havu

2017-04-01

Future coastal management continuously strives for more location-exact and precise methods to investigate possible extreme sea level events and to face flooding hazards in the most appropriate way. Evaluating future flooding risks by understanding the behaviour of the joint effect of sea level variations and wind waves is one of the means to make more comprehensive flooding hazard analysis, and may at first seem like a straightforward task to solve. Nevertheless, challenges and limitations such as availability of time series of the sea level and wave height components, the quality of data, significant locational variability of coastal wave height, as well as assumptions to be made depending on the study location, make the task more complicated. In this study, we present a statistical method for combining location-specific probability distributions of water level variations (including local sea level observations and global mean sea level rise) and wave run-up (based on wave buoy measurements). The goal of our method is to obtain a more accurate way to account for the waves when making flooding hazard analysis on the coast compared to the approach of adding a separate fixed wave action height on top of sea level -based flood risk estimates. As a result of our new method, we gain maximum elevation heights with different return periods of the continuous water mass caused by a combination of both phenomena, "the green water". We also introduce a sensitivity analysis to evaluate the properties and functioning of our method. The sensitivity test is based on using theoretical wave distributions representing different alternatives of wave behaviour in relation to sea level variations. As these wave distributions are merged with the sea level distribution, we get information on how the different wave height conditions and shape of the wave height distribution influence the joint results. Our method presented here can be used as an advanced tool to minimize over- and underestimation of the combined effect of sea level variations and wind waves, and to help coastal infrastructure planning and support smooth and safe operation of coastal cities in a changing climate.

Minimum and Maximum Potential Contributions to Future Sea Level Rise from Polar Ice Sheets

NASA Astrophysics Data System (ADS)

Deconto, R. M.; Pollard, D.

2017-12-01

New climate and ice-sheet modeling, calibrated to past changes in sea-level, is painting a stark picture of the future fate of the great polar ice sheets if greenhouse gas emissions continue unabated. This is especially true for Antarctica, where a substantial fraction of the ice sheet rests on bedrock more than 500-meters below sea level. Here, we explore the sensitivity of the polar ice sheets to a warming atmosphere and ocean under a range of future greenhouse gas emissions scenarios. The ice sheet-climate-ocean model used here considers time-evolving changes in surface mass balance and sub-ice oceanic melting, ice deformation, grounding line retreat on reverse-sloped bedrock (Marine Ice Sheet Instability), and newly added processes including hydrofracturing of ice shelves in response to surface meltwater and rain, and structural collapse of thick, marine-terminating ice margins with tall ice-cliff faces (Marine Ice Cliff Instability). The simulations improve on previous work by using 1) improved atmospheric forcing from a Regional Climate Model and 2) a much wider range of model physical parameters within the bounds of modern observations of ice dynamical processes (particularly calving rates) and paleo constraints on past ice-sheet response to warming. Approaches to more precisely define the climatic thresholds capable of triggering rapid and potentially irreversible ice-sheet retreat are also discussed, as is the potential for aggressive mitigation strategies like those discussed at the 2015 Paris Climate Conference (COP21) to substantially reduce the risk of extreme sea-level rise. These results, including physics that consider both ice deformation (creep) and calving (mechanical failure of marine terminating ice) expand on previously estimated limits of maximum rates of future sea level rise based solely on kinematic constraints of glacier flow. At the high end, the new results show the potential for more than 2m of global mean sea level rise by 2100, implying that physically plausible upper limits on future sea-level rise might need to be reconsidered.

Sea-Level Change in the Russian Arctic Since the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Horton, B.; Baranskaya, A.; Khan, N.; Romanenko, F. A.

2017-12-01

Relative sea-level (RSL) databases that span the Last Glacial Maximum (LGM) to present have been used to infer changes in climate, regional ice sheet variations, the rate and geographic source of meltwater influx, and the rheological structure of the solid Earth. Here, we have produced a quality-controlled RSL database for the Russian Arctic since the LGM. The database contains 394 index points, which locate the position of RSL in time and space, and 244 limiting points, which constrain the minimum or maximum limit of former sea level. In the western part of the Russian Arctic (Barents and White seas,) RSL was driven by glacial isostatic adjustment (GIA) due to deglaciation of the Scandinavian ice sheet, which covered the Baltic crystalline shield at the LGM. RSL data from isolation basins show rapid RSL from 80-100 m at 11-12 ka BP to 15-25 m at 4-5 ka BP. In the Arctic Islands of Franz-Joseph Land and Novaya Zemlya, RSL data from dated driftwood in raised beaches show a gradual fall from 25-35 m at 9-10 ka BP to 5-10 m at 3 ka BP. In the Russian plain, situated at the margins of the formerly glaciated Baltic crystalline shield, RSL data from raised beaches and isolation basins show an early Holocene rise from less than -20 m at 9-11 ka BP before falling in the late Holocene, illustrating the complex interplay between ice-equivalent meltwater input and GIA. The Western Siberian Arctic (Yamal and Gydan Peninsulas, Beliy Island and islands of the Kara Sea) was not glaciated at the LGM. Sea-level data from marine and salt-marsh deposits show RSL rise at the beginning of the Holocene to a mid-Holocene highstand of 1-5 m at 5-1 ka BP. A similar, but more complex RSL pattern is shown for Eastern Siberia. RSL data from the Laptev Sea shelf show RSL at -40- -45 m and 11-14 ka BP. RSL data from the Lena Delta and Tiksi region have a highstand from 5 to 1 ka BP. The research is supported by RSF project 17-77-10130

Sea Level Rise Drove Enhanced Coastal Erosion following the Last Glacial Maximum, Southern California, U.S.A.

NASA Astrophysics Data System (ADS)

Sharman, G.; Covault, J. A.; Stockli, D. F.; Sickmann, Z.; Malkowski, M. A.; Johnstone, S.

2017-12-01

Seacliff erosion poses a major threat to southern California coastal communities, including the propensity for episodic cliff failure and damage to residential and commercial property. Rising sea level is predicted to accelerate seacliff retreat, yet few constraints exist on how rapid sea level rise influenced coastal erosion rates in pre-modern timescales. Here we look to the geologic record in submarine fans to investigate changes in relative sediment supply from rivers and coastal erosion, the latter including seacliff retreat and bluffland erosion. To understand how sea level rise driven by past global warming impacted coastal erosion rates, we sampled modern rivers of the Peninsular Ranges and latest Pleistocene-Holocene submarine canyon-fan systems in southern California for detrital zircon U-Pb geochronology (1369 analyses from 10 samples). Modern river samples show a systematic north-south change in grain age populations broadly distributed across Cretaceous time (ca. 70-135 Ma) to a predominance of middle Cretaceous grain ages (ca. 95-115 Ma), reflecting variations in the geologic age of units within each river catchment. The Carlsbad and La Jolla submarine canyon-fan systems, deposited during sea level lowstand and highstand, respectively, exhibit detrital zircon age distributions consistent with derivation from upstream rivers, with mixing in the littoral zone. However, a sample from the Oceanside fan, deposited during rapid sea level rise at ca. 13 ka, is dominated by detrital ages that lack a local source in the northern Peninsular Ranges, including latest Cretaceous, late Jurassic, and Proterozoic ages. However, such grain ages are widespread in Paleogene sedimentary rocks that comprise the shelf and coastal area, suggesting increased sediment supply from coastal and shelf erosion. Assuming that the Oceanside sample is representative of sediment production during sea level rise, sediment mixing calculations suggest a one to two orders of magnitude increase in sediment from coastal erosion relative to river-supplied sediment. Our results thus suggest a significant increase in coastal erosion rates following the Last Glacial Maximum, highlighting the risk that future sea level rise poses to coastal communities.

Can uncertainties in sea ice albedo reconcile patterns of data-model discord for the Pliocene and 20th/21st centuries?

USGS Publications Warehouse

Howell, Fergus W.; Haywood, Alan M.; Dolan, Aisling M.; Dowsett, Harry J.; Francis, Jane E; Hill, Daniel J.; Pickering, Steven J.; Pope, James O.; Salzmann, Ulrich; Wade, Bidget S

2014-01-01

General Circulation Model simulations of the mid-Pliocene warm period (mPWP, 3.264 to 3.025 Myr ago) currently underestimate the level of warming that proxy data suggest existed at high latitudes, with discrepancies of up to 11°C for sea surface temperature estimates and 17°C for surface air temperature estimates. Sea ice has a strong influence on high-latitude climates, partly due to the albedo feedback. We present results demonstrating the effects of reductions in minimum sea ice albedo limits in general circulation model simulations of the mPWP. While mean annual surface air temperature increases of up to 6°C are observed in the Arctic, the maximum decrease in model-data discrepancies is just 0.81°C. Mean annual sea surface temperatures increase by up to 2°C, with a maximum model-data discrepancy improvement of 1.31°C. It is also suggested that the simulation of observed 21st century sea ice decline could be influenced by the adjustment of the sea ice albedo parameterization.

Sources and levels of ambient ocean sound near the antarctic peninsula

DOE PAGES

Dziak, Robert P.; Bohnenstiehl, DelWayne R.; Stafford, Kathleen M.; ...

2015-04-14

Arrays of hydrophones were deployed within the Bransfield Strait and Scotia Sea (Antarctic Peninsula region) from 2005 to 2009 to record ambient ocean sound at frequencies of up to 125 and 500 Hz. Icequakes, which are broadband, short duration signals derived from fracturing of large free-floating icebergs, are a prominent feature of the ocean soundscape. Icequake activity peaks during austral summer and is minimum during winter, likely following freeze-thaw cycles. Iceberg grounding and rapid disintegration also releases significant acoustic energy, equivalent to large-scale geophysical events. Overall ambient sound levels can be as much as ~10–20 dB higher in the open,more » deep ocean of the Scotia Sea compared to the relatively shallow Bransfield Strait. Noise levels become lowest during the austral winter, as sea-ice cover suppresses wind and wave noise. Ambient noise levels are highest during austral spring and summer, as surface noise, ice cracking and biological activity intensifies. Vocalizations of blue ( Balaenoptera musculus) and fin ( B. physalus) whales also dominate the long-term spectra records in the 15–28 and 89 Hz bands. Blue whale call energy is a maximum during austral summer-fall in the Drake Passage and Bransfield Strait when ambient noise levels are a maximum and sea-ice cover is a minimum. Fin whale vocalizations were also most common during austral summer-early fall months in both the Bransfield Strait and Scotia Sea. The hydrophone data overall do not show sustained anthropogenic sources (ships and airguns), likely due to low coastal traffic and the typically rough weather and sea conditions of the Southern Ocean.« less

Glacial-eustatic/climatic model for Upper Pennsylvanian marine and nonmarine cyclothems in the Appalachian basin

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

Heckel, P.H.

1992-01-01

Only glacial-eustatic sea-level fluctuations can account for all the characteristics of Upper Pennsylvanian marine cyclothems in the Midcontinent. Because this control is global, it must have affected deposition during this time everywhere. In the Appalachian basin widespread well developed paleosols represent long-term sea-level lowstand. During Conemaugh marine incursions, rising sea level ponded fresh-water influx to form peat swamps that migrated landward ahead of transgression and produced early transgressive coals. Marine highstand deposits commonly are conodont-rich limestones, typically skeletal packstone with glaucony and phosphorite. Regression resulted in progradation of detrital shorelines with local delta cycles, followed eventually by more paleosol formationmore » and local erosional incision that removed older sediments including the marine units in places. Fluvial sands filled many of these channels. During Monongahela deposition when marine incursions no longer entered the Appalachian basin, the climatic fluctuations recognized by Cecil can reasonably be related to sea-level fluctuations nearby, but with shifts in climatic significance of gross lithotopes. Coal swamps would more likely have formed at maximum marine highstand when the nearby sea would have provided both high base level and an abundant source of rainfall. Nonmarine limestones would more likely have formed at maximum lowstand when the sea was most distant and the climate driest. The intervening detrital deposits between the coals and limestones formed under intermediate seasonal rainfall regimes during both marine transgression and regression farther west in the Midcontinent. Conemaugh and Allegheny coals without overlying marine units probably also represent mainly marine highstand elsewhere, and nonmarine limestones of these ages typically are associated with lowstand paleosols.« less

Extreme Storm Surges in the North Sea

NASA Astrophysics Data System (ADS)

Goennert, G.; Buß, Th.; Mueller, O.; Thumm, S.

2009-04-01

Extreme Storm Surges in the North Sea Gabriele Gönnert, Olaf Müller, Thomas Buß and Sigrid Thumm Climate Change will cause a rise of the sea level and probably more frequent and more violent storm surges. This has serious consequences for the safety of people as well as for their values and assets behind the dikes. It is therefore inevitable to first assess how sea level rise and an extreme storm surge event designes. In a second step it is possible to determine the risk for specific locations and develop strategies. The Project XtremRisk - Extreme Storm Surges at the North Sea Coast and in Estuaries. Risk calculation and risk strategies, funded by the German Federal Government will help answering these questions. The „Source-Pathway-Receptor" Concept will be used as a basis for risk analysis and development of new strategies. The Project offers methods to assess the development of extreme events under the conditions of today. Under conditions reflecting the climate change it will be tried to design an extreme event. For these three main points will be considered: a) Analysis and calculation of each factor, which produce a storm surge and its maximum level occurring in the last 100 years. These are: - maximum surge level: surge (due to the wind), - influence of the tide and the interaction between surge and tide, - influence of external surges , b) The hydrodynamics of a storm surge cause nonlinear effects in the interaction of the named factors. These factors and effects will both be taken into account to calculate the magnitude of the extreme storm surge. This step is very complex and need additional examination by numerical models. c) Analysis of the different scenarios to mean sea level rise and to the increase of wind speed due to the climate change. The presentation will introduce methods and show first results of the analysis of extreme events and the mean sea level rise.

Wind extremes in the North Sea basin under climate change: an ensemble study of 12 CMIP5 GCMs

NASA Astrophysics Data System (ADS)

de Winter, R.; Ruessink, G.; Sterl, A.

2012-12-01

Coastal safety may be influenced by climate change, as changes in extreme surge levels and wave extremes may increase the vulnerability of dunes and other coastal defenses. In the North Sea, an area already prone to severe flooding, these high surge levels and waves are generated by severe wind speeds during storm events. As a result of the geometry of the North Sea, not only the maximum wind speed is relevant, but also wind direction. Analyzing changes in a changing climate implies that several uncertainties need to be taken into account. First, there is the uncertainty in climate experiments, which represents the possible development of the emission of greenhouse gases. Second, there is uncertainty between the climate models that are used to analyze the effect of different climate experiments. The third uncertainty is the natural variability of the climate. When this system variability is large, small trends will be difficult to detect. The natural variability results in statistical uncertainty, especially for events with high return values. We addressed the first two types of uncertainties for extreme wind conditions in the North Sea using 12 CMIP5 GCMs. To evaluate the differences between the climate experiments, two climate experiments (rcp4.5 and rcp8.5) from 2050-2100 are compared with historical runs, running from 1950-2000. Rcp4.5 is considered to be a middle climate experiment and rcp8.5 represents high-end climate scenarios. The projections of the 12 GCMs for a given scenario illustrate model uncertainty. We focus on the North Sea basin, because changes in wind conditions could have a large impact on safety of the densely populated North Sea coast, an area that has already a high exposure to flooding. Our results show that, consistent with ERA-Interim results, the annual maximum wind speed in the historical run demonstrates large interannual variability. For the North Sea, the annual maximum wind speed is not projected to change in either rcp4.5 or rcp8.5. In fact, the differences in the 12 GCMs are larger than the difference between the three experiments. Furthermore, our results show that, the variation in direction of annual maximum wind speed is large and this precludes a firm statement on climate-change induced changes in these directions. Nonetheless, most models indicate a decrease in annual maximum wind speed from south-eastern directions and an increase from south-western and western directions. This might be caused by a poleward shift of the storm track. The amount of wind from north-west and north-north-west, wind directions that are responsible for the development of extreme storm surges in the southern part of the North Sea, are not projected to change. However, North Sea coasts that have the longest fetch for western direction, e.g. the German Bight, may encounter more often high storm surge levels and extreme waves when the annual maximum wind will indeed be more often from western direction.

Sea-level projections representing the deeply uncertain contribution of the West Antarctic ice sheet.

PubMed

Bakker, Alexander M R; Wong, Tony E; Ruckert, Kelsey L; Keller, Klaus

2017-06-20

There is a growing awareness that uncertainties surrounding future sea-level projections may be much larger than typically perceived. Recently published projections appear widely divergent and highly sensitive to non-trivial model choices . Moreover, the West Antarctic ice sheet (WAIS) may be much less stable than previous believed, enabling a rapid disintegration. Here, we present a set of probabilistic sea-level projections that approximates the deeply uncertain WAIS contributions. The projections aim to inform robust decisions by clarifying the sensitivity to non-trivial or controversial assumptions. We show that the deeply uncertain WAIS contribution can dominate other uncertainties within decades. These deep uncertainties call for the development of robust adaptive strategies. These decision-making needs, in turn, require mission-oriented basic science, for example about potential signposts and the maximum rate of WAIS-induced sea-level changes.

Display of historical and hypothetical tsunami on the coast of Sakhalin Island

NASA Astrophysics Data System (ADS)

Kostenko, Irina; Zaytsev, Andrey; Kurkin, Andrey; Yalciner, Ahmet

2014-05-01

Tsunami waves achieve the coast of the Sakhalin Island and their sources are located in the Japan Sea, in the Okhotsk Sea, in Kuril Islands region and in the Pacific Ocean. Study of tsunami generation characteristics and its propagation allows studying display of the tsunami on the various parts of the island coast. For this purpose the series of computational experiments of some historical tsunamis was carried out. Their sources located in Japan Sea and Kuril Islands region. The simulation results are compared with the observations. Analysis of all recorded historical tsunami on coast of Sakhalin Island was done. To identify the possible display of the tsunami on the coast of Sakhalin Island the series of computational experiments of hypothetical tsunamis was carried out. Their sources located in the Japan Sea and in the Okhotsk Sea. There were used hydrodynamic sources. There were used different parameters of sources (length, width, height, raising and lowering of sea level), which correspond to earthquakes of various magnitudes. The analysis of the results was carried out. Pictures of the distribution of maximum amplitudes from each tsunami were done. Areas of Okhotsk Sea, Japan Sea and offshore strip of Sakhalin Island with maximum tsunami amplitudes were defined. Graphs of the distribution of maximum tsunami wave heights along the coast of the Sakhalin Island were plotted. Based on shallow-water equation tsunami numerical code NAMI DANCE was used for numerical simulations. This work was supported by ASTARTE project.

Mass-induced sea level variations in the Red Sea from GRACE, steric-corrected altimetry, in situ bottom pressure records, and hydrographic observations

NASA Astrophysics Data System (ADS)

Feng, W.; Lemoine, J.-M.; Zhong, M.; Hsu, H. T.

2014-08-01

An annual amplitude of ∼18 cm mass-induced sea level variations (SLV) in the Red Sea is detected from the Gravity Recovery and Climate Experiment (GRACE) satellites and steric-corrected altimetry from 2003 to 2011. The annual mass variations in the region dominate the mean SLV, and generally reach maximum in late January/early February. The annual steric component of the mean SLV is relatively small (<3 cm) and out of phase of the mass-induced SLV. In situ bottom pressure records at the eastern coast of the Red Sea validate the high mass variability observed by steric-corrected altimetry and GRACE. In addition, the horizontal water mass flux of the Red Sea estimated from GRACE and steric-corrected altimetry is validated by hydrographic observations.

Understanding the Microphysical Properties of Developing Cloud Clusters during TCS-08

DTIC Science & Technology

2010-09-30

Typhoon Mawar (2005) from the western North Pacific to demonstrate considerable differences in both the development of (Fig. 4), and the microphysical...traces of simulated Typhoon Mawar (2005) showing sea-level pressure on the left axis and maximum wind speed on the right axis. There is considerable...differences in both the speed at which Mawar develops and the final minimum sea-level pressure depending on which microphysics (cloud-resolving

Geoethics: IPCC disgraced by violation of observational facts and physical laws in their sea level scenario

NASA Astrophysics Data System (ADS)

Mörner, Nils-Axel

2014-05-01

Sea level may rise due to glacier melting, heat expansion of the oceanic water column, and redistribution of the waster masses - all these factors can be handled as to rates and amplitudes (provided one knows what one is talking about). In key areas over the entire Indian Ocean and in many Pacific Islands there are no traces of and sea level rise over the last 40-50 years. This is also the case for test-areas like Venice and the North Sea coasts. In the Kattegatt Sea one can fix the sea level factor to a maximum rise of 1.0-0.9 mm/year over the last century. The 204 tide gauges selected by NOAA for their global sea level monitoring provide a strong and sharp maximum (of 182 sites) in the range of 0.0-2.0 mm/yr. Satellite altimetry is said to give a rise of 3.2 mm/yr; this, however, is a value achieved after a quite subjective and surely erroneous "correction". The IPCC is talking about exceptionally much higher rates, and even worse are some "boy scouts" desperate try to launce real horror ratios. Physical laws set the frames of the rate and amount of ice melting, and so do records of events in the past (i.e. the geological records). During the Last Ice Age so much ice was accumulated on land, that the sea level dropped by about 120 m. When the process was reversed and ice melted under exceptionally strong climate forcing, sea level rose at a maximum rate of about 10 mm/yr (a meter per century). This can never happen under today's climate conditions. Even with IPCC's hypothetical scenarios, the true sea rise must be far less. When people like Rahmstorf (claiming 1 m or more by 2100) and Hansen (claiming a 4 m rise from 2080 to 2100) give their values, they exceed what is possible according to physical laws and accumulated geological knowledge. The expansion of the oceanic water column may reach amounts of sea level rise in the order of a few centimetres, at the most a decimetre. Old temperature measurements may record a temperature rise over the last 50 years in the order of 0.4o C. The improved ARGO measurements starting 2004 give virtually no change, however. The physically possible amount of expansion decreases, of course, with the decreasing water columns towards the coasts, and at the coasts it is zero (±0.0 mm). The redistribution of water masses in response to the Earth's rotation, surface current beat, wind stress, air pressure, etc. is an important factor. It gives local to regional changes, cancelled out on the global scale, however. From a geoethical point of view, it is of course quite blameworthy that IPCC excels in spreading these horror scenarios of a rapid, even accelerating, sea level rise. Besides, modern understanding of the planetary-solar-terrestrial interaction shows that we are now on our way into grand solar minimum with severely colder climate - that is just the opposite to IPCC's talk about an accelerating warming. In science we should debate - but we should not dictate (as IPCC insist upon), and it is here the perspectives of geoethics comes into the picture.

Mass-induced sea level variations in the Red Sea from steric-corrected altimetry, GRACE, in-situ bottom pressure records, and hydrographic observations

NASA Astrophysics Data System (ADS)

Feng, Wei; Lemoine, Jean-Michel; Zhong, Min; Xu, Houze

2014-05-01

An annual amplitude of ~18 cm mass-induced sea level variations (SLV) in the Red Sea is detected from steric-corrected altimetry and the Gravity Recovery and Climate Experiment (GRACE) satellites from 2003 to 2011, which dominates the mean sea level in the region. Seawater mass variations here generally reach maximum in late January/early February. The steric component of SLV calculated from oceanographic temperature and salinity data is relatively small and peaks about seven months later than mass variations. The phase difference between the steric SLV and the mass-induced SLV indicates that when the Red Sea gains the mass from inflow water in winter, the steric SLV fall, and vice versa in summer. In-situ bottom pressure records in the eastern coast of the Red Sea validate the high mass variability observed by steric-corrected altimetry and GRACE. Furthermore, we compare the horizontal water mass flux in the Red Sea from steric-corrected altimetry and GRACE with that estimated from hydrographic observations.

A Late Pleistocene sea level stack

NASA Astrophysics Data System (ADS)

Spratt, R. M.; Lisiecki, L. E.

2015-08-01

Late Pleistocene sea level has been reconstructed from ocean sediment core data using a wide variety of proxies and models. However, the accuracy of individual reconstructions is limited by measurement error, local variations in salinity and temperature, and assumptions particular to each technique. Here we present a sea level stack (average) which increases the signal-to-noise ratio of individual reconstructions. Specifically, we perform principal component analysis (PCA) on seven records from 0-430 ka and five records from 0-798 ka. The first principal component, which we use as the stack, describes ~80 % of the variance in the data and is similar using either five or seven records. After scaling the stack based on Holocene and Last Glacial Maximum (LGM) sea level estimates, the stack agrees to within 5 m with isostatically adjusted coral sea level estimates for Marine Isotope Stages 5e and 11 (125 and 400 ka, respectively). When we compare the sea level stack with the δ18O of benthic foraminifera, we find that sea level change accounts for about ~40 % of the total orbital-band variance in benthic δ18O, compared to a 65 % contribution during the LGM-to-Holocene transition. Additionally, the second and third principal components of our analyses reflect differences between proxy records associated with spatial variations in the δ18O of seawater.

Athletes at altitude

PubMed Central

Pugh, L. G. C. E.

1967-01-01

1. Six international middle-distance runners were investigated during 4 weeks in England and during a similar period in Mexico City (2270 m (7450 ft.)) 2. In 3-mile (4828 m) time trials at 2270 m the increase in time taken by four subjects compared with sea level was 8·5% on the 4th day and 5·7% on the 29th day. There was thus a gain of 2·8% or 20 sec in time associated with acclimatization. 3. In 1-mile (1609 m) time trials the times were increased by 3·6% in the first week at altitude and by 1·5% in the 4th week. The improvement amounted to 2·1%, or 4·9 sec. 4. In 5 min maximum exercise on the ergometer maximum O2 intake for six subjects at altitude was reduced by 14·6% on the 2nd day and 9·5% on the 27th. Only one subject showed no change in maximum oxygen intake (V̇O2, max) with time spent at altitude. 5. Although V̇O2, max was persistently reduced at altitude work rates finally exceeded sea-level values, owing to increased over-all efficiency. 6. Forty-minute recovery O2 intakes after 5 min maximum exercise averaged 17·35 l. at sea level and 17·53 l. at altitude. Mean values from 40th to 50th min were within ± 7% of pre-exercise values. 7. Serial tests at increasing loads yielded a straight-line relation between O2 intake and work rate over a wide range of work rates at sea level and at altitude. Heart rate and ventilation for given work intensity were maximal in the first 2-10 days at altitude and thereafter declined. 8. Capillary HbO2 saturation fell from 93% at rest to 87% in maximum exercise. The corresponding alveolar gas tensions were PA, O2 89 mm Hg, PA, CO2 24 mm Hg. About half the total unsaturation in maximum exercise was explained by the Bohr effect. 9. In six of eight pairs of determinations V̇O2, max measured on the ergometer was within ± 0·15 l./min of V̇O2, max measured on the running track. Nevertheless, it was not possible to predict running performance from ergometer measurements. PMID:6058997

Sea-level and environmental changes since the last interglacial in the Gulf of Carpentaria, Australia: an overview

USGS Publications Warehouse

Chivas, Allan R.; Garcı́a, Adriana; van der Kaars, Sander; Couapel, Martine; Holt, Sabine; Reeves, Jessica M.; Wheeler, David J.; Switzer, Adam D.; Murray-Wallace, Colin V.; Banerjee, Debabrata; Price, David M.; Wang, Sue X.; Pearson, Grant; Edgar, N. Terry; Beaufort, Luc; de Deckker, Patrick; Lawson, Ewan; Cecil, C. Blaine

2001-01-01

The Gulf of Carpentaria is an epicontinental sea (maximum depth 70 m) between Australia and New Guinea, bordered to the east by Torres Strait (currently 12 m deep) and to the west by the Arafura Sill (53 m below present sea level). Throughout the Quaternary, during times of low sea-level, the Gulf was separated from the open waters of the Indian and Pacific Oceans, forming Lake Carpentaria, an isolation basin, perched above contemporaneous sea-level with outlet channels to the Arafura Sea. A preliminary interpretation is presented of the palaeoenvironments recorded in six sediment cores collected by the IMAGES program in the Gulf of Carpentaria. The longest core (approx. 15 m) spans the past 130 ka and includes a record of sea-level/lake-level changes, with particular complexity between 80 and 40 ka when sea-level repeatedly breached and withdrew from Gulf/Lake Carpentaria. Evidence from biotic remains (foraminifers, ostracods, pollen), sedimentology and geochemistry clearly identifies a final marine transgression at about 9.7 ka (radiocarbon years). Before this transgression, Lake Carpentaria was surrounded by grassland, was near full, and may have had a surface area approaching 600 km×300 km and a depth of about 15 m. The earlier rise in sea-level which accompanied the Marine Isotopic Stage 6/5 transgression at about 130 ka is constrained by sedimentological and biotic evidence and dated by optical- and thermoluminescence and amino acid racemisation methods.

Birth of the modern Chesapeake Bay estuary between 7.4 and 8.2 ka and implications for global sea-level rise

NASA Astrophysics Data System (ADS)

Bratton, John F.; Colman, Steven M.; Thieler, E. Robert; Seal, Robert R.

2002-12-01

Two major pulses of sea-level rise are thought to have taken place since the last glacial maximum — meltwater pulses (mwp) 1A (12 cal ka) and 1B (9.5 cal ka). Between mwp 1B and about 6 cal ka, many of the complex coastal ecosystems which ring the world's oceans began to form. Here we report data for rhenium, carbon isotopes, total organic carbon, and fossil oysters from Chesapeake Bay which span the transition from fresh to brackish water conditions in the bay in the mid-Holocene. These data constrain sea-level change and resulting environmental change in the bay. They indicate that the transition was rapid, and that it was produced by (1) a third pulse of rapid eustatic sea-level rise, or (2) a geometry of the prehistoric Chesapeake Bay basin which predisposed it to a nonlinear response to a steadily rising sea level. Similar nonlinear changes in vulnerable coastal environments are likely to take place in the future due to polar warming, regardless of the timing or rate of sea-level rise.

Birth of the modern Chesapeake Bay estuary between 7.4 and 8.2 ka and implications for global sea-level rise

USGS Publications Warehouse

Bratton, John F.; Colman, Steven M.; Thieler, E. Robert; Seal, Robert R.

2003-01-01

Two major pulses of sea-level rise are thought to have taken place since the last glacial maximum — meltwater pulses (mwp) 1A (12 cal ka) and 1B (9.5 cal ka). Between mwp 1B and about 6 cal ka, many of the complex coastal ecosystems which ring the world’s oceans began to form. Here we report data for rhenium, carbon isotopes, total organic carbon, and fossil oysters from Chesapeake Bay which span the transition from fresh to brackish water conditions in the bay in the mid-Holocene. These data constrain sea-level change and resulting environmental change in the bay. They indicate that the transition was rapid, and that it was produced by (1) a third pulse of rapid eustatic sea-level rise, or (2) a geometry of the prehistoric Chesapeake Bay basin which predisposed it to a nonlinear response to a steadily rising sea level. Similar nonlinear changes in vulnerable coastal environments are likely to take place in the future due to polar warming, regardless of the timing or rate of sea-level rise.

Late Quaternary variations in relative sea level due to glacial cycle polar wander

USGS Publications Warehouse

Bills, B.G.; James, T.S.

1996-01-01

Growth and decay of continental ice sheets can excite significant motion of the Earth's rotation pole and cause a complex spatio-temporal pattern of changes in relative sea level. These two effects have generally been considered separately, but may interact in important ways. In particular, a simple model of the melting of the Laurentide ice sheet causes a uniform eustatic sea level rise of 55 m, and also induces a motion of the rotation pole by 0.1 to 1 degree, depending on viscosity structure in the mantle. This motion produces a secular pole tide, which is a spherical harmonic degree 2, order 1 component of the relative sea level pattern, with peak-to-peak amplitude of 20 to 40 m. The maximum effect is along the great circle passing through the path of the pole and at latitudes of ??45??. This secular pole tide has been ignored in most previous attempts to estimate ice sheet loading history and mantle viscosity from global patterns of relative sea level change. It has a large influence along the East coast of North America and the West coast of South America, and significantly contributes to present day rates of relative sea level change.

Sea-level records from the U.S. mid-Atlantic constrain Laurentide Ice Sheet extent during Marine Isotope Stage 3

PubMed Central

Pico, T; Creveling, J. R.; Mitrovica, J. X.

2017-01-01

The U.S. mid-Atlantic sea-level record is sensitive to the history of the Laurentide Ice Sheet as the coastline lies along the ice sheet's peripheral bulge. However, paleo sea-level markers on the present-day shoreline of Virginia and North Carolina dated to Marine Isotope Stage (MIS) 3, from 50 to 35 ka, are surprisingly high for this glacial interval, and remain unexplained by previous models of ice age adjustment or other local (for example, tectonic) effects. Here, we reconcile this sea-level record using a revised model of glacial isostatic adjustment characterized by a peak global mean sea level during MIS 3 of approximately −40 m, and far less ice volume within the eastern sector of the Laurentide Ice Sheet than traditional reconstructions for this interval. We conclude that the Laurentide Ice Sheet experienced a phase of very rapid growth in the 15 kyr leading into the Last Glacial Maximum, thus highlighting the potential of mid-field sea-level records to constrain areal extent of ice cover during glacial intervals with sparse geological observables. PMID:28555637

Barrier island response to an elevated sea-level anomaly: Onslow Beach, North Carolina, USA

NASA Astrophysics Data System (ADS)

Theuerkauf, E. J.; Rodriguez, A. B.; Fegley, S. R.; Luettich, R.

2012-12-01

Variations in sea level over time scales ranging from hours to millennia influence coastal processes and evolution. At annual time scales, elevated sea-level anomalies produce coastal flooding and promote beach erosion. This study examines the coastal response of Onslow Beach, North Carolina to the summer 2009 East Coast sea-level anomaly. Onslow Beach is a 12-km-long wave-dominated barrier island with highly variable along-barrier morphology. The transgressive southern portion of the island is characterized by a narrow beach, low dunes, and multiple washover fans, while the regressive northern portion is characterized by a wide beach and continuous tall dunes. Hourly tide gauge data from adjacent NOAA stations (Beaufort and Wrightsville Beach) are used to determine the timing and extent of elevated water levels. The seasonal and longer term trends (relative sea level rise) are removed from both of the water level series and the sea-level anomaly is represented by a large residual between the observed and predicted water levels. Beach response is quantified using terrestrial laser scanning for morphology and from geoprobe cores to determine the maximum depth of erosion (MDOE). The mean high water (MHW) shoreline and dune toe are digitized from digital elevation models derived from the laser scans and analyzed using the Digital Shoreline Analysis System (DSAS). Landward (negative) movement of these contacts indicates erosion. Wave data collected from an Acoustic Wave and Current Meter (AWAC) located offshore of the southern end of Onslow Beach is used to characterize the wave regime throughout the study. Water level is elevated in the tide gauge data from June 2009 to March 2010. This sea-level anomaly corresponds with an increase in the maximum depth of erosion between 2009 and 2010. Landward movement of the MHW shoreline and the dunetoe increased during the period between September 2009 and May 2010 indicating an increase in beach erosion during the sea-level anomaly. No significant increase in wave height was observed during this period, suggesting that the increase in beach erosion resulted from the sea-level anomaly. The sites that were strongly impacted by the sea-level anomaly did not fully recover from the beach erosion and consequently experienced large amounts of erosion in response to Hurricane Irene in 2011. These results suggest that long duration (weeks to months) high water levels cause changes to the beach similar to those generally thought to occur only during large storms. Dune erosion from higher sea levels weakens a beaches defense to storms, leading to increased beach erosion and overwash if a storm occurs before the beach can recover. It is likely that similar high water events will increase in duration and magnitude with future climate change, leading to increased "fair-weather" beach erosion and priming the system for devastating hurricane impacts.

Extreme Statistics of Storm Surges in the Baltic Sea

NASA Astrophysics Data System (ADS)

Kulikov, E. A.; Medvedev, I. P.

2017-11-01

Statistical analysis of the extreme values of the Baltic Sea level has been performed for a series of observations for 15-125 years at 13 tide gauge stations. It is shown that the empirical relation between value of extreme sea level rises or ebbs (caused by storm events) and its return period in the Baltic Sea can be well approximated by the Gumbel probability distribution. The maximum values of extreme floods/ebbs of the 100-year recurrence were observed in the Gulf of Finland and the Gulf of Riga. The two longest data series, observed in Stockholm and Vyborg over 125 years, have shown a significant deviation from the Gumbel distribution for the rarest events. Statistical analysis of the hourly sea level data series reveals some asymmetry in the variability of the Baltic Sea level. The probability of rises proved higher than that of ebbs. As for the magnitude of the 100-year recurrence surge, it considerably exceeded the magnitude of ebbs almost everywhere. This asymmetry effect can be attributed to the influence of low atmospheric pressure during storms. A statistical study of extreme values has also been applied to sea level series for Narva over the period of 1994-2000, which were simulated by the ROMS numerical model. Comparisons of the "simulated" and "observed" extreme sea level distributions show that the model reproduces quite satisfactorily extreme floods of "moderate" magnitude; however, it underestimates sea level changes for the most powerful storm surges.

LLWBCS changes through surface mesoscale activity and baroclinic tides in the Solomon Sea

NASA Astrophysics Data System (ADS)

Gourdeau, L.; Djath, B.; Ganachaud, A. S.; Tchilibou, M. L.; Verron, J. A.; Jouanno, J.

2016-02-01

In the south west Pacific, the Solomon Sea is on the pathway of the Low Latitudes Western Boundary Currents that connect the subtropics to the equator. Changes in their strengths, or in their water mass properties may have implication for ENSO and its low frequency modulation. During their transit in the Solomon Sea, the salinity maximum at thermocline level, characteristic of the South Pacific Tropical Waters (SPTW), is largely eroded. Different mechanisms could explain such salt erosion whose current/bathymetry interaction, internal tides, eddy activity. The Solomon Sea is an area of high level of eddy kinetic energy (EKE), especially in the surface layers, and its complex bathymetry is favourable for generation and dissipation of internal tides. Based on high resolution modelling, glider, and altimetric data mesoscale eddies observed at the surface are analysed in their 4D aspects. Their role on water mass transformation is explored. These eddies may affect the surface layers (σ<23.3) and the upper thermocline waters (23.3< σ <24.3), but they cannot explained the erosion of the salinity maximum below. Simulations with and without explicit tides provide a description of baroclinic tides in the Solomon Sea. Their role on water mixing is evaluated, especially for the SPTW.

Last 900 ka river longprofile changes controlled by Yoro fault activity and glacial sea-level changes, Nobi plain, central Japan

NASA Astrophysics Data System (ADS)

Sugai, T.; Sato, T.

2015-12-01

This paper compared grain size, thickness, and lithological character of ten fluvial gravel layers formed during the glacial sea-level lowstands intervening inner bay mud layers deposited during the interglacial marine transgressional periods since the last 900 ka by integrated analyses of sediment cores including 600 m deep onein the Nobi plain, central Japan. Linkages between river long profile changes and sea-level and climate changes will be discussed. The Nobi basin is one of the representative delta type alluvial lowlands in Japan dominated by longitudinal drainage system named Kiso river system flowing southward from central Japan Alps with abundant water and sediment discharges. The basin bounded by the Yoro fault on the west has been tilted westward by the repetitive faulting activity. The basin stratigraphy and its stacking patterns suggest uniform and rapid subsidence and tilting rates of the basin with the maximum value of 1 mm yr-1 and 10-4 kyr-1 respectively produced by the Yoro fault activity under the W-E compressional regional stress field during the middle and late Quaternary periods. Tephrochronological, paleomagnetic, geochemical, and diatom analyses enabled to identify ten times repeated marine transgression-regression sequences correlated with full glacial-interglacial sea-level changes during the last 900 ka. All of the ten sequence boundaries were characterized by fluvial gravel layers were formed by the Kiso river system. The mean maximum gravel size is proportional to the magnitude of sea level lowering inferred from MIS curve, i.e. gravels deposited in MIS 12 and 16 are the largest, and those in MIS 14 and 8 are the smallest since MIS 16. This suggests that the longitudinal profile of the Kiso river system has been adjusting to the sea level changes and that the steeper longitudinal profile formed in the lower sea level periods can transport larger gravels to the drilling sites. In fact the present river bed gravel size is in proportion with the tractive force and mainly controlled by slope of the rive long-profile.

Dynamics of the last glacial maximum Antarctic ice-sheet and its response to ocean forcing

PubMed Central

Golledge, Nicholas R.; Fogwill, Christopher J.; Mackintosh, Andrew N.; Buckley, Kevin M.

2012-01-01

Retreat of the Last Glacial Maximum (LGM) Antarctic ice sheet is thought to have been initiated by changes in ocean heat and eustatic sea level propagated from the Northern Hemisphere (NH) as northern ice sheets melted under rising atmospheric temperatures. The extent to which spatial variability in ice dynamics may have modulated the resultant pattern and timing of decay of the Antarctic ice sheet has so far received little attention, however, despite the growing recognition that dynamic effects account for a sizeable proportion of mass-balance changes observed in modern ice sheets. Here we use a 5-km resolution whole-continent numerical ice-sheet model to assess whether differences in the mechanisms governing ice sheet flow could account for discrepancies between geochronological studies in different parts of the continent. We first simulate the geometry and flow characteristics of an equilibrium LGM ice sheet, using pan-Antarctic terrestrial and marine geological data for constraint, then perturb the system with sea level and ocean heat flux increases to investigate ice-sheet vulnerability. Our results identify that fast-flowing glaciers in the eastern Weddell Sea, the Amundsen Sea, central Ross Sea, and in the Amery Trough respond most rapidly to ocean forcings, in agreement with empirical data. Most significantly, we find that although ocean warming and sea-level rise bring about mainly localized glacier acceleration, concomitant drawdown of ice from neighboring areas leads to widespread thinning of entire glacier catchments—a discovery that has important ramifications for the dynamic changes presently being observed in modern ice sheets. PMID:22988078

Dynamics of the last glacial maximum Antarctic ice-sheet and its response to ocean forcing.

PubMed

Golledge, Nicholas R; Fogwill, Christopher J; Mackintosh, Andrew N; Buckley, Kevin M

2012-10-02

Retreat of the Last Glacial Maximum (LGM) Antarctic ice sheet is thought to have been initiated by changes in ocean heat and eustatic sea level propagated from the Northern Hemisphere (NH) as northern ice sheets melted under rising atmospheric temperatures. The extent to which spatial variability in ice dynamics may have modulated the resultant pattern and timing of decay of the Antarctic ice sheet has so far received little attention, however, despite the growing recognition that dynamic effects account for a sizeable proportion of mass-balance changes observed in modern ice sheets. Here we use a 5-km resolution whole-continent numerical ice-sheet model to assess whether differences in the mechanisms governing ice sheet flow could account for discrepancies between geochronological studies in different parts of the continent. We first simulate the geometry and flow characteristics of an equilibrium LGM ice sheet, using pan-Antarctic terrestrial and marine geological data for constraint, then perturb the system with sea level and ocean heat flux increases to investigate ice-sheet vulnerability. Our results identify that fast-flowing glaciers in the eastern Weddell Sea, the Amundsen Sea, central Ross Sea, and in the Amery Trough respond most rapidly to ocean forcings, in agreement with empirical data. Most significantly, we find that although ocean warming and sea-level rise bring about mainly localized glacier acceleration, concomitant drawdown of ice from neighboring areas leads to widespread thinning of entire glacier catchments-a discovery that has important ramifications for the dynamic changes presently being observed in modern ice sheets.

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.

Mercury distribution in ancient and modern sediment of northeastern Bering Sea

USGS Publications Warehouse

Nelson, C.H.; Pierce, D.E.; Leong, K.W.; Wang, F.F.H.

1975-01-01

Reconnaissance sampling of surface and subsurface sediment to a maximum depth of 80 m below the sea floor shows that typical values of 0.03 p.p.m. and anomalies of 0.2-1.3 p.p.m. mercury have been present in northeastern Bering Sea since Early Pliocene time. Values are highest in modern beach (maximum 1.3 and mean 0.22 p.p.m. Hg) and nearshore subsurface gravels (maximum 0.6 and mean 0.06 p.p.m. Hg) along the highly mineralized Seward Peninsula and in clayey silt rich in organic matter (maximum 0.16 and mean 0.10 p.p.m. Hg) throughout the region. Although gold mining may be partly responsible for high mercury levels in the modern beach near Nome, Alaska (maximum 0.45 p.p.m.), equally high or greater concentrations of mercury occur in buried Pleistocene sediments immediately offshore (maximum 0.6 p.p.m.) and in modern unpolluted beach sediments at Bluff (maximum 1.3 p.p.m.); this suggests that the contamination effects of mining may be no greater than natural concentration processes in the Seward Peninsula region. The mercury content of offshore surface sediment, even adjacent to mercury-rich beaches, corresponds to that of unpolluted marine and fresh-water sediment elsewhere. The normal values that prevail offshore may be attributable to entrapment of mercury-bearing heavy minerals on beaches near sources and/or dilution effects of offshore sedimentation. The few minor anomalies offshore occur in glacial drift derived from mercury source regions of Chukotka (Siberia) and Seward Peninsula; Pleistocene shoreline processes have reworked the drift to concentrate the heavy metals. The distribution pattern of mercury indicates that particulate mercury-bearing minerals have not been widely dispersed from onland deposits in quantities sufficient to increase mercury levels above normal in offshore sediments of Bering Sea; however, it shows that natural sedimentary processes can concentrate this mercury in beaches of the coastal zone where there already is concern because of potential pollution from man's activities.

Late Cretaceous to Miocene sea-level estimates from the New Jersey and Delaware coastal plain coreholes: An error analysis

USGS Publications Warehouse

Kominz, M.A.; Browning, J.V.; Miller, K.G.; Sugarman, P.J.; Mizintseva, S.; Scotese, C.R.

2008-01-01

Sea level has been estimated for the last 108 million years through backstripping of corehole data from the New Jersey and Delaware Coastal Plains. Inherent errors due to this method of calculating sea level are discussed, including uncertainties in ages, depth of deposition and the model used for tectonic subsidence. Problems arising from the two-dimensional aspects of subsidence and response to sediment loads are also addressed. The rates and magnitudes of sea-level change are consistent with at least ephemeral ice sheets throughout the studied interval. Million-year sea-level cycles are, for the most part, consistent within the study area suggesting that they may be eustatic in origin. This conclusion is corroborated by correlation between sequence boundaries and unconformities in New Zealand. The resulting long-term curve suggests that sea level ranged from about 75-110 m in the Late Cretaceous, reached a maximum of about 150 m in the Early Eocene and fell to zero in the Miocene. The Late Cretaceous long-term (107 years) magnitude is about 100-150 m less than sea level predicted from ocean volume. This discrepancy can be reconciled by assuming that dynamic topography in New Jersey was driven by North America overriding the subducted Farallon plate. However, geodynamic models of this effect do not resolve the problem in that they require Eocene sea level to be significantly higher in the New Jersey region than the global average. ?? 2008 The Authors. Journal compilation ?? 2008 Blackwell Publishing.

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.

Levels of total mercury in predatory fish sold in Canada in 2005.

PubMed

Dabeka, R W; McKenzie, A D; Forsyth, D S

2011-06-01

Total mercury was analysed in 188 samples of predatory fish purchased at the retail level in Canada in 2005. The average concentrations (ng g(-1), range) were: sea bass 329 (38-1367), red snapper 148 (36-431), orange roughy 543 (279-974), fresh water trout 55 (20-430), grouper 360 (8-1060), black cod 284 (71-651), Arctic char 37 (28-54), king fish 440 (42-923), tilefish 601 (79-1164) and marlin 854 (125-2346). The Canadian standard for maximum total mercury allowed in the edible portions of fish sold at the retail level is 1000 ng g(-1) for shark, swordfish, marlin, orange roughy, escolar and both fresh and frozen tuna. The standard is 500 ng g(-1) for all other types of fish. In this study, despite the small number of samples of each species, the 1000 ng g(-1) maximum was exceeded in five samples of marlin (28%). The 500 ng g(-1) maximum was exceeded by six samples of sea bass (20%), four of tilefish (50%), five of grouper (24%), six of king fish (40%) and one of black cod (13%).

Spatial variations of sea level along the coast of Thailand: Impacts of extreme land subsidence, earthquakes and the seasonal monsoon

NASA Astrophysics Data System (ADS)

Saramul, Suriyan; Ezer, Tal

2014-11-01

The study addresses two important issues associated with sea level along the coasts of Thailand: first, the fast sea level rise and its spatial variation, and second, the monsoonal-driven seasonal variations in sea level. Tide gauge data that are more extensive than in past studies were obtained from several different local and global sources, and relative sea level rise (RSLR) rates were obtained from two different methods, linear regressions and non-linear Empirical Mode Decomposition/Hilbert-Huang Transform (EMD/HHT) analysis. The results show extremely large spatial variations in RSLR, with rates varying from ~ 1 mm y-1 to ~ 20 mm y-1; the maximum RSLR is found in the upper Gulf of Thailand (GOT) near Bangkok, where local land subsidence due to groundwater extraction dominates the trend. Furthermore, there are indications that RSLR rates increased significantly in all locations after the 2004 Sumatra-Andaman Earthquake and the Indian Ocean tsunami that followed, so that recent RSLR rates seem to have less spatial differences than in the past, but with high rates of ~ 20-30 mm y-1 almost everywhere. The seasonal sea level cycle was found to be very different between stations in the GOT, which have minimum sea level in June-July, and stations in the Andaman Sea, which have minimum sea level in February. The seasonal sea-level variations in the GOT are driven mostly by large-scale wind-driven set-up/set-down processes associated with the seasonal monsoon and have amplitudes about ten times larger than either typical steric changes at those latitudes or astronomical annual tides.

Last Deglacial Sea Level: A Curated Database of Indicators of Past Sea Levels from Biological and Geomorphological Archives

NASA Astrophysics Data System (ADS)

Hibbert, F. D.; Williams, F. H.; Fallon, S.; Rohling, E. J.

2017-12-01

The last deglacial was an interval of rapid climate and sea-level change, including the collapse of large continental ice sheets. This database collates carefully assessed sea-level data from peer-reviewed sources for the interval 0 to 25 thousand years ago (ka), from the last glacial maximum to the present interglacial conditions. In addition to facilitating site-specific reconstructions of past sea levels, the database provides a suite of data beyond the range of modern/instrumental variability that may help hone future sea-level projections. The database is global in scope, internally consistent, and contains U-series and radiocarbon dated indicators from both biological and geomorpohological archives. We focus on far-field data (i.e., away from the sites of the former continental ice sheets), but some key intermediate (i.e., from the Caribbean) data are also included. All primary fields (i.e., sample location, elevation, age and context) possess quantified uncertainties, which - in conjunction with available metadata - allows the reconstructed sea levels to be interpreted within both their uncertainties and geological context. Consistent treatment of each of the individual records in the database, and incorporation of fully expressed uncertainties, allows datasets to be easily compared. The compilation contains 145 studies from 40 locations (>2,000 data points) and includes all raw information and metadata.

Levels of total mercury in marine organisms from Adriatic Sea, Italy.

PubMed

Perugini, Monia; Visciano, Pierina; Manera, Maurizio; Zaccaroni, Annalisa; Olivieri, Vincenzo; Amorena, Michele

2009-08-01

The presence of total mercury in fish, crustacean and cephalopod from Adriatic Sea, was investigated. The highest concentrations were observed in decreasing order in: Norway lobster (0.97 +/- 0.24 mg/kg; mean +/- SE), European hake (0.59 +/- 0.14 mg/kg), red mullet (0.48 +/- 0.09 mg/kg), blue whiting (0.38 +/- 0.09 mg/kg), Atlantic mackerel (0.36 +/- 0.08 mg/kg) and European flying squid (0.25 +/- 0.03 mg/kg). A significant difference (p < 0.01) was found between the levels of total mercury in Norway lobster and those detected in all other species. The 25% of all samples exceeded the maximum limit fixed by Commission Regulation (EC) No 1881/2006. The results show that fish and fishery products can exceed the maximum levels and stress the need of more information for consumers in particular for people that eat large amount of fish.

Holocene sea-level change and Antarctic melting history derived from geological observations and geophysical modeling along the Shimokita Peninsula, northern Japan

NASA Astrophysics Data System (ADS)

Yokoyama, Yusuke; Okuno, Jun'ichi; Miyairi, Yosuke; Obrochta, Stephen; Demboya, Nobuhiro; Makino, Yoshinori; Kawahata, Hodaka

2012-07-01

A Mid to Late Holocene sea-level record based on combined geomorphological, geological and micropaleontological observations was obtained from well-developed wave cut benches subaerially exposed along the Shimokita Peninsula, northern Japan. Results indicate that the benches were formed during mid to late Holocene sea-level transgressions, reaching a maximum highstand level of 2 m above present at about 4,000 years ago. This timing corresponds to an abrupt, order of magnitude decrease in sedimentation rate as recorded in a core recovered from proximal Mutsu Bay. In addition, glacio-hydro-isostatic adjustment due to crustal deformation in response to postglacial sea-level rise was modeled, and results are consistent with the reconstructed local 2 m highstand. Given that meltwater contributions from the major North American and European ice sheets had largely ceased by 7,000 years ago, these independent lines of evidence, taken together, indicate that melting of the Antarctic ice sheet ended by 4,000 years ago.

Determination of sound types and source levels of airborne vocalizations by California sea lions, Zalophus californianus, in rehabilitation at the Marine Mammal Center in Sausalito, California

NASA Astrophysics Data System (ADS)

Schwalm, Afton Leigh

California sea lions (Zalophus californianus) are a highly popular and easily recognized marine mammal in zoos, aquariums, circuses, and often seen by ocean visitors. They are highly vocal and gregarious on land. Surprisingly, little research has been performed on the vocalization types, source levels, acoustic properties, and functions of airborne sounds used by California sea lions. This research on airborne vocalizations of California sea lions will advance the understanding of this aspect of California sea lions communication, as well as examine the relationship between health condition and acoustic behavior. Using a PhillipsRTM digital recorder with attached microphone and a calibrated RadioShackRTM sound pressure level meter, acoustical data were recorded opportunistically on California sea lions during rehabilitation at The Marine Mammal Center in Sausalito, CA. Vocalizations were analyzed using frequency, time, and amplitude variables with Raven Pro: Interactive Sound Analysis Software Version 1.4 (The Cornell Lab of Ornithology, Ithaca, NY). Five frequency, three time, and four amplitude variables were analyzed for each vocalization. Differences in frequency, time, and amplitude variables were not significant by sex. The older California sea lion group produced vocalizations that were significantly lower in four frequency variables, significantly longer in two time variables, significantly higher in calibrated maximum and minimum amplitude variables, and significantly lower in frequency at maximum and minimum amplitude compared with pups. Six call types were identified: bark, goat, growl/grumble, bark/grumble, bark/growl, and grumble/moan. The growl/grumble call was higher in dominant beginning, ending, and minimum frequency, as well as in the frequency at maximum amplitude compared with the bark, goat, bark/grumble calls in the first versus last vocalization sample. The goat call was significantly higher in first harmonic interval than any other call type in the all vocalizations sample. The "fate" of a sea lion was categorized as: released, placed at another facility, remained at TMMC, euthanized, or died. To determine if acoustic features could be used to assess the recovery of a pup, the acoustic features of a pup's first recorded vocalization were compared with the frequency, time, and amplitude of the last vocalization recorded (i.e., before it was released or placed at another facility). In addition, all first vocalizations were pooled and all last vocalizations were pooled for acoustic analysis, regardless of their fate. Released pups had shorter duration calls, a greater first harmonic interval, and a higher dominant maximum frequency than either pups that died or pups remaining at TMMC. Released pups had a higher frequency at maximum and minimum amplitude compared to dead and remaining pups. Pups that died had significantly lower dominant ending frequency and a lower dominant minimum frequency than released or remaining pups. These results were supported by other studies on different species of otariids, phocids, and cetaceans. The preliminary analyses presented in this thesis holds promise that with additional data acoustic features of California sea lion airborne vocalizations could indicate sex, age, and possibly health condition or the potential for release.

Interhemispheric ice-sheet synchronicity during the last glacial maximum

USGS Publications Warehouse

Weber, Michael E.; Clark, Peter U.; Ricken, Werner; Mitrovica, Jerry X.; Hostetler, Steven W.; Kuhn, Gerhard

2011-01-01

The timing of the last maximum extent of the Antarctic ice sheets relative to those in the Northern Hemisphere remains poorly understood. We develop a chronology for the Weddell Sea sector of the East Antarctic Ice Sheet that, combined with ages from other Antarctic ice-sheet sectors, indicates that the advance to and retreat from their maximum extent was within dating uncertainties synchronous with most sectors of Northern Hemisphere ice sheets. Surface climate forcing of Antarctic mass balance would probably cause an opposite response, whereby a warming climate would increase accumulation but not surface melting. Our new data support teleconnections involving sea-level forcing from Northern Hemisphere ice sheets and changes in North Atlantic deep-water formation and attendant heat flux to Antarctic grounding lines to synchronize the hemispheric ice sheets.

Interhemispheric ice-sheet synchronicity during the Last Glacial Maximum.

PubMed

Weber, Michael E; Clark, Peter U; Ricken, Werner; Mitrovica, Jerry X; Hostetler, Steven W; Kuhn, Gerhard

2011-12-02

The timing of the last maximum extent of the Antarctic ice sheets relative to those in the Northern Hemisphere remains poorly understood. We develop a chronology for the Weddell Sea sector of the East Antarctic Ice Sheet that, combined with ages from other Antarctic ice-sheet sectors, indicates that the advance to and retreat from their maximum extent was within dating uncertainties synchronous with most sectors of Northern Hemisphere ice sheets. Surface climate forcing of Antarctic mass balance would probably cause an opposite response, whereby a warming climate would increase accumulation but not surface melting. Our new data support teleconnections involving sea-level forcing from Northern Hemisphere ice sheets and changes in North Atlantic deep-water formation and attendant heat flux to Antarctic grounding lines to synchronize the hemispheric ice sheets.

Daily sea level prediction at Chiayi coast, Taiwan using extreme learning machine and relevance vector machine

NASA Astrophysics Data System (ADS)

Imani, Moslem; Kao, Huan-Chin; Lan, Wen-Hau; Kuo, Chung-Yen

2018-02-01

The analysis and the prediction of sea level fluctuations are core requirements of marine meteorology and operational oceanography. Estimates of sea level with hours-to-days warning times are especially important for low-lying regions and coastal zone management. The primary purpose of this study is to examine the applicability and capability of extreme learning machine (ELM) and relevance vector machine (RVM) models for predicting sea level variations and compare their performances with powerful machine learning methods, namely, support vector machine (SVM) and radial basis function (RBF) models. The input dataset from the period of January 2004 to May 2011 used in the study was obtained from the Dongshi tide gauge station in Chiayi, Taiwan. Results showed that the ELM and RVM models outperformed the other methods. The performance of the RVM approach was superior in predicting the daily sea level time series given the minimum root mean square error of 34.73 mm and the maximum determination coefficient of 0.93 (R2) during the testing periods. Furthermore, the obtained results were in close agreement with the original tide-gauge data, which indicates that RVM approach is a promising alternative method for time series prediction and could be successfully used for daily sea level forecasts.

Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum

USGS Publications Warehouse

Sluijs, A.; Schouten, S.; Pagani, M.; Woltering, M.; Brinkhuis, H.; Damste, J.S.S.; Dickens, G.R.; Huber, M.; Reichart, G.-J.; Stein, R.; Matthiessen, J.; Lourens, L.J.; Pedentchouk, N.; Backman, J.; Moran, K.; Clemens, S.; Cronin, T.; Eynaud, F.; Gattacceca, J.; Jakobsson, M.; Jordan, R.; Kaminski, M.; King, J.; Koc, N.; Martinez, N.C.; McInroy, D.; Moore, T.C.; O'Regan, M.; Onodera, J.; Palike, H.; Rea, B.; Rio, D.; Sakamoto, T.; Smith, D.C.; St John, K.E.K.; Suto, I.; Suzuki, N.; Takahashi, K.; Watanabe, M. E.; Yamamoto, M.

2006-01-01

The Palaeocene/Eocene thermal maximum, ???55 million years ago, was a brief period of widespread, extreme climatic warming, that was associated with massive atmospheric greenhouse gas input. Although aspects of the resulting environmental changes are well documented at low latitudes, no data were available to quantify simultaneous changes in the Arctic region. Here we identify the Palaeocene/Eocene thermal maximum in a marine sedimentary sequence obtained during the Arctic Coring Expedition. We show that sea surface temperatures near the North Pole increased from ???18??C to over 23??C during this event. Such warm values imply the absence of ice and thus exclude the influence of ice-albedo feedbacks on this Arctic warming. At the same time, sea level rose while anoxic and euxinic conditions developed in the ocean's bottom waters and photic zone, respectively. Increasing temperature and sea level match expectations based on palaeoclimate model simulations, but the absolute polar temperatures that we derive before, during and after the event are more than 10??C warmer than those model-predicted. This suggests that higher-than-modern greenhouse gas concentrations must have operated in conjunction with other feedback mechanisms-perhaps polar stratospheric clouds or hurricane-induced ocean mixing-to amplify early Palaeogene polar temperatures. ?? 2006 Nature Publishing Group.

Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum.

PubMed

Sluijs, Appy; Schouten, Stefan; Pagani, Mark; Woltering, Martijn; Brinkhuis, Henk; Sinninghe Damsté, Jaap S; Dickens, Gerald R; Huber, Matthew; Reichart, Gert-Jan; Stein, Ruediger; Matthiessen, Jens; Lourens, Lucas J; Pedentchouk, Nikolai; Backman, Jan; Moran, Kathryn

2006-06-01

The Palaeocene/Eocene thermal maximum, approximately 55 million years ago, was a brief period of widespread, extreme climatic warming, that was associated with massive atmospheric greenhouse gas input. Although aspects of the resulting environmental changes are well documented at low latitudes, no data were available to quantify simultaneous changes in the Arctic region. Here we identify the Palaeocene/Eocene thermal maximum in a marine sedimentary sequence obtained during the Arctic Coring Expedition. We show that sea surface temperatures near the North Pole increased from 18 degrees C to over 23 degrees C during this event. Such warm values imply the absence of ice and thus exclude the influence of ice-albedo feedbacks on this Arctic warming. At the same time, sea level rose while anoxic and euxinic conditions developed in the ocean's bottom waters and photic zone, respectively. Increasing temperature and sea level match expectations based on palaeoclimate model simulations, but the absolute polar temperatures that we derive before, during and after the event are more than 10 degrees C warmer than those model-predicted. This suggests that higher-than-modern greenhouse gas concentrations must have operated in conjunction with other feedback mechanisms--perhaps polar stratospheric clouds or hurricane-induced ocean mixing--to amplify early Palaeogene polar temperatures.

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.

First results from IODP Expedition 325 to the Great Barrier Reef: unlocking climate and sea level secrets since the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Webster, J. M.; Yokoyama, Y.; Cotterill, C.; Expedition 325 Scientists

2010-12-01

Integrated Ocean Drilling Program (IODP) Exp. 325 (GBREC: Great Barrier Reef Environmental Change) that investigated fossil reefs on the shelf edge of the Great Barrier Reef (GBR), was the fourth IODP expedition to use a mission-specific platform, and was conducted by the European Consortium for Ocean Research Drilling (ECORD) Science Operator (ESO). The scientific objectives are to establish the course of sea level change, define sea-surface temperature variations, and to analyze the impact of these environmental changes on reef growth and geometry over the period of 20-10 ka. Exp.325 complements and extends the findings of the 2005 Exp. 310 (Tahiti Sea Level) that recovered Postglacial coral reef cores from the flanks of Tahiti from 41.6-117.5 meters below sea level and spanned ~16 to ~8 ka. Preliminary data confirms that Exp. 325 recovered truly unique and valuable fossil coral reef material from key periods in Earth's sea level and climate history from 30 to 9 ka. On Exp. 325 a succession of fossil reef structures preserved on the shelf edge seaward of the modern barrier reef were cored at three geographic locations (Hydrographers Passage, Noggin Pass and Ribbon Reef) from a dynamically positioned vessel in February-April 2010. A total of 34 boreholes were cored from 17 sites in four transects at depths ranging from 42.2 to 167.2 meters below sea level. Borehole logging of four boreholes provided continuous geophysical information about the drilled strata. The cores were split and described during the Onshore Science Party at the IODP Bremen Core Repository (Germany) in July 2010, where minimum and some standard measurements were made. Initial lithologic and biologic observations identified high-quality fossil coralgal frameworks, consistent with shallow, high energy reef settings - crucial for precise reconstructions of sea level and paleoclimate change. Preliminary C14-AMS and U-Th age interpretations from 60 core catcher samples confirmed that the cores span ages from >30 to 9 ka. This chronology, combined with their recovered depths, clearly demonstrates that Exp. 325 recovered coral reef material from key periods of interest for sea level change and environmental reconstruction, including the Last Glacial Maximum, Heinrich Events 1 and 2, 19ka-MWP, Bølling-Allerød, MWP1A, the Younger Dryas and MWPB. The new Exp. 325 cores are especially important because few fossil coral records span these intervals, and even fewer are from stable, passive margin settings far from the confounding influences of ice sheets or tectonic activity. This paper summarizes Exp. 325’s first results and their broader implications for understanding global sea-level and paleoclimate changes, and provides a first interpretation of how these reefs responded to environmental stress.

Increasing the highest storm surge in Busan harbor

NASA Astrophysics Data System (ADS)

Oh, Sang Myeong; Moon, Il-Ju; Kwon, Suk Jae

2017-04-01

One of the most pronounced effects of climate change in coastal regions is sea level rise and storm surges. Busan in particular, the fifth largest container handling port in the world, has suffered from serious storm surges and experienced a remarkable mean sea level (MSL) rise. This study investigates a long-term variation of annual maximum surge height (AMSH) using sea level data observed in Busan over 53 years (1962 2014). The decomposition of astronomical tides and surge components shows that the AMSH has increased 18 cm over 53 years (i.e., 3.5 mm/year), which is much larger than the MSL trend (2.5 mm/year) in Busan. This significant increase in AMSH is mostly explained by the increased intensity of landfall typhoons over the Korean peninsula (KP), which is associated with the increase of sea surface temperature and the decrease of vertical wind shear at mid-latitudes of the western North Pacific. In a projected future warming environment, the combination of an increasing MSL and AMSH will accelerate the occurrence of record-breaking extreme sea levels, which will be a potential threat in Busan harbor.

Modelling Antarctic sea-level data to explore the possibility of a dominant Antarctic contribution to meltwater pulse IA

NASA Astrophysics Data System (ADS)

Bassett, S. E.; Milne, G. A.; Bentley, M. J.; Huybrechts, P.

2007-09-01

We compare numerical predictions of glaciation-induced sea-level change to data from 8 locations around the Antarctic coast in order to test if the available data preclude the possibility of a dominant Antarctic contribution to meltwater pulse IA (mwp-IA). Results based on a subset of 7 spherically symmetric earth viscosity models and 6 different Antarctic deglaciation histories indicate that the sea-level data do not rule out a large Antarctic source for this event. Our preliminary analysis indicates that the Weddell Sea is the most likely source region for a large (˜9 m) Antarctic contribution to mwp-IA. The Ross Sea is also plausible as a significant contributor (˜5 m) from a sea-level perspective, but glacio-geological field observations are not compatible with such a large and rapid melt from this region. Our results suggest that the Lambert Glacier component of the East Antarctic ice sheet experienced significant retreat at the time of mwp-IA, but only contributed ˜0.15 m (eustatic sea-level change). All of the ice models considered under-predicted the isostatic component of the sea-level response in the Antarctic Peninsula and the Sôya Coast region of the East Antarctic ice sheet, indicating that the maximum ice thickness in these regions is underestimated. It is therefore plausible that ice melt from these areas, the Antarctic Peninsula in particular, could have made a significant contribution to mwp-IA.

Species- and tissue-specific mercury bioaccumulation in five fish species from Laizhou Bay in the Bohai Sea of China

NASA Astrophysics Data System (ADS)

Liu, Jinhu; Cao, Liang; Huang, Wei; Dou, Shuozeng

2013-05-01

Mercury (Hg) concentrations in the tissues (muscle, stomach, liver, gills, skin, and gonads) of five fish species (mullet Liza ha em atocheil us, flathead fish Platycephalus indicus, sea bass Lateolabrax japonic u s, mackerel Scomberomorus niphonius and silver pomfret Pampus argenteus) collected from Laizhou Bay in the Bohai Sea of China were investigated. The results indicate that Hg bioaccumulation in the five fish was tissue-specific, with the highest levels in the muscle and liver, followed by the stomach and gonads. The lowest levels were found in the gills and skin. Fish at higher trophic levels (flathead fish and sea bass) exhibited higher Hg concentrations than consumers at lower trophic levels. Mercury bioaccumulation tended to be positively correlated with fish length in mullet, silver pomfret, mackerel, and flathead fish, but was negatively correlated with fish length in sea bass. The Hg concentrations in the muscles of all fish species in Laizhou Bay were within the permissible limits of food safety set by national and international criteria. However, the suggesting maximum consumption of sea bass is 263 g per week for human health.

Impacts of climate-change-driven sea level rise on intertidal rocky reef habitats will be variable and site specific.

PubMed

Thorner, Jaqueline; Kumar, Lalit; Smith, Stephen D A

2014-01-01

Intertidal rocky reefs are complex and rich ecosystems that are vulnerable to even the smallest fluctuations in sea level. We modelled habitat loss associated with sea level rise for intertidal rocky reefs using GIS, high-resolution digital imagery, and LIDAR technology at fine-scale resolution (0.1 m per pixel). We used projected sea levels of +0.3 m, +0.5 m and +1.0 m above current Mean Low Tide Level (0.4 m). Habitat loss and changes were analysed for each scenario for five headlands in the Solitary Islands Marine Park (SIMP), Australia. The results indicate that changes to habitat extent will be variable across different shores and will not necessarily result in net loss of area for some habitats. In addition, habitat modification will not follow a regular pattern over the projected sea levels. Two of the headlands included in the study currently have the maximum level of protection within the SIMP. However, these headlands are likely to lose much of the habitat known to support biodiverse assemblages and may not continue to be suitable sanctuaries into the future. The fine-scale approach taken in this study thus provides a protocol not only for modelling habitat modification but also for future proofing conservation measures under a scenario of changing sea levels.

Quaternary Sea-ice history in the Arctic Ocean based on a new Ostracode sea-ice proxy

USGS Publications Warehouse

Cronin, T. M.; Gemery, L.; Briggs, W.M.; Jakobsson, M.; Polyak, L.; Brouwers, E.M.

2010-01-01

Paleo-sea-ice history in the Arctic Ocean was reconstructed using the sea-ice dwelling ostracode Acetabulastoma arcticum from late Quaternary sediments from the Mendeleyev, Lomonosov, and Gakkel Ridges, the Morris Jesup Rise and the Yermak Plateau. Results suggest intermittently high levels of perennial sea ice in the central Arctic Ocean during Marine Isotope Stage (MIS) 3 (25-45 ka), minimal sea ice during the last deglacial (16-11 ka) and early Holocene thermal maximum (11-5 ka) and increasing sea ice during the mid-to-late Holocene (5-0 ka). Sediment core records from the Iceland and Rockall Plateaus show that perennial sea ice existed in these regions only during glacial intervals MIS 2, 4, and 6. These results show that sea ice exhibits complex temporal and spatial variability during different climatic regimes and that the development of modern perennial sea ice may be a relatively recent phenomenon. ?? 2010.

Future sea-level rise in the Mediterranean Sea

NASA Astrophysics Data System (ADS)

Galassi, Gaia; Spada, Giorgio

2014-05-01

Secular sea level variations in the Mediterranean Sea are the result of a number of processes characterized by distinct time scales and spatial patterns. Here we predict the future sea level variations in the Mediterranean Sea to year 2050 combining the contributions from terrestrial ice melt (TIM), glacial isostatic adjustment (GIA), and the ocean response (OR) that includes the thermal expansion and the ocean circulation contributions. The three contributions are characterized by comparable magnitudes but distinctly different sea-level fingerprints across the Mediterranean basin. The TIM component of future sea-level rise is taken from Spada et al. (2013) and it is mainly driven by the melt of small glaciers and ice caps and by the dynamic ice loss from Antarctica. The sea-level fingerprint associated with GIA is studied using two distinct models available from the literature: ICE-5G(VM2) (Peltier, 2004) and the ice model progressively developed at the Research School of Earth Sciences (RSES) of the National Australian University (KL05) (see Fleming and Lambeck, 2004 and references therein). Both the GIA and the TIM sea-level predictions have been obtained with the aid of the SELEN program (Spada and Stocchi, 2007). The spatially-averaged OR component, which includes thermosteric and halosteric sea-level variations, recently obtained using a regional coupled ocean-atmosphere model (Carillo et al., 2012), vary between 2 and 7 cm according to scenarios adopted (EA1B and EA1B2, see Meehl at al., 2007). Since the sea-level variations associated with TIM mainly result from the gravitational interactions between the cryosphere components, the oceans and the solid Earth, and long-wavelength rotational variations, they are characterized by a very smooth global pattern and by a marked zonal symmetry reflecting the dipole geometry of the ice sources. Since the Mediterranean Sea is located in the intermediate far-field of major ice sources, TIM sea-level changes have sub-eustatic values (i.e. they do not exceed the global average) and show little (but still significant) variations across the basin associated with the subsidence driven by the meltwater load. For year 2050, TIM calculations predict a sea-level rise of ~10 and ~30 cm for the mid range and the high end scenarios, respectively. Mainly because of the distinct mantle viscosity profiles adopted in ICE-5G(VM2) and KL05, the GIA patterns differ significantly and, in contrast with the TIM fingerprint, are both characterized by strong variations across the Mediterranean Sea, showing maximum values in the bulk of the basin. For the OR component, a significant geographical variation is observed across the Mediterranean sub-basins, corresponding to different Atlantic boundary conditionsAccording to this study, the total future sea-level rise for year 2050 will reach maximum values for the extreme scenario (hig-hend prediction for TIM, KL05 for GIA and EA1B2 for OR) of ˜ 27 cm in average with peak of ˜ 30 cm in the central sub-basins. Our results show that when these three components of future sea-level rise are simultaneously considered, the spatial variability is enhanced because of the neatly distinct geometry of the three fingerprints. References: Carillo, A., Sannino, G., Artale, V., Ruti, P., Calmanti, S., DellAquila, A., 2012, Clim. Dyn. 39 (9-10), 2167-2184; Fleming, K. and Lambeck, K., 2004, Quat. Sci. Rev. 23 (9-10), 1053-1077; Meehl, G.A., and 11 others, 2007, in Climate Change 2007: The Physical Science Basis, Cambridge University Press; Peltier W.R., 2004, Annu. Rev. Earth Pl. Sc., 32, 111-149; Spada, G. and Stocchi, P., 2007, Comput. and Geosci., 33(4), 538-562; Spada G., Bamber J. L., Hurkmans R. T. W. L., 2013, Geophys. Res. Lett., 1-5, 40.

Forecasting Caspian Sea level changes using satellite altimetry data (June 1992-December 2013) based on evolutionary support vector regression algorithms and gene expression programming

NASA Astrophysics Data System (ADS)

Imani, Moslem; You, Rey-Jer; Kuo, Chung-Yen

2014-10-01

Sea level forecasting at various time intervals is of great importance in water supply management. Evolutionary artificial intelligence (AI) approaches have been accepted as an appropriate tool for modeling complex nonlinear phenomena in water bodies. In the study, we investigated the ability of two AI techniques: support vector machine (SVM), which is mathematically well-founded and provides new insights into function approximation, and gene expression programming (GEP), which is used to forecast Caspian Sea level anomalies using satellite altimetry observations from June 1992 to December 2013. SVM demonstrates the best performance in predicting Caspian Sea level anomalies, given the minimum root mean square error (RMSE = 0.035) and maximum coefficient of determination (R2 = 0.96) during the prediction periods. A comparison between the proposed AI approaches and the cascade correlation neural network (CCNN) model also shows the superiority of the GEP and SVM models over the CCNN.

14 CFR 29.87 - Height-velocity envelope.

Code of Federal Regulations, 2011 CFR

2011-01-01

...) Weight from the maximum weight (at sea level) to the highest weight approved for takeoff and landing at each altitude. For helicopters, this weight need not exceed the highest weight allowing hovering out-of...

14 CFR 29.87 - Height-velocity envelope.

Code of Federal Regulations, 2014 CFR

2014-01-01

...) Weight from the maximum weight (at sea level) to the highest weight approved for takeoff and landing at each altitude. For helicopters, this weight need not exceed the highest weight allowing hovering out-of...

14 CFR 29.87 - Height-velocity envelope.

Code of Federal Regulations, 2013 CFR

2013-01-01

...) Weight from the maximum weight (at sea level) to the highest weight approved for takeoff and landing at each altitude. For helicopters, this weight need not exceed the highest weight allowing hovering out-of...

14 CFR 29.87 - Height-velocity envelope.

Code of Federal Regulations, 2012 CFR

2012-01-01

...) Weight from the maximum weight (at sea level) to the highest weight approved for takeoff and landing at each altitude. For helicopters, this weight need not exceed the highest weight allowing hovering out-of...

Response of the Great Barrier Reef to sea-level and environmental changes over the past 30,000 years

NASA Astrophysics Data System (ADS)

Webster, Jody M.; Braga, Juan Carlos; Humblet, Marc; Potts, Donald C.; Iryu, Yasufumi; Yokoyama, Yusuke; Fujita, Kazuhiko; Bourillot, Raphael; Esat, Tezer M.; Fallon, Stewart; Thompson, William G.; Thomas, Alexander L.; Kan, Hironobu; McGregor, Helen V.; Hinestrosa, Gustavo; Obrochta, Stephen P.; Lougheed, Bryan C.

2018-06-01

Previous drilling through submerged fossil coral reefs has greatly improved our understanding of the general pattern of sea-level change since the Last Glacial Maximum, however, how reefs responded to these changes remains uncertain. Here we document the evolution of the Great Barrier Reef (GBR), the world's largest reef system, to major, abrupt environmental changes over the past 30 thousand years based on comprehensive sedimentological, biological and geochronological records from fossil reef cores. We show that reefs migrated seaward as sea level fell to its lowest level during the most recent glaciation ( 20.5-20.7 thousand years ago (ka)), then landward as the shelf flooded and ocean temperatures increased during the subsequent deglacial period ( 20-10 ka). Growth was interrupted by five reef-death events caused by subaerial exposure or sea-level rise outpacing reef growth. Around 10 ka, the reef drowned as the sea level continued to rise, flooding more of the shelf and causing a higher sediment flux. The GBR's capacity for rapid lateral migration at rates of 0.2-1.5 m yr-1 (and the ability to recruit locally) suggest that, as an ecosystem, the GBR has been more resilient to past sea-level and temperature fluctuations than previously thought, but it has been highly sensitive to increased sediment input over centennial-millennial timescales.

Observational analysis of air-sea fluxes and sea water temperature offshore South China Sea

NASA Astrophysics Data System (ADS)

Bi, X.; Huang, J.; Gao, Z.; Liu, Y.

2017-12-01

This paper investigates the air-sea fluxes (momentum flux, sensible heat flux and latent heat flux) from eddy covariance method based on data collected at an offshore observation tower in the South China Sea from January 2009 to December 2016 and sea water temperature (SWT) on six different levels based on data collected from November 2011 to June 2013. The depth of water at the tower over the sea averages about 15 m. This study presents the in-situ measurements of continuous air-sea fluxes and SWT at different depths. Seasonal and diurnal variations in air-sea fluxes and SWT on different depths are examined. Results show that air-sea fluxes and all SWT changed seasonally; sea-land breeze circulation appears all the year round. Unlike winters where SWT on different depths are fairly consistent, the difference between sea surface temperature (SST) and sea temperature at 10 m water depth fluctuates dramatically and the maximum value reaches 7 °C during summer.

Climatology of the winter Red Sea Trough

NASA Astrophysics Data System (ADS)

Awad, Adel M.; Almazroui, Mansour

2016-12-01

In this study, a new and objective method for detecting the Red Sea Trough (RST) was developed using mean sea level pressure (SLP) data from NCEP/NCAR reanalysis dataset from the winters of 1956 to 2015 to identify the Sudan Low and its trough. Approximately 96% of the winter RSTs were generated near two main sources, South Sudan and southeastern Sudan, and approximately 85% of these troughs were in four of the most outer areas surrounding the northern Red Sea. Moreover, from west to east of the Red Sea, the RST was affected by the relationships between the Siberian High and Azores High. The RST was oriented to the west when the strength of the Siberian High increased and to the east when the strength of the Azores High increased. Furthermore, the synoptic features of the upper level of the RST emphasize the impacts of subtropical anticyclones at 850 hPa on the orientation of the RST, the impacts of the northern cyclone trough and the maximum wind at a pressure level of 250 hPa. The average static stability between 1000 hPa and 500 hPa demonstrated that the RST followed the northern areas of low static stability. The results from previous studies were confirmed by a detailed case study of the RST that extended to its central outermost area. The results of a detailed case study of the short RST indicated that the trough becomes shorter with increasing static stability and that the Azores and Siberian high-pressure systems influence the northern region of the trough while the maximum upper wind shifts south of the climate position.

A note on sea level variability at Clipperton Island from GEOSAT and in-situ observations

NASA Astrophysics Data System (ADS)

Maul, George A.; Hansen, Donald V.; Bravo, Nicolas J.

During the 1986-1989 Exact Repeat Mission (ERM) of GEOSAT, in-situ observations of sea level at Clipperton Island (10°N/109°W) and satellite-tracked free-drifting drogued buoys in the eastern tropical Pacific Ocean are concurrently available. A map of the standard deviations of GEOSAT sea surface heights (2.9 years) shows a variance maximum along ˜12°N from Central America, past Clipperton to ˜160°W. Sea floor pressure gauge observations from a shallow (10m depth) site on Clipperton Island and an ERM crossover point in deep water nearby show a correlation of r = 0.76 with a residual of ±6.7 cm RMS. Approximately 17% of the difference (GEOSAT minus sea level) is characterized by a 4 cm amplitude 0° phase annual harmonic, which is probably caused by unaccounted-for tropospheric water vapor affecting the altimeter and/or ERM orbit error removal. Wintertime anticyclonic mesoscale eddies advecting past Clipperton Island each year have GEOSAT sea surface height and in-situ sea level signals of more than 30 cm, some of which are documented by the satellite-tracked drifters. Meridional profiles of the annual harmonic of zonal geostrophic current from GEOSAT and from the drifters both show synchronous maxima in the North Equatorial Countercurrent and the North Equatorial Current. Other Clipperton sea level maxima seen during late spring of each year may involve anticyclonic vortices formed along Central America the previous winter.

How much can Greenland melt? An upper bound on mass loss from the Greenland Ice Sheet through surface melting

NASA Astrophysics Data System (ADS)

Liu, X.; Bassis, J. N.

2015-12-01

With observations showing accelerated mass loss from the Greenland Ice Sheet due to surface melt, the Greenland Ice Sheet is becoming one of the most significant contributors to sea level rise. The contribution of the Greenland Ice Sheet o sea level rise is likely to accelerate in the coming decade and centuries as atmospheric temperatures continue to rise, potentially triggering ever larger surface melt rates. However, at present considerable uncertainty remains in projecting the contribution to sea level of the Greenland Ice Sheet both due to uncertainty in atmospheric forcing and the ice sheet response to climate forcing. Here we seek an upper bound on the contribution of surface melt from the Greenland to sea level rise in the coming century using a surface energy balance model coupled to an englacial model. We use IPCC Representative Concentration Pathways (RCP8.5, RCP6, RCP4.5, RCP2.6) climate scenarios from an ensemble of global climate models in our simulations to project the maximum rate of ice volume loss and related sea-level rise associated with surface melting. To estimate the upper bound, we assume the Greenland Ice Sheet is perpetually covered in thick clouds, which maximize longwave radiation to the ice sheet. We further assume that deposition of black carbon darkens the ice substantially turning it nearly black, substantially reducing its albedo. Although assuming that all melt water not stored in the snow/firn is instantaneously transported off the ice sheet increases mass loss in the short term, refreezing of retained water warms the ice and may lead to more melt in the long term. Hence we examine both assumptions and use the scenario that leads to the most surface melt by 2100. Preliminary models results suggest that under the most aggressive climate forcing, surface melt from the Greenland Ice Sheet contributes ~1 m to sea level by the year 2100. This is a significant contribution and ignores dynamic effects. We also examined a lower bound, assuming negligible longwave radiation and albedo near the maximum observed for freshly fallen snow. Even under this scenarios preliminary estimates suggest tens of centimeters of sea level rise by 2100.

A Late Pleistocene sea level stack

NASA Astrophysics Data System (ADS)

Spratt, Rachel M.; Lisiecki, Lorraine E.

2016-04-01

Late Pleistocene sea level has been reconstructed from ocean sediment core data using a wide variety of proxies and models. However, the accuracy of individual reconstructions is limited by measurement error, local variations in salinity and temperature, and assumptions particular to each technique. Here we present a sea level stack (average) which increases the signal-to-noise ratio of individual reconstructions. Specifically, we perform principal component analysis (PCA) on seven records from 0 to 430 ka and five records from 0 to 798 ka. The first principal component, which we use as the stack, describes ˜ 80 % of the variance in the data and is similar using either five or seven records. After scaling the stack based on Holocene and Last Glacial Maximum (LGM) sea level estimates, the stack agrees to within 5 m with isostatically adjusted coral sea level estimates for Marine Isotope Stages 5e and 11 (125 and 400 ka, respectively). Bootstrapping and random sampling yield mean uncertainty estimates of 9-12 m (1σ) for the scaled stack. Sea level change accounts for about 45 % of the total orbital-band variance in benthic δ18O, compared to a 65 % contribution during the LGM-to-Holocene transition. Additionally, the second and third principal components of our analyses reflect differences between proxy records associated with spatial variations in the δ18O of seawater.

Groundwater reorganization in the Floridan aquifer following Holocene sea-level rise

NASA Astrophysics Data System (ADS)

Morrissey, Sheila K.; Clark, Jordan F.; Bennett, Michael; Richardson, Emily; Stute, Martin

2010-10-01

Sea-level fluctuations, particularly those associated with glacial-interglacial cycles, can have profound impacts on the flow and circulation of coastal groundwater: the water found at present in many coastal aquifers may have been recharged during the last glacial period, when sea level was over 100m lower than present, and thus is not in equilibrium with present recharge conditions. Here we show that the geochemistry of the groundwater found in the Floridan Aquifer System in south Florida is best explained by a reorganization of groundwater flow following the sea-level rise at the end of the Last Glacial Maximum approximately 18,000 years ago. We find that the geochemistry of the fresh water found in the upper aquifers at present is consistent with recharge from meteoric water during the last glacial period. The lower aquifer, however, consists of post-sea-level-rise salt water that is most similar to that of the Straits of Florida, though with some dilution from the residual fresh water from the last glacial period circulation. We therefore suggest that during the last glacial period, the entire Floridan Aquifer System was recharged with meteoric waters. After sea level rose, the increased hydraulic head reduced the velocity of the groundwater flow. This velocity reduction trapped the fresh water in the upper aquifers and initiated saltwater circulation in the lower aquifer.

Eddy-induced Sea Surface Salinity changes in the tropical Pacific

NASA Astrophysics Data System (ADS)

Delcroix, T. C.; Chaigneau, A.; Soviadan, D.; Boutin, J.

2017-12-01

We analyse the Sea Surface Salinity (SSS) signature of westward propagating mesoscale eddies in the tropical Pacific by collocating 5 years (2010-2015) of SMOS (Soil Moisture and Ocean Salinity) SSS and altimetry-derived sea level anomalies. The main characteristics of mesoscale eddies are first identified in SLA maps. Composite analyses in the Central and Eastern ITCZ regions then reveal regionally dependent impacts with opposite SSS anomalies for the cyclonic and anticyclonic eddies. In the Central region (where we have the largest meridional SSS gradient), we found dipole-like SSS changes with maximum anomalies on the leading edge of the eddy. In the Eastern region (where we have the largest near-surface vertical salinity gradient) we found monopole-like SSS changes with maximum anomalies in the eddy centre. These dipole/monopole patterns and the rotational sense of eddies suggest the dominant role of horizontal and vertical advection in the Central and Eastern ITCZ regions, respectively.

Holocene sea-level change and Antarctic melting history derived from geological observations and geophysical modeling along the Shimokita Peninsula, northern Japan

NASA Astrophysics Data System (ADS)

Yokoyama, Y.; Okuno, J.; Miyairi, Y.; Obrochta, S.; Demboya, N.; Makino, Y.; Kawahata, H.

2012-12-01

A Mid to Late Holocene sea-level record based on combined geomorphological, geological and micropaleontological observations was obtained from well-developed wave cut benches subaerially exposed along the Shimokita Peninsula, northern Japan. Results indicate that the benches were formed during mid to late Holocene sea-level transgressions, reaching a maximum highstand level of 2 m above present at about 3,000 to 4,000 years ago. This timing corresponds to an abrupt, order of magnitude decrease in sedimentation rate as recorded in a core recovered from proximal Mutsu Bay. In addition, glacio-hydro-isostatic adjustment due to crustal deformation in response to postglacial sea-level rise was modeled, and results are consistent with the reconstructed local 2 m highstand. Given that meltwater contributions from the major North American and European ice sheets had largely ceased by 7,000 years ago, these independent lines of evidence, taken together, indicate that melting of the Antarctic ice sheet ended by late Holocene, around 3,000-4,000 years ago.

Tropical tales of polar ice: evidence of Last Interglacial polar ice sheet retreat recorded by fossil reefs of the granitic Seychelles islands

NASA Astrophysics Data System (ADS)

Dutton, Andrea; Webster, Jody M.; Zwartz, Dan; Lambeck, Kurt; Wohlfarth, Barbara

2015-01-01

In the search for a record of eustatic sea level change on glacial-interglacial timescales, the Seychelles ranks as one of the best places on the planet to study. Owing to its location with respect to the former margins of Northern Hemisphere ice sheets that wax and wane on orbital cycles, the local-or relative-sea level history is predicted to lie within a few meters of the globally averaged eustatic signal during the Last Interglacial period. We have surveyed and dated Last Interglacial fossil corals to ascertain peak sea level and hence infer maximum retreat of polar ice sheets during this time interval. We observe a pattern of gradually rising sea level in the Seychelles between ˜129 and 125 thousand years ago (ka), with peak eustatic sea level attained after 125 ka at 7.6 ± 1.7 m higher than present. After accounting for thermal expansion and loss of mountain glaciers, this sea-level budget would require ˜5-8 m of polar ice sheet contribution, relative to today's volume, of which only ˜2 m came from the Greenland ice sheet. This result clearly identifies the Antarctic ice sheet as a significant source of melt water, most likely derived from one of the unstable, marine-based sectors in the West and/or East Antarctic ice sheet. Furthermore, the establishment of a +5.9 ± 1.7 m eustatic sea level position by 128.6 ± 0.8 ka would require that partial AIS collapse was coincident with the onset of the sea level highstand.

Mercury distribution in ancient and modern sediments of northeastern Bering Sea

USGS Publications Warehouse

Nelson, C. Hans; Pierce, D.E.; Leong, K.W.; Wang, F.F.

1972-01-01

A reconnaissance of surface and subsurface sediments to a maximum depth of 244 feet below the sea floor shows that natural mercury anomalies from 0.2 to 1.3 ppm have been present in northeastern Bering Sea since early Pliocene. The anomalies and mean values are highest in modern beach (maximum 1.3 and mean 0.22 ppm Hg) and nearshore subsurface gravels (maximum 0.6 and mean .06 ppm Hg) along the highly mineralized Seward Peninsula and in organic rich silt (maximum 0.16 and mean 0.10 ppm Hg) throughout the region; the mean values are lowest in offshore sands (0.03 ppm Hg) . Although gold mining may be partially responsible for high mercury levels in the beaches near Nome, Alaska, equally high or greater concentrations of mercury occur in ancient glacial sediments immediately offshore (0.6 ppm) and in modern unpolluted beach sediments at Bluff (0.45 - 1.3 ppm); this indicates that the contamination effects of mining may be no greater than natural concentration processes in the Seward Peninsula region. The background content of mercury (0.03) throughout the central area of northeastern Bering Sea is similar to that elsewhere in the world. The low mean values (0.04 ppm) even immediately offshore from mercury-rich beaches, suggests that in the surface sediments of northeastern Bering Sea, the highest concentrations are limited to the beaches near mercury sources; occasionally, however, low mercury anomalies occur offshore in glacial drift derived from mercury source regions of Chukotka and Seward Peninsula and reworked by Pleistocene shoreline processes. The minimal values offshore may be attributable to beach entrapment of heavy minerals containing mercury and/or dilution effects of modern sedimentation.

Consideration of vertical uncertainty in elevation-based sea-level rise assessments: Mobile Bay, Alabama case study

USGS Publications Warehouse

Gesch, Dean B.

2013-01-01

The accuracy with which coastal topography has been mapped directly affects the reliability and usefulness of elevationbased sea-level rise vulnerability assessments. Recent research has shown that the qualities of the elevation data must be well understood to properly model potential impacts. The cumulative vertical uncertainty has contributions from elevation data error, water level data uncertainties, and vertical datum and transformation uncertainties. The concepts of minimum sealevel rise increment and minimum planning timeline, important parameters for an elevation-based sea-level rise assessment, are used in recognition of the inherent vertical uncertainty of the underlying data. These concepts were applied to conduct a sea-level rise vulnerability assessment of the Mobile Bay, Alabama, region based on high-quality lidar-derived elevation data. The results that detail the area and associated resources (land cover, population, and infrastructure) vulnerable to a 1.18-m sea-level rise by the year 2100 are reported as a range of values (at the 95% confidence level) to account for the vertical uncertainty in the base data. Examination of the tabulated statistics about land cover, population, and infrastructure in the minimum and maximum vulnerable areas shows that these resources are not uniformly distributed throughout the overall vulnerable zone. The methods demonstrated in the Mobile Bay analysis provide an example of how to consider and properly account for vertical uncertainty in elevation-based sea-level rise vulnerability assessments, and the advantages of doing so.

Deglaciation of the Eurasian ice sheet complex

NASA Astrophysics Data System (ADS)

Patton, Henry; Hubbard, Alun; Andreassen, Karin; Auriac, Amandine; Whitehouse, Pippa L.; Stroeven, Arjen P.; Shackleton, Calvin; Winsborrow, Monica; Heyman, Jakob; Hall, Adrian M.

2017-08-01

The Eurasian ice sheet complex (EISC) was the third largest ice mass during the Last Glacial Maximum with a span of over 4500 km and responsible for around 20 m of eustatic sea-level lowering. Whilst recent terrestrial and marine empirical insights have improved understanding of the chronology, pattern and rates of retreat of this vast ice sheet, a concerted attempt to model the deglaciation of the EISC honouring these new constraints is conspicuously lacking. Here, we apply a first-order, thermomechanical ice sheet model, validated against a diverse suite of empirical data, to investigate the retreat of the EISC after 23 ka BP, directly extending the work of Patton et al. (2016) who modelled the build-up to its maximum extent. Retreat of the ice sheet complex was highly asynchronous, reflecting contrasting regional sensitivities to climate forcing, oceanic influence, and internal dynamics. Most rapid retreat was experienced across the Barents Sea sector after 17.8 ka BP when this marine-based ice sheet disintegrated at a rate of ∼670 gigatonnes per year (Gt a-1) through enhanced calving and interior dynamic thinning, driven by oceanic/atmospheric warming and exacerbated by eustatic sea-level rise. From 14.9 to 12.9 ka BP the EISC lost on average 750 Gt a-1, peaking at rates >3000 Gt a-1, roughly equally partitioned between surface melt and dynamic losses, and potentially contributing up to 2.5 m to global sea-level rise during Meltwater Pulse 1A. Independent glacio-isostatic modelling constrained by an extensive inventory of relative sea-level change corroborates our ice sheet loading history of the Barents Sea sector. Subglacial conditions were predominately temperate during deglaciation, with over 6000 subglacial lakes predicted along with an extensive subglacial drainage network. Moreover, the maximum EISC and its isostatic footprint had a profound impact on the proglacial hydrological network, forming the Fleuve Manche mega-catchment which had an area of ∼2.5 × 106 km2 and drained the present day Vistula, Elbe, Rhine and Thames rivers through the Seine Estuary. During the Bølling/Allerød oscillation after c. 14.6 ka BP, two major proglacial lakes formed in the Baltic and White seas, buffering meltwater pulses from eastern Fennoscandia through to the Younger Dryas when these massive proglacial freshwater lakes flooded into the North Atlantic Ocean. Deglaciation temporarily abated during the Younger Dryas stadial at 12.9 ka BP, when remnant ice across Svalbard, Franz Josef Land, Novaya Zemlya, Fennoscandia and Scotland experienced a short-lived but dynamic re-advance. The final stage of deglaciation converged on present day ice cover around the Scandes mountains and the Barents Sea by 8.7 ka BP, although the phase-lagged isostatic recovery still continues today.

Geoarchaeological response to landscape changes of the Greek continental shelf since the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Kapsimalis, Vasilios; Pavlopoulos, Kosmas; Panagiotopoulos, Ioannis

2010-05-01

An overview of geological, sedimentological, palaeoclimatic, archaeological and mythological data is presented in order to detect the geomorphological changes of the Aegean and Ionian shelves during the last sea-level transgression, and comprehend the consequent prehistoric human adaptations. The irregular rise of sea level since the Last Glacial Maximum forced the Palaeolithic human to abandon its settlements located near the old (lower) coastlines and to move landward in new positions. Commonly, the coastline movement was very slow causing no significant impact on human activities; however in some cases, the transgression was very prompt causing human migration towards highlands. In some very gentle-dipped and wide regions, e.g. the North Aegean plateau, the sea-level rise caused a rapid coastline retreat (in some extreme case as fast as 10 m/yr) and inundation of an extended surface area. However, at the same time, in the steep parts of the Greek shelf, e.g. the Kyparissiakos Gulf and Crete, the coastline advanced landwards with a slow motion (commonly, a few cm/yr) covering small areas. In addition, coastal regions with particular geomorphologic characteristics, e.g. coastal paleo-lakes protected by a sill (gulfs of Corinth, Amvrakikos, Pagasitikos Evvoikos, Saronikos), were deluged by the sea during different periods and under different intensity, depending on the elevation of the sill and the manner of its overflow. Although the presence of Palaeolithic human in the Greek mainland has been confirmed by several archaeological excavations, there is no certain evidence for human settlement in the deep parts of Greek shelf. However, many archaeologists have suggested that some of Palaeolithic people lived on the shelf, when the sea level was lower than its present position. Nevertheless, some potential Palaeolithic migration routes can be indicated taking into account (a) the palaeogeographic reconstruction of Greek shelf over the Last Quaternary; (b) archaeological data coming from, nowadays, coastal prehistoric sites; and (a) mythological references. At the Last Gracial Maximum, Palaeolithic human dispersed on the subaerially-exposed Greek shelf searching for places with mild climates, drinking water and food. When the sea-lever started to rise (ca. 18 kyr B.P.), people moved inland following some main migration routes on the North Aegean shelf, Thermaikos Gulf, Pagasitikos/North Evvoikos Gulf, Saronikos Gulf, Argolikos Gulf, Patrakos/Corinthian Gulf, and north Ionian shelf. Frequently, at the landward end of these routes, there are Mesolithic or Neolithic sites established when the sea level reached approximately its present position and preserved because coastal or marine processes did not destroyed them. Furthermore, the long-standing migration could be recorded in the social memory like a landward escapement from a destructive flood.

Effect of Climate Change on Water Temperature and ...

EPA Pesticide Factsheets

There is increasing evidence that our planet is warming and this warming is also resulting in rising sea levels. Estuaries which are located at the interface between land and ocean are impacted by these changes. We used CE-QUAL-W2 water quality model to predict changes in water temperature as a function of increasing air temperatures and rising sea level for the Yaquina Estuary, Oregon (USA). Annual average air temperature in the Yaquina watershed is expected to increase about 0.3 deg C per decade by 2040-2069. An air temperature increase of 3 deg C in the Yaquina watershed is likely to result in estuarine water temperature increasing by 0.7 to 1.6 deg C. Largest water temperature increases are expected in the upper portion of the estuary, while sea level rise may ameliorate some of the warming in the lower portion of the estuary. Smallest changes in water temperature are predicted to occur in the summer, and maximum changes during the winter and spring. Increases in air temperature may result in an increase in the number of days per year that the 7-day maximum average temperature exceeds 18 deg C (criterion for protection of rearing and migration of salmonids and trout) as well as other water quality concerns. In the upstream portion of the estuary, a 4 deg C increase in air temperature is predicted to cause an increase of 40 days not meeting the temperature criterion, while in the lower estuary the increase will depend upon rate of sea level rise (rang

The build-up, configuration, and dynamical sensitivity of the Eurasian ice-sheet complex to Late Weichselian climatic and oceanic forcing

NASA Astrophysics Data System (ADS)

Patton, Henry; Hubbard, Alun; Andreassen, Karin; Winsborrow, Monica; Stroeven, Arjen P.

2016-12-01

The Eurasian ice-sheet complex (EISC) was the third largest ice mass during the Last Glacial Maximum (LGM), after the Antarctic and North American ice sheets. Despite its global significance, a comprehensive account of its evolution from independent nucleation centres to its maximum extent is conspicuously lacking. Here, a first-order, thermomechanical model, robustly constrained by empirical evidence, is used to investigate the dynamics of the EISC throughout its build-up to its maximum configuration. The ice flow model is coupled to a reference climate and applied at 10 km spatial resolution across a domain that includes the three main spreading centres of the Celtic, Fennoscandian and Barents Sea ice sheets. The model is forced with the NGRIP palaeo-isotope curve from 37 ka BP onwards and model skill is assessed against collated flowsets, marginal moraines, exposure ages and relative sea-level history. The evolution of the EISC to its LGM configuration was complex and asynchronous; the western, maritime margins of the Fennoscandian and Celtic ice sheets responded rapidly and advanced across their continental shelves by 29 ka BP, yet the maximum aerial extent (5.48 × 106 km2) and volume (7.18 × 106 km3) of the ice complex was attained some 6 ka later at c. 22.7 ka BP. This maximum stand was short-lived as the North Sea and Atlantic margins were already in retreat whilst eastern margins were still advancing up until c. 20 ka BP. High rates of basal erosion are modelled beneath ice streams and outlet glaciers draining the Celtic and Fennoscandian ice sheets with extensive preservation elsewhere due to frozen subglacial conditions, including much of the Barents and Kara seas. Here, and elsewhere across the Norwegian shelf and North Sea, high pressure subglacial conditions would have promoted localised gas hydrate formation.

Searching for Eustasy in Pliocene Sea-Level Records (Invited)

NASA Astrophysics Data System (ADS)

Raymo, M. E.; Hearty, P. J.; O'Leary, M.; Mitrovica, J.; Deconto, R.; Inglis, J. D.; Robinson, M. M.

2010-12-01

It is widely accepted that greenhouse gas-induced warming over the next few decades to centuries could lead to a rise in sea level due to melting ice caps. Yet despite the enormous social and economic consequences for society, our ability to predict the likelihood and location of future melting is hampered by an insufficient theoretical and historical understanding of ice sheet behavior in the past. Various lines of evidence suggest that CO2 levels in the mid-Pliocene were between 350-450 ppm, similar to today, and it is important that significant effort be made to confirm these estimates, especially in light of policy discussions that seek to determine a “safe” level of atmospheric CO2. Likewise, accurate estimates of mid-Pliocene sea levels are necessary if we are to better constrain Greenland and Antarctic ice sheet stability in a slightly warmer world. Current published estimates of mid-Pliocene sea level (during times of maximum insolation forcing) range from +5m to >+40m (relative to present) reflecting a huge range of uncertainty in the sensitivity of polar ice sheets, including the East Antarctic Ice Sheet, to a modest global warming. Accurate determination of the maximum mid-Pliocene sea level rise is needed if climate and ice sheet modelers are to better assess the robustness of models used to predict the effects of anthropogenic global warming. Pliocene ice volume/highstand estimates fall into two classes, those derived from geologic evidence of past high stands and those derived from geochemical proxies of ice-sensitive changes in ocean chemistry. Both methods have significant errors and uncertainties associated with them. Recent multidisciplinary work along the intra-plate continental margin of Roe Plain (~250 x 30 km) on the southern coastline of Western Australia provides additional constraints on sea level during the mid-Pliocene. Outcroppings of shore-proximal marine deposits are observed at two distinct elevations across the plain, +28 ± 2 m and +18 ± 2 m. Definitive sedimentary intertidal indications (e.g., concentrated concave down bivalves characteristic of a swash zone) and subtidal biofacies including articulated valves are found throughout the deposits and suggest the occurrence two distinct highstand events. Preliminary Sr-isotopes yield a broad range of mid to late Pliocene ages. These data will be discussed in light of possible ice volume, dynamic topography, and isostatic effects. Building on these data we present a strategy for improving the accuracy of mid Pliocene sea level estimates.

Modelling storm development and the impact when introducing waves, sea spray and heat fluxes

NASA Astrophysics Data System (ADS)

Wu, Lichuan; Rutgersson, Anna; Sahlée, Erik

2015-04-01

In high wind speed conditions, sea spray generated due to intensity breaking waves have big influence on the wind stress and heat fluxes. Measurements show that drag coefficient will decrease in high wind speed. Sea spray generation function (SSGF), an important term of wind stress parameterization in high wind speed, usually treated as a function of wind speed/friction velocity. In this study, we introduce a wave state depended SSGG and wave age depended Charnock number into a high wind speed wind stress parameterization (Kudryavtsev et al., 2011; 2012). The proposed wind stress parameterization and sea spray heat fluxes parameterization from Andreas et al., (2014) were applied to an atmosphere-wave coupled model to test on four storm cases. Compared with measurements from the FINO1 platform in the North Sea, the new wind stress parameterization can reduce the forecast errors of wind in high wind speed range, but not in low wind speed. Only sea spray impacted on wind stress, it will intensify the storms (minimum sea level pressure and maximum wind speed) and lower the air temperature (increase the errors). Only the sea spray impacted on the heat fluxes, it can improve the model performance on storm tracks and the air temperature, but not change much in the storm intensity. If both of sea spray impacted on the wind stress and heat fluxes are taken into account, it has the best performance in all the experiment for minimum sea level pressure and maximum wind speed and air temperature. Andreas, E. L., Mahrt, L., and Vickers, D. (2014). An improved bulk air-sea surface flux algorithm, including spray-mediated transfer. Quarterly Journal of the Royal Meteorological Society. Kudryavtsev, V. and Makin, V. (2011). Impact of ocean spray on the dynamics of the marine atmospheric boundary layer. Boundary-layer meteorology, 140(3):383-410. Kudryavtsev, V., Makin, V., and S, Z. (2012). On the sea-surface drag and heat/mass transfer at strong winds. Technical report, Royal Netherlands Meteorological Institute.

How large is the subducted water flux? New constraints on mantle regassing rates

NASA Astrophysics Data System (ADS)

Parai, R.; Mukhopadhyay, S.

2012-02-01

Estimates of the subducted water (H2O) flux have been used to discuss the regassing of the mantle over Earth history. However, these estimates vary widely, and some are large enough to have reduced the volume of water in the global ocean by a factor of two over the Phanerozoic. In light of uncertainties in the hydration state of subducting slabs, magma production rates and mantle source water contents, we use a Monte Carlo simulation to set limits on long-term global water cycling and the return flux of water to the deep Earth. Estimates of magma production rates and water contents in primary magmas generated at ocean islands, mid-ocean ridges, arcs and back-arcs are paired with estimates of water entering trenches via subducting oceanic slab in order to construct a model of the deep Earth water cycle. The simulation is constrained by reconstructions of Phanerozoic sea level change, which suggest that ocean volume is near steady-state, though a sea level decrease of up to 360 m may be supported. We provide limits on the return flux of water to the deep Earth over the Phanerozoic corresponding to a near steady-state exosphere (0-100 meter sea level decrease) and a maximum sea level decrease of 360 m. For the near steady-state exosphere, the return flux is 1.4 - 2.0- 0.3+ 0.4 × 1013 mol/yr, corresponding to 2-3% serpentinization in 10 km of lithospheric mantle. The return flux that generates the maximum sea level decrease over the Phanerozoic is 3.5- 0.3+ 0.4 × 1013 mol/yr, corresponding to 5% serpentinization in 10 km of lithospheric mantle. Our estimates of the return flux of water to the mantle are up to 7 times lower than previously suggested. The imbalance between our estimates of the return flux and mantle output flux leads to a low rate of increase in bulk mantle water content of up to 24 ppm/Ga.

Atmospheric forcing on the seasonal variability of sea level at Cochin, southwest coast of India

NASA Astrophysics Data System (ADS)

Srinivas, K.; Dinesh Kumar, P. K.

2006-07-01

The seasonal cycles of some atmospheric parameters at Cochin (southwest coast of India) have been studied with a specific emphasis on the role played by them in forcing the seasonal sea level. Equatorward along-shore wind stress as well as equatorward volume transport by coastal currents along the Indian peninsula could play an important role in the sea level low during the premonsoon and southwest monsoon seasons. During postmonsoon season, along-shore wind stress plays no major role in the high sea level whereas this could be due to the poleward volume transport by the coastal along-shore currents. Atmospheric pressure and river discharge do not seem to influence much the sea level during the southwest monsoon period, even though the river discharge during that period is considerable. The sea level was minimal during the southwest monsoon season, when the river discharge was at its annual maximum. The difference between the seasonal march of observed and pressure corrected sea level (CSL) was not significant for the study region. Harmonic analysis of the climatological data on the various parameters revealed that air temperature is the only parameter with a dominance of the semi-annual over the annual cycle. Cross-shore wind stress indicated strong interannual variability whereas relative density showed strong seasonal variability. The climatological seasonal cycles of CSL at eight other tide gauge stations along the west coast of the Indian subcontinent are also examined, to assess the role of various forcings on the seasonal sea level cycle. The signatures of El Nino-Southern Oscillation (ENSO) phenomenon could be seen in some of the parameters (SST, air temperature, atmospheric pressure, along-shore wind stress, relative density and sea level). The signature of ENSO was particularly strong in the case of atmospheric pressure followed by relative density, the variance accounted by the relationship being 47% and 16%, respectively.

Contribution of atmospheric circulation to recent off-shore sea-level variations in the Baltic Sea and the North Sea

NASA Astrophysics Data System (ADS)

Karabil, Sitar; Zorita, Eduardo; Hünicke, Birgit

2018-01-01

The main purpose of this study is to quantify the contribution of atmospheric factors to recent off-shore sea-level variability in the Baltic Sea and the North Sea on interannual timescales. For this purpose, we statistically analysed sea-level records from tide gauges and satellite altimetry and several climatic data sets covering the last century. Previous studies had concluded that the North Atlantic Oscillation (NAO) is the main pattern of atmospheric variability affecting sea level in the Baltic Sea and the North Sea in wintertime. However, we identify a different atmospheric circulation pattern that is more closely connected to sea-level variability than the NAO. This circulation pattern displays a link to sea level that remains stable through the 20th century, in contrast to the much more variable link between sea level and the NAO. We denote this atmospheric variability mode as the Baltic Sea and North Sea Oscillation (BANOS) index. The sea-level pressure (SLP) BANOS pattern displays an SLP dipole with centres of action located over (5° W, 45° N) and (20° E, 70° N) and this is distinct from the standard NAO SLP pattern in wintertime. In summertime, the discrepancy between the SLP BANOS and NAO patterns becomes clearer, with centres of action of the former located over (30° E, 45° N) and (20° E, 60° N). This index has a stronger connection to off-shore sea-level variability in the study area than the NAO in wintertime for the period 1993-2013, explaining locally up to 90 % of the interannual sea-level variance in winter and up to 79 % in summer. The eastern part of the Gulf of Finland is the area where the BANOS index is most sensitive to sea level in wintertime, whereas the Gulf of Riga is the most sensitive region in summertime. In the North Sea region, the maximum sea-level sensitivity to the BANOS pattern is located in the German Bight for both winter and summer seasons. We investigated, and when possible quantified, the contribution of several physical mechanisms which may explain the link between the sea-level variability and the atmospheric pattern described by the BANOS index. These mechanisms include the inverse barometer effect (IBE), freshwater balance, net energy surface flux and wind-induced water transport. We found that the most important mechanism is the IBE in both wintertime and summertime. Assuming a complete equilibration of seasonal sea level to the SLP gradients over this region, the IBE can explain up to 88 % of the sea-level variability attributed to the BANOS index in wintertime and 34 % in summertime. The net energy flux at the surface is found to be an important factor for the variation of sea level, explaining 35 % of sea-level variance in wintertime and a very small amount in summer. The freshwater flux could only explain 27 % of the variability in summertime and a negligible part in winter. In contrast to the NAO, the direct wind forcing associated with the SLP BANOS pattern does not lead to transport of water from the North Sea into the Baltic Sea in wintertime.

IInvestigations of space-time variability of the sea level in the Barents Sea and the White Sea by satellite altimetry data and results of hydrodynamic modelling

NASA Astrophysics Data System (ADS)

Lebedev, S. A.; Zilberstein, O. I.; Popov, S. K.; Tikhonova, O. V.

2003-04-01

The problem of retrieving of the sea level anomalies in the Barents and White Seas from satellite can be considered as two different problems. The first one is to calculate the anomalies of sea level along the trek taking into account all amendments including tidal heights. The second one is to obtain of fields of the sea level anomalies on the grid over one cycle of the exact repeat altimetry mission. Experience results show that there is preferable to use the regional tidal model for calculating tidal heights. To construct of the anomalies fields of the sea level during the exact repeat mission (cycle 35 days for ERS-1 and ERS-2), when a density of the coverage of the area of water of the Barents and White Seas by satellite measurements achieves maximum. It is necessary to solve the problem of the error minimum. This error is based by the temporal difference of the measurements over one cycle and by the specific of the hydrodynamic regime of the both seas (tidal, storm surge variations, tidal currents). To solve this problem it is assumed to use the results of the hydrodynamic modeling. The error minimum is preformed by the regression of the model results and satellite measurements. As a version it is considered the possibility of the utilizing of the neuronet obtained by the model results to construct maps of the sea level anomalies. The comparison of the model results and the calculation of the satellite altimetry variability of the sea level of Barents and White Seas shows a good coincidence between them. The satellite altimetry data of ERS-1/2 and TOPEX/POSEIDON of Ocean Altimeter Pathfinder Project (NASA/GSFC) has been used in this study. Results of the regional tidal model computations and three dimensional baroclinic model created in the Hydrometeocenter have been used as well. This study also exploited the atmosphere date of the Project REANALYSIS. The research was undertaken with partial support from the Russian Basic Research Foundation (Project No. 01-07-90106).

The sea-level highstand correlated to marine isotope stage (MIS) 7 in the coastal plain of the state of Rio Grande do Sul, Brazil.

PubMed

Lopes, Renato P; Dillenburg, Sergio R; Schultz, Cesar L; Ferigolo, Jorge; Ribeiro, Ana Maria; Pereira, Jamil C; Holanda, Elizete C; Pitana, Vanessa G; Kerber, Leonardo

2014-12-01

The coastal plain of the state of Rio Grande do Sul, in southern Brazil, includes four barrier-lagoon depositional systems formed by successive Quaternary sea-level highstands that were correlated to marine isotope stages (MIS) 11, 9, 5 and 1, despite the scarcity of absolute ages. This study describes a sea-level highstand older than MIS 5, based on the stratigraphy, ages and fossils of the shallow marine facies found in coastal barrier (Barrier II). This facies outcrops along the banks of Chuí Creek, it is composed of fine, well-sorted quartz sand and contains ichnofossils Ophiomorpha nodosa and Rosselia sp., and molluscan shells. The sedimentary record indicates coastal aggradation followed by sea-level fall and progradation of the coastline. Thermoluminescence (TL) and electron spin resonance (ESR) ages from sediments and fossil shells point to an age of ∼220 ka for the end of this marine transgression, thus correlating it to MIS 7 (substage 7e). Altimetric data point to a maximum amplitude of about 10 meters above present-day mean sea-level, but tectonic processes may be involved. Paleoceanographic conditions at the time of the highstand and correlations with other deposits in the Brazilian coasts are also discussed.

The sea-level highstand correlated to marine isotope stage (MIS) 7 in the coastal plain of the state of Rio Grande do Sul, Brazil.

PubMed

Lopes, Renato P; Dillenburg, Sergio R; Schultz, Cesar L; Ferigolo, Jorge; Ribeiro, Ana Maria; Pereira, Jamil C; Holanda, Elizete C; Pitana, Vanessa G; Kerber, Leonardo

2014-12-09

The coastal plain of the state of Rio Grande do Sul, in southern Brazil, includes four barrier-lagoon depositional systems formed by successive Quaternary sea-level highstands that were correlated to marine isotope stages (MIS) 11, 9, 5 and 1, despite the scarcity of absolute ages. This study describes a sea-level highstand older than MIS 5, based on the stratigraphy, ages and fossils of the shallow marine facies found in coastal barrier (Barrier II). This facies outcrops along the banks of Chuí Creek, it is composed of fine, well-sorted quartz sand and contains ichnofossils Ophiomorpha nodosa and Rosselia sp., and molluscan shells. The sedimentary record indicates coastal aggradation followed by sea-level fall and progradation of the coastline. Thermoluminescence (TL) and electron spin resonance (ESR) ages from sediments and fossil shells point to an age of ∼220 ka for the end of this marine transgression, thus correlating it to MIS 7 (substage 7e). Altimetric data point to a maximum amplitude of about 10 meters above present-day mean sea-level, but tectonic processes may be involved. Paleoceanographic conditions at the time of the highstand and correlations with other deposits in the Brazilian coasts are also discussed.

The Potential Effect of Sea Level Rise on Coastal Property Values

NASA Astrophysics Data System (ADS)

O'Donnell, J.

2015-12-01

It is well established that one consequence of increasing global sea level is that the frequency of flooding at low-lying coastal sites will increase. We review recent evidence that the effects coastal geometry will create substantial spatial variations in the changes in flooding frequency with scales of order 100km. Using a simple model of the evolution of coastal property values we demonstrate that a consequence of sea level rise is that the appreciation of coastal properties will peak, and then decline relative to higher properties. The time when the value reach a maximum is shown to depend upon the demand for the coastal property, and the local rate of change of flooding frequency due to sea level rise. The simple model is then extended to include, in an elementary manner, the effects on the value of adjacent but higher properties. We show that the effect of increased flooding frequency of the lower properties leads to an accelerated appreciation of the value of upland properties and an accelerated decline in the value of the coastal properties. We then provide some example calculations for selected sites. We conclude with a discussion of comparisons of the prediction of the analyses to recent data, and then comments on the impact of sea level rise on tax base of coastal communities.

On The Black Sea Surozhian

NASA Astrophysics Data System (ADS)

Caraivan, Glicherie; Corneliu, Cerchia

2016-04-01

Some Black Sea researchers still support the idea of no other connection to the Mediterranean Sea between LGM and Karangatian Stage (Riss - Wurm). We try to clarify the source of these disagreements. C14 AMS age data (HERAS Project) made on undisturbed samples from a new Mamaia drilling hole where compared with the classical Black Sea stratigraphic schemes. A first transgressive event (Zone D) is found between 38.00 - 20.20 m depth. Zone D4 shows a fairly rapid rise of sea level, about 10 m below the present one indicating an inner shelf marine polyhaline environment. AMS age data show 14C ages between 53690 - 47359 y (MIS 1), corresponding to the "Surozhian Beds" of Popov. The "beach rock" from Zone E marks the decrease of the sea level after the maximum reached in Zone D4. Zone E mollusc shells AMS data, indicate 14C ages of 48724 - 44604 y, suggesting a long-time reworked material from the previous D4 zone sediments, and represents the beginning of the "regressive Tarkankutian" sequence.The Last Glacial Maximum (LGM) led to the retreat of the sea level down to about 100 m below the current one (27-17 ky BP), followed by an retreat of the shoreline to the present position. At the beginning of the Holocene - MIS 1 (8408-8132 cal. y BP), Black Sea brackish water level grew rapidly, up to -14 m below the present one (Zone F: 22, 57-20, 20 m). Zone F deposits could be correlated with the Bugazian strata. Then, a continuous rising of the Black Sea level is recorded up to a maximum of -2 m under the present one, about 6789 - 7063 cal. y BP, when a transgressive spurt ("Neolithic transgression") may have taken place. After that, given a weak Danubian sedimentary input, coastal erosion intensified. The coarse sandy sediments were reworked and pushed over the previous peat deposits, and suggest a classical "sedimentary regression", not a sea-level decrease. During the last 1.5 ky, sea level has risen towards the current one. Previous C14 dates from "Karangatian stratotypes", show ages between 27390 - 42120 y BP. Our AMS C14 data on Surozhian mollusk indicate ages between 47359 - 53690 cal. y BP. We argue that "Surozhian" is likely the classic "Karangatian" defined by Nevesskaia that does not correspond to the Riss-Wurm, but to the Middle Wurm instead. The generally accepted "Karangatian", placed in the Riss-Wurm interval is much older. Similarly, the Surozhian (transgressive) cannot be Tarhankutian (regressive). References Caraivan, G., 2010. Studiul sedimentologic al depozitelor de plajǎ si de selful intern al M\\varii Negre între Portița si Tuzla. [Sedimentological Study of Beach and Inner Shelf Romanian Black Sea Deposits]. Ex Ponto, Constanta. (In Romanian) Caraivan, G., Fulga, C., Opreanu, P., 2012. Upper Quaternary evolution of the Mamaia Lake area (Romanian Black Sea shore). Quaternary International 261: 14-20. Caraivan, G., Opreanu, P., Voinea, V., Pojar, I., Sava, T., Giosan, L. „Holocene landscape changes and human communities' migration in the western part of the Black Sea (Mamaia Lake area)", In: IGCP 610 Proceedings of the Third Plenary Conference, Astrakhan, Russia, 22-30 September 2015. Giosan L.et al, 2012. Early Anthropogenic Transformation of the Danube-Black Sea System. Sci Rep. 2012; 2:582 Nevesskaia, L.A. 1965. Pozdrecetverticinîe dvustvorcestîe molluski Cernogo Moria, ih sistematica i ekologhia, Trudî Pal. Inst., 105, Moskva. Shcherbakov, F.A., Koreneva, E.V., and Zabelina, E.K., 1977. Stratigrafiia pozdnechetvertichnykh otlozhenii Chernogo moria [Stratigraphy of the Late Quaternary deposits in the Black Sea]. In Pozdnechetvertichnaia istoriia i sedimentogenez okrainikh i vnutrennikh morei [Late-Quaternary History and Sedimentogenesis in Marginal and Inland Seas]. Nauka, Moscow, pp. 46-51. Yanko-Hombach, V.V., 2007. Controversy over Noah's Flood in the Black Sea: Geological and foraminiferal evidence from the shelf. In Yanko-Hombach, V., Gilbert, A.S., Panin, N., and Dolukanov, P.M. (eds.), [The Black Sea Flood Question: Changes in Coastline, Climate and Human Settlement]. Springer, Dordrecht, pp. 149-203. Semenenko, V. N.; Kovaliuh, N.N., 1973. Absoliutnîi vozrast verhnecertverticinîh otlojenii Azovo-Cernomorskogo basseina po dannîm radiouglerodnogo analiza, Gheologhiceskii jurnal, T 33, 6, 11-17. [Upper Quaternary sediments absolute radiocarbon age data from the Azovian - Black Sea Basin]. Journal of Geology,T 33, 6, 11-17.

Continuous sea-level reconstructions beyond the Pleistocene: improving the Mediterranean sea-level method

NASA Astrophysics Data System (ADS)

Grant, K.; Rohling, E. J.; Amies, J.

2017-12-01

Sea-level (SL) reconstructions over glacial-interglacial timeframes are critical for understanding the equilibrium response of ice sheets to sustained warming. In particular, continuous and high-resolution SL records are essential for accurately quantifying `natural' rates of SL rise. Global SL changes are well-constrained since the last glacial maximum ( 20,000 years ago, ky) by radiometrically-dated corals and paleoshoreline data, and fairly well-constrained over the last glacial cycle ( 150 ky). Prior to that, however, studies of ice-volume:SL relationships tend to rely on benthic δ18O, as geomorphological evidence is far more sparse and less reliably dated. An alternative SL reconstruction method (the `marginal basin' approach) was developed for the Red Sea over 500 ky, and recently attempted for the Mediterranean over 5 My (Rohling et al., 2014, Nature). This method exploits the strong sensitivity of seawater δ18O in these basins to SL changes in the relatively narrow and shallow straits which connect the basins with the open ocean. However, the initial Mediterranean SL method did not resolve sea-level highstands during Northern Hemisphere insolation maxima, when African monsoon run-off - strongly depleted in δ18O - reached the Mediterranean. Here, we present improvements to the `marginal basin' sea-level reconstruction method. These include a new `Med-Red SL stack', which combines new probabilistic Mediterranean and Red Sea sea-level stacks spanning the last 500 ky. We also show how a box model-data comparison of water-column δ18O changes over a monsoon interval allows us to quantify the monsoon versus SL δ18O imprint on Mediterranean foraminiferal carbonate δ18O records. This paves the way for a more accurate and fully continuous SL reconstruction extending back through the Pliocene.

Assessing the Potential for Inland Migration of a Northeastern Salt Marsh

NASA Astrophysics Data System (ADS)

Farron, S.; FitzGerald, D.; Hughes, Z. J.

2017-12-01

It is often assumed that as sea level rises, salt marshes will expand inland. If the slope of the upland is relatively flat and sufficient sediment is available, marshes should be able to spread horizontally and grow vertically in order to maintain their areal extent. However, in cases where marshes are backed by steeper slopes, or sediment supply is limited, rising sea level will produce minimal gains along the landward edge insufficient to offset potential losses along the seaward edge. This study uses future sea level rise scenarios to project areal losses for the Great Marsh in Massachusetts, the largest continuous salt marsh in New England. Land area covered by salt marsh is defined by surface elevation. Annual sediment input to the system is estimated based on the areal extent of high and low marsh, historical accretion rates for each, and known organic/inorganic ratios. Unlike other studies, sediment availability is considered to be finite, and future accretion rates are limited based on the assumption that the system is presently receiving the maximum sediment input available. The Great Marsh is dominated by high marsh; as sea level rises, it will convert to low marsh, vastly altering the ecological and sedimentological dynamics of the system. If it is assumed that former high marsh areas will build vertically at the increased rate associated with low marsh, then much of the total marsh area will be maintained. However, this may be an unrealistic assumption due to the low levels of suspended sediment within the Great Marsh system. Modeling the evolution of the Great Marsh by assuming that the current accretion rate is the maximum possible for this system reveals much greater losses than models assuming an unlimited sediment supply would predict (17% less marsh by 2115). In addition, uplands surrounding the Great Marsh have been shaped by glaciation, leaving numerous drumlins and other glacial landforms. Compared to the flat backbarrier, the surrounding hills offer little opportunity for expansion. Modeling results suggest that sea level rise over the next century will convert 12 km2 of marsh to open water, but only 9 km2 of new marsh will be formed through uplands inundation and sedimentation. These findings suggest that sea level rise presents a particular threat to the Great Marsh, and marshes like it.

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.

14 CFR 23.65 - Climb: All engines operating.

Code of Federal Regulations, 2010 CFR

2010-01-01

...-powered airplane of 6,000 pounds or less maximum weight must have a steady climb gradient at sea level of... gradient of climb after takeoff of at least 4 percent with (1) Take off power on each engine; (2) The...

Informatics and computational method for inundation and land use study in Arctic Sea eastern Siberia, Russia

NASA Astrophysics Data System (ADS)

Boori, Mukesh Singh; Choudhary, Komal; Kupriyanov, Alexander; Sugimoto, Atsuko

2016-11-01

Eastern Siberia, Russia is physically and socio-economically vulnerable to accelerated Arctic sea level rise due to low topography, high ecological value, harsh climatic conditions, erosion and flooding of coastal area and destruction of harbor constructions and natural coastal hazards. A 1 to 10m inundation land loss scenarios for surface water and sea level rise (SLR) were developed using digital elevation models of study site topography through remote sensing and GIS techniques by ASTER GDEM and Landsat OLI data. Results indicate that 10.82% (8072.70km2) and 29.73% (22181.19km2) of the area will be lost by flooding at minimum and maximum inundation levels, respectively. The most severely impacted sectors are expected to be the vegetation, wetland and the natural ecosystem. Improved understanding of the extent and response of SLR will help in preparing for mitigation and adaptation.

Spatiotemporal fusion of multiple-satellite aerosol optical depth (AOD) products using Bayesian maximum entropy method

NASA Astrophysics Data System (ADS)

Tang, Qingxin; Bo, Yanchen; Zhu, Yuxin

2016-04-01

Merging multisensor aerosol optical depth (AOD) products is an effective way to produce more spatiotemporally complete and accurate AOD products. A spatiotemporal statistical data fusion framework based on a Bayesian maximum entropy (BME) method was developed for merging satellite AOD products in East Asia. The advantages of the presented merging framework are that it not only utilizes the spatiotemporal autocorrelations but also explicitly incorporates the uncertainties of the AOD products being merged. The satellite AOD products used for merging are the Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 5.1 Level-2 AOD products (MOD04_L2) and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Deep Blue Level 2 AOD products (SWDB_L2). The results show that the average completeness of the merged AOD data is 95.2%,which is significantly superior to the completeness of MOD04_L2 (22.9%) and SWDB_L2 (20.2%). By comparing the merged AOD to the Aerosol Robotic Network AOD records, the results show that the correlation coefficient (0.75), root-mean-square error (0.29), and mean bias (0.068) of the merged AOD are close to those (the correlation coefficient (0.82), root-mean-square error (0.19), and mean bias (0.059)) of the MODIS AOD. In the regions where both MODIS and SeaWiFS have valid observations, the accuracy of the merged AOD is higher than those of MODIS and SeaWiFS AODs. Even in regions where both MODIS and SeaWiFS AODs are missing, the accuracy of the merged AOD is also close to the accuracy of the regions where both MODIS and SeaWiFS have valid observations.

Tsunami Risk Assessment Modelling in Chabahar Port, Iran

NASA Astrophysics Data System (ADS)

Delavar, M. R.; Mohammadi, H.; Sharifi, M. A.; Pirooz, M. D.

2017-09-01

The well-known historical tsunami in the Makran Subduction Zone (MSZ) region was generated by the earthquake of November 28, 1945 in Makran Coast in the North of Oman Sea. This destructive tsunami killed over 4,000 people in Southern Pakistan and India, caused great loss of life and devastation along the coasts of Western India, Iran and Oman. According to the report of "Remembering the 1945 Makran Tsunami", compiled by the Intergovernmental Oceanographic Commission (UNESCO/IOC), the maximum inundation of Chabahar port was 367 m toward the dry land, which had a height of 3.6 meters from the sea level. In addition, the maximum amount of inundation at Pasni (Pakistan) reached to 3 km from the coastline. For the two beaches of Gujarat (India) and Oman the maximum run-up height was 3 m from the sea level. In this paper, we first use Makran 1945 seismic parameters to simulate the tsunami in generation, propagation and inundation phases. The effect of tsunami on Chabahar port is simulated using the ComMIT model which is based on the Method of Splitting Tsunami (MOST). In this process the results are compared with the documented eyewitnesses and some reports from researchers for calibration and validation of the result. Next we have used the model to perform risk assessment for Chabahar port in the south of Iran with the worst case scenario of the tsunami. The simulated results showed that the tsunami waves will reach Chabahar coastline 11 minutes after generation and 9 minutes later, over 9.4 Km2 of the dry land will be flooded with maximum wave amplitude reaching up to 30 meters.

46 CFR 113.50-15 - Loudspeakers.

Code of Federal Regulations, 2010 CFR

2010-10-01

... loudspeakers must be watertight and suitably protected from the effects of the wind and seas. (c) There must be... emergency announcements must be— (1) In interior spaces, 75 dB(A) or, if the background noise level exceeds 75 dB(A), then at least 20 dB(A) above maximum background noise level; and (2) In exterior spaces, 80...

Radioactive pollution of the waters of the baltic sea during 1986

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

Lazarev, L.N.; Kuznetsov, Yu.V.; Gedeonov, L.I.

Results are presented from an investigation of radioactive pollution of the waters of the Baltic Sea during 1986. Inhomogeneities in the pollution of this area of water, due to varying density of atmospheric radioactive fallout, are detected. It is found that among the radionuclides entering the surface of the Baltic Sea in 1986 as a result of atmospheric transport, the main one in terms of radiation dose is cesium-137. Comparisons are made of the level of cesium-137 content in the waters of the Baltic Sea in 1986 and in preceding years. It is noted that even in the most pollutedmore » regions of the sea the cesium-137 content was 500 times less than the maximum allowable concentration (MAC) in the USSR for drinking water. The first results of the determination of plutonium-239 and 240 in the Baltic Sea are presented.« less

Transmission dynamics of parasitic sea lice from farm to wild salmon.

PubMed

Krkosek, Martin; Lewis, Mark A; Volpe, John P

2005-04-07

Marine salmon farming has been correlated with parasitic sea lice infestations and concurrent declines of wild salmonids. Here, we report a quantitative analysis of how a single salmon farm altered the natural transmission dynamics of sea lice to juvenile Pacific salmon. We studied infections of sea lice (Lepeophtheirus salmonis and Caligus clemensi) on juvenile pink salmon (Oncorhynchus gorbuscha) and chum salmon (Oncorhynchus keta) as they passed an isolated salmon farm during their seaward migration down two long and narrow corridors. Our calculations suggest the infection pressure imposed by the farm was four orders of magnitude greater than ambient levels, resulting in a maximum infection pressure near the farm that was 73 times greater than ambient levels and exceeded ambient levels for 30 km along the two wild salmon migration corridors. The farm-produced cohort of lice parasitizing the wild juvenile hosts reached reproductive maturity and produced a second generation of lice that re-infected the juvenile salmon. This raises the infection pressure from the farm by an additional order of magnitude, with a composite infection pressure that exceeds ambient levels for 75 km of the two migration routes. Amplified sea lice infestations due to salmon farms are a potential limiting factor to wild salmonid conservation.

Transmission dynamics of parasitic sea lice from farm to wild salmon

PubMed Central

Krkošek, Martin; Lewis, Mark A; Volpe, John P

2005-01-01

Marine salmon farming has been correlated with parasitic sea lice infestations and concurrent declines of wild salmonids. Here, we report a quantitative analysis of how a single salmon farm altered the natural transmission dynamics of sea lice to juvenile Pacific salmon. We studied infections of sea lice (Lepeophtheirus salmonis and Caligus clemensi ) on juvenile pink salmon (Oncorhynchus gorbuscha) and chum salmon (Oncorhynchus keta) as they passed an isolated salmon farm during their seaward migration down two long and narrow corridors. Our calculations suggest the infection pressure imposed by the farm was four orders of magnitude greater than ambient levels, resulting in a maximum infection pressure near the farm that was 73 times greater than ambient levels and exceeded ambient levels for 30 km along the two wild salmon migration corridors. The farm-produced cohort of lice parasitizing the wild juvenile hosts reached reproductive maturity and produced a second generation of lice that re-infected the juvenile salmon. This raises the infection pressure from the farm by an additional order of magnitude, with a composite infection pressure that exceeds ambient levels for 75 km of the two migration routes. Amplified sea lice infestations due to salmon farms are a potential limiting factor to wild salmonid conservation. PMID:15870031

Tropical cyclone induced asymmetry of sea level surge and fall and its presentation in a storm surge model with parametric wind fields

NASA Astrophysics Data System (ADS)

Peng, Machuan; Xie, Lian; Pietrafesa, Leonard J.

The asymmetry of tropical cyclone induced maximum coastal sea level rise (positive surge) and fall (negative surge) is studied using a three-dimensional storm surge model. It is found that the negative surge induced by offshore winds is more sensitive to wind speed and direction changes than the positive surge by onshore winds. As a result, negative surge is inherently more difficult to forecast than positive surge since there is uncertainty in tropical storm wind forecasts. The asymmetry of negative and positive surge under parametric wind forcing is more apparent in shallow water regions. For tropical cyclones with fixed central pressure, the surge asymmetry increases with decreasing storm translation speed. For those with the same translation speed, a weaker tropical cyclone is expected to gain a higher AI (asymmetry index) value though its induced maximum surge and fall are smaller. With fixed RMW (radius of maximum wind), the relationship between central pressure and AI is heterogeneous and depends on the value of RMW. Tropical cyclone's wind inflow angle can also affect surge asymmetry. A set of idealized cases as well as two historic tropical cyclones are used to illustrate the surge asymmetry.

Deposit from a giant wave on the Island of Lanai, Hawaii

USGS Publications Warehouse

Moore, J.G.; Moore, G.W.

1984-01-01

Limestone-bearing gravel, the newly named Hulopoe Gravel, blankets the coastal slopes on Lanai. The deposit, which reaches a maximum altitude of 326 meters, formerly was believed to have been deposited along several different ancient marine strandlines, but dated submerged coral reefs and tide-gauge measurements indicate that the southeastern Hawaiian Islands sink so fast that former worldwide high stands of the sea now lie beneath local sea level. Evidence indicates that the Hulopoe Gravel and similar deposits on nearby islands were deposited during the Pleistocene by a giant wave generated by a submarine landslide on a sea scarp south of Lanai.

Dynamic Singularity Spectrum Distribution of Sea Clutter

NASA Astrophysics Data System (ADS)

Xiong, Gang; Yu, Wenxian; Zhang, Shuning

2015-12-01

The fractal and multifractal theory have provided new approaches for radar signal processing and target-detecting under the background of ocean. However, the related research mainly focuses on fractal dimension or multifractal spectrum (MFS) of sea clutter. In this paper, a new dynamic singularity analysis method of sea clutter using MFS distribution is developed, based on moving detrending analysis (DMA-MFSD). Theoretically, we introduce the time information by using cyclic auto-correlation of sea clutter. For transient correlation series, the instantaneous singularity spectrum based on multifractal detrending moving analysis (MF-DMA) algorithm is calculated, and the dynamic singularity spectrum distribution of sea clutter is acquired. In addition, we analyze the time-varying singularity exponent ranges and maximum position function in DMA-MFSD of sea clutter. For the real sea clutter data, we analyze the dynamic singularity spectrum distribution of real sea clutter in level III sea state, and conclude that the radar sea clutter has the non-stationary and time-varying scale characteristic and represents the time-varying singularity spectrum distribution based on the proposed DMA-MFSD method. The DMA-MFSD will also provide reference for nonlinear dynamics and multifractal signal processing.

Survey of patterns, levels, and trends of perfluorinated compounds in aquatic organisms and bird eggs from representative German ecosystems.

PubMed

Rüdel, Heinz; Müller, Josef; Jürling, Heinrich; Bartel-Steinbach, Martina; Koschorreck, Jan

2011-11-01

Samples from the German Environmental Specimen Bank (ESB) covering particularly the years 1994-1996, 2000-2002, and 2006-2009 were analyzed for perfluorinated compounds (PFC; mainly C4-C13 carboxylic and sulfonic acids) to gain an overview on current PFC levels and patterns in marine, limnetic, and terrestrial biota; to assess their concentrations in different trophic levels; and to investigate whether risk management measures for PFC are successful. Specimens, either standardized annual pooled samples (blue mussels, eelpout liver, bream liver, pigeon eggs) or individual single samples (cormorant eggs, rook eggs), were collected for the German ESB program from representative sampling sites according to documented guidelines. After appropriate extraction, PFC were quantified under ISO/IEC 17025 accreditation by HPLC/MS-MS with isotopically labeled internal standards. Limits of quantification (LOQs) were 0.2-0.5 ng/g. Data are reported on a wet weight basis. In most samples the predominant PFC was perfluorooctane sulfonic acid (PFOS). However, in marine mussels from North and Baltic Seas, PFOS levels were mostly below the LOQ, but low residues of PFOS amide were found which declined in recent years. Livers of eelpout showed maximum concentrations of 15-25 ng/g PFOS in the period 2000-2002 and low amounts of perfluoropentanoate in all years. Beside PFOS (median 48 ng/g) several PFC could be determined in cormorant eggs sampled in 2009 from a Baltic Sea site. For a freshwater ecosystem, current PFC burdens for cormorant eggs were even higher (median 400 ng/g PFOS). Livers of bream from rivers showed concentrations of 130-260 ng/g PFOS, but for bream from a reference lake levels were only about 6 ng/g. In contrast to cormorants, eggs of rook and feral pigeon from terrestrial ecosystems displayed only low PFC burdens (up to 6 ng/g PFOS). Generally, PFC levels were lower in marine than in freshwater biota. PFC burdens were higher in biota from the ESB-North Sea sites than in Baltic Sea organisms. Levels of PFC were quite high especially in top predators of both limnetic and marine ecosystems. Only low PFC levels were detected in eggs of terrestrial birds. A decrease of PFOS levels from maximum values around the year 2000 observed at least in North Sea biota may be a result of a production cease and shifts in marketing pattern.

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.

Gravitational failure of sea cliffs in weakly lithified sediment

USGS Publications Warehouse

Hampton, M.A.

2002-01-01

Gravitational failure of sea cliffs eroded into weakly lithified sediment at several sites in California involves episodic stress-release fracturing and cantilevered block falls. The principal variables that influence the gravitational stability are tensional stresses generated during the release of horizontal confining stress and weakening of the sediment with increased saturation levels. Individual failures typically comprise less than a cubic meter of sediment, but large areas of a cliff face can be affected by sustained instability over a period of several days. Typically, only the outer meter or so of sediment is removed during a failure episode. In-place sediment saturation levels vary over time and space, generally being higher during the rainy season but moderate to high year-round. Laboratory direct-shear tests show that sediment cohesion decreases abruptly with increasing saturation level; the decrease is similar for all tested sediment if the cohesion is normalized by the maximum, dry-sediment cohesion. Large failures that extend over most or all of the height of the sea cliff are uncommon, but a few large wedge-shaped failures sometimes occur, as does separation of large blocks at sea cliff-gully intersections.

Simulation of coastal floodings during a typhoon event with the consideration of future sea-level rises.

NASA Astrophysics Data System (ADS)

Shu-Huei, Jhang; Chih-Chung, Wen; Dong-Jiing, Doong; Cheng-Han, Tsai

2017-04-01

Taiwan is an Island in the western Pacific Ocean and experienced more than 3 typhoons in a year. Typhoons bring intense rainfall, high waves, and storm surges, which often resulted in coastal flooding. The flooding can be aggravated by the sea level rise due to the global warming, which may subject Taiwan's coastal areas to more serious damage in the future than present. The objectives of this study are to investigate the flooding caused by typhoons in the Annan District, Tainan, a city on the southwest coast of Taiwan by numerical simulations, considering the effects of sea-level rises according to the level suggested by the 5th Assessment Report of IPCC (Intergovernmental Panel on Climate Change) for 2050 and 2100, respectively. The simulations were carried out by using MIKE21 HD (a hydrodynamic model) and MIKE21 SW (a spectral wave model). In our simulation, we used an intense typhoon, named Soudelor, as our base typhoon, which made its landfall on the east coast of Taiwan in the summer of 2015, traveled through the width of the island, and exited the island to the north of Tainan. The reasons we pick this typhoon are that it passed near our objective area, wind field data for this typhoon are available, and we have well documented coastal wave and water level measurements during the passage of Typhoon Soudelor. We firstly used ECMWF (European Centre for Medium-Range Weather Forecasts) wind field data to reconstruct typhoon waves and storm surges for this typhoon by using coupled MIKE21 SW and MIKE21 HD in a regional model. The resultant simulated wave height and sea-level height matched satisfactorily with the measured data. The wave height and storm surge calculated by the regional model provided the boundary conditions for our fine-grid domain. Then different sea-level rises suggested by the IPCC were incorporated into the fine-grid model. Since river discharge due to intense rainfall has also to be considered for coastal flooding, our fine-grid models encompass the estuary of River Yanshui, and measured upstream river discharges were used to simulate the interactions among tide, current, and wave near the estuary of Yanshui River. Our preliminary results showed that with only the effect of rainwater discharge, the maximum surface level of the river during the storm near the estuary was 1.4 m, which is not higher than the river embankments. With the storm surge, the river level at the same location was 2.2 m. With the storm surge and sea-level rise, the maximum river levels near the estuary were 3.6 m and 3.9 m for 2050 and 2100 scenarios, respective. These levels were higher than the embankment height of 3 m. This showed that due to higher sea-level, the area near the estuary will be flooded.

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.

Pliocene shorelines and the deformation of passive margins.

NASA Astrophysics Data System (ADS)

Rovere, Alessio; Raymo, Maureen; Austermann, Jacqueline; Mitrovica, Jerry; Janßen, Alexander

2016-04-01

Characteristic geomorphology described from three Pliocene scarps in Rovere et al. [2014] was used to guide a global search for additional Pliocene age scarps that could be used to document former Pliocene shoreline locations. Each of the Rovere et al. [2014] paleo-shorelines was measured at the scarp toe abutting a flat coastal plain. In this study, nine additional such scarp-toe paleo-shorelines were identified. Each of these scarps has been independently dated to the Plio-Pleistocene; however, they were never unified by a single formation mechanism. Even when corrected for Glacial Isostatic Adjustment post-depositional effects, Post-Pliocene deformation of the inferred shorelines precludes a direct assessment of maximum Pliocene sea level height at the scarp toes. However, careful interpretation of the processes at the inferred paleo-shoreline suggests specific amplitudes of dynamic topography at each location, which could lead to a corrected maximum sea level height and provide a target dataset with which to compare dynamic topography model output.

Calcareous microfossil-based orbital cyclostratigraphy in the Arctic Ocean

USGS Publications Warehouse

Marzen, Rachel; DeNinno, Lauren H.; Cronin, Thomas M.

2016-01-01

Microfaunal and geochemical proxies from marine sediment records from central Arctic Ocean (CAO) submarine ridges suggest a close relationship over the last 550 thousand years (kyr) between orbital-scale climatic oscillations, sea-ice cover, marine biological productivity and other parameters. Multiple paleoclimate proxies record glacial to interglacial cycles. To understand the climate-cryosphere-productivity relationship, we examined the cyclostratigraphy of calcareous microfossils and constructed a composite Arctic Paleoclimate Index (API) "stack" from benthic foraminiferal and ostracode density from 14 sediment cores. Following the hypothesis that API is driven mainly by changes in sea-ice related productivity, the API stack shows the Arctic experienced a series of highly productive interglacials and interstadials every ∼20 kyr. These periods signify minimal ice shelf and sea-ice cover and maximum marine productivity. Rapid transitions in productivity are seen during shifts from interglacial to glacial climate states. Discrepancies between the Arctic API curves and various global climatic, sea-level and ice-volume curves suggest abrupt growth and decay of Arctic ice shelves related to climatic and sea level oscillations.

Asynchronous behavior of the Antarctic Ice Sheet and local glaciers during and since Termination 1, Salmon Valley, Antarctica

NASA Astrophysics Data System (ADS)

Jackson, Margaret S.; Hall, Brenda L.; Denton, George H.

2018-01-01

The stability of the Antarctic Ice Sheet under future warming remains an open question with broad implications for sea-level prediction and adaptation. In particular, knowledge of whether the ice sheet has the capacity for rapid drawdown or collapse, or whether it can remain stable during periods of warming, is essential for predicting its future behavior. Here we use 55 radiocarbon dates, coupled with geomorphologic mapping, to reconstruct the timing of changes in ice extent and elevation during the last ice-age termination in Salmon Valley, adjacent to McMurdo Sound in the western Ross Sea Embayment. Results indicate that a grounded ice sheet in the Ross Sea Embayment achieved its maximum elevation and extent along the headlands of Salmon Valley at ∼18,000 yr BP, during a period of increasing temperatures and accumulation over the Antarctic continent. This ice remained at or near its maximum on the headlands near the valley mouth until after ∼14,000 yr BP. Removal of grounded Ross Sea ice from Salmon Valley was complete shortly after ∼7900 yr BP, indicating that the grounding line had retreated through southern McMurdo Sound by that time. We suggest the primary driver of Ross Sea ice removal from McMurdo Sound was marine-based, either through basal melting or calving due to sea-level rise. When combined with regional data, the Salmon Valley record suggests that this sector of the Antarctic Ice Sheet did not contribute in a significant way to deglacial meltwater pulses, such as meltwater pulse 1a. In contrast to the Ross Sea ice, our work also shows that local, independent alpine glaciers in Salmon Valley have advanced through the Holocene. Land-terminating glaciers such as these elsewhere in the region show a similar pattern, and may reflect the continued influence of increased accumulation following the termination of the last ice age.

76 FR 47493 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands King and...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-05

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76 FR 25295 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands King and...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-04

... crab rebuilding plan to define the stock as rebuilt the first year the stock biomass is above the level... stock assessment model to estimate the biomass level and fishing rate necessary to achieve maximum sustainable yield. Tier 4 stocks have a stock assessment model that estimates biomass using the historical...

Deglacial sea level history of the East Siberian Sea and Chukchi Sea margins

USGS Publications Warehouse

Cronin, Thomas M.; O'Regan, Matt; Pearce, Christof; Gemery, Laura; Toomey, Michael; Semiletov, Igor

2017-01-01

Deglacial (12.8–10.7 ka) sea level history on the East Siberian continental shelf and upper continental slope was reconstructed using new geophysical records and sediment cores taken during Leg 2 of the 2014 SWERUS-C3 expedition. The focus of this study is two cores from Herald Canyon, piston core SWERUS-L2-4-PC1 (4-PC1) and multicore SWERUS-L2-4-MC1 (4-MC1), and a gravity core from an East Siberian Sea transect, SWERUS-L2-20-GC1 (20-GC1). Cores 4-PC1 and 20-GC were taken at 120 and 115 m of modern water depth, respectively, only a few meters above the global last glacial maximum (LGM;  ∼  24 kiloannum or ka) minimum sea level of  ∼  125–130 meters below sea level (m b.s.l.). Using calibrated radiocarbon ages mainly on molluscs for chronology and the ecology of benthic foraminifera and ostracode species to estimate paleodepths, the data reveal a dominance of river-proximal species during the early part of the Younger Dryas event (YD, Greenland Stadial GS-1) followed by a rise in river-intermediate species in the late Younger Dryas or the early Holocene (Preboreal) period. A rapid relative sea level rise beginning at roughly 11.4 to 10.8 ka ( ∼  400 cm of core depth) is indicated by a sharp faunal change and unconformity or condensed zone of sedimentation. Regional sea level at this time was about 108 m b.s.l. at the 4-PC1 site and 102 m b.s.l. at 20-GC1. Regional sea level near the end of the YD was up to 42–47 m lower than predicted by geophysical models corrected for glacio-isostatic adjustment. This discrepancy could be explained by delayed isostatic adjustment caused by a greater volume and/or geographical extent of glacial-age land ice and/or ice shelves in the western Arctic Ocean and adjacent Siberian land areas.

Deglacial sea level history of the East Siberian Sea and Chukchi Sea margins

NASA Astrophysics Data System (ADS)

Cronin, Thomas M.; O'Regan, Matt; Pearce, Christof; Gemery, Laura; Toomey, Michael; Semiletov, Igor; Jakobsson, Martin

2017-09-01

Deglacial (12.8-10.7 ka) sea level history on the East Siberian continental shelf and upper continental slope was reconstructed using new geophysical records and sediment cores taken during Leg 2 of the 2014 SWERUS-C3 expedition. The focus of this study is two cores from Herald Canyon, piston core SWERUS-L2-4-PC1 (4-PC1) and multicore SWERUS-L2-4-MC1 (4-MC1), and a gravity core from an East Siberian Sea transect, SWERUS-L2-20-GC1 (20-GC1). Cores 4-PC1 and 20-GC were taken at 120 and 115 m of modern water depth, respectively, only a few meters above the global last glacial maximum (LGM; ˜ 24 kiloannum or ka) minimum sea level of ˜ 125-130 meters below sea level (m b.s.l.). Using calibrated radiocarbon ages mainly on molluscs for chronology and the ecology of benthic foraminifera and ostracode species to estimate paleodepths, the data reveal a dominance of river-proximal species during the early part of the Younger Dryas event (YD, Greenland Stadial GS-1) followed by a rise in river-intermediate species in the late Younger Dryas or the early Holocene (Preboreal) period. A rapid relative sea level rise beginning at roughly 11.4 to 10.8 ka ( ˜ 400 cm of core depth) is indicated by a sharp faunal change and unconformity or condensed zone of sedimentation. Regional sea level at this time was about 108 m b.s.l. at the 4-PC1 site and 102 m b.s.l. at 20-GC1. Regional sea level near the end of the YD was up to 42-47 m lower than predicted by geophysical models corrected for glacio-isostatic adjustment. This discrepancy could be explained by delayed isostatic adjustment caused by a greater volume and/or geographical extent of glacial-age land ice and/or ice shelves in the western Arctic Ocean and adjacent Siberian land areas.

The exposure of Sydney (Australia) to earthquake-generated tsunamis, storms and sea level rise: a probabilistic multi-hazard approach

PubMed Central

Dall'Osso, F.; Dominey-Howes, D.; Moore, C.; Summerhayes, S.; Withycombe, G.

2014-01-01

Approximately 85% of Australia's population live along the coastal fringe, an area with high exposure to extreme inundations such as tsunamis. However, to date, no Probabilistic Tsunami Hazard Assessments (PTHA) that include inundation have been published for Australia. This limits the development of appropriate risk reduction measures by decision and policy makers. We describe our PTHA undertaken for the Sydney metropolitan area. Using the NOAA NCTR model MOST (Method for Splitting Tsunamis), we simulate 36 earthquake-generated tsunamis with annual probabilities of 1:100, 1:1,000 and 1:10,000, occurring under present and future predicted sea level conditions. For each tsunami scenario we generate a high-resolution inundation map of the maximum water level and flow velocity, and we calculate the exposure of buildings and critical infrastructure. Results indicate that exposure to earthquake-generated tsunamis is relatively low for present events, but increases significantly with higher sea level conditions. The probabilistic approach allowed us to undertake a comparison with an existing storm surge hazard assessment. Interestingly, the exposure to all the simulated tsunamis is significantly lower than that for the 1:100 storm surge scenarios, under the same initial sea level conditions. The results have significant implications for multi-risk and emergency management in Sydney. PMID:25492514

The exposure of Sydney (Australia) to earthquake-generated tsunamis, storms and sea level rise: a probabilistic multi-hazard approach.

PubMed

Dall'Osso, F; Dominey-Howes, D; Moore, C; Summerhayes, S; Withycombe, G

2014-12-10

Approximately 85% of Australia's population live along the coastal fringe, an area with high exposure to extreme inundations such as tsunamis. However, to date, no Probabilistic Tsunami Hazard Assessments (PTHA) that include inundation have been published for Australia. This limits the development of appropriate risk reduction measures by decision and policy makers. We describe our PTHA undertaken for the Sydney metropolitan area. Using the NOAA NCTR model MOST (Method for Splitting Tsunamis), we simulate 36 earthquake-generated tsunamis with annual probabilities of 1:100, 1:1,000 and 1:10,000, occurring under present and future predicted sea level conditions. For each tsunami scenario we generate a high-resolution inundation map of the maximum water level and flow velocity, and we calculate the exposure of buildings and critical infrastructure. Results indicate that exposure to earthquake-generated tsunamis is relatively low for present events, but increases significantly with higher sea level conditions. The probabilistic approach allowed us to undertake a comparison with an existing storm surge hazard assessment. Interestingly, the exposure to all the simulated tsunamis is significantly lower than that for the 1:100 storm surge scenarios, under the same initial sea level conditions. The results have significant implications for multi-risk and emergency management in Sydney.

Do fattening process and biological parameters affect the accumulation of metals in Atlantic bluefin tuna?

PubMed

Milatou, Niki; Dassenakis, Manos; Megalofonou, Persefoni

2015-01-01

The objective of this study was to determine the current levels of heavy metals and trace elements in Atlantic bluefin tuna muscle tissues and how they are influenced by the fattening process and various life history parameters to ascertain whether the concentrations in muscle tissue exceed the maximum levels defined by the European Commission Decision and to evaluate the health risk posed by fish consumption. A total of 20 bluefin tuna reared in sea cages, ranging from 160 to 295 cm in length and from 80 to 540 kg in weight, were sampled from a bluefin tuna farm in the Ionian Sea. The condition factor K of each specimen was calculated and their age was estimated. Heavy metal and trace element (Hg, Zn, Fe and Cu) contents were determined in muscle tissue using cold vapour atomic absorption spectrometry and flame and graphite furnace atomic absorption spectrometry. The total Hg concentrations ranged from 0.28 to 1.28 mg kg(-1) w/w, Zn from 5.81 to 76.37 mg kg(-1) w/w, Fe from 12.14 to 39.58 mg kg(-1) w/w, and Cu from 0.36 to 0.94 mg kg(-1) w/w. Only 5% of the muscle samples of tuna contained Hg above the maximum level laid down by the European Commission Decision. Moreover, 15% of the muscle samples contained Zn above the maximum level, while Fe and Cu concentrations were within the acceptable tolerable guideline values. The reared bluefin tuna had lower concentrations of Hg than the wild ones from the Mediterranean Sea. Hg and Fe concentrations showed a positive relationship with size and age of bluefin tuna, whereas negative relationships were found for the concentrations of Zn and Cu. The estimated dietary intake values of the analysed metals were mostly below the derived guidelines.

An Assessment of SeaWiFS and MODIS Ocean Coverage

NASA Technical Reports Server (NTRS)

Woodward, Robert H.; Gregg, Watson W.

1998-01-01

Ocean coverages of SeaWiFS and MODIS were assessed for three seasons by considering monthly mean values of surface winds speeds and cloud cover. Mean and maximum coverages combined SeaWiFS and MODIS by considering combined coverages for ten-degree increments of the MODIS orbital mean anomaly. From this analysis the mean and maximum combined coverages for SeaWiFS and MODIS were determined for one and four-day periods for spring, summer, and winter seasons. Loss of coverage due to Sun glint and cloud cover were identified for both the individual and combined cases. Our analyses indicate that MODIS will enhance ocean coverage for all three seasons examined. ne combined SeaWiFS/MODIS show an increase of coverage of 42.2% to 48.7% over SeaWiFS alone for the three seasons studied; the increase in maximum one day coverage ranges from 47.5% to 52.0%. The increase in four-day coverage for the combined case ranged from 31.0% to 35.8% for mean coverage and 33.1 % to 39.2% for maximum coverage. We computed meridional distributions of coverages by binning the data into five-degree latitude bands. Our analysis shows a strong seasonal dependence of coverage. In general the meridional analysis indicates that increase in coverages for SeaWiFS/MODIS over SeaWiFS alone are greatest near the solar declination.

Mercury concentrations in lean fish from the Western Mediterranean Sea: Dietary exposure and risk assessment in the population of the Balearic Islands.

PubMed

Llull, Rosa Maria; Garí, Mercè; Canals, Miquel; Rey-Maquieira, Teresa; Grimalt, Joan O

2017-10-01

The present study reports total mercury (THg) and methylmercury (MeHg) concentrations in 32 different lean fish species from the Western Mediterranean Sea, with a special focus on the Balearic Islands. The concentrations of THg ranged between 0.05mg/kg ww and 3.1mg/kg ww (mean 0.41mg/kg ww). A considerable number of the most frequently fish species consumed by the Spanish population exceed the maximum levels proposed by the European legislation when they originate from the Mediterranean Sea, such as dusky grouper (100% of the examined specimens), common dentex (65%), conger (45%), common sole (38%), hake (26%) and angler (15%), among others. The estimated weekly intakes (EWI) in children (7-12 years of age) and adults from the Spanish population (2.7µg/kg bw and 2.1µg/kg bw, respectively) for population only consuming Mediterranean fish were below the provisional tolerable weekly intake (PTWI) of THg established by EFSA in 2012, 4µg/kg bw. However, the equivalent estimations for methylmercury, involving PTWI of 1.3µg/kg bw, were two times higher in children and above 50% in adults. For hake, sole, angler and dusky grouper, the most frequently consumed fish, the estimated weekly intakes in both children and adults were below the maximum levels accepted. These intakes correspond to maximum potential estimations because fish from non-Mediterranean origin is often consumed by the Spanish population including the one from the Balearic Islands. Copyright © 2017 Elsevier Inc. All rights reserved.

Constraints on evaporation and dilution of terminal, hypersaline lakes under negative water balance: The Dead Sea, Israel

NASA Astrophysics Data System (ADS)

Zilberman, Tami; Gavrieli, Ittai; Yechieli, Yoseph; Gertman, Isaac; Katz, Amitai

2017-11-01

The response of hypersaline terminal lakes to negative water balance was investigated by studying brines evaporating to extreme salinities in sinkholes along the western coast of the Dead Sea and during on-site evaporation experiments of the Dead Sea brine. Density and temperature were determined in the field and all samples were analyzed for their major and a few minor solutes. The activity of H2O (aH2O) in the brines was calculated, and the degree of evaporation (DE) was established using Sr2+as a conservative solute. The relations between density and water activity were obtained by polynomial regression, and the relation between the lake's volume and level was established using Hall's (1996) hypsographic model for the Dead Sea basin. Relating the results to the modern, long-term relative humidity (RH) over the basin shows that (a) The lowermost attainable level of a terminal lake undergoing evaporation with no inflow is dictated by the median RH; this level represents equilibrium between the brine's aH2O and RH; (b) Small, saline water bodies with high surface to volume ratios (A/V), such as the hypersaline brines in the sinkholes, are very sensitive to short term changes in RH; in these, the brines' aH2O closely follows the seasonal changes; (c) the level decline of the Dead Sea due to evaporation under present climatic conditions and assuming no inflow to the lake may continue down to 516-537 m below mean sea level (bmsl), corresponding to a water activity range of 0.46-0.39 in its brine, in equilibrium with the overlying relative air humidity; this suggests that the lake level cannot drop more than ∼100 m from its present level; and (d) The maximum RH values that existed over the precursor lake of the Dead Sea (Lake Lisan) during geologically reconstructed minima levels can be similarly calculated.

Spatial variability in the trends in extreme storm surges and weekly-scale high water levels in the eastern Baltic Sea

NASA Astrophysics Data System (ADS)

Soomere, Tarmo; Pindsoo, Katri

2016-03-01

We address the possibilities of a separation of the overall increasing trend in maximum water levels of semi-enclosed water bodies into associated trends in the heights of local storm surges and basin-scale components of the water level based on recorded and modelled local water level time series. The test area is the Baltic Sea. Sequences of strong storms may substantially increase its water volume and raise the average sea level by almost 1 m for a few weeks. Such events are singled out from the water level time series using a weekly-scale average. The trends in the annual maxima of the weekly average have an almost constant value along the entire eastern Baltic Sea coast for averaging intervals longer than 4 days. Their slopes are ~4 cm/decade for 8-day running average and decrease with an increase of the averaging interval. The trends for maxima of local storm surge heights represent almost the entire spatial variability in the water level maxima. Their slopes vary from almost zero for the open Baltic Proper coast up to 5-7 cm/decade in the eastern Gulf of Finland and Gulf of Riga. This pattern suggests that an increase in wind speed in strong storms is unlikely in this area but storm duration may have increased and wind direction may have rotated.

Expression levels of chaperones influence biotransformation activity of recombinant Escherichia coli expressing Micrococcus luteus alcohol dehydrogenase and Pseudomonas putida Baeyer-Villiger monooxygenase.

PubMed

Baek, A-Hyong; Jeon, Eun-Yeong; Lee, Sun-Mee; Park, Jin-Byung

2015-05-01

We demonstrated for the first time that the archaeal chaperones (i.e., γ-prefoldin and thermosome) can stabilize enzyme activity in vivo. Ricinoleic acid biotransformation activity of recombinant Escherichia coli expressing Micrococcus luteus alcohol dehydrogenase and the Pseudomonas putida KT2440 Baeyer-Villiger monooxygenase improved significantly with co-expression of γ-prefoldin or recombinant themosome originating from the deep-sea hyperthermophile archaea Methanocaldococcus jannaschii. Furthermore, the degree of enhanced activity was dependent on the expression levels of the chaperones. For example, whole-cell biotransformation activity was highest at 12 µmol/g dry cells/min when γ-prefoldin expression level was approximately 46% of the theoretical maximum. This value was approximately two-fold greater than that in E. coli, where the γ-prefoldin expression level was zero or set to the theoretical maximum. Therefore, it was assumed that the expression levels of chaperones must be optimized to achieve maximum biotransformation activity in whole-cell biocatalysts. © 2014 Wiley Periodicals, Inc.

XXI century projections of wind-wave conditions and sea-level rise in the Black sea

NASA Astrophysics Data System (ADS)

Polonsky, A.; Garmashov, A.; Fomin, V.; Valchev, N.; Trifonova, E.

2012-04-01

Projection of regional climate changes for XXI century is one of the priorities of EC environmental programme. Potential worsening of the waves' statistics, sea level rise and extreme surges are the principal negative consequences of the climate change for marine environment. That is why the main purpose of this presentation is to discuss the above issue for the Black sea region (with a strong focus to the south-west subregion because the maximum heights of waves exceeding 10 m occur just here) using output of several global coupled models (GCM) for XXI century, wave simulation, long-term observations of sea level and statistical techniques. First of all we tried to choose the best coupled model (s) simulated the Black sea climate change and variability using the control experiments for 20 century (203). The principal result is as follows. There is not one model which is simulating adequately even one atmospheric parameter for all seasons. Therefore we considered (for the climate projection) different outputs form various models. When it was possible we calculated also the ensemble mean projection for the selected model (s) and emission scenarios. To calculate the wave projection we used the output of SWAN model forced by the GCM wind projection for 2010 to 2100. To estimate the sea level rise in XXI century and future surges statistics we extrapolate the observed sea level rise tendencies, statistical relation between wave heights and sea level and wave scenarios. Results show that in general, the climate change in XXI century doesn't lead to the catastrophic change of the Black sea wind-wave statistics including the extreme waves in the S-W Black sea. The typical atmospheric pattern leading to the intense storm in the S-W Black sea is characterized by the persistent anticyclonic area to the North of the Black sea and cyclonic conditions in the Southern Black sea region. Such pressure pattern causes persistent and strong eastern or north-eastern wind which generates the high waves in the S-E Black sea. The climate projections show that the frequency of such atmospheric pattern will not principally increase. The recent probability of the extreme wave height (exceeding 8 to10 m) in the S-W Black sea (~1 occurrence per 10 years) will not be much worse in XXI century. Similar conclusion is true for the storm surges along the Bulgarian coastline. Expected sea level rise in the Black sea basin for XXI century due to regional climate changes is about 2 mm per year (±50%). However, some Black sea subregions (such as Odessa and Varna bay) are characterized by fivefold sea level rise because of the local land subsidence. So, this geomorphologic effect is the most dangerous local consequence for the sustainable development and management of the coastal zone in such subregions. This study was supported by EC project "THESEUS".

Assessment of salinity intrusion in the James and Chickahominy Rivers as a result of simulated sea-level rise in Chesapeake Bay, East Coast, USA.

PubMed

Rice, Karen C; Hong, Bo; Shen, Jian

2012-11-30

Global sea level is rising, and the relative rate in the Chesapeake Bay region of the East Coast of the United States is greater than the worldwide rate. Sea-level rise can cause saline water to migrate upstream in estuaries and rivers, threatening freshwater habitat and drinking-water supplies. The effects of future sea-level rise on two tributaries of Chesapeake Bay, the James and Chickahominy (CHK) Rivers, were evaluated in order to quantify the salinity change with respect to the magnitude of sea-level rise. Such changes are critical to: 1) local floral and faunal habitats that have limited tolerance ranges to salinity; and 2) a drinking-water supply for the City of Newport News, Virginia. By using the three-dimensional Hydrodynamic-Eutrophication Model (HEM-3D), sea-level rise scenarios of 30, 50, and 100 cm, based on the U.S. Climate Change Science Program for the mid-Atlantic region for the 21st century, were evaluated. The model results indicate that salinity increases in the entire river as sea level rises and that the salinity increase in a dry year is greater than that in a typical year. In the James River, the salinity increase in the middle-to-upper river (from 25 to 50 km upstream of the mouth) is larger than that in the lower and upper parts of the river. The maximum mean salinity increase would be 2 and 4 ppt for a sea-level rise of 50 and 100 cm, respectively. The upstream movement of the 10 ppt isohaline is much larger than the 5 and 20 ppt isohalines. The volume of water with salinity between 10 and 20 ppt would increase greatly if sea level rises 100 cm. In the CHK River, with a sea-level rise of 100 cm, the mean salinity at the drinking-water intake 34 km upstream of the mouth would be about 3 ppt in a typical year and greater than 5 ppt in a dry year, both far in excess of the U.S. Environmental Protection Agency's secondary standard for total dissolved solids for drinking water. At the drinking-water intake, the number of days of salinity greater than 0.1 ppt increases with increasing sea-level rise; during a dry year, 0.1 ppt would be exceeded for more than 100 days with as small a rise as 30 cm. Copyright © 2012 Elsevier Ltd. All rights reserved.

Assessment of salinity intrusion in the James and Chickahominy Rivers as a result of simulated sea-level rise in Chesapeake Bay, East Coast, USA

USGS Publications Warehouse

Rice, Karen; Bo Hong,; Jian Shen,

2012-01-01

Global sea level is rising, and the relative rate in the Chesapeake Bay region of the East Coast of the United States is greater than the worldwide rate. Sea-level rise can cause saline water to migrate upstream in estuaries and rivers, threatening freshwater habitat and drinking-water supplies. The effects of future sea-level rise on two tributaries of Chesapeake Bay, the James and Chickahominy (CHK) Rivers, were evaluated in order to quantify the salinity change with respect to the magnitude of sea-level rise. Such changes are critical to: 1) local floral and faunal habitats that have limited tolerance ranges to salinity; and 2) a drinking-water supply for the City of Newport News, Virginia. By using the three-dimensional Hydrodynamic-Eutrophication Model (HEM-3D), sea-level rise scenarios of 30, 50, and 100 cm, based on the U.S. Climate Change Science Program for the mid-Atlantic region for the 21st century, were evaluated. The model results indicate that salinity increases in the entire river as sea level rises and that the salinity increase in a dry year is greater than that in a typical year. In the James River, the salinity increase in the middle-to-upper river (from 25 to 50 km upstream of the mouth) is larger than that in the lower and upper parts of the river. The maximum mean salinity increase would be 2 and 4 ppt for a sea-level rise of 50 and 100 cm, respectively. The upstream movement of the 10 ppt isohaline is much larger than the 5 and 20 ppt isohalines. The volume of water with salinity between 10 and 20 ppt would increase greatly if sea level rises 100 cm. In the CHK River, with a sea-level rise of 100 cm, the mean salinity at the drinking-water intake 34 km upstream of the mouth would be about 3 ppt in a typical year and greater than 5 ppt in a dry year, both far in excess of the U.S. Environmental Protection Agency's secondary standard for total dissolved solids for drinking water. At the drinking-water intake, the number of days of salinity greater than 0.1 ppt increases with increasing sea-level rise; during a dry year, 0.1 ppt would be exceeded for more than 100 days with as small a rise as 30 cm.

Water level response in back-barrier bays unchanged following Hurricane Sandy

USGS Publications Warehouse

Aretxabaleta, Alfredo L.; Butman, Bradford; Ganju, Neil K.

2014-01-01

On 28–30 October 2012, Hurricane Sandy caused severe flooding along portions of the northeast coast of the United States and cut new inlets across barrier islands in New Jersey and New York. About 30% of the 20 highest daily maximum water levels observed between 2007 and 2013 in Barnegat and Great South Bay occurred in 5 months following Hurricane Sandy. Hurricane Sandy provided a rare opportunity to determine whether extreme events alter systems protected by barrier islands, leaving the mainland more vulnerable to flooding. Comparisons between water levels before and after Hurricane Sandy at bay stations and an offshore station show no significant differences in the transfer of sea level fluctuations from offshore to either bay following Sandy. The post-Hurricane Sandy bay high water levels reflected offshore sea levels caused by winter storms, not by barrier island breaching or geomorphic changes within the bays.

Genetic signature of Last Glacial Maximum regional refugia in a circum-Antarctic sea spider

PubMed Central

Soler-Membrives, Anna; Linse, Katrin; Miller, Karen J.

2017-01-01

The evolutionary history of Antarctic organisms is becoming increasingly important to understand and manage population trajectories under rapid environmental change. The Antarctic sea spider Nymphon australe, with an apparently large population size compared with other sea spider species, is an ideal target to look for molecular signatures of past climatic events. We analysed mitochondrial DNA of specimens collected from the Antarctic continent and two Antarctic islands (AI) to infer past population processes and understand current genetic structure. Demographic history analyses suggest populations survived in refugia during the Last Glacial Maximum. The high genetic diversity found in the Antarctic Peninsula and East Antarctic (EA) seems related to multiple demographic contraction–expansion events associated with deep-sea refugia, while the low genetic diversity in the Weddell Sea points to a more recent expansion from a shelf refugium. We suggest the genetic structure of N. australe from AI reflects recent colonization from the continent. At a local level, EA populations reveal generally low genetic differentiation, geographically and bathymetrically, suggesting limited restrictions to dispersal. Results highlight regional differences in demographic histories and how these relate to the variation in intensity of glaciation–deglaciation events around Antarctica, critical for the study of local evolutionary processes. These are valuable data for understanding the remarkable success of Antarctic pycnogonids, and how environmental changes have shaped the evolution and diversification of Southern Ocean benthic biodiversity. PMID:29134072

Genetic signature of Last Glacial Maximum regional refugia in a circum-Antarctic sea spider

NASA Astrophysics Data System (ADS)

Soler-Membrives, Anna; Linse, Katrin; Miller, Karen J.; Arango, Claudia P.

2017-10-01

The evolutionary history of Antarctic organisms is becoming increasingly important to understand and manage population trajectories under rapid environmental change. The Antarctic sea spider Nymphon australe, with an apparently large population size compared with other sea spider species, is an ideal target to look for molecular signatures of past climatic events. We analysed mitochondrial DNA of specimens collected from the Antarctic continent and two Antarctic islands (AI) to infer past population processes and understand current genetic structure. Demographic history analyses suggest populations survived in refugia during the Last Glacial Maximum. The high genetic diversity found in the Antarctic Peninsula and East Antarctic (EA) seems related to multiple demographic contraction-expansion events associated with deep-sea refugia, while the low genetic diversity in the Weddell Sea points to a more recent expansion from a shelf refugium. We suggest the genetic structure of N. australe from AI reflects recent colonization from the continent. At a local level, EA populations reveal generally low genetic differentiation, geographically and bathymetrically, suggesting limited restrictions to dispersal. Results highlight regional differences in demographic histories and how these relate to the variation in intensity of glaciation-deglaciation events around Antarctica, critical for the study of local evolutionary processes. These are valuable data for understanding the remarkable success of Antarctic pycnogonids, and how environmental changes have shaped the evolution and diversification of Southern Ocean benthic biodiversity.

Integrated Monitoring of the Soya Warm Current Using HF Ocean Radars, Satellite Altimeters, Coastal Tide Gauges, and a Bottom-Mounted ADCP

NASA Astrophysics Data System (ADS)

Ebuchi, N.; Fukamachi, Y.; Ohshima, K. I.; Wakatsuchi, M.

2007-12-01

The Soya Warm Current (SWC) is a coastal boundary current, which flows along the coast of Hokkaido in the Sea of Okhotsk. The SWC flows into the Sea of Okhotsk from the Sea of Japan through the Soya/La Perouse Strait, which is located between Hokkaido, Japan, and Sakhalin, Russia. It supplies warm, saline water in the Sea of Japan to the Sea of Okhotsk and largely affects the ocean circulation and water mass formation in the Sea of Okhotsk, and local climate, environment and fishery in the region. However, the SWC has never been continuously monitored due to the difficulties involved in field observations related to, for example, severe weather conditions in the winter, political issues at the border strait, and conflicts with fishing activities in the strait. Detailed features of the SWC and its variations have not yet been clarified. In order to monitor variations in the SWC, three HF ocean radar stations were installed around the strait. The radar covers a range of approximately 70 km from the coast. It is shown that the HF radars clearly capture seasonal and subinertial variations of the SWC. The velocity of the SWC reaches its maximum, approximately 1 m/s, in summer, and weakens in winter. The velocity core is located 20 to 30 km from the coast, and its width is approximately 50 km. The surface transport by the Soya Warm Current shows a significant correlation with the sea level difference along the strait, as derived from coastal tide gauge records. The cross-current sea level difference, which is estimated from the sea level anomalies observed by the Jason-1 altimeter and a coastal tide gauge, also exhibits variation in concert with the surface transport and along-current sea level difference.

Phase relations of natural 65 year SST variations, ocean sea level variations over 260 years, and Arctic sea-ice retreat of the satellite era - issues of cause and effect.

NASA Astrophysics Data System (ADS)

Asten, Michael

2017-04-01

We study sea level variations over the past 300yr in order to quantify what fraction of variations may be considered cyclic, and what phase relations exist with respect to those cycles. The 64yr cycle detected by Chambers et al (2012) is found in the 1960-2000 data set which Hamlington et al (2013) interpreted as an expression of the PDO; we show that fitting a 64yr cycle is a better fit, accounting for 92% of variance. In a 300yr GMSL tide guage record Jeverejeva et al (2008) identified a 60-65yr cycle superimposed on an upward trend from 1800CE. Using break-points and removal of centennial trends identified by Kemp et al (2015), we produce a detrended GMSL record for 1700-2000CE which emphasizes the 60-65yr oscillations. A least-square fit using a 64yr period cosine yields an amplitude 12mm and origin at year 1958.6, which accounts for 30% of the variance. A plot of the cosine against the entire length of the 300yr detrended GMSL record shows a clear phase lock for the interval 1740 to 2000CE, denoting either a very consistent timing of an internally generated natural variation, or adding to evidence for an external forcing of astronomical origin (Scafetta 2012, 2013). Barcikowska et al (2016) have identified a 65yr cyclic variation in sea surface temperature in the first multidecadal component of Multi- Channel Singular Spectrum Analysis (MSSA) on the Hadley SST data set (RC60). A plot of RC60 versus our fitted cosine shows the phase shift to be 16 yr, close to a 90 degree phase lag of GMSL relative to RC60. This is the relation to be expected for a simple low-pass or integrating filter, which suggests that cyclic natural variations in sea-surface temperature drive similar variations in GMSL. We compare the extent of Arctic sea-ice using the time interval of 1979- 2016 (window of satellite imagery). The decrease in summer ice cover has been subject of many predictions as to when summer ice will reach zero. The plot of measured ice area can be fitted with many speculative curves, and we show three such best fit curves, a parabola (zero ice cover by 2028), a linear fit (zero by 2060) and a 64yr period cosine, where the cosine is a shape chosen as a hypothesis, given the relation we observe between SST natural variations and 260 years of detrended sea level data. The cosine best fit shows a maximum ice coverage in 1985.6 and predicted minimum in 2017.6, which compares with the detrended sea level cyclic component minimum at 1990.6 and predicted maximum at 2023.6CE. Thus the sea-ice retreat lags RC60 by about 10 yr or 60deg in phase. The consistent phase of sea-level change over 260yr, and the phase lags of sea-ice retreat and sea-level change relative to the natural 65yr cyclic component of SST, have implications in the debate over internal versus external drivers of the cyclic components of change, and in hypotheses on cause and effect of the non-anthropogenic components of change.

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.

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.

Shoreline reconstructions for the Persian Gulf since the last glacial maximum

NASA Astrophysics Data System (ADS)

Lambeck, Kurt

1996-07-01

Sea-level change in the Persian Gulf since the time of the last maximum glaciation at about 18 000 yr BP is predicted to exhibit considerable spatial variability, because of the response of the Earth to glacial unloading of the distant ice sheets and to the meltwater loading of the Gulf itself and the adjacent ocean. Models for these glacio-hydro-isostatic effects have been compared with observations of sea-level change and palaeoshoreline reconstructions of the Gulf have been made. From the peak of the glaciation until about 14 000 yr BP the Gulf is free of marine influence out to the edge of the Biaban Shelf. By 14 000 yr BP the Strait of Hormuz had opened up as a narrow waterway and by about 12 500 years ago the marine incursion into the Central Basin had started. The Western Basin flooded about 1000 years later. Momentary stillstands may have occurred during the Gulf flooding phase at about 11 300 and 10 500 yr BP. The present shorelines was reached shortly before 6000 yr ago and exceeded as relative sea level rose 1-2 m above its present level, inundating the low-lying areas of lower Mesopotamia. These reconstructions have implications for models of the evolution of the Euphrates-Tigris-Karun delta, as well as for the movements of people and the timing of the earliest settlements in lower Mesopotamia. For example, the early Gulf floor would have provided a natural route for people moving westwards from regions to the east of Iran from the late Palaeolithic to early Neolithic.

Marine palynological record for tropical climate variations since the late last glacial maximum in the northern South China Sea

NASA Astrophysics Data System (ADS)

Dai, Lu; Weng, Chengyu

2015-12-01

The upper part (191-1439 cm) of the marine sediment core MD05-2906 from the northern South China Sea (SCS) was palynologically investigated. The chronology suggested that it covered the record since ~19 calendar kiloyears before present (cal ka BP) and revealed a detailed environmental change history since the late last glacial maximum (LGM). During the late LGM, due to the lowered sea level (~100 m lower) and the shortened distance from the shore to the study site, the pollen concentration was very high. The pollen assemblages were dominated by non-arboreal taxa, especially Artemisia pollen, before ~15 cal ka BP. Abundant subtropical and tropical pollen taxa were still important components and a south subtropical climate prevailed during the late LGM. The coexistent rich Artemisia pollen possibly was not derived from near shores, but was derived mainly from the northern exposed continental shelf in the East China Sea (ECS). After ~15 cal ka BP, with the rise in the sea level and enhanced distance from the pollen source areas to the core site, pollen concentrations started to decline gradually. However, during the late deglaciation and early Holocene, the higher concentrations of many pollen taxa reoccurred, which cannot be attributed to the sea level changes. Pinus pollen deposited in the core, which is considered to be mostly water-carried based on many modern pollen surveys, also started to dramatically increase at the same time. Therefore, the higher pollen concentration, with more Pinus and Typha (an aquatic plant) pollen indicated a notably enhanced terrestrial runoff and precipitation during the last deglaciation/Holocene transition (~11.3-9.4 cal ka BP). We inferred that a strong summer monsoon occurred at this time. During the late LGM/deglaciation transition period, the pollen assemblage reflected a gradually warming climate, and the climate fluctuations derived from the high-latitudes were not well-identified. This study suggests that solar insolation played a crucial role in controlling the East Asian monsoon and hydrological cycle in the northern SCS.

Impact of sea spray on the Yellow and East China Seas thermal structure during the passage of Typhoon Rammasun (2002)

NASA Astrophysics Data System (ADS)

Zhang, Lianxin; Zhang, Xuefeng; Chu, P. C.; Guan, Changlong; Fu, Hongli; Chao, Guofang; Han, Guijun; Li, Wei

2017-10-01

Strong winds lead to large amounts of sea spray in the lowest part of the atmospheric boundary layer. The spray droplets affect the air-sea heat fluxes due to their evaporation and the momentum due to the change of sea surface, and in turn change the upper ocean thermal structure. In this study, impact of sea spray on upper ocean temperatures in the Yellow and East China Seas (YES) during typhoon Rammasun's passage is investigated using the POMgcs ocean model with a sea spray parameterization scheme, in which the sea spray-induced heat fluxes are based on an improved Fairall's sea spray heat fluxes algorithm, and the sea spray-induced momentum fluxes are derived from an improved COARE version 2.6 bulk model. The distribution of the sea spray mediated turbulent fluxes was primarily located at Rammasun eye-wall region, in accord with the maximal wind speeds regions. When Rammasun enters the Yellow sea, the sea spray mediated latent (sensible) heat flux maximum is enhanced by 26% (13.5%) compared to that of the interfacial latent (sensible) heat flux. The maximum of the total air-sea momentum fluxes is enhanced by 43% compared to the counterpart of the interfacial momentum flux. Furthermore, the sea spray plays a key role in enhancing the intensity of the typhoon-induced "cold suction" and "heat pump" processes. When the effect of sea spray is considered, the maximum of the sea surface cooling in the right side of Rammasun's track is increased by 0.5°C, which is closer to the available satellite observations.

Impacts of Potential Aircraft Observations on Forecasts of Tropical Cyclones Over the Western North Pacific

DTIC Science & Technology

2014-12-01

anticyclone. Vertical wind shear was low, while a moderate level of upper level diffluence existed. The minimum sea level pressure ( SLP ) was estimated...pre-Sinlaku disturbance. At this time, JTWC estimated maximum surface level winds to be 15 to 20 kt, with a SLP near 1005 hPa. 17 Figure 11...poleward side of the circulation. Surface winds had increased to near 23 kt as the SLP continued to fall to 1004 hPa. JTWC forecasters upgraded the

Nutrient Pumping/Advection by Propagating Rossby Waves in the Kuroshio Extension

DTIC Science & Technology

2010-01-01

sea-elevation changes or SLA variance levels are a maximum as eddies and meanders cross a mean route. This boundary in terms of Chl- a levels (lower...and elevated Chl- a levels ) is south of the KE jet. Kuroshio Extension meanders and rings carry different water types across a mean Kuroshio Extension...Fig. 5A). The ring or eddy currents may also redistribute the surface Chl- a levels , drawing out plumes of locally increased Chl-a from regions of

The Impact of Water Loading on Estimates of Postglacial Decay Times in Hudson Bay

NASA Astrophysics Data System (ADS)

Han, H. K.; Gomez, N. A.

2016-12-01

Ongoing glacial isostatic adjustment (GIA) due to surface loading (ice and water) variations since the Last Glacial Maximum (LGM) has been contributing to sea level changes globally throughout the Holocene, especially in regions like the Canada that were heavily glaciated during the LGM. The spatial and temporal distribution of GIA and relative sea level change are attributed to the ice history and the rheological structure of the solid Earth, both of which are uncertain. It has been shown that relative sea level curves in previously glaciated regions follow an exponential-like form, and the post glacial decay times associated with that form have weak sensitivity to the details of the ice loading history (Andrews 1970, Walcott 1980, Mitrovica & Peltier 1995). Post glacial decay time estimates may therefore be used to constrain the Earth's structure and improve GIA predictions. However, estimates of decay times in Hudson Bay in the literature differ significantly due to a number of sources of uncertainty and bias (Mitrovica et al. 2000). Previous decay time analyses have not considered the potential bias that surface loading associated with Holocene sea level changes can introduce in decay time estimates derived from nearby relative sea level observations. We explore the spatial patterns of post glacial decay time predictions in previously glaciated regions, and their sensitivity to ice and water loading history. We compute post glacial sea level changes over the last deglaciation from 21ka to the modern associated with the ICE5G (Peltier, 2004) and ICE6G (Argus et al. 2014, Peltier et al. 2015) ice history models. We fit exponential curves to the modeled relative sea level changes, and compute maps of post glacial decay time predictions across North America and the Arctic. In addition, we decompose the modeled relative sea level changes into contributions from water and ice loading effects, and compute the impact of water loading redistribution since the LGM on present day decay times. We show that Holocene water loading in the Hudson Bay may introduce significant bias in decay time estimates and we highlight locations where biases are minimized.

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.

Glacio-isostasy and Glacial Ice Load at Law Dome, Wilkes Land, East Antarctica

NASA Astrophysics Data System (ADS)

Goodwin, Ian D.; Zweck, Christopher

2000-05-01

The Holocene sea-level high stand or "marine limit" in Wilkes Land, East Antarctica, reached ˜30 m above present sea level at a few dispersed sites. The most detailed marine limit data have been recorded for the Windmill Islands and Budd Coast at the margin of the Law Dome ice cap, a dome of the East Antarctic Ice Sheet (EAIS). Relative sea-level lowering of 30 m and the associated emergence of the Windmill Islands have occurred since 6900 14C (corr.) yr B.P. Numerical modeling of the Earth's rheology is used to determine the glacio-isostatic component of the observed relative sea-level lowering. Glaciological evidence suggests that most of EAIS thickening occurred around its margin, with expansion onto the continental shelf. Consequently, a regional ice history for the last glacial maximum (LGM) was applied in the glacio-isostatic modeling to test whether the observed relative sea-level lowering was primarily produced by regional ice-sheet changes. The results of the modeling indicate that the postglacial (13,000 to 8000 14C yr B.P) removal of an ice load of between 770 and 1000 m from around the margin of the Law Dome and adjacent EAIS have produced the observed relative sea-level lowering. Such an additional ice load would have been associated with a 40- to 65-km expansion of the Law Dome to near the continental shelf break, together with a few hundred meters of ice thickening on the adjoining coastal slope of the EAIS up to 2000 m elevation. Whereas the observed changes in relative sea level are shown to be strongly influenced by regional ice sheet changes, the glacio-isostatic response at the Windmill Islands results from a combination of regional and, to a lesser extent, Antarctic-wide effects. The correspondence between the Holocene relative sea-level lowering interpreted at the margin of the Law Dome and the lowering interpreted along the remainder of the Wilkes Land and Oates Land coasts (105°-160° E) suggests that a similar ice load of up to 1000 m existed along the EAIS margin between Wilkes Land and Oates Land.

Dating glacimarine sediments from the continental shelf in the Amundsen Sea using a multi-tool box: Implications for West Antarctic ice-sheet extent and retreat during the last glacial cycle

NASA Astrophysics Data System (ADS)

Hillenbrand, C. D.; Smith, J.; Klages, J. P.; Kuhn, G.; Maher, B.; Moreton, S.; Wacker, L.; Frederichs, T.; Wiers, S.; Jernas, P.; Anderson, J. B.; Ehrmann, W. U.; Graham, A. G. C.; Gohl, K.; Larter, R. D.

2016-02-01

Satellite data and in-situ measurements show that today considerable mass loss is occurring from the Amundsen Sea sector of the West Antarctic Ice Sheet (WAIS). The observational record only spans the past four decades, and until recently the long-term context of the current deglaciation was poorly constrained. This information is, however, crucial for understanding WAIS dynamics, evaluating the role of forcing mechanisms for ice-sheet melting, and testing and calibrating ice-sheet models that attempt to predict future WAIS behavior and its impact on global sea level. Over the past decade several multinational marine expeditions and terrestrial fieldwork campaigns have targeted the Amundsen Sea shelf and its hinterland to reconstruct the WAIS configuration during the Last Glacial Maximum (LGM) and its subsequent deglacial history. The resulting studies succeeded in shedding light on the maximum WAIS extent at the LGM and the style, pattern and speed of its retreat and thinning thereafter. Despite this progress, however, significant uncertainties and discrepancies between marine and terrestrial reconstructions remain, which may arise from difficulties in dating sediment cores from the Antarctic shelf, especially their deglacial sections. Resolving these issues is crucial for understanding the WAIS' contribution to post-LGM sea-level rise, its sensitivity to different forcing mechanisms and its future evolution. Here we present chronological constraints on WAIS advance in the Amundsen Sea and its retreat from 20 ka BP into the Holocene that were obtained by various techniques, such as 14C dating of large ( 10 mg) and small (<<1 mg) sample aliquots of calcareous microfossils, 14C dating of acid-insoluble organic matter combusted at low (300 °C) and high (800 °C) temperatures and dating of sediment cores by using geomagnetic paleointensity. We will compare the different age constraints and discuss their reliability, applicability and implications for WAIS history.

Relative sea level changes during the Cretaceous in Israel

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

Flexer, A.; Rosenfeld, A.; Lipson-Benitah, S.

1986-11-01

Detailed lithologic, microfaunal, and biometric investigations, using relative abundances, diversity indexes, and duration charts of ostracods and foraminifera, allowed the recognition of sea level changes during the Cretaceous of Israel. Three major transgressive-regressive sedimentation cycles occur on the northwest margins of the Arabian craton. These cycles are the Neocomian-Aptian, which is mostly terrigenous sediments; the Albian-Turonian, which is basin marls and platform carbonates; and the Senonian, which is uniform marly chalks. The cycles are separated by two major regional unconformities, the Aptian-Albian and Turonian-Coniacian boundaries. The sedimentary cycles are related to regional tectonic and volcanic events and eustatic changes. Themore » paleodepth curve illustrates the gradual sea level rise, reaching its maximum during the Late Cretaceous, with conspicuous advances during the late Aptian, late Albian-Cenomanian, early Turonian, early Santonian, and early Campanian. Major lowstands occur at the Aptian-Albian, Cenomanian-Turonian, Turonian-Coniacian, and Campanian-Maastrichtian boundaries. This model for Israel agrees well with other regional and global sea level fluctuations. Four anoxic events (black shales) accompanying transgressions correspond to the Cretaceous oceanic record. They hypothesize the presence of mature oil shales in the present-day eastern Mediterranean basin close to allochthonous reef blocks detached from the Cretaceous platform. 11 figures.« less

Drivers of Holocene sea-level change in the Caribbean

USGS Publications Warehouse

Khan, Nicole; Ashe, Erica; Horton, Benjamin P.; Dutton, Andrea; Kopp, Robert E.; Brocard, Gilles; Engelhart, Simon E.; Hill, David F.; Peltier, W.R.; Vane, Christopher H.; Scatena, Fred N.

2017-01-01

We present a Holocene relative sea-level (RSL) database for the Caribbean region (5°N to 25°N and 55°W to 90°W) that consists of 499 sea-level index points and 238 limiting dates. The database was compiled from multiple sea-level indicators (mangrove peat, microbial mats, beach rock and acroporid and massive corals). We subdivided the database into 20 regions to investigate the influence of tectonics and glacial isostatic adjustment on RSL. We account for the local-scale processes of sediment compaction and tidal range change using the stratigraphic position (overburden thickness) of index points and paleotidal modeling, respectively. We use a spatio-temporal empirical hierarchical model to estimate RSL position and its rates of change in the Caribbean over 1-ka time slices. Because of meltwater input, the rates of RSL change were highest during the early Holocene, with a maximum of 10.9 ± 0.6 m/ka in Suriname and Guyana and minimum of 7.4 ± 0.7 m/ka in south Florida from 12 to 8 ka. Following complete deglaciation of the Laurentide Ice Sheet (LIS) by ∼7 ka, mid-to late-Holocene rates slowed to < 2.4 ± 0.4 m/ka. The hierarchical model constrains the spatial extent of the mid-Holocene highstand. RSL did not exceed the present height during the Holocene, except on the northern coast of South America, where in Suriname and Guyana, RSL attained a height higher than present by 6.6 ka (82% probability). The highstand reached a maximum elevation of +1.0 ± 1.1 m between 5.3 and 5.2 ka. Regions with a highstand were located furthest away from the former LIS, where the effects from ocean syphoning and hydro-isostasy outweigh the influence of subsidence from forebulge collapse.

Comparing growth rates of Arctic Cod Boreogadus saida across the Chukchi and Beaufort Seas

NASA Astrophysics Data System (ADS)

Frothingham, A. M.; Norcross, B.

2016-02-01

Dramatic changes to the Arctic have highlighted the need for a greater understanding of the present ecosystem. Arctic Cod, Boreogadus saida, commonly dominate fish assemblages in the Arctic region and inhabit two geographically unique seas in the U.S. Due to the importance of Arctic Cod in the Arctic food web, establishing current benchmark information such as growth rates, will provide a better understanding as to how the species will adapt to the effects of climate change. To investigate differences in Arctic Cod life history across nearly 1500 km of vital habitat, growth rates were examined using a von Bertalanffy growth equation. Arctic Cod were collected from 2009 to 2014 from the Chukchi and Beaufort seas. Arctic Cod collected from the Chukchi Sea had an overall smaller maximum achievable length (210 mm) compared to the Beaufort Sea (253 mm) despite a larger sample size in the Chukchi Sea (n=1569) than the Beaufort Sea (n=1140). Growth rates indicated faster growth in the Chukchi Sea (K =0.33) than in the Beaufort Sea (K= 0.29). Arctic Cod collected from the Chukchi Sea had similar achievable maximum lengths throughout, but those collected from the southern Chukchi Sea grew at faster rates (K=0.45).Arctic Cod in the eastern Beaufort Sea region had a higher overall maximum achievable length (243 mm) than in the western Beaufort Sea region (186 mm). Knowledge about contemporary growth rates of Arctic Cod in the Chukchi and Beaufort Seas can be used in future comparisons to evaluate potential effects of increasing climate change and anthropogenic influences.

Intercomparison of global, ultraviolet B and A radiation measurements in the Dead Sea region (Ein Bokek) and Beer Sheva.

PubMed

Kushelevsky, A P; Kudish, A I

1996-07-01

Thousands of patients suffering from psoriasis have been treated successfully in the Dead Sea area by climatological methods, without medication. This high rate of success, measured in terms of partial to complete plaque clearance and reported to exceed 85% after 3-4 weeks of treatment, has been assumed to be associated with a unique ultraviolet (UV) radiation environment present in the Dead Sea region. In order to broaden our knowledge of the UV radiation environment at the Dead Sea, continuous monitoring of UV (both B and A) and global radiation has recently been initiated at two sites--Ein Bokek (located in the vicinity of the Dead Sea 375 m below mean sea level) and Beer Sheva (315 m above mean sea level)--to facilitate an intercomparison of their respective radiation intensities. The results of the first year of a detailed study of the global, UVB and UVA radiation intensities measured at both sites are summarized and reported in terms of the monthly average daily, average midday (11:00-13:00) and the corresponding maximum values. The radiation data for clear days (based upon the absolute magnitude of the global radiation) were also analyzed to perform an intercomparison between Ein Bokek and Beer Sheva for a winter month and a summer month for which all three types of radiation data were available at both sites.

14 CFR 23.77 - Balked landing.

Code of Federal Regulations, 2010 CFR

2010-01-01

... pounds or less maximum weight must be able to maintain a steady gradient of climb at sea level of at... acrobatic category turbine engine-powered airplane must be able to maintain a steady gradient of climb of at....73(b). (c) Each commuter category airplane must be able to maintain a steady gradient of climb of at...

Control Performance of General Electric Fuel and Torque Regulator Operating on T31-3 Turbine-Propeller Engine in Sea-Level Test Stand

NASA Technical Reports Server (NTRS)

Oppenheimer, Frank L.; Lazar, James

1951-01-01

A .General Electric fuel and torque regulator was tested in conjunction with a T31-3 turbine-propeller engine in the sea-level static test stand at the NACA Lewis laboratory. The engine and control were operated over the entire speed range: 11,000 rpm, nominal flight idle, to 13,000 rpm, full power. Steady-state and transient data were recorded and are presented with a description of the four control loops being used in the system. Results of this investigation indicated that single-lever control operation was satisfactory under conditions of test. Transient data presented showed that turbine-outlet temperature did overshoot maximum operating value on acceleration but that the time duration of overshoot did not exceed approximately 1 second. This temperature limiting resulted from a control on fuel flow as a function of engine speed. Speed and torque first reached their desired values 0.4 second from the time of change in power-setting lever position. Maximum speed overshoot was 3 percent.

Last Glacial Maximum to Holocene climate evolution controlled by sea-level change, Leeuwin Current, and Australian Monsoon in the Northwestern Australia

NASA Astrophysics Data System (ADS)

Ishiwa, T.; Yokoyama, Y.; McHugh, C.; Reuning, L.; Gallagher, S. J.

2017-12-01

The transition from cold to warm conditions during the last deglaciation influenced climate variability in the Indian Ocean and Pacific as a result of submerge of continental shelf and variations in the Indonesian Throughflow and Australian Monsoon. The shallow continental shelf (< 200 m water depth) developed along the northwestern Australian margin is influenced by the Australian Monsoon and Leeuwin Current (one of branch of the Indonesian Throughflow). The International Ocean Discovery Program Expedition 356 Indonesian Throughflow drilled in the northwestern Australian shallow continental shelf and recovered an interval from the Last Glacial Maximum to Holocene in Site U1461. Radiocarbon dating on macrofossils, foraminifera, and bulk organic matter provided a precise age-depth model, leading to high-resolved paleoclimate reconstruction. X-ray elemental analysis results are interpreted as an indicator of sedimentary environmental changes. The upper 20-m part of Site U1461 apparently records the climate transition from the LGM to Holocene in the northwestern Australia, which could be associated with sea-level change, Leeuwin Current activity, and the Australian Monsoon.

Changes in monsoon-driven upwelling in the South China Sea over glacial Terminations I and II: a multi-proxy record

NASA Astrophysics Data System (ADS)

Sadatzki, Henrik; Sarnthein, Michael; Andersen, Nils

2016-06-01

Upwelling intensity in the South China Sea has changed over glacial-interglacial cycles in response to orbital-scale changes in the East Asian Monsoon. Here, we evaluate new multi-proxy records of two sediment cores from the north-eastern South China Sea to uncover millennial-scale changes in winter monsoon-driven upwelling over glacial Terminations I and II. On the basis of U/Th-based speleothem chronology, we compare these changes with sediment records of summer monsoon-driven upwelling east of South Vietnam. Ocean upwelling is traced by reduced (UK'37-based) temperature and increased nutrient and productivity estimates of sea surface waters (δ13C on planktic foraminifera, accumulation rates of alkenones, chlorins, and total organic carbon). Accordingly, strong winter upwelling occurred north-west of Luzon (Philippines) during late Marine Isotope Stage 6.2, Heinrich (HS) and Greenland stadials (GS) HS-11, GS-26, GS-25, HS-1, and the Younger Dryas. During these stadials, summer upwelling decreased off South Vietnam and sea surface salinity reached a maximum suggesting a drop in monsoon rains, concurrent with speleothem records of aridity in China. In harmony with a stadial-to-interstadial see-saw pattern, winter upwelling off Luzon in turn was weak during interstadials, in particular those of glacial Terminations I and II, when summer upwelling culminated east of South Vietnam. Most likely, this upwelling terminated widespread deep-water stratification, coeval with the deglacial rise in atmospheric CO2. Yet, a synchronous maximum in precipitation fostered estuarine overturning circulation in the South China Sea, in particular as long as the Borneo Strait was closed when sea level dropped below -40 m.

Disentangling the impact of nutrient load and climate changes on Baltic Sea hypoxia and eutrophication since 1850

NASA Astrophysics Data System (ADS)

Meier, H. E. M.; Eilola, K.; Almroth-Rosell, E.; Schimanke, S.; Kniebusch, M.; Höglund, A.; Pemberton, P.; Liu, Y.; Väli, G.; Saraiva, S.

2018-06-01

In the Baltic Sea hypoxia has been increased considerably since the first oxygen measurements became available in 1898. In 2016 the annual maximum extent of hypoxia covered an area of the sea bottom of about 70,000 km2, comparable with the size of Ireland, whereas 150 years ago hypoxia was presumably not existent or at least very small. The general view is that the increase in hypoxia was caused by eutrophication due to anthropogenic riverborne nutrient loads. However, the role of changing climate, e.g. warming, is less clear. In this study, different causes of expanding hypoxia were investigated. A reconstruction of the changing Baltic Sea ecosystem during the period 1850-2008 was performed using a coupled physical-biogeochemical ocean circulation model. To disentangle the drivers of eutrophication and hypoxia a series of sensitivity experiments was carried out. We found that the decadal to centennial changes in eutrophication and hypoxia were mainly caused by changing riverborne nutrient loads and atmospheric deposition. The impacts of other drivers like observed warming and eustatic sea level rise were comparatively smaller but still important depending on the selected ecosystem indicator. Further, (1) fictively combined changes in air temperature, cloudiness and mixed layer depth chosen from 1904, (2) exaggerated increases in nutrient concentrations in the North Sea and (3) high-end scenarios of future sea level rise may have an important impact. However, during the past 150 years hypoxia would not have been developed if nutrient conditions had remained at pristine levels.

Impacts of sea-level rise on the Moroccan coastal zone: Quantifying coastal erosion and flooding in the Tangier Bay

NASA Astrophysics Data System (ADS)

Snoussi, Maria; Ouchani, Tachfine; Khouakhi, Abdou; Niang-Diop, Isabelle

2009-06-01

As part of a broad assessment of climate change impacts in Morocco, an assessment of vulnerability and adaptation of coastal zones to sea-level rise was conducted. Tangier Bay which is the most important socio-economic pole in Northern Morocco represents one of the cases studies. Using a GIS-based inundation analysis and an erosion modelling approach, the potential physical vulnerability to accelerated sea-level rise was investigated, and the most vulnerable socio-economic sectors were assessed. Results indicate that 10% and 24% of the area will be at risk of flooding respectively for minimum (4 m) and maximum (11 m) inundation levels. The most severely impacted sectors are expected to be the coastal defences and the port, the urban area, tourist coastal infrastructures, the railway, and the industrial area. Shoreline erosion would affect nearly 20% and 45% of the total beach areas respectively in 2050 and 2100. Potential response strategies and adaptation options identified include: sand dune fixation, beach nourishment and building of seawalls to protect the urban and industrial areas of high value. It was also recommended that an Integrated Coastal Zone Management Plan for the region, including upgrading awareness, building regulation and urban growth planning should be the most appropriate tool to ensure a long-term sustainable development, while addressing the vulnerability of the coast to future sea-level rise.

Food intake and growth of Sarsia tubulosa (SARS, 1835), with quantitative estimates of predation on copepod populations

NASA Astrophysics Data System (ADS)

Daan, Rogier

In laboratory tests food intake by the hydromedusa Sarsia tubulosa, which feeds on copepods, was quantified. Estimates of maximum predation are presented for 10 size classes of Sarsia. Growth rates, too, were determined in the laboratory, at 12°C under ad libitum food conditions. Mean gross food conversion for all size classes averaged 12%. From the results of a frequent sampling programme, carried out in the Texelstroom (a tidal inlet of the Dutch Wadden Sea) in 1983, growth rates of Sarsia in the field equalled maximum growth under experimental conditions, which suggests that Sarsia in situ can feed at an optimum level. Two estimates of predation pressure in the field matched very closely and lead to the conclusion that the impact of Sarsia predation on copepod standing stocks in the Dutch coastal area, including the Wadden Sea, is generally negligible.

Dynamics of Monsoon-Induced Biennial Variability in ENSO

NASA Technical Reports Server (NTRS)

Kim, Kyu-Myong; Lau, K.-M.; Einaudi, Franco (Technical Monitor)

2000-01-01

The mechanism of the quasi-biennial tendency in El Nino Southern Oscillation (ENSO)-monsoon coupled system is investigated using an intermediate coupled model. The monsoon wind forcing is prescribed as a function of Sea Surface Temperature (SST) anomalies based on the relationship between zonal wind anomalies over the western Pacific to sea level change in the equatorial eastern Pacific. The key mechanism of quasi-biennial tendency in El Nino evolution is found to be in the strong coupling of ENSO to monsoon wind forcing over the western Pacific. Strong boreal summer monsoon wind forcing, which lags the maximum SST anomaly in the equatorial eastern Pacific approximately 6 months, tends to generate Kelvin waves of the opposite sign to anomalies in the eastern Pacific and initiates the turnabout in the eastern Pacific. Boreal winter monsoon forcing, which has zero lag with maximum SST in the equatorial eastern Pacific, tends to damp the ENSO oscillations.

Marine evidence of a deconvolving Antarctic Ice Sheet during post-LGM retreat of the Ross Sea sector

NASA Astrophysics Data System (ADS)

Prothro, L. O.; Yokoyama, Y.; Simkins, L. M.; Anderson, J. B.; Majewski, W.; Yamane, M.; Ohkouchi, N.

2017-12-01

Predictive models of ice sheet and sea level change are dependent on observational data of ice-sheet behavior for model testing and tuning. The geologic record contains a wealth of information about ice-sheet dynamics, with fewer logistical, spatial, and temporal limitations than are involved in data acquisition along contemporary ice margins. However, past ice-sheet behavior is still largely uncertain or contested due to issues with obtaining meaningful radiocarbon dates. We minimize bias from glacially-reworked carbon and limitations from unknown geomorphic context and uncertainty in sediment facies identification by using careful sedimentary analyses within a geomorphic framework, as well as selection of appropriate dating methods. Our study area, the Ross Sea sector of Antarctica, is the primary drainage outlet for 25% of the continent's grounded ice. During the Last Glacial Maximum, the low-profile, marine-based West Antarctic Ice Sheet (WAIS) and the steeper profile, largely land-based East Antarctic Ice Sheet (EAIS) converged in the Ross Sea to flow out to or near the continental shelf edge. Geomorphic and sedimentary data reveal that during their subsequent retreat to form the Ross Sea Embayment, the two ice sheets behaved differently, with the WAIS rapidly retreating tens of kilometers followed by extended pauses, while the EAIS retreated steadily, with shorter (decadal- to century-long) pauses. This behavior leads us to believe that the two ice sheets may have contributed diachronously to sea level. By acquiring accurate timing of grounding line retreat, we are able to calculate volumes of ice lost throughout deglaciation, as well as associated sea level contributions. In addition, we attempt to rectify the contradicting marine and terrestrial interpretations of retreat patterns from the Ross Sea continental shelf.

Compiling Holocene RSL databases from near- to far-field regions: proxies, difficulties and possible solutions

NASA Astrophysics Data System (ADS)

Vacchi, M.; Horton, B.; Mann, T.; Engelhart, S. E.; Rovere, A.; Nikitina, D.; Bender, M.; Roy, K.; Peltier, W. R.

2017-12-01

Reconstructions of relative sea level (RSL) have implications for investigation of crustal movements, calibration of earth rheology models and the reconstruction of ice sheets. In recent years, efforts were made to create RSL databases following a standardized methodology. These regional databases provide a framework for developing our understanding of the primary mechanisms of RSL change since the Last Glacial Maximum and a long-term baseline against which to gauge changes in sea level during the 20th century and forecasts for the 21st. We report here the results of recently compiled databases in very different climatic and geographic contexts that are the northeastern Canadian coast, the Mediterranean Sea as well as the southeastern Asiatic region. Our re-evaluation of sea-level indicators from geological and archaeological investigations have yielded more than 3000 RSL data-points mainly from salt and freshwater wetlands or adjacent estuarine sediment, isolation basins, beach ridges, fixed biological indicators, beachrocks as well as coastal archaeological structures. We outline some of the inherent difficulties, and potential solutions to analyse sea-level data in such different depositional environments. In particular, we discuss problems related with the definition of standardized indicative meaning, and with the re-evaluation of old radiocarbon samples. We further address complex tectonics influences and the framework to compare such large variability of RSL data-points. Finally we discuss the implications of our results for the patterns of glacio-isostatic adjustment in these regions.

Survey of total mercury and methylmercury levels in edible fish from the Adriatic Sea.

PubMed

Storelli, M M; Giacominelli-Stuffler, R; Storelli, A; D'Addabbo, R; Palermo, C; Marcotrigiano, G O

2003-12-01

Total mercury and methylmercury concentrations were measured in the muscle tissue of different fish species from the Adriatic Sea to ascertain whether the concentrations exceeded the maximum level fixed by the European Commission. Large species-dependent variability was observed. The highest total mercury mean concentrations were in benthic (0.20-0.76 microg g(-1) wet wt) and demersal fish (0.22-0.73 microg g(-1) wet wt), while pelagic species showed the lowest levels (0.09-0.23 microg g(-1) wet wt). In 15% of frost fish, in 42% of skate and in 30% of angler fish samples total mercury concentrations exceeded the maximum level fixed by the European Commission (Hg = 1 microg g(-1) wet wt); for the species for which the maximum level was set to 0.5 microg g(-1) wet wt, concentrations exceeding the prescribed legal limit were observed in 6.4% of bokkem, in 6.6% of pandora, in 20% of megrin, in 12.5% of four-spotted megrim, in 16% of striped mullet, in 5.0% of forkbeard and in 5.3% of picarel samples. In all the different species, mercury was present almost completely in the methylated form, with mean percentages between 70 and 100%. Weekly intake was estimated and compared with the provisional tolerable weekly intake recommended by the FAO/WHO Expert Committee on Food Additives. A high exposure was associated with the consumption of only skates, frost fish and angler fish, thought the consumption of the other species, such as, megrim, four spotted megrim, red fish striped mullet and forkbeard, resulted in a weekly intake slightly below the established provisional tolerable weekly intake.

Vulnerability of marginal seas to sea level rise

NASA Astrophysics Data System (ADS)

Gomis, Damia; Jordà, Gabriel

2017-04-01

Sea level rise (SLR) is a serious thread for coastal areas and has a potential negative impact on society and economy. SLR can lead for instance to land loss, beach reduction, increase of the damage of marine storms on coastal infrastructures and to the salinization of underground water streams. It is well acknowledged that future SLR will be inhomogeneous across the globe, with regional differences of up to 100% with respect to global mean sea level (GMSL). Several studies have addressed the projections of SLR at regional scale, but most of them are based on global climate models (GCMs) that have a relatively coarse spatial resolution (>1°). In marginal seas this has proven to be a strong limitation, as their particular configurations require spatial resolutions that are not reachable by present GCMs. A paradigmatic case is the Mediterranean Sea, connected to the global ocean through the Strait of Gibraltar, a narrow passage of 14 km width. The functioning of the Mediterranean Sea involves a variety of processes including an overturning circulation, small-scale convection and a rich mesoscale field. Moreover, the long-term evolution of Mediterranean sea level has been significantly different from the global mean during the last decades. The observations of present climate and the projections for the next decades have lead some authors to hypothesize that the particular characteristics of the basin could allow Mediterranean mean sea level to evolve differently from the global mean. Assessing this point is essential to undertake proper adaptation strategies for the largely populated Mediterranean coastal areas. In this work we apply a new approach that combines regional and global projections to analyse future SLR. In a first step we focus on the quantification of the expected departures of future Mediterranean sea level from GMSL evolution and on the contribution of different processes to these departures. As a result we find that, in spite of its particularities, Mediterranean Sea level would follow global changes with departures lower than + 5 cm. In a second step we use the same methodology to obtain SLR projections at global scale in order to assess the vulnerability of other coastal areas. Namely, we define a vulnerability index based on relating the characteristics of present day variability with SLR projections under different scenarios. Results show that the averaged vulnerability index is 0.5 for scenario RCP8.5 (projected SLR is about a half of the maximum sea level recorded in the last decades). However, in the Mediterranean, the Caribbean and the Sea of Japan the vulnerability index is much higher (2.6, 2.4 and 2.1, respectively). From this point of view, therefore, these regions could be considered the most vulnerable regions in the world.

Aeroelastic Stability of the LCTR2 Civil Tiltrotor

DTIC Science & Technology

2008-10-01

Airfoils MCP Maximum Continuous Power MRP Maximum Rated Power (take-off power) OGE Out of Ground Effect SFC Specific Fuel Consumption SLS Sea-Level...Ref. 6). Aircraft technology projections from the LCTR1 have been updated for the LCTR2 based on a service entry date of 2018. Table 1 summarizes...Length, ft 108.9 Wing span, ft 107.0 Wing loading, lb/ft2 107.4 Wing sweep −5.0 deg Engine power, hp 4×7500 SFC (at MRP , SLS), lb/hr/hp 0.373

Impact of asymmetry in the total ozone distribution in Antarctic region to the South Ocean ecosystem

NASA Astrophysics Data System (ADS)

Kovalenok, S.; Evtushevsky, A.; Grytsai, A.; Milinevsky, G.

2009-04-01

Impact of asymmetry in the total ozone distribution in Antarctic region to South Ocean ecosystem is studied. The existence of the considerable zonal asymmetry in total ozone distribution over Antarctica observed last decades based on the satellite TOMS measurements in 1979-2005 due to existence of quasi-stationary planetary waves in a polar stratosphere. As was shown by authors earlier in the latitudinal interval of 55-75°S in Antarctic spring months (Sep-Nov) the region of zonal total ozone minimum experienced the systematic spatial drift to the east. In the same period a minimum and maximum of quasi-stationary wave in TOC distribution are located: minimum over the Antarctic Peninsula and Weddell Sea area, and maximum in the Ross Sea area. We expect that zonal asymmetry in total ozone distribution and its long-term spatial changes should impact to South Ocean ecosystem food chain, especially in primary level. The systematic eastern shift of the quasi-stationary minimum in ozone distribution over north Weddell Sea area should cause the increased UV radiation on sea surface in comparison to Ross Sea area, where the lack of UVR should exist in spring month. To study this influence the available data of phytoplankton distribution in South Ocean in 1997-2007 were analyzed. The results of analysis in connections with Antarctic Peninsula regional climate warming are discussed. The research was partly supported by project 06BF051-12 of the National Taras Shevchenko University of Kyiv.

Early-to-middle Holocene sea-level fluctuations, coastal progradation and the Neolithic occupations in Yaojiang valley of southern Hangzhou bay, eastern China

NASA Astrophysics Data System (ADS)

Liu, Y.; Sun, Q.; Fan, D.; Chen, Z.

2017-12-01

The formation of Holocene coast in eastern China provided material base for the development of Neolithic civilizations. The coastal Yaojiang valley of south Hangzhou bay was one of the examples where the well-known Neolithic Hemudu Culture (HC) of Eastern China initiated. Here, we studied the early-to-middle Holocene environment changes in relation to sea-level fluctuations on the basis of a serial of sediment cores based on a set of new Accelerator Mass Spectrometry radiocarbon (AMS 14C) chronology. The result indicated that relative sea-level rose rapidly in the Yaojiang valley at the early Holocene, reaching its maximum at ca. 8000-7800 cal yr BP and then decelerated at ca. 7800-7500 cal yr BP. The alluvial plain in Yaojiang valley began to form at the foothills first and then grew towards the valley center accompanying with the sea-level stabilization after ca. 7500 cal yr BP. This progressive progradation of alluvial plain would attract the early arrivals of foragers to dwell at the foothills to engaging in rice farming after ca.7000 cal yr BP and starting the epic Hemudu Culture. The HC people then move down to the valley center as more land became available thanks to sediment aggregation and progradation. The rise and development of HC were closely associated with the sea-level induced landscape changes in Yaojiang valley at the early-middle Holocene, and the unstable hydraulic condition in the valley after 5000 cal yr BP could be accountable for the cultural termination.

Altitude-Related Change in Endotracheal Tube Cuff Pressures in Helicopter EMS

PubMed Central

Weisberg, Stacy N.; McCall, Jonathan C.; Tennyson, Joseph

2017-01-01

Introduction Over-inflation of endotracheal tube (ETT) cuffs has the potential to lead to scarring and stenosis of the trachea.1, 2,3, 4 The air inside an ETT cuff is subject to expansion as atmospheric pressure decreases, as happens with an increase in altitude. Emergency medical services helicopters are not pressurized, thereby providing a good environment for studying the effects of altitude changes ETT cuff pressures. This study aims to explore the relationship between altitude and ETT cuff pressures in a helicopter air-medical transport program. Methods ETT cuffs were initially inflated in a nonstandardized manner and then adjusted to a pressure of 25 cmH2O. The pressure was again measured when the helicopter reached maximum altitude. A final pressure was recorded when the helicopter landed at the receiving facility. Results We enrolled 60 subjects in the study. The mean for initial tube cuff pressures was 70 cmH2O. Maximum altitude for the program ranged from 1,000–3,000 feet above sea level, with a change in altitude from 800–2,480 feet. Mean cuff pressure at altitude was 36.52 ± 8.56 cmH2O. Despite the significant change in cuff pressure at maximum altitude, there was no relationship found between the maximum altitude and the cuff pressures measured. Conclusion Our study failed to demonstrate the expected linear relationship between ETT cuff pressures and the maximum altitude achieved during typical air-medical transportation in our system. At altitudes less than 3,000 feet above sea level, the effect of altitude change on ETT pressure is minimal and does not require a change in practice to saline-filled cuffs. PMID:28611883

Altitude-Related Change in Endotracheal Tube Cuff Pressures in Helicopter EMS.

PubMed

Weisberg, Stacy N; McCall, Jonathan C; Tennyson, Joseph

2017-06-01

Over-inflation of endotracheal tube (ETT) cuffs has the potential to lead to scarring and stenosis of the trachea.1, 2,3, 4 The air inside an ETT cuff is subject to expansion as atmospheric pressure decreases, as happens with an increase in altitude. Emergency medical services helicopters are not pressurized, thereby providing a good environment for studying the effects of altitude changes ETT cuff pressures. This study aims to explore the relationship between altitude and ETT cuff pressures in a helicopter air-medical transport program. ETT cuffs were initially inflated in a nonstandardized manner and then adjusted to a pressure of 25 cmH 2 O. The pressure was again measured when the helicopter reached maximum altitude. A final pressure was recorded when the helicopter landed at the receiving facility. We enrolled 60 subjects in the study. The mean for initial tube cuff pressures was 70 cmH 2 O. Maximum altitude for the program ranged from 1,000-3,000 feet above sea level, with a change in altitude from 800-2,480 feet. Mean cuff pressure at altitude was 36.52 ± 8.56 cmH 2 O. Despite the significant change in cuff pressure at maximum altitude, there was no relationship found between the maximum altitude and the cuff pressures measured. Our study failed to demonstrate the expected linear relationship between ETT cuff pressures and the maximum altitude achieved during typical air-medical transportation in our system. At altitudes less than 3,000 feet above sea level, the effect of altitude change on ETT pressure is minimal and does not require a change in practice to saline-filled cuffs.

Several specific and nonspecific responses of the human and animal body to ship noise

NASA Technical Reports Server (NTRS)

Markaryan, S. S.; Volkov, S. S.; Sysoyev, A. B.

1983-01-01

The effect of noise on cargo boats on a long voyage differs considerably from the effect of noise in factories and in service industries. The peculiarities of the effect of round-the-clock noises at sea at 55 to 85 decibels, typical for cargo boats, were studied in white rats in the laboratory and aboard ship (each of the experiments lasted three months) and in young naval cadets and experienced seamen on voyages lasting one, two, and three months. The findings helped to derive health standards for maximum admissible noise level at sea.

Kara Sea radioactivity assessment.

PubMed

Osvath, I; Povinec, P P; Baxter, M S

1999-09-30

Investigations following five international expeditions to the Kara Sea have shown that no radiologically significant contamination has occurred outside of the dumping sites in Novaya Zemlya bays. Increased levels of radionuclides in sediment have only been observed in Abrosimov and Stepovoy Bays very close to dumped containers. Evaluations of radionuclide inventories in water and sediment of the open Kara Sea and Novaya Zemlya bays as well as soil from the shore of Abrosimov bay have shown that radionuclide contamination of the open Kara Sea is mainly due to global fallout, with smaller contributions from the Sellafield reprocessing plant, the Chernobyl accident run-off from the Ob and Yenisey rivers and local fallout. Computer modelling results have shown that maximum annual doses of approximately 1 mSv are expected for a hypothetical critical group subsisting on fish caught in the Novaya Zemlya bays whereas populations living on the mainland can be expected to receive doses at least three orders of magnitude lower.

Spatial variation of statistical properties of extreme water levels along the eastern Baltic Sea

NASA Astrophysics Data System (ADS)

Pindsoo, Katri; Soomere, Tarmo; Rocha, Eugénio

2016-04-01

Most of existing projections of future extreme water levels rely on the use of classic generalised extreme value distributions. The choice to use a particular distribution is often made based on the absolute value of the shape parameter of the Generalise Extreme Value distribution. If this parameter is small, the Gumbel distribution is most appropriate while in the opposite case the Weibull or Frechet distribution could be used. We demonstrate that the alongshore variation in the statistical properties of numerically simulated high water levels along the eastern coast of the Baltic Sea is so large that the use of a single distribution for projections of extreme water levels is highly questionable. The analysis is based on two simulated data sets produced in the Swedish Meteorological and Hydrological Institute. The output of the Rossby Centre Ocean model is sampled with a resolution of 6 h and the output of the circulation model NEMO with a resolution of 1 h. As the maxima of water levels of subsequent years may be correlated in the Baltic Sea, we also employ maxima for stormy seasons. We provide a detailed analysis of spatial variation of the parameters of the family of extreme value distributions along an approximately 600 km long coastal section from the north-western shore of Latvia in the Baltic Proper until the eastern Gulf of Finland. The parameters are evaluated using maximum likelihood method and method of moments. The analysis also covers the entire Gulf of Riga. The core parameter of this family of distributions, the shape parameter of the Generalised Extreme Value distribution, exhibits extensive variation in the study area. Its values evaluated using the Hydrognomon software and maximum likelihood method, vary from about -0.1 near the north-western coast of Latvia in the Baltic Proper up to about 0.05 in the eastern Gulf of Finland. This parameter is very close to zero near Tallinn in the western Gulf of Finland. Thus, it is natural that the Gumbel distribution gives adequate projections of extreme water levels for the vicinity of Tallinn. More importantly, this feature indicates that the use of a single distribution for the projections of extreme water levels and their return periods for the entire Baltic Sea coast is inappropriate. The physical reason is the interplay of the complex shape of large subbasins (such as the Gulf of Riga and Gulf of Finland) of the sea and highly anisotropic wind regime. The 'impact' of this anisotropy on the statistics of water level is amplified by the overall anisotropy of the distributions of the frequency of occurrence of high and low water levels. The most important conjecture is that long-term behaviour of water level extremes in different coastal sections of the Baltic Sea may be fundamentally different.

Geodetic measurements reveal similarities between post-Last Glacial Maximum and present-day mass loss from the Greenland ice sheet.

PubMed

Khan, Shfaqat A; Sasgen, Ingo; Bevis, Michael; van Dam, Tonie; Bamber, Jonathan L; Wahr, John; Willis, Michael; Kjær, Kurt H; Wouters, Bert; Helm, Veit; Csatho, Beata; Fleming, Kevin; Bjørk, Anders A; Aschwanden, Andy; Knudsen, Per; Munneke, Peter Kuipers

2016-09-01

Accurate quantification of the millennial-scale mass balance of the Greenland ice sheet (GrIS) and its contribution to global sea-level rise remain challenging because of sparse in situ observations in key regions. Glacial isostatic adjustment (GIA) is the ongoing response of the solid Earth to ice and ocean load changes occurring since the Last Glacial Maximum (LGM; ~21 thousand years ago) and may be used to constrain the GrIS deglaciation history. We use data from the Greenland Global Positioning System network to directly measure GIA and estimate basin-wide mass changes since the LGM. Unpredicted, large GIA uplift rates of +12 mm/year are found in southeast Greenland. These rates are due to low upper mantle viscosity in the region, from when Greenland passed over the Iceland hot spot about 40 million years ago. This region of concentrated soft rheology has a profound influence on reconstructing the deglaciation history of Greenland. We reevaluate the evolution of the GrIS since LGM and obtain a loss of 1.5-m sea-level equivalent from the northwest and southeast. These same sectors are dominating modern mass loss. We suggest that the present destabilization of these marine-based sectors may increase sea level for centuries to come. Our new deglaciation history and GIA uplift estimates suggest that studies that use the Gravity Recovery and Climate Experiment satellite mission to infer present-day changes in the GrIS may have erroneously corrected for GIA and underestimated the mass loss by about 20 gigatons/year.

Geodetic measurements reveal similarities between post–Last Glacial Maximum and present-day mass loss from the Greenland ice sheet

PubMed Central

Khan, Shfaqat A.; Sasgen, Ingo; Bevis, Michael; van Dam, Tonie; Bamber, Jonathan L.; Wahr, John; Willis, Michael; Kjær, Kurt H.; Wouters, Bert; Helm, Veit; Csatho, Beata; Fleming, Kevin; Bjørk, Anders A.; Aschwanden, Andy; Knudsen, Per; Munneke, Peter Kuipers

2016-01-01

Accurate quantification of the millennial-scale mass balance of the Greenland ice sheet (GrIS) and its contribution to global sea-level rise remain challenging because of sparse in situ observations in key regions. Glacial isostatic adjustment (GIA) is the ongoing response of the solid Earth to ice and ocean load changes occurring since the Last Glacial Maximum (LGM; ~21 thousand years ago) and may be used to constrain the GrIS deglaciation history. We use data from the Greenland Global Positioning System network to directly measure GIA and estimate basin-wide mass changes since the LGM. Unpredicted, large GIA uplift rates of +12 mm/year are found in southeast Greenland. These rates are due to low upper mantle viscosity in the region, from when Greenland passed over the Iceland hot spot about 40 million years ago. This region of concentrated soft rheology has a profound influence on reconstructing the deglaciation history of Greenland. We reevaluate the evolution of the GrIS since LGM and obtain a loss of 1.5-m sea-level equivalent from the northwest and southeast. These same sectors are dominating modern mass loss. We suggest that the present destabilization of these marine-based sectors may increase sea level for centuries to come. Our new deglaciation history and GIA uplift estimates suggest that studies that use the Gravity Recovery and Climate Experiment satellite mission to infer present-day changes in the GrIS may have erroneously corrected for GIA and underestimated the mass loss by about 20 gigatons/year. PMID:27679819

76 FR 23322 - Storage Development Partners, LLC; Notice of Preliminary Permit Application Accepted for Filing...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-26

... total storage capacity of 5,737 acre-feet at a normal maximum operating elevation of 1,600 feet mean sea level (msl); (2) five 9,700-foot-long, 25-foot- diameter steel lined penstocks extending between the... Ocean, serving as the lower reservoir; (4) an underground powerhouse with approximate dimensions of 250...

Predictions of turbidity due to enhanced sediment resuspension resulting from sea-level rise on a fringing Coral Reef: Evidence from Molokai, Hawaii

USGS Publications Warehouse

Ogston, A.S.; Field, M.E.

2010-01-01

Accelerating sea-level rise associated with global climate change will affect sedimentary processes on coral reefs and other shoreline environments by increasing energy and sediment resuspension. On reefs, sedimentation is known to increase coral stress and bleaching as particles that settle on coral surfaces interfere with photosynthesis and feeding, and turbidity induced by suspended sediment reduces incident light levels. Using relationships developed from observations of wave orbital velocity, water-surface elevation, and suspended-sediment concentration on a fringing reef flat of Molokai, Hawaii, predictions of the average daily maximum in suspended-sediment concentration increase from ~11 mg/l to ~20 mg/l with 20 cm sea-level rise. The duration of time concentrations exceeds 10 mg/l increases from 9 to 37. An evaluation of the reduction of wave energy flux through breaking and frictional dissipation across the reef flat shows an increase of ~80 relative to the present will potentially reach the shoreline as sea level increases by 20 cm. Where the shoreline exists on low, flat terrain, the increased energy could cause significant erosion of the shoreline. Considering the sediment budget, the sediment flux is predicted to increase and removal of fine-grained sediment may be expedited on some fringing reefs, and sediment in storage on the inner reef could ultimately be reduced. However, increased shoreline erosion may add sediment and offset removal from the reef flat. The shifts in sediment availability and transport that will occur as result of a modest increase in sea level have wide application to fringing coral reefs elsewhere, as well as other shoreline environments. ?? 2010 the Coastal Education & Research Foundation (CERF).

Sequence stratigraphy of the subaqueous Changjiang (Yangtze River) delta since the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Xu, Taoyu; Wang, Guoqing; Shi, Xuefa; Wang, Xin; Yao, Zhengquan; Yang, Gang; Fang, Xisheng; Qiao, Shuqing; Liu, Shengfa; Wang, Xuchen; Zhao, Quanhong

2016-01-01

This study focuses on sedimentary research at the subaqueous Changjiang (Yangtze River) delta, based on five high-resolution seismic profiles and seven borehole cores with accurate AMS 14C datings. Three distinct seismic units were identified from the seismic profiles according to seismic reflection characteristics, and five sedimentary facies were recognized from borehole cores. These facies constituted a fining upward sedimentary sequence in relation to postglacial sea-level transgression. Three sequence surfaces (sequence boundary (SB), transgressive surface (TS), and maximum flooding surface (MFS)) demarcate the boundaries between early transgressive system tract (E-TST), late transgressive system tract (L-TST), early highstand system tract (E-HST) and late highstand system tract (L-HST), which constitute the sixth order sequence. These system tracts were developed coevally with postglacial sea-level rise. E-TST (~ 19-12 ka BP) corresponds to an incised-valley infilling in the early stages of postglacial transgression whereas L-TST (~ 12-7.5 ka BP) was formed during the last stage of postglacial transgression. The progradational structure of L-TST reflected in seismic profiles is possibly related to the intensification of the East Asian summer monsoon. E-HST (~ 7.5-2 ka BP) was deposited in response to the highstand after maximum postglacial transgression was reached, while L-HST (~ 2 ka BP-present) was initiated by accelerated progradation of the Changjiang delta.

Impacts of abrupt climate changes in the Levant from Last Glacial Dead Sea levels

NASA Astrophysics Data System (ADS)

Torfstein, Adi; Goldstein, Steven L.; Stein, Mordechai; Enzel, Yehouda

2013-06-01

A new, detailed lake level curve for Lake Lisan (the Last Glacial Dead Sea) reveals a high frequency of abrupt fluctuations during Marine Isotope Stage 3 (MIS3) compared to the relatively high stand characterizing MIS2, and the significantly lower Holocene lake. The lake level fluctuations reflect the hydrological conditions in the large watershed of the lake, which in turn reflects the hydro-climatic conditions in the central Levant region. The new curve shows that the fluctuations coincide on millennial timescales with temperature variations recorded in Greenland. Four patterns of correlation are observed through the last ice age: (1) maximum lake elevations were reached during MIS2, the coldest interval; (2) abrupt lake level drops to the lowest elevations coincided with the occurrence of Heinrich (H) events; (3) the lake returned to higher-stand conditions along with warming in Greenland that followed H-events; (4) significant lake level fluctuations coincided with virtually every Greenland stadial-interstadial cycle. Over glacial-interglacial time-scales, Northern Hemisphere glacial cooling induces extreme wetness in the Levant, with high lake levels reaching ˜160 m below mean sea level (mbmsl), approximately 240 m above typical Holocene levels of ˜400 mbmsl. These orbital time-scale shifts are driven by expansions of the European ice sheet, which deflect westerly storm tracks southward to the Eastern Mediterranean, resulting in increased sea-air temperature gradients that invoke increased cyclogenesis, and enhanced moisture delivery to the Levant. The millennial-scale lake level drops associated with Greenland stadials are most extreme during Heinrich stadials and reflect abrupt cooling of the Eastern Mediterranean atmosphere and sea-surface, which weaken the cyclogenic rain engine and cause extreme Levant droughts. During the recovery from the effect of Heinrich stadials, the regional climate configuration resumed typical glacial conditions, with enhanced Levant precipitation and a rise in Lake Lisan levels. Similar cyclicity in the transfer of moisture to the Levant affected lake levels during all of the non-Heinrich stadial-interstadial cycles.

Sea-level rise impacts on the tides of the European Shelf

NASA Astrophysics Data System (ADS)

Idier, Déborah; Paris, François; Cozannet, Gonéri Le; Boulahya, Faiza; Dumas, Franck

2017-04-01

Sea-level rise (SLR) can modify not only total water levels, but also tidal dynamics. Several studies have investigated the effects of SLR on the tides of the western European continental shelf (mainly the M2 component). We further investigate this issue using a modelling-based approach, considering uniform SLR scenarios from -0.25 m to +10 m above present-day sea level. Assuming that coastal defenses are constructed along present-day shorelines, the patterns of change in high tide levels (annual maximum water level) are spatially similar, regardless of the magnitude of sea-level rise (i.e., the sign of the change remains the same, regardless of the SLR scenario) over most of the area (70%). Notable increases in high tide levels occur especially in the northern Irish Sea, the southern part of the North Sea and the German Bight, and decreases occur mainly in the western English Channel. These changes are generally proportional to SLR, as long as SLR remains smaller than 2 m. Depending on the location, they can account for +/-15% of regional SLR. High tide levels and the M2 component exhibit slightly different patterns. Analysis of the 12 largest tidal components highlights the need to take into account at least the M2, S2, N2, M4, MS4 and MN4 components when investigating the effects of SLR on tides. Changes in high tide levels are much less proportional to SLR when flooding is allowed, in particular in the German Bight. However, some areas (e.g., the English Channel) are not very sensitive to this option, meaning that the effects of SLR would be predictable in these areas, even if future coastal defense strategies are ignored. Physically, SLR-induced tidal changes result from the competition between reductions in bed friction damping, changes in resonance properties and increased reflection at the coast, i.e., local and non-local processes. A preliminary estimate of tidal changes by 2100 under a plausible non-uniform SLR scenario (using the RCP4.5 scenario) is provided. Though the changes display similar patterns, the high water levels appear to be sensitive to the non-uniformity of SLR.

Evolution of potentially eroding events along the northern coast of the Iberian Peninsula

NASA Astrophysics Data System (ADS)

Rasilla Álvarez, D.; García Codrón, J. C.

2009-09-01

The anthropogenic global warming is expected to result in a rise in sea-level, accompanied by changes in extreme climate events, such as the frequency and intensity of storms. Such scenario would result in an acceleration of coastal erosion. The aim of the present study is to assess the temporal evolution of potentially eroding events along the northern coast of the Iberian Peninsula during the second half of the 20th century, and to investigate changes in forcing processes such as the frequency and magnitude of storm surges and high wave events. To characterize the potentially eroding events, the total elevation of the water level was selected, being calculated as the sum of the contributions of the average water level, wave run up and the storm surges. Potentially eroding events were identified and quantified following a two-step procedure. Through the first step the potential flood induced by a given storm was estimated by simulating its effects on a theoretical beach profile (intermediate) using an empirical parameterization for extreme run-up approach. The second step consisted on characterizing the maximum storm surge registered during a storm. Those parameters were calculated from hindcasted data (storm surge, wave heights and period, wind speed and direction), retrieved from the SIMAR-44 database (Puertos del Estado), and validated against actual tide gauge measurements and buoy data (RedMar and RedExt networks). Analyses of total water levels showed a long term increase since 1958, resulting from the increase of mean sea level; conversely, a reduction of the frequency and the intensity of the storm events were deduced from the analysis of meteorological records. Since the impact of the storms on macro- and meso- tidal coast closely depend on the tides, a storm impact index was computed taking into account the storm surge magnitude, the wave heights and time duration during which a predefined threshold was exceeded by the sea level. The results are consistent with the analysis of the shoreline evolution on a specific sector of Cantabria (Oyambre) through the comparison of aerial photographs taken between 1957 and 2005. From the late 50´s to late 70’s, the shoreline significantly retreated, in correspondence with the period of maximum storm activity. Conversely, shoreline retreat slowed down during the late 1980s and 1990s while storm activity considerably decreased. Thus long-term coastal erosion, due to the occurrences of high water levels embedded into a long trend term of sea level rise, has been balanced by the reduction of the frequency and intensity of the Atlantic storms. Since relative sea-level will continue rising in the future, most of the coastal morphologies will probably be more frequently reached by the sea, increasing the flooding risk in low-lying sectors and promoting landslides along the cliffs.

Recent advances in the compilation of holocene relative Sea-level database in North America

NASA Astrophysics Data System (ADS)

Horton, B.; Vacchi, M.; Engelhart, S. E.; Nikitina, D.

2015-12-01

Reconstruction of relative sea level (RSL) has implications for investigation of crustal movements, calibration of earth rheology models and the reconstruction of ice sheets. In recent years, efforts were made to create RSL databases following a standardized methodology. These regional databases provided a framework for developing our understanding of the primary mechanisms of RSL change since the Last Glacial Maximum and a long-term baseline against which to gauge changes in sea-level during the 20th century and forecasts for the 21st. Here we present two quality-controlled Holocene RSL database compiled for North America. Along the Pacific coast of North America (British Columbia, Canada to California, USA), our re-evaluation of sea-level indicators from geological and archaeological investigations yield 841 RSL data-points mainly from salt and freshwater wetlands or adjacent estuarine sediment as well as from isolation basin. Along the Atlantic coast of North America (Hudson Bay, Canada to South Carolina, USA), we are currently compiling a database including more than 2000 RSL data-points from isolation basin, salt and freshwater wetlands, beach ridges and intratidal deposits. We outline the difficulties and solutions we made to compile databases in such different depostional environment. We address complex tectonics and the framework to compare such large variability of RSL data-point. We discuss the implications of our results for the glacio-isostatic adjustment (GIA) models in the two studied regions.

Wind-induced circulation in a large tropical lagoon: Chetumal Bay

NASA Astrophysics Data System (ADS)

Palacios, E.; Carrillo, L.

2013-05-01

Chetumal Bay is a large tropical lagoon located at the Mesoamerican Reef System. Windinduced circulation in this basin was investigated by using direct measurements of current, sea level, and 2d barotropic numerical model. Acoustic Doppler Profiler (ADP) transects covering the north of Chetumal Bay during two campaigns September 2006 and March 2007 were used. The 2d barotropic numerical model was ROMs based and wind forced. Wind information was obtained from a meteorological station located at ECOSUR Chetumal. Sea level data was collected from a pressure sensor deployed in the lagoon. A seasonal pattern of circulation was observed. From observations, during September 2006, a northward flow was shown in most part of the bay and a southward flow in the eastern coast was observed with velocities ranged from 6 cm s-1 to 36 cm s-1. In March 2007, the current pattern was more complex; divergences and converges were identified. The dominant circulation was northward in eastern portion, and southward in the central and western zone. The average current speed was 6 cm s-1 with maximum values of 26 -34 cm s-1. During September 2006 predominant wind was easternsoutheastern and during March 2007, northerly wind events were recorded. Sea level amplitude responded quickly to changes in the magnitude and direction of the wind. Results of sea level and circulation from the 2d barotropic numerical model agreed with observations at first approximation.

Efficacy of emamectin benzoate against sea lice infestations of Atlantic salmon, Salmo salar L.: evaluation in the absence of an untreated contemporary control.

PubMed

Gustafson, L; Ellis, S; Robinson, T; Marenghi, F; Endris, R

2006-10-01

The efficacy of emamectin benzoate (SLICE) against sea lice infestations of Atlantic salmon, Salmo salar L., is typically assessed using untreated fish, or fish treated with alternative therapeutants, as controls. The State of Maine, USA, is currently under active management for the OIE-notifiable pathogen, infectious salmon anaemia virus (ISAV); consequently, neither control group is feasible in this region. Untreated salmon risk extensive damage from the ectoparasites, and threaten to increase vector-borne exposure or susceptibility of farms to ISAV; and the only treatment presently available in Maine is SLICE. However, because sea lice infestations are unlikely to resolve spontaneously, and response to treatment occurs within weeks, use of a pretreatment baseline is a reasonable alternative for confirmatory studies. We evaluated SLICE efficacy on Atlantic salmon farms in Cobscook Bay 2002-2005, in the absence of untreated controls, using pretreatment lice loads as a reference for calculation. Maximum efficacy ranged from 68% to 100% reduction from initial levels. Time-to-maximum efficacy ranged from 1 to 8 weeks after treatment initiation. Efficacy duration, measured between first reduction and first progressive rise in counts, ranged from 4 to 16 weeks.

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.

The changing seascape of Galway Bay, Western Ireland

NASA Astrophysics Data System (ADS)

Mc Cullagh, D.; Benetti, S.; Plets, R. M. K.; Edwards, R.

2016-12-01

During the late Quaternary significant environmental and relative sea-level variations have contributed to shaping present day coastlines. This is particularly evident along formerly glaciated continental margins. Strong evidence of these changes are recorded in Galway Bay, Western Ireland. This research uses a multidisciplinary approach. Seismic and multibeam data, sedimentological, micropaleontological, geochemical analysis and 15 radiocarbon dates of sediment cores from the bay provide post last glacial maximum (LGM) sea level and environmental reconstructions for the region. The acoustic stratigraphy of the bay includes 3 seismic units: the deepest unit represents the acoustic basement, composed of limestone and granite bedrock; the middle unit is composed of the oldest preserved sediments, deposited during and after the LGM, and interpreted to be glacial till. The uppermost unit represents deposition and reworking after glacial retreat. The erosive action of the ice sheet that extended off the Irish coast is thought to be responsible for the removal and reworking of all sediments older that the LGM. In the sediment cores, three main lithofacies were identified: 1) a sandy silt and clay facies, 2) a distinct shell hash interlayer and, 3) a fine silty sand facies. These 3 facies are found within the uppermost seismic unit, and initial radiocarbon dating of shells in 4 cores, constrain these sediments and the uppermost seismic unit to the Holocene. Preliminary qualitative analysis on foraminifera from several cores shows a general trend of progression from estuarine to open marine conditions, inferred from indicator species. This trend is supported by X-ray fluorescence (XRF) analysis which shows increased ratios of Cl/Fe in younger deposits. Constraining dates on sea level variations in the region will be added to the sea level database for Ireland and possibly used to adjust the existing relative sea level models. These are important for understating past sea level variations and modelling future trends.

Evidence from the Seychelles of Last Interglacial Sea Level Oscillations

NASA Astrophysics Data System (ADS)

Vyverberg, K.; Dutton, A.; Dechnik, B.; Webster, J.; Zwartz, D.

2014-12-01

Several studies indicate that sea level oscillated during Marine Isotope Stage (MIS) 5e, but the details of these scenarios, including the number of sea level oscillations, are still debated. We lack a detailed understanding of the sensitivity of the large polar ice sheets to changes in temperature that could result in eustatic sea level oscillations. Because the Seychelles are located far from the margins of the Last Glacial Maximum northern hemisphere ice sheets, they have not been subjected to glacial isostatic adjustment, and have been tectonically stable since the Last Interglacial period; therefore, they provide a robust record of eustatic sea level during MIS 5e. All of the outcrops we examined contain unconformities and/or sharp transitions between facies, though the nature of these boundaries varies between sites. In some outcrops we observed a hardground comprising fine-grained, mollusc-rich sediment layer between distinct generations of in situ coralgal framework. In one outcrop, this succession was observed twice, where two generations of reef growth were each capped by a strongly indurated fine-grained, mollusc-rich sediment layer. At the site with the greatest vertical extent of outcrop, there is a marked difference in the taxonomic composition of the coral community above and below an unconformable surface, but the indurated fine-grained, sediment layer observed elsewhere was absent. Most of the other outcrops we studied contained a common succession of facies from in situ reef units overlain by cemented coral rubble. In two dated outcrops, the age of corals above and below the rubble layer are the same age. The hardgrounds and rubble layers may represent ephemeral exposure of the reef units during two drops in sea level. The inference of multiple meter-scale oscillations during the MIS 5e highstand indicates a more dynamic cryosphere than the present interglacial, although the climatic threshold for more volatile polar ice sheets is not yet clear.

δ18O and salinity variability from the Last Glacial Maximum to Recent in the Bay of Bengal and Andaman Sea

NASA Astrophysics Data System (ADS)

Sijinkumar, A. V.; Clemens, Steven; Nath, B. Nagender; Prell, Warren; Benshila, Rachid; Lengaigne, Matthieu

2016-03-01

Oxygen isotopes of surface, thermocline and bottom dwelling foraminifera were analysed from two well-dated Andaman Sea cores and combined with nine previously published records from the Bay of Bengal (BoB) and Andaman Sea to create a transect spanning 20°N to 5°N. Combined with temperature estimates and the observed seawater δ18O-salinity relationship, these data are used to estimate past changes in BoB salinity structure. Compared to modern, mid-Holocene (9-6 cal ka BP) surface waters in the northern BoB were 2.5 psμ (8%) fresher, Andaman Sea were 3.8 psμ (12%) fresher, and southern BoB were 1.2 psμ (3.5%) fresher. Conversely, during the last glacial maximum (LGM), surface waters in the northern BoB were 2.9 psμ (9%) more saline while Andaman Sea were essentially unchanged and southern BoB were 1.7 psμ (4.9%) more saline compared to modern. The relative freshness of the Andaman during the last glacial maximum is likely the result of basin morphology during sea level low stand, resulting in reduced surface water mixing with the open BoB as well as shelf emergence, causing increased proximity of the core locations to river outflow. Sensitivity experiments using a regional ocean model indicate that the increased mid-Holocene north to south (20°N to 5°N) salinity gradient can be achieved with a ∼50% increase in precipitation/runoff while the decreased glacial age gradient can be achieved with a ∼50% reduction in precipitation/runoff. During the deglaciation, both surface and thermocline-dwelling species in the Andaman and northern BoB exhibit depleted δ18O within the Younger Dryas (YD), indicating colder and/or more saline conditions. None of the records from the southern BoB site have clear YD structure, possibly due to the combined effects of bioturbation and low sedimentation rates.

Phytoplankton response to the contrasting physical regimes in the eastern Arabian Sea during north east monsoon

NASA Astrophysics Data System (ADS)

Chndrasekhararao, A. V.; Kurian, Siby; Vidya, P. J.; Gauns, Mangesh; Shenoy, Damodar M.; Mulla, Amara; Naik, Hema; Reddy, T. Venugopal; Naqvi, S. W. A.

2018-06-01

Phytoplankton abundance and composition in two contrasting physical regimes - convective mixing in the northeastern Arabian Sea (NEAS) and Arabian Sea mini warm pool (ASMWP) in the southeastern Arabian Sea (SEAS) - were investigated during the northeast monsoon (NEM) of 2015 and 2017. Observations in 2015 were carried out late during the season, and only one station in the north (at 21°N latitude) fell within the zone of convective mixing where microplankton was dominated by diatoms. In 2017, convective mixing occurred even at 16°N latitude, but the microplankton contribution was low, presumably due to low Si/N ratios. Within the convective mixing regime of the NEAS, chlorophyll (Chl) a concentrations were higher in 2015 (maximum 1080 ng L-1; average 493 ng L-1) than in 2017 (maximum 673 ng L-1; average 263 ng L-1). In contrast, picophytoplankton were dominant in the ASMWP of the SEAS with peak abundance associated with the subsurface chlorophyll maximum. A warm core eddy was present in 2015 in the SEAS where four times higher Prochlorococcus counts were found within the core of the eddy than at its periphery. This study provides the first description of the phytoplankton community in the ASMWP. Our results clearly demonstrate phytoplankton response to the contrasting physical conditions, highlighting the role of bio-physical coupling in the productivity of the Arabian Sea.

Biogeochemical control of marine productivity in the Mediterranean Sea during the last 50 years

PubMed Central

Macias, Diego; Garcia-Gorriz, Elisa; Piroddi, Chiara; Stips, Adolf

2014-01-01

The temporal dynamics of biogeochemical variables derived from a coupled 3-D model of the Mediterranean Sea are evaluated for the last 50 years (1960–2010) against independent data on fisheries catch per unit effort (CPUE) for the same time period. Concordant patterns are found in the time series of all of the biological variables (from the model and from fisheries statistics), with low values at the beginning of the series, a later increase, with maximum levels reached at the end of the 1990s, and a posterior stabilization. Spectral analysis of the annual biological time series reveals coincident low-frequency signals in all of them. The first, more energetic signal peaks around the year 2000, while the second, less energetic signal peaks near 1982. Almost identical low-frequency signals are found in the nutrient loads of the rivers and in the integrated nutrient levels in the surface marine ecosystem. Nitrate concentration shows a maximum level in 1998, with a later stabilization to present-day values, coincident with the first low-frequency signal found in the biological series. Phosphate shows maximum concentrations around 1982 and a posterior sharp decline, in concordance with the second low-frequency signal observed in the biological series. That result seems to indicate that the control of marine productivity (plankton to fish) in the Mediterranean is principally mediated through bottom-up processes that could be traced back to the characteristics of riverine discharges. The high sensitivity of CPUE time series to environmental conditions might be another indicator of the overexploitation of this marine ecosystem. Key Points Biogeochemical evolution of the Mediterranean over the past 50 years River nutrient loads drive primary and secondary productions Strong link between low trophic levels and fisheries PMID:26180286

Parallel Computation of Ocean-Atmosphere-Wave Coupled Storm Surge Model

NASA Astrophysics Data System (ADS)

Kim, K.; Yamashita, T.

2003-12-01

Ocean-atmosphere interactions are very important in the formation and development of tropical storms. These interactions are dominant in exchanging heat, momentum, and moisture fluxes. Heat flux is usually computed using a bulk equation. In this equation air-sea interface supplies heat energy to the atmosphere and to the storm. Dynamical interaction is most often one way in which it is the atmosphere that drives the ocean. The winds transfer momentum to both ocean surface waves and ocean current. The wind wave makes an important role in the exchange of the quantities of motion, heat and a substance between the atmosphere and the ocean. Storm surges can be considered as the phenomena of mean sea-level changes, which are the result of the frictional stresses of strong winds blowing toward the land and causing the set level and the low atmospheric pressure at the centre of the cyclone can additionally raise the sea level. In addition to the rise in water level itself, another wave factor must be considered. A rise of mean sea level due to white-cap wave dissipation should be considered. In bounded bodies of water, such as small seas, wind driven sea level set up is much serious than inverted barometer effects, in which the effects of wind waves on wind-driven current play an important role. It is necessary to develop the coupled system of the full spectral third-generation wind-wave model (WAM or WAVEWATCH III), the meso-scale atmosphere model (MM5) and the coastal ocean model (POM) for simulating these physical interactions. As the component of coupled system is so heavy for personal usage, the parallel computing system should be developed. In this study, first, we developed the coupling system of the atmosphere model, ocean wave model and the coastal ocean model, in the Beowulf System, for the simulation of the storm surge. It was applied to the storm surge simulation caused by Typhoon Bart (T9918) in the Yatsushiro Sea. The atmosphere model and the ocean model have been made the parallel codes by SPMD methods. The wave-current interface model was developed by defining the wave breaking stresses. And we developed the coupling program to collect and distribute the exchanging data with the parallel system. Every models and coupler are executed at same time, and they calculate own jobs and pass data with organic system. MPMD method programming was performed to couple the models. The coupler and each models united by the separated group, and they calculated by the group unit. Also they passed message when exchanging data by global unit. The data are exchanged every 60-second model time that is the least common multiple time of the atmosphere model, the wave model and the ocean model. The model was applied to the storm surge simulation in the Yatsushiro Sea, in which we could not simulated the observed maximum surge height with the numerical model that did not include the wave breaking stress. It is confirmed that the simulation which includes the wave breaking stress effects can produce the observed maximum height, 450 cm, at Matsuai.

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.

Middle Holocene thermal maximum in eastern Beringia

NASA Astrophysics Data System (ADS)

Kaufman, D. S.; Bartlein, P. J.

2015-12-01

A new systematic review of diverse Holocene paleoenvironmental records (Kaufman et al., Quat. Sci. Rev., in revision) has clarified the primary multi-centennial- to millennial-scale trends across eastern Beringia (Alaska, westernmost Canada and adjacent seas). Composite time series from midges, pollen, and biogeochemical indicators are compared with new summaries of mountain-glacier and lake-level fluctuations, terrestrial water-isotope records, sea-ice and sea-surface-temperature analyses, and peatland and thaw-lake initiation frequencies. The paleo observations are also compared with recently published simulations (Bartlein et al., Clim. Past Discuss., 2015) that used a regional climate model to simulate the effects of global and regional-scale forcings at 11 and 6 ka. During the early Holocene (11.5-8 ka), rather than a prominent thermal maximum as suggested previously, the newly compiled paleo evidence (mostly sensitive to summer conditions) indicates that temperatures were highly variable, at times both higher and lower than present, although the overall lowest average temperatures occurred during the earliest Holocene. During the middle Holocene (8-4 ka), glaciers retreated as the regional average temperature increased to a maximum between 7 and 5 ka, as reflected in most proxy types. The paleo evidence for low and variable temperatures during the early Holocene contrasts with more uniformly high temperatures during the middle Holocene and agrees with the climate simulations, which show that temperature in eastern Beringia was on average lower at 11 ka and higher at 6 ka than at present (pre-industrial). Low temperatures during the early Holocene can be attributed in part to the summer chilling caused by flooding the continental shelves, whereas the mid-Holocene thermal maximum was likely driven by the loss of the Laurentide ice sheet, rise in greenhouse gases, higher-than-present summer insolation, and expansion of forest over tundra.

The climate response of the Indo-Pacific warm pool to glacial sea level

NASA Astrophysics Data System (ADS)

Di Nezio, Pedro N.; Timmermann, Axel; Tierney, Jessica E.; Jin, Fei-Fei; Otto-Bliesner, Bette; Rosenbloom, Nan; Mapes, Brian; Neale, Rich; Ivanovic, Ruza F.; Montenegro, Alvaro

2016-06-01

Growing climate proxy evidence suggests that changes in sea level are important drivers of tropical climate change on glacial-interglacial timescales. These paleodata suggest that rainfall patterns over the Indo-Pacific warm pool (IPWP) are highly sensitive to the landmass configuration of the Maritime Continent and that lowered sea level contributed to large-scale drying during the Last Glacial Maximum (LGM, approximately 21,000 years B.P.). Using the Community Earth System Model Version 1.2 (CESM1), we investigate the mechanisms by which lowered sea level influenced the climate of the IPWP during the LGM. The CESM1 simulations show that, in agreement with previous hypotheses, changes in atmospheric circulation are initiated by the exposure of the Sunda and Sahul shelves. Ocean dynamical processes amplify the changes in atmospheric circulation by increasing the east-west sea surface temperature (SST) gradient along the equatorial Indian Ocean. The coupled mechanism driving this response is akin to the Bjerknes feedback and results in a large-scale climatic reorganization over the Indian Ocean with impacts extending from east Africa to the western tropical Pacific. Unlike exposure of the Sunda shelf, exposure of Sahul shelf and the associated changes in surface albedo play a key role because of the positive feedback. This mechanism could explain the pattern of dry (wet) eastern (western) Indian Ocean identified in climate proxies and LGM simulations. However, this response also requires a strengthened SST gradient along the equatorial Indian Ocean, a pattern that is not evident in marine paleoreconstructions. Strategies to resolve this issue are discussed.

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.

Joint use of long water pipe tiltmeters and sea level gauges for monitoring ground deformation at Campi Flegrei caldera

NASA Astrophysics Data System (ADS)

Scarpa, Roberto; Capuano, Paolo; Tammaro, Umberto; Bilham, Roger

2014-05-01

The Campi Flegrei caldera, located in the Campanian Plain, Southern Italy, 15 km west of the city of Naples, is a nested, resurgent, and restless structure in the densely inhabited Neapolitan area. The main caldera at Campi Flegrei is 12 - 15 km across and its rim is thought to have been formed during the catastrophic eruption, occurred 39 ky ago ca., which produced a deposit referred to as the Campanian Ignimbrite. The volcanic hazards posed by this caldera and the related risk are extremely high, because of its explosive character and the about 1.5 million people living within the caldera. Campi Flegrei area periodically experiences significant unrest episodes which include ground deformations, the so-called 'bradisismo'. Following the last eruption (Monte Nuovo, 1538) a general subsidence has been interrupted by episodes of uplift, the most recent of which occurred in 1970-72 and 1982-84. Since 1950 the caldera is showing signs of unrest with ground uplift, seismicity, and composition variation of fumarole fluids. In particular, subsidence has been replaced by intermittent episodes of inflation with short time duration and various maximum amplitude. They occurred in 1989, 1994, 2000, 2005-06, 2008-09 and 2011-2014 with duration of few months and maximum amplitude ranging between 3 and 18 cm., approximately. In the last years an array of water-pipe tiltmeters with lengths between 28 m and 278 m in tunnels on the flanks of the region of maximum inflation has been installed to avoid problems common to the traditional tiltmeters. The tiltmeters record inflation episodes upon which are superimposed local load tides and the effects of the seiches in the Bay of Naples and in the Tyrrhenian sea. We use data recorded by three tide gauges in the Bay of Pozzuoli (Pozzuoli, Miseno, Nisida) to compare water pipe data with sea level to extract astronomical tidal components (diurnal and semidiurnal) and seiches periods (particularly between 20 minutes and 56 minutes) that could constitute local loading frequencies recorded clearly by tide gauges and tiltmeters. We perform an analysis of the amplitude stability of seiches amplitudes. After the removal of the tides and seiches component we compare tilt residual and sea level trend for the same periods of time. The comparison between these two kind of data enables a more sensitive definition of the low level uplift with an accuracy of 1% for nanoradiant tilts in the period range 10 minutes to 10 hours with a long term tilt stability of approximately 0.1 microradiant/yr.

A Bayesian Network to Predict Barrier Island Geomorphologic Characteristics

NASA Astrophysics Data System (ADS)

Gutierrez, B.; Plant, N. G.; Thieler, E. R.; Turecek, A.; Stippa, S.

2014-12-01

Understanding how barrier islands along the Atlantic and Gulf coasts of the United States respond to storms and sea-level rise is an important management concern. Although these threats are well recognized, quantifying the integrated vulnerability is challenging due to the range of time and space scalesover which these processes act. Developing datasets and methods to identify the physical vulnerabilities of coastal environments due to storms and sea-level rise thus is an important scientific focus that supports land management decision making. Here we employ a Bayesian Network (BN) to model the interactions between geomorphic variables sampled from existing datasets that capture both storm-and sea-level rise related coastal evolution. The BN provides a means of estimating probabilities of changes in specific geomorphic characteristics such as foredune crest height, beach width, beach height, given knowledge of barrier island width, maximum barrier island elevation, distance from an inlet, the presence of anthropogenic modifications, and long-term shoreline change rates, which we assume to be directly related to sea-level rise. We evaluate BN skill and explore how different constraints, such as shoreline change characteristics (eroding, stable, accreting), distance to nearby inlets and island width, affect the probability distributions of future morphological characteristics. Our work demonstrates that a skillful BN can be constructed and that factors such as distance to inlet, shoreline change rate, and the presence of human alterations have the strongest influences on network performance. For Assateague Island, Maryland/Virginia, USA, we find that different shoreline change behaviors affect the probabilities of specific geomorphic characteristics, such as dune height, which allows us to identify vulnerable locations on the barrier island where habitat or infrastructure may be vulnerable to storms and sea-level rise.

On the rate and causes of twentieth century sea-level rise.

PubMed

Miller, Laury; Douglas, Bruce C

2006-04-15

Both the rate and causes of twentieth century global sea-level rise (GSLR) have been controversial. Estimates from tide-gauges range from less than one, to more than two millimetre yr(-1). In contrast, values based on the processes mostly responsible for GSLR-mass increase (from mountain glaciers and the great high latitude ice masses) and volume increase (expansion due to ocean warming)-fall below this range. Either the gauge estimates are too high, or one (or both) of the component estimates is too low. Gauge estimates of GSLR have been in dispute for several decades because of vertical land movements, especially due to glacial isostatic adjustment (GIA). More recently, the possibility has been raised that coastal tide-gauges measure exaggerated rates of sea-level rise because of localized ocean warming. Presented here are two approaches to a resolution of these problems. The first is morphological, based on the limiting values of observed trends of twentieth century relative sea-level rise as a function of distance from the centres of the ice loads at last glacial maximum. This observational approach, which does not depend on a geophysical model of GIA, supports values of GSLR near 2 mm yr(-1). The second approach involves an analysis of long records of tide-gauge and hydrographic (in situ temperature and salinity) observations in the Pacific and Atlantic Oceans. It was found that sea-level trends from tide-gauges, which reflect both mass and volume change, are 2-3 times higher than rates based on hydrographic data which reveal only volume change. These results support those studies that put the twentieth century rate near 2 mm yr(-1), thereby indicating that mass increase plays a much larger role than ocean warming in twentieth century GSLR.

How sea level change mediates genetic divergence in coastal species across regions with varying tectonic and sediment processes.

PubMed

Dolby, Greer A; Ellingson, Ryan A; Findley, Lloyd T; Jacobs, David K

2018-02-01

Plate tectonics and sediment processes control regional continental shelf topography. We examine the genetic consequences of how glacial-associated sea level change interacted with variable nearshore topography since the last glaciation. We reconstructed the size and distribution of areas suitable for tidal estuary formation from the last glacial maximum, ~20 thousand years ago, to present from San Francisco, California, USA (~38°N) to Reforma, Sinaloa, Mexico (~25°N). We assessed range-wide genetic structure and diversity of three codistributed tidal estuarine fishes (California Killifish, Shadow Goby, Longjaw Mudsucker) along ~4,600 km using mitochondrial control region and cytB sequence, and 16-20 microsatellite loci from a total of 524 individuals. Results show that glacial-associated sea level change limited estuarine habitat to few, widely separated refugia at glacial lowstand, and present-day genetic clades were sourced from specific refugia. Habitat increased during postglacial sea level rise and refugial populations admixed in newly formed habitats. Continental shelves with active tectonics and/or low sediment supply were steep and hosted fewer, smaller refugia with more genetically differentiated populations than on broader shelves. Approximate Bayesian computation favoured the refuge-recolonization scenarios from habitat models over isolation by distance and seaway alternatives, indicating isolation at lowstand is a major diversification mechanism among these estuarine (and perhaps other) coastal species. Because sea level change is a global phenomenon, we suggest this top-down physical control of extirpation-isolation-recolonization may be an important driver of genetic diversification in coastal taxa inhabiting other topographically complex coasts globally during the Mid- to Late Pleistocene and deeper timescales. © 2018 John Wiley & Sons Ltd.

Postglacial relative sea-level history of the Prince Rupert area, British Columbia, Canada

NASA Astrophysics Data System (ADS)

Letham, Bryn; Martindale, Andrew; Macdonald, Rebecca; Guiry, Eric; Jones, Jacob; Ames, Kenneth M.

2016-12-01

This paper presents a history of relative sea level (RSL) change for the last 15,000 years in the Prince Rupert region on the northern coast of British Columbia, Canada. One hundred twenty-three radiocarbon ages of organic material from isolation basin cores, sediment sequence exposures, and archaeological sites having a recognized relation to past sea levels constrain postglacial RSL. The large number of new measurements relating to past sea-level provides a well constrained RSL curve that differs in significant ways from previously published results. After deglaciation following the Last Glacial Maximum, the region experienced an isostatically-induced rapid RSL drop from as much 50 m asl to as low as -6.3 m asl in as little as a few centuries between 14,500 BP and 13,500 BP. After a lowstand below current sea level for about 2000 years during the terminal Pleistocene, RSL rose again to a highstand at least 6 m asl after the end of the Younger Dryas. RSL slowly dropped through the Holocene to close to its current position by 2000-1500 BP, with some potential fluctuations between 3500 and 1500 BP. This study highlights variation in RSL histories across relatively short distances, which must be accounted for by local RSL reconstructions such as this one. This RSL curve aided in the identification of an 8000-9000 year old archaeological site on a 10-12 m asl terrace, which is currently the earliest dated archaeological site in the area, and it provides guidance for searching for even older archaeological remains. We highlight the utility and potential of this refined RSL history for developing surveys for other archaeological sites associated with paleoshorelines.

Elucidating the Holocene Relative Sea-Level History of the US Atlantic Coast

NASA Astrophysics Data System (ADS)

Engelhart, S. E.; Anderson, C.; Hill, D.; Horton, B. P.; Peltier, W. R.; van de Plassche, O.; Shennan, I.; Thieler, E. R.; Tornqvist, T. E.

2007-12-01

There is an urgent need for a re-assessment of the quality of Holocene relative sea-level (RSL) observations from the Atlantic and Gulf coasts of the United States. Holocene RSL data provide an essential benchmark to compare against other records of RSL change in the last 100-150 years. Only high quality sea-level data reveal spatial and temporal variations in crustal movements since the Last Glacial Maximum and provide a vital constraint upon dynamical models of the Glacial Isostatic Adjustment (GIA) process. We require an accurate model of the GIA process to inform the global data set currently being produced on the time dependence of the gravitational field of the planet by the Gravity Recovery and Climate Experiment (GRACE). We have compiled database of 1400 possible sea-level index points for the Atlantic coast of the United States. These unvalidated data contain much scatter due to concepts inherent in their original interpretation. They rarely allow for other factors such as sediment compaction and tidal range variation. Following validation, results from Delaware and North Carolina show a rapid rise in RSL from the early to mid Holocene, with no evidence of sea- level above present. They also differ somewhat from GIA model predictions. Rates of RSL change during the late Holocene divide into three broad zones: (1) Maine to Boston, MA ~ RSL rise of less than 1 mm yr-1; (2) Cape Cod, MA to Maryland ~ RSL rise between 1 and 3 mm yr-1; and (3) North Carolina to South Carolina ~ RSL rise less than 1 mm yr-1. Comparison with tide-gauge records demonstrate an increase of at least 1 mm yr-1 at all sites since AD 1900.

Arctic Dinoflagellate Migration Marks the Oligocene Glacial Maximum: Implications for the Rupelian-Chattian Boundary

NASA Astrophysics Data System (ADS)

van Simaeys, S.; Brinkhuis, H.; Pross, J.; Williams, G. L.; Zachos, J. C.

2004-12-01

Various geochemical and biotic climate proxies, and notably deep-sea benthic foraminiferal δ 18O records indicate that the Eocene 'greenhouse' state of the Earth gradually evolved towards an earliest Oligocene 'icehouse' state, eventually triggering the abrupt appearance of large continental ice-sheets on Antarctic at ˜33.3 Ma (Oi-1 event). This, however, was only the first of two major glacial events in the Oligocene. Benthic foraminiferal δ 18O records show a second positive excursion in the mid Oligocene, consistent with a significant ice-sheet expansion and/or cooling at 27.1 Ma (Oi-2b) coincident with magnetosubchron C9n. Here, we report on a mid Oligocene, globally synchronous, Arctic dinoflagellate migration event, calibrated against the upper half of C9n. A sudden appearance, and abundance increases of the Arctic taxon Svalbardella at lower-middle latitudes coincides with the so-called Oi-2b benthic δ 18O event, dated at ˜27.1 Ma. This phenomenon is taken to indicate significant high-latitude surface water cooling, concomitant Antarctic ice-sheet growth, and sea level lowering. The duration of the Svalbardella migrations, and the episode of profound cooling is estimated as ˜500 ka, and is here termed the Oligocene Glacial Maximum (OGM). Our records suggest a close link between the OGM, sea-level fall, and the classic Rupelian-Chattian boundary, magnetostratigraphically dating this boundary as ˜27.1 Ma.

76 FR 26280 - Vermont Marble Power Division of Omya Inc.; Notice of Application Accepted for Filing, Soliciting...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-06

...); (6) an additional steel structure measuring 28 by 48 feet attached to the original powerhouse... maximum water surface elevation of 469.5 feet mean sea level (M.S.L); (3) a gated-forebay intake structure...: A 9-foot- diameter, 460-foot-long, riveted steel penstock that decreases to 8 feet diameter; and a 7...

BOREAS AES READAC Surface Meteorological Data

NASA Technical Reports Server (NTRS)

Atkinson, G. Barrie; Funk, Barry; Hall, Forrest G. (Editor); Knapp, David E. (Editor)

2000-01-01

Canadian AES personnel collected and processed data related to surface atmospheric meteorological conditions over the BOREAS region. This data set contains 15-minute meteorological data from one READAC meteorology station in Hudson Bay, Saskatchewan. Parameters include day, time, type of report, sky condition, visibility, mean sea level pressure, temperature, dewpoint, wind, altimeter, opacity, minimum and maximum visibility, station pressure, minimum and maximum air temperature, a wind group, precipitation, and precipitation in the last hour. The data were collected non-continuously from 24-May-1994 to 20-Sep-1994. The data are provided in tabular ASCII files, and are classified as AFM-Staff data.

Luminescence dating of paleolake deltas and glacial deposits in Garwood Valley, Antarctica: Implications for climate, Ross ice sheet dynamics, and paleolake duration

USGS Publications Warehouse

Levy, Joseph S.; Rittenour, Tammy M.; Fountain, Andrew G.; O'Connor, Jim E.

2017-01-01

The formation of perched deltas and other lacustrine deposits in the McMurdo Dry Valleys of Antarctica is widely considered to be evidence of valley-filling lakes dammed by the grounded Ross Sea ice sheet during the local Last Glacial Maximum, with lake drainage interpreted as a record of grounding line retreat. We used luminescence dating to determine the age of paleolake deltas and glacial tills in Garwood Valley, a coastal dry valley that opens to the Ross Sea. Luminescence ages are stratigraphically consistent with radiocarbon results from algal mats within the same delta deposits but suggest radiocarbon dates from lacustrine carbonates may overestimate deposit ages by thousands of years. Results suggest that late Holocene delta deposition into paleolake Howard in Garwood Valley persisted until ca. 3.5 ka. This is significantly younger than the date when grounded ice is thought to have retreated from the Ross Sea. Our evidence suggests that the local, stranded ice-cored till topography in Garwood Valley, rather than regional ice-sheet dynamics, may have controlled lake levels for some McMurdo Dry Valleys paleolakes. Age control from the supraglacial Ross Sea drift suggests grounding and up-valley advance of the Ross Sea ice sheet into Garwood valley during marine oxygen isotope stage (MIS) 4 (71–78 ka) and the local Last Glacial Maximum (9–10 ka). This work demonstrates the power of combining luminescence dating with existing radiocarbon data sets to improve understanding of the relationships among paleolake formation, glacial position, and stream discharge in response to climate change.

Hearing in the Juvenile Green Sea Turtle (Chelonia mydas): A Comparison of Underwater and Aerial Hearing Using Auditory Evoked Potentials

PubMed Central

Piniak, Wendy E. D.; Mann, David A.; Harms, Craig A.; Jones, T. Todd; Eckert, Scott A.

2016-01-01

Sea turtles spend much of their life in aquatic environments, but critical portions of their life cycle, such as nesting and hatching, occur in terrestrial environments, suggesting that it may be important for them to detect sounds in both air and water. In this study we compared underwater and aerial hearing sensitivities in five juvenile green sea turtles (Chelonia mydas) by measuring auditory evoked potential responses to tone pip stimuli. Green sea turtles detected acoustic stimuli in both media, responding to underwater stimuli between 50 and 1600 Hz and aerial stimuli between 50 and 800 Hz, with maximum sensitivity between 200 and 400 Hz underwater and 300 and 400 Hz in air. When underwater and aerial hearing sensitivities were compared in terms of pressure, green sea turtle aerial sound pressure thresholds were lower than underwater thresholds, however they detected a wider range of frequencies underwater. When thresholds were compared in terms of sound intensity, green sea turtle sound intensity level thresholds were 2–39 dB lower underwater particularly at frequencies below 400 Hz. Acoustic stimuli may provide important environmental cues for sea turtles. Further research is needed to determine how sea turtles behaviorally and physiologically respond to sounds in their environment. PMID:27741231

Hearing in the Juvenile Green Sea Turtle (Chelonia mydas): A Comparison of Underwater and Aerial Hearing Using Auditory Evoked Potentials.

PubMed

Piniak, Wendy E D; Mann, David A; Harms, Craig A; Jones, T Todd; Eckert, Scott A

2016-01-01

Sea turtles spend much of their life in aquatic environments, but critical portions of their life cycle, such as nesting and hatching, occur in terrestrial environments, suggesting that it may be important for them to detect sounds in both air and water. In this study we compared underwater and aerial hearing sensitivities in five juvenile green sea turtles (Chelonia mydas) by measuring auditory evoked potential responses to tone pip stimuli. Green sea turtles detected acoustic stimuli in both media, responding to underwater stimuli between 50 and 1600 Hz and aerial stimuli between 50 and 800 Hz, with maximum sensitivity between 200 and 400 Hz underwater and 300 and 400 Hz in air. When underwater and aerial hearing sensitivities were compared in terms of pressure, green sea turtle aerial sound pressure thresholds were lower than underwater thresholds, however they detected a wider range of frequencies underwater. When thresholds were compared in terms of sound intensity, green sea turtle sound intensity level thresholds were 2-39 dB lower underwater particularly at frequencies below 400 Hz. Acoustic stimuli may provide important environmental cues for sea turtles. Further research is needed to determine how sea turtles behaviorally and physiologically respond to sounds in their environment.

Sea Water Characterization at Ujung Kulon Coastal Depth as Raw Water Source for Desalination and Potential Energy

NASA Astrophysics Data System (ADS)

Mugisidi, Dan; Heriyani, Okatrina

2018-02-01

Fresh water is basic need for life while the source is limited. Therefore, sea water is used as fresh water through desalination process. Sea water has different physical and chemical properties ranging from the surface to the seabed. The energy potential that can be obtained from the hydrostatic pressure also changes according to the depth. As part of the research of the utilization of sea water into fresh water, the aim of this study is to know the characteristics of sea water in the depth that can be utilized as source of fresh water. The sea water samples were taken at 11km from Ujung Kulon beach with depth of 0m, 20m, 40m, 60m, 80m, and 100m under the surface. The results showed that the physical properties at every depth were below the maximum allowable drinking water except for the amount of dissolved solids. Chemical characteristics at any depth above allowable level were fluoride, hardness (CaCo3), chloride, sodium, sulphate, and (KMnO4). In addition to the properties, pressure is one of the considerations in this study to determine the depth of sea water as sources for desalination. Pressure increased by 36.11% as the depth of the sea increased.

A Description of Methodologies Used in Estimation of A-Weighted Sound Levels for FAA Advisory Circular AC-36-3B.

DTIC Science & Technology

1982-01-01

second) Dia propeller diameter (expressed in inches) T°F air temperature in degrees Farenheit T°C air temperature in degrees Celsius T:dBA total dBA...eMpiriC31 function to the absolute noise level ordinate. The term 240 log ( MH is the most sensitive and important part of the equation. The constant (240...standard day, zero wind, dry, zero gradient runway, at a sea level airport. 2. All aircraft operate at maximum takeoff gross weight. 3. All aircraft climb

Global warming related transient albedo feedback in the Arctic and its relation to the seasonality of sea ice

NASA Astrophysics Data System (ADS)

Andry, Olivier; Bintanja, Richard; Hazeleger, Wilco

2015-04-01

The Arctic is warming two to three times faster than the global average. Arctic sea ice cover is very sensitive to this warming and has reached historic minima in late summer in recent years (i.e. 2007, 2012). Considering that the Arctic Ocean is mainly ice-covered and that the albedo of sea ice is very high compared to that of open water, the change in sea ice cover is very likely to have a strong impact on the local surface albedo feedback. Here we quantify the temporal changes in surface albedo feedback in response to global warming. Usually feedbacks are evaluated as being representative and constant for long time periods, but we show here that the strength of climate feedbacks in fact varies strongly with time. For instance, time series of the amplitude of the surface albedo feedback, derived from future climate simulations (CIMP5, RCP8.5 up to year 2300) using a kernel method, peaks around the year 2100. This maximum is likely caused by an increased seasonality in sea-ice cover that is inherently associated with sea ice retreat. We demonstrate that the Arctic average surface albedo has a strong seasonal signature with a maximum in spring and a minimum in late summer/autumn. In winter when incoming solar radiation is minimal the surface albedo doesn't have an important effect on the energy balance of the climate system. The annual mean surface albedo is thus determined by the seasonality of both downwelling shortwave radiation and sea ice cover. As sea ice cover reduces the seasonal signature is modified, the transient part from maximum sea ice cover to its minimum is shortened and sharpened. The sea ice cover is reduced when downwelling shortwave radiation is maximum and thus the annual surface albedo is drastically smaller. Consequently the change in annual surface albedo with time will become larger and so will the surface albedo feedback. We conclude that a stronger seasonality in sea ice leads to a stronger surface albedo feedback, which accelerates melting of sea ice. Hence, the change in seasonality and the associated change in feedback strength is an integral part of the positive surface albedo feedback leading to Arctic amplification and diminishing sea ice cover in the next century when global climate warms.

Inversion of Solid Earth's Varying Shape 2: Using Self-Consistency to Infer Static Ocean Topography

NASA Astrophysics Data System (ADS)

Blewitt, G.; Clarke, P. J.

2002-12-01

We have developed a spectral approach to invert for the redistribution of mass on the Earth's surface given precise global geodetic measurements of the solid Earth's geometrical shape. We used the elastic load Love number formalism to characterize the redistributed mass as a spherical harmonic expansion, truncated at some degree and order n. [Clarke and Blewitt, this meeting]. Here we incorporate the additional physical constraint that the sea surface in hydrostatic equilibrium corresponds to an equipotential surface, to infer the non-steric component of static ocean topography. Our model rigorously accounts for self-gravitation of the ocean, continental surface mass, and the deformed solid Earth, such that the sea surface adopts a new equipotential surface consistent with ocean-land mass exchange, deformation of the geoid, deformation of the sea floor, and the geographical configuration of the oceans and continents. We develop a self-consistent spectral inversion method to solve for the distribution of continental surface mass that would generate geographic variations in relative mean sea level such that the total (ocean plus continental) mass distribution agrees with the original geodetic estimates to degree and order n. We apply this theory to study the contribution of seasonal inter-hemispheric (degree-1) mass transfer to seasonal variation in static ocean topography, using a published empirical seasonal model for degree-1 surface loading derived using GPS coordinate time series from the global IGS network [Blewitt et al., Science 294, 2,342-2,345, 2001]. The resulting predictions of seasonal variations of relative sea level strongly depend on location, with peak variations ranging from 3 mm to 19 mm. The largest peak variations are predicted in mid-August around Antarctica and the southern hemisphere in general; the lowest variations are predicted in the northern hemisphere. Corresponding maximum continental loading occurs in Canada and Siberia at the water-equivalent level of 200 mm. The RMS spatial variability about global mean sea level at any given time is 20% for geocentric sea level (as measured by satellite altimetry) versus relative sea level, which is a consequence of degree-1 sea floor displacement in the center of figure frame. While land-ocean mass exchange governs global mean relative sea level, at any given point the contribution of geoid deformation to relative sea level can be of similar magnitude, and so can almost cancel or double the effect of change in global mean sea level.While the sea surface takes on the shape of the deformed geoid, the sea surface everywhere seasonally oscillates about the deformed geoid with annual amplitude 6.1 mm. This effect is due mainly to an 8.0+/- 0.7~mm contribution from land-ocean mass exchange, which is then reduced by a 1.9 mm seasonal variation in the mean geoid height above the sea floor (to which a mass-conserved ocean cannot respond). Of this, 0.4 mm is due to the mean geocentric height of the sea floor, and 1.5 mm is due to the mean geocentric height of the geoid over oceanic areas. The seasonal gradients predicted by our inversion might be misinterpreted as basin-scale dynamics. Also, the oceans amplify a land degree-1 load by 20--30%, which suggests that deformation (and models of geocenter displacements) would be sensitive to the accuracy of ocean bottom pressure, particularly in the southern hemisphere.

Assessment of island beach erosion due to sea level rise: the case of the Aegean archipelago (Eastern Mediterranean)

NASA Astrophysics Data System (ADS)

Monioudi, Isavela N.; Velegrakis, Adonis F.; Chatzipavlis, Antonis E.; Rigos, Anastasios; Karambas, Theophanis; Vousdoukas, Michalis I.; Hasiotis, Thomas; Koukourouvli, Nikoletta; Peduzzi, Pascal; Manoutsoglou, Eva; Poulos, Serafim E.; Collins, Michael B.

2017-03-01

The present contribution constitutes the first comprehensive attempt to (a) record the spatial characteristics of the beaches of the Aegean archipelago (Greece), a critical resource for both the local and national economy, and (b) provide a rapid assessment of the impacts of the long-term and episodic sea level rise (SLR) under different scenarios. Spatial information and other attributes (e.g., presence of coastal protection works and backshore development) of the beaches of the 58 largest islands of the archipelago were obtained on the basis of remote-sensed images available on the web. Ranges of SLR-induced beach retreats under different morphological, sedimentological and hydrodynamic forcing, and SLR scenarios were estimated using suitable ensembles of cross-shore (1-D) morphodynamic models. These ranges, combined with empirically derived estimations of wave run-up induced flooding, were then compared with the recorded maximum beach widths to provide ranges of retreat/erosion and flooding at the archipelago scale. The spatial information shows that the Aegean pocket beaches may be particularly vulnerable to mean sea level rise (MSLR) and episodic SLRs due to (i) their narrow widths (about 59 % of the beaches have maximum widths < 20 m), (ii) their limited terrestrial sediment supply, (iii) the substantial coastal development and (iv) the limited existing coastal protection. Modeling results indeed project severe impacts under mean and episodic SLRs, which by 2100 could be devastating. For example, under MSLR of 0.5 m - representative concentration pathway (RCP) 4.5 of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate change (IPCC) - a storm-induced sea level rise of 0.6 m is projected to result in a complete erosion of between 31 and 88 % of all beaches (29-87 % of beaches are currently fronting coastal infrastructure and assets), at least temporarily. Our results suggest a very considerable risk which will require significant effort, financial resources and policies/regulation in order to protect/maintain the critical economic resource of the Aegean archipelago.

PCDDs, PCDFs and PCBs in farmed fish produced in Greece: Levels and human population exposure assessment.

PubMed

Costopoulou, Danae; Vassiliadou, Irene; Leondiadis, Leondios

2016-03-01

Fish is among the essential components of Mediterranean diet and has beneficial effects on human health. Farmed fish is an affordable alternative to wild fish and a significant food export product for Greece. Published studies worldwide have reported significant levels of environmental pollutants in fish tissues. Especially for PCDDs/Fs and PCBs, the studies suggest that the most important contribution to human dietary intake is from fish and seafood. In the present study, we investigate the levels of PCDDs/Fs, dioxin-like and non dioxin-like PCBs in the most common farmed fish species produced in Greece i.e. sea bass, sea bream and rainbow trout. These species are widely consumed in Greece and are also exported to many countries worldwide. The mean levels found were WHO-PCDD/F-TEQ: 0.22 pg g(-1) wet weight (w.w.), WHO-PCDD/F-PCB-TEQ: 0.88 pg g(-1) w.w. for sea bream, WHO-PCDD/F-TEQ: 0.13 pg g(-1) w.w., WHO-PCDD/F-PCB-TEQ: 0.68 pg g(-1) w.w. for sea bass and WHO-PCDD/F-TEQ: 0.10 pg g(-1) w.w., WHO-PCDD/F-PCB-TEQ: 0.43 pg g(-1) w.w. for rainbow trout. For non dioxin-like PCBs, mean sum values found were 8.02 ng g(-1) w.w. for sea bream, 5.24 ng g(-1) w.w. for sea bass and 2.90 ng g(-1) w.w. for rainbow trout. All concentrations found were far below maximum levels set by the European Union and in the same range as wild-caught fish also presented for comparison. Daily intake from the consumption of farmed fish species examined is calculated at 1.3 pg WHO-TEQ kg(-1) b.w., which is at the lowest end of TDI values proposed by the WHO. Copyright © 2015 Elsevier Ltd. All rights reserved.

Innovative Energy Absorbing Mounting Systems for High Mass Rotorcraft Payloads

DTIC Science & Technology

2008-12-01

that a maximum SEA value of 21.5 J/g can be achieved with a ±45° FMC tube and an aramid/ phenolic hexagonal honeycomb core with a crush stress of 10...Table 3. Optimized TTSRD tube SEA values (J/g) for various tube material systems. Carbon FMC Carbon/ Epoxy E-Glass/ Epoxy Kevlar / Epoxy Max...material systems considered in the present study, the crush tube concept had a maximum SEA of 21.5 J/g with a ±45° FMC tube and an aramid/ phenolic

Quaternary sedimentation of the Alaskan Beaufort shelf: Influence of regional tectonics, fluctuating sea levels, and glacial sediment sources

USGS Publications Warehouse

Dinter, D.A.

1985-01-01

The offshore stratigraphy of the Quaternary Gubik Formation of Arctic Alaska has been studied on high-resolution seismic profiles with a maximum sub-seafloor penetration of about 100 m. In general, marine transgressive subunits of the Gubik Formation are wedge-shaped on the shelf, thickening slightly seaward to the shelf break, beyond which they are offset by landslides and slumps. Beneath the eastern third of the Alaskan Beaufort shelf, active folding has created two persistent structural depressions, the Eastern and Western Wedge Terranes, in which the wedge morphology is especially well developed. The youngest transgressive marine wedge, which was deposited in such a way as to fill these depressions, leaving a generally flat present-day shelf surface, is inferred to be late Wisconsin or younger in age because it overlies a prominent disconformity interpreted to have been formed during the late Wisconsin glacial sea-level minimum. The thickness of this youngest wedge, Unit A, locally exceeds 40 m on the outer shelf, yet apparently relict gravel deposits collected from its seabed surface indicate that the depositional rate is presently quite low on the middle and outer shelf. Lithologies of the gravels are exotic to Alaska, but similar to suites exposed in the Canadian Arctic Islands. These observations suggest a depositional scenario in which the retreating Laurentide Ice Sheet shed sediment-laden icebergs from the Canadian Arctic Islands into the Arctic Ocean following the late Wisconsin glacial maximum. These bergs were then rafted westward by the Beaufort Gyre and grounded on the Alaskan shelf by northeasterly prevailing winds. Especially large numbers of bergs accumulated in the wedge terrane embayments-created as sea level rose-and melted there, filling the embayments with their sedimentary cargo. As glacial retreat slowed, depositional rates on the shelf dwindled. This mode of deposition in the Alaskan Beaufort wedge terranes may be typical of early post-glacial transgressive phases throughout Quaternary time. It has resulted in the preservation of disconformities that apparently formed during glacioeustatic lowstands, and whose seaward termination depths, appropriately corrected, may yield estimates of lowstand magnitudes. Knowledge of global sea-level fluctuations back through the Sangamon Interglacial (oxygen isotope stage 5e) and possible correlations with dated onshore deposits have facilitated a tentative correlation of major disconformities in the Beaufort Sea record with major 18O enrichment maxima in the oxygen isotope curve back through stage 8. In this tentative scheme, close similarities between the two data sets occur both in magnitudes and in numbers of fluctuations intervening between major correlation points. Further testing of the Quaternary depositional model suggested here and of the resulting sea level curve awaits the collection and dating of core samples from the Beaufort wedge terranes. ?? 1985.

Global temperature change

PubMed Central

Hansen, James; Sato, Makiko; Ruedy, Reto; Lo, Ken; Lea, David W.; Medina-Elizade, Martin

2006-01-01

Global surface temperature has increased ≈0.2°C per decade in the past 30 years, similar to the warming rate predicted in the 1980s in initial global climate model simulations with transient greenhouse gas changes. Warming is larger in the Western Equatorial Pacific than in the Eastern Equatorial Pacific over the past century, and we suggest that the increased West–East temperature gradient may have increased the likelihood of strong El Niños, such as those of 1983 and 1998. Comparison of measured sea surface temperatures in the Western Pacific with paleoclimate data suggests that this critical ocean region, and probably the planet as a whole, is approximately as warm now as at the Holocene maximum and within ≈1°C of the maximum temperature of the past million years. We conclude that global warming of more than ≈1°C, relative to 2000, will constitute “dangerous” climate change as judged from likely effects on sea level and extermination of species. PMID:17001018

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.

Post-glacial sea-level history for SW Ireland (Bantry Bay) based on offshore evidence

NASA Astrophysics Data System (ADS)

Plets, R. M.; Callard, L.; Cooper, A.; Long, A. J.; Belknap, D. F.; Edwards, R.; Jackson, D.; Kelley, J. T.; Long, D.; Milne, G. A.; Monteys, X.; Quinn, R.

2013-12-01

In recent years, progress in remote sensing techniques has helped to constrain the advance and retreat phases of the British-Irish Ice Sheet during and after the Last Glacial Maximum (LGM), both on- and offshore. However, little evidence has been collected to study the pattern of relative sea-level (RSL) change immediately after ice sheet retreat. Glacio-isostatic adjustment (GIA) models suggest a complex RSL pattern around Ireland, influenced by local and regional isostatic movements. Unfortunately, such models are poorly constrained for periods during which RSL was significantly lower than present, particularly the Late Pleistocene and Early Holocene, owing to the paucity of accurate observational data offshore. This poster presents post-LGM stratigraphic evidence from Bantry Bay (SW Ireland), one of seven areas targeted around the Irish Sea as part of a larger NERC funded project which aims to provide the first field data on the depth and age of the RSL minimum since deglaciation in the Irish Sea Basin. Data examined consists of: multibeam bathymetry and backscatter, pinger sub-bottom and vibrocores (25 sites). Notable features on the multibeam are a bluff line in the outer bay with a maximum height of 10 m in water depths of c. -80 m which forms the western edge of a large sediment lobe. The south-western boundary of this lobe is marked by a series of long (up to 22 km), parallel ridges at depths between -96 m and -131 m, with iceberg scouring evident on the offshore margin. Six seismo-stratigraphic units are interpreted from the pinger data, the most prominent of which can be traced from the inner part of the Bay to the inshore edge of the ridges. This unit sits on an erosional surface, is characterised by a turbid acoustic signature and is identified as alternating sand and clay layers with some traces of organic material and gas. Equal amounts of marine and estuarine foraminifera are present within this unit, whilst the underlying unit has a higher percentage of brackish species and the overlying unit becomes predominantly marine. Based on this evidence, we suggest that the erosional surface represents the transgressive surface, underlying intertidal sediments. Mapping the extent of this surface reveals a maximum depth of -75 m offshore, rising gradually to a depth of -30 m in the inner Bay, a profile remarkably similar to the modelled sea-level curve for the area. The long parallel ridges are interpreted to represent ice-marginal, submarine moraine ridges associated with ice retreat, behind which a glacio-marine delta formed, resulting in the large sediment lobe imaged at the mouth of Bantry Bay. Foraminifera from the proposed transgressive surface have been submitted for radiocarbon dating. Once available, these results will be used for fine-tuning the Earth and ice model parameters in the GIA model. Such adjustments could have important implications for modelled RSL curves around the Irish Sea basin.

Holocene sea-level changes along the North Carolina Coastline and their implications for glacial isostatic adjustment models

USGS Publications Warehouse

Horton, B.P.; Peltier, W.R.; Culver, S.J.; Drummond, R.; Engelhart, S.E.; Kemp, A.C.; Mallinson, D.; Thieler, E.R.; Riggs, S.R.; Ames, D.V.; Thomson, K.H.

2009-01-01

We have synthesized new and existing relative sea-level (RSL) data to produce a quality-controlled, spatially comprehensive database from the North Carolina coastline. The RSL database consists of 54 sea-level index points that are quantitatively related to an appropriate tide level and assigned an error estimate, and a further 33 limiting dates that confine the maximum and minimum elevations of RSL. The temporal distribution of the index points is very uneven with only five index points older than 4000 cal a BP, but the form of the Holocene sea-level trend is constrained by both terrestrial and marine limiting dates. The data illustrate RSL rapidly rising during the early and mid Holocene from an observed elevation of -35.7 ?? 1.1 m MSL at 11062-10576 cal a BP to -4.2 m ?? 0.4 m MSL at 4240-3592 cal a BP. We restricted comparisons between observations and predictions from the ICE-5G(VM2) with rotational feedback Glacial Isostatic Adjustment (GIA) model to the Late Holocene RSL (last 4000 cal a BP) because of the wealth of sea-level data during this time interval. The ICE-5G(VM2) model predicts significant spatial variations in RSL across North Carolina, thus we subdivided the observations into two regions. The model forecasts an increase in the rate of sea-level rise in Region 1 (Albemarle, Currituck, Roanoke, Croatan, and northern Pamlico sounds) compared to Region 2 (southern Pamlico, Core and Bogue sounds, and farther south to Wilmington). The observations show Late Holocene sea-level rising at 1.14 ?? 0.03 mm year-1 and 0.82 ?? 0.02 mm year-1 in Regions 1 and 2, respectively. The ICE-5G(VM2) predictions capture the general temporal trend of the observations, although there is an apparent misfit for index points older than 2000 cal a BP. It is presently unknown whether these misfits are caused by possible tectonic uplift associated with the mid-Carolina Platform High or a flaw in the GIA model. A comparison of local tide gauge data with the Late Holocene RSL trends from Regions 1 and 2 support the spatial variation in RSL across North Carolina, and imply an additional increase of mean sea level of greater than 2 mm year-1 during the latter half of the 20th century; this is in general agreement with historical tide gauge and satellite altimetry data. ?? 2009 Elsevier Ltd.

Total meltwater volume since the Last Glacial Maximum and viscosity structure of Earth's mantle inferred from relative sea level changes at Barbados and Bonaparte Gulf and GIA-induced J˙2

NASA Astrophysics Data System (ADS)

Nakada, Masao; Okuno, Jun'ichi; Yokoyama, Yusuke

2016-02-01

Inference of globally averaged eustatic sea level (ESL) rise since the Last Glacial Maximum (LGM) highly depends on the interpretation of relative sea level (RSL) observations at Barbados and Bonaparte Gulf, Australia, which are sensitive to the viscosity structure of Earth's mantle. Here we examine the RSL changes at the LGM for Barbados and Bonaparte Gulf ({{RSL}}_{{L}}^{{{Bar}}} and {{RSL}}_{{L}}^{{{Bon}}}), differential RSL for both sites (Δ {{RSL}}_{{L}}^{{{Bar}},{{Bon}}}) and rate of change of degree-two harmonics of Earth's geopotential due to glacial isostatic adjustment (GIA) process (GIA-induced J˙2) to infer the ESL component and viscosity structure of Earth's mantle. Differential RSL, Δ {{RSL}}_{{L}}^{{{Bar}},{{Bon}}} and GIA-induced J˙2 are dominantly sensitive to the lower-mantle viscosity, and nearly insensitive to the upper-mantle rheological structure and GIA ice models with an ESL component of about (120-130) m. The comparison between the predicted and observationally derived Δ {{RSL}}_{{L}}^{{{Bar}},{{Bon}}} indicates the lower-mantle viscosity higher than ˜2 × 1022 Pa s, and the observationally derived GIA-induced J˙2 of -(6.0-6.5) × 10-11 yr-1 indicates two permissible solutions for the lower mantle, ˜1022 and (5-10) × 1022 Pa s. That is, the effective lower-mantle viscosity inferred from these two observational constraints is (5-10) × 1022 Pa s. The LGM RSL changes at both sites, {{RSL}}_{{L}}^{{{Bar}}} and {{RSL}}_{{L}}^{{{Bon}}}, are also sensitive to the ESL component and upper-mantle viscosity as well as the lower-mantle viscosity. The permissible upper-mantle viscosity increases with decreasing ESL component due to the sensitivity of the LGM sea level at Bonaparte Gulf ({{RSL}}_{{L}}^{{{Bon}}}) to the upper-mantle viscosity, and inferred upper-mantle viscosity for adopted lithospheric thicknesses of 65 and 100 km is (1-3) × 1020 Pa s for ESL˜130 m and (4-10) × 1020 Pa s for ESL˜125 m. The former solution of (1-3) × 1020 Pa s is consistent with the inferences from the postglacial differential RSL changes in the Australian region and also inversion study of far-field sea-level data. The inference of the viscosity structure based on these four observational constraints is, however, relatively insensitive to the viscosity structure of D″ layer.

Glacier velocity Changes at Novaya Zemlya revealed by ALOS1 and ALOS2

NASA Astrophysics Data System (ADS)

Konuma, Y.; Furuya, M.

2016-12-01

Matsuo and Heki (2013) revealed substantial ice-mass loss at Novaya Zemlya by Gravity Recovery And Climate Experiment (GRACE). In addition, the elevation thinning (Moholdt et al., 2012) and glacier retreat (Carr et al., 2014) has been reported. Melkonian et al. (2016) showed velocities map at coastal area of Novaya Zemlya by using Worldview, Landsat, ASTER and TerraSAR-X images. However, the entire distributions of ice speed and the temporal evolution remain unclear. In this study, we measured the glacier velocities using L-band SAR sensor onboard ALOS1 and ALOS2. We analyzed the data using pixel-offset tracking technique. We could observe the entire glaciated region in 2007-2008 winter and 2008-2009 winter. In particular, we could examine the velocities at middle of the glaciated region from 2006 to 2015 due to the availability of high-temporal resolution SAR data. As a result, we found the most glaciers in Novaya Zemlya have been accelerating since 1990s (Strozzi et al., 2008). Specially, Shokalskogo glacier has dramatically accelerated from the maximum of 300 ma-1 in 1998 to maximum of 600 ma-1 in 2015. Additionally, it turns out that there are marked differences in the glacier's velocities between the Barents Sea side and the Kara Sea side. The averaged maximum speed of the glaciers in Barents Sea side were approximately two times faster than that in Kara Sea side. We speculate the causes as the difference of topography under the calving front and sea-ice concentration. While each side has many calving glaciers, the fjord distribution in the Barents Sea side is much broader than in the Kara Sea side. Moreover, sea-ice concentration in the Barents Sea is lower than the Kara Sea, which might affect the glaciers' speed distribution.

Microbial diversity from chlorophyll maximum, oxygen minimum and bottom zones in the southwestern Atlantic Ocean

NASA Astrophysics Data System (ADS)

Medina-Silva, Renata; de Oliveira, Rafael R.; Pivel, Maria A. G.; Borges, Luiz G. A.; Simão, Taiz L. L.; Pereira, Leandro M.; Trindade, Fernanda J.; Augustin, Adolpho H.; Valdez, Fernanda P.; Eizirik, Eduardo; Utz, Laura R. P.; Groposo, Claudia; Miller, Dennis J.; Viana, Adriano R.; Ketzer, João M. M.; Giongo, Adriana

2018-02-01

Conspicuous physicochemical vertical stratification in the deep sea is one of the main forces driving microbial diversity in the oceans. Oxygen and sunlight availability are key factors promoting microbial diversity throughout the water column. Ocean currents also play a major role in the physicochemical stratification, carrying oxygen down to deeper zones as well as moving deeper water masses up towards shallower depths. Water samples within a 50-km radius in a pockmark location of the southwestern Atlantic Ocean were collected and the prokaryotic communities from different water depths - chlorophyll maximum, oxygen minimum and deep-sea bottom (down to 1355 m) - were described. At phylum level, Proteobacteria were the most frequent in all water depths, Cyanobacteria were statistically more frequent in chlorophyll maximum zone, while Thaumarchaeota were significantly more abundant in both oxygen minimum and bottom waters. The most frequent microorganism in the chlorophyll maximum and oxygen minimum zones was a Pelagibacteraceae operational taxonomic unit (OTU). At the bottom, the most abundant genus was the archaeon Nitrosopumilus. Beta diversity analysis of the 16S rRNA gene sequencing data uncovered in this study shows high spatial heterogeneity among water zones communities. Our data brings important contribution for the characterisation of oceanic microbial diversity, as it consists of the first description of prokaryotic communities occurring in different oceanic water zones in the southwestern Atlantic Ocean.

The Climate Science Special Report: Rising Seas and Changing Oceans

NASA Astrophysics Data System (ADS)

Kopp, R. E.

2017-12-01

GMSL has risen by about 16-21 cm since 1900. Ocean heat content has increased at all depths since the 1960s, and global mean sea-surface temperature increased 0.7°C/century between 1900 to 2016. Human activity contributed substantially to generating a rate of GMSL rise since 1900 faster than during any preceding century in at least 2800 years. A new set of six sea-level rise scenarios, spanning a range from 30 cm to 250 cm of 21st century GMSL rise, were developed for the CSSR. The lower scenario is based on linearly extrapolating the past two decades' rate of rise. The upper scenario is informed by literature estimates of maximum physically plausible values, observations indicating the onset of marine ice sheet instability in parts of West Antarctica, and modeling of ice-cliff and ice-shelf instability mechanisms. The new scenarios include localized projections along US coastlines. There is significant variability around the US, with rates of rise likely greater than GMSL rise in the US Northeast and the western Gulf of Mexico. Under scenarios involving extreme Antarctic contributions, regional rise would be greater than GMSL rise along almost all US coastlines. Historical sea-level rise has already driven a 5- to 10-fold increase in minor tidal flooding in several US coastal cities since the 1960s. Under the CSSR's Intermediate sea-level rise scenario (1.0 m of GMSL rise in 2100) , a majority of NOAA tide gauge locations will by 2040 experience the historical 5-year coastal flood about 5 times per year. Ocean changes are not limited to rising sea levels. Ocean pH is decreasing at a rate that may be unparalleled in the last 66 million years. Along coastlines, ocean acidification can be enhanced by changes in the upwelling (particularly along the US Pacific Coast); by episodic, climate change-enhanced increases in freshwater input (particularly along the US Atlantic Coast); and by the enhancement of biological respiration by nutrient runoff. Climate models project a slowdown in the Atlantic Meridional Overturning Circulation (AMOC) under high-emissions scenarios. Any slowdown will reduce ocean heat and carbon absorption and raise sea levels off the northeastern US A full AMOC collapse, improbable in the current century, would lead to an additional 0.5 m of sea-level rise and offset 0-2°C of warming over the US.

Deterministic approach for multiple-source tsunami hazard assessment for Sines, Portugal

NASA Astrophysics Data System (ADS)

Wronna, M.; Omira, R.; Baptista, M. A.

2015-11-01

In this paper, we present a deterministic approach to tsunami hazard assessment for the city and harbour of Sines, Portugal, one of the test sites of project ASTARTE (Assessment, STrategy And Risk Reduction for Tsunamis in Europe). Sines has one of the most important deep-water ports, which has oil-bearing, petrochemical, liquid-bulk, coal, and container terminals. The port and its industrial infrastructures face the ocean southwest towards the main seismogenic sources. This work considers two different seismic zones: the Southwest Iberian Margin and the Gloria Fault. Within these two regions, we selected a total of six scenarios to assess the tsunami impact at the test site. The tsunami simulations are computed using NSWING, a Non-linear Shallow Water model wIth Nested Grids. In this study, the static effect of tides is analysed for three different tidal stages: MLLW (mean lower low water), MSL (mean sea level), and MHHW (mean higher high water). For each scenario, the tsunami hazard is described by maximum values of wave height, flow depth, drawback, maximum inundation area and run-up. Synthetic waveforms are computed at virtual tide gauges at specific locations outside and inside the harbour. The final results describe the impact at the Sines test site considering the single scenarios at mean sea level, the aggregate scenario, and the influence of the tide on the aggregate scenario. The results confirm the composite source of Horseshoe and Marques de Pombal faults as the worst-case scenario, with wave heights of over 10 m, which reach the coast approximately 22 min after the rupture. It dominates the aggregate scenario by about 60 % of the impact area at the test site, considering maximum wave height and maximum flow depth. The HSMPF scenario inundates a total area of 3.5 km2.

Biostratigraphic, chronostratigraphic, and stratigraphic sequence analysis of Lower Tertiary marine sediments of Alabama for indicators of sea-level change

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

Thompson, P.R.; Baum, G.R.

1991-03-01

Early Eocene to late Oligocene marine sedimentary units in southwestern Alabama were sampled at closely spaced intervals to derive a precise time-stratigraphic framework and to determine the paleoecological and mineralogical responses to fluctuations in sea level. Paleontologic control consisted of planktonic, smaller and larger benthonic foraminifera, calcareous nannofossils, dinoflagellates, and megafossils. Paleomagnetic reversals were delineated in two boreholes which, when supplemented by strontium isotope dates and the biostratigraphic control, provided a robust in situ chronostratigraphy for the Gulf Coast lower Tertiary. Paleoecologic trends in regression and transgression can be clearly correlated across major regional facies changes. Using the chronostratigraphy developedmore » here, the second-, third-, and fourth-orders of Vail's global sea-level cycles can be recognized and demonstrate the influence of sea-level change on sedimentation. Stratigraphic systems tracts (SSTs) and bounding surfaces in outcrop were determined by lithologic variations and paleoecologic trends, and additionally by gamma logs in the cores. The lower sequence boundary occurs at a contact where an older, relatively fine-grained, deep-water, fossiliferous unit was abruptly succeeded by a coarse-grained, shallow-water, poorly fossiliferous unit. The transgressive surface occurs at the base of a fining- and deepening-upwards unit that was commonly glauconitic and very fossiliferous. Transgression culminated with a pulse of planktonic microfossils in a bed having reduced clastic sedimentation; on the log the surface of maximum starvation was marked by a gamma spike.« less

A complete Holocene record of trematode-bivalve infection and implications for the response of parasitism to climate change

NASA Astrophysics Data System (ADS)

Huntley, John Warren; Fürsich, Franz T.; Alberti, Matthias; Hethke, Manja; Liu, Chunlian

2014-12-01

Increasing global temperature and sea-level rise have led to concern about expansions in the distribution and prevalence of complex-lifecycle parasites (CLPs). Indeed, numerous environmental variables can influence the infectivity and reproductive output of many pathogens. Digenean trematodes are CLPs with intermediate invertebrate and definitive vertebrate hosts. Global warming and sea level rise may affect these hosts to varying degrees, and the effect of increasing temperature on parasite prevalence has proven to be nonlinear and difficult to predict. Projecting the response of parasites to anthropogenic climate change is vital for human health, and a longer term perspective (104 y) offered by the subfossil record is necessary to complement the experimental and historical approaches of shorter temporal duration (10-1 to 103 y). We demonstrate, using a high-resolution 9,600-y record of trematode parasite traces in bivalve hosts from the Holocene Pearl River Delta, that prevalence was significantly higher during the earliest stages of sea level rise, significantly lower during the maximum transgression, and statistically indistinguishable in the other stages of sea-level rise and delta progradation. This stratigraphic paleobiological pattern represents the only long-term high-resolution record of pathogen response to global change, is consistent with fossil and recent data from other marine basins, and is instructive regarding the future of disease. We predict an increase in trematode prevalence concurrent with anthropogenic warming and marine transgression, with negative implications for estuarine macrobenthos, marine fisheries, and human health.

Temporal constraints on future accumulation-area loss of a major Arctic ice cap due to climate change (Vestfonna, Svalbard)

PubMed Central

Möller, Marco; Schneider, Christoph

2015-01-01

Arctic glaciers and ice caps are major contributors to past, present and future sea-level fluctuations. Continued global warming may eventually lead to the equilibrium line altitudes of these ice masses rising above their highest points, triggering unstoppable downwasting. This may feed future sea-level rise considerably. We here present projections for the timing of equilibrium-line loss at the major Arctic ice cap Vestfonna, Svalbard. The projections are based on spatially distributed climatic mass balance modelling driven by the outputs of multiple climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) forced by the Representative Concentration Pathways (RCPs) 2.6, 4.5, 6.0 and 8.5. Results indicate strongly decreasing climatic mass balances over the 21st century for all RCPs considered. Glacier-wide mass-balance rates will drop down to −4 m a−1 w.e. (water equivalent) at a maximum. The date at which the equilibrium line rises above the summit of Vestfonna (630 m above sea level) is calculated to range between 2040 and 2150, depending on scenario. PMID:25628045

COSMIC RADIATION AND TUBERCULOSIS. IV. INFLUENCE OF COSMIC RADIATION ON TUBERCULOSIS AT HIGH ALTITUDE (3,130 M) AND AT SEA-LEVEL

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

Ong, S.G.

1964-01-01

At high altitude (3,130 m) tuberculous mice exposed to cosmic radiation under 10 cm of lead showed significantly greater mean survival time and a significantly greater number of survivors than tuberculous mice exposed to direct cosmic radiation. Tuberculous mice exposed to cosmic radiation at high altitude under 10 cm of lead showed a significantly greater mean survival time than tuberculous mice kept at sea level, exposed to direct cosmic radiation, and to cosmic radiation under 1, 2, and 10 cm of lead. The correlation analysis shows that a decreas in lung lesions is associated with an increase in survival time.more » The decrease in lung lesions is associated with an enlargement of the spleen. At high altitude the female showed a significantly greater number of survivors than the male. At sea level no significant difference was observed. On the average the female showed a significantly greater number of survivors. The beneficial effect of daylight with ultraviolet light on tuberculous mice was manifested in a lower maximum of mortality and in a significant decrease of lung and spleen lesions. (auth)« less

Distribution of low-level natural radioactivity in a populated marine region of the Eastern Mediterranean Sea.

PubMed

Evangeliou, Nikolaos; Florou, Heleny; Kritidis, Panayotis

2012-12-01

The levels of natural radioactivity have been evaluated in the water column of an eastern Mediterranean region (Saronikos Gulf), with respect to the relevant environmental parameters. A novel methodology was used for the determination of natural radionuclides, which substitutes the time-consuming radiochemical analysis, based on an in situ sample preconcentration using ion-selective manganese fibres placed on pumping systems. With regard to the results obtained, (238)U-series radionuclides were found at the same level or lower than those observed previously in Mediterranean regions indicating the absence of technologically enhanced naturally occurring radioactive material (TENORM) activities in the area. Similar results were observed for the (232)Th-series radionuclides and (40)K in the water column in comparison with the relevant literature on the Mediterranean Sea. The calculated ratios of (238)U-(232)Th and (40)K-(232)Th verified the lack of TENORM contribution in the Saronikos Gulf. Finally, a rough estimation was attempted concerning the residence times of fresh water inputs from a treatment plant of domestic wastes (Waste Water Treatment Plant of Psitalia) showing that fresh waters need a maximum of 15.7±7.6 d to be mixed with the open sea water.

Regional influences on reconstructed global mean sea level

NASA Astrophysics Data System (ADS)

Natarov, Svetlana I.; Merrifield, Mark A.; Becker, Janet M.; Thompson, Phillip R.

2017-04-01

Reconstructions of global mean sea level (GMSL) based on tide gauge measurements tend to exhibit common multidecadal rate fluctuations over the twentieth century. GMSL rate changes may result from physical drivers, such as changes in radiative forcing or land water storage. Alternatively, these fluctuations may represent artifacts due to sampling limitations inherent in the historical tide gauge network. In particular, a high percentage of tide gauges used in reconstructions, especially prior to the 1950s, are from Europe and North America in the North Atlantic region. Here a GMSL reconstruction based on the reduced space optimal interpolation algorithm is deconstructed, with the contributions of individual tide gauge stations quantified and assessed regionally. It is demonstrated that the North Atlantic region has a disproportionate influence on reconstructed GMSL rate fluctuations prior to the 1950s, notably accounting for a rate minimum in the 1920s and contributing to a rate maximum in the 1950s. North Atlantic coastal sea level fluctuations related to wind-driven ocean volume redistribution likely contribute to these estimated GMSL rate inflections. The findings support previous claims that multidecadal rate changes in GMSL reconstructions are likely related to the geographic distribution of tide gauge stations within a sparse global network.

Modern climate challenges and the geological record

USGS Publications Warehouse

Cronin, Thomas M.

2010-01-01

Today's changing climate poses challenges about the influence of human activity, such as greenhouse gas emissions and land use changes, the natural variability of Earth's climate, and complex feedback processes. Ice core and instrumental records show that over the last century, atmospheric carbon dioxide (CO2) concentrations have risen to 390 parts per million volume (ppmv), about 40% above pre-Industrial Age concentrations of 280 ppmv and nearly twice those of the last glacial maximum about 22,000 years ago. Similar historical increases are recorded in atmospheric methane (CH4) and nitrous oxide (N2O). There is general agreement that human activity is largely responsible for these trends. Substantial evidence also suggests that elevated greenhouse gas concentrations are responsible for much of the recent atmospheric and oceanic warming, rising sea level, declining Arctic sea-ice cover, retreating glaciers and small ice caps, decreased mass balance of the Greenland and parts of the Antarctic ice sheets, and decreasing ocean pH (ocean "acidification"). Elevated CO2 concentrations raise concern not only from observations of the climate system, but because feedbacks associated with reduced reflectivity from in land and sea ice, sea level, and land vegetation relatively slowly (centuries or longer) to elevated 2 levels. This means that additional human-induced climate change is expected even if the rate of CO2 emissions is reduced or concentrations immediately stabilized.

Ice loading model for Glacial Isostatic Adjustment in the Barents Sea constrained by GRACE gravity observations

NASA Astrophysics Data System (ADS)

Root, Bart; Tarasov, Lev; van der Wal, Wouter

2014-05-01

The global ice budget is still under discussion because the observed 120-130 m eustatic sea level equivalent since the Last Glacial Maximum (LGM) can not be explained by the current knowledge of land-ice melt after the LGM. One possible location for the missing ice is the Barents Sea Region, which was completely covered with ice during the LGM. This is deduced from relative sea level observations on Svalbard, Novaya Zemlya and the North coast of Scandinavia. However, there are no observations in the middle of the Barents Sea that capture the post-glacial uplift. With increased precision and longer time series of monthly gravity observations of the GRACE satellite mission it is possible to constrain Glacial Isostatic Adjustment in the center of the Barents Sea. This study investigates the extra constraint provided by GRACE data for modeling the past ice geometry in the Barents Sea. We use CSR release 5 data from February 2003 to July 2013. The GRACE data is corrected for the past 10 years of secular decline of glacier ice on Svalbard, Novaya Zemlya and Frans Joseph Land. With numerical GIA models for a radially symmetric Earth, we model the expected gravity changes and compare these with the GRACE observations after smoothing with a 250 km Gaussian filter. The comparisons show that for the viscosity profile VM5a, ICE-5G has too strong a gravity signal compared to GRACE. The regional calibrated ice sheet model (GLAC) of Tarasov appears to fit the amplitude of the GRACE signal. However, the GRACE data are very sensitive to the ice-melt correction, especially for Novaya Zemlya. Furthermore, the ice mass should be more concentrated to the middle of the Barents Sea. Alternative viscosity models confirm these conclusions.

An Assessment of State-of-the-Art Mean Sea Surface and Geoid Models of the Arctic Ocean: Implications for Sea Ice Freeboard Retrieval

NASA Astrophysics Data System (ADS)

Skourup, Henriette; Farrell, Sinéad Louise; Hendricks, Stefan; Ricker, Robert; Armitage, Thomas W. K.; Ridout, Andy; Andersen, Ole Baltazar; Haas, Christian; Baker, Steven

2017-11-01

State-of-the-art Arctic Ocean mean sea surface (MSS) models and global geoid models (GGMs) are used to support sea ice freeboard estimation from satellite altimeters, as well as in oceanographic studies such as mapping sea level anomalies and mean dynamic ocean topography. However, errors in a given model in the high-frequency domain, primarily due to unresolved gravity features, can result in errors in the estimated along-track freeboard. These errors are exacerbated in areas with a sparse lead distribution in consolidated ice pack conditions. Additionally model errors can impact ocean geostrophic currents, derived from satellite altimeter data, while remaining biases in these models may impact longer-term, multisensor oceanographic time series of sea level change in the Arctic. This study focuses on an assessment of five state-of-the-art Arctic MSS models (UCL13/04 and DTU15/13/10) and a commonly used GGM (EGM2008). We describe errors due to unresolved gravity features, intersatellite biases, and remaining satellite orbit errors, and their impact on the derivation of sea ice freeboard. The latest MSS models, incorporating CryoSat-2 sea surface height measurements, show improved definition of gravity features, such as the Gakkel Ridge. The standard deviation between models ranges 0.03-0.25 m. The impact of remaining MSS/GGM errors on freeboard retrieval can reach several decimeters in parts of the Arctic. While the maximum observed freeboard difference found in the central Arctic was 0.59 m (UCL13 MSS minus EGM2008 GGM), the standard deviation in freeboard differences is 0.03-0.06 m.

Glacial conditions in the Red Sea

NASA Astrophysics Data System (ADS)

Rohling, Eelco J.

1994-10-01

In this paper, results from previous studies on planktonic foraminifera, δ18O, and global sea level are combined to discuss climatic conditions in the Red Sea during the last glacial maximum (18,000 B.P.). First, the influence of 120-m sea level lowering on the exchange transport through the strait of Bab-el-Mandab is considered. This strait is the only natural connection of the Red Sea to the open ocean. Next, glacial Red Sea outflow salinity is estimated (about 48 parts per thousand) from the foraminiferal record. Combined, these results yield an estimate of the glacial net water deficit, which appears to have been quite similar to the present (about 2 m yr-1). Finally, budget calculation of δ18O fluxes suggests that the glacial δ18O value of evaporation was about 50% of the present value. This is considered to have resulted from substantially increased mean wind speeds over the glacial Red Sea, which would have caused a rapid drop in the kinematic fractionation factor for 18O. The sensitivity of the calculated values for water deficit and isotopic fractionation to the various assumptions and estimates is evaluated in the discussion. Improvents are to be expected especially through research on the glacial salinity contrast between the Red Sea and Gulf of Aden. It is argued, however, that such future improvement will likely result in a worsening of the isotopic discrepancy, thus increasing the need for an additional mechanism that influenced fractionation (such as mean wind speed). This study demonstrates the need for caution when calculating paleosalinities from δ18O records under the assumption that the modern S∶δ18O relation has remained constant through time. Previously overlooked factors, such as mean wind speed, may have significantly altered that relation in the past.

How strong is the impact of the Indo-ocean dipole on the surface air temperature/sea level pressure anomalies in the Mediterranean region?

NASA Astrophysics Data System (ADS)

Polonsky, Alexander B.; Basharin, Dmitry V.

2017-04-01

The aim of this paper is to study the interannual climate variability over the Mediterranean region related to the Indo-ocean dipole (IOD) using the data of re-analyses, archival data and specialized numerical experiments. It is shown that the IOD does not impact essentially the anomalies of surface air temperature (SAT) and sea level pressure (SLP) in the Mediterranean region. On average, the IOD-induced share of the SAT/SLP variance in the total variance of these fields in the Mediterranean region is smaller than 10% even in summer when it is at a maximum. However, the statistically significant IOD-induced SAT/SLP anomalies in the Mediterranean region are detectable. For definite IOD events the associated Mediterranean SAT anomalies can reach about 1 °C.

Naval Sea Systems Command Acquisition Strategy Guide v1.0

DTIC Science & Technology

2010-04-01

necessary to perform the contract. 2. Program context in overall prime system and major subsystem level industry sector and market . 3...organizations, and with industry through maximum use of alerts and the Government- Industry Data Exchange Program (GIDEP). 6.9 Military Equipment Valuation...simplified acquisition threshold. (2) The head of an agency shall use the results of market research to determine whether there are commercial

76 FR 8729 - Bison Peak Pumped Storage, LLC; Notice of Preliminary Permit Application Accepted for Filing and...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-15

...) to be located in the Tehachapi Mountains south of Tehachapi, Kern County, California. The sole... upper dam with a height of 50 feet, a crest length of 7,128 feet, and with a reservoir having a total storage capacity of 5,500 acre-feet at a normal maximum operating elevation of 7,860 feet mean sea level...

75 FR 19632 - San Diego County Water Authority; Notice of Preliminary Permit Application Accepted for Filing...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-15

... about each of these alternatives are described below. The sole purpose of a preliminary permit, if... being raised to a dam height of 337 feet, and a length of 1,442 feet; and (2) an existing impoundment... 247,000 acre-feet with a normal maximum water surface elevation of 767 feet above mean sea level (msl...

Evolution of a Greenland Ice sheet Including Shelves and Regional Sea Level Variations

NASA Astrophysics Data System (ADS)

Bradley, Sarah; Reerink, Thomas; van de Wal, Roderik S. W.; Helsen, Michiel; Goelzer, Heiko

2016-04-01

Observational evidence, including offshore moraines and marine sediment cores infer that at the Last Glacial maximum (LGM) the Greenland ice sheet (GIS) grounded out across the Davis Strait into Baffin Bay, with fast flowing ice streams extending out to the continental shelf break along the NW margin. These observations lead to a number of questions as to weather the GIS and Laurentide ice sheet (LIS) coalesced during glacial maximums, and if so, did a significant ice shelf develop across Baffin Bay and how would such a configuration impact on the relative contribution of these ice sheets to eustatic sea level (ESL). Most previous paleo ice sheet modelling simulations of the GIS recreated an ice sheet that either did not extend out onto the continental shelf or utilised a simplified marine ice parameterisation to recreate an extended GIS, and therefore did not fully include ice shelf dynamics. In this study we simulate the evolution of the GIS from 220 kyr BP to present day using IMAU-ice; a 3D thermodynamical ice sheet model which fully accounts for grounded and floating ice, calculates grounding line migration and ice shelf dynamics. As there are few observational estimates of the long-term (yrs) sub marine basal melting rates (mbm) for the GIS, we developed a mbm parameterization within IMAU-ice controlled primarily by changes in paleo water depth. We also investigate the influence of the LIS on the GIS evolution by including relative sea level forcing's derived from a Glacial Isostatic Adjustment model. We will present results of how changes in the mbm directly impacts on the ice sheet dynamics, timing and spatial extent of the GIS at the glacial maximums, but also on the rate of retreat and spatial extent at the Last interglacial (LIG) minimum. Results indicate that with the inclusion of ice shelf dynamics, a larger GIS is generated which is grounded out into Davis strait, up to a water depth of -750 m, but significantly reduces the GIS contribution to Last interglacial ESL.

Evolution of a Greenland Ice sheet Including Shelves and Regional Sea Level Variations

NASA Astrophysics Data System (ADS)

Bradley, S.; Reerink, T.; Vandewal, R.; Helsen, M.

2015-12-01

Observational evidence, including offshore moraines and marine sediment cores infer that at the Last Glacial maximum (LGM) the Greenland ice sheet (GIS) grounded out across the Davis Strait into Baffin Bay, with fast flowing ice streams extending out to the continental shelf break along the NW margin. These observations lead to a number of questions as to weather the GIS and Laurentide ice sheet (LIS) coalesced during glacial maximums, and if so, did a significant ice shelf develop across Baffin Bay and how would such a configuration impact on the relative contribution of these ice sheets to eustatic sea level (ESL). Most previous paleo ice sheet modelling simulations of the GIS recreated an ice sheet that either did not extend out onto the continental shelf or utilised a simplified marine ice parameterisation to recreate an extended GIS, and therefore did not fully include ice shelf dynamics. In this study we simulate the evolution of the GIS from 220 kyr BP to present day using IMAU-ice; a 3D thermodynamical ice sheet model which fully accounts for grounded and floating ice, calculates grounding line migration and ice shelf dynamics. There is few observational estimates of long-term (yrs) sub marine basal melting rates (mbm) for the GIS. Therefore we investigate a range of relationships to constrain the spatial and temporal parameterisation of mbm within IMAU-ice related to changes in paleo water depth, driven by changes in relative sea level and ocean temperature. We will present results of how changes in the mbm directly impacts on the ice sheet dynamics, timing and spatial extent of the GIS at the glacial maximums, but also on the rate of retreat and spatial extent at the Last interglacial (LIG) minimum. Initial results indicate that with the inclusion of ice shelf dynamics, a larger GIS is generated which is grounded out into Davis strait, up to a water depth of -750 m, but the total contribution to LIG ESL is reduced by up to 0.6 m.

Simulated Altitude Investigation of Stewart-Warner Model 906-B Combustion Heater

NASA Technical Reports Server (NTRS)

Ebersbach, Frederick R.; Cervenka, Adolph J.

1947-01-01

An investigation has been conducted to determine thermal and pressure-drop performance and the operational characteristics of a Stewart-Warner model 906-B combustion heater. The performance tests covered a range of ventilating-air flows from 500 to 3185 pounds per hour, combustion-air pressure drops from 5 to 35 inches of water, and pressure altitudes from sea level to 41,000 feet. The operational characteristics investigated were the combustion-air flows for sustained combustion and for consistent ignition covering fuel-air ratios ranging from 0.033 to 0.10 and pressure altitudes from sea level to 45,000 feet. Rated heat output of 50,000 Btu per hour was obtained at pressure altitudes up to 27,000 feet for ventilating-air flows greater than 800 pounds per hour; rated output was not obtained at ventilating-air flow below 800 pounds per hour at any altitude. The maximum heater efficiency was found to be 60.7 percent at a fuel-air ratio of 0.050, a sea-level pressure altitude, a ventilating-air temperature of 0 F, combustion-air temperature of 14 F, a ventilating-air flow of 690 pounds per hour, and a combustion-air flow of 72.7 pounds per hour. The minimum combustion-air flow for sustained combustion at a pressure altitude of 25,000 feet was about 9 pounds per hour for fuel-air ratios between 0.037 and 0.099 and at a pressure altitude of 45,000 feet increased to 18 pounds per hour at a fuel-air ratio of 0.099 and 55 pounds per hour at a fuel-air ratio of 0.036. Combustion could be sustained at combustion-air flows above values of practical interest. The maximum flow was limited, however, by excessively high exhaust-gas temperature or high pressure drop. Both maximum and minimum combustion-air flows for consistent ignition decrease with increasing pressure altitude and the two curves intersect at a pressure altitude of approximately 25,000 feet and a combustion-air flow of approximately 28 pounds per hour.

Antarctic climate change: extreme events disrupt plastic phenotypic response in Adélie penguins.

PubMed

Lescroël, Amélie; Ballard, Grant; Grémillet, David; Authier, Matthieu; Ainley, David G

2014-01-01

In the context of predicted alteration of sea ice cover and increased frequency of extreme events, it is especially timely to investigate plasticity within Antarctic species responding to a key environmental aspect of their ecology: sea ice variability. Using 13 years of longitudinal data, we investigated the effect of sea ice concentration (SIC) on the foraging efficiency of Adélie penguins (Pygoscelis adeliae) breeding in the Ross Sea. A 'natural experiment' brought by the exceptional presence of giant icebergs during 5 consecutive years provided unprecedented habitat variation for testing the effects of extreme events on the relationship between SIC and foraging efficiency in this sea-ice dependent species. Significant levels of phenotypic plasticity were evident in response to changes in SIC in normal environmental conditions. Maximum foraging efficiency occurred at relatively low SIC, peaking at 6.1% and decreasing with higher SIC. The 'natural experiment' uncoupled efficiency levels from SIC variations. Our study suggests that lower summer SIC than currently observed would benefit the foraging performance of Adélie penguins in their southernmost breeding area. Importantly, it also provides evidence that extreme climatic events can disrupt response plasticity in a wild seabird population. This questions the predictive power of relationships built on past observations, when not only the average climatic conditions are changing but the frequency of extreme climatic anomalies is also on the rise.

Antarctic Climate Change: Extreme Events Disrupt Plastic Phenotypic Response in Adélie Penguins

PubMed Central

Lescroël, Amélie; Ballard, Grant; Grémillet, David; Authier, Matthieu; Ainley, David G.

2014-01-01

In the context of predicted alteration of sea ice cover and increased frequency of extreme events, it is especially timely to investigate plasticity within Antarctic species responding to a key environmental aspect of their ecology: sea ice variability. Using 13 years of longitudinal data, we investigated the effect of sea ice concentration (SIC) on the foraging efficiency of Adélie penguins (Pygoscelis adeliae) breeding in the Ross Sea. A ‘natural experiment’ brought by the exceptional presence of giant icebergs during 5 consecutive years provided unprecedented habitat variation for testing the effects of extreme events on the relationship between SIC and foraging efficiency in this sea-ice dependent species. Significant levels of phenotypic plasticity were evident in response to changes in SIC in normal environmental conditions. Maximum foraging efficiency occurred at relatively low SIC, peaking at 6.1% and decreasing with higher SIC. The ‘natural experiment’ uncoupled efficiency levels from SIC variations. Our study suggests that lower summer SIC than currently observed would benefit the foraging performance of Adélie penguins in their southernmost breeding area. Importantly, it also provides evidence that extreme climatic events can disrupt response plasticity in a wild seabird population. This questions the predictive power of relationships built on past observations, when not only the average climatic conditions are changing but the frequency of extreme climatic anomalies is also on the rise. PMID:24489657

Post-glacial sea-level history for NE Ireland (Belfast Lough) based on offshore evidence

NASA Astrophysics Data System (ADS)

Quinn, R.; Plets, R. M.; Callard, L.; Cooper, A.; Long, A. J.; Belknap, D. F.; Edwards, R.; Jackson, D.; Kelley, J. T.; Long, D.; Milne, G. A.; Monteys, X.

2013-12-01

Glacio-isostatic adjustment (GIA) models suggest a complex relative sea-level (RSL) pattern around the Irish Sea Basin after the Last Glacial Maximum (LGM), with modelled sea-level lowstands ranging from -12 m in the north to greater than -60 m in the south of the Basin. However, these GIA models are poorly constrained by observational data offshore. Belfast Lough, on the NE coast of Ireland, is one of seven sites chosen to investigate this complex RSL history as part of the project ';Late Glacial Sea level minima in the Western British Isles' (NERC NE/H024301/1). Belfast Lough was chosen as one of the candidate sites on the basis of location (at the northern end of the Irish Sea Basin), sedimentary environment (grossly depositional) and the fact that the lowstand predicted for the Belfast Lough area by a recent version of the GIA model (-16.5 m) differs significantly from the (limited) extant observational data, which interprets the lowstand at -30 m. In 2011 and 2012 we gathered new multi-beam echo-sounder data, >200 km trackline pinger- and boomer- seismic reflection data and 46 vibrocores in Belfast Lough. Radiocarbon dating and palaeoenvironmental analysis are used to constrain the interpretation of the seismic and sediment data. Five seismo-stratigraphic units are interpreted, with a distinct erosional surface between U3 and U4 interpreted as a transgressive surface associated with sea level rise post-dating a RSL lowstand. Foraminiferal evidence indicates an increase in marine species (from lagoonal/estuarine to fully marine) from U4 to U5. Integration of the seismic and core data indicate an erosional event prior to 12.7 cal yr BP resulting in a planated surface in the inner Lough and wave-eroded drumlins at the mouth of the Lough between -15 and -22 m, interpreted as a possible slowstand. On the basis of seismic evidence in the outer Lough, an as yet undated lowstand at -42 m is tentatively interpreted to pre-date this stillstand. These results will be used to tune the Earth and ice model parameters in a new run of the GIA model.

Post-glacial sea-level history for NE Ireland (Belfast Lough) based on offshore evidence

NASA Astrophysics Data System (ADS)

Quinn, Rory; Plets, Ruth; Callard, Louise; Cooper, Andrew; Antony, Long; Daniel, Belknap; Robin, Edwards; Derek, Jackson; Joseph, Kelley; David, Long; Glenn, Milne; Xavier, Monteys

2014-05-01

Glacio-isostatic adjustment (GIA) models suggest a complex relative sea-level (RSL) pattern around the Irish Sea Basin after the Last Glacial Maximum (LGM), with modelled sea-level lowstands ranging from -12 m in the north to greater than -60 m in the south of the Basin. However, these GIA models are poorly constrained by observational data offshore. Belfast Lough, on the NE coast of Ireland, is one of seven sites chosen to investigate this complex RSL history as part of the project 'Late Glacial Sea level minima in the Western British Isles' (NERC NE/H024301/1). Belfast Lough was chosen as one of the candidate sites on the basis of location (at the northern end of the Irish Sea Basin), sedimentary environment (grossly depositional) and the fact that the lowstand predicted for the Belfast Lough area by a recent version of the GIA model (-16.5 m) differs significantly from the (limited) extant observational data, which interprets the lowstand at -30 m. In 2011 and 2012 we gathered new multi-beam echo-sounder data, >200 km trackline pinger- and boomer- seismic reflection data and 46 vibrocores in Belfast Lough. Radiocarbon dating and palaeoenvironmental analysis are used to constrain the interpretation of the seismic and sediment data. Five seismo-stratigraphic units are interpreted, with a distinct erosional surface between U3 and U4 interpreted as a transgressive surface associated with sea level rise post-dating a RSL lowstand. Foraminiferal evidence indicates an increase in marine species (from lagoonal/estuarine to fully marine) from U4 to U5. Integration of the seismic and core data indicate an erosional event prior to 12.7 cal yr BP resulting in a planated surface in the inner Lough and wave-eroded drumlins at the mouth of the Lough between -15 and -22 m, interpreted as a possible slowstand. On the basis of seismic evidence in the outer Lough, an as yet undated lowstand at -42 m is tentatively interpreted to pre-date this stillstand. These results will be used to tune the Earth and ice model parameters in a new run of the GIA model.

Drowned reefs and antecedent karst topography, Au'au channel, S.E. Hawaiian Islands

USGS Publications Warehouse

Grigg, R.W.; Grossman, E.E.; Earle, S.A.; Gittings, S.R.; Lott, D.; McDonough, J.

2002-01-01

During the last glacial maximum (LGM), about 21,000 years ago, the Hawaiian Islands of Maui, Lanai, and Molokai were interconnected by limestone bridges, creating a super-island known as Maui-Nui. Approximately 120 m of sea-level rise during the Holocene Transgression flooded, and then drowned, these bridges separating the islands by inter-island channels. A new multibeam high-resolution bathymetric survey of the channels between the islands, coupled with observations and video-transects utilizing DeepWorker-2000 submersibles, has revealed the existence of numerous drowned reef features including concentric solution basins, solution ridges (rims), sand and sediment plains, and conical-shaped reef pinnacles. The concentric basins contain flat lagoon-like bottoms that are rimmed by steep-sided limestone walls. Undercut notches rim the basins at several depths, marking either sea-level still stands or paleo-lake levels. All of the solution basins shallower than 120 m were subaerial at the LGM, and at one stage or another may have been shallow shoreline lakes. Today, about 70 drowned reef pinnacles are scattered across the Maui-Lanai underwater bridge and all are situated in wave-sheltered positions. Most drowned during the interval between 14,000 and 10,000 years ago when sea-level rise averaged 15 mm/year. Virtually all of the surficial topography in the Au'au Channel today is a product of karst processes accentuated by marginal reef growth during the Holocene. Both the submerged basins and the drowned reefs represent an archive of sea-level and climate history in Hawaii during the late Quaternary.

Elemental composition of commercial sea cucumbers (holothurians).

PubMed

Wen, J; Hu, C

2010-01-01

Toxic and essential elements in 11 different sea cucumber species were determined and compared with daily intake recommendations and maximum allowed levels. The contents of macro-elements contents in dried sea cucumber samples were found to be 25,000-152,000 mg kg(-1) for Na, 4000-8600 mg kg(-1) for Mg, 1100-5200 mg kg(-1) for K, 15,000-68,000 mg kg(-1) and 36,300-251,000 mg kg(-1) for Cl. Trace element concentrations in dried sea cucumber samples were found to be 11-100 mg kg(-1) for Zn, 41-660 mg kg(-1) for Fe, 3-74 mg kg(-1) for Cu, 1.1-16 mg kg(-1) for Mn, 1.4-3.7 mg kg(-1) for Se, 1.1-9.6 mg kg(-1) for Cr, and 0.3-5.1 mg kg(-1) for Ni. All sea cucumber species were rich sources of Na, Cl, Mg, Ca, Fe, Cu, Se and Cr for human consumption. Regarding contaminants, As, Cd and Pb concentrations in dried sea cucumbers were in the ranges of 1.1-6.1, 0.03-0.06 and 0.11-0.69 mg kg(-1), respectively. Moreover, Hg values of 11 sea cucumbers were below the detection limit (0.01 mg kg(-1)).

Mechanical stress induces neuroendocrine and immune responses of sea cucumber ( Apostichopus japonicus)

NASA Astrophysics Data System (ADS)

Tan, Jie; Li, Fenghui; Sun, Huiling; Gao, Fei; Yan, Jingping; Gai, Chunlei; Chen, Aihua; Wang, Qingyin

2015-04-01

Grading procedure in routine sea cucumber hatchery production is thought to affect juvenile sea cucumber immunological response. The present study investigated the impact of a 3-min mechanical perturbation mimicking the grading procedure on neuroendocrine and immune parameters of the sea cucumber Apostichopus japonicus. During the application of stress, concentrations of noradrenaline and dopamine in coelomic fluid increased significantly, indicating that the mechanical perturbation resulted in a transient state of stress in sea cucumbers. Coelomocytes concentration in coelomic fluid increased transiently after the beginning of stressing, and reached the maximum in 1 h. Whereas, coelomocytes phagocytosis at 3 min, superoxide anion production from 3 min to 0.5 h, acid phosphatase activity at 0.5 h, and phenoloxidase activity from 3 min to 0.5 h were all significantly down-regulated. All of the immune parameters recovered to baseline levels after the experiment was conducted for 8 h, and an immunostimulation occurred after the stress considering the phagocytosis and acid phosphatase activity. The results suggested that, as in other marine invertebrates, neuroendocrine/immune connections exist in sea cucumber A. japonicus. Mechanical stress can elicit a profound influence on sea cucumber neuroendocrine system. Neuroendocrine messengers act in turn to modulate the immunity functions. Therefore, these effects should be considered for developing better husbandry procedures.

The Impacts of Aerosols on Hurricane Katrina under the Effect of Air-Sea Coupling

NASA Astrophysics Data System (ADS)

Lin, Y.; Hsieh, J. S.; Wang, Y.; Zhang, R.

2017-12-01

Aerosols can affect the development of tropical cyclones, which often involve intense interactions with the ocean. Therefore, the impacts of aerosols on the tropical cyclones are reckoned closely associated with the effect of ocean feedback, a priori, which has often been omitted by most of the previous modeling studies about the aerosol effects on tropical cyclones. We investigate the synergetic effects of aerosols and ocean feedback on the development of hurricane Katrina using a convection-resolving coupled regional model (WRF-ROMS). In comparison with observations, our coupled simulation under pristine aerosol condition well captures the pressure drop near the center of Katrina with maximum mean sea level pressure in good agreement with the observation albeit the simulated maximal wind speed is relatively weaker than the observation. Preliminary results suggest that the ocean feedback tends to work with (against) aerosols to suppress (enhance) the hurricane's center pressure drop/maximum wind intensity at the developing (decaying) stage, suggesting a positive (negative) feedback to the aerosols' suppression effect on hurricanes. Moreover, the size of the simulated hurricane considerably expands due to the elevated polluted aerosols while the expansion is weakened, along with the increased precipitation, by the effect of air-sea interactions during the developing stage, which demonstrates intricate nonlinear interactions between aerosols, the hurricane and the ocean.

The relative contribution of waves, tides, and nontidal residuals to extreme total water levels on U.S. West Coast sandy beaches

USGS Publications Warehouse

Serafin, Katherine A.; Ruggiero, Peter; Stockdon, Hilary F.

2017-01-01

To better understand how individual processes combine to cause flooding and erosion events, we investigate the relative contribution of tides, waves, and nontidal residuals to extreme total water levels (TWLs) at the shoreline of U.S. West Coast sandy beaches. Extreme TWLs, defined as the observed annual maximum event and the simulated 100 year return level event, peak in Washington, and are on average larger in Washington and Oregon than in California. The relative contribution of wave-induced and still water levels (SWL) to the 100 year TWL event is similar to that of the annual maximum event; however, the contribution of storm surge to the SWL doubles across events. Understanding the regional variability of TWLs will lead to a better understanding of how sea level rise, changes in storminess, and possible changes in the frequency of major El Niños may impact future coastal flooding and erosion along the U.S. West Coast and elsewhere.

Sequence stratigraphy of the Monterey Formation, Santa Barbara County: Integration of physical, chemical, and biofacies data from outcrop and subsurface

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

Bohacs, K.M.

1990-05-01

Deep basinal rocks of the Monterey Formation can be allocated to different depositional environments based on an integration of bedding, facies stacking patterns, lithology, biofacies, and inorganic and organic chemistry. These rocks show evidence of systematic changes in depositional environments that can be related to eustatic sea level change and basin evolution. Even deep-basinal environments are affected by changing sea level through changes in circulation patterns and intensities nutrient budgets and dispersal patterns, and location and intensity of the oceanic oxygen minimum. The sequence-stratigraphic framework was constructed based on the physical expression of the outcrop strata and confirmed by typingmore » the outcrop sections to an integrated well-log/seismic grid through outcrop gamma-ray-spectral profiles. Interpretation of a sequence boundary was based on increased proportions of hemipelagic facies, evidence of increased bottom-energy levels above the boundary, and local erosion and relief on the surface. The proportion of shallower water and reworked dinoflagellates increased to a local maximum above the boundary, Downlap surfaces exhibited increased proportions of pelagic facies around the surface, evidence of decreased bottom-energy levels and terrigenous sedimentation rates, and little or no significant erosion on the surface. The proportion of deeper water dinoflagellates increased to a local maximum at or near the downlap surface; there was no evidence of reworked individuals. The detailed sequence-stratigraphic framework makes it possible to the rock properties to genetic processes for construction of predictive models.« less

Crustal subsidence rate off Hawaii determined from sup 234 U/ sup 238 U ages of drowned coral reefs

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

Ludwig, K.R.; Szabo, B.J.; Simmons, K.R.

1991-02-01

A series of submerged coral reefs off northwestern Hawaii was formed during (largely glacial) intervals when the rate of local sea-level rise was less than the maximum upward growth rate of the reefs. Mass-spectrometric {sup 234}U/{sup 238}U ages for samples from six such reefs range from 17 to 475 ka and indicate that this part of the Hawaiian Ridge has been subsiding at a roughly uniform rate of 2.6 mm/yr for the past 475 ka. The {sup 234}U/{sup 238}U ages are in general agreement with model ages of reef drowning (based on estimates of paleo-sea-level stands derived from oxygen-isotope ratiosmore » of deep-sea sediments), but there are disagreements in detail. The high attainable precision ({plus minus}10 ka or better on samples younger than {approximately}800 ka), large applicable age range, relative robustness against open-system behavior, and ease of analysis for this technique hold great promise for future applications of dating of 50-1,000 ka coral.« less

Anomalous Variability in Antarctic Sea Ice Extents During the 1960s With the Use of Nimbus Data

NASA Technical Reports Server (NTRS)

Gallaher, David W.; Campbell, G. Garrett; Meier, Walter N.

2014-01-01

The Nimbus I, II, and III satellites provide a new opportunity for climate studies in the 1960s. The rescue of the visible and infrared imager data resulted in the utilization of the early Nimbus data to determine sea ice extent. A qualitative analysis of the early NASA Nimbus missions has revealed Antarctic sea ice extents that are signicant larger and smaller than the historic 1979-2012 passive microwave record. The September 1964 ice mean area is 19.7x10 km +/- 0.3x10 km. This is more the 250,000 km greater than the 19.44x10 km seen in the new 2012 historic maximum. However, in August 1966 the maximum sea ice extent fell to 15.9x10 km +/- 0.3x10 km. This is more than 1.5x10 km below the passive microwave record of 17.5x10 km set in September of 1986. This variation between 1964 and 1966 represents a change of maximum sea ice of over 3x10 km in just two years. These inter-annual variations while large, are small when compared to the Antarctic seasonal cycle.

The structure of the stably stratified internal boundary layer in offshore flow over the sea

NASA Astrophysics Data System (ADS)

Garratt, J. R.; Ryan, B. F.

1989-04-01

Observations obtained mainly from a research aircraft are presented of the mean and turbulent structure of the stably stratified internal boundary layer (IBL) over the sea formed by warm air advection from land to sea. The potential temperature and humidity fields reveal the vertical extent of the IBL, for fetches out to several hundred of kilometres, geostrophic winds of 20 25 m s-1, and potential temperature differences between undisturbed continental air and the sea surface of 7 to 17 K. The dependence of IBL depth on these external parameters is discussed in the context of the numerical results of Garratt (1987), and some discrepancies are noted. Wind observations show the development of a low-level wind maximum (wind component normal to the coast) and rotation of the wind to smaller cross-isobar flow angles. Potential temperature (θ) profiles within the IBL reveal quite a different structure to that found in the nocturnal boundary layer (NBL) over land. Over the sea, θ profiles have large positive curvature with vertical gradients increasing monotonically with height; this reflects the dominance of turbulent cooling within the layer. The behaviour is consistent with known behaviour in the NBL over land where curvature becomes negative (vertical gradients of θ decreasing with height) as radiative cooling becomes dominant. Turbulent properties are discussed in terms of non-dimensional quantities, normalised by the surface friction velocity, as functions of normalised height using the IBL depth. Vertical profiles of these and the normalised wavelength of the spectral maximum agree well with known results for the stable boundary layer over land (Caughey et al., 1979).

Properties, formation, and dissipation of the North Pacific Eastern Subtropical Mode Water and its impact on interannual spiciness anomalies

NASA Astrophysics Data System (ADS)

Katsura, Shota

2018-03-01

The properties, formation, and dissipation of the North Pacific Eastern Subtropical Mode Water (ESTMW), their interannual variability, and impact on spiciness anomalies in the upper permanent pycnocline were investigated using Argo profiling float data in 2005-2015. The core temperature and salinity of ESTMWs were horizontally compensated to a constant density, and core potential density concentrates in a range of 24.5-25.2 kg m-3 with two distinct peaks. ESTMWs showed different spatial distribution and persistence for its core potential density. Denser ESTMWs with a potential density of 24.9-25.2 kg m-3 were formed in winter mixed layer depth maximum centered at 30°N, 140°W and lighter ESTMWs of 24.5-24.9 kg m-3 were formed south and east of it. After formation through shoaling of the winter mixed layer, the former persisted until the following autumn and a small part of it subducted in winter, while the latter dissipated in summer. The formation region of ESTMW corresponded to the summer sea surface density maximum resulting from its poleward sea surface salinity front. Sea surface density maximum maintains weak stratification during summer, preconditioning the deepening of the winter mixed layer and hence the formation of ESTMWs. A relationship between the ESTMW formation region and the summer sea surface density maximum was also found in the North Atlantic and the South Pacific, implying the importance of sea surface salinity fronts and the associated summer sea surface density maximum to ESTMW formation. Interannual variations of ESTMW reflected that of the winter mixed layer in its formation region, and the thickness of ESTMW was related to the Pacific decadal oscillation. ESTMW contributed to the occurrence of spice injection and affected spiciness anomalies in the upper permanent pycnocline through its formation and dissipation.

Rectification of Atmospheric Intraseasonal Oscillations on Seasonal to Interannual Sea Surface Temperature in the Indian Ocean

NASA Astrophysics Data System (ADS)

Duncan, B.; Han, W.

2010-12-01

An ocean general circulation model (the Hybrid Coordinate Ocean Model, HYCOM) is used to examine the rectification of atmospheric intraseasonal oscillations (ISOs) on lower-frequency seasonal to interannual sea surface temperatures (SSTs) in the Indian Ocean (IO). Existing studies have shown that ISOs rectify on low-frequency equatorial surface currents, suggesting that they may also have important impacts on low-frequency SST variability. To evaluate these impacts, a hierarchy of experiments is run with HYCOM that isolates the ocean response to atmospheric forcing by 10-30 day (submonthly), 30-90 day (dominated by the Madden-Julian Oscillation), and 10-90 day (all ISO) events. Other experiments isolate the ocean response to a range of forcing processes including shortwave radiation, precipitation, and winds. Results indicate that ISOs have a non-negligible effect on the seasonal and annual cycles of SST in the Arabian Sea. The maximum seasonal SST variability in the Arabian Sea is 1.6°C, while the ISO-forced seasonal SST variability has a maximum of 0.4°C. Because SSTs in the Arabian Sea are already warm (>28°C), a change of 0.4°C can affect convection there. ISOs also have non-negligible effects on the seasonal variability of SST in the south- and west- equatorial IO. The ISO contribution to the seasonal cycle of mixed layer thickness (hmix) in the eastern equatorial IO has a maximum of 9m, while the total hmix seasonal cycle has a maximum of 14m. ISOs affect the hmix seasonal cycle by up to 10m in the Arabian Sea, where the total seasonal cycle has a maximum of 75m. Further work will seek to explain the causes of this observed rectification of ISOs on seasonal SST and mixed layer variability, and to extend our results to include interannual timescales.

34 CFR 654.50 - How does an SEA disburse scholarship funds?

Code of Federal Regulations, 2011 CFR

2011-07-01

... 34 Education 3 2011-07-01 2011-07-01 false How does an SEA disburse scholarship funds? 654.50... Receive Scholarship Payments? § 654.50 How does an SEA disburse scholarship funds? (a) Except as provided in paragraph (b) of this section, the SEA shall disburse $1,500 for each year of study for a maximum...

34 CFR 654.50 - How does an SEA disburse scholarship funds?

Code of Federal Regulations, 2010 CFR

2010-07-01

... 34 Education 3 2010-07-01 2010-07-01 false How does an SEA disburse scholarship funds? 654.50... Receive Scholarship Payments? § 654.50 How does an SEA disburse scholarship funds? (a) Except as provided in paragraph (b) of this section, the SEA shall disburse $1,500 for each year of study for a maximum...

34 CFR 654.50 - How does an SEA disburse scholarship funds?

Code of Federal Regulations, 2014 CFR

2014-07-01

... 34 Education 3 2014-07-01 2014-07-01 false How does an SEA disburse scholarship funds? 654.50... Receive Scholarship Payments? § 654.50 How does an SEA disburse scholarship funds? (a) Except as provided in paragraph (b) of this section, the SEA shall disburse $1,500 for each year of study for a maximum...

34 CFR 654.50 - How does an SEA disburse scholarship funds?

Code of Federal Regulations, 2013 CFR

2013-07-01

... 34 Education 3 2013-07-01 2013-07-01 false How does an SEA disburse scholarship funds? 654.50... Receive Scholarship Payments? § 654.50 How does an SEA disburse scholarship funds? (a) Except as provided in paragraph (b) of this section, the SEA shall disburse $1,500 for each year of study for a maximum...

34 CFR 654.50 - How does an SEA disburse scholarship funds?

Code of Federal Regulations, 2012 CFR

2012-07-01

... 34 Education 3 2012-07-01 2012-07-01 false How does an SEA disburse scholarship funds? 654.50... Receive Scholarship Payments? § 654.50 How does an SEA disburse scholarship funds? (a) Except as provided in paragraph (b) of this section, the SEA shall disburse $1,500 for each year of study for a maximum...

Foehn-induced effects on local dust pollution, frontal clouds and solar radiation in the Dead Sea valley

NASA Astrophysics Data System (ADS)

Kishcha, Pavel; Starobinets, Boris; Savir, Amit; Alpert, Pinhas; Kaplan, Michael

2018-06-01

Despite the long history of investigation of foehn phenomena, there are few studies of the influence of foehn winds on air pollution and none in the Dead Sea valley. For the first time the foehn phenomenon and its effects on local dust pollution, frontal cloudiness and surface solar radiation were analyzed in the Dead Sea valley, as it occurred on 22 March 2013. This was carried out using both numerical simulations and observations. The foehn winds intensified local dust emissions, while the foehn-induced temperature inversion trapped dust particles beneath this inversion. These two factors caused extreme surface dust concentration in the western Dead Sea valley. The dust pollution was transported by west winds eastward, to the central Dead Sea valley, where the speed of these winds sharply decreased. The transported dust was captured by the ascending airflow contributing to the maximum aerosol optical depth (AOD) over the central Dead Sea valley. On the day under study, the maximum surface dust concentration did not coincide with the maximum AOD: this being one of the specific effects of the foehn phenomenon on dust pollution in the Dead Sea valley. Radar data showed a passage of frontal cloudiness through the area of the Dead Sea valley leading to a sharp drop in noon solar radiation. The descending airflow over the downwind side of the Judean Mountains led to the formation of a cloud-free band followed by only the partial recovery of solar radiation because of the extreme dust pollution caused by foehn winds.

The angular distributions of ultraviolet spectral irradiance at different solar elevation angles under clear sky conditions

NASA Astrophysics Data System (ADS)

Liu, Yan; Hu, LiWen; Wang, Fang; Gao, YanYan; Zheng, Yang; Wang, Yu; Liu, Yang

2016-01-01

To investigate the angular distributions of UVA, UVB, and effective UV for erythema and vitamin D (vitD) synthesis, the UV spectral irradiances were measured at ten inclined angles (from 0° to 90°) and seven azimuths (from 0° to 180°) at solar elevation angle (SEA) that ranged from 18.8° to 80° in Shanghai (31.22° N, 121.55° E) under clear sky and the albedo of ground was 0.1. The results demonstrated that in the mean azimuths and with the back to the sun, the UVA, UVB, and erythemally and vitD-weighted irradiances increased with the inclined angles and an increase in SEA. When facing toward the sun at 0°-60° inclined angles, the UVA first increased and then decreased with an increase in SEA; at other inclined angles, the UVA increased with SEA. At 0°-40° inclined angles, the UVB and erythemally and vitD-weighted irradiances first increased and then decreased with an increase in SEA, and their maximums were achieved at SEA 68.7°; at other inclined angles, the above three irradiances increased with an increase in SEA. The maximum UVA, UVB, and erythemally and vitD-weighted irradiances were achieved at an 80° inclined angle at SEA 80° (the highest in our measurements); the cumulative exposure of the half day achieved the maximum at a 60° inclined angle, but not on the horizontal. This study provides support for the assessment of human skin sun exposure.

Gridded climate data from 5 GCMs of the Last Glacial Maximum downscaled to 30 arc s for Europe

NASA Astrophysics Data System (ADS)

Schmatz, D. R.; Luterbacher, J.; Zimmermann, N. E.; Pearman, P. B.

2015-06-01

Studies of the impacts of historical, current and future global change require very high-resolution climate data (≤ 1 km) as a basis for modelled responses, meaning that data from digital climate models generally require substantial rescaling. Another shortcoming of available datasets on past climate is that the effects of sea level rise and fall are not considered. Without such information, the study of glacial refugia or early Holocene plant and animal migration are incomplete if not impossible. Sea level at the last glacial maximum (LGM) was approximately 125 m lower, creating substantial additional terrestrial area for which no current baseline data exist. Here, we introduce the development of a novel, gridded climate dataset for LGM that is both very high resolution (1 km) and extends to the LGM sea and land mask. We developed two methods to extend current terrestrial precipitation and temperature data to areas between the current and LGM coastlines. The absolute interpolation error is less than 1 and 0.5 °C for 98.9 and 87.8 %, respectively, of all pixels within two arc degrees of the current coastline. We use the change factor method with these newly assembled baseline data to downscale five global circulation models of LGM climate to a resolution of 1 km for Europe. As additional variables we calculate 19 "bioclimatic" variables, which are often used in climate change impact studies on biological diversity. The new LGM climate maps are well suited for analysing refugia and migration during Holocene warming following the LGM.

Monitoring Global Sea Level: Eustatic Variations, Local Variations, and Solid Earth Effects

NASA Technical Reports Server (NTRS)

Davis, James L.

2000-01-01

Project BIFROST (Baseline Inferences for Fennoscandian Rebound Observations. Sea-level and Tectonics) combines networks of continuously operating CPS receivers in Sweden and Finland to measure ongoing crustal deformation due to glacial isostatic adjustment, (CIA). We present an analysis of data collected in the years 1993-1998. We compare the CPS determinations of three-dimensional crustal motion to predictions calculated using the high resolution Fennoscandian deglaciation model recently proposed by Lambeck et al. We find that the the maximum observed uplift rate (approx. 10 mm/ yr) and the maximum predicted uplift rate agree to better than 1 mm/ yr. The patterns of uplift also agree quite well, although differences are discernible. The chi(exp 2) difference between predicted and GPS-observed radial rates is reduced by a factor of 5-6 compared to that for the "null" (no uplift) model, depending on whether a mean difference is first removed. The north components of velocity agree at about the same relative level. whereas the agreement for the east components is worse, a problem possibly related to the lack of bias fixing. We have also compared the values for the observed radial deformation rates to those based on sea-level rates from Baltic tide gauges. The weighted RMS difference between CPS and tide-gauge rates (after removing a mean) is 0.6 mm/ yr, giving an indication of the combined accuracy of the CPS and tide-gauge measurement systems. Spectral analysis of the time series of position estimates yields spectral indices in the range -1 to -2. An EOF analysis indicates, however, that much of this power is correlated among the sites. The correlation appears to be regional and falls off only slightly with distance. Some of this correlated noise is associated with snow accumulation on the antennas or, for those antennas with radomes, on the radomes. This problem has caused us to modify the radomes used several times, leading to one of our more significant sources of uncertainty.

Marine Fog over the Western Pacific Marginal Seas Based Upon Ship Observations for 1950 - 2007

NASA Astrophysics Data System (ADS)

Dorman, C. E.; Koracin, D. R.

2016-12-01

An analysis is presented of the marine fog distribution over the western Pacific marginal seas based upon the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) ship observations taken during 1950-2007. Fog occurrence is reported in routine weather reports that are encoded in an ICOADS ship observation. This includes the marginal seas of Okhotsk Sea, Japan Sea, Yellow Sea and South China Sea which have significant fog occurrences with values much greater than in the surrounding ocean with distinct seasonal trends but different generation mechanisms. The greatest occurrence is 55 % in Jun-Jul-Aug over the Okhotsk Sea followed by 28 % over the Japan Sea. This is seasonally controlled by the sea level pressure gradient moving air over a negative sea surface temperature gradient. During Dec-Jan-Feb, the SLP gradient reverses, moving cold, dry continental air over the Okhotsk and Japan Seas, eliminating any fog. The maximum fog over the Okhotsk Sea is over isolated locations with shallow water. In the Japan Sea, the most frequent fog occurs along the north side of the sea over a narrow shelf with the lowest SST of the entire Sea. In the Yellow Sea, the fog frequency peak is from Dec through May. In Mar-Apr-May the highest value is 18 % which is centered at 33 N 122 W while elevated values extend along the China coast to Taiwan. In Jun-Jul-Aug, highest values are mostly confined to the Yellow Sea. In Dec-Jan-Feb, decreased but significant fog occurrences extend along the entire China coast when the highest value in the Yellow Sea is 5 % and in South China Sea it is 6 %. The only other world marine fog occurrence analysis discovered by us is a US Department of Agriculture Jun-Jul-Aug marine fog frequency chart published in 1938 that does not show any fog in the Okhotsk Sea and misses most of the fog occurrence reported by ships in the Yellow Sea.

Application of Low cost Spirulina growth medium using Deep sea water

NASA Astrophysics Data System (ADS)

Lim, Dae-hack; Kim, Bong-ju; Lee, Sung-jae; Choi, Nag-chul; Park, Cheon-young

2017-04-01

Deep-sea water has a relatively constant temperature, abundant nutrients such as calcium, magnesium, nitrates, and phosphates, etc., and stable water quality, even though there might be some variations of their compositions according to collection places. Thus, deep-sea water would be a good substrate for algal growth and biomass production since it contains various nutrients, including a fluorescent red pigment, and β-carotene, etc. The aim of this study was to investigate the economics of a culture condition through comparative analysis to Spirulina platensis growth characteristic under various medium conditions for cost-effective production of Spirulina sp.. Growth experiments were performed with S. platensis under various culture medium conditions (deep sea water + SP medium). Growth tests for culture medium demonstrated that the deep sea water to SP medium ratio of 50:50(W/W) was effective in S. platensis with the maximum biomass (1.35g/L) and minimum medium making cost per production mass (133.28 KRW/g). Parameter estimation of bio-kinetics (maximum growth rate and yield) for low cost medium results showed that the maximum growth rate and yield of N, P, K were obtained under deep sea water to SP medium ratio of 50:50(W/W) of 0.057 1/day and 0.151, 0.076, 0.123, respectively. Acknowledgment : "This research was a part of the project titled 'Development of microalgae culture technique for cosmetic materials based on ocean deep sea water(20160297)', funded by the Ministry of Oceans and Fisheries, Korea."

Effect of commercial airline travel on oxygen saturation in athletes.

PubMed

Geertsema, C; Williams, A B; Dzendrowskyj, P; Hanna, C

2008-11-01

Aircraft cabins are pressurised to maximum effective altitudes of 2440 metres, resulting in significant decline in oxygen saturation in crew and passengers. This effect has not been studied in athletes. To investigate the degree of decline in oxygen saturation in athletes during long-haul flights. A prospective cross-sectional study. National-level athletes were recruited. Oxygen saturation and heart rate were measured with a pulse oximeter at sea level before departure, at 3 and 7 hours into the flight, and again after arrival at sea level. Aircraft cabin pressure and altitude, cabin fraction of inspired oxygen and true altitude were also recorded. 45 athletes and 18 healthy staff aged between 17 and 70 years were studied on 10 long-haul flights. Oxygen saturation levels declined significantly after 3 hours and 7 hours (3-4%), compared with sea level values. There was an associated drop in cabin pressure and fraction of inspired oxygen, and an increase in cabin altitude. Oxygen saturation declines significantly in athletes during long-haul commercial flights, in response to reduced cabin pressure. This may be relevant for altitude acclimatization planning by athletes, as the time spent on the plane should be considered time already spent at altitude, with associated physiological changes. For flights of 10-13 hours in duration, it will be difficult to arrive on the day of competition to avoid the influence of these changes, as is often suggested by coaches.

Sea-level and tectonic control of middle to late Pleistocene turbidite systems in Santa Monica Basin, offshore California

USGS Publications Warehouse

Normark, W.R.; Piper, D.J.W.; Sliter, R.

2006-01-01

Small turbidite systems offshore from southern California provide an opportunity to track sediment from river source through the turbidity-current initiation process to ultimate deposition, and to evaluate the impact of changing sea level and tectonics. The Santa Monica Basin is almost a closed system for terrigenous sediment input, and is supplied principally from the Santa Clara River. The Hueneme fan is supplied directly by the river, whereas the smaller Mugu and Dume fans are nourished by southward longshore drift. This study of the Late Quaternary turbidite fill of the Santa Monica Basin uses a dense grid of high-resolution seismic-reflection profiles tied to new radiocarbon ages for Ocean Drilling Program (ODP) Site 1015 back to 32 ka. Over the last glacial cycle, sedimentation rates in the distal part of Santa Monica Basin averaged 2-3 mm yr-1, with increases at times of extreme relative sea-level lowstand. Coarser-grained mid-fan lobes prograded into the basin from the Hueneme, Mugu and Dume fans at times of rapid sea-level fall. These pulses of coarse-grained sediment resulted from river channel incision and delta cannibalization. During the extreme lowstand of the last glacial maximum, sediment delivery was concentrated on the Hueneme Fan, with mean depositional rates of up to 13 mm yr-1 on the mid- and upper fan. During the marine isotope stage (MIS) 2 transgression, enhanced rates of sedimentation of > 4 mm yr-1 occurred on the Mugu and Dume fans, as a result of distributary switching and southward littoral drift providing nourishment to these fan systems. Longer-term sediment delivery to Santa Monica Basin was controlled by tectonics. Prior to MIS 10, the Anacapa ridge blocked the southward discharge of the Santa Clara River into the Santa Monica Basin. The pattern and distribution of turbidite sedimentation was strongly controlled by sea level through the rate of supply of coarse sediment and the style of initiation of turbidity currents. These two factors appear to have been more important than the absolute position of sea level. ?? 2006 The Authors. Journal compilation 2006 International Association of Sedimentologists.

A global compilation of coral sea-level benchmarks: Implications and new challenges

NASA Astrophysics Data System (ADS)

Medina-Elizalde, Martín

2013-01-01

I present a quality-controlled compilation of sea-level data from U-Th dated corals, encompassing 30 studies of 13 locations around the world. The compilation contains relative sea level (RSL) data from each location based on both conventional and open-system U-Th ages. I have applied a commonly used age quality control criterion based on the initial 234U/238U activity ratios of corals in order to select reliable ages and to reconstruct sea level histories for the last 150,000 yr. This analysis reveals scatter of RSL estimates among coeval coral benchmarks both within individual locations and between locations, particularly during Marine Isotope Stage (MIS) 5a and the glacial inception following the last interglacial. The character of data scatter during these time intervals imply that uncertainties still exist regarding tectonics, glacio-isostacy, U-series dating, and/or coral position. To elucidate robust underlying patterns, with confidence limits, I performed a Monte Carlo-style statistical analysis of the compiled coral data considering appropriate age and sea-level uncertainties. By its nature, such an analysis has the tendency to smooth/obscure millennial-scale (and finer) details that may be important in individual datasets, and favour the major underlying patterns that are supported by all datasets. This statistical analysis is thus functional to illustrate major trends that are statistically robust ('what we know'), trends that are suggested but still are supported by few data ('what we might know, subject to addition of more supporting data and improved corrections'), and which patterns/data are clear outliers ('unlikely to be realistic given the rest of the global data and possibly needing further adjustments'). Prior to the last glacial maximum and with the possible exception of the 130-120 ka period, available coral data generally have insufficient temporal resolution and unexplained scatter, which hinders identification of a well-defined pattern with usefully narrow confidence limits. This analysis thus provides a framework that objectively identifies critical targets for new data collection, improved corrections, and integration of coral data with independent, stratigraphically continuous methods of sea-level reconstruction.

Satellite altimetry in sea ice regions - detecting open water for estimating sea surface heights

NASA Astrophysics Data System (ADS)

Müller, Felix L.; Dettmering, Denise; Bosch, Wolfgang

2017-04-01

The Greenland Sea and the Farm Strait are transporting sea ice from the central Arctic ocean southwards. They are covered by a dynamic changing sea ice layer with significant influences on the Earth climate system. Between the sea ice there exist various sized open water areas known as leads, straight lined open water areas, and polynyas exhibiting a circular shape. Identifying these leads by satellite altimetry enables the extraction of sea surface height information. Analyzing the radar echoes, also called waveforms, provides information on the surface backscatter characteristics. For example waveforms reflected by calm water have a very narrow and single-peaked shape. Waveforms reflected by sea ice show more variability due to diffuse scattering. Here we analyze altimeter waveforms from different conventional pulse-limited satellite altimeters to separate open water and sea ice waveforms. An unsupervised classification approach employing partitional clustering algorithms such as K-medoids and memory-based classification methods such as K-nearest neighbor is used. The classification is based on six parameters derived from the waveform's shape, for example the maximum power or the peak's width. The open-water detection is quantitatively compared to SAR images processed while accounting for sea ice motion. The classification results are used to derive information about the temporal evolution of sea ice extent and sea surface heights. They allow to provide evidence on climate change relevant influences as for example Arctic sea level rise due to enhanced melting rates of Greenland's glaciers and an increasing fresh water influx into the Arctic ocean. Additionally, the sea ice cover extent analyzed over a long-time period provides an important indicator for a globally changing climate system.

Major episodes of geologic change - Correlations, time structure and possible causes

NASA Technical Reports Server (NTRS)

Rampino, Michael R.; Caldeira, Ken

1993-01-01

Published data sets of major geologic events of the past about 250 Myr (extinction events, sea-level lows, continental flood-basalt eruptions, mountain-building events, abrupt changes in sea-floor spreading, ocean-anoxic and blackshale events and the largest evaporite deposits) have been synthesized (with estimated errors). These events show evidence for a statistically significant periodic component with an underlying periodicity, formally equal to 26.6 Myr, and a recent maximum, close to the present time. The cycle may not be strictly periodic, but a periodicity of about 30 Myr is robust to probable errors in dating of the geologic events. The intervals of geologic change seem to involve jumps in sea-floor spreading associated with episodic continental rifting, volcanism, enhanced orogeny, global sea-level changes and fluctuations in climate. The period may represent a purely internal earth-pulsation, but evidence of planetesimal impacts at several extinction boundaries, and a possible underlying cycle of 28-36 Myr in crater ages, suggests that highly energetic impacts may be affecting global tectonics. A cyclic increase in the flux of planetesimals might result from the passage of the Solar System through the central plane of the Milky Way Galaxy - an event with a periodicity and mean phasing similar to that detected in the geologic changes.

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.

Tsunamis hazard assessment and monitoring for the Back Sea area

NASA Astrophysics Data System (ADS)

Partheniu, Raluca; Ionescu, Constantin; Constantin, Angela; Moldovan, Iren; Diaconescu, Mihail; Marmureanu, Alexandru; Radulian, Mircea; Toader, Victorin

2016-04-01

NIEP has improved lately its researches regarding tsunamis in the Black Sea. As part of the routine earthquake and tsunami monitoring activity, the first tsunami early-warning system in the Black Sea has been implemented in 2013 and is active during these last years. In order to monitor the seismic activity of the Black Sea, NIEP is using a total number of 114 real time stations and 2 seismic arrays, 18 of the stations being located in Dobrogea area, area situated in the vicinity of the Romanian Black Sea shore line. Moreover, there is a data exchange with the Black Sea surrounding countries involving the acquisition of real-time data for 17 stations from Bulgaria, Turkey, Georgia and Ukraine. This improves the capability of the Romanian Seismic Network to monitor and more accurately locate the earthquakes occurred in the Black Sea area. For tsunamis monitoring and warning, a number of 6 sea level monitoring stations, 1 infrasound barometer, 3 offshore marine buoys and 7 GPS/GNSS stations are installed in different locations along and near the Romanian shore line. In the framework of ASTARTE project, few objectives regarding the seismic hazard and tsunami waves height assessment for the Black Sea were accomplished. The seismic hazard estimation was based on statistical studies of the seismic sources and their characteristics, compiled using different seismic catalogues. Two probabilistic methods were used for the evaluation of the seismic hazard, the Cornell method, based on the Gutenberg Richter distribution parameters, and Gumbel method, based on extremes statistic. The results show maximum values of possible magnitudes and their recurrence periods, for each seismic source. Using the Tsunami Analysis Tool (TAT) software, a set of tsunami modelling scenarios have been generated for Shabla area, the seismic source that could mostly affect the Romanian shore. These simulations are structured in a database, in order to set maximum possible tsunami waves that could be generated and to establish minimum magnitude values that could trigger tsunamis in this area. Some particularities of Shabla source are: past observed magnitudes > 7 and a recurrence period of 175 years. Some other important objectives of NIEP are to continue the monitoring of the seismic activity of the Black Sea, to improve the data base of the tsunami simulations for this area, near real time fault plane solution estimations used for the warning system, and to add new seismic, GPS/GNSS and sea level monitoring equipment to the existing network. Acknowledgements: This work was partially supported by the FP7 FP7-ENV2013 6.4-3 "Assessment, Strategy And Risk Reduction For Tsunamis in Europe" (ASTARTE) Project 603839/2013 and PNII, Capacity Module III ASTARTE RO Project 268/2014. This work was partially supported by the "Global Tsunami Informal Monitoring Service - 2" (GTIMS2) Project, JRC/IPR/2015/G.2/2006/NC 260286, Ref. Ares (2015)1440256 - 01.04.2015.

Red Sea circulation during marine isotope stage 5e

NASA Astrophysics Data System (ADS)

Siccha, Michael; Biton, Eli; Gildor, Hezi

2015-04-01

We have employed a regional Massachusetts Institute of Technology oceanic general circulation model of the Red Sea to investigate its circulation during marine isotope stage (MIS) 5e, the peak of the last interglacial, approximately 125 ka before present. Compared to present-day conditions, MIS 5e was characterized by higher Northern Hemisphere summer insolation, accompanied by increases in air temperature of more than 2°C and global sea level approximately 8 m higher than today. As a consequence of the increased seasonality, intensified monsoonal conditions with increased winds, rainfall, and humidity in the Red Sea region are evident in speleothem records and supported by model simulations. To assess the dominant factors responsible for the observed changes, we conducted several sensitivity experiments in which the MIS 5 boundary conditions or forcing parameters were used individually. Overall, our model simulation for the last interglacial maximum reconstructs a Red Sea that is colder, less ventilated and probably more oligotrophic than at present day. The largest alteration in Red Sea circulation and properties was found for the simulation of the northward displacement and intensification of the African tropical rain belt during MIS 5e, leading to a notable increase in the fresh water flux into the Red Sea. Such an increase significantly reduced the Red Sea salinity and exchange volume of the Red Sea with the Gulf of Aden. The Red Sea reacted to the MIS 5e insolation forcing by the expected increase in seasonal sea surface temperature amplitude and overall cooling caused by lower temperatures during deep water formation in winter.

On the tidally driven circulation in the South China Sea: modeling and analysis

NASA Astrophysics Data System (ADS)

Nelko, Varjola; Saha, Abhishek; Chua, Vivien P.

2014-03-01

The South China Sea is a large marginal sea surrounded by land masses and island chains, and characterized by complex bathymetry and irregular coastlines. An unstructured-grid SUNTANS model is employed to perform depth-averaged simulations of the circulation in the South China Sea. The model is tidally forced at the open ocean boundaries using the eight main tidal constituents as derived from the OSU Tidal Prediction Software. The model simulations are performed for the year 2005 using a time step of 60 s. The model reproduces the spring-neap and diurnal and semidiurnal variability in the observed data. Skill assessment of the model is performed by comparing model-predicted surface elevations with observations. For stations located in the central region of the South China Sea, the root mean squared errors (RMSE) are less than 10 % and the Pearson's correlation coefficient ( r) is as high as 0.9. The simulations show that the quality of the model prediction is dependent on the horizontal grid resolution, coastline accuracy, and boundary locations. The maximum RMSE errors and minimum correlation coefficients occur at Kaohsiung (located in northern South China Sea off Taiwan coast) and Tioman (located in southern South China Sea off Malaysia coast). This may be explained with spectral analysis of sea level residuals and winds, which reveal dynamics at Kaohsiung and Tioman are strongly influenced by the seasonal monsoon winds. Our model demonstrates the importance of tidally driven circulation in the central region of the South China Sea.

Ecological effects of co-culturing sea cucumber Apostichopus japonicus (Selenka) with scallop Chlamys farreri in earthen ponds

NASA Astrophysics Data System (ADS)

Ren, Yichao; Dong, Shuanglin; Qin, Chuanxin; Wang, Fang; Tian, Xiangli; Gao, Qinfeng

2012-01-01

Monthly changes in sedimentation and sediment properties were studied for three different culture treatments: sea cucumber monoculture (Mc), sea cucumber and scallop polyculture (Ps-c) and scallop monoculture (Ms). Results indicated that the survival rate of sea cucumber was significantly higher in Ps-c cultures than in Mc cultures. Sea cucumber yield was 69.6% higher in Ps-c culture than in Mc culture. No significant differences in body weight and scallop shell length were found between Ps-c and Ms cultures. The mean sedimentation rate of total particulate matter (TPM) was 72.2 g/(m2·d) in Ps-c cultures, with a maximum of 119.7 g/(m2·d), which was markedly higher than that of Mc (mean value). Sedimentation rates of organic matter (OM), total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) in Ps-c cultures were also significantly higher than those in Mc cultures. TOC and TN contents of sediment increased rapidly in the first 5 months in Ms cultures and remained at a high level. TOC and TN contents in Mc and Ps-c cultures decreased during sea cucumber feeding seasons and increased during sea cucumber dormancy periods (summer and winter). The study demonstrates that co-culture of sea cucumber and scallop in earthen ponds is an alternative way to alleviate nutrient loads and improve water quality in coastal aquaculture systems. Moreover, it provides the additional benefit of an increased sea cucumber yield.

Measurement of cardiopulmonary performance during acute exposure to a 2440-m equivalent atmosphere

NASA Technical Reports Server (NTRS)

Levitan, B. M.; Bungo, M. W.

1982-01-01

Each of 20 subjects (ranging in age from 18 to 38 years, 15 being male, five female) was given two Bruce Protocol symptom-limited maximum treadmill stress tests, breathing sea-level compressed air (20.9% O2) for one test and a 2440-m equivalent (15.5% O2) for the other. A significant difference was found to exist between measured VO2 max (p less than 0.0002) and exercise time (p less than 0.0004) for the two conditions. No significant differences were observed in heart rate or the recovery time to a respiratory quotient of less than 1. Hemoglobin saturation, as measured by an ear oximeter, averaged 95% for sea-level and 91% for the 2440-m equivalent gases. These results support a 2440-m equivalent contingency atmosphere in the Space Shuttle prior to donning a low-pressure suit for the purpose reducing nitrogen washout times.

Climatological aspects of mesoscale cyclogenesis over the Ross Sea and Ross Ice shelf regions of Antarctica

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

Carrasco, J.F.; Bromwich, D.H.

1994-11-01

A one-year (1988) statistical study of mesoscale cyclogenesis near Terra Nova Bay and Byrd Glacier, Antarctica, was conducted using high-resolution digital satellite imagery and automatic weather station data. Results indicate that on average two (one) mesoscale cyclones form near Terra Nova Bay (Byrd Glacier) each week, confirming these two locations as mesoscale cyclogeneis areas. The maximum (minimum) weekly frequency of mesoscale cyclones occurred during the summer (winter). The satellite survey of mesoscale vortices was extended over the Ross Sea and Ross Ice Shelf. Results suggest southern Marie Byrd Land as another area of mesoscale cyclone formation. Also, frequent mesoscale cyclonicmore » activity was noted over the Ross Sea and Ross Ice Shelf, where, on average, six and three mesoscale vortices were observed each week, respectively, with maximum (minimum) frequency during summer (winter) in both regions. The majority (70-80%) of the vortices were of comma-cloud type and were shallow. Only around 10% of the vortices near Terra Nova Bay and Byrd Glacier were classified as deep vortices, while over the Ross Sea and Ross Ice Shelf around 20% were found to be deep. The average large-scale pattern associated with cyclogenesis days near Terra Nova Bay suggests a slight decrease in the sea level pressure and 500-hPa geopotential height to the northwest of this area with respect to the annual average. This may be an indication of the average position of synoptic-scale cyclones entering the Ross Sea region. Comparison with a similar study but for 1984-85 shows that the overall mesoscale cyclogenesis activity was similar during the three years, but 1985 was found to be the year with greater occurrence of {open_quotes}significant{close_quotes} mesoscales cyclones. The large-scale pattern indicates that this greater activity is related to a deeper circumpolar trough and 500-hPa polar vortex for 1985 in comparison to 1984 and 1988. 64 refs., 13 figs., 5 tabs.« less

Phylogeographic and population insights of the Asian common toad (Bufo gargarizans) in Korea and China: population isolation and expansions as response to the ice ages

PubMed Central

Santos, Joana L.; Sánchez-RamÍrez, Santiago; Bae, Yoonhyuk; Jang, Yikweon

2017-01-01

The effects of ice ages on speciation have been well documented for many European and North American taxa. In contrast, very few studies have addressed the consequences of such environmental and topographical changes in North East Asian species. More precisely, the Korean Peninsula offers a unique model to assess patterns and processes of speciation as it hosts the northern- and eastern-most distribution limit of some widespread Asian taxa. Despite this, studies addressing phylogeographic patterns and population genetics in the peninsula and surrounding countries are few and studies for most families are lacking. Here we inferred the phylogenetic relationships of the common toad (Bufo gargarizans) from South Korea and their North East Asian counterpart populations, based on mitochondrial data. Korean B. gargarizans GenBank BLASTs matched few individuals from nearby China, but the presence of a Korean clade suggests isolation on the Korean Peninsula, previous to the last glacial maximum, linked to sea level resurgence. Molecular clock calibrations within this group were used to date the divergence between clades and their relationship to paleo-climatic events in the area. Lack of genetic structure among South Korean populations and strong homogeneity between the Korean and some Chinese localities suggest weak isolation and recent expansion. Geographical projection of continuous coalescent maximum-clade-credibility trees shows an original Chinese expansion towards the Korean Peninsula through the Yellow Sea circa two million years ago with colonisation events dating circa 800 thousand years ago (K. y. a.). Following this colonisation, the data point to outgoing Korean Peninsula dispersal events throughout different periods, towards the North through land, and West through land bridge formations over the Yellow Sea during sea level falls. In accordance, demographic analyses revealed a population expansion in the Koran Peninsula circa 300 K. y. a., likely attributed to glacial cycle fluctuations. PMID:29201561

Foraminifera and the ecology of sea grass communities since the late Cretaceous

NASA Astrophysics Data System (ADS)

Hart, Malcolm; Smart, Christopher; Jagt, John

2016-04-01

Sea grasses are marine angiosperms (plants) that, in the late Cretaceous, migrated from the land into shallow-water marine environments. They represent a distinct, but fragile, marine habitat and sea grass meadows are often regarded as biodiversity hot-spots with a range of species (including fish, sea horses and cuttlefish) using them as nurseries for their young. Foraminifera are often found associated with sea grass meadows, with the associated taxa reflecting both the environment and palaeolatitude. In the tropics and sub-tropics, miliolid foraminifera dominate (e.g., Peneroplis spp.) as do large discoidal taxa such as Marginopora and Calcarina. In temperate to cool latitudes the assemblage changes to one dominated by smaller benthic taxa, including Elphidium spp. One taxon, Elphidium crispum, is geotropic and is often found - in the summer months - to crowd the fronds of the sea grass. In the Gulpen and Maastricht formations of the Maastricht area (The Netherlands and Belgium) sea grass fossils (both fronds and rhizomes) have been recorded in association with assemblages of both larger and smaller benthic foraminifera (Hart et al., 2016). Some of the large discoidal forms (e.g., Omphalocyclus and Orbitoides/Lepidorbitoides) and the distinctive Siderolites are associated with these sea grass fossils and are suggestive of the modern sea grass communities of sub-tropical areas. While earlier records were of relatively isolated sea grasses, in September/October 2015 surfaces with abundant sea grasses were found that are suggestive of complete 'meadows'. Preservation of some silicified rhizomes indicates that silicification must have been very rapid, before any degradation or compaction of the delicate tissues. The presence of sea grass fossils and their associated benthic foraminifera is indicative of a clear, shallow-water seaway, with a maximum depth of 15-20 m. The reported variations in sea level during the latest Cretaceous cannot, therefore, have been very large as such a change in water depth would have been disastrous to such a fragile ecosystem. The fossil record of sea grasses in the Cenozoic is relatively limited, though there are some assemblages of benthic foraminifera that are suggestive of their presence, despite the lack of plant fossils. Hart, M.B., FitzPatrick, M.E.J. & Smart, C.W. 2016. The Cretaceous/Paleogene boundary: Foraminifera, sea grasses, sea level change and sequence stratigraphy. Palaeogeography, Palaeoclimatology, Palaeoecology, 441, 420-429.

Controlling factors of stratigraphic occurrences of fine-grained turbidites: Examples from the Japanese waters

NASA Astrophysics Data System (ADS)

Ikehara, K.

2017-12-01

Fine-grained turbidite has been used for subaqueous paleoseismology, and has been recognized from shallow- to deep-water environments around the Japanese islands. Stratigraphic occurrence of fine-grained turbidites in the deepest Beppu Bay, south Japan, with its water depth of 75 m suggest clear influence of sea-level changes. Turbidite frequency was high during the post glacial sea-level rising and last 2.7 ka, and was low during the Holocene maximum sea-level highstand (5.3-2.7 ka). Retreat and progress of coastal delta front of the nearby river might affect the sediment supply to the deepest basin. On the other hand, fine-grained turbidites found in the forearc basins ( 3500 and 4500 m in water depths) and trench floor ( 6000 m in water depth) along the southern Ryukyu arc have no clear relation with sea-level changes. Sediment and bathymetric characteristics suggest that origin of these fine-grained turbidites is Taiwan. Remarkable tectonic uplift of Taiwanese coast with small mountainous rivers and narrow shelf may produce the continuous supply of fine-grained turbidites in this area. The Japan Trench floor composes of a series of small basins reflecting subducting horst-graben structure of the Pacific Plate. Each small basin acts as a natural sediment trap receiving the earthquake-induced turbidity currents. Thick fine-grained turbidites are also occurred in the small basins in the Japan Trench floor ( 7500 m in water depth). These are most likely induced by huge earthquakes along the Japan Trench. Thus, their stratigraphic occurrences might have close relation with recurrence of huge earthquakes in the past.

Stratigraphic Evidence for Environmental Change in a Bermudian Coastal Underwater Cave (Palm Cave System) in Response to Holocene Sea-level Rise

NASA Astrophysics Data System (ADS)

Cresswell, J. N.; van Hengstum, P. J.; Iliffe, T. M.

2016-12-01

Unique environments exist worldwide in coastal underwater caves, including those from Bermuda, which has been a global epicenter for interdisciplinary cave research. However, the development of environments, ecosystems, and sedimentary deposits in coastal underwater caves, particularly over millennial timescales is poorly understood, with previous research from Bermuda indicating a critical role for sea-level rise in driving environmental change. A multi-proxy stratigraphic analysis of 14 sediment cores that were collected from the Palm Cave System in Bermuda from 2 m to 20 m water depths was conducted to better understand Holocene-scale environmental change in coastal underwater caves (e.g., textural analysis, x-radiographs, microfossil analysis, radiocarbon dating). The rate of deposition was found to be variable throughout time and dependent upon the proximity of core locations to cave openings (`karst windows') and conduit geometry. The oldest recovered sediment was likely Pleistocene-aged, terra-rosa soil deposits that predate the Holocene inundation. By 9500 Cal yrs BP, deposition was dominated by organic-rich facies (gyttja), with agglutinated brackish foraminifera (Trochammina, Polysaccammina) and bivalves indicating brackish aquatic conditions in the system by 9200 Cal yrs BP. A system-wide shift to carbonate deposition occurred 8500 Cal yrs BP, which indicates the onset of oxygenated marine water entering the cave and development of a marine-dominated (i.e., submarine) cave environment. Comparison with local maximum sea-level indicators shows that inundation of the Bermuda platform by Holocene sea-level rise likely drove environmental change in the Palm Cave System.

Dynamic changes in the interchromosomal interaction of early histone gene loci during development of sea urchin.

PubMed

Matsushita, Masaya; Ochiai, Hiroshi; Suzuki, Ken-Ichi T; Hayashi, Sayaka; Yamamoto, Takashi; Awazu, Akinori; Sakamoto, Naoaki

2017-12-15

The nuclear positioning and chromatin dynamics of eukaryotic genes are closely related to the regulation of gene expression, but they have not been well examined during early development, which is accompanied by rapid cell cycle progression and dynamic changes in nuclear organization, such as nuclear size and chromatin constitution. In this study, we focused on the early development of the sea urchin Hemicentrotus pulcherrimus and performed three-dimensional fluorescence in situ hybridization of gene loci encoding early histones (one of the types of histone in sea urchin). There are two non-allelic early histone gene loci per sea urchin genome. We found that during the morula stage, when the early histone gene expression levels are at their maximum, interchromosomal interactions were often formed between the early histone gene loci on separate chromosomes and that the gene loci were directed to locate to more interior positions. Furthermore, these interactions were associated with the active transcription of the early histone genes. Thus, such dynamic interchromosomal interactions may contribute to the efficient synthesis of early histone mRNA during the morula stage of sea urchin development. © 2017. Published by The Company of Biologists Ltd.

Internal tides in the Solomon Sea

NASA Astrophysics Data System (ADS)

Lionel, Tchilibou Michel; Gourdeau, Lionel; Djath, Bugshin; Lyard, Florent; Allain, Damien; Koch Larrouy, Ariane; Yoga Nogroho, Dwi; Morrow, Rosemary

2017-04-01

In the south west Pacific, the Solomon Sea lies on the pathway of the Low Latitudes Western Boundary Currents (LLWBCs) that connect the subtropics to the equator. The Solomon Sea have a particular interest in a climatic context, since they are a critical pathway for ENSO and its low frequency modulation. The western Pacific is a place of energetic internal tides generated over its complex bottom topographic features. In the Indonesian Archipelago, they are particularly active in defining the properties of the waters that move from the Pacific to the Indian Ocean. The salinity maximum at the thermocline level, which is characteristic of the South Pacific Tropical Waters (SPTW) flowing within the LLWBCs and feeding the Equatorial UnderCurrent, is largely eroded within the Solomon Sea. Different mechanisms could explain such salt erosion including current/bathymetry interactions, internal tides, and eddy activity. The motivation of this study is to investigate the potential role of internal tides for such water mass transformation. Results from a 1/36° resolution regional model including explicit tides are presented. As a first step, the generation and propagation of internal tides in the Solomon Sea are determined, and the conversion rate from barotropic to baroclinic energy is estimated.

Maximal exercise and muscle oxygen extraction in acclimatizing lowlanders and high altitude natives

PubMed Central

Lundby, Carsten; Sander, Mikael; van Hall, Gerrit; Saltin, Bengt; Calbet, José A L

2006-01-01

The tight relation between arterial oxygen content and maximum oxygen uptake () within a given person at sea level is diminished with altitude acclimatization. An explanation often suggested for this mismatch is impairment of the muscle O2 extraction capacity with chronic hypoxia, and is the focus of the present study. We have studied six lowlanders during maximal exercise at sea level (SL) and with acute (AH) exposure to 4100 m altitude, and again after 2 (W2) and 8 weeks (W8) of altitude sojourn, where also eight high altitude native (Nat) Aymaras were studied. Fractional arterial muscle O2 extraction at maximal exercise was 90.0 ± 1.0% in the Danish lowlanders at sea level, and remained close to this value in all situations. In contrast to this, fractional arterial O2 extraction was 83.2 ± 2.8% in the high altitude natives, and did not change with the induction of normoxia. The capillary oxygen conductance of the lower extremity, a measure of oxygen diffusing capacity, was decreased in the Danish lowlanders after 8 weeks of acclimatization, but was still higher than the value obtained from the high altitude natives. The values were (in ml min−1 mmHg−1) 55.2 ± 3.7 (SL), 48.0 ± 1.7 (W2), 37.8 ± 0.4 (W8) and 27.7 ± 1.5 (Nat). However, when correcting oxygen conductance for the observed reduction in maximal leg blood flow with acclimatization the effect diminished. When calculating a hypothetical leg at altitude using either the leg blood flow or the O2 conductance values obtained at sea level, the former values were almost completely restored to sea level values. This would suggest that the major determinant for not to increase with acclimatization is the observed reduction in maximal leg blood flow and O2 conductance. PMID:16581864

Aeroacoustic Analysis of Fan Noise Reduction With Increased Bypass Nozzle Area

NASA Technical Reports Server (NTRS)

Woodward, Richard P.; Hughes, Christopher E.; Podboy, Gary G.

2005-01-01

An advanced model turbofan was tested in the NASA Glenn 9-by 15-Foot Low Speed Wind Tunnel (9x15 LSWT) to explore far field acoustic effects of increased bypass nozzle area. This fan stage test was part of the NASA Glenn Fan Broadband Source Diagnostic Test, second entry (SDT2) which acquired aeroacoustic results over a range of test conditions. The baseline nozzle was sized to produce maximum stage performance at cruise condition. However, the wind tunnel testing is conducted near sea level condition. Therefore, in order to simulate and obtain performance at other operating conditions, two additional nozzles were designed and tested one with +5 percent increase in weight flow (+5.4 percent increase in nozzle area compared with the baseline nozzle), sized to simulate the performance at the stage design point (takeoff) condition, and the other with a +7.5 percent increase in weight flow (+10.9 percent increase in nozzle area) sized for maximum weight flow with a fixed nozzle at sea level condition. Measured acoustic benefits with increased nozzle area were very encouraging, showing overall sound power level (OAPWL) reductions of 2 or more dB while the stage thrust actually increased by 2 to 3 percent except for the most open nozzle at takeoff rotor speed where stage performance decreased. Effective perceived noise levels for a 1500 ft engine flyover and 3.35 scale factor showed a similar noise reduction of 2 or more EPNdB. Noise reductions, principally in the level of broadband noise, were observed everywhere in the far field. Laser Doppler Velocimetry measurements taken downstream of the rotor showed that the total turbulent velocity decreased with increasing nozzle flow, which may explain the reduced rotor broadband noise levels.

The competing impacts of climate change and nutrient reductions on dissolved oxygen in Chesapeake Bay

NASA Astrophysics Data System (ADS)

Irby, Isaac D.; Friedrichs, Marjorie A. M.; Da, Fei; Hinson, Kyle E.

2018-05-01

The Chesapeake Bay region is projected to experience changes in temperature, sea level, and precipitation as a result of climate change. This research uses an estuarine-watershed hydrodynamic-biogeochemical modeling system along with projected mid-21st-century changes in temperature, freshwater flow, and sea level rise to explore the impact climate change may have on future Chesapeake Bay dissolved-oxygen (DO) concentrations and the potential success of nutrient reductions in attaining mandated estuarine water quality improvements. Results indicate that warming bay waters will decrease oxygen solubility year-round, while also increasing oxygen utilization via respiration and remineralization, primarily impacting bottom oxygen in the spring. Rising sea level will increase estuarine circulation, reducing residence time in bottom waters and increasing stratification. As a result, oxygen concentrations in bottom waters are projected to increase, while oxygen concentrations at mid-depths (3 < DO < 5 mg L-1) will typically decrease. Changes in precipitation are projected to deliver higher winter and spring freshwater flow and nutrient loads, fueling increased primary production. Together, these multiple climate impacts will lower DO throughout the Chesapeake Bay and negatively impact progress towards meeting water quality standards associated with the Chesapeake Bay Total Maximum Daily Load. However, this research also shows that the potential impacts of climate change will be significantly smaller than improvements in DO expected in response to the required nutrient reductions, especially at the anoxic and hypoxic levels. Overall, increased temperature exhibits the strongest control on the change in future DO concentrations, primarily due to decreased solubility, while sea level rise is expected to exert a small positive impact and increased winter river flow is anticipated to exert a small negative impact.

Correcting for initial Th in speleothems to obtain the age of calcite nucleation after a growth hiatus

NASA Astrophysics Data System (ADS)

Richards, D. A.; Nita, D. C.; Moseley, G. E.; Hoffmann, D. L.; Standish, C. D.; Smart, P. L.; Edwards, R.

2013-12-01

In addition to the many U-Th dated speleothem records (δ18O δ13C, trace elements) of past environmental change based on continuous phases of calcite growth, discontinuous records also provide important constraints for a wide range of past states of the Earth system, including sea levels, permafrost extent, regional aridity and local cave flooding. Chronological information about human activity or faunal evolution can also be obtained where calcite can be seen to overlie cave art or mammalian bones, for example. Among the important considerations when determining the U-Th age of calcite that nucleates on an exposed surface are (1) initial 230Th/232Th, which can be elevated and variable in some settings, and (2) growth rate and sub-sample density, where extrapolation is required. By way of example, we present sea level data based on U-Th ages of vadose speleothems (i.e. formed above the water table and distinct from 'phreatic' examples) from caves of the circum-Caribbean , where calcite growth was interrupted by rising sea levels and then reinitiated after regression. These estimates demand large corrections and derived sea level constraints are compared with alternative data from coral reef terraces, phreatic overgrowths on speleothems or indirect, proxy evidence from oxygen isotopes to constrain rates of ice volume growth. Flowstones from the Bahamas provide useful sea level constraints because they present the longest and most continuous records in such settings (a function of preservation potential in addition to hydrological routing) and also earliest growth post-emergence after sea level fall. We revisit estimates for sea level regression at the end of MIS 5 at ~ 80 ka (Richards et al, 1994; Lundberg and Ford, 1994) and make corrections for non-Bulk Earth initial Th contamination (230Th/232Th activity ratio > 10), based on isochron analysis of alternative stalagmites from the same settings and recent high resolution analysis. We also present new U-Th ages for contiguous layers sub-sampled from the first 2-3 mm of flowstone growth after the MIS 5 hiatus, using a sub-sample milling strategy that matches spatial resolution with maximum achievable precision (ThermoFinnigan Neptune MC-ICPMS methodology; 20-30 mg calcite, U = ~ 300 ng.g-1, 2σ age uncertainty is × 600 a at ~80 ka). Isochron methods are used to estimate the range of initial 230Th/232Th ratio and are compared with elevated values obtained from stalagmites from the same cave (Beck et al, 2001; Hoffmann et al, 2010). A similar strategy is presented for a stalagmite with much faster axial growth data, and the data are combined with additional sea level information from the same region to estimate the rate and uncertainty of sea level regression at the MIS stage 5/4 boundary. Elevated initial 230Th/232Th values have also been observed in a stalagmite from 6 m below present sea level in a cenote from the Yucatan, Mexico, where 5 phases of calcite between 10 and 5.5 ka are separated by serpulid worm tubes formed during periods of submergence. The transition between each phase provides constraints on age and elevation of relative sea level, but the former is hampered by the uncertainty of the high initial 230Th/232Th correction. We consider the possible sources of elevated Th ratios: hydrogenous, colloidal and carbonate or other detrital components.

Effects of the earthquake of March 27, 1964, on the communities of Kodiak and nearby islands: Chapter F in The Alaska earthquake, March 27, 1964: effects on communities

USGS Publications Warehouse

Kachadoorian, Reuben; Plafker, George

1967-01-01

The great earthquake (Richter magnitude of 8.4–8.5) that struck south-central Alaska at 5:36 p.m., Alaska standard time, on March 27, 1964 (03:36, March 28, Greenwich mean time), was felt in every community on Kodiak Island and the nearby islands. It was the most severe earthquake to strike this part of Alaska in modern time, and took the lives of 18 persons in the area by drowning; this includes two in Kodiak and three at Kaguyak. Property damage and loss of income to the communities is estimated at more than $45 million. The largest community, Kodiak, had the greatest loss from the earthquake. Damage was caused chiefly by 5.6 feet of tectonic subsidence and a train of 10 seismic sea waves that inundated the low-lying areas of the town. The seismic sea waves destroyed all but one of the docking facilities and more than 215 structures; many other structures were severely damaged. The waves struck the town during the evening hours of March 27 and early morning hours of March 28. They moved from the southwest and northeast: and reached their maximum height of 20–30 feet above mean lower low water at Shahafka Cove between 11:00 and 11:45 p.m., March 27. The violently destructive seismic sea waves not only severely damaged homes, shops, and naval-station structures but also temporarily crippled the fishing industry in Kodiak by destroying the processing plants and most of the fishing vessels. The waves scoured out 10 feet of sediments in the channel between Kodiak Island and Near Island and exposed bedrock. This bedrock presented a major post-earthquake construction problem because no sediments remained into which piles could be driven for foundations of waterfront facilities. Because of tectonic subsidence, high tides now flood Mission and Potatopatch Lakes which, before the earthquake, had not been subject to tidal action. The subsidence also accelerated erosion of the unconsolidated sediments along the shoreline in the city of Kodiak. Seismic shaking lasted 4½–5½ minutes at Kodiak and had a rolling motion. Inasmuch as most of Kodiak is underlain by bedrock or by only a thin veneer of unconsolidated sediments, very little if any damage occurred from ground motion or seismic shaking. The ground motion, however, did cause a massive short circuit and power failure at Kodiak. The Kodiak Naval Station, 5 miles southwest of Kodiak, was also severely damaged by the earthquake. The station was inundated by at least 10 seismic sea waves which reached a maximum height of 25 feet above post-earthquake mean lower low water between 11:16 and 11:34 p.m. on March 27, 1964. The first seismic sea wave that inundated the station did not do severe damage because it behaved much like a rapid rise of tide, but the subsequent and more violent waves destroyed most of the docking facilities and several other shoreline structures. The waves struck the station from the southwest and from the east. The shoreline structures that were not destroyed required rehabilitation because the 5.6 feet of tectonic subsidence put them under water during the highest tides. Furthermore the subsidence accelerated erosion during high tide of the soft unconsolidated sediments and fill in the low-lying areas of the station. Seismic shaking did little damage to the station housing facility, but it was responsible for compaction of sediments, lateral displacement of a seawall, and the development of fissures in the aircraft parking area. The ground motion was as south-southeast–north-northwest to north-south in direction. An unusual case of radioactive contamination was reported at the naval station. The inundating seismic sea waves entered a building in which radionuclides were stored. The contamination was restricted to the building only, however, and did not spread throughout the station. Afognak was abandoned because of the extensive damage incurred from tectonic subsistence and seismic sea waves. The seismic effects, estimated Mercalli intensity VI-VII, did not directly cause any significant property damage at Afognak Serious long-term damage, however, resulted from tectonic subsidence estimated to be from 3½ to 5½ feet. The subsidence has resulted in rapid erosion of the coast, landward shift and building up of bench berms to the new higher sea levels, and flooding of extensive low-lying areas behind the barrier beaches. Inundation of low-lying parts of the village by a train of seismic sea waves having maximum heights of 10.8 feet above post-earthquake tide level (14.5 ft above post-earthquake mean lower low water) caused losses of about half a million dollars to homes, vehicles, bridges, and personal possessions. Uzinki was damaged by tectonic subsidence and seismic sea waves. No significant damage resulted from the ground motion during the earthquake; the Mercalli intensity was about VI. However, tectonic subsidence, estimated to be 5 feet, caused inundation of a narrow zone along the waterfront. Structures and vessels were damaged as a result of the seismic sea waves that repeatedly flooded the waterfront area after the earthquake. Old Harbor was damaged by seismic shock, subsidence, and seismic sea waves. The tremors, which had a Mercalli intensity estimated at VII-VIII, toppled two concrete-block chimneys, cracked interior walls, and caused minor breakage of personal property in the homes. Regional tectonic subsidence and superficial subsidence of the unconsolidated deposits on which the village is situated apparently caused incursion of salt water into the school well. A quarter of million yards of fill was required to raise the waterfront areas to their pre-earthquake elevations relative to sea level. Seismic sea waves having a maximum runup of about 12 feet above tide level (16 ft above post-earthquake mean lower low water) destroyed 34 of the 35 residences in the village and presumably drowned one man who lived immediately across the strait from Old Harbor. At Kaguyak, seismic sea waves having a maximum runup of about 25 feet above mean lower low water carried away all 10 buildings in the village, took three lives, and damaged an unknown number of fishing vessels. The village site has been abandoned. The communities of Akhiok, Karluk, and Larsen Bay were virtually undamaged by the earthquake tremors, which had estimated Mercalli intensities of VI-VII, but tectonic subsidence of about 2–2½ feet at Larsen Bay made it necessary to raise the cannery dock level at an estimated cost of $80,000.

Holocene Relative Sea-Level Changes from Near-, Intermediate-, and Far-Field Locations

NASA Astrophysics Data System (ADS)

Walker, J. S.; Khan, N.; Shaw, T.; Ashe, E.; Vacchi, M.; Peltier, W. R.; Kopp, R. E.; Horton, B.

2015-12-01

Holocene relative sea-level (RSL) records exhibit spatial and temporal variability that arises mainly from the interaction of eustatic (land ice volume and thermal expansion) and isostatic (glacio- and hydro-) factors. We fit RSL histories from near-, intermediate-, and far-field locations with noisy-input Gaussian process models to assess rates of RSL change from selected study areas. Records from near-field regions (e.g., Antarctica, Greenland, Canada, Sweden, and Scotland) reveal a complex pattern of RSL fall from a maximum marine limit due to the net effect of eustatic sea-level rise and glacial-isostatic uplift with rates of RSL fall as great as -69 ± 9 m/ka. Intermediate-field regions (e.g., mid-Atlantic and Pacific coasts of the United States, Netherlands, Southern France, St. Croix) display variable rates of RSL rise from the cumulative effect of isostatic and eustatic factors. Fast rates of RSL rise (up to 10 ± 1 m/ka) are found in the early Holocene in regions near the center of forebulge collapse. Far-field RSL records exhibit a mid-Holocene highstand, the timing (between 8 and 4 ka) and magnitude (between <1 and 6 m) of which varies across South America, Africa, Asia and Australia regions.

Pennsylvanian tropical rain forests responded to glacial-interglacial rhythms

NASA Astrophysics Data System (ADS)

Falcon-Lang, Howard J.

2004-08-01

Pennsylvanian tropical rain forests flourished during an icehouse climate mode. Although it is well established that Milankovitch-band glacial-interglacial rhythms caused marked synchronous changes in Pennsylvanian tropical climate and sea level, little is known of vegetation response to orbital forcing. This knowledge gap has now been addressed through sequence- stratigraphic analysis of megafloral and palynofloral assemblages within the Westphalian D Cantabrian Sydney Mines Formation of eastern Canada. This succession was deposited in a low- accommodation setting where sequences can be attributed confidently to glacio-eustasy. Results show that long-lived, low-diversity peat mires dominated by lycopsids were initiated during deglaciation events, but were mostly drowned by rising sea level at maximum interglacial conditions. Only upland coniferopsid forests survived flooding without significant disturbance. Mid- to late interglacial phases witnessed delta-plain progradation and establishment of high-diversity, mineral-substrate rain forests containing lycopsids, sphenopsids, pteridosperms, cordaites, and tree ferns. Renewed glaciation resulted in sea-level fall, paleovalley incision, and the onset of climatic aridity. Glacial vegetation was dominated by cordaites, pteridosperms, and tree ferns; hydrophilic lycopsids and sphenopsids survived in paleovalley refugia. Findings clearly demonstrate the dynamic nature of Pennsylvanian tropical ecosystems and are timely given current debates about the impact of Quaternary glacial-interglacial rhythms on the biogeography of tropical rain forest.

The effect of sediment loading in Fennoscandia and the Barents Sea during the last glacial cycle on glacial isostatic adjustment observations

NASA Astrophysics Data System (ADS)

van der Wal, Wouter; IJpelaar, Thijs

2017-09-01

Models for glacial isostatic adjustment (GIA) routinely include the effects of meltwater redistribution and changes in topography and coastlines. Since the sediment transport related to the dynamics of ice sheets may be comparable to that of sea level rise in terms of surface pressure, the loading effect of sediment deposition could cause measurable ongoing viscous readjustment. Here, we study the loading effect of glacially induced sediment redistribution (GISR) related to the Weichselian ice sheet in Fennoscandia and the Barents Sea. The surface loading effect and its effect on the gravitational potential is modeled by including changes in sediment thickness in the sea level equation following the method of Dalca et al. (2013). Sediment displacement estimates are estimated in two different ways: (i) from a compilation of studies on local features (trough mouth fans, large-scale failures, and basin flux) and (ii) from output of a coupled ice-sediment model. To account for uncertainty in Earth's rheology, three viscosity profiles are used. It is found that sediment transport can lead to changes in relative sea level of up to 2 m in the last 6000 years and larger effects occurring earlier in the deglaciation. This magnitude is below the error level of most of the relative sea level data because those data are sparse and errors increase with length of time before present. The effect on present-day uplift rates reaches a few tenths of millimeters per year in large parts of Norway and Sweden, which is around the measurement error of long-term GNSS (global navigation satellite system) monitoring networks. The maximum effect on present-day gravity rates as measured by the GRACE (Gravity Recovery and Climate Experiment) satellite mission is up to tenths of microgal per year, which is larger than the measurement error but below other error sources. Since GISR causes systematic uplift in most of mainland Scandinavia, including GISR in GIA models would improve the interpretation of GNSS and GRACE observations there.

Enhanced UV exposure on a ski-field compared with exposures at sea level.

PubMed

Allen, Martin; McKenzie, Richard

2005-05-01

Personal erythemal UV monitoring badges, which were developed to monitor the UV exposure of school children, were used to measure UV exposures received by one of the authors (MA) at the Mt Hutt ski-field, in New Zealand. These were then compared with measurements taken at the same times from a nearby sea level site in Christchurch city. The badges were designed to give instantaneous readings of erythemally-weighted (i.e., "sun burning") UV radiation and were cross-calibrated against meteorological grade UV instruments maintained by the National Institute of Water & Atmospheric Research (NIWA). All skiing and calibration days were clear and almost exclusively cloud free. It was found that the UV maxima for horizontal surfaces at the ski-field (altitude approximately 2 km) were 20-30% greater than at the low altitude site. Larger differences between the sites were observed when the sensor was oriented perpendicular to the sun. The personal doses of UV received by a sensor on the skier's lapel during two days of skiing activity were less than those received by a stationary detector on a horizontal surface near sea level. The exposures depended strongly on the time of year, and in mid-October the maximum UV intensity on the ski-field was 60% greater than in mid-September. The UV exposure levels experienced during skiing were smaller than the summer maxima at low altitudes.

Retrieval of the thickness of undeformed sea ice from C-band compact polarimetric SAR images

NASA Astrophysics Data System (ADS)

Zhang, X.; Dierking, W.; Zhang, J.; Meng, J. M.; Lang, H. T.

2015-10-01

In this paper we introduce a parameter for the retrieval of the thickness of undeformed first-year sea ice that is specifically adapted to compact polarimetric SAR images. The parameter is denoted as "CP-Ratio". In model simulations we investigated the sensitivity of CP-Ratio to the dielectric constant, thickness, surface roughness, and incidence angle. From the results of the simulations we deduced optimal conditions for the thickness retrieval. On the basis of C-band CTLR SAR data, which were generated from Radarsat-2 quad-polarization images acquired jointly with helicopter-borne sea ice thickness measurements in the region of the Sea of Labrador, we tested empirical equations for thickness retrieval. An exponential fit between CP-Ratio and ice thickness provides the most reliable results. Based on a validation using other compact polarimetric SAR images from the same region we found a root mean square (rms) error of 8 cm and a maximum correlation coefficient of 0.92 for the retrieval procedure when applying it on level ice of 0.9 m mean thickness.

Assembly and Initial Analysis of a Database of the Characteristics of Fixed-Wing Unmanned Aircraft Systems

DTIC Science & Technology

2014-11-01

sea level (evaluated for turbojet- and turbofan -powered UAVs and targets only) R range (km) ferryR ferry range (km) radiusR mission radius (km...operating airspeed for manned turbofan -powered aircraft, and a power law for birds derived by Alerstam et al. [22...UAVs in the Database; and ratio of operating to maximum airspeed for turbojet- or turbofan -powered UAVs with mmax > 103 kg

Understanding the Microphysical Properties of Developing Cloud Clusters during TCS-08

DTIC Science & Technology

2011-09-30

resolution (1.67-km) sensitivity simulations have been performed using Typhoon Mawar (2005) from the western North Pacific to demonstrate considerable...cloud-resolving) scheme is used in the model. Initial calculations of some basic cloud properties from infrared imagery for Typhoon Mawar indicate that...Figure 4: Intensity traces of simulated Typhoon Mawar (2005) showing sea-level pressure on the left axis and maximum wind speed on the right axis

SEA Semester Undergraduates Research the Ocean's Role in Climate Systems in the Pacific Ocean

NASA Astrophysics Data System (ADS)

Meyer, A. W.; Becker, M. K.; Grabb, K. C.

2014-12-01

Sea Education Association (SEA)'s fully accredited Oceans & Climate SEA Semester program provides upper-level science undergraduates a unique opportunity to explore the ocean's role in the global climate system as they conduct real-world oceanographic research and gain first-hand understanding of and appreciation for the collaborative nature of the scientific research process. Oceans & Climate is an interdisciplinary science and policy semester in which students also explore public policy perspectives to learn how scientific knowledge is used in making climate-related policy. Working first at SEA's shore campus, students collaborate with SEA faculty and other researchers in the local Woods Hole scientific community to design and develop an original research project to be completed at sea. Students then participate as full, working members of the scientific team and sailing crew aboard the 134-foot brigantine SSV Robert C. Seamans; they conduct extensive oceanographic sampling, manage shipboard operations, and complete and present the independent research project they designed onshore. Oceans & Climate SEA Semester Cruise S-250 sailed from San Diego to Tahiti on a 7-week, >4000nm voyage last fall (November-December 2013). This remote open-ocean cruise track traversed subtropical and equatorial regions of the Pacific particularly well suited for a diverse range of climate-focused studies. Furthermore, as SEA has regularly collected scientific data along similar Pacific cruise tracks for more than a decade, students often undertake projects that require time-series analyses. 18 undergraduates from 15 different colleges and universities participated in the S-250 program. Two examples of the many projects completed by S-250 students include a study of the possible relationship between tropical cyclone intensification, driven by warm sea surface temperatures, and the presence of barrier layers; and a study of nutrient cycling in the eastern Pacific, focusing on primary nitrite maximum changes in various oceanographic regions with differing levels of stratification and accompanying localization of microbial communities. These studies, as well as additional scientific and policy projects conducted by other Oceans & Climate students, will be highlighted in this poster presentation.

Sequence stratigraphy of the Monterey Formation, Santa Barbara County: Integration of physical, chemical, and biofacies data from outcrop and subsurface

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

Bohacs, K.M.

1991-02-01

Deep basinal rocks of the Monterey Formation can be allocated to different depositional environments based on an integration of bedding, stacking patterns of facies, lithology, biofacies, and inorganic and organic chemistry. These rocks show evidence of systematic changes in depositional environments that can be related to eustatic sea level changes and basin evolution. Even deep-basinal environments are affected by changing sea level through changes in circulation patterns and intensities, nutrient budgets and dispersal patterns, and location and intensity of the oceanic oxygen minimum. The sequence-stratigraphic framework was constructed based on the physical expression of the outcrop strata and confirmed bymore » typing the outcrop sections to an integrated will-log/seismic grid through outcrop gamma-ray spectral profiles. Interpretation of a sequence boundary was based on increased proportions of hemipelagic facies and evidence of increased bottom-energy levels above the boundary, and local erosion and relief on the surface. The proportion of shallower water and reworked dinoflagellates increased to a local maximum above the boundary. Downlap surfaces exhibited increased proportions of pelagic facies around the surface, a secular change in the dominant lithology across the surface, evidence of decreased bottom-energy levels and terrigenous sedimentation rates, and little or not significant erosion on the surface. The proportion of deeper water dinoflagellates increased to a local maximum at or near the downlap surface; there was no evidence of reworked individuals. The detailed sequence-stratigraphic framework makes it possible to tie rock properties to genetic processes for construction of predictive models.« less

A Quantitative Ecological Risk Assessment of the Toxicological Risks from Exxon Valdez Subsurface Oil Residues to Sea Otters at Northern Knight Island, Prince William Sound, Alaska

PubMed Central

Harwell, Mark A.; Gentile, John H.; Johnson, Charles B.; Garshelis, David L.; Parker, Keith R.

2010-01-01

A comprehensive, quantitative risk assessment is presented of the toxicological risks from buried Exxon Valdez subsurface oil residues (SSOR) to a subpopulation of sea otters (Enhydra lutris) at Northern Knight Island (NKI) in Prince William Sound, Alaska, as it has been asserted that this subpopulation of sea otters may be experiencing adverse effects from the SSOR. The central questions in this study are: could the risk to NKI sea otters from exposure to polycyclic aromatic hydrocarbons (PAHs) in SSOR, as characterized in 2001–2003, result in individual health effects, and, if so, could that exposure cause subpopulation-level effects? We follow the U.S. Environmental Protection Agency (USEPA) risk paradigm by: (a) identifying potential routes of exposure to PAHs from SSOR; (b) developing a quantitative simulation model of exposures using the best available scientific information; (c) developing scenarios based on calculated probabilities of sea otter exposures to SSOR; (d) simulating exposures for 500,000 modeled sea otters and extracting the 99.9% quantile most highly exposed individuals; and (e) comparing projected exposures to chronic toxicity reference values. Results indicate that, even under conservative assumptions in the model, maximum-exposed sea otters would not receive a dose of PAHs sufficient to cause any health effects; consequently, no plausible toxicological risk exists from SSOR to the sea otter subpopulation at NKI. PMID:20862194

Geoid determination in the coastal areas of the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Song, HongZhi

Coastal areas of the Gulf of Mexico are important for many reasons. This part of the United States provides vital coastal habitats for many marine species; the area has seen-ever increasing human settlement along the coast, ever increasing infrastructure for marine transportation of the nation's imports and exports through Gulf ports, and ever increasing recreational users of coastal resources. These important uses associated with the Gulf coast are subject to dynamic environmental and physical changes including: coastal erosion (Gulf-wide rates of 25 square miles per year), tropical storm surges, coastal subsidence, and global sea level rise. Coastal land subsidence is a major component of relative sea level rise along the coast of the Gulf of Mexico. These dynamic coastal changes should be evident in changes to the geoid along the coast. The geoid is the equipotential gravity surface of the earth, which the best fits the global mean sea level. The geoid is not only been seen as the most natural shape of the Earth, but also it serves as the reference surface for most of the height systems. By using satellites (GRACE mission) scientists have been able to measure the large scale geoid for the Earth. A small scale geoid model is required to monitor local events such as flooding, for example, flooding created by storm surges from hurricanes such as Katrina (2005), Rita (2005), and Ike (2008). The overall purpose of this study is to evaluate the accuracy of the local coastal geoid. The more precise geoid will enable to improve coastal flooding predictions, and will enable more cost effective and accurate measurement of coastal topography using global navigation satellite systems (GNSS). The main objective of this study is to devise mathematical models and computational methods to achieve the best possible precision for evaluation of the geoid in the coastal areas of the Gulf of Mexico. More specifically, the numerical objectives of this study are 1) to obtain a continuous map of gravity anomalies and a continuous map of gravity by using spatial interpolation methods and to evaluate errors; 2) to solve the Laplace boundary value problem and evaluate errors; 3) to evaluate precision of the local geoid by using geospatial statistical tools and numerical techniques. This dissertation investigates modeling of the geoid, especially the gravimetric equipotential surface that approximates mean sea level, in the coastal areas of the Gulf of Mexico as well as errors in the geoid determination. The document begins with Chapter 1 which introduces the study of this dissertation. Different models of kriging are used to determine the precision of the geoid based on the free-air gravity anomalies data supplied by United States Naval Research Laboratory and the airborne gravity data provided by the U.S. National Geodetic Survey, which can be found in Chapters 2 and 3. Research in Chapters 2 shows that more precise evaluation of errors in gravity anomalies can be achieved by using different models of kriging. Results from Chapters 2 and 3 show that ordinary kriging with the stable semivariogram model provide better predictions. Research results from Chapter 3 provide estimation of maximum possible errors in the calculation of the geoid undulation. The dissertation also investigates behavior of gravity equipotential surfaces around coastal lines and its impact on the geoid evaluation. Chapters 4 and 5 are about evaluation of errors in the Dirichlet problem for calculation of gravity potential with uncertain boundary and boundary values has been achieved by solving the Laplace equation by means of separation of variables. Research has provided a theoretical model in Chapter 4 to estimate very small changes in gravimetric potential relative to the coast. Maximum possible error in the solution of Direchlet problem is determined in Chapter 5. Maximum possible error depends on the errors of boundary values and the precision of the boundary itself. Chapter 6 describes a novel approach to sea level rise modeling. Factor analysis is used to analyze local and global sea level rise and relationships between changing sea levels, currents, and the shape of the Earth. Results of factor analysis from Chapter 6 show that the elevation of sea level relates to the geoid and ocean circulation. Chapter 7 describes the relationship between the geoid and wetlands modeling. Research in Chapter 7 shows that the predicted continuous elevation map obtained through the ordinary stable kriging was sufficiently precise and fairly reliable. Chapter 7 is an exploratory chapter, and the ideas of this chapter will help the future research.

Seasonal variations of sulfate, carbonaceous species (black carbon and polycyclic aromatic hydrocarbons), and trace elements in fine atmospheric aerosols collected at subtropical islands in the East China Sea

NASA Astrophysics Data System (ADS)

Kaneyasu, Naoki; Takada, Hideshige

2004-03-01

In order to characterize the outflow of pollution derived aerosols from the Asian Pacific rim to the North Pacific Ocean, seasonal variations of fine aerosol components (aerodynamic diameter <2 μm) were collected at two islands (Amami Island and Miyako Island) that surround the East China Sea. Monthly averaged concentrations of non-sea-salt SO42- (nss.SO42-) and black carbon (BC) at Amami and Miyako showed relatively high values in winter to spring and low values in summer. The observed seasonal variation is basically determined by the northwesterly monsoon in winter to spring and southeasterly wind from the stationary North Pacific anticyclone in summer. The minimum concentration levels of nss.SO42- and BC in summer were almost 2-3 times that of the North Pacific background level. Trace metals in aerosols showed similar seasonal variations observed for nss.SO42- and BC. The concentrations of nss.SO42- and Sb were highly correlated; this is in contradiction with the results at stations established in Pacific Exploratory Mission-West ground monitoring sites. Polycyclic aromatic hydrocarbons (PAHs) also showed a pronounced maximum in winter and/or spring, with maximum concentrations comparable in magnitude to those in spring at Barrow, Alaska. Many of the low molecular weight species of PAHs had high correlation with BC, suggesting that they were either transported independently in a similar way or were transported attached to BC. Furthermore, the relative abundance of some PAH species in the present study and those found in deep-ocean surface sediments sampled in the middle Pacific Ocean are compared and discussed.

Sea-Ice Conditions in the Norwegian, Barents, and White Seas

DTIC Science & Technology

1976-08-01

pack, aided by relatively warm water from the Murman coast current, would reduce the maximum ice thickness predicted by the equation used for...THICKNESS With the aid of the ice growth model in the appendix, it is pos- sible to relate the maximum ice thickness attained during a winter season to a...inserted merely to aid the reader in discerning differences between individual winter seasons. As was the case for the 12-month mean temperatures

Changes and variations in the turning angle of Arctic sea ice

NASA Astrophysics Data System (ADS)

Ukita, J.; Honda, M.; Ishizuka, S.

2012-12-01

The motion of sea ice is under influences of forcing from winds and currents and of sea ice properties. In facing rapidly changing Arctic climate we are interested in whether we observe and quantify changes in sea ice conditions reflected in its velocity field. Theoretical consideration on the freedrift model predicts a change in the sea ice turning angle with respect to the direction of forcing wind in association with thinning sea ice thickness. Possible changes in atmospheric and ocean boundary layer conditions may be reflected in the sea ice turning angle through modification of both atmospheric and oceanic Ekman spirals. With these in mind this study examines statistical properties of the turning angle of the Arctic sea ice and compares them with atmospheric/ice/ocean conditions for the period of 1979-2010 on the basis of IABP buoy data. Preliminary results indicate that over this period the turning angle has varying trends depending on different seasons. We found weakly significant (>90% level) changes in the turning angle from August to October with the maximum trend in October. The direction of trends is counter-clockwise with respect to the geostrophic wind direction, which is consistent with the thinning of sea ice. The interannual variability of the turning angle for this peak season of the reduced sea ice cover is not the same as that of the Arctic SIE. However, in recent years the turning angle appears to covary with the surface air temperature, providing supporting evidence for the relationship between the angle and sea ice thickness. In the presentation we will provide results on the relationships between the turning angle and atmospheric and oceanic variables and further discuss their implications.

Holocene Sea-Levels from Greenland to Antarctica: A Pole-to-Pole Transect of Sea Level History

NASA Astrophysics Data System (ADS)

Horton, Benjamin; Peltier, William; Roy, Keven; Ashe, Erica; Shaw, Tim; Engelhart, Simon; Khan, Nicole; Kopp, Robert; Simkins, Lauren; Vacchi, Matteo; Woodroffe, Sarah

2017-04-01

The Holocene is the most recent period during which natural temperature variability predominates and, therefore, provides an important paleo perspective for understanding the climate:sea-level relationship prior to anthropogenic modification of the climate system. But our understanding of Holocene sea level is limited by a lack of a standard protocol that incorporates full consideration of vertical and temporal uncertainty for each sea-level index point. We have compiled a Holocene RSL database of 3000 validated sea-level index points from Greenland, North American Atlantic coast, Caribbean, South American Atlantic coast and Antarctica. The databases were collated using a formalized and consistent methodology to facilitate the development and comparison of regional RSL records. The database also includes information relevant to sediment compaction, and modelling of both modern-day and paleotidal ranges. We develop a spatio-temporal empirical hierarchical model to compare regional RSL histories and estimate rates of change. Holocene RSL history from near-field regions (e.g., Antarctica, Greenland and Canada) reveal a complex pattern of RSL fall from a maximum marine limit due to the net effect of eustatic sea-level rise and glacio-isostatic uplift with rates of RSL fall as great as 70 ± 5 m/ka (East Hudson Bay). Intermediate field regions (e.g., North American mid-Atlantic coast) display variable rates of RSL rise from the cumulative effect of eustatic and isostatic factors. Fast rates of RSL rise (up to 10 ± 4m/ka; New Jersey) are found in the early Holocene in regions near the center of forebulge collapse. Far-field RSL records (South American Atlantic coast) exhibit a mid-Holocene highstand, the timing and magnitude of which varies between 8 and 4 ka and <1 and 6 m, respectively. We compare RSL histories with the predictions from two recent models of the Glacial Isostatic Adjustment (GIA) process, namely the ICE-6GC (VM5a) model of Peltier et al. (2015) and the ICE-7G_NA (VM7) model of Roy and Peltier (2017 in press). Although the fit of these models to the wide range of inferred RSL histories along the pole-to-pole transect is very high quality, unexplained signals are identified in several restricted regions upon which work is continuing. It is remarkable that a spherically symmetric model of the internal viscoelastic structure is able to reconcile the wide range of RSL signals observed.

Influence of sea ice on Arctic coasts

NASA Astrophysics Data System (ADS)

Barnhart, K. R.; Kay, J. E.; Overeem, I.; Anderson, R. S.

2017-12-01

Coasts form the dynamic interface between the terrestrial and oceanic systems. In the Arctic, and in much of the world, the coast is a focal point for population, infrastructure, biodiversity, and ecosystem services. A key difference between Arctic and temperate coasts is the presence of sea ice. Changes in sea ice cover can influence the coast because (1) the length of the sea ice-free season controls the time over which nearshore water can interact with the land, and (2) the location of the sea ice edge controls the fetch over which storm winds can interact with open ocean water, which in turn governs nearshore water level and wave field. We first focus on the interaction of sea ice and ice-rich coasts. We combine satellite records of sea ice with a model for wind-driven storm surge and waves to estimate how changes in the sea ice-free season have impacted the nearshore hydrodynamic environment along Alaska's Beaufort Sea Coast for the period 1979-2012. This region has experienced some of the greatest changes in both sea ice cover and coastal erosion rates in the Arctic: the median length of the open-water season has expanded by 90 percent, while coastal erosion rates have more than doubled from 8.7 to 19 m yr-1. At Drew Point, NW winds increase shoreline water levels that control the incision of a submarine notch, the rate-limiting step of coastal retreat. The maximum water-level setup at Drew Point has increased consistently with increasing fetch. We extend our analysis to the entire Arctic using both satellite-based observations and global coupled climate model output from the Community Earth System Model Large Ensemble (CESM-LE) project. This 30-member ensemble employs a 1-degree version of the CESM-CAM5 historical forcing for the period 1920-2005, and RCP 8.5 forcing from 2005-2100. A control model run with constant pre-industrial (1850) forcing characterizes internal variability in a constant climate. Finally, we compare observations and model results to identify locations of both observed and expected rapid sea ice change. Based on satellite observations, the median length of the 2012 open-water season expanded by between 1.5 and 3-fold relative to 1979 over the Arctic Sea region. This results in open water during the stormy Arctic fall, with implications for not only coastal processes but for amplification of warming on land.

Fast Response of the Tropics to an Abrupt Loss of Arctic Sea Ice via Ocean Dynamics

NASA Astrophysics Data System (ADS)

Wang, Kun; Deser, Clara; Sun, Lantao; Tomas, Robert A.

2018-05-01

The role of ocean dynamics in the transient adjustment of the coupled climate system to an abrupt loss of Arctic sea ice is investigated using experiments with Community Climate System Model version 4 in two configurations: a thermodynamic slab mixed layer ocean and a full-depth ocean that includes both dynamics and thermodynamics. Ocean dynamics produce a distinct sea surface temperature warming maximum in the eastern equatorial Pacific, accompanied by an equatorward intensification of the Intertropical Convergence Zone and Hadley Circulation. These tropical responses are established within 25 years of ice loss and contrast markedly with the quasi-steady antisymmetric coupled response in the slab-ocean configuration. A heat budget analysis reveals the importance of anomalous vertical advection tied to a monotonic temperature increase below 200 m for the equatorial sea surface temperature warming maximum in the fully coupled model. Ocean dynamics also rapidly modify the midlatitude atmospheric response to sea ice loss.

Ocean Profile Measurements During the Seasonal Ice Zone Reconnaissance Surveys Ocean Profiles

DTIC Science & Technology

2017-01-01

repeated ocean, ice, and atmospheric measurements across the Beaufort-Chukchi sea seasonal sea ice zone (SIZ) utilizing US Coast Guard Arctic Domain...contributing to the rapid decline in summer ice extent that has occurred in recent years. The SIZ is the region between maximum winter sea ice extent and...minimum summer sea ice extent. As such, it contains the full range of positions of the marginal ice zone (MIZ) where sea ice interacts with open water

Millennial-scale northern Hemisphere Atlantic-Pacific climate teleconnections in the earliest Middle Pleistocene.

PubMed

Hyodo, Masayuki; Bradák, Balázs; Okada, Makoto; Katoh, Shigehiro; Kitaba, Ikuko; Dettman, David L; Hayashi, Hiroki; Kumazawa, Koyo; Hirose, Kotaro; Kazaoka, Osamu; Shikoku, Kizuku; Kitamura, Akihisa

2017-08-30

Suborbital-scale climate variations, possibly caused by solar activity, are observed in the Holocene and last-glacial climates. Recently published bicentennial-resolution paleoceanic environmental records reveal millennial-scale high-amplitude oscillations postdating the last geomagnetic reversal in the Marine Isotope Stage (MIS) 19 interglacial. These oscillations, together with decoupling of post-reversal warming from maximum sea-level highstand in mid-latitudes, are key features for understanding the climate system of MIS 19 and the following Middle Pleistocene. It is unclear whether the oscillations are synchronous, or have the same driver as Holocene cycles. Here we present a high resolution record of western North Pacific submarine anoxia and sea surface bioproductivity from the Chiba Section, central Japan. The record reveals many oxic events in MIS 19, coincident with cold intervals, or with combined cold and sea-level fall events. This allows detailed correlations with paleoceanic records from the mid-latitude North Atlantic and Osaka Bay, southwest Japan. We find that the millennial-scale oscillations are synchronous between East and West hemispheres. In addition, during the two warmest intervals, bioproductivity follows the same pattern of change modulated by bicentennial cycles that are possibly related to solar activity.

Wave Transformation over a Fringing Coral Reef and the Importance of Low-Frequency Waves and Offshore Water Levels to Runup and Island Overtopping

NASA Astrophysics Data System (ADS)

Cheriton, O. M.; Storlazzi, C. D.; Rosenberger, K. J.

2016-02-01

Low-lying, reef-fringed islands are susceptible to sea-level rise and often subjected to overwash and flooding during large wave events. To quantify wave dynamics and wave-driven water levels on fringing coral reefs, wave gauges and a current meter were deployed for 5 months across two shore-normal transects on Roi-Namur, an atoll island in the Republic of the Marshall Islands. These observations captured two large wave events that had maximum wave heights greater than 6 m and peak periods of 16 s over the fore reef. The larger event coincided with a peak spring tide, leading to energetic, highly-skewed infragravity (0.04-0.004 Hz) and very low frequency (0.004-0.001 Hz) waves at the shoreline, which reached heights of 1.0 and 0.7 m, respectively. Water surface elevations, combined with wave runup, exceeded 3.7 m at the innermost reef flat adjacent to the toe of the beach, resulting in flooding of inland areas. This overwash occurred during a 3-hr time window that coincided with high tide and maximum low-frequency reef flat wave heights. The relatively low-relief characteristics of this narrow reef flat may further drive shoreline amplification of low-frequency waves due to resonance modes. These results demonstrate how the coupling of high offshore water levels with low-frequency reef flat wave energetics can lead to large impacts along atoll and fringing reef-lined shorelines, such as island overwash. These observations lend support to the hypothesis that predicted higher sea levels will lead to more frequent occurrences of both extreme shoreline runup and island overwash, threatening the sustainability of these islands.

Observations of wave transformation over a fringing coral reef and the importance of low-frequency waves and offshore water levels to runup, overwash, and coastal flooding

NASA Astrophysics Data System (ADS)

Cheriton, Olivia M.; Storlazzi, Curt D.; Rosenberger, Kurt J.

2016-05-01

Many low-lying tropical islands are susceptible to sea level rise and often subjected to overwash and flooding during large wave events. To quantify wave dynamics and wave-driven water levels on fringing coral reefs, a 5 month deployment of wave gauges and a current meter was conducted across two shore-normal transects on Roi-Namur Island in the Republic of the Marshall Islands. These observations captured two large wave events that had waves with maximum heights greater than 6 m with peak periods of 16 s over the fore reef. The larger event coincided with a peak spring tide, leading to energetic, highly skewed infragravity (0.04-0.004 Hz) and very low frequency (0.004-0.001 Hz) waves at the shoreline, which reached heights of 1.0 and 0.7 m, respectively. Water surface elevations, combined with wave runup, reached 3.7 m above the reef bed at the innermost reef flat adjacent to the toe of the beach, resulting in flooding of inland areas. This overwash occurred during a 3 h time window that coincided with high tide and maximum low-frequency reef flat wave heights. The relatively low-relief characteristics of this narrow reef flat may further drive shoreline amplification of low-frequency waves due to resonance modes. These results (1) demonstrate how the coupling of high offshore water levels with low-frequency reef flat wave energetics can lead to large impacts along fringing reef-lined shorelines, such as island overwash, and (2) lend support to the hypothesis that predicted higher sea levels will lead to more frequent occurrences of these extreme events, negatively impacting coastal resources and infrastructure.

Observations of wave transformation over a fringing coral reef and the importance of low-frequency waves and offshore water levels to runup, overwash, and coastal flooding

USGS Publications Warehouse

Cheriton, Olivia; Storlazzi, Curt; Rosenberger, Kurt

2016-01-01

Many low-lying tropical islands are susceptible to sea level rise and often subjected to overwash and flooding during large wave events. To quantify wave dynamics and wave-driven water levels on fringing coral reefs, a 5 month deployment of wave gauges and a current meter was conducted across two shore-normal transects on Roi-Namur Island in the Republic of the Marshall Islands. These observations captured two large wave events that had waves with maximum heights greater than 6 m with peak periods of 16 s over the fore reef. The larger event coincided with a peak spring tide, leading to energetic, highly skewed infragravity (0.04–0.004 Hz) and very low frequency (0.004–0.001 Hz) waves at the shoreline, which reached heights of 1.0 and 0.7 m, respectively. Water surface elevations, combined with wave runup, reached 3.7 m above the reef bed at the innermost reef flat adjacent to the toe of the beach, resulting in flooding of inland areas. This overwash occurred during a 3 h time window that coincided with high tide and maximum low-frequency reef flat wave heights. The relatively low-relief characteristics of this narrow reef flat may further drive shoreline amplification of low-frequency waves due to resonance modes. These results (1) demonstrate how the coupling of high offshore water levels with low-frequency reef flat wave energetics can lead to large impacts along fringing reef-lined shorelines, such as island overwash, and (2) lend support to the hypothesis that predicted higher sea levels will lead to more frequent occurrences of these extreme events, negatively impacting coastal resources and infrastructure.

The distribution of deep-sea sponge aggregations in the North Atlantic and implications for their effective spatial management

NASA Astrophysics Data System (ADS)

Howell, Kerry-Louise; Piechaud, Nils; Downie, Anna-Leena; Kenny, Andrew

2016-09-01

Sponge aggregations have been recognised as key component of shallow benthic ecosystems providing several important functional roles including habitat building and nutrient recycling. Within the deep-sea ecosystem, sponge aggregations may be extensive and available evidence suggests they may also play important functional roles, however data on their ecology, extent and distribution in the North Atlantic is lacking, hampering conservation efforts. In this study, we used Maximum Entropy Modelling and presence data for two deep-sea sponge aggregation types, Pheronema carpenteri aggregations and ostur aggregations dominated by geodid sponges, to address the following questions: 1) What environmental factors drive the broad-scale distribution of these selected sponge grounds? 2) What is the predicted distribution of these grounds in the northern North Atlantic, Norwegian and Barents Sea? 3) How are these sponge grounds distributed between Exclusive Economic Zones (EEZs) and High Seas areas? 4) What percentage of these grounds in High Seas areas are protected by the current High Seas MPA network? Our results suggest that silicate concentration, temperature, depth and amount of particulate organic carbon are the most important drivers of sponge distribution. Most of the sponge grounds are located within national EEZs rather than in the High Seas. Coordinated conservation planning between nations with significant areas of sponge grounds such as Iceland, Greenland and Faroes (Denmark), Norway (coastal Norway and Svalbard), Portugal and the UK, should be implemented in order to effectively manage these communities in view of the increasing level of human activity within the deep-sea environment.

Trophodynamics of a deep-sea demersal fish assemblage from the bathyal eastern Ionian Sea (Mediterranean Sea)

NASA Astrophysics Data System (ADS)

Madurell, T.; Cartes, J. E.

2005-11-01

Daily food consumption of the eight dominant demersal fish species of the bathyal eastern Ionian Sea were determined from field data on four seasonal cruises (April 1999, July August 1999, November 1999 and February 2000). Daily ration (DR) estimates ranged from 0.198 to 4.273% WW/WW. Overall, DR estimates were independent of the model used, and they were comparable to the daily consumption of other deep-sea fauna (e.g. fish and crustaceans). Both sharks studied ( Galeus melastomus and Etmopterus spinax) exhibited the highest values of DRs, together with the macrourid Coelorhynchus coelorhynchus in August. Among osteichthyes, DR estimates were related (in a multi-linear regression model) to the nature of their diet (i.e. their trophic level deduced from δ15N isotopic composition, the mean number of prey and trophic diversity). Thus, species feeding at a lower trophic level, ingesting a large number of prey items and with a very diversified diet had higher DR than species from higher trophic level and feeding fewer prey items. By season, the DR of species feeding mainly on mesopelagic prey ( Hoplostethus mediterraneus and Helicolenus dactylopterus) were higher in summer, while DR for benthos/suprabenthos feeders (i.e. C. coelorhynchus and Nezumia sclerorhynchus) were higher in spring. Higher food consumption coincides with maximum food availability, both among mesopelagic feeders (higher availability of euphausiids, Pasiphaea sivado and Sergestes arcticus in summer) and among Macrouridae (higher suprabenthos densities in spring). In a tentative estimate the energy intake deduced from diet (i.e. mean energy value of food ingested) was constant in all seasons for each species studied. Results for the energy intake also indicate higher energy intake in the diet of mesopelagic feeders than in the diet of benthic feeders. Overall results are discussed in relation to the deep-sea ecosystem structure and functioning.

Design and skill assessment of an Operational Forecasting System for currents and sea level variability to the Santos Estuarine System - Brazil

NASA Astrophysics Data System (ADS)

Godoi Rezende Costa, C.; Castro, B. M.; Blumberg, A. F.; Leite, J. R. B., Sr.

2017-12-01

Santos City is subject to an average of 12 storm tide events per year. Such events bring coastal flooding able to threat human life and damage coastal infrastructure. Severe events have forced the interruption of ferry boat services and ship traffic through Santos Harbor, causing great impacts to Santos Port, the largest in South America, activities. Several studies have focused on the hydrodynamics of storm tide events but only a few of those studies have pursued an operational initiative to predict short term (< 3 days) sea level variability. The goals of this study are (i) to describe the design of an operational forecasting system built to predict sea surface elevation and currents in the Santos Estuarine System and (ii) to evaluate model performance in simulating observed sea surface elevation. The Santos Operational Forecasting System (SOFS) hydrodynamic module is based on the Stevens Institute Estuarine and Coastal Ocean Model (sECOM). The fully automated SOFS is designed to provide up to 71 h forecast of sea surface elevations and currents every day. The system automatically collects results from global models to run the SOFS nested into another sECOM based model for the South Brazil Bight (SBB). Global forecasting results used to force both models come from Mercator Ocean, released by Copernicus Marine Service, and from the Brazilian developments on the Regional Atmospheric Modeling System (BRAMS) stablished by the Center for Weather Forecasts and Climate Studies (with Portuguese acronym CPTEC). The complete routines task take about 8 hours of run time to finish. SOFS was able to hindcast a severe storm tide event that took place in Santos on August 21-22, 2016. Comparisons with observed sea level provided skills of 0.92 and maximum root mean square errors of 25 cm. The good agreement with observed data shows the potential of the designed system to predict storm tides and to support both human and assets protection.

Drilling and operational sounds from an oil production island in the ice-covered Beaufort sea.

PubMed

Blackwell, Susanna B; Greene, Charles R; Richardson, W John

2004-11-01

Recordings of sounds underwater and in air, and of iceborne vibrations, were obtained at Northstar Island, an artificial gravel island in the Beaufort Sea near Prudhoe Bay (Alaska). The aim was to document the levels, characteristics, and range dependence of sounds and vibrations produced by drilling and oil production during the winter, when the island was surrounded by shore-fast ice. Drilling produced the highest underwater broadband (10-10,000 Hz) levels (maximum= 124 dB re: 1 microPa at 1 km), and mainly affected 700-1400 Hz frequencies. In contrast, drilling did not increase broadband levels in air or ice relative to levels during other island activities. Production did not increase broadband levels for any of the sensors. In all media, broadband levels decreased by approximately 20 dB/tenfold change in distance. Background levels underwater were reached by 9.4 km during drilling and 3-4 km without. In the air and ice, background levels were reached 5-10 km and 2-10 km from Northstar, respectively, depending on the wind but irrespective of drilling. A comparison of the recorded sounds with harbor and ringed seal audiograms showed that Northstar sounds were probably audible to seals, at least intermittently, out to approximately 1.5 km in water and approximately 5 km in air.

Doppler recordings after diving to depth of 30 meters at high altitude of 4,919 meters (16,138 feet) during the Tilicho Lake Expedition 2007.

PubMed

Kot, J; Sicko, Z; Zyszkowski, M; Brajta, M

2014-01-01

When going to high altitude (higher than 2,400 meters above mean sea level [about 8,200 feet]), human physiology is strongly affected by changes in atmospheric conditions, including decreased ambient pressure and hypobaric hypoxia, which can lead to severe hypoxemia, brain and/or pulmonary edema, negative changes in body and blood composition, as well as disturbances in regional microcirculation. When adding other factors, such as dehydration, physical exercise and exposure to low temperature, it is likely that nitrogen desaturation after diving at such environmental conditions is far from optimal, There are only single reports on diving at high alti-tudes. In 2007 a Polish team of climbers and divers participated in the Tilicho Lake and Peak Expedition to the Himalaya Mountains in Nepal. During this expedition, four divers conducted six dives in the Tilicho Lake at altitude of 4,919 meters above mean sea level equivalent (16,138 feet) to a maximum depth of 15 meters of fresh water (mfw) (equivalent to 28 mfw at sea level by the Cross Correction method) and 30 mfw (equivalent to 57 mfw at sea level "by Cross correction). Decompression debt was calculated using Cross Correction with some additional safety add-ons. Precordial Doppler recordings were taken every 15 minutes until 90 minutes after surfacing. No signs or symptoms of decompression sickness were observed after diving but in one diver, very high bubble grade Doppler signals were recorded. It can be concluded that diving at high altitude should be accompanied by additional safety precautions as well as taking into account personal sensitivity for such conditions.

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.

Mapping Relative Sea Level Influences of the Cape Fear Arch in southern North Carolina

NASA Astrophysics Data System (ADS)

Hawkes, A.; Kemp, A.; Capar, P.

2017-12-01

Long-term relative sea-level (RSL) records are a necessary benchmark by which to gauge present accelerated rates of sea-level rise, future sea-level predictions, and their implications to the coastal zone. The east coast of the United States functions as a significant region of latitudinal RSL variability due to the continuous recovery of land from the deglaciation of the Laurentide Ice Sheet since the Last Glacial Maximum. Differential glacial isostatic adjustment (GIA) along the coastline has caused higher rates of subsidence in areas around the former forbulge maxima near New Jersey and Delaware and lower rates to the north and south of this maxima. However, the coast between southern North Carolina and northern South Carolina is experiencing a slower rate of RSL rise then is seen in reconstructed GIA latitudinal trends along the U.S. east coast. It was thought that this could have been attributed to non-isostatic, long-term tectonic processes causing less GIA subsidence of the lithosphere within the region impacted by uplift from the Cape Fear Arch (CFA), an underlying crystalline basement high. A recent study suggests that RSL rise is slower around the CFA than areas to the north and south due to suggested CFA uplift rates of 0.24+0.15mm a-1. An absence of RSL records for 200km north of the CFA make mapping of its influence difficult. Additional RSL records to the north of the CFA allow for a better understanding of the asymmetrical distribution in the rate of RSL rise in this region. Because the distribution in the rate of RSLR between records is not linear it is important for these low-lying coastal communities to better understand their risk to future RSLR.

Settlement on the Shores of Lake Lisan and adjacent swamps: Hindered aridization

NASA Astrophysics Data System (ADS)

Agnon, A.; Goring-Morris, N.

2014-12-01

Increased rainfall/evaporation ratio had merged the Dead Sea and Sea of Galilee basins to a 260 km long Lake Lisan during the Last Glacial Maximum, 160 m below current mean sea level (mbsl). The timing of the natural drop to the 400 mbsl (Dead Sea level) has been precisely determined to 25-11 ka. Human settlements had initiated near the retreating shorelines at 21 ka. However, rather than following the dropping level, the subsequent settlement took advantage of swamps perched above 240 mbsl.Along with an increased number of persons in the communities that left artefacts in the lacustrine and shore sediments, the technologies for exploiting the environment for survival had evolved. Some of the finds attest to activities that were not tied immediately to physical survival. The development of art and of social behaviour raises fascinating issues regarding our perception of the capabilities and motives of Mankind during the change from hunter-gatherer subsistence to one based on cultivation of plants and livestock associated with settlement.The changes in the lifestyle are likely related to the environmental changes, some of which can be reconstructed by modern geological tools. On the other hand, some of the findings of the archaeological studies can help resolve geological issues, such as aridization around 9 ka, attested by initiation of gully washers that form boulder deposits over Netiv Hagdud site. The aridization is hindered relatively to lake level drop, presumably due to evolving spatial distribution of rainfall, where the rift shoulders still receive rain, while lake decline reflects aridization in the southern drainage, namely the Negev. This observation accords with speleothem studies from the rift shoulders.

Gradual demise of a thin southern Laurentide ice sheet recorded by Mississippi drainage.

PubMed

Wickert, Andrew D; Mitrovica, Jerry X; Williams, Carlie; Anderson, Robert S

2013-10-31

At the Last Glacial Maximum (LGM), about 21,000 years before present, land-based ice sheets held enough water to reduce global mean sea level by 130 metres. Yet after decades of study, major uncertainties remain as to the distribution of that ice. Here we test four reconstructions of North American deglacial ice-sheet history by quantitatively connecting them to high-resolution oxygen isotope (δ(18)O) records from the Gulf of Mexico using a water mixing model. For each reconstruction, we route meltwater and seasonal runoff through the time-evolving Mississippi drainage basin, which co-evolves with ice geometry and changing topography as ice loads deform the solid Earth and produce spatially variable sea level in a process known as glacial isostatic adjustment. The δ(18)O records show that the Mississippi-drained southern Laurentide ice sheet contributed only 5.4 ± 2.1 metres to global sea level rise, of which 0.66 ± 0.07 metres were released during the meltwater pulse 1A event 14,650-14,310 years before present, far less water than previously thought. In contrast, the three reconstructions based on glacial isostatic adjustment overpredict the δ(18)O-based post-LGM meltwater volume by a factor of 1.6 to 3.6. The fourth reconstruction, which is based on ice physics, has a low enough Mississippi-routed meltwater discharge to be consistent with δ(18)O constraints, but also contains the largest LGM North American ice volume. This suggests that modelling based on ice physics may be the best way of matching isotopic records while also sequestering enough water in the North American ice sheets to match the observed LGM sea level fall.

East Sea Spatial and Temporal Variability of Thermohaline Structure and Circulation Identified From Observational (T, S) Profiles

DTIC Science & Technology

2015-12-01

salinity effect caused by the Amur River’s discharge into the Tatar Strait, and a one- month delay after maximum discharge in September. The research...discovered another low salinity effect through the Korea Strait in summer by the Changjiang River’s discharge into the East China Sea, which identified... effect caused by the Amur River’s discharge into the Tatar Strait, and a one-month delay after maximum discharge in September. The research discovered

Ad-Hoc Sensor Networks for Maritime Interdiction Operations and Regional Security

DTIC Science & Technology

2012-09-01

as resistant to rough sea conditions as the SHARC, since its maximum operation limit is sea state 3. Its maximum speed approaches three knots and...which renders it corrosion resistant and lightweight. Its length is 3.2 meters with a rotor diameter at 3.3 meters. It flies at speeds of 50 knots...NMIOTC main building and to a moored training ship (see Figure 50), (2) GSM/GPRS was networked with swimmers , (3) security patrol and target vessels

Reconstruction of western Pacific and Atlantic Ocean Surface Stability during the Miocene to Quaternary based on nannofossil assemblages

NASA Astrophysics Data System (ADS)

Sato, T.; Pratiwi, S. D.; Effendi, R.

2015-12-01

We studied in detail the calcareous nannofossil assemblages of the middle Miocene to Quaternary sequences of ODP Sites 782, 1005, 1006, and 1007 located in western Pacific Ocean and Bahama Bank of Caribbean Sea. Site 1007, 1005, 1006 are situated in the cross section of Bahama Bank from near shore to offshore site. Discoaster species, which is interpreted as lower photic zone species, is increasing the relative number towards the offshore site. This means that the abundant occurrence of Discoaster specimens indicates the well stratified surface water conditions. We also correlated the variability of maximum size of "Reticulofenestra" specimens between Sites 782, 1005, 1006, and 1007 (Fig ). The variability of the maximum size of Reticulofenestra recorded in site 782 is positive correlation with those in Site 1006, 1005, and 1007. As the occurrence of large size Reticulofenestra indicate the oligotrophic and stable sea surface condition, the drastic decreasing of maximum size of Reticulofenestra fond in 2.75Ma, 3.6Ma, 5.4Ma, 9Ma and 13Ma, indicates the collapse of stable and low nutrient sea surface conditions at these ages in both Caribbean Sea and western Pacific Ocean. The events found in the sequences are correlated to closure of Central American seaway, Messinian salinity crisis, intensify the Asian Monsoon, and closure of Indonesian Sea way.

Simulated wind-generated inertial oscillations compared to current measurements in the northern North Sea

NASA Astrophysics Data System (ADS)

Bruserud, Kjersti; Haver, Sverre; Myrhaug, Dag

2018-06-01

Measured current speed data show that episodes of wind-generated inertial oscillations dominate the current conditions in parts of the northern North Sea. In order to acquire current data of sufficient duration for robust estimation of joint metocean design conditions, such as wind, waves, and currents, a simple model for episodes of wind-generated inertial oscillations is adapted for the northern North Sea. The model is validated with and compared against measured current data at one location in the northern North Sea and found to reproduce the measured maximum current speed in each episode with considerable accuracy. The comparison is further improved when a small general background current is added to the simulated maximum current speeds. Extreme values of measured and simulated current speed are estimated and found to compare well. To assess the robustness of the model and the sensitivity of current conditions from location to location, the validated model is applied at three other locations in the northern North Sea. In general, the simulated maximum current speeds are smaller than the measured, suggesting that wind-generated inertial oscillations are not as prominent at these locations and that other current conditions may be governing. Further analysis of the simulated current speed and joint distribution of wind, waves, and currents for design of offshore structures will be presented in a separate paper.

Simulated wind-generated inertial oscillations compared to current measurements in the northern North Sea

NASA Astrophysics Data System (ADS)

Bruserud, Kjersti; Haver, Sverre; Myrhaug, Dag

2018-04-01

Measured current speed data show that episodes of wind-generated inertial oscillations dominate the current conditions in parts of the northern North Sea. In order to acquire current data of sufficient duration for robust estimation of joint metocean design conditions, such as wind, waves, and currents, a simple model for episodes of wind-generated inertial oscillations is adapted for the northern North Sea. The model is validated with and compared against measured current data at one location in the northern North Sea and found to reproduce the measured maximum current speed in each episode with considerable accuracy. The comparison is further improved when a small general background current is added to the simulated maximum current speeds. Extreme values of measured and simulated current speed are estimated and found to compare well. To assess the robustness of the model and the sensitivity of current conditions from location to location, the validated model is applied at three other locations in the northern North Sea. In general, the simulated maximum current speeds are smaller than the measured, suggesting that wind-generated inertial oscillations are not as prominent at these locations and that other current conditions may be governing. Further analysis of the simulated current speed and joint distribution of wind, waves, and currents for design of offshore structures will be presented in a separate paper.

Anomalous Variability in Antarctic Sea Ice Extents During the 1960s With the Use of Nimbus Data

NASA Technical Reports Server (NTRS)

Gallaher, David W.; Campbell, G. Garrett; Meier, Walter N.

2013-01-01

The Nimbus I, II, and III satellites provide a new opportunity for climate studies in the 1960s. The rescue of the visible and infrared imager data resulted in the utilization of the early Nimbus data to determine sea ice extent. A qualitative analysis of the early NASA Nimbus missions has revealed Antarctic sea ice extents that are significant larger and smaller than the historic 1979-2012 passive microwave record. The September 1964 ice mean area is 19.7x10(exp 6) sq. km +/- 0.3x10(exp 6) sq. km. This is more the 250,000 sq. km greater than the 19.44x10(exp 6) sq. km seen in the new 2012 historic maximum. However, in August 1966 the maximum sea ice extent fell to 15.9x10(exp 6) sq. km +/- 0.3x10(exp 6) sq. km. This is more than 1.5x10(exp 6) sq. km below the passive microwave record of 17.5x10(exp 6) sq. km set in September of 1986. This variation between 1964 and 1966 represents a change of maximum sea ice of over 3x10(exp 6) sq. km in just two years. These inter-annual variations while large, are small when compared to the Antarctic seasonal cycle.

Extreme warming, photic zone euxinia and sea level rise during the Paleocene/Eocene Thermal Maximum on the Gulf of Mexico Coastal Plain; connecting marginal marine biotic signals, nutrient cycling and ocean deoxygenation

NASA Astrophysics Data System (ADS)

Sluijs, A.; van Roij, L.; Harrington, G. J.; Schouten, S.; Sessa, J. A.; LeVay, L. J.; Reichart, G.-J.; Slomp, C. P.

2013-12-01

The Paleocene/Eocene Thermal Maximum (PETM, ~56 Ma) was a ~200 kyr episode of global warming, associated with massive injections of 13C-depleted carbon into the ocean-atmosphere system. Although climate change during the PETM is relatively well constrained, effects on marine oxygen and nutrient cycling remain largely unclear. We identify the PETM in a sediment core from the US margin of the Gulf of Mexico. Biomarker-based paleotemperature proxies (MBT/CBT and TEX86) indicate that continental air and sea surface temperatures warmed from 27-29 °C to ~35 °C, although variations in the relative abundances of terrestrial and marine biomarkers may have influenced the record. Vegetation changes as recorded from pollen assemblages supports profound warming. Lithology, relative abundances of terrestrial vs. marine palynomorphs as well as dinoflagellate cyst and biomarker assemblages indicate sea level rise during the PETM, consistent with previously recognized eustatic rise. The recognition of a maximum flooding surface during the PETM changes regional sequence stratigraphic interpretations, which allows us to exclude the previously posed hypothesis that a nearby fossil found in PETM-deposits represents the first North American primate. Within the PETM we record the biomarker isorenieratane, diagnostic of euxinic photic zone conditions. A global data compilation indicates that deoxygenation occurred in large regions of the global ocean in response to warming, hydrological change, and carbon cycle feedbacks, particularly along continental margins, analogous to modern trends. Seafloor deoxygenation and widespread anoxia likely caused phosphorus regeneration from suboxic and anoxic sediments. We argue that this fuelled shelf eutrophication, as widely recorded from microfossil studies, increasing organic carbon burial along continental margins as a negative feedback to carbon input and global warming. If properly quantified with future work, the PETM offers the opportunity to assess the biogeochemical effects of enhanced phosphorus regeneration, as well as the time-scales on which this feedback operates in view of modern and future ocean deoxygenation.

Biophysics of Cold Adaptation and Acclimatization: Microbial Decomposition.

DTIC Science & Technology

1984-03-01

plant communities. Parameters such as temperature, precipitation and relative humidity, as they are related to winds and sea ice, interact to produce the...predictable pattern, 9 the occurrence of clouds, precipitation and heavy fogs build to a maximum as the number of daily sunshine hours increases. At 12...August 2, the sun finally sets for 1 hour and 25 minutes. Climatic records kept since 1934 show low precipitation levels with a 40 year mean of 11.5 cm/yr

The effect of altitude on cycling performance: a challenge to traditional concepts.

PubMed

Hahn, A G; Gore, C J

2001-01-01

Acute exposure to moderate altitude is likely to enhance cycling performance on flat terrain because the benefit of reduced aerodynamic drag outweighs the decrease in maximum aerobic power [maximal oxygen uptake (VO2max)]. In contrast, when the course is mountainous, cycling performance will be reduced at moderate altitude. Living and training at altitude, or living in an hypoxic environment (approximately 2500 m) but training near sea level, are popular practices among elite cyclists seeking enhanced performance at sea level. In an attempt to confirm or refute the efficacy of these practices, we reviewed studies conducted on highly-trained athletes and, where possible, on elite cyclists. To ensure relevance of the information to the conditions likely to be encountered by cyclists, we concentrated our literature survey on studies that have used 2- to 4-week exposures to moderate altitude (1500 to 3000 m). With acclimatisation there is strong evidence of decreased production or increased clearance of lactate in the muscle, moderate evidence of enhanced muscle buffering capacity (beta m) and tenuous evidence of improved mechanical efficiency (ME) of cycling. Our analysis of the relevant literature indicates that, in contrast to the existing paradigm, adaptation to natural or simulated moderate altitude does not stimulate red cell production sufficiently to increase red cell volume (RCV) and haemoglobin mass (Hb(mass)). Hypoxia does increase serum erthyropoietin levels but the next step in the erythropoietic cascade is not clearly established; there is only weak evidence of an increase in young red blood cells (reticulocytes). Moreover, the collective evidence from studies of highly-trained athletes indicates that adaptation to hypoxia is unlikely to enhance sea level VO2max. Such enhancement would be expected if RCV and Hb(mass) were elevated. The accumulated results of 5 different research groups that have used controlled study designs indicate that continuous living and training at moderate altitude does not improve sea level performance of high level athletes. However, recent studies from 3 independent laboratories have consistently shown small improvements after living in hypoxia and training near sea level. While other research groups have attributed the improved performance to increased RCV and VO2max, we cite evidence that changes at the muscle level (beta m and ME) could be the fundamental mechanism. While living at altitude but training near sea level may be optimal for enhancing the performance of competitive cyclists, much further research is required to confirm its benefit. If this benefit does exist, it probably varies between individuals and averages little more than 1%.

The influence of high viscosity slabs on post-glacial sea-level change: the case of Barbados

NASA Astrophysics Data System (ADS)

Austermann, Jacqueline; Mitrovica, Jerry X.; Latychev, Konstantin

2013-04-01

The coral record at Barbados is one of the best available measures of relative sea level during the last glacial cycle and has been widely used to reconstruct ice volume (or, equivalently, eustatic sea-level, ESL) changes during the last deglaciation phase of the ice age. However, to estimate ESL variations from the local relative sea level (RSL) history at Barbados, one has to account for the contaminating effect of glacial isostatic adjustment (GIA). In previous work, the GIA signal at this site has been corrected for by assuming a spherically symmetric (i.e., 1-D) viscoelastic Earth. Since Barbados is located at the margin of the South American - Caribbean subduction zone, this assumption may introduce a significant error in inferences of ice volumes. To address this issue, we use a finite-volume numerical code to model GIA in the Caribbean region including the effects of a lithosphere with variable elastic thickness, plate boundaries, lateral variations in lower mantle viscosity, and a high viscosity slab within the upper mantle. The geometry of the subducted slab is inferred from local seismicity. We find that predictions of relative sea-level change since the Last Glacial Maximum (LGM) in the Caribbean region are diminished by ~10 m, relative to 1-D calculations, which suggests that previous studies have underestimated post-LGM ESL change by the same amount. This perturbation, which largely reflects the impact of the high viscosity slab, is nearly twice the total GIA-induced departure from eustasy predicted at Barbados using the 1-D Earth model. Our calculations imply an excess ice-volume equivalent to ~130 m ESL at the LGM, which brings the Barbados-based estimate into agreement with inferences based on other far-field RSL histories, such as at Bonaparte Gulf. This inference, together with recent studies that have substantially lowered estimates of Antarctic Ice Sheet mass at LGM, suggest that a significant amount of ice remains unaccounted for in sea-level based ice sheet reconstructions. In addition, we conclude that inference of ice age ice volumes derived from RSL histories at sites in proximity to subduction zones must incorporate slab structure into the numerical predictions of the GIA process.

Defining the ecologically relevant mixed-layer depth for Antarctica's coastal seas

NASA Astrophysics Data System (ADS)

Carvalho, Filipa; Kohut, Josh; Oliver, Matthew J.; Schofield, Oscar

2017-01-01

Mixed-layer depth (MLD) has been widely linked to phytoplankton dynamics in Antarctica's coastal regions; however, inconsistent definitions have made intercomparisons among region-specific studies difficult. Using a data set with over 20,000 water column profiles corresponding to 32 Slocum glider deployments in three coastal Antarctic regions (Ross Sea, Amundsen Sea, and West Antarctic Peninsula), we evaluated the relationship between MLD and phytoplankton vertical distribution. Comparisons of these MLD estimates to an applied definition of phytoplankton bloom depth, as defined by the deepest inflection point in the chlorophyll profile, show that the maximum of buoyancy frequency is a good proxy for an ecologically relevant MLD. A quality index is used to filter profiles where MLD is not determined. Despite the different regional physical settings, we found that the MLD definition based on the maximum of buoyancy frequency best describes the depth to which phytoplankton can be mixed in Antarctica's coastal seas.

Multi-decadal storminess fluctuations of Black Sea due to North Atlantic Oscillation

NASA Astrophysics Data System (ADS)

Kuznetsov, Sergey; Saprykina, Yana; Grigorieva, Victoria; Aydoǧan, Berna; Aydoǧan, Burak

2017-04-01

Storminess variability is of key importance for many marine applications, naval and coastal engineering. Studying the evolution of this phenomenon along with large scale atmospheric patterns and being able to predict them is crucial for in the context of rising sea level due to climate change what make the low-lying coasts in the Black Sea to become increasingly vulnerable to marine hazards. The aim of this work is to clarify the trends, statistics and reasons of variations of storminess in dependence of such climatic characteristic as NAO (North Atlantic Oscillation Index). The analysis of Black Sea storminess activity was performed on the base of visual wave observations (Voluntary Observing Ship or VOS) for the period 1970-2011. Annual means and maximum heights of wind-driven seas and swell waves averaging over whole Black Sea area were investigated separately. The both wind-driven seas and swell demonstrate the decreasing in heights about 10% the same as their periods for the chosen time frame. Parametric spectral analysis was performed. The periods of wave height fluctuations for wind-driven seas and swell were shown to coincide with each other and with periods of low frequency fluctuation of NOA: 14 and 4 year respectively. Correlation coefficients of wave height and NOA were 0.3 for swell and 0.4 for wind-driven sea. Nonlinear regularities of NAO fluctuations were investigated using wavelet and spavlet (spectra of modules of wavelet coefficients) analyses. Their influence on variability of storminess in Black Sea is discussed. The reported study was funded by RFBR (project No. 16-55-76002 ERA_a) and by TUBITAK (project No. 116M061) in frame of BS STEMA project.

Tracing the source of deep water in the Arctic Ocean with 17Oexcess of dissolved O2

NASA Astrophysics Data System (ADS)

Smethie, W. M., Jr.; Luz, B.; Barkan, E.; Broecker, W. S.

2014-12-01

The 17Oexcess of dissolved O2 (17Δ) in the ocean is a unique property which is useful for telling apart O2 produced by marine photosynthesis (bio-O2) from atmospheric O2. Unlike O2 concentration, 17Δ is not affected by respiration and thus behaves conservatively in the deep sea. In general, 17Δ in the oceanic mixed layer is low due to the dominance of air-sea gas exchange. In contrast, in the Arctic mixed-layer 17Δ is higher because sufficient light penetrates through the sea-ice cover and drives photosynthesis, but air-sea gas exchange is retarded by sea ice cover. We have preliminary 17Δ data from depth profiles in the Eurasian and Makarov basins. In both, the fraction of bio-O2 is about 20 % in the surface mixed layer. However, the vertical distribution beneath the mixed layer at the two stations is substantially different. In the Makarov Basin there is a layer of Pacific Water centered at about 100 m, which enters the Arctic Ocean through Bering Strait and is modified as it flows across the wide Chukchi and Siberian shelves. It has a strong maximum in 17Δ, equivalent to ~30% bio-O2. 17Δ then decreases through the underlying halocline to a minimum between 500 and 700 m, which lies within the Barents Sea Branch of Atlantic Water (BSBW) indicating ~15% bio-O2. At the Eurasian Basin station, 17Δ decreases from the mixed layer through the halocline reaching a minimum at the temperature maximum of Atlantic Water. This temperature maximum marks the core of the Fram Strait Branch of Atlantic Water (FSBW). 17Δ then increases to a maximum indicating ~20% bio-O2 between 500 and 700 m. The BSBW is produced as Atlantic Water flows through the shallow Barents Sea becoming denser than FSBW and enters the Eurasian Basin through the Santa Anna Trough beneath the FSBW. Our 17Δ measurements suggest that waters of Pacific and Atlantic origin that transit across the wide Arctic continental shelves acquire a high 17Δ signal indicative of photosynthesis in ice covered water.

Future hurricane storm surge risk for the U.S. gulf and Florida coasts based on projections of thermodynamic potential intensity

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

Balaguru, Karthik; Judi, David R.; Leung, L. Ruby

Coastal populations in the global tropics and sub-tropics are vulnerable to the devastating impacts of hurricane storm surge and this risk is only expected to rise under climate change. In this study, we address this issue for the U.S. Gulf and Florida coasts. Using the framework of Potential Intensity, observations and output from coupled climate models, we show that the future large-scale thermodynamic environment may become more favorable for hurricane intensification. Under the RCP 4.5 emissions scenario and for the peak hurricane season months of August–October, we show that the mean intensities of Atlantic hurricanes may increase by 1.8–4.2 %more » and their lifetime maximum intensities may increase by 2.7–5.3 % when comparing the last two decades of the 20th and 21st centuries. We then combine our estimates of hurricane intensity changes with projections of sea-level rise to understand their relative impacts on future storm surge using simulations with the National Weather Service’s SLOSH (Sea, Lake, and Overland Surges from Hurricanes) model for five historical hurricanes that made landfall in the Gulf of Mexico and Florida. Considering uncertainty in hurricane intensity changes and sea-level rise, our results indicate a median increase in storm surge ranging between 25 and 47 %, with changes in hurricane intensity increasing future storm surge by about 10 % relative to the increase that may result from sea level rise alone, with highly non-linear response of population at risk.« less

Sources of Arctic Ocean upper halocline and changes in its properties

NASA Astrophysics Data System (ADS)

Anderson, L. G.; Andersson, P. S.; Bjvrk, G. M.; Jutterstrom, S.; Wahlstrom, I.

2011-12-01

The upper halocline of the Arctic Ocean has a distinct chemical signature by its high nutrient and partial pressure of carbon dioxide as well as low oxygen and pH values. This signature is formed along the bottoms of the Siberian shelf seas, primarily the Chukchi and East Siberian Seas, by a combination of mineralization of organic matter and release of the decay products to the sea ice brine enriched bottom water. In this contribution we use salinity and total alkalinity data to show that the fraction of sea ice brine in the nutrient enriched upper halocline water in the central Arctic Ocean is up to 4%. This water of low pH, and thus also low in calcium carbonate solubility, is found between about 100 and 200 m depth and is thus close to the productive surface water in a future central Arctic Ocean of less summer sea ice cover. In the East Siberian Sea the bottom waters with exceptional high nutrient concentration and low pH have typically between 5 and 10% of sea ice brine as computed form salinity and oxygen-18 vales. On the continental slope, over bottom depths of 15-200 m, the brine contribution was 6% at the nutrient maximum depth (50-100 m). At the same location as well as over deeper waters the silicate maximum was found over a wider salinity range than traditionally, in agreement with observations of Nishino et al (J. Oceanogr, Vol. 65, pp. 871 to 883, 2009) in the area of the deep Arctic Ocean east of the Chukchi Plateau. However, the water with lowest salinity (~32.5) in the silicate maximum had maximum in nitrate deficit expressed as N** (= [NO3] - 16[PO4] + 2.9) and the waters with highest salinity (~34.5) had the lowest oxygen concentration. This pattern is not obvious and point to at least two different biochemical environments within the East Siberian Sea that has not been observed before and could be a sign of a changing marine climate in the East Siberian Sea. One cause could be more open water in the summer season followed by more sea ice formation and brine production in the fall/winter. Strong signals of sea ice brine was also observed in the nutrient rich water found in the Herald Valley of the Chukchi Sea. This water is likely flowing north and has traditionally been assumed to be a significant contributor to the upper halocline in the central Arctic Ocean. A challenging question for the future is; are changing sea ice conditions and biogeochemical processes on the Siberian shelves impacting the composition of the halocline of the central Arctic Ocean. A follow up issue is then what effect this might have on the ecosystem of these waters.

Atmospheric Influences on the Anomalous 2016 Antarctic Sea Ice Decay

NASA Astrophysics Data System (ADS)

Raphael, M. N.; Schlosser, E.; Haumann, A.

2017-12-01

Over the past three decades, a small but significant increase in sea ice extent (SIE) has been observed in the Antarctic. However, in 2016 there was a surprisingly early onset of the melt season. The maximum Antarctic SIE was reached in August rather than end of September, and was followed by a rapid decrease. The decline of the sea ice area (SIA) started even earlier, in July. The retreat of the ice was particularly large in November where Antarctic SIE exhibited a negative anomaly (compared to the 1981-2010 average) of almost 2 Mio. km2, which, combined with reduced Arctic SIE, led to a distinct minimum in global SIE. And, satellite observations show that from November 2016 to February 2017, the daily Antarctic SIE has been at record low levels. We use sea level pressure and geopotential height data from the ECMWF- Interim reanalysis, in conjunction with sea ice data obtained from the National Snow and Ice Data Centre (NSIDC), to investigate possible atmospheric influences on the observed phenomena. Indications are that both the onset of the melt in July and the rapid decrease in SIA and SIE in November were triggered by atmospheric flow patterns related to a positive Zonal Wave 3 index, i.e. synoptic situations leading to strong meridional flow. Additionally the Southern Annular Mode (SAM) index reached its second lowest November value since the beginning of the satellite observations. It is likely that the SIE decrease was preconditioned by SIA decrease. Positive feedback effects led to accelerated melt and consequently to the extraordinary low November SIE.

The last glaciation of Bear Peninsula, central Amundsen Sea Embayment of Antarctica: Constraints on timing and duration revealed by in situ cosmogenic 14C and 10Be dating

NASA Astrophysics Data System (ADS)

Johnson, Joanne S.; Smith, James A.; Schaefer, Joerg M.; Young, Nicolás E.; Goehring, Brent M.; Hillenbrand, Claus-Dieter; Lamp, Jennifer L.; Finkel, Robert C.; Gohl, Karsten

2017-12-01

Ice streams in the Pine Island-Thwaites region of West Antarctica currently dominate contributions to sea level rise from the Antarctic ice sheet. Predictions of future ice-mass loss from this area rely on physical models that are validated with geological constraints on past extent, thickness and timing of ice cover. However, terrestrial records of ice sheet history from the region remain sparse, resulting in significant model uncertainties. We report glacial-geological evidence for the duration and timing of the last glaciation of Hunt Bluff, in the central Amundsen Sea Embayment. A multi-nuclide approach was used, measuring cosmogenic 10Be and in situ14C in bedrock surfaces and a perched erratic cobble. Bedrock 10Be ages (118-144 ka) reflect multiple periods of exposure and ice-cover, not continuous exposure since the last interglacial as had previously been hypothesized. In situ14C dating suggests that the last glaciation of Hunt Bluff did not start until 21.1 ± 5.8 ka - probably during the Last Glacial Maximum - and finished by 9.6 ± 0.9 ka, at the same time as ice sheet retreat from the continental shelf was complete. Thickening of ice at Hunt Bluff most likely post-dated the maximum extent of grounded ice on the outer continental shelf. Flow re-organisation provides a possible explanation for this, with the date for onset of ice-cover at Hunt Bluff providing a minimum age for the timing of convergence of the Dotson and Getz tributaries to form a single palaeo-ice stream. This is the first time that timing of onset of ice cover has been constrained in the Amundsen Sea Embayment.

Climatology of the autumn Red Sea trough

NASA Astrophysics Data System (ADS)

Awad, Adel M.; Mashat, Abdul-Wahab S.

2018-03-01

In this study, the Sudan low and the associated Red Sea trough (RST) are objectively identified using the mean sea level pressure (SLP) data from the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis dataset covering the period 1955-2015. The Sudan low was detected in approximately 60.6% of the autumn periods, and approximately 83% of the detected low-pressure systems extended into RSTs, with most generated at night and during cold months. The distribution of the RSTs demonstrated that Sudan, South Sudan and Red Sea are the primary development areas of the RSTs, generating 97% of the RSTs in the study period. In addition, the outermost areas affected by RSTs, which include the southern, central and northern Red Sea areas, received approximately 91% of the RSTs originating from the primary generation areas. The synoptic features indicated that a Sudan low developed into an RST when the Sudan low deepened in the atmosphere, while the low pressures over the southern Arabian Peninsula are shallow and the anticyclonic systems are weakened over the northern Red Sea. Moreover, stabile areas over Africa and Arabian Peninsula form a high stability gradient around the Red Sea and the upper maximum winds weaken. The results of the case studies indicate that RSTs extend northward when the upper cyclonic and anticyclonic systems form a high geopotential gradient over Arabian Peninsula. Furthermore, the RST is oriented from the west to the east when the Azores high extends eastward and the Siberian high shrinks eastward or shifts northward.

Star-shaped feeding traces produced by echiuran worms on the deep-sea floor of the Bay of Bengal

NASA Astrophysics Data System (ADS)

Ohta, Suguru

1984-12-01

Many star-shaped foraging traces were observed in bottom photographs of the deep-sea floor taken in the Bay of Bengal between the depths of 5025 and 2635 m. They were classified into 10 types according to their dimensions, aspect ratios (length/width) of their spokes, features of the central structure, and possible production mechanisms. The proboscis of a deep-sea bonellid echiuran worm was photographed at a depth of 2635 m in the act of producing one of the star-shaped foraging traces. On the basis of photographic observations and observations of shallow-water forms, several types of the feeding traces can be ascribed to the foraging of deep-sea echiuran worms on surface detritus. At least four types of the star-shaped trace are probably produced by deep-sea bonellid worms, and a linear correlation could be found between the aspect ratios of the spokes and maximum number of spokes around the central hole. A geometrical model experiment stimulating the feeding behavior of a bonellid worm suggested simple behavioral principles which afford maximum utilization of the surface area around a central hole with least expenditure of energy. The prediction of the maximum number of spokes for a given aspect of spokes by the model experiment agreed well with those observed, both utilizing about 76% of the fresh sediment surface within the span of the probiscis around a central hole. This efficient feeding pattern may have adaptive value in deep-sea environments such as the central part of the Bay of Bengal, where energy input is limited.

Recalculated Areas for Maximum Ice Extents of the Baltic Sea During Winters 1971-2008

NASA Astrophysics Data System (ADS)

Niskanen, T.; Vainio, J.; Eriksson, P.; Heiler, I.

2009-04-01

Publication of operational ice charts in Finland was started from the Baltic Sea in a year 1915. Until year 1993 all ice charts were hand drawn paper copies but in the year 1993 ice charting software IceMap was introduced. Since then all ice charts were produced digitally. Since the year 1996 IceMap has had an option that user can calculate areas of single ice area polygons in the chart. Using this option the area of the maximum ice extent can be easily solved fully automatically. Before this option was introduced (and in full operation) all maximum extent areas were calculated manually by a planimeter. During recent years it has become clear that some areas calculated before 1996 don't give the same result as IceMap. Differences can come from for example inaccuracy of old coastlines, map projections, the calibration of the planimeter or interpretation of old ice area symbols. Old ice charts since winter 1970-71 have now been scanned, rectified and re-drawn. New maximum ice extent areas for Baltic Sea have now been re-calculated. By these new technological tools it can be concluded that in some cases clear differences can be found.

Seasonal investigation of trace element contents in commercially valuable fish species from the Black sea, Turkey.

PubMed

Mendil, Durali; Demirci, Zafer; Tuzen, Mustafa; Soylak, Mustafa

2010-03-01

Fish species (Sarda sarda, Mulus barbatus ponticus, Trachurus trachurus and Merlangius merlangus) were collected from the Black sea, Turkey between 2008 and 2009 (spring, summer, autumn and winter). The samples were analyzed using flame and graphite furnace atomic absorption spectrometry after microwave digestion. The maximum metal concentrations were found to be as 25.5-41.4 microg/g (Fe), 17.8-25.7 microg/g (Zn), 0.28-0.64 microg/g (Pb), 0.64-0.99 microg/g (Cr), 1.3-3.6 microg/g (Mn), 1.4-1.9 microg/g (Cu), 0.18-0.35 microg/g (Cd) and 0.25-0.42 microg/g (Co) for fish species. The concentration of trace metals in samples is depended on fish species. Some species is accumulated trace metals at high ratio. Trace element levels in analyzed fish species were acceptable to human consumption at nutritional and toxic levels. The levels of lead and cadmium in fish samples were higher than the recommended legal limits. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

Diatom evidence for earthquake-induced subsidence and tsunami 300 yr ago in southern coastal Washington

USGS Publications Warehouse

Hemphill-Haley, E.

1995-01-01

Fossil diatoms from four stratigraphic sections along the tidal Niawiakum River, southwestern Washington, provide an independent paleoecological test of a relative sea-level rise that has been attributed to subsidence during an inferred earthquake in the Cascadia subduction zone about 300 yr ago. Diatom assemblages in a buried soil and overlying mud indicate a sudden and lasting shift from marshes and forests near or above highest tides to mud flats and incipient tidal marshes, with a progressive return to high-level tidal marshes by sediment aggradation and, perhaps, gradual tectonic uplift. The maount of coseismic submergence required to generate the paleoecological changes observed at these sites could have ranged from a minimum of 0.8-1.0m to a maximum of ~3.0m. The following tsunami extended farther landward than was previously inferred from the stratigraphy. These data rule out proposed alternatives to the coseismic subsidence model - that is, climatically induced sea-level rise, temporary submergence caused by storms - and support the hypothesis that a great earthquake struck southwestern Washington 300 yr ago. -from Author

Diversity of terrestrial avifauna in response to distance from the shoreline of the Salton Sea

USGS Publications Warehouse

Mendelsohn, M.B.; Boarman, W.I.; Fisher, R.N.; Hathaway, S.A.

2007-01-01

Large aquatic bodies influence surrounding terrestrial ecosystems by providing water and nutrients. In arid landscapes, the increased primary productivity that results may greatly enhance vertebrate biodiversity. The Salton Sea, a large saline lake in the Colorado Desert of southern California, provides nutrients in the form of hundreds of thousands of dead fish carcasses, brine flies, and chemical compounds through windborne salt sea spray. We performed point counts for landbirds and shorebirds monthly or every other month between March 2001 and February 2002 across a sampling grid of 35 points along the west edge of Salton Sea. We found that avian diversity (numbers of species and numbers per species) was dependent on proximity to the Sea. Diversity was at a maximum nearest the shore, and was significantly lower away from the Sea's edge, at all surveyed distances up to 1 km from the shore. Cover by the dominant shrubs on the study site also corresponded to proximity to the water's edge. Whereas one may hypothesize that the avian diversity patterns are caused by these differences in vegetation structure, our data did not support this. Future studies should further investigate this potential correlation between vegetation and bird patterns. Until more is understood about the relationship between elevated avian diversity and the physical environment of the land-shore interface, our results suggest that the Sea's surface be stabilized near its present level. Future management schemes at the Salton Sea that include reductions of water sources should be carefully analyzed, so as to not jeopardize the terrestrial avifauna at this unique ecosystem. ?? 2006 Elsevier Ltd. All rights reserved.

A binary genetic programing model for teleconnection identification between global sea surface temperature and local maximum monthly rainfall events

NASA Astrophysics Data System (ADS)

Danandeh Mehr, Ali; Nourani, Vahid; Hrnjica, Bahrudin; Molajou, Amir

2017-12-01

The effectiveness of genetic programming (GP) for solving regression problems in hydrology has been recognized in recent studies. However, its capability to solve classification problems has not been sufficiently explored so far. This study develops and applies a novel classification-forecasting model, namely Binary GP (BGP), for teleconnection studies between sea surface temperature (SST) variations and maximum monthly rainfall (MMR) events. The BGP integrates certain types of data pre-processing and post-processing methods with conventional GP engine to enhance its ability to solve both regression and classification problems simultaneously. The model was trained and tested using SST series of Black Sea, Mediterranean Sea, and Red Sea as potential predictors as well as classified MMR events at two locations in Iran as predictand. Skill of the model was measured in regard to different rainfall thresholds and SST lags and compared to that of the hybrid decision tree-association rule (DTAR) model available in the literature. The results indicated that the proposed model can identify potential teleconnection signals of surrounding seas beneficial to long-term forecasting of the occurrence of the classified MMR events.

Internal tidal currents in the Gaoping (Kaoping) Submarine Canyon

USGS Publications Warehouse

Lee, I.-H.; Wang, Y.-H.; Liu, J.T.; Chuang, W.-S.; Xu, Jie

2009-01-01

Data from five separate field experiments during 2000-2006 were used to study the internal tidal flow patterns in the Gaoping (formerly spelled Kaoping) Submarine Canyon. The internal tides are large with maximum interface displacements of about 200??m and maximum velocities of over 100cm/s. They are characterized by a first-mode velocity and density structure with zero crossing at about 100??m depth. In the lower layer, the currents increase with increasing depth. The density interface and the along-channel velocity are approximately 90?? out-of-phase, suggesting a predominant standing wave pattern. However, partial reflection is indicated as there is a consistent phase advance between sea level and density interface along the canyon axis. ?? 2008 Elsevier B.V. All rights reserved.

Post-glacial variations of sea ice cover and river discharge in the western Laptev Sea (Arctic Ocean) - a high-resolution study over the last 18 ka

NASA Astrophysics Data System (ADS)

Hörner, Tanja; Stein, Ruediger; Fahl, Kirsten

2015-04-01

Here, we provide a high-resolution reconstruction of sea-ice cover variations in the western Laptev Sea, a crucial area in terms of sea-ice production in the Arctic Ocean and a region characterized by huge river discharge. Furthermore, the shallow Laptev Sea was strongly influenced by the post-glacial sea-level rise that should also be reflected in the sedimentary records. The sea Ice Proxy IP25 (Highly-branched mono-isoprenoid produced by sea-ice algae; Belt et al., 2007) was measured in two sediment cores from the western Laptev Sea (PS51/154, PS51/159) that offer a high-resolution composite record over the last 18 ka. In addition, sterols are applied as indicator for marine productivity (brassicasterol, dinosterol) and input of terrigenous organic matter by river discharge into the ocean (campesterol, ß-sitosterol). The sea-ice cover varies distinctly during the whole time period and shows a general increase in the Late Holocene. A maximum in IP25 concentration can be found during the Younger Dryas. This sharp increase can be observed in the whole circumarctic realm (Chukchi Sea, Bering Sea, Fram Strait and Laptev Sea). Interestingly, there is no correlation between elevated numbers of ice-rafted debris (IRD) interpreted as local ice-cap expansions (Taldenkova et al. 2010), and sea ice cover distribution. The transgression and flooding of the shelf sea that occurred over the last 16 ka in this region, is reflected by decreasing terrigenous (riverine) input, reflected in the strong decrease in sterol (ß-sitosterol and campesterol) concentrations. References Belt, S.T., Massé, G., Rowland, S.J., Poulin, M., Michel, C., LeBlanc, B., 2007. A novel chemical fossil of palaeo sea ice: IP25. Organic Geochemistry 38 (1), 16e27. Taldenkova, E., Bauch, H.A., Gottschalk, J., Nikolaev, S., Rostovtseva, Yu., Pogodina, I., Ya, Ovsepyan, Kandiano, E., 2010. History of ice-rafting and water mass evolution at the northern Siberian continental margin (Laptev Sea) during Late Glacial and Holocene times. Quaternary Science Reviews 29 (27-28), 3919-3935.

High-resolution record of last post-glacial variations of sea-ice cover and river discharge in the western Laptev Sea (Arctic Ocean)

NASA Astrophysics Data System (ADS)

Stein, R. H.; Hörner, T.; Fahl, K.

2014-12-01

Here, we provide a high-resolution reconstruction of sea-ice cover variations in the western Laptev Sea, a crucial area in terms of sea-ice production in the Arctic Ocean and a region characterized by huge river discharge. Furthermore, the shallow Laptev Sea was strongly influenced by the post-glacial sea-level rise that should also be reflected in the sedimentary records. The sea Ice Proxy IP25 (Highly-branched mono-isoprenoid produced by sea-ice algae; Belt et al., 2007) was measured in two sediment cores from the western Laptev Sea (PS51/154, PS51/159) that offer a high-resolution composite record over the last 18 ka. In addition, sterols are applied as indicator for marine productivity (brassicasterol, dinosterol) and input of terrigenous organic matter by river discharge into the ocean (campesterol, ß-sitosterol). The sea-ice cover varies distinctly during the whole time period and shows a general increase in the Late Holocene. A maximum in IP25 concentration can be found during the Younger Dryas. This sharp increase can be observed in the whole circumarctic realm (Chukchi Sea, Bering Sea, Fram Strait and Laptev Sea). Interestingly, there is no correlation between elevated numbers of ice-rafted debris (IRD) interpreted as local ice-cap expansions (Taldenkova et al. 2010), and sea ice cover distribution. The transgression and flooding of the shelf sea that occurred over the last 16 ka in this region, is reflected by decreasing terrigenous (riverine) input, reflected in the strong decrease in sterol (ß-sitosterol and campesterol) concentrations. ReferencesBelt, S.T., Massé, G., Rowland, S.J., Poulin, M., Michel, C., LeBlanc, B., 2007. A novel chemical fossil of palaeo sea ice: IP25. Organic Geochemistry 38 (1), 16e27. Taldenkova, E., Bauch, H.A., Gottschalk, J., Nikolaev, S., Rostovtseva, Yu., Pogodina, I., Ya, Ovsepyan, Kandiano, E., 2010. History of ice-rafting and water mass evolution at the northern Siberian continental margin (Laptev Sea) during Late Glacial and Holocene times. Quaternary Science Reviews 29 (27-28), 3919-3935.

Future Wave Height Situation estimated by the Latest Climate Scenario around Funafuti Atoll, Tuvalu

NASA Astrophysics Data System (ADS)

Sato, D.; Yokoki, H.; Kuwahara, Y.; Yamano, H.; Kayanne, H.; Okajima, H.; Kawamiya, M.

2012-12-01

Sea-level rise due to the global warming is significant phenomenon to coastal region in the world. Especially the atoll islands, which are low-lying and narrow, have high vulnerability against the sea-level rise. Recently the improved future climate projection (MIROC-ESM) was provided by JAMSTEC, which adopted the latest climate scenarios based on the RCP (Representative Concentration Pathway) of the green house gasses. Wave field simulation including the latest sea-level rise pathway by MIROC-ESM was conducted to understand the change of significant wave heights in Funafuti Atoll, Tuvalu, which was an important factor to manage the coast protection. MIROC-ESM provides monthly sea surface height in the fine gridded world (1.5 degree near the equator). Wave field simulation was conducted using the climate scenario of RCP45 in which the radioactive forcing of the end of 21st century was stabilized to 4.5 W/m2. Sea-level rise ratio of every 10 years was calculated based on the historical data set from 1850 to 2005 and the estimated data set from 2006 to 2100. In that case, the sea-level increases by 10cm after 100 years. In this study, the numerical simulation of wave field at the rate of sea-level rise was carried out using the SWAN model. The wave and wind conditions around Funafuti atoll is characterized by two seasons that are the trade (Apr. - Nov.) and non-trade (Jan. - Mar., Dec.) wind season. Then, we set up the two seasonal boundary conditions for one year's simulation, which were calculated from ECMWF reanalysis data. Simulated results of significant wave heights are analyzed by the increase rate (%) calculated from the base results (Average for 2000 - 2005) and the results of 2100. Calculated increase rate of the significant wave height for both seasons was extremely high on the reef-flat. Maximum increase rates of the trade and non-trade wind season were 1817% and 686%, respectively. The southern part of the atoll has high increasing rate through the two seasons. In the non-trade wind season, the northern tip and the southern part of the island were higher increase rate in the lagoon-side coasts, which was about 7%, and the average rate was 3.4%. On the other hand, the average rate in the trade wind season was 5.0%. Ocean side coast has high increase rate through the two seasons. Especially, the very large rate was calculated in the northern part of the Fongafale Island locally. The DEM data in the middle of Fongafale Island, which is most populated area in the island, showed that the northern oceanic coast has wide and high storm ridge and the increase rate was extremely large there. In such coasts, sea-level rise due to global warming has same effect as storm surge due to tropical cyclone in the point of increasing the sea-level, although the time scale of them is not same. Thus we can consider that the calculated area with large increase rate has already experienced the high wave due to tropical cyclone, which was enabled to construct the wide and high storm ridge. This result indicated that the effective coastal management under the sea-level rise needs to understand not only the quantitative estimation of the future situation but also the protect potential constructed by the present wave and wind condition.

Midlatitude cooling caused by geomagnetic field minimum during polarity reversal.

PubMed

Kitaba, Ikuko; Hyodo, Masayuki; Katoh, Shigehiro; Dettman, David L; Sato, Hiroshi

2013-01-22

The climatic effects of cloud formation induced by galactic cosmic rays (CRs) has recently become a topic of much discussion. The CR-cloud connection suggests that variations in geomagnetic field intensity could change climate through modulation of CR flux. This hypothesis, however, is not well-tested using robust geological evidence. Here we present paleoclimate and paleoenvironment records of five interglacial periods that include two geomagnetic polarity reversals. Marine oxygen isotope stages 19 and 31 contain both anomalous cooling intervals during the sea-level highstands and the Matuyama-Brunhes and Lower Jaramillo reversals, respectively. This contrasts strongly with the typical interglacial climate that has the temperature maximum at the sea-level peak. The cooling occurred when the field intensity dropped to <40% of its present value, for which we estimate >40% increase in CR flux. The climate warmed rapidly when field intensity recovered. We suggest that geomagnetic field intensity can influence global climate through the modulation of CR flux.

Midlatitude cooling caused by geomagnetic field minimum during polarity reversal

PubMed Central

Kitaba, Ikuko; Hyodo, Masayuki; Katoh, Shigehiro; Dettman, David L.; Sato, Hiroshi

2013-01-01

The climatic effects of cloud formation induced by galactic cosmic rays (CRs) has recently become a topic of much discussion. The CR–cloud connection suggests that variations in geomagnetic field intensity could change climate through modulation of CR flux. This hypothesis, however, is not well-tested using robust geological evidence. Here we present paleoclimate and paleoenvironment records of five interglacial periods that include two geomagnetic polarity reversals. Marine oxygen isotope stages 19 and 31 contain both anomalous cooling intervals during the sea-level highstands and the Matuyama–Brunhes and Lower Jaramillo reversals, respectively. This contrasts strongly with the typical interglacial climate that has the temperature maximum at the sea-level peak. The cooling occurred when the field intensity dropped to <40% of its present value, for which we estimate >40% increase in CR flux. The climate warmed rapidly when field intensity recovered. We suggest that geomagnetic field intensity can influence global climate through the modulation of CR flux. PMID:23297205

Tides in the Black Sea: Observations and Numerical Modelling

NASA Astrophysics Data System (ADS)

Medvedev, Igor P.

2018-05-01

Longterm hourly data from 28 tide gauges were used to examine the main features of tides in the Black Sea. The tides in this basin are directly caused by tide-generating forces and the semidiurnal tides prevail over diurnal tides. Based on the Princeton Ocean Model (POM), a numerical model of tides in the Black Sea and adjacent Sea of Azov was developed and found to be in good agreement with tide gauge observations. Detailed tidal charts for amplitudes and phase lags of the major tidal harmonics in these two seas were constructed. The results of the numerical modelling and observations reveal for the semidiurnal tides the presence of an amphidromy with clockwise rotation and another one with counterclockwise rotation for the diurnal tides, both located in the central part of the sea near the Crimean Peninsula. Therefore, for this part of the sea the amplitudes of harmonics M 2 and K 1 are less than 0.1 cm. Relatively larger M 2 amplitudes are observed on the east and west coasts of the sea (2-3 cm). The maximum amplitude of the harmonic M 2 was found at Karkinit Bay—up to 4.5 cm—while the maximum tidal range varies from 1 cm near the Crimean Peninsula to 18-19 cm in the Dnieper-Bug Estuary and Karkinit Bay. Radiational tides, initiated mainly by sea breezes, make an important contribution to the formation of tidal oscillations in the Dnieper-Bug Estuary.

Mechanisms and Effects of Summertime Transport of African Dust Through the Tokar Mountain Gap to the Red Sea and Arabian Peninsula

NASA Astrophysics Data System (ADS)

Kalenderski, S.; Stenchikov, G. L.

2015-12-01

Very high dust loading over the Red Sea region in summer strongly affects the nutrition balance and thermal and dynamic regimes of the sea. The observations suggest that small-scale local dynamic and orographic effects, from both the Arabian and African sides, strongly contribute to dust plume formation. To better understand and quantify these processes we present here the first high resolution modeling study of the dust outbreak phenomena in June 2012 over East Africa, the Red Sea, and the Arabian Peninsula using the WRF-Chem model. We identified several dust generating dynamical processes that range from convective to synoptic scales, including: synoptic cyclones, nocturnal low-level jets, and cold pools of mesoscale convective systems. The simulations reveal an eastward transport of African dust across the Red Sea. Over the northern part of the Red Sea most of the dust transport occurs beyond 2 km above ground level and is strengthened by a pressure gradient formed by low pressure over the eastern Mediterranean and high pressure over the Arabian Peninsula. Across the central and southern parts of the Red Sea dust is mostly transported below 2 km height. During the study period dust is a dominant contributor (87%) to aerosol optical depth (AOD), producing a domain average cooling effect of -12.1 W m-2 at surface, a warming of 7.1 W m-2 in the atmosphere, and a residual cooling of -4.9 W m-2 at the top of the atmosphere. WRF-Chem simulations demonstrate that both dry and wet deposition processes contribute significantly to dust removal from the atmosphere. During the dust outbreak 49.2 Tg of dust deposits within the calculation domain, which is approximately 90% of the total dust emission of 54.5 Tg. Model results compare well with available ground-based and satellite observations but generally underestimate the observed AOD maximum values.

Warming, euxinia and sea level rise during the Paleocene-Eocene Thermal Maximum on the Gulf Coastal Plain: implications for ocean oxygenation and nutrient cycling

NASA Astrophysics Data System (ADS)

Sluijs, A.; van Roij, L.; Harrington, G. J.; Schouten, S.; Sessa, J. A.; LeVay, L. J.; Reichart, G.-J.; Slomp, C. P.

2014-07-01

The Paleocene-Eocene Thermal Maximum (PETM, ~ 56 Ma) was a ~ 200 kyr episode of global warming, associated with massive injections of 13C-depleted carbon into the ocean-atmosphere system. Although climate change during the PETM is relatively well constrained, effects on marine oxygen concentrations and nutrient cycling remain largely unclear. We identify the PETM in a sediment core from the US margin of the Gulf of Mexico. Biomarker-based paleotemperature proxies (methylation of branched tetraether-cyclization of branched tetraether (MBT-CBT) and TEX86) indicate that continental air and sea surface temperatures warmed from 27-29 to ~ 35 °C, although variations in the relative abundances of terrestrial and marine biomarkers may have influenced these estimates. Vegetation changes, as recorded from pollen assemblages, support this warming. The PETM is bracketed by two unconformities. It overlies Paleocene silt- and mudstones and is rich in angular (thus in situ produced; autochthonous) glauconite grains, which indicate sedimentary condensation. A drop in the relative abundance of terrestrial organic matter and changes in the dinoflagellate cyst assemblages suggest that rising sea level shifted the deposition of terrigenous material landward. This is consistent with previous findings of eustatic sea level rise during the PETM. Regionally, the attribution of the glauconite-rich unit to the PETM implicates the dating of a primate fossil, argued to represent the oldest North American specimen on record. The biomarker isorenieratene within the PETM indicates that euxinic photic zone conditions developed, likely seasonally, along the Gulf Coastal Plain. A global data compilation indicates that O2 concentrations dropped in all ocean basins in response to warming, hydrological change, and carbon cycle feedbacks. This culminated in (seasonal) anoxia along many continental margins, analogous to modern trends. Seafloor deoxygenation and widespread (seasonal) anoxia likely caused phosphorus regeneration from suboxic and anoxic sediments. We argue that this fueled shelf eutrophication, as widely recorded from microfossil studies, increasing organic carbon burial along many continental margins as a negative feedback to carbon input and global warming. If properly quantified with future work, the PETM offers the opportunity to assess the biogeochemical effects of enhanced phosphorus regeneration, as well as the timescales on which this feedback operates in view of modern and future ocean deoxygenation.

Origin and depositional environment of fine-grained sediments since the last glacial maximum in the southeastern Yellow Sea: evidence from rare earth elements

NASA Astrophysics Data System (ADS)

Um, In Kwon; Choi, Man Sik; Lee, Gwang Soo; Chang, Tae Soo

2015-12-01

Despite the well-reconstructed seismic stratigraphy of the Holocene mud deposit in the southeastern Yellow Sea, known as the Heuksan mud belt (HMB), the provenances of these sediments and their depositional environments are unclear, especially for the fine-grained sediments. According to seismic data (extracted from another article in this special issue), the HMB comprises several sedimentary units deposited since the last glacial maximum. Based on analytical results on rare earth elements, fine-grained sediments in all sedimentary units can be interpreted as mixtures of sediments discharged from Chinese and Korean rivers. The proportions of fine-grained sediments from Chinese rivers (74.5 to 80.0%) were constant and higher than those from Korean rivers in all units. This fact demonstrates that all units have the same fine-grained sediment provenance: units III-b and III-a, located in the middle and northern parts of the HMB and directly deposited from Chinese rivers during the sea-level lowstand, could be the sediment source for units II-b and II-a. Unit I, while ambiguous, is of mixed origin combining reworked sediments from nearby mud deposits and Changjiang River-borne material with those of the Keum River. The results of this study indicate that at least 18.6% of bulk sediments in the HMB clearly originate from Chinese rivers, despite its location close to the southwestern coast of Korea.

Sedimentary record on the Indian Summer Monsoon since the Last Glacial Maximum: Evidence from the southeastern Andaman Sea

NASA Astrophysics Data System (ADS)

Shi, Xuefa; Liu, Shengfa; Cao, Peng; Khokiattiwong, Somkiat; Kornkanitnan, Narumol

2016-04-01

The Indian Summer Monsoon (ISM) generated by across-equatorial pressure gradient between the Asian continent and the southern Indian Ocean is a major component of the Asian monsoon system and establishes interactions among the ocean, land and atmosphere. Provenance and paleoclimate changes in the Andaman Sea during the last 26 ka were reconstructed from high-resolution records of grain-size, major elements and Sr-Nd isotopes in core ADM-9. The values of ɛNd(0) and 87Sr/86Sr were in good agreement with those of Irrawaddy River sediments, indicating a common source of origin. Two sensitive grain-size intervals (3.4-7.5 and 16.8-21.2 μm) were identified; the former was controlled primarily by sea-level change, whereas the latter was related to Irrawaddy River discharge and South-west Current transport driven by the ISM. Proxies of chemical weathering (K/Al) and terrigenous input (Ti/Ca) coupled with sensitive grain-size interval (16.8-21.2 μm population) revealed that the ISM was weak during ~15-26 ka BP and then strengthened gradually to a maximum during ~7-9 ka BP; subsequently, the ISM exhibited a generally declining trend to ~2 ka BP. The variation of the ISM recorded in this work is consistent with ISM variations observed in an open area in the northern Indian Ocean and in adjacent continents, implying the evolution of the Asia summer monsoon since 26 ka.

Retrieval of the thickness of undeformed sea ice from simulated C-band compact polarimetric SAR images

NASA Astrophysics Data System (ADS)

Zhang, Xi; Dierking, Wolfgang; Zhang, Jie; Meng, Junmin; Lang, Haitao

2016-07-01

In this paper we introduce a parameter for the retrieval of the thickness of undeformed first-year sea ice that is specifically adapted to compact polarimetric (CP) synthetic aperture radar (SAR) images. The parameter is denoted as the "CP ratio". In model simulations we investigated the sensitivity of the CP ratio to the dielectric constant, ice thickness, ice surface roughness, and radar incidence angle. From the results of the simulations we deduced optimal sea ice conditions and radar incidence angles for the ice thickness retrieval. C-band SAR data acquired over the Labrador Sea in circular transmit and linear receive (CTLR) mode were generated from RADARSAT-2 quad-polarization images. In comparison with results from helicopter-borne measurements, we tested different empirical equations for the retrieval of ice thickness. An exponential fit between the CP ratio and ice thickness provides the most reliable results. Based on a validation using other compact polarimetric SAR images from the same region, we found a root mean square (rms) error of 8 cm and a maximum correlation coefficient of 0.94 for the retrieval procedure when applying it to level ice between 0.1 and 0.8 m thick.

Navigation, Guidance and Control For the CICADA Expendable Micro Air Vehicle

DTIC Science & Technology

2015-01-01

aircraft, as shown in Figure 5a. A Tempest UAV mothership was used as the host platform for the CICADA vehicles. Figure 5b shows how two CICADAs were...mounted on wing pylon drop mechanisms located on each wing of the Tempest . The Tempest was needed to carry the CICADAs back within range of the recovery...carried the Tempest and CICADA combination to a maximum altitude of 57,000 feet above sea-level. At that point, Tempest was released from the balloon and

Freshwater exchanges and surface salinity in the Colombian basin, Caribbean Sea.

PubMed

Beier, Emilio; Bernal, Gladys; Ruiz-Ochoa, Mauricio; Barton, Eric Desmond

2017-01-01

Despite the heavy regional rainfall and considerable discharge of many rivers into the Colombian Basin, there have been few detailed studies about the dilution of Caribbean Surface Water and the variability of salinity in the southwestern Caribbean. An analysis of the precipitation, evaporation and runoff in relation to the climate variability demonstrates that although the salt balance in the Colombian Basin overall is in equilibrium, the area south of 12°N is an important dilution sub-basin. In the southwest of the basin, in the region of the Panama-Colombia Gyre, Caribbean Sea Water is diluted by precipitation and runoff year round, while in the northeast, off La Guajira, its salinity increases from December to May by upwelling. At the interannual scale, continental runoff is related to El Niño Southern Oscillation, and precipitation and evaporation south of 12°N are related to the Caribbean Low Level Jet. During El Niño years the maximum salinification occurs in the dry season (December-February) while in La Niña years the maximum dilution (or freshening), reaching La Guajira Coastal Zone, occurs in the wet season (September-November).

Freshwater exchanges and surface salinity in the Colombian basin, Caribbean Sea

PubMed Central

2017-01-01

Despite the heavy regional rainfall and considerable discharge of many rivers into the Colombian Basin, there have been few detailed studies about the dilution of Caribbean Surface Water and the variability of salinity in the southwestern Caribbean. An analysis of the precipitation, evaporation and runoff in relation to the climate variability demonstrates that although the salt balance in the Colombian Basin overall is in equilibrium, the area south of 12°N is an important dilution sub-basin. In the southwest of the basin, in the region of the Panama-Colombia Gyre, Caribbean Sea Water is diluted by precipitation and runoff year round, while in the northeast, off La Guajira, its salinity increases from December to May by upwelling. At the interannual scale, continental runoff is related to El Niño Southern Oscillation, and precipitation and evaporation south of 12°N are related to the Caribbean Low Level Jet. During El Niño years the maximum salinification occurs in the dry season (December-February) while in La Niña years the maximum dilution (or freshening), reaching La Guajira Coastal Zone, occurs in the wet season (September-November). PMID:28777801

Cyanobacteria toxins in the Salton Sea.

PubMed

Carmichael, Wayne W; Li, RenHui

2006-04-19

The Salton Sea (SS) is the largest inland body of water in California: surface area 980 km2, volume 7.3 million acre-feet, 58 km long, 14-22 km wide, maximum depth 15 m. Located in the southeastern Sonoran desert of California, it is 85 m below sea level at its lowest point. It was formed between 1905 and 1907 from heavy river flows of the Colorado River. Since its formation, it has attracted both people and wildlife, including flocks of migratory birds that have made the Salton Sea a critical stopover on the Pacific flyway. Over the past 15 years wintering populations of eared grebe (Podiceps nigricollis) at the Salton Sea, have experienced over 200,000 mortalities. The cause of these large die-offs remains unknown. The unique environmental conditions of the Salton Sea, including salinities from brackish freshwater at river inlets to hypersaline conditions, extreme daily summer temperatures (>38 degrees C), and high nutrient loading from rivers and agricultural drainage favor eutrophic conditions that encourage algal blooms throughout the year. A significant component of these algal blooms are the prokaryotic group - the Cyanophyta or blue-green algae (also called Cyanobacteria). Since many Cyanobacteria produce toxins (the cyanotoxins) it became important to evaluate their presence and to determine if they are a contributing factor in eared-grebe mortalities at the Salton Sea. From November 1999 to April 2001, 247 water and sediment samples were received for phytoplankton identification and cyanotoxin analyses. Immunoassay (ELISA) screening of these samples found that eighty five percent of all water samples contained low but detectable levels of the potent cyclic peptide liver toxin called microcystins. Isolation and identification of cyanobacteria isolates showed that the picoplanktonic Synechococcus and the benthic filamentous Oscillatoria were dominant. Both organisms were found to produce microcystins dominated by microcystin-LR and YR. A laboratory strain of Synechococcus was identified by PCR as being closest to known marine forms of this genus. Analyses of affected grebe livers found microcystins at levels that may account for some of the acute mortalities. The production of microcystins by a marine Synechococcus indicates that microcystins may be a more common occurrence in marine environments - a finding not recognized before this work. Further research should be done to define the distribution of microcystin producing marine cyanobacteria and to determine exposure/response effects of microcystins and possibly other cyanotoxins in the Salton Sea. Future efforts to reduce avian mortalities and remediate the Salton Sea should evaluate vectors by which microcystins enter avian species and ways to control and mitigate toxic cyanobacteria waterblooms at the Salton Sea.

Suspended sediment projections in Apalachicola Bay in response to altered river flow and sediment loads under climate change and sea level rise

NASA Astrophysics Data System (ADS)

Huang, Wenrui; Hagen, Scott C.; Wang, Dingbao; Hovenga, Paige A.; Teng, Fei; Weishampel, John F.

2016-10-01

Suspended sediments, or total suspended solids (TSS), are an important factor for oyster habitat. While high concentrations of suspended sediments can cause a reduction of oyster density, some level of suspended sediment is required to supply oysters with necessary nutrients. In this study, characteristics of TSS variations in response to sea level rise (SLR) at two oyster reefs in Apalachicola Bay are investigated by coupled estuarine hydrodynamic and sediment transport modeling. A storm event in 1993 and a year-long period in 2010 under recent sea level conditions are selected as the baseline conditions. Scenarios of river flow and sediment loads under SLR and climate change are obtained by downscaled global climate modeling. Compared to the baseline conditions, simulations of TSS indicate that predicted SLR yields a substantial decrease in TSS near the two oyster reefs. However, TSS levels differed at the two study locations. TSS changes by SLR revealed minimal impact on oyster habitat at the Dry Bar site (to the west of the mouth of the Apalachicola River) but are projected to have a significant impact at the Cat Point site (to the east of the Apalachicola River). At Cat Point, because SLR causes the increase of salt water intrusion from the Gulf through a large tidal inlet (East Pass), maximum sediment concentration is near zero for 0.2-m SLR and equal to zero for 0.5- and 1.2-m SLR. Therefore, SLR may result in a substantial loss of nutrients from suspended sediment in the oyster reef at Cat Point.

The Impacts of 3-D Earth Structure on GIA-Induced Crustal Deformation and Future Sea-Level Change in the Antarctic

NASA Astrophysics Data System (ADS)

Powell, E. M.; Hay, C.; Latychev, K.; Gomez, N. A.; Mitrovica, J. X.

2016-12-01

Glacial Isostatic Adjustment (GIA) models used to constrain the extent of past ice sheets and viscoelastic Earth structure, or to correct geodetic and geological observables for ice age effects, generally only consider depth-dependent variations in Earth viscosity and lithospheric structure. A et al. [2013] argued that 3-D Earth structure could impact GIA observables in Antarctica, but concluded that the presence of such structure contributes less to GIA uncertainty than do differences in Antarctic deglaciation histories. New seismic and geological evidence, however, indicates the Antarctic is underlain by complex, high amplitude variability in viscoelastic structure, including a low viscosity zone (LVZ) under West Antarctica. Hay et al. [2016] showed that sea-level fingerprints of modern melting calculated using such Earth models differ from those based on elastic or 1-D viscoelastic Earth models within decades of melting. Our investigation is motivated by two questions: (1) How does 3-D Earth structure, especially this LVZ, impact observations of GIA-induced crustal deformation associated with the last deglaciation? (2) How will 3-D Earth structure affect predictions of future sea-level rise in Antarctica? We compute the gravitationally self-consistent sea level, uplift, and gravity changes using the finite volume treatment of Latychev et al. [2005]. We consider four viscoelastic Earth models: a global 1-D model; a regional, West Antarctic-like 1-D model; a 3-D model where the lithospheric thickness varies laterally; and a 3-D model where both viscosity and lithospheric thickness vary laterally. For our Last Glacial Maximum to present investigations we employ ICE6g [Peltier et al., 2015]. For our present-future investigations we consider a melt scenario consistent with GRACE satellite gravity derived solutions [Harig et al., 2015]. Our calculations indicate that predictions of crustal deformations due to both GIA and ongoing melting are strongly influenced by 3-D lithospheric thickness and viscosity structure. Future sea level change due to ongoing melting is primarily influenced by 3-D viscosity structure. We show that 1-D Earth models built using regional inferences of viscosity and lithospheric thickness do not accurately capture the variability introduced by 3-D Earth structure.

The Impacts of 3-D Earth Structure on GIA-Induced Crustal Deformation and Future Sea-Level Change in the Antarctic

NASA Astrophysics Data System (ADS)

Powell, E. M.; Hay, C.; Latychev, K.; Gomez, N. A.; Mitrovica, J. X.

2017-12-01

Glacial Isostatic Adjustment (GIA) models used to constrain the extent of past ice sheets and viscoelastic Earth structure, or to correct geodetic and geological observables for ice age effects, generally only consider depth-dependent variations in Earth viscosity and lithospheric structure. A et al. [2013] argued that 3-D Earth structure could impact GIA observables in Antarctica, but concluded that the presence of such structure contributes less to GIA uncertainty than do differences in Antarctic deglaciation histories. New seismic and geological evidence, however, indicates the Antarctic is underlain by complex, high amplitude variability in viscoelastic structure, including a low viscosity zone (LVZ) under West Antarctica. Hay et al. [2016] showed that sea-level fingerprints of modern melting calculated using such Earth models differ from those based on elastic or 1-D viscoelastic Earth models within decades of melting. Our investigation is motivated by two questions: (1) How does 3-D Earth structure, especially this LVZ, impact observations of GIA-induced crustal deformation associated with the last deglaciation? (2) How will 3-D Earth structure affect predictions of future sea-level rise in Antarctica? We compute the gravitationally self-consistent sea level, uplift, and gravity changes using the finite volume treatment of Latychev et al. [2005]. We consider four viscoelastic Earth models: a global 1-D model; a regional, West Antarctic-like 1-D model; a 3-D model where the lithospheric thickness varies laterally; and a 3-D model where both viscosity and lithospheric thickness vary laterally. For our Last Glacial Maximum to present investigations we employ ICE6g [Peltier et al., 2015]. For our present-future investigations we consider a melt scenario consistent with GRACE satellite gravity derived solutions [Harig et al., 2015]. Our calculations indicate that predictions of crustal deformations due to both GIA and ongoing melting are strongly influenced by 3-D lithospheric thickness and viscosity structure. Future sea level change due to ongoing melting is primarily influenced by 3-D viscosity structure. We show that 1-D Earth models built using regional inferences of viscosity and lithospheric thickness do not accurately capture the variability introduced by 3-D Earth structure.

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.

Observations of internal waves in the Gulf of California by SEASAT SAR

NASA Technical Reports Server (NTRS)

Fu, L. L.; Holt, B.

1983-01-01

Internal waves which are among the most commonly observed oceanic phenomena in the SEASAT SAR imagery are discussed. These waves are associated with the vertical displacements of constant water density surfaces in the ocean. Their amplitudes are maximum at depths where the water density changes most rapidly usually at depths from 50 to 100 m, whereas the horizontal currents associated with these waves are maximum at the sea surface where the resulting oscillatory currents modulate the sea surface roughness and produce the signatures detected by SAR.

Observations of internal waves in the Gulf of California by SEASAT SAR

NASA Astrophysics Data System (ADS)

Fu, L. L.; Holt, B.

1983-07-01

Internal waves which are among the most commonly observed oceanic phenomena in the SEASAT SAR imagery are discussed. These waves are associated with the vertical displacements of constant water density surfaces in the ocean. Their amplitudes are maximum at depths where the water density changes most rapidly usually at depths from 50 to 100 m, whereas the horizontal currents associated with these waves are maximum at the sea surface where the resulting oscillatory currents modulate the sea surface roughness and produce the signatures detected by SAR.

Diversity patterns in the terrestrial avifauna of the Salton sea

Treesearch

Mark B. Mendelsohn; William I. Boarman; Robert N. Fisher

2005-01-01

We performed bird point counts monthly March-June 2001 and bi-monthly August 2001-February 2002 across a sampling grid of 35 points along the west edge of Salton Sea. We found that landbird species diversity (both in numbers of species, and numbers per species) was dependent on proximity to the sea. Diversity was at a maximum nearest the shore, and was significantly...

Stratigraphy, climate and downhole logging data - an example from the ICDP Dead Sea deep drilling project

NASA Astrophysics Data System (ADS)

Coianiz, Lisa; Ben-Avraham, Zvi; Lazar, Michael

2017-04-01

During the late Quaternary a series of lakes occupied the Dead Sea tectonic basin. The sediments that accumulated within these lakes preserved the environmental history (tectonic and climatic) of the basin and its vicinity. Most of the information on these lakes was deduced from exposures along the marginal terraces of the modern Dead Sea, e.g. the exposures of the last glacial Lake Lisan and Holocene Dead Sea. The International Continental Drilling Program (ICDP) project conducted in the Dead Sea during 2010-2011 recovered several cores that were drilled in the deep depocenter of the lake (water depth of 300 m) and at the margin (depth of 3 m offshore Ein Gedi spa). New high resolution logging data combined with a detailed lithological description and published age models for the deep 5017-1-A borehole were used to establish a sequence stratigraphic framework for the Lakes Amora, Samra, Lisan and Zeelim strata. This study presents a stratigraphic timescale for reconstructing the last ca 225 ka. It provides a context within which the timing of key sequence surfaces identified in the distal part of the basin can be mapped on a regional and stratigraphic time frame. In addition, it permitted the examination of depositional system tracts and related driving mechanisms controlling their formation. The sequence stratigraphic model developed for the Northern Dead Sea Basin is based on the identification of sequence bounding surfaces including: sequence boundary (SB), transgressive surface (TS) and maximum flooding surface (MFS). They enabled the division of depositional sequences into a Lowstand systems tracts (LST), Transgressive systems tracts (TST) and Highstand systems tracts (HST), which can be interpreted in terms of relative lake level changes. The analysis presented here show that system tract stacking patterns defined for the distal 5017-1-A borehole can be correlated to the proximal part of the basin, and widely support the claim that changes in relative lake levels were synchronous across the northern Dead Sea, although differences do exist. These discrepancies can possibly be explained in part by the tectonic nature of the basin. Within the 5017-1-A section, the interpreted changes in depositional environments derived primarily from the gamma ray log patterns show a good correlation in time with sequence-chronostratigraphic framework, extracted lake level curves and paleohydrological records of other areas worldwide. Sequence stratigraphic analysis presented here allows for a detailed, high resolution examination of the sedimentary sequences in the Northern Dead Sea Basin together with an independent proxy that is an indirect indicator of changes in relative lake level.

Calculated maximum Hl ground-level concentrations downwind from launch pad aborts of the space shuttle and Titan 3 C vehicles at Kennedy Space Center

NASA Technical Reports Server (NTRS)

Dumbauld, R. K.; Bjorklund, J. R.

1972-01-01

A quantitative assessment is described of the potential environmental hazard posed by the atmospheric release of HCl resulting from the burning of solid propellant during two hypothetical on-pad aborts of the Titan 3 C and space shuttle vehicles at Kennedy Space Center. In one pad-abort situation, it is assumed that the cases of the two solid-propellant engines are ruptured and the burning propellant falls to the ground in the immediate vicinity of the launch pad where it continues to burn for 5 minutes. In the other pad-abort situation considered, one of the two solid engines on each vehicle is assumed to ignite and burn at the normal rate while the vehicle remains on the launch pad. Calculations of maximum HCl ground-level concentration for the above on-pad abort situations were made using the computerized NASA/MSFC multilayer diffusion models in conjunction with appropriate meteorological and source inputs. Three meteorological regimes are considered-fall, spring, and afternoon sea-breeze. Source inputs for the hazard calculations were developed. The principal result of the calculations is that maximum ground-level HCl concentrations at distances greater than 1 kilometer from the launch pad are less than 3 parts per million in all cases considered.

Eddy energy sources and mesoscale eddies in the Sea of Okhotsk

NASA Astrophysics Data System (ADS)

Stepanov, Dmitry V.; Diansky, Nikolay A.; Fomin, Vladimir V.

2018-05-01

Based on eddy-permitting ocean circulation model outputs, the mesoscale variability is studied in the Sea of Okhotsk. We confirmed that the simulated circulation reproduces the main features of the general circulation in the Sea of Okhotsk. In particular, it reproduced a complex structure of the East-Sakhalin current and the pronounced seasonal variability of this current. We established that the maximum of mean kinetic energy was associated with the East-Sakhalin Current. In order to uncover causes and mechanisms of the mesoscale variability, we studied the budget of eddy kinetic energy (EKE) in the Sea of Okhotsk. Spatial distribution of the EKE showed that intensive mesoscale variability occurs along the western boundary of the Sea of Okhotsk, where the East-Sakhalin Current extends. We revealed a pronounced seasonal variability of EKE with its maximum intensity in winter and its minimum intensity in summer. Analysis of EKE sources and rates of energy conversion revealed a leading role of time-varying (turbulent) wind stress in the generation of mesoscale variability along the western boundary of the Sea of Okhotsk in winter and spring. We established that a contribution of baroclinic instability predominates over that of barotropic instability in the generation of mesoscale variability along the western boundary of the Sea of Okhotsk. To demonstrate the mechanism of baroclinic instability, the simulated circulation was considered along the western boundary of the Sea of Okhotsk from January to April 2005. In April, the mesoscale anticyclonic eddies are observed along the western boundary of the Sea of Okhotsk. The role of the sea ice cover in the intensification of the mesoscale variability in the Sea of Okhotsk was discussed.

Variability of Arctic Sea Ice as Determined from Satellite Observations

NASA Technical Reports Server (NTRS)

Parkinson, Claire L.

1999-01-01

The compiled, quality-controlled satellite multichannel passive-microwave record of polar sea ice now spans over 18 years, from November 1978 through December 1996, and is revealing considerable information about the Arctic sea ice cover and its variability. The information includes data on ice concentrations (percent areal coverages of ice), ice extents, ice melt, ice velocities, the seasonal cycle of the ice, the interannual variability of the ice, the frequency of ice coverage, and the length of the sea ice season. The data reveal marked regional and interannual variabilities, as well as some statistically significant trends. For the north polar ice cover as a whole, maximum ice extents varied over a range of 14,700,000 - 15,900,000 sq km, while individual regions experienced much greater percent variations, for instance, with the Greenland Sea having a range of 740,000 - 1,110,000 sq km in its yearly maximum ice coverage. In spite of the large variations from year to year and region to region, overall the Arctic ice extents showed a statistically significant, 2.80% / decade negative trend over the 18.2-year period. Ice season lengths, which vary from only a few weeks near the ice margins to the full year in the large region of perennial ice coverage, also experienced interannual variability, along with spatially coherent overall trends. Linear least squares trends show the sea ice season to have lengthened in much of the Bering Sea, Baffin Bay, the Davis Strait, and the Labrador Sea, but to have shortened over a much larger area, including the Sea of Okhotsk, the Greenland Sea, the Barents Sea, and the southeastern Arctic.

Post-glacial variability of sea ice cover, river run-off and biological production in the western Laptev Sea (Arctic Ocean) - A high-resolution biomarker study

NASA Astrophysics Data System (ADS)

Hörner, T.; Stein, R.; Fahl, K.; Birgel, D.

2016-07-01

Multi-proxy biomarker measurements were applied on two sediment cores (PS51/154, PS51/159) to reconstruct sea ice cover (IP25), biological production (brassicasterol, dinosterol) and river run-off (campesterol, β-sitosterol) in the western Laptev Sea over the last ∼17 ka with unprecedented temporal resolution. The absence of IP25 from 17.2 to 15.5 ka, in combination with minimum concentration of phytoplankton biomarkers, suggests that the western Laptev Sea shelf was mostly covered with permanent sea ice. Very minor river run-off and restricted biological production occurred during this cold interval. From ∼16 ka until 7.5 ka, a long-term decrease of terrigenous (riverine) organic matter and a coeval increase of marine organic matter reflect the gradual establishment of fully marine conditions in the western Laptev Sea, caused by the onset of the post-glacial transgression. Intensified river run-off and reduced sea ice cover characterized the time interval between 15.2 and 12.9 ka, including the Bølling/Allerød warm period (14.7-12.9 ka). Prominent peaks of the DIP25 Index coinciding with maximum abundances of subpolar foraminifers, are interpreted as pulses of Atlantic water inflow on the western Laptev Sea shelf. After the warm period, a sudden return to severe sea ice conditions with strongest ice-coverage between 11.9 and 11 ka coincided with the Younger Dryas (12.9-11.6 ka). At the onset of the Younger Dryas, a distinct alteration of the ecosystem (reflected in a distinct drop in terrigenous and phytoplankton biomarkers) was detected. During the last 7 ka, the sea ice proxies reflect a cooling of the Laptev Sea spring/summer season. This cooling trend was superimposed by a short-term variability in sea ice coverage, probably representing Bond cycles (1500 ± 500 ka) that are related to solar activity changes. Hence, atmospheric circulation changes were apparently able to affect the sea ice conditions on the Laptev Sea shelf under modern sea level conditions.

Contrasting Holocene sedimentary geologies of lower Daly River, northern Australia, and lower Sepik-Ramu, Papua New Guinea

NASA Astrophysics Data System (ADS)

Chappell, John

1993-03-01

The estuarine plain of the macrotidal Daly River, in monsoonal northern Australia, is underlain by extensive mid-Holocene mangrove swamp sediments which accumulated during the last stages of Post-glacial sea-level rise. Sediment yield from the catchment is too low to account for the volume which accumulated during sea-level rise, and onshore transport is invoked. This is supported by radiocarbon ages and facies analysis of the transgressive sediment tract beneath the maximum flooding surface (MFS), and of the tract of vertical sedimentation which extends from the MFS to the surface of estuarine/fluvial transition (the EFT). The EFT occurred about 5000 to 6000 BP throughout the estuarine plain. A contrasting situation exists in the lowland Holocene basin of the microtidal Sepik and Ramu rivers in Papua New Guinea, which derive sediment from highly tectonic catchments. A tectonic basin, which was a shallow brackish inland sea after Post-glacial transgression, is separated by a low divide from a deltaic plain. Progradation of the deltaic plain commenced about 3500 BP after regressive sedimentation eclipsed the inland sea in the tectonic basin. Contrasting organic facies, mangrove in the Daly and freshwater swamp deposits in the Sepik-Ramu, highlight differences between facies models of the two systems. Differences between fluvio-tidal regimes are reflected by the EFT, which is synchronous in the Daly and diachronous in the Sepik-Ramu, and possibly by the MFS which is diachronous in the Daly and may be synchronous in the Sepik-Ramu.

On using scatterometer and altimeter data to improve storm surge forecasting in the Adriatic Sea

NASA Astrophysics Data System (ADS)

Bajo, Marco; Umgiesser, Georg; De Biasio, Francesco; Vignudelli, Stefano; Zecchetto, Stefano

2017-04-01

Satellite data are seldom used in storm surge forecasting. Among the most important issues related to the storm surge forecasting are the quality of the model wind forcing and the initial condition of the sea surface elevation. In this work, focused on storm surge forecasting in the Adriatic Sea, satellite scatterometer wind data are used to correct the wind speed and direction biases of the ECMWF global atmospheric model by tuning the spatial fields, as an alternative to data assimilation. The capability of such an unbiased wind is tested against that of a high resolution wind, produced by a regional non-hydrostatic model. On the other hand, altimeter Total Water Level Envelope (TWLE) data, which provide the sea level elevation, are used to improve the accuracy of the initial state of the model simulations. This is done by assimilating into a storm surge model the TWLE obtained by the altimeter observations along ground tracks, after subtraction of the tidal components. In order to test the methodology, eleven storm surge events recorded in Venice, from 2008 to 2012, have been simulated using different configurations of forcing wind and altimeter data assimilation. Results show that the relative error on the estimation of the maximum surge peak, averaged over the cases considered, decreases from 13% to 7% using both the unbiased wind and the altimeter data assimilation, while forcing the hydrodynamic model with the high resolution wind (no tuning), the altimeter data assimilation reduces the error from 9% to 6%.

Sundaland Peat Carbon Dynamics and Its Contribution to the Holocene Atmospheric CO2 Concentration

NASA Astrophysics Data System (ADS)

Abrams, Jesse F.; Hohn, Sönke; Rixen, Tim; Merico, Agostino

2018-04-01

The Sunda Shelf is a large submerged extension of the continental shelf of mainland Asia, joining the islands of Borneo, Java, and Sumatra and forming the shallow seabed of the South China Sea. Recent studies identified present-day peatlands in Southeast Asia as a globally important carbon reservoir. However, little is known about Sundaland paleopeatlands and their role in the global carbon cycle since the Last Glacial Maximum. Using a topography-based, sea level-driven model, we estimate the potential spatial extent of peatlands during the late Pleistocene and early Holocene across the low-lying Sundaland plains. We then use the estimated peatland area together with data on carbon accumulation rates to calculate the total peat carbon pool on the Sunda Shelf. Finally, using a global biogeochemical model, we analyze the relative influence of the predicted Sundaland peat dynamics and other carbon change mechanisms, specifically high-latitude forest growth and peat formation, shallow sea carbonate deposition, ocean warming, and combinations of them, on the global carbon cycle of the Holocene. We identify a feedback mechanism between sea level and peatland carbon sequestration in Sundaland that reduced atmospheric CO2 concentration by about 4-5 ppm and increased δ13C by 0.05‰ during the Holocene. We also show that a concurrence of mechanisms that includes Sundaland peat dynamics produces model results that are consistent with proxy records, especially with respect to δ13C.

The ICE-6G_C (VM5a) Global Model of the GIA Process: Antarctica at High Spatial Resolution

NASA Astrophysics Data System (ADS)

Peltier, W. R.; Drummond, R.; Argus, D. F.

2016-12-01

The ICE-6G_C (VM5a) global model of the glacial isostatic adjustment process (Argus et al., 2014 GJI 198, 537-563; Peltier et al. , 2015, JGR 119, doi:10.1002/2014JB011176) is the latest model in the ICE-nG (VMx) sequence. The model continues to be unique in that it is the only model whose properties are made freely available at each iterative step in its development. This latest version, which embodies detailed descriptions of the Laurentide , Fennoscandian/Barents Sea, Greenland and Antarctic ice sheets through the most recent glacial cycle, is a refinement based primarily upon the incorporation of the constraints being provided by GPS measurements of the vertical and horizontal motion of the crust as well as GRACE observations of the time dependent gravity field. The model has been shown to provide exceptionally accurate predictions of these space geodetic observations of the response to the most recent Late Quaternary glacial cycle. Particular attention has been paid to the Antarctic component as it is well known on the basis of analyses of the sedimentary stratigraphy off-shore and geomorphological characteristics of the continental shelf, that the Last Glacial Maximum state of the southern continent was one in which grounded ice extended out to the shelf break in most locations, including significant fractions of the Ross Sea and Weddell Sea embayments. In the latter regions especially, it is expected that grounded ice would have existed below sea level. In ICE-6G_C (VM5a) a grounding line tracking algorithm was employed (Stuhne and Peltier, 2015 JGR 120, 1841-1865) in order to describe the unloading of the solid surface by ice that was initially grounded below sea level, an apparently unique characteristic of this model. In the initially published version, in which the Sea Level Equation (SLE) was inverted on a basis of spherical harmonics truncated at degree and order 256, this led to "ringing" in the embayments when the Stokes coefficients of the model were employed to infer vertical crustal motion. Otherwise this modest level of resolution proved entirely adequate to represent both relative sea level history and modern crustal motion. We demonstrate that there is no issue with this reconstruction by simply increasing the resolution of the SLE inversion and describe the details of its predictions for both hemispheres.

Assessing Climate Variability Effects on Dengue Incidence in San Juan, Puerto Rico

PubMed Central

Méndez-Lázaro, Pablo; Muller-Karger, Frank E.; Otis, Daniel; McCarthy, Matthew J.; Peña-Orellana, Marisol

2014-01-01

We test the hypothesis that climate and environmental conditions are becoming favorable for dengue transmission in San Juan, Puerto Rico. Sea Level Pressure (SLP), Mean Sea Level (MSL), Wind, Sea Surface Temperature (SST), Air Surface Temperature (AST), Rainfall, and confirmed dengue cases were analyzed. We evaluated the dengue incidence and environmental data with Principal Component Analysis, Pearson correlation coefficient, Mann-Kendall trend test and logistic regressions. Results indicated that dry days are increasing and wet days are decreasing. MSL is increasing, posing higher risk of dengue as the perimeter of the San Juan Bay estuary expands and shorelines move inland. Warming is evident with both SST and AST. Maximum and minimum air surface temperature extremes have increased. Between 1992 and 2011, dengue transmission increased by a factor of 3.4 (95% CI: 1.9–6.1) for each 1 °C increase in SST. For the period 2007–2011 alone, dengue incidence reached a factor of 5.2 (95% CI: 1.9–13.9) for each 1 °C increase in SST. Teenagers are consistently the age group that suffers the most infections in San Juan. Results help understand possible impacts of different climate change scenarios in planning for social adaptation and public health interventions. PMID:25216253

Amplitude calibration of an acoustic backscattered signal from a bottom-moored ADCP based on long-term measurement series

NASA Astrophysics Data System (ADS)

Piotukh, V. B.; Zatsepin, A. G.; Kuklev, S. B.

2017-05-01

A possible approach to, and preliminary results of, amplitude calibration of acoustic signals backscattered from an ADCP moored at the bottom of the near-shelf zone of the Black Sea is considered. The aim of this work is to obtain vertical profiles of acoustic scattering signal levels, showing the real characteristics of the volume content of suspended sediments in sea water in units of conventional acoustic turbidity for a given signal frequency. In this case, the assumption about the intervals of maximum acoustic transparency and vertical homogeneity of the marine environment in long-term series of ADCP measurements is used. According to this hypothesis, the intervals of the least values of acoustic backscattered signals are detected, an empirical transfer function of the ADCP reception path is constructed, and it is calibrated. Normalized sets of acoustic backscattered signals relative to a signal from a level of conventionally clear water are obtained. New features in the behavior of vertical profiles of an acoustic echo-signal are revealed due to the calibration. The results of this work will be used in subsequent analysis of the vertical and time variations in suspended sediment content in the near-shelf zone of the Black Sea.

A baseline study of metals in herring (Clupea harengus) from the Norwegian Sea, with focus on mercury, cadmium, arsenic and lead.

PubMed

Frantzen, Sylvia; Maage, Amund; Duinker, Arne; Julshamn, Kaare; Iversen, Svein A

2015-05-01

The Norwegian spring spawning (NSS) herring is an ecologically and economically important fish population in the Norwegian Sea. It was the first of several Norwegian fish stocks subject to a baseline study designed to give a comprehensive account of the levels of contaminants in a fish species from most of its area of distribution and during different seasons. During 2006 and 2007, 800 individual herring were sampled in their feeding areas in the Norwegian Sea in spring and autumn and at their spawning grounds off the coast of Norway during late winter. Metals including Hg, Cd, As and Pb were determined in muscle samples of individual herring, and mean concentrations±sd (mg kg(-1) ww) were: Hg: 0.04±0.03, Cd: 0.010±0.006, As: 2.2±0.6 and Pb: <0.01-0.10. Apart from one sample, no individual herring exceeded the EU's maximum level for any of these elements, as has been seen also in previous monitoring. Hg and Cd concentration increased with increasing fish age and As concentration varied seasonally, possibly due to uptake during feeding (summer), elimination during starvation (winter) and up-concentration during spawning (spring). Copyright © 2015 Elsevier Ltd. All rights reserved.

Tooele Army Depot-North Area Suspected Releases SWMUs. Phase 1 RFI report. Volume 1. Text

DTIC Science & Technology

1993-12-01

Maximum Contaminant Level MSL Mean Sea Level NEPA National Environmental Policy Act OB/OD Open Burning/Open Detonation PAH Polycyclic Aromatic...part of a pre-construction environmental assessment (EA), as required by the National Environmental Policy Act (NEPA). The following summarize the...0 1 1M*C!. 43, IV 𔃺 -4C o c a 0fi MA ao W!t 40 CD at w 4Kb CNCD 0 0 CS 40 - 0 e’A * CL m s.a Sc -~ ~ *b C CL 0 WN0 . 0 - at’ 30. qm 2 5--1 z 44

Storm surges and coastal impacts at Mar del Plata, Argentina

NASA Astrophysics Data System (ADS)

Fiore, Mónica M. E.; D'Onofrio, Enrique E.; Pousa, Jorge L.; Schnack, Enrique J.; Bértola, Germán R.

2009-07-01

Positive storm surges (PSS) lasting for several days can raise the water level producing significant differences between the observed level and the astronomical tide. These storm events can be more severe if they coincide with a high tide or if they bracket several tidal cycles, particularly in the case of the highest astronomical tide. Besides, the abnormal sea-level elevation near the coast can cause the highest waves generated to attack the upper beach. This combination of factors can produce severe erosion, threatening sectors located along the coastline. These effects would be more serious if the storm surge height and duration increase as a result of a climatic change. The Mar del Plata (Argentina) coastline and adjacent areas are exposed to such effects. A statistical characterization of PSS based on their intensity, duration and frequency, including a surge event classification, was performed utilizing tide-gauge records over the period 1956-2005. A storm erosion potential index (SEPI) was calculated from observed levels based on hourly water level measurements. The index was related to beach profile responses to storm events. Also, a return period for extreme SEPI values was calculated. Results show an increase in the average number of positive storm surge events per decade. Considering all the events, the last decade (1996-2005) exhibits an average 7% increase compared to each one of the previous decades. A similar behavior was found for the decadal average of the heights of maximum annual positive storm surges. In this case the average height of the last two decades exceeds that of the previous decades by approximately 8 cm. The decadal average of maximum annual duration of these meteorological events shows an increase of 2 h in the last three decades. A possible explanation of the changes in frequency, height and duration of positive storm surges at Mar del Plata would seem to lie in the relative mean sea-level rise.

The de-correlation of westerly winds and westerly-wind stress over the Southern Ocean during the Last Glacial Maximum

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

Liu, Wei; Lu, Jian; Leung, Lai-Yung R.

2015-02-22

This paper investigates the changes of the Southern Westerly Winds (SWW) and Southern Ocean (SO) upwelling between the Last Glacial Maximum (LGM) and preindustrial (PI) in the PMIP3/CMIP5 simulations, highlighting the role of the Antarctic sea ice in modulating the wind stress effect on the ocean. Particularly, a discrepancy may occur between the changes in SWW and westerly wind stress, caused primarily by an equatorward expansion of winter Antarctic sea ice that undermines the wind stress in driving the liquid ocean. Such discrepancy may reflect the LGM condition in reality, in view of that the model simulates this condition hasmore » most credible simulation of modern SWW and Antarctic sea ice. The effect of wind stress on the SO upwelling is further explored via the wind-induced Ekman pumping, which is reduced under the LGM condition in all models, in part by the sea-ice “capping” effect present in the models.« less

Optimum Sea Surface Displacement and Fault Slip Distribution of the 2017 Tehuantepec Earthquake (Mw 8.2) in Mexico Estimated From Tsunami Waveforms

NASA Astrophysics Data System (ADS)

Gusman, Aditya Riadi; Mulia, Iyan E.; Satake, Kenji

2018-01-01

The 2017 Tehuantepec earthquake (Mw 8.2) was the first great normal fault event ever instrumentally recorded to occur in the Middle America Trench. The earthquake generated a tsunami with an amplitude of 1.8 m (height = 3.5 m) in Puerto Chiapas, Mexico. Tsunami waveforms recorded at coastal tide gauges and offshore buoy stations were used to estimate the optimum sea surface displacement without assuming any fault. Our optimum sea surface displacement model indicated that the maximum uplift of 0.5 m is located near the trench and the maximum subsidence of 0.8 m on the coastal side near the epicenter. We then estimated the fault slip distribution that can best explain the optimum sea surface displacement assuming 10 different fault geometries. The best model suggests that a compact region of large slip (3-6 m) extends from a depth of 30 km to 90 km, centered at a depth of 60 km.

Optimisation of sea surface current retrieval using a maximum cross correlation technique on modelled sea surface temperature

NASA Astrophysics Data System (ADS)

Heuzé, Céline; Eriksson, Leif; Carvajal, Gisela

2017-04-01

Using sea surface temperature from satellite images to retrieve sea surface currents is not a new idea, but so far its operational near-real time implementation has not been possible. Validation studies are too region-specific or uncertain, due to the errors induced by the images themselves. Moreover, the sensitivity of the most common retrieval method, the maximum cross correlation, to the three parameters that have to be set is unknown. Using model outputs instead of satellite images, biases induced by this method are assessed here, for four different seas of Western Europe, and the best of nine settings and eight temporal resolutions are determined. For all regions, tracking a small 5 km pattern from the first image over a large 30 km region around its original location on a second image, separated from the first image by 6 to 9 hours returned the most accurate results. Moreover, for all regions, the problem is not inaccurate results but missing results, where the velocity is too low to be picked by the retrieval. The results are consistent both with limitations caused by ocean surface current dynamics and with the available satellite technology, indicating that automated sea surface current retrieval from sea surface temperature images is feasible now, for search and rescue operations, pollution confinement or even for more energy efficient and comfortable ship navigation.

Reconstruction of Sea/Lake-Level Changes in an Active Strike-Slip Basin (Gulf of Cariaco, NE Venezuela)

NASA Astrophysics Data System (ADS)

van Daele, M.; Audemard, F.; Beck, C.; de Batist, M.; van Welden, A.; Moernaut, J.; 2006 Shipboard Party, G.

2008-05-01

In January 2006, 76 high-resolution reflection seismic profiles were acquired in the Gulf of Cariaco, Northeast Venezuela. In the upper 100 m of sedimentary infill, 17 unconformity-bounded sequences were identified and mapped throughout the basin. Up to now, no core or borehole information is available to provide age constraints on these units. The sedimentary infill is cut by several faults, Riedel faults in the central part and the El Pilar fault (one of the main faults of the South American-Caribbean plate boundary) in the southern part of the gulf. The connection of the Gulf of Cariaco with the adjacent Cariaco Basin occurs at a present-day water depth of ~ 55 m. This implies that the gulf was disconnected from the world ocean and functioned as a lake during a large part of the last glacial. The main rivers entering the gulf drain the coastal mountain ranges and tend to form pronounced deltas at their inlet. During times when the gulf was a lake, periods with a dry climate resulted in dramatic lake-level lowstands and even complete desiccation/evaporation. The present-day depths of delta offlap breaks and the presence of lowstand/evaporite deposits can thus be used to estimate sea/lake level at the time of their formation. Detailed analysis of these stratigraphic sea/lake-level indicators allowed reconstructing the sea/lake-level history for the period encompassed by the 17 identified sequences. This sea/lake-level reconstruction also needed to be corrected for tectonic subsidence, affecting different parts of the gulf with different intensity. The reconstructed sea/lake-level curve of the Gulf of Cariaco was compared with the eustatic sea-level curve and with results of previous paleoclimate studies in Venezuela. The striking coherence between the eustatic curve and the amplitudes and absolute heights of successive reconstructed lowstands and highstands compelled us to tune our record to the eustatic curve in order to achieve a rough age estimate for our units. According to this age model, our seismic stratigraphy reaches back to MIS6, and the average sedimentation rate in the central parts of the gulf since MIS5e is 0.92 mm/y. Our data show that reconstructed lake levels in the Gulf of Cariaco, which represent a proxy for climate in NE- Venezuela, are very strongly coupled to the global stadials and interstadials of the last glacial period. Also the Younger Dryas is recognised in the sedimentary record of the Gulf of Cariaco as lowstand deposit resulting from an (almost) complete desiccation. Our data reveal that the stratigraphy of the Gulf of Cariaco holds a very accurate, complete and promising record of eustasy and climate change, at least since the penultimate glacial maximum. The quality of this record and the vicinity to the iconic Cariaco Basin make the Gulf of Cariaco an ideal target for future ocean drilling (or long coring).

Comprehensive species set revealing the phylogeny and biogeography of Feliformia (Mammalia, Carnivora) based on mitochondrial DNA

PubMed Central

Ma, Jian-Zhang

2017-01-01

Extant Feliformia species are one of the most diverse radiations of Carnivora (~123 species). Despite substantial recent interest in their conservation, diversification, and systematic study, no previous phylogeny contains a comprehensive species set, and no biogeography of this group is available. Here, we present a phylogenetic estimate for Feliformia with a comprehensive species set and establish a historical biogeography based on mitochondrial DNA. Both the Bayesian and maximum likelihood phylogeny for Feliformia are elucidated in our analyses and are strongly consistent with many groups recognized in previous studies. The mitochondrial phylogenetic relationships of Felidae were for the first time successfully reconstructed in our analyses with strong supported. When divergence times and dispersal/vicariance histories were compared with historical sea level changes, four dispersal and six vicariance events were identified. These vicariance events were closely related with global sea level changes. The transgression of sea into the lowland plains between Eurasia and Africa may have caused the vicariance in these regions. A fall in the sea level during late Miocene to Pliocene produced the Bering strait land bridge, which assisted the migration of American Feliformia ancestors from Asia to North America. In contrast with the ‘sweepstakes hypothesis’, our results suggest that the climate cooling during 30–27 Ma assisted Feliformia migration from the African mainland to Madagascar by creating a short-lived ice bridge across the Mozambique Channel. Lineages-through-time plots revealed a large increase in lineages since the Mid-Miocene. During the Mid-Miocene Climatic Optimum, the ecosystems and population of Feliformia rapidly expanded. Subsequent climate cooling catalyzed immigration, speciation, and the extinction of Feliformia. PMID:28358848

Storm-surge flooding on the Yukon-Kuskokwim Delta, Alaska

USGS Publications Warehouse

Terenzi, John; Ely, Craig R.; Jorgenson, M. Torre

2014-01-01

Coastal regions of Alaska are regularly affected by intense storms of ocean origin, the frequency and intensity of which are expected to increase as a result of global climate change. The Yukon-Kuskokwim Delta (YKD), situated in western Alaska on the eastern edge of the Bering Sea, is one of the largest deltaic systems in North America. Its low relief makes it especially susceptible to storm-driven flood tides and increases in sea level. Little information exists on the extent of flooding caused by storm surges in western Alaska and its effects on salinization, shoreline erosion, permafrost thaw, vegetation, wildlife, and the subsistence-based economy. In this paper, we summarize storm flooding events in the Bering Sea region of western Alaska during 1913 – 2011 and map both the extent of inland flooding caused by autumn storms on the central YKD, using Radarsat-1 and MODIS satellite imagery, and the drift lines, using high-resolution IKONOS satellite imagery and field surveys. The largest storm surges occurred in autumn and were associated with high tides and strong (> 65 km hr-1) southwest winds. Maximum inland extent of flooding from storm surges was 30.3 km in 2005, 27.4 km in 2006, and 32.3 km in 2011, with total flood area covering 47.1%, 32.5%, and 39.4% of the 6730 km2 study area, respectively. Peak stages for the 2005 and 2011 storms were 3.1 m and 3.3 m above mean sea level, respectively—almost as high as the 3.5 m amsl elevation estimated for the largest storm observed (in November 1974). Several historically abandoned village sites lie within the area of inundation of the largest flood events. With projected sea level rise, large storms are expected to become more frequent and cover larger areas, with deleterious effects on freshwater ponds, non-saline habitats, permafrost, and landscapes used by nesting birds and local people.

The Pianosa Contourite Depositional System (Northern Tyrrhenian Sea): drift morphology and Plio-Quaternary stratigraphic evolution

NASA Astrophysics Data System (ADS)

Miramontes Garcia, Elda; Cattaneo, Antonio; Jouet, Gwenael; Thereau, Estelle; Thomas, Yannick; Rovere, Marzia; Cauquil, Eric; Trincardi, Fabio

2016-04-01

The Pianosa Contourite Depositional System (CDS) is located in the Corsica Trough (Northern Tyrrhenian Sea), a confined basin dominated by mass transport and contour currents in the eastern flank and by turbidity currents in the western flank. The morphologic and stratigraphic characterisation of the Pianosa CDS is based on multibeam bathymetry, seismic reflection data (multi-channel high resolution mini GI gun, single-channel sparker and CHIRP), sediment cores and ADCP data. The Pianosa CDS is located at shallow to intermediate water depths (170 to 850 m water depth) and is formed under the influence of the Levantine Intermediate Water (LIW). It is 120 km long, has a maximum width of 10 km and is composed of different types of muddy sediment drifts: plastered drift, separated mounded drift, sigmoid drift and multicrested drift. The reduced tectonic activity in the Corsica Trough since the early Pliocene permits to recover a sedimentary record of the contourite depositional system that is only influenced by climate fluctuations. Contourites started to develop in the Middle-Late Pliocene, but their growth was enhanced since the Middle Pleistocene Transition (0.7-0.9 Ma). Although the general circulation of the LIW, flowing northwards in the Corsica Trough, remained active all along the history of the system, contourite drift formation changed, controlled by sediment influx and bottom current velocity. During periods of sea level fall, fast bottom currents often eroded the drift crest in the middle and upper slope. At that time the proximity of the coast to the shelf edge favoured the formation of bioclastic sand deposits winnowed by bottom currents. Higher sediment accumulation of mud in the drifts occurred during periods of fast bottom currents and high sediment availability (i.e. high activity of turbidity currents), coincident with periods of sea level low-stands. Condensed sections were formed during sea level high-stands, when bottom currents were more sluggish and the turbidite system was disconnected, resulting in a lower sediment influx.

Modelling West Antarctic ice sheet growth and collapse through the past five million years.

PubMed

Pollard, David; DeConto, Robert M

2009-03-19

The West Antarctic ice sheet (WAIS), with ice volume equivalent to approximately 5 m of sea level, has long been considered capable of past and future catastrophic collapse. Today, the ice sheet is fringed by vulnerable floating ice shelves that buttress the fast flow of inland ice streams. Grounding lines are several hundred metres below sea level and the bed deepens upstream, raising the prospect of runaway retreat. Projections of future WAIS behaviour have been hampered by limited understanding of past variations and their underlying forcing mechanisms. Its variation since the Last Glacial Maximum is best known, with grounding lines advancing to the continental-shelf edges around approximately 15 kyr ago before retreating to near-modern locations by approximately 3 kyr ago. Prior collapses during the warmth of the early Pliocene epoch and some Pleistocene interglacials have been suggested indirectly from records of sea level and deep-sea-core isotopes, and by the discovery of open-ocean diatoms in subglacial sediments. Until now, however, little direct evidence of such behaviour has been available. Here we use a combined ice sheet/ice shelf model capable of high-resolution nesting with a new treatment of grounding-line dynamics and ice-shelf buttressing to simulate Antarctic ice sheet variations over the past five million years. Modelled WAIS variations range from full glacial extents with grounding lines near the continental shelf break, intermediate states similar to modern, and brief but dramatic retreats, leaving only small, isolated ice caps on West Antarctic islands. Transitions between glacial, intermediate and collapsed states are relatively rapid, taking one to several thousand years. Our simulation is in good agreement with a new sediment record (ANDRILL AND-1B) recovered from the western Ross Sea, indicating a long-term trend from more frequently collapsed to more glaciated states, dominant 40-kyr cyclicity in the Pliocene, and major retreats at marine isotope stage 31 ( approximately 1.07 Myr ago) and other super-interglacials.

Relative sea level and coastal environments in arctic Alaska during Marine Isotope Stage 5

NASA Astrophysics Data System (ADS)

Farquharson, L. M.; Mann, D. H.; Jones, B. M.; Rittenour, T. M.; Grosse, G.; Groves, P.

2015-12-01

Marine Isotope Stage (MIS) 5 was characterized by marked fluctuations in climate, the warmest being MIS 5e (124-119 ka) when relative sea level (RSL) stood 2-10 m higher than today along many coastlines. In northern Alaska, marine deposits now 5-10 m above modern sea level are assigned to this time period and termed the Pelukian transgression (PT). Complicating this interpretation is the possibility that an intra-Stage 5 ice shelf extended along the Alaskan coast, causing isostatic depression along its grounded margins, which caused RSL highs even during periods of low, global RSL. Here we use optically stimulated luminescence (OSL) to date inferred PT deposits on the Beaufort Sea coastal plain. A transition from what we interpret to be lagoonal mud to sandy tidal flat deposits lying ~ 2.75 m asl dates to 113+/-18 ka. Above this, a 5-m thick gravelly barrier beach dates to 95 +/- 20 ka. This beach contains well-preserved marine molluscs, whale vertebrae, and walrus tusks. Pleistocene-aged ice-rich eolian silt (yedoma) blanket the marine deposits and date to 57.6 +/-10.9 ka. Our interpretation of this chronostratigraphy is that RSL was several meters higher than today during MIS 5e, and lagoons or brackish lakes were prevalent. Gravel barrier beaches moved onshore as local RSL rose further after MIS 5e. The error range of the OSL age of the barrier-beach unit spans the remaining four substages of MIS 5; however, the highstand of RSL on this arctic coastline appears to occurr after the warmest part of the last interglacial and appears not to be coeval with the eustatic maximum reached at lower latitudes during MIS 5. One possibility is that RSL along the Beaufort Sea coast was affected by isostatic depression caused by an ice shelf associated with widespread, intra-Stage 5 glaciation that was out of phase with lower latitude glaciation and whose extent and timing remains enigmatic.

Comparison of buried sand ridges and regressive sand ridges on the outer shelf of the East China Sea

NASA Astrophysics Data System (ADS)

Wu, Ziyin; Jin, Xianglong; Zhou, Jieqiong; Zhao, Dineng; Shang, Jihong; Li, Shoujun; Cao, Zhenyi; Liang, Yuyang

2017-06-01

Based on multi-beam echo soundings and high-resolution single-channel seismic profiles, linear sand ridges in U14 and U2 on the East China Sea (ECS) shelf are identified and compared in detail. Linear sand ridges in U14 are buried sand ridges, which are 90 m below the seafloor. It is presumed that these buried sand ridges belong to the transgressive systems tract (TST) formed 320-200 ka ago and that their top interface is the maximal flooding surface (MFS). Linear sand ridges in U2 are regressive sand ridges. It is presumed that these buried sand ridges belong to the TST of the last glacial maximum (LGM) and that their top interface is the MFS of the LGM. Four sub-stage sand ridges of U2 are discerned from the high-resolution single-channel seismic profile and four strikes of regressive sand ridges are distinguished from the submarine topographic map based on the multi-beam echo soundings. These multi-stage and multi-strike linear sand ridges are the response of, and evidence for, the evolution of submarine topography with respect to sea-level fluctuations since the LGM. Although the difference in the age of formation between U14 and U2 is 200 ka and their sequences are 90 m apart, the general strikes of the sand ridges are similar. This indicates that the basic configuration of tidal waves on the ECS shelf has been stable for the last 200 ka. A basic evolutionary model of the strata of the ECS shelf is proposed, in which sea-level change is the controlling factor. During the sea-level change of about 100 ka, five to six strata are developed and the sand ridges develop in the TST. A similar story of the evolution of paleo-topography on the ECS shelf has been repeated during the last 300 ka.

Method to characterize directional changes in Arctic sea ice drift and associated deformation due to synoptic atmospheric variations using Lagrangian dispersion statistics

NASA Astrophysics Data System (ADS)

Lukovich, Jennifer V.; Geiger, Cathleen A.; Barber, David G.

2017-07-01

A framework is developed to assess the directional changes in sea ice drift paths and associated deformation processes in response to atmospheric forcing. The framework is based on Lagrangian statistical analyses leveraging particle dispersion theory which tells us whether ice drift is in a subdiffusive, diffusive, ballistic, or superdiffusive dynamical regime using single-particle (absolute) dispersion statistics. In terms of sea ice deformation, the framework uses two- and three-particle dispersion to characterize along- and across-shear transport as well as differential kinematic parameters. The approach is tested with GPS beacons deployed in triplets on sea ice in the southern Beaufort Sea at varying distances from the coastline in fall of 2009 with eight individual events characterized. One transition in particular follows the sea level pressure (SLP) high on 8 October in 2009 while the sea ice drift was in a superdiffusive dynamic regime. In this case, the dispersion scaling exponent (which is a slope between single-particle absolute dispersion of sea ice drift and elapsed time) changed from superdiffusive (α ˜ 3) to ballistic (α ˜ 2) as the SLP was rounding its maximum pressure value. Following this shift between regimes, there was a loss in synchronicity between sea ice drift and atmospheric motion patterns. While this is only one case study, the outcomes suggest similar studies be conducted on more buoy arrays to test momentum transfer linkages between storms and sea ice responses as a function of dispersion regime states using scaling exponents. The tools and framework developed in this study provide a unique characterization technique to evaluate these states with respect to sea ice processes in general. Application of these techniques can aid ice hazard assessments and weather forecasting in support of marine transportation and indigenous use of near-shore Arctic areas.

Remote Sensing the Phytoplankton Seasonal Succession of the Red Sea

PubMed Central

Brewin, Robert J. W.; Stenchikov, Georgiy; Hoteit, Ibrahim

2013-01-01

The Red Sea holds one of the most diverse marine ecosystems, primarily due to coral reefs. However, knowledge on large-scale phytoplankton dynamics is limited. Analysis of a 10-year high resolution Chlorophyll-a (Chl-a) dataset, along with remotely-sensed sea surface temperature and wind, provided a detailed description of the spatiotemporal seasonal succession of phytoplankton biomass in the Red Sea. Based on MODIS (Moderate-resolution Imaging Spectroradiometer) data, four distinct Red Sea provinces and seasons are suggested, covering the major patterns of surface phytoplankton production. The Red Sea Chl-a depicts a distinct seasonality with maximum concentrations seen during the winter time (attributed to vertical mixing in the north and wind-induced horizontal intrusion of nutrient-rich water in the south), and minimum concentrations during the summer (associated with strong seasonal stratification). The initiation of the seasonal succession occurs in autumn and lasts until early spring. However, weekly Chl-a seasonal succession data revealed that during the month of June, consistent anti-cyclonic eddies transfer nutrients and/or Chl-a to the open waters of the central Red Sea. This phenomenon occurs during the stratified nutrient depleted season, and thus could provide an important source of nutrients to the open waters. Remotely-sensed synoptic observations highlight that Chl-a does not increase regularly from north to south as previously thought. The Northern part of the Central Red Sea province appears to be the most oligotrophic area (opposed to southern and northern domains). This is likely due to the absence of strong mixing, which is apparent at the northern end of the Red Sea, and low nutrient intrusion in comparison with the southern end. Although the Red Sea is considered an oligotrophic sea, sporadic blooms occur that reach mesotrophic levels. The water temperature and the prevailing winds control the nutrient concentrations within the euphotic zone and enable the horizontal transportation of nutrients. PMID:23755161

Fatty acid and stable isotope characteristics of sea ice and pelagic particulate organic matter in the Bering Sea: tools for estimating sea ice algal contribution to Arctic food web production.

PubMed

Wang, Shiway W; Budge, Suzanne M; Gradinger, Rolf R; Iken, Katrin; Wooller, Matthew J

2014-03-01

We determined fatty acid (FA) profiles and carbon stable isotopic composition of individual FAs (δ(13)CFA values) from sea ice particulate organic matter (i-POM) and pelagic POM (p-POM) in the Bering Sea during maximum ice extent, ice melt, and ice-free conditions in 2010. Based on FA biomarkers, differences in relative composition of diatoms, dinoflagellates, and bacteria were inferred for i-POM versus p-POM and for seasonal succession stages in p-POM. Proportions of diatom markers were higher in i-POM (16:4n-1, 6.6-8.7%; 20:5n-3, 19.6-25.9%) than in p-POM (16:4n-1, 1.2-4.0%; 20:5n-3, 5.5-14.0%). The dinoflagellate marker 22:6n-3/20:5n-3 was highest in p-POM. Bacterial FA concentration was higher in the bottom 1 cm of sea ice (14-245 μg L(-1)) than in the water column (0.6-1.7 μg L(-1)). Many i-POM δ(13)C(FA) values were higher (up to ~10‰) than those of p-POM, and i-POM δ(13)C(FA) values increased with day length. The higher i-POM δ(13)C(FA) values are most likely related to the reduced dissolved inorganic carbon (DIC) availability within the semi-closed sea ice brine channel system. Based on a modified Rayleigh equation, the fraction of sea ice DIC fixed in i-POM ranged from 12 to 73%, implying that carbon was not limiting for primary productivity in the sympagic habitat. These differences in FA composition and δ(13)C(FA) values between i-POM and p-POM will aid efforts to track the proportional contribution of sea ice algal carbon to higher trophic levels in the Bering Sea and likely other Arctic seas.

Remote sensing the phytoplankton seasonal succession of the Red Sea.

PubMed

Raitsos, Dionysios E; Pradhan, Yaswant; Brewin, Robert J W; Stenchikov, Georgiy; Hoteit, Ibrahim

2013-01-01

The Red Sea holds one of the most diverse marine ecosystems, primarily due to coral reefs. However, knowledge on large-scale phytoplankton dynamics is limited. Analysis of a 10-year high resolution Chlorophyll-a (Chl-a) dataset, along with remotely-sensed sea surface temperature and wind, provided a detailed description of the spatiotemporal seasonal succession of phytoplankton biomass in the Red Sea. Based on MODIS (Moderate-resolution Imaging Spectroradiometer) data, four distinct Red Sea provinces and seasons are suggested, covering the major patterns of surface phytoplankton production. The Red Sea Chl-a depicts a distinct seasonality with maximum concentrations seen during the winter time (attributed to vertical mixing in the north and wind-induced horizontal intrusion of nutrient-rich water in the south), and minimum concentrations during the summer (associated with strong seasonal stratification). The initiation of the seasonal succession occurs in autumn and lasts until early spring. However, weekly Chl-a seasonal succession data revealed that during the month of June, consistent anti-cyclonic eddies transfer nutrients and/or Chl-a to the open waters of the central Red Sea. This phenomenon occurs during the stratified nutrient depleted season, and thus could provide an important source of nutrients to the open waters. Remotely-sensed synoptic observations highlight that Chl-a does not increase regularly from north to south as previously thought. The Northern part of the Central Red Sea province appears to be the most oligotrophic area (opposed to southern and northern domains). This is likely due to the absence of strong mixing, which is apparent at the northern end of the Red Sea, and low nutrient intrusion in comparison with the southern end. Although the Red Sea is considered an oligotrophic sea, sporadic blooms occur that reach mesotrophic levels. The water temperature and the prevailing winds control the nutrient concentrations within the euphotic zone and enable the horizontal transportation of nutrients.

Geologic youth of galapagos islands confirmed by marine stratigraphy and paleontology.

PubMed

Hickman, C S; Lipps, J H

1985-03-29

Six distinctive types of fossiliferous marine deposits occur on the Galádpagos Islands that provide evidence for the age of emergence of the islands above sea level and hence a maximum age for the islands' terrestrial biota. These subtidal to supratidal deposits include (i) volcanic tuffs with fossils, (ii) limestones and sandstones interbedded with basalt, (iii) terrace deposits, (iv) beach rock, (v) supratidal talus deposits, and (vi) recently uplifted tidal and subtidal rocks and sand. With the exception of (vi), the deposits were previously assigned ages varying from Miocene to Pleistocene, but all are less than about 2 million years old. This age, together with independently determined geologic ages, indicate that the islands emerged from the sea relatively recently and that all evolution of the islands' unique terrestrial biota occurred within the past 3 to 4 million years.

Variations in radiolarian assemblages in the Japan Sea since the Last Glacial Period: implications for paleoceanography Zhi Dong12, Xuefa Shi2, Xinqing Zou1, Jianjun Zou2, Muhong Chen3, Qiang Zhang3, Chendong Ge1,Yanguang Liu21. Nanjing University,China 2. First Institute of Oceanography, China 3. South China Sea Institute of Oceanology, China

NASA Astrophysics Data System (ADS)

Dong, Z.; Shi, X.; Zou, X.; Zou, J. J.; Chen, M.; Zhang, Q.; Ge, C.; Liu, Y.

2017-12-01

Japan Sea is a marginal sea located on the rim of the western Pacific, connecting with the open ocean via key straits with sill depths of less than 130 m, whichis close to the maximum drop of sea level during the Last Glacial Maximum (LGM). Tsushima Strait connects modern JS with neighboring seas and Tsushima Warm Current (TWC), the only warm current flowing into the JS, reaches the northern JS where the cold saline deep wate is formed. Previous studies show that only northern Tsugaru Strait was opened during the last deglaciation, indicating different pattern of water mass exchange between JS and adjacent seas. Few paleoceanographic reconstructions in the southern JS are available to reconstruct the history of inflow of the TWC and deep ventilation. Radiolaria comprises shallow to deep water dwellers, sensitive response to changes in sea water physical and chemical states. It is well known for being preserved in the deep-sea sediments of the North Pacific. In order to decipher the changes of paleoceanography in the JS, here we investigate SST, SSS, deep ventilation using radiolarian assemblages recorded in core KCES1 recovered from the Ulleung Basin. We identified total 108 taxa which have been counted and divided into three categories: TWC, low-salinity and deep water taxa. Changes in radiolaria reveal that the paleoceanographic conditions has changed drastically during the last glacial period. The dominance of low-salinitytaxa indicates low SSS in JS during LGM. For older interval (24-46 ka), low-salinity taxa and TWC taxa could be identified, suggesting both East China Sea Coastal Water, whose volume is higher than Holocene, and TWC flow into the JS. The TWC taxa start to increase at 19 ka, also indicated by negative excursion of TOC δ13C due to the re-open of the Tsushima Strait, coincident with the 19 ka-MWP. The increasing abundance of low-salinity taxa during the B/A warm period, indicated an enhanced influence of river discharge forced by EASM. The enhanced deep ventilation occurred abruptly at 17 ka, caused by the sink of cold and saline water into the deep during the HS 1. While between 13 and 12 ka, high abundance of C.davisiana, one of the dominant species of deep water, inferring the strongest ventilation corresponding to the YD-like event. High abundance of TWC taxa shows the TWC re-enters into the JS during 9-7 ka.

East China Sea Storm Surge Modeling and Visualization System: the Typhoon Soulik case.

PubMed

Deng, Zengan; Zhang, Feng; Kang, Linchong; Jiang, Xiaoyi; Jin, Jiye; Wang, Wei

2014-01-01

East China Sea (ECS) Storm Surge Modeling System (ESSMS) is developed based on Regional Ocean Modeling System (ROMS). Case simulation is performed on the Typhoon Soulik, which landed on the coastal region of Fujian Province, China, at 6 pm of July 13, 2013. Modeling results show that the maximum tide level happened at 6 pm, which was also the landing time of Soulik. This accordance may lead to significant storm surge and water level rise in the coastal region. The water level variation induced by high winds of Soulik ranges from -0.1 to 0.15 m. Water level generally increases near the landing place, in particular on the left hand side of the typhoon track. It is calculated that 0.15 m water level rise in this region can cause a submerge increase of ~0.2 km(2), which could be catastrophic to the coastal environment and the living. Additionally, a Globe Visualization System (GVS) is realized on the basis of World Wind to better provide users with the typhoon/storm surge information. The main functions of GVS include data indexing, browsing, analyzing, and visualization. GVS is capable of facilitating the precaution and mitigation of typhoon/storm surge in ESC in combination with ESSMS.

Freshwater and polynya components of the shelf-derived Arctic Ocean halocline in summer 2007 identified by stable oxygen isotopes

NASA Astrophysics Data System (ADS)

Bauch, D.; Rutgers van der Loeff, M.; Andersen, N.; Torres-Valdes, S.; Bakker, K.; Abrahamsen, E.

2011-12-01

With the aim of determining the origin of freshwater in the halocline, fractions of river water and sea-ice meltwater (or brine influence from sea-ice formation) in the upper 150 m were quantified by a combination of salinity and δ18O and nutrients in the Eurasian basins and the Makarov Basin. Our study indicates which layers of the Arctic Ocean halocline are primarily influenced by sea-ice formation in coastal polynyas and which are primarily influenced by sea-ice formation over the open ocean. With the ongoing changes in sea-ice coverage in the Arctic Ocean it can be expected that these processes will change in the immediate future and that the relative contributions to the halocline will change accordingly. Within the Eurasian Basin a west to east oriented front between net melting and production of sea-ice is observed. Outside the Atlantic regime dominated by net sea-ice melting, a pronounced layer influenced by brines released during sea-ice formation is present at about 30 to 50 m water depth with a maximum over the Lomonosov Ridge. The geographically distinct definition of this maximum demonstrates the rapid release and transport of signals from the shelf regions in discrete pulses within the Transpolar Drift. We use the ratio of sea-ice derived brine influence and river water to link the maximum in brine influence within the Transpolar Drift with a pulse of shelf waters from the Laptev Sea likely released in summer 2005. For a distinction of Atlantic and Pacific-derived contributions the initial phosphate corrected for mineralization with oxygen (PO*) and alternatively the nitrate to phosphate ratio (N/P) in each sample were used. While PO*-based assessments systematically underestimate the contribution of Pacific-derived waters, N/P-based calculations overestimate Pacific-derived waters within the Transpolar Drift due to denitrification in bottom sediments of the Laptev Sea. The extent of Pacific-derived water in the Arctic Ocean was approximately limited by the position of the Lomonosov Ridge in 2007. The ratio of sea-ice derived brine influence and river water is roughly constant within each layer of the Arctic Ocean halocline. The correlation between brine influence and river water reveals two clusters that can be assigned to the two main mechanisms of sea-ice formation within the Arctic Ocean. Over the open ocean or in polynyas at the continental slope sea-ice formation results in a linear correlation between brine influence and river water at salinities of ~ 32 to 34. In coastal polynyas in the shallow regions of the Laptev Sea and southern Kara Sea, sea-ice formation transports river water into the shelf's bottom layer due to the close proximity to the river mouths. This process results in a second linear correlation between brine influence and river water at salinities of ~ 30 to 32.

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.

Temperature under the Tongue: A paleotemperature record of the Drygalksi Ice Tongue with improved chronology of ice retreat

NASA Astrophysics Data System (ADS)

Subt, C.; Rosenheim, B. E.; Lee, J. I.; Yoo, K. C.; Browne, I. M.; Shevenell, A.

2017-12-01

The Ross Embayment is among the most well-studied regions in Antarctica. Despite the relative abundance of data, the style and forcing of deglaciation of the Ross Sea sector following the Last Glacial Maximum (LGM; 23-19 ka) is challenging due to the region's considerable size, complex geometry, and the difficulties in dating Antarctic glaciomarine sedimentary sequences. Ross Sea sediments indicate a dynamic glacial retreat in the western Ross Sea, whereas regional glacial systems may have retreated and advanced multiple times during the last deglaciation. Two marine sediment cores collected near the Drygalski Ice Tongue in the western Ross Sea during 2012 and 2015 Korea Polar Research Institute (KOPRI) expeditions reveal a sequence of alternating diatomaceous muds and oozes interbedded with diamict, which suggest dynamic post-LGM grounded ice retreat in the Ross Sea. Dynamic retreat is hypothesized to have been driven by rising sea levels and warmer ocean waters on the continental shelf, thus a record of upper ocean temperatures should reflect this. Here we present the first post-LGM upper ocean temperature record from the Ross Sea, developed using the TEX86 (tetraether index of lipids consisting of 86 carbons) paleothermometer. To overcome the difficulties of dating these sediments using traditional methods, we apply specialized Ramped PyrOx 14C dating for sediments with high proportions of relict carbon . This technique is particularly well-suited for the post-LGM retreat sedimentary sequences from Antarctic margins because it allows for separation of autochthonous and relict material for dating. By combining organic paleothermometry and state-of-the-art chronologic techniques, we gain a more thorough understanding of upper ocean temperatures in the Ross Sea during the last deglaciation, and their implications for ice retreat.

Effects of using slurry ice during transportation on the microbiological, chemical, and sensory assessments of aquacultured sea bass (Dicentrarchus labrax) stored at 4 degrees C.

PubMed

Cakli, Sukran; Kilinc, Berna; Dincer, Tolga; Tolasa, Sebnem

2006-01-01

Slurry ice, a biphasic system consisting of small spherical ice crystals surrounded by seawater at subzero temperature, was evaluated as a new chilled storage method for whole sea bass (Dicentrarchus labrax) a sparidae fish species of remarkable commercial interests. In this study two different group of chilling methods were used during transportation; in slurry ice packaged (Group A), and flake ice packaged (Group B). The effect of this advanced system during transportation on quality losses and the shelf life of aquacultured sea bass was evaluated. Mesophilic counts for sea bass exceeded 7 log cfu/g, which is considered the maximum level for acceptability for freshwater and marine fish after 13 days for groups A and B. On day 13 TVB-N values of groups A and B, reached the legal limits (35 mg/100 g set for TVB-N) for consumption. According to the results of sensory analyses, up to day 9 all the groups were determined as "acceptable" but on day 13 the groups A and B were no longer acceptable. The main negative aspect related to quality loss in slurry ice group corresponded to the appearance of eyes and gills. Using slurry ice during transportation did not extend the shelf life of sea bass stored at 4 degrees C.

Measurement of the solar ultraviolet radiation at ground level in Bangi, Malaysia

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

Aljawi, Ohoud; Gopir, Geri; Duay, Abdul Basit

2015-04-24

Understanding the amount of ultraviolet (UV) radiation received by human, plant, and animal organisms near the earth’s surface is important to a wide range of fields such as cancer research, agriculture and forestry. The solar ultraviolet spectral irradiance at ground level was measured using the Avantes spectrometer for the period of January to March 2014 at Bangi (2°55´N, 101°46´E, 50 m above sea level) in Malaysia. These data were used to estimate the diurnal variation of UV irradiance (300 – 400 nm). The maximum irradiance of UV radiation was 45 W m{sup −2} on horizontal surface. The maximum irradiance ofmore » UV received in the local noon time, and the minimum values of UV irradiance was received in the local morning time. It is found a bigger value of UV radiation was observed on clear sky in January. The estimation of daily flux average of UV irradiance was (921± 91) kJ m{sup −2}.« less

Regional sea level projections with observed gauge, altimeter and reconstructed data along China coast

NASA Astrophysics Data System (ADS)

Du, L.; Shi, H.; Zhang, S.

2017-12-01

Acting as the typical shelf seas in northwest Pacific Ocean, regional sea level along China coasts exhibits complicated and multiscale spatial-temporal characteristics under circumstance of global change. In this paper, sea level variability is investigated with tide gauges records, satellite altimetry data, reconstructed sea surface height, and CMIP simulation fields. Sea level exhibits the interannual variability imposing on a remarkable sea level rising in the China seas and coastal region, although its seasonal signals are significant as the results of global ocean. Sea level exhibits faster rising rate during the satellite altimetry era, nearly twice to the rate during the last sixty years. AVISO data and reconstructed sea surface heights illustrate good correlation coefficient, more than 0.8. Interannual sea level variation is mainly modulated by the low-frequency variability of wind fields over northern Pacific Ocean by local and remote processes. Meanwhile sea level varies obviously by the transport fluctuation and bimodality path of Kuroshio. Its variability possibly linked to internal variability of the ocean-atmosphere system influenced by ENSO oscillation. China Sea level have been rising during the 20th century, and are projected to continue to rise during this century. Sea level can reach the highest extreme level in latter half of 21st century. Modeled sea level including regional sea level projection combined with the IPCC climate scenarios play a significant role on coastal storm surge evolution. The vulnerable regions along the ECS coast will suffer from the increasing storm damage with sea level variations.

Storm surges in the White and Barents Seas: formation, statistics, analysis

NASA Astrophysics Data System (ADS)

Korablina, Anastasia; Arkhipkin, Victor

2017-04-01

Arctic seas storm surges investigation are high priority in Russia due to the active development of offshore oil and gas, construction of facilities in the coastal zone, as well as for the navigation safety. It is important to study the surges variability, to predict this phenomena and subsequent economic losses, thus including such information into the Russian Arctic Development Program 2020. White and Barents Seas storm surges are caused mainly by deep cyclones of two types: "diving" from the north (88% of all cyclones) and Atlantic from the west. The surge height was defined as the excess of the level that was obtained as the difference between the observed level and subtracting tide level and low-frequency level. The period of low-frequency level oscillation was determined by spectral analysis of the in-situ data. ADCIRC model is used for calculating the storm surge height. We did the calculations on unstructured grid with variable step from 50 to 5000 m. The ADCIRC model was based on the data on wind field, the sea level pressure, the concentration of ice reanalysis CFSR (1979-2010) in increments 0.3°, CFSv2 (2011-2015) in increments 0.2°. On the boundary conditions harmonic constants from Finite Element Solution tide model 2004 (FES2004) in increments 1/8° were set. The following stations on the coast Varandey, Pechora Bay, Chosha Bay, Severodvinsk, Onega, Solovki and other were selected for the storm surges statistical analysis in the period 1979-2015. The number of storm surges (> 0.3 m) long-term variability was obtained, the number of surges at a height (m) range (0.3-0.6, 0.6-0.9, 0.9-1.2, >1.2) was estimated. It shows that 1980 and 1998 are the years with the fewest number storms. For example, the largest number of storm surge (53) was observed in 1995 in Varandey. The height of the surge, possible only once in 100 years, is counted. This maximum height (m) of the surge was noted in Varandey (4.1), Chosha Bay (3.4), Barents Sea, Onega Bay (2.4), White Sea. Quantitative assessment of the pressure and wind contributing to the surge formation was made. The analysis has shown that the wind has a larger contribution (90%) to surge formation in the study area. The study was performed in the framework of the Russian Science Foundation (project 14-37-00038).

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.

Fluvial landscapes evolution in the Gangkou River basin of southern Taiwan: Evidence from the sediment cores

NASA Astrophysics Data System (ADS)

Chen, Jia-Hong; Chyi, Shyh-Jeng; Yen, Jiun-Yee; Lin, Li-Hung; Yen, I.-Chin; Yu, Neng-Ti; Ho, Lih-Der; Jen, Chia-Hung

2017-04-01

The Gangkou River basin is the largest basin in the eastern Hengchun Peninsula of Taiwan. Its main river length is 31km and the basin area is 102sq. km. The width of the active channel is relatively narrow, but the valley from the middle to downstream is remarkably wide, indicating a feature of underfit stream. We drilled two sediment cores in the downstream area, including a 30m core (core-A) from a higher terrace, which is 14m above mean sea level, and a 20m core (core-B) from a lower terrace, which is 4m above mean sea level. Most of the sediments in the core-A are mud, which represents the flood plain facies, and 14C dates in the core-A range from 11ka to 7ka BP. Furthermore, the sediment layers reveal signals of marine events at the core depths of 5m to 11m by X-ray fluorescence. In the core-B, there is an erosional surface at the core depth of 5m. The age of the fluvial gravel layer above the erosional surface is about 0.4ka BP, and the mud layer top the surface is about 8.5ka BP. The preliminary results show that (1) as the tectonic uplift rate induced by the marine terraces around the basin is 1.0 to 2.5 mm/yr, and the accumulation rate of the mud layer in the basin is 6.7 to 8.7 mm/yr, the sediments infilling (more than 30-meters-thick) in the downstream area of the basin should be the results of the lower tectonic uplifting and the higher post-glacial sea level rise and; (2) the marine sediment layer with 14C dates of 7.5ka to 8.5ka BP is very likely the remain of the maximum flooding surface (MFS) in the early Holocene. These results indicate that the fluvial landscapes evolution of the basin was controlled by the sea-level; (3) the erosional surface in the core-B indicates the Gangkou River continuously erode the infilling sediments from 7ka to 0.4ka BP. Previous studies show that the sea-level around Taiwan gradually declined from its high stand since 6ka, we proposed that the continuous erosion was probably the results of tectonic uplifting and eustatic sea-level fall.

Bacterial Diversity in the South Adriatic Sea during a Strong, Deep Winter Convection Year

PubMed Central

Korlević, M.; Pop Ristova, P.; Garić, R.; Amann, R.

2014-01-01

The South Adriatic Sea is the deepest part of the Adriatic Sea and represents a key area for both the Adriatic Sea and the deep eastern Mediterranean. It has a role in dense water formation for the eastern Mediterranean deep circulation cell, and it represents an entry point for water masses originating from the Ionian Sea. The biodiversity and seasonality of bacterial picoplankton before, during, and after deep winter convection in the oligotrophic South Adriatic waters were assessed by combining comparative 16S rRNA sequence analysis and catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH). The picoplankton communities reached their maximum abundance in the spring euphotic zone when the maximum value of the chlorophyll a in response to deep winter convection was recorded. The communities were dominated by Bacteria, while Archaea were a minor constituent. A seasonality of bacterial richness and diversity was observed, with minimum values occurring during the winter convection and spring postconvection periods and maximum values occurring under summer stratified conditions. The SAR11 clade was the main constituent of the bacterial communities and reached the maximum abundance in the euphotic zone in spring after the convection episode. Cyanobacteria were the second most abundant group, and their abundance strongly depended on the convection event, when minimal cyanobacterial abundance was observed. In spring and autumn, the euphotic zone was characterized by Bacteroidetes and Gammaproteobacteria. Bacteroidetes clades NS2b, NS4, and NS5 and the gammaproteobacterial SAR86 clade were detected to co-occur with phytoplankton blooms. The SAR324, SAR202, and SAR406 clades were present in the deep layer, exhibiting different seasonal variations in abundance. Overall, our data demonstrate that the abundances of particular bacterial clades and the overall bacterial richness and diversity are greatly impacted by strong winter convection. PMID:25548042

Towards a full representation of tropical cyclones in a global reanalysis of extreme sea levels

NASA Astrophysics Data System (ADS)

Muis, S.; Verlaan, M.; Lin, N.; Winsemius, H.; Vatvani, D.; Ward, P.; Aerts, J.

2016-12-01

Tropical cyclones (TCs), including hurricanes and typhoons, are characterised by high wind speeds and low pressure, and cause dangerous storm surges in coastal areas. Recent disasters like the flooding of New Orleans in 2005 due to Hurricane Katrina and of New York in 2012 due to Hurricane Sandy exemplify the significant TC risk in the United States. In this contribution, we present a new framework to model TC storm surges and probabilities at the Atlantic basin- and, ultimately, global scales. This works builds on the work of Muis et al. (2016), which presented the first dynamically-derived reanalysis dataset of storm surges that covers the entire world's coastline (GTSR dataset). Surge levels for the period 1979-2014 were simulated by forcing the Global Surge and Tide Model (GTSM) with wind speed and atmospheric pressure from the ERA-Interim reanalysis. There is generally a good agreement between simulated and observed sea level extremes in extra-tropical regions; however for areas prone to TCs there is a severe underestimation of extremes. For example, the maximum surge levels during Hurricane Katrina in New Orleans exceeded 8 m, whilst the GTSM surge levels in that area do not exceed 2-3 m. Hence, due to the coarse grid resolution, the strong intensities of TCs are not fully captured in ERA-Interim. Furthermore, the length of ERA-Interim data set, like other reanalysis datasets, is too short to estimate the probabilities of extreme TC events in a reliable way. For accurate risk assessments it is essential to improve the representation of TCs in these global reanalysis of extreme sea levels. First, we need a higher resolution of meteorological forcing, which can be modelled with input from the observed best track data. Second, we need to statistically extend the observed record to many thousands of years. We will present the first results of these steps for the east coast of the United States. We will validate the GTSM model forced with best track data using recent extreme events like Katrina and Sandy. We will investigate how the statistics of the extreme sea level will change due to improved representation of TCs.

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

Sequence stratigraphy of the Maastrichtian-Paleocene succession at the Dakhla Oasis, Western Desert, Egypt

NASA Astrophysics Data System (ADS)

Hewaidy, Abdel Galil A.; Farouk, Sherif; Bazeen, Youssef S.

2017-12-01

The Maastrichtian-Paleocene succession at the Dakhla Oasis is marked by the presence of a typical Nile Valley Facies represented by the Dakhla and Tarawan formations in Edmonstone and Qur El Malik sections in the central and western parts of the oasis, while a mixed Nile Valley and Garra Al-Arbain facies represented by Dakhla, Kurkur and Tarawan formations in Teneida section in the eastern part of the oasis adjacent to the Abu Tartur Plateau. These sections were examined for their foraminiferal contents, lithologic characters and stratigraphic boundaries. The distribution of foraminifera in the studied sections is variable and inconstant, as the planktonics are concentrated only at certain levels, which may be considered as a time intervals of transgression and maximum flooding surfaces. Eight planktonic biozones are distinguished in this work; of theses two are of Maastrichtain age and six are of Paleocene age. Eight 3rd order depositional sequences are recognized in the studied Maastrichtian-Paleocene succession based on the time stratigraphic boundaries released from the planktonic foraminifera and sea level changes which are released from the paleoecologic interpretations. The distinguished sequences are subdivided into their systems tracts based on the paleobathymetric interpretations of P/B% and benthic biofacies analysis. These sequences are bounded by eight sequence boundaries (SB A - SB H) represented by unconformity surfaces and depositional hiatuses. The correlation of the sequence boundaries of the established depositional sequences with the eustatic sea level curve, suggesting that these depositional sequences were resulted from the interplay of eustatic sea-level changes and local tectonic activities.

Wave-induced stress and breaking of sea ice in a coupled hydrodynamic discrete-element wave-ice model

NASA Astrophysics Data System (ADS)

Herman, Agnieszka

2017-11-01

In this paper, a coupled sea ice-wave model is developed and used to analyze wave-induced stress and breaking in sea ice for a range of wave and ice conditions. The sea ice module is a discrete-element bonded-particle model, in which ice is represented as cuboid grains floating on the water surface that can be connected to their neighbors by elastic joints. The joints may break if instantaneous stresses acting on them exceed their strength. The wave module is based on an open-source version of the Non-Hydrostatic WAVE model (NHWAVE). The two modules are coupled with proper boundary conditions for pressure and velocity, exchanged at every wave model time step. In the present version, the model operates in two dimensions (one vertical and one horizontal) and is suitable for simulating compact ice in which heave and pitch motion dominates over surge. In a series of simulations with varying sea ice properties and incoming wavelength it is shown that wave-induced stress reaches maximum values at a certain distance from the ice edge. The value of maximum stress depends on both ice properties and characteristics of incoming waves, but, crucially for ice breaking, the location at which the maximum occurs does not change with the incoming wavelength. Consequently, both regular and random (Jonswap spectrum) waves break the ice into floes with almost identical sizes. The width of the zone of broken ice depends on ice strength and wave attenuation rates in the ice.

County-Level Climate Uncertainty for Risk Assessments: Volume 23 Appendix V - Forecast Sea Ice Thickness

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

Backus, George A.; Lowry, Thomas Stephen; Jones, Shannon M.

2017-04-01

This report uses the CMIP5 series of climate model simulations to produce country- level uncertainty distributions for use in socioeconomic risk assessments of climate change impacts. It provides appropriate probability distributions, by month, for 169 countries and autonomous-areas on temperature, precipitation, maximum temperature, maximum wind speed, humidity, runoff, soil moisture and evaporation for the historical period (1976-2005), and for decadal time periods to 2100. It also provides historical and future distributions for the Arctic region on ice concentration, ice thickness, age of ice, and ice ridging in 15-degree longitude arc segments from the Arctic Circle to 80 degrees latitude, plusmore » two polar semicircular regions from 80 to 90 degrees latitude. The uncertainty is meant to describe the lack of knowledge rather than imprecision in the physical simulation because the emphasis is on unfalsified risk and its use to determine potential socioeconomic impacts. The full report is contained in 27 volumes.« less

County-Level Climate Uncertainty for Risk Assessments: Volume 24 Appendix W - Historical Sea Ice Age.

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

Backus, George A.; Lowry, Thomas Stephen; Jones, Shannon M

2017-05-01

This report uses the CMIP5 series of climate model simulations to produce country- level uncertainty distributions for use in socioeconomic risk assessments of climate change impacts. It provides appropriate probability distributions, by month, for 169 countries and autonomous-areas on temperature, precipitation, maximum temperature, maximum wind speed, humidity, runoff, soil moisture and evaporation for the historical period (1976-2005), and for decadal time periods to 2100. It also provides historical and future distributions for the Arctic region on ice concentration, ice thickness, age of ice, and ice ridging in 15-degree longitude arc segments from the Arctic Circle to 80 degrees latitude, plusmore » two polar semicircular regions from 80 to 90 degrees latitude. The uncertainty is meant to describe the lack of knowledge rather than imprecision in the physical simulation because the emphasis is on unfalsified risk and its use to determine potential socioeconomic impacts. The full report is contained in 27 volumes.« less

County-Level Climate Uncertainty for Risk Assessments: Volume 22 Appendix U - Historical Sea Ice Thickness

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

Backus, George A.; Lowry, Thomas Stephen; Jones, Shannon M

2017-06-01

This report uses the CMIP5 series of climate model simulations to produce country- level uncertainty distributions for use in socioeconomic risk assessments of climate change impacts. It provides appropriate probability distributions, by month, for 169 countries and autonomous-areas on temperature, precipitation, maximum temperature, maximum wind speed, humidity, runoff, soil moisture and evaporation for the historical period (1976-2005), and for decadal time periods to 2100. It also provides historical and future distributions for the Arctic region on ice concentration, ice thickness, age of ice, and ice ridging in 15-degree longitude arc segments from the Arctic Circle to 80 degrees latitude, plusmore » two polar semicircular regions from 80 to 90 degrees latitude. The uncertainty is meant to describe the lack of knowledge rather than imprecision in the physical simulation because the emphasis is on unfalsified risk and its use to determine potential socioeconomic impacts. The full report is contained in 27 volumes.« less

County-Level Climate Uncertainty for Risk Assessments: Volume 21 Appendix T - Forecast Sea Ice Area Fraction.

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

Backus, George A.; Lowry, Thomas Stephen; Jones, Shannon M.

2017-06-01

This report uses the CMIP5 series of climate model simulations to produce country- level uncertainty distributions for use in socioeconomic risk assessments of climate change impacts. It provides appropriate probability distributions, by month, for 169 countries and autonomous-areas on temperature, precipitation, maximum temperature, maximum wind speed, humidity, runoff, soil moisture and evaporation for the historical period (1976-2005), and for decadal time periods to 2100. It also provides historical and future distributions for the Arctic region on ice concentration, ice thickness, age of ice, and ice ridging in 15-degree longitude arc segments from the Arctic Circle to 80 degrees latitude, plusmore » two polar semicircular regions from 80 to 90 degrees latitude. The uncertainty is meant to describe the lack of knowledge rather than imprecision in the physical simulation because the emphasis is on unfalsified risk and its use to determine potential socioeconomic impacts. The full report is contained in 27 volumes.« less

County-Level Climate Uncertainty for Risk Assessments: Volume 25 Appendix X - Forecast Sea Ice Age.

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

Backus, George A.; Lowry, Thomas Stephen; Jones, Shannon M.

2017-05-01

This report uses the CMIP5 series of climate model simulations to produce country- level uncertainty distributions for use in socioeconomic risk assessments of climate change impacts. It provides appropriate probability distributions, by month, for 169 countries and autonomous-areas on temperature, precipitation, maximum temperature, maximum wind speed, humidity, runoff, soil moisture and evaporation for the historical period (1976-2005), and for decadal time periods to 2100. It also provides historical and future distributions for the Arctic region on ice concentration, ice thickness, age of ice, and ice ridging in 15-degree longitude arc segments from the Arctic Circle to 80 degrees latitude, plusmore » two polar semicircular regions from 80 to 90 degrees latitude. The uncertainty is meant to describe the lack of knowledge rather than imprecision in the physical simulation because the emphasis is on unfalsified risk and its use to determine potential socioeconomic impacts. The full report is contained in 27 volumes.« less

Sea Consultants Inc, Cambridge, MA

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

Reed, D.F.

1989-06-01

The EPA is currently developing regulations to limit the radon concentration in public water supplies. Based on the latest scientific evaluations, it appears that the health impact of radon is larger than suggested by guidelines used at the state level. The radon maximum contaminant level being discussed would impact over half of the groundwater supplies in the country and a larger percentage in the New England States. In Friendship, Maine, a public water system was recently placed into operation that uses a bedrock well as a source. High radon levels are treated using granulated activated carbon contactors. Performance testing wasmore » completed that provides insight into process effectiveness and the flexibility of GAC to respond to varying loading rates. 17 refs., 5 figs., 1 tab.« less

Inception and variability of the Antarctic ice sheet across the Eocene-Oligocene transition

NASA Astrophysics Data System (ADS)

Stocchi, Paolo; Galeotti, Simone; Ladant, Jan-Baptiste; DeConto, Robert; Vermeersen, Bert; Rugenstein, Maria

2014-05-01

Climate cooling throughout middle to late Eocene (~48 - 34 Million years ago, Ma) triggered the transition from hot-house to ice-house conditions. Based on deep-sea marine δ18O values, a continental-scale Antarctic Ice Sheet (AIS) rapidly developed across the Eocene-Oligocene transition (EOT) in two ~200 kyr-spaced phases between 34.0 - 33.5 Ma. Regardless of the geographical configuration of southern ocean gateways, geochemical data and ice-sheet modelling show that AIS glaciation initiated as atmospheric CO2 fell below ~2.5 times pre-industrial values. AIS likely reached or even exceeded present-day dimensions. Quantifying the magnitude and timing of AIS volume variations by means of δ18O records is hampered by the fact that the latter reflect a coupled signal of temperature and ice-sheet volume. Besides, bathymetric variations based on marine geologic sections are affected by large uncertainties and, most importantly, reflect the local response of relative sea level (rsl) to ice volume fluctuations rather than the global eustatic signal. AIS proximal and Northern Hemisphere (NH) marine settings show an opposite trend of rsl change across the EOT. In fact, consistently with central values based on δ18O records, an 60 ± 20m rsl drop is estimated from NH low-latitude shallow marine sequences. Conversely, sedimentary facies from shallow shelfal areas in the proximity of the AIS witness an 50 - 150m rsl rise across the EOT. Accounting for ice-load-induced crustal and geoidal deformations and for the mutual gravitational attraction between the growing AIS and the ocean water is a necessary requirement to reconcile near- and far-field rsl sites, regardless of tectonics and of any other possible local contamination. In this work we investigate the AIS inception and variability across the EOT by combining the observed rsl changes with predictions based on numerical modeling of Glacial Isostatic Adjustment (GIA). We solve the gravitationally self-consistent Sea Level Equation for two different and independent AIS models both driven by atmospheric CO2 variations and evolving on different Antarctic topographies. In particular, minimum and maximum AIS volumes, respectively of ~55m and ~70m equivalent sea level (esl), stem from a smaller and a larger Antarctic topography. Minimum and maximum GIA predictions at the NH rsl sites respectively correspond to the lower limit and central value of the EOT rsl drop inferred from geological data. For both GIA models, the departures from the eustatic trend significantly increase southward toward Antarctica, where the AIS growth is accompanied by a rsl rise. Accordingly, the cyclochronological record of sedimentary cycles retrieved from Cape Roberts Project Drillcore CRP-3 (Victoria Land Basin) witness a deepening across the EOT. Most importantly, CRP-3 record shows that full glacial conditions consistent with the maximum AIS model dimensions were reached only at ~32.8 Ma, while ice-sheet volumes fluctuations around the minimum AIS model volume persisted during the first million years of glaciation.

Characterization of phylogenetically diverse astroviruses of marine mammals.

PubMed

Rivera, Rebecca; Nollens, Hendrik H; Venn-Watson, Stephanie; Gulland, Frances M D; Wellehan, James F X

2010-01-01

Astroviruses are small, non-enveloped, positive-stranded RNA viruses. Previously studied mammalian astroviruses have been associated with diarrhoeal disease. Knowledge of astrovirus diversity is very limited, with only six officially recognized astrovirus species from mammalian hosts and, in addition, one human and some bat astroviruses were recently described. We used consensus PCR techniques for initial identification of five astroviruses of marine mammals: three from California sea lions (Zalophus californianus), one from a Steller sea lion (Eumetopias jubatus) and one from a bottlenose dolphin (Tursiops truncatus). Bayesian and maximum-likelihood phylogenetic analysis found that these viruses showed significant diversity at a level consistent with novel species. Astroviruses that we identified from marine mammals were found across the mamastrovirus tree and did not form a monophyletic group. Recombination analysis found that a recombination event may have occurred between a human and a California sea lion astrovirus, suggesting that both lineages may have been capable of infecting the same host at one point. The diversity found amongst marine mammal astroviruses and their similarity to terrestrial astroviruses suggests that the marine environment plays an important role in astrovirus ecology.

Non-migratory breeding by isolated green sea turtles (Chelonia mydas) in the Indian Ocean: biological and conservation implications.

PubMed

Whiting, Scott D; Murray, Wendy; Macrae, Ismail; Thorn, Robert; Chongkin, Mohammad; Koch, Andrea U

2008-04-01

Green sea turtles (Chelonia mydas) are renowned for their long-distance migrations but have less fame for short-distance migrations or non-migratory behavior. We present satellite telemetric evidence from Cocos (Keeling) Islands, Indian Ocean for the first predominantly non-migratory green sea turtle (C. mydas) population. The mean migration distance from the nesting beach to the foraging grounds was 35.5 km with a maximum mean transit time of 3.4 days. The behavior of this population has major implications for our general understanding of green turtle behavior and their life cycle and for conservation. Firstly, these results indicate a level of juvenile or adult non-breeding homing behavior from the open ocean to foraging grounds adjacent to their natal nesting beach. Secondly, a non-migratory breeding phase reduces the consumption of reproductive energy utilized, potentially resulting in higher fecundity for this population. Thirdly, the close proximity of the nesting and foraging habitats allows for uniformity in management and conservation strategies rarely possible for wide-ranging green turtle populations.

Non-migratory breeding by isolated green sea turtles ( Chelonia mydas) in the Indian Ocean: biological and conservation implications

NASA Astrophysics Data System (ADS)

Whiting, Scott D.; Murray, Wendy; Macrae, Ismail; Thorn, Robert; Chongkin, Mohammad; Koch, Andrea U.

2008-04-01

Green sea turtles ( Chelonia mydas) are renowned for their long-distance migrations but have less fame for short-distance migrations or non-migratory behavior. We present satellite telemetric evidence from Cocos (Keeling) Islands, Indian Ocean for the first predominantly non-migratory green sea turtle ( C. mydas) population. The mean migration distance from the nesting beach to the foraging grounds was 35.5 km with a maximum mean transit time of 3.4 days. The behavior of this population has major implications for our general understanding of green turtle behavior and their life cycle and for conservation. Firstly, these results indicate a level of juvenile or adult non-breeding homing behavior from the open ocean to foraging grounds adjacent to their natal nesting beach. Secondly, a non-migratory breeding phase reduces the consumption of reproductive energy utilized, potentially resulting in higher fecundity for this population. Thirdly, the close proximity of the nesting and foraging habitats allows for uniformity in management and conservation strategies rarely possible for wide-ranging green turtle populations.

Biodiversity patterns of plankton assemblages at the extremes of the Red Sea.

PubMed

Pearman, J K; Kürten, S; Sarma, Y V B; Jones, B H; Carvalho, S

2016-03-01

The diversity of microbial plankton has received limited attention in the main basin of the Red Sea. This study investigates changes in the community composition and structure of prokaryotes and eukaryotes at the extremes of the Red Sea along cross-shelf gradients and between the surface and deep chlorophyll maximum. Using molecular methods to target both the 16S and 18S rRNA genes, it was observed that the dominant prokaryotic classes were Acidimicrobiia, Alphaproteobacteria and Cyanobacteria, regardless of the region and depth. The eukaryotes Syndiniophyceae and Dinophyceae between them dominated in the north, with Bacillariophyceae and Mamiellophyceae more prominent in the southern region. Significant differences were observed for prokaryotes and eukaryotes for region, depth and distance from shore. Similarly, it was noticed that communities became less similar with increasing distance from the shore. Canonical correspondence analysis at the class level showed that Mamiellophyceae and Bacillariophyceae correlated with increased nutrients and chlorophyll a found in the southern region, which is influenced by the input of Gulf of Aden Intermediate Water. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Estimation of the Role of Natural Climatic Trends and Local Depositional Conditions on Peat Formation in the Sacramento-San Joaquin Delta, Based on Palynological and Paleomagnetic Data

NASA Astrophysics Data System (ADS)

Delusina, I.; Verosub, K. L.

2014-12-01

The Sacramento-San Joaquin Delta of California is a critical ecosystem for reconstructing natural and anthropogenic impacts on environmental conditions, understanding stream development, and assessing the fate of artificial levees. Peat formation is influenced by all these processes and represents the combined effects of climatic and hydrographic evolution. In the framework of Project REPEAT, we studied three peat cores using palynological and paleomagnetic methods, focusing on the influence of the general climatic setting and postglacial sea-level changes during the last 6500 years on the process of peat formation and the interplay of local environmental and hydrological conditions. In this report we consider the hypothesis that peat accretion was closely related to general climatic trends, as reflected in atmospheric carbon storage in the Delta sediments, and to general sea-level fluctuation. Based on the fact that the bulk density of the peat is closely correlated with organic carbon content, we examine: 1) whether the pollen concentration is highest when the organic carbon content in the cores is a maximum and corresponds to the warmest episodes; 2) whether organic content is inversely related to the lithic content as determined by paleomagnetic measurements; 3) whether a salinity index based on pollen criteria is highest during the highest stands of sea level; 4) and whether the C3/C4 plant index is a good measure of the carbon content of the peat.

Estimating the sources of global sea level rise with data assimilation techniques.

PubMed

Hay, Carling C; Morrow, Eric; Kopp, Robert E; Mitrovica, Jerry X

2013-02-26

A rapidly melting ice sheet produces a distinctive geometry, or fingerprint, of sea level (SL) change. Thus, a network of SL observations may, in principle, be used to infer sources of meltwater flux. We outline a formalism, based on a modified Kalman smoother, for using tide gauge observations to estimate the individual sources of global SL change. We also report on a series of detection experiments based on synthetic SL data that explore the feasibility of extracting source information from SL records. The Kalman smoother technique iteratively calculates the maximum-likelihood estimate of Greenland ice sheet (GIS) and West Antarctic ice sheet (WAIS) melt at each time step, and it accommodates data gaps while also permitting the estimation of nonlinear trends. Our synthetic tests indicate that when all tide gauge records are used in the analysis, it should be possible to estimate GIS and WAIS melt rates greater than ∼0.3 and ∼0.4 mm of equivalent eustatic sea level rise per year, respectively. We have also implemented a multimodel Kalman filter that allows us to account rigorously for additional contributions to SL changes and their associated uncertainty. The multimodel filter uses 72 glacial isostatic adjustment models and 3 ocean dynamic models to estimate the most likely models for these processes given the synthetic observations. We conclude that our modified Kalman smoother procedure provides a powerful method for inferring melt rates in a warming world.

Estimating the sources of global sea level rise with data assimilation techniques

PubMed Central

Hay, Carling C.; Morrow, Eric; Kopp, Robert E.; Mitrovica, Jerry X.

2013-01-01

A rapidly melting ice sheet produces a distinctive geometry, or fingerprint, of sea level (SL) change. Thus, a network of SL observations may, in principle, be used to infer sources of meltwater flux. We outline a formalism, based on a modified Kalman smoother, for using tide gauge observations to estimate the individual sources of global SL change. We also report on a series of detection experiments based on synthetic SL data that explore the feasibility of extracting source information from SL records. The Kalman smoother technique iteratively calculates the maximum-likelihood estimate of Greenland ice sheet (GIS) and West Antarctic ice sheet (WAIS) melt at each time step, and it accommodates data gaps while also permitting the estimation of nonlinear trends. Our synthetic tests indicate that when all tide gauge records are used in the analysis, it should be possible to estimate GIS and WAIS melt rates greater than ∼0.3 and ∼0.4 mm of equivalent eustatic sea level rise per year, respectively. We have also implemented a multimodel Kalman filter that allows us to account rigorously for additional contributions to SL changes and their associated uncertainty. The multimodel filter uses 72 glacial isostatic adjustment models and 3 ocean dynamic models to estimate the most likely models for these processes given the synthetic observations. We conclude that our modified Kalman smoother procedure provides a powerful method for inferring melt rates in a warming world. PMID:22543163

Assessment on dioxin-like compounds intake from various marine fish from Zhoushan Fishery, China.

PubMed

Wang, Xiangyong; Zhang, Hongxia; Zhang, Lei; Zhong, Kai; Shang, Xiaohong; Zhao, Yunfeng; Tong, Zhendong; Yu, Xinwei; Li, Jingguang; Wu, Yongning

2015-01-01

Sea fish consuming is an important intake source of dioxin-like compounds, especially for the coastal residents. To assess the intake levels of these contaminants from sea fish and to provide risk-based consumption advice, concentrations of 17 polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and 12 dioxin-like polychlorinated biphenyls (dl-PCBs) were measured in 32 commonly consumed fish species from Zhoushan Fishery, China. Due to the different accumulation influenced by fat content, feed habits and living zone in the sea area, the levels of PCDDs, PCDFs and dl-PCBs in different fish species varied significantly ranging from 0.002 to 0.078pg WHO-TEQ/g fresh weight, from 0.002 to 0.553pg WHO-TEQ/g fresh weight and from 0.003 to 2.059pg WHO-TEQ/g fresh weight, respectively. Based on mean fish consuming rate in China, the estimated maximum possible dioxin-like compounds intake through different fish species ranged from 0.26 to 65.61pgTEQkg(-1)bwmonth(-1). Bullet mackerel has the highest monthly intake level which was much higher than other fish species and very close to the provisional tolerable monthly intake (70pgTEQkg(-)(1)bwmonth(-)(1)) proposed by the Joint FAO/WHO Expert Committee on Food Additives. Hence, comparing to other fish species, the consumption of Bullet mackerel from Zhoushan Fishery should be cautious to reduce the potential health risk. Copyright © 2014 Elsevier Ltd. All rights reserved.

Climate Sensitivity, Sea Level, and Atmospheric Carbon Dioxide

NASA Technical Reports Server (NTRS)

Hansen, James; Sato, Makiko; Russell, Gary; Kharecha, Pushker

2013-01-01

Cenozoic temperature, sea level and CO2 covariations provide insights into climate sensitivity to external forcings and sea-level sensitivity to climate change. Climate sensitivity depends on the initial climate state, but potentially can be accurately inferred from precise palaeoclimate data. Pleistocene climate oscillations yield a fast-feedback climate sensitivity of 3+/-1deg C for a 4 W/sq m CO2 forcing if Holocene warming relative to the Last Glacial Maximum (LGM) is used as calibration, but the error (uncertainty) is substantial and partly subjective because of poorly defined LGM global temperature and possible human influences in the Holocene. Glacial-to-interglacial climate change leading to the prior (Eemian) interglacial is less ambiguous and implies a sensitivity in the upper part of the above range, i.e. 3-4deg C for a 4 W/sq m CO2 forcing. Slow feedbacks, especially change of ice sheet size and atmospheric CO2, amplify the total Earth system sensitivity by an amount that depends on the time scale considered. Ice sheet response time is poorly defined, but we show that the slow response and hysteresis in prevailing ice sheet models are exaggerated. We use a global model, simplified to essential processes, to investigate state dependence of climate sensitivity, finding an increased sensitivity towards warmer climates, as low cloud cover is diminished and increased water vapour elevates the tropopause. Burning all fossil fuels, we conclude, would make most of the planet uninhabitable by humans, thus calling into question strategies that emphasize adaptation to climate change.

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.

Evaluation of Fluoride Retention Due to Most Commonly Consumed Estuarine Fishes Among Fish Consuming Population of Andhra Pradesh as a Contributing Factor to Dental Fluorosis: A Cross-Sectional Study

PubMed Central

Ganta, Shravani; Nagaraj, Anup; Pareek, Sonia; Sidiq, Mohsin; Singh, Kushpal; Vishnani, Preeti

2015-01-01

Background Fluoride in drinking water is known for both beneficial and detrimental effects on health. The principal sources of fluoride include water, some species of vegetation, certain edible marine animals, dust and industrial processes. The purpose of this study was to evaluate the fluoride retention of most commonly consumed estuarine fishes among fish consuming population of Andhra Pradesh. Materials and Methods A cross-sectional study was conducted to evaluate the amount of fluoride retention due to ten most commonly consumed estuarine fishes as a contributing factor to Fluorosis by SPADNS Spectrophotometric method. The presence and severity of dental fluorosis among fish consuming population was recorded using Community Fluorosis Index. Statistical analysis was done using MedCalc v12.2.1.0 software. Results For Sea water fishes, the fluoride levels in bone were maximum in Indian Sardine (4.22 ppm). Amongst the river water fishes, the fluoride levels in bone were maximum in Catla (1.51 ppm). Also, the mean total fluoride concentrations of all the river fishes in skin, muscle and bone were less (0.86 ppm) as compared to the sea water fishes (2.59 ppm). It was unveiled that sea fishes accumulate relatively large amounts of Fluoride as compared to the river water fishes. The mean Community Fluorosis Index was found to be 1.06 amongst a sampled fish consuming population. Evaluation by Community Index for Dental fluorosis (CFI) suggested that fluorosis is of medium public health importance. Conclusion It was analysed that bone tends to accumulate more amount of fluoride followed by muscle and skin which might be due to the increased permeability and chemical trapping of fluoride inside the tissues. The amount of fluoride present in the fishes is directly related to the severity of fluorosis amongst fish consuming population, suggesting fishes as a contributing factor to fluorosis depending upon the dietary consumption. PMID:26266208

Evaluation of Fluoride Retention Due to Most Commonly Consumed Estuarine Fishes Among Fish Consuming Population of Andhra Pradesh as a Contributing Factor to Dental Fluorosis: A Cross-Sectional Study.

PubMed

Ganta, Shravani; Yousuf, Asif; Nagaraj, Anup; Pareek, Sonia; Sidiq, Mohsin; Singh, Kushpal; Vishnani, Preeti

2015-06-01

Fluoride in drinking water is known for both beneficial and detrimental effects on health. The principal sources of fluoride include water, some species of vegetation, certain edible marine animals, dust and industrial processes. The purpose of this study was to evaluate the fluoride retention of most commonly consumed estuarine fishes among fish consuming population of Andhra Pradesh. A cross-sectional study was conducted to evaluate the amount of fluoride retention due to ten most commonly consumed estuarine fishes as a contributing factor to Fluorosis by SPADNS Spectrophotometric method. The presence and severity of dental fluorosis among fish consuming population was recorded using Community Fluorosis Index. Statistical analysis was done using MedCalc v12.2.1.0 software. For Sea water fishes, the fluoride levels in bone were maximum in Indian Sardine (4.22 ppm). Amongst the river water fishes, the fluoride levels in bone were maximum in Catla (1.51 ppm). Also, the mean total fluoride concentrations of all the river fishes in skin, muscle and bone were less (0.86 ppm) as compared to the sea water fishes (2.59 ppm). It was unveiled that sea fishes accumulate relatively large amounts of Fluoride as compared to the river water fishes. The mean Community Fluorosis Index was found to be 1.06 amongst a sampled fish consuming population. Evaluation by Community Index for Dental fluorosis (CFI) suggested that fluorosis is of medium public health importance. It was analysed that bone tends to accumulate more amount of fluoride followed by muscle and skin which might be due to the increased permeability and chemical trapping of fluoride inside the tissues. The amount of fluoride present in the fishes is directly related to the severity of fluorosis amongst fish consuming population, suggesting fishes as a contributing factor to fluorosis depending upon the dietary consumption.

Pleistocene sea level fluctuation and host plant habitat requirement influenced the historical phylogeography of the invasive species Amphiareus obscuriceps (Hemiptera: Anthocoridae) in its native range.

PubMed

Zhang, Danli; Ye, Zhen; Yamada, Kazutaka; Zhen, Yahui; Zheng, Chenguang; Bu, Wenjun

2016-08-31

On account of repeated exposure and submergence of the East China Sea (ECS) land bridge, sea level fluctuation played an important role in shaping the population structure of many temperate species across the ECS during the glacial period. The flower bug Amphiareus obscuriceps (Poppius, 1909) (Hemiptera: Anthocoridae) is an invasive species native to the Sino-Japanese Region (SJR) of East Asia. We tested the hypothesis of the ECS land bridge acting as a dispersal corridor or filter for A. obscuriceps during the glacial period. Specifically, we tested whether and the extent to which dispersal ability and host plant habitat requirement influenced the genetic structure of A. obscuriceps during the exposure of the ECS land bridge. Phylogenetic and network analyses indicated that A. obscuriceps is composed of two major lineages, i.e., China and Japan. Divergence time on both sides of the ECS was estimated to be approximately 1.07 (0.79-1.32) Ma, which was about the same period that the sea level increased. No significant Isolation by Distance (IBD) relationship was found between Фst and Euclidean distances in the Mantel tests, which is consistent with the hypothesis that this species has a good dispersal ability. Our Last Glacial Maximum (LGM) niche modeling of plants that constitute preferred habitats for A. obscuriceps exhibited a similar habitat gap on the exposed ECS continental shelf between China and Japan, but showed a continuous distribution across the Taiwan Strait. Our results suggest that ecological properties (habitat requirement and dispersal ability), together with sea level fluctuation during the Pleistocene across the ECS, have shaped the genetic structure and demographic history of A. obscuriceps in its native area. The host plant habitat requirement could also be a key to the colonization of the A. obscuriceps species during the exposure of the ECS land bridge. Our findings will shed light on the potential role of habitat requirement in the process of biological invasion in future studies.

Reconstruction and paleoclimatic significance of Late Pleistocene niche glaciation at Mt Aston, Tararua Range, North Island, New Zealand

NASA Astrophysics Data System (ADS)

Brook, Martin

2017-04-01

Evidence for the timing of inter-hemispheric climate fluctuations during the Pleistocene is important, with reconstructed mountain glacier extents routinely used as a proxy for climate. While valley glaciers extended out from an ice sheet centred on New Zealand's Southern Alps during Pleistocene climate cooling to below present-day sea level, evidence of former glacial activity on the North Island of New Zealand is rare, in comparison. A newly-identified glaciated site is Mt Aston, an isolated cirque-like basin within the Tararua Range on New Zealand's North Island. Previously published cosmogenic isotope ages and paleo-glacier reconstructions of a 3 km-long valley glacier 30 km to the north show that paleo-equilibrium line altitudes (ELAs) increased northwards across New Zealand during the regional last glacial maximum (LGM). Hence, at this latitude (41˚ 00' S), only topography >1300 m above present day sea-level was of feasible elevation to intersect the prevailing south-westerly airflow and to allow niche glaciers to form. In the basin below Mt Aston, a c. 0.38 km2 cirque glacier existed with ELA of c. 1290 ± 10 m above present-day sea level. This paleo-ELA closely approximates the extrapolated ELA trend surface for the regional LGM. The mean glacier thickness of 35 m gives a maximum basal shear stress of c. 102 kPa-1, with a mean January temperature at the ELA of c. 5.5 ˚ C. It is well-established that present-day glaciers in New Zealand are particularly sensitive to climate change, manifested by glacial advances and retreats in response to simple mass balance dynamics. Consistent with this, the paleo-glacier reconstruction implies that rather than simple temperature decreases driving paleo-ELA depression, changes in south-westerly airflow over New Zealand, bringing moisture-laden but cool air, maximized snowfall and minimised winter melt. The corollary is that (1) patterns of Pleistocene glacier fluctuations may be interpreted as responses, in-part, to precipitation-driven changes, and (2) the extent of LGM glaciation on New Zealand's North Island was probably more extensive than previously assumed.

Impacts of historic morphology and sea level rise on tidal hydrodynamics in a microtidal estuary (Grand Bay, Mississippi)

NASA Astrophysics Data System (ADS)

Passeri, Davina L.; Hagen, Scott C.; Medeiros, Stephen C.; Bilskie, Matthew V.

2015-12-01

This study evaluates the geophysical influence of the combined effects of historic sea level rise (SLR) and morphology on tidal hydrodynamics in the Grand Bay estuary, located in the Mississippi Sound. Since 1848, the landscape of the Mississippi Sound has been significantly altered as a result of natural and anthropogenic factors including the migration of the offshore Mississippi-Alabama (MSAL) barrier islands and the construction of navigational channels. As a result, the Grand Bay estuary has undergone extensive erosion resulting in the submergence of its protective barrier island, Grand Batture. A large-domain hydrodynamic model was used to simulate present (circa 2005) and past conditions (circa 1848, 1917, and 1960) with unique sea levels, bathymetry, topography and shorelines representative of each time period. Additionally, a hypothetical scenario was performed in which Grand Batture Island exists under 2005 conditions in order to observe the influence of the island on tidal hydrodynamics within the Grand Bay estuary. Changes in tidal amplitudes from the historic conditions varied. Within the Sound, tidal amplitudes were unaltered due to the open exposed shoreline; however, in semi-enclosed embayments outside of the Sound, tidal amplitudes increased. In addition, harmonic constituent phases were slower historically. The position of the MSAL barrier island inlets influenced tidal currents within the Sound; the westward migration of Petit Bois Island allowed stronger tidal velocities to be centered on the Grand Batture Island. Maximum tidal velocities within the Grand Bay estuary were 5 cm/s faster historically, and reversed from being flood dominant in 1848 to ebb dominant in 2005. If the Grand Batture Island was reconstructed under 2005 conditions, tidal amplitudes and phases would not be altered, indicating that the offshore MSAL barrier islands and SLR have a greater influence on these tidal parameters within the estuary. However, maximum tidal velocities would increase by as much as 5 cm/s (63%) and currents would become more ebb dominant. Results of this study illustrate the hydrodynamic response of the system to SLR and the changing landscape, and provide insight into potential future changes under SLR and barrier island evolution.

Interpreting operational altimetry signals in near-coastal areas using underwater autonomous vehicles and remotely sensed ocean colour data

NASA Astrophysics Data System (ADS)

Borrione, Ines; Oddo, Paolo; Russo, Aniello; Coelho, Emanuel

2017-04-01

During the LOGMEC16 (Long-Term Glider Mission for Environmental Characterization) sea trial carried out in the eastern Ligurian Sea (Northwestern Mediterranean Sea), two oceanographic gliders rated to a maximum depth of 1000m were operating continuously from 3 May to 27 June 2016. When possible, glider tracks were synchronized with the footprints of contemporaneous altimeters (i.e., Jason 2, Altika and Cryosat 2). Temperature and salinity measured by the gliders along the tracks that were co-localized with the altimeter passages, were used to calculate along-track dynamic heights. The latter were then compared with near-real time absolute sea level CMEMS-TAPAS (Copernicus Marine Environment Monitoring Service - Tailored Product for Data Assimilation) product. TAPAS provides along-track sea level anomaly (SLA) estimates together with all the terms used in the correction and the associated Mean Dynamic Topography. Where available, the CMEMS near-real time 1km resolution, Aqua-MODIS ocean colour data was also used as a tracer of the main oceanographic features of the region. Comparison between SLA derived from gliders and TAPAS along common transects, indicates that differences increase for larger sampling time lags between platforms and especially when time differences exceed 20 hrs. In fact, contemporaneous ocean color images reveal the presence of several mesoscale/sub-mesoscale structures (i.e., transient meanders and filaments), suggesting that the oceanographic variability of the region is likely the main cause for the differences observed between the glider and altimetry-based SLA. Results from this study provide additional evidence of the advantages on using a networked ocean observing system. In fact, the interpretation of in-situ observations obtained from a continuously operating sampling platform (also during ongoing experiments at sea) can be greatly improved when combined with other operational datasets, as the CMEMS SLA used here.

Hurricane Matthew (2016) and its Storm Surge Inundation under Global Warming Scenarios: Application of an Interactively Coupled Atmosphere-Ocean Model

NASA Astrophysics Data System (ADS)

Jisan, M. A.; Bao, S.; Pietrafesa, L.; Pullen, J.

2017-12-01

An interactively coupled atmosphere-ocean model was used to investigate the impacts of future ocean warming, both at the surface and the layers below, on the track and intensity of a hurricane and its associated storm surge and inundation. The category-5 hurricane Matthew (2016), which made landfall on the South Carolina coast of the United States, was used for the case study. Future ocean temperature changes and sea level rise (SLR) were estimated based on the projection of Inter-Governmental Panel on Climate Change (IPCC)'s Representative Concentration Pathway scenarios RCP 2.6 and RCP 8.5. After being validated with the present-day observational data, the model was applied to simulate the changes in track, intensity, storm surge and inundation that Hurricane Matthew would cause under future climate change scenarios. It was found that a significant increase in hurricane intensity, storm surge water level, and inundation area for Hurricane Matthew under future ocean warming and SLR scenarios. For example, under the RCP 8.5 scenario, the maximum wind speed would increase by 17 knots (14.2%), the minimum sea level pressure would decrease by 26 hPa (2.85%), and the inundated area would increase by 401 km2 (123%). By including the effect of SLR for the middle-21st-century scenario, the inundated area will further increase by up to 49.6%. The increase in the hurricane intensity and the inundated area was also found for the RCP 2.6 scenario. The response of sea surface temperature was analyzed to investigate the change in intensity. A comparison was made between the impacts when only the sea surface warming is considered versus when both the sea surface and the underneath layers are considered. These results showed that even without the effect of SLR, the storm surge level and the inundated area would be higher due to the increased hurricane intensity under the influence of the future warmer ocean temperature. The coupled effect of ocean warming and SLR would cause the hurricane-induced storm surge and inundation to be amplified. The relative importance of the ocean warming versus the SLR was evaluated. Keywords: Hurricane Matthew, Global Warming, Coupled Atmosphere-Ocean Model, Air-Sea interactions, Storm Surge, Inundation

Coral Bleaching Products - Office of Satellite and Product Operations

Science.gov Websites

weeks. One DHW is equivalent to one week of sea surface temperatures one degree Celsius greater than the expected summertime maximum. Two DHWs are equivalent to two weeks at one degree above the expected summertime maximum OR one week of two degrees above the expected summertime maximum. Also called Coral Reef

North Pacific atmospheric rivers and their influence on western North America at the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Lora, Juan M.; Mitchell, Jonathan L.; Risi, Camille; Tripati, Aradhna E.

2017-01-01

Southwestern North America was wetter than present during the Last Glacial Maximum. The causes of increased water availability have been recently debated, and quantitative precipitation reconstructions have been underutilized in model-data comparisons. We investigate the climatological response of North Pacific atmospheric rivers to the glacial climate using model simulations and paleoclimate reconstructions. Atmospheric moisture transport due to these features shifted toward the southeast relative to modern. Enhanced southwesterly moisture delivery between Hawaii and California increased precipitation in the southwest while decreasing it in the Pacific Northwest, in agreement with reconstructions. Coupled climate models that are best able to reproduce reconstructed precipitation changes simulate decreases in sea level pressure across the eastern North Pacific and show the strongest southeastward shifts of moisture transport relative to a modern climate. Precipitation increases of ˜1 mm d-1, due largely to atmospheric rivers, are of the right magnitude to account for reconstructed pluvial conditions in parts of southwestern North America during the Last Glacial Maximum.

Hydrogeology and quality of ground water on Guemes Island, Skagit County, Washington

USGS Publications Warehouse

Kahle, S.C.; Olsen, T.D.

1995-01-01

Guemes Island, located in Puget Sound of Washington State, is experiencing population growth and seawater intrusion. The island consists of Pleistocene glacial deposits overlying bedrock. Geologic sections and a map of surficial geology were constructed and used to delineate six hydrogeologic units, three of which are aquifers. The most productive aquifer is the Double Bluff aquifer, situated at or below sea level. Water budget estimates indicate that of the 21-29 inches of precipitation received in a typical year, 0-4 inches runs off, 12-22 inches evapotranspires, and 2-10 inches recharges the ground-water system. Of the water recharged, 0.1-0.3 inches is withdrawn by wells; the remainder recharges deeper aquifer(s) or discharges from the ground-water system to drainage ditches or the sea. The median dissolved-solids concentration was 236 mg/L (milligrams per liter). Half of the samples were classified as moderately hard, the remainder as hard or very hard. Although magnesium-calcium/bicarbonate water types dominate, some samples contained large amounts of sodium and chloride. The median concentration of 0.08 mg/L for nitrate indicates that no widespread contamination from septic systems or livestock exists. Small concentrations of arsenic were present in 5 of 24 samples. Trace concentrations of volatile organic compounds were detected in three of five samples. None of the U.S. Environmental Protection Agency's maximum contaminant levels was exceeded. However, secondary maximum contaminant levels were exceeded for dissolved solids, chloride, manganese, and iron. Seasonal variability of chloride concentration was apparent in water from coastal wells that had chloride concentrations greater than 100 mg/L. Higher values occurred from April through September because of increased pumping and lower recharge.

Diagenesis in coastal carbonates related to Pleistocene sea level, Bermuda Platform

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

Vollbrecht, R.; Meischner, D.

1996-01-01

Pleistocene glacioeustatic sea-level oscillation on the stable Bermuda Platform is expressed in a succession of shallow-water carbonates interrupted by lowstand unconformities. In Bermuda, the maximum highstands of the last 400,000 yr ranged within 10 m around the present level. Coastal carbonates of various highstands are exposed along the present shoreline. These carbonates were penetrated by meteoric and marine pore waters during lowstands and highstands following on deposition. Two representative Pleistocene shoreline sections were studied to see whether early diagenesis has recorded these pore-water changes. The sediments of both sections show multiple generations of cement. Optical and scanning electron microscopy, cathodoluminescencemore » microscopy, X-ray diffraction, microprobe studies and stable-isotope analyses were used to determine the diagenetic environments involved. Regardless of the degree of substrate cementation, freshwater alteration was mainly vadose whereas marine cementation was either phreatic or vadose or both. Early diagenetic oscillation is easier recorded in coastal successions than in lagoonal sediments, mainly because marine cementation is more active nearshore.Because the coastal environment is prone to wave destruction, the potential for preserving these diagenetic features is usually low. Data published on tectonically unstable areas suggest that early diagenetic oscillation may characterize stable coastlines.« less

Impact of winter cooling on the northern part of the Black Sea.

NASA Astrophysics Data System (ADS)

Savchenko, Anatolii

2016-07-01

Climate change in the future may have a negative impact on many countries due to the increasing surface temperature and sea level rise. Probably, unprecedented largest positive trend of surface temperature, which observed since the mid XX century, has associated with increasing human activities around the world. Moreover, this warming will continue in this century, and at the end of the XXI century will be 2 - 5 ºC. Thus, investigation and monitoring of current climate are very important and necessary tasks. Regional model data (downscaling) and satellite data are used, because of underdeveloped network of meteorological stations in the northern part of the Black Sea region. Experiment of downscaling was carried out for the Black Sea region with a high spatial resolution of 0.22° x 0.22° for 1958 - 2007(daily values). For the Black Sea were also used satellite data of sea surface temperature(SST) from MyOcean-2 Project, which CNR(Rome) has reprocessed Pathfinder V5.2 (PFV52) AVHRR data over period 1981 - 2012 with daily gap-free maps (L4) at the original PFV52 resolution at 0.04° x 0.04°. Correlation between satellite SST and surface temperature from regional model climate are amounted 0,99. Thus, surface temperature of model and satellite data for the Black Sea is much correlated between yourself. The following integral characteristics of the Black Sea are referred to the area of sea limited by the 44 - 47º N and 28 - 34º E. Maximum cooling of the north-western part of the Black Sea in winter is occurs after invasion of cold air across the northern border of the basin. In addition, this water area is also interesting in the presence of her huge oil and gas reserves, as well as the construction of liquefied gas (crude oil) terminals. The maximum values of total heat flux (sensible + latent heat fluxes= Q) corresponding to the minimum values of SST are observed during the periods of the negative phase of the NAO. Besides, fluxes with extreme days P (Q) = 95% (the number of which is 5% of the total number of winter days) contribute ≈ 16 - 18% of the total heat flux during the winter, and with P (Q) = 90% - approximately 30%. Typical synoptic situation of extreme winter cooling P (Q) = 95% is presence of anticyclone in the district of Carpathian Mountains. North-easterly flow of cold air at high velocities near-surface wind leads to extreme total heat flux and decreasing SST. Satellite images of clouds well illustrate such cases as, for example, cold air invasion to the Black Sea area on January 23, 2006 (Satellite TERRA). Because of increase of risk associated with climate change, this topic is particularly relevant for the marine area, which is subjected to strong weathering during extreme events in winter. The monitoring of this area will allow reducing the damage from extreme natural events in the future.

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.

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.

Remote sensing and GIS analysis for demarcation of coastal hazard line along the highly eroding Krishna-Godavari delta front

NASA Astrophysics Data System (ADS)

Kallepalli, Akhil; Kakani, Nageswara Rao; James, David B.

2016-10-01

Coastal regions, especially river deltas are highly resourceful and hence densely populated; but these extremely low-lying lands are vulnerable to rising sea levels due to global warming threatening the life and property in these regions. Recent IPCC (2013) predictions of 26-82cm global sea level rise are now considered conservative as subsequent investigations such as by Met Office, UK indicated a vertical rise of about 190cm, which would displace 10% of the world's population living within 10 meters above the sea level. Therefore, predictive models showing the hazard line are necessary for efficient coastal zone management. Remote sensing and GIS technologies form the mainstay of such predictive models on coastal retreat and inundation to future sea-level rise. This study is an attempt to estimate the varying trends along the Krishna-Godavari (K-G) delta region. Detailed maps showing various coastal landforms in the K-G delta region were prepared using the IRS-P6 LISS 3 images. The rate of shoreline shift during a 31-year period along different sectors of the 330km long K-G delta coast was estimated using Landsat-2 and IRS-P6 LISS 3 images between 1977 and 2008. With reference to a selected baseline from along an inland position, End Point Rate (EPR), Shoreline Change Envelope (SCE) and Net Shoreline Movement (NSM) were calculated, using a GIS-based Digital Shoreline Analysis System (DSAS). The results showed that the shoreline migrated landward up to a maximum distance of 3.13km resulting in a net loss of about 42.10km2 area during this 31-year period. Further, considering the nature of landforms and EPR, the future hazard line is predicted for the area, which also indicated a net erosion of about 57.68km2 along the K-G delta coast by 2050 AD.

A last glacial and deglacial pollen record from the northern South China Sea: New insight into coastal-shelf paleoenvironment

NASA Astrophysics Data System (ADS)

Yu, Shaohua; Zheng, Zhuo; Chen, Fang; Jing, Xia; Kershaw, Peter; Moss, Patrick; Peng, Xuechao; Zhang, Xin; Chen, Chixin; Zhou, Yang; Huang, Kangyou; Gan, Huayang

2017-02-01

This study presents a marine palynological record of the Asian summer monsoon and sea level change in the Last Glacial Maximum (LGM) and the deglacial period in the northern South China Sea (SCS). A fossil core STD 235 (855 cm in length) and 273 surface sediment samples from the northern SCS were pollen analysed to reconstruct the paleoenvironment of the continental shelf during the last glacial period. Results from fossil pollen show that the main pollen source region fundamentally changed from the LGM to the deglacial period as sea level rapidly rose. The modern marine surface samples show that pollen concentrations in the estuary of the Pearl River are extremely high, and modern pollen assemblages are in good agreement with the regional vegetation. However, wind transport becomes more important in the deeper ocean as the percentages of Pinus, a taxon with very high pollen production and dispersal capacity, is highest in these sediments, which otherwise have very low pollen concentrations. The concentration of total pollen between surface and fossil pollen samples is compared in order to determine the possible vegetation sources areas for the marine core. Pollen concentration as high as >100 grains/g at the LGM suggested that the paleo-shoreline was located within 80 km of the core. Consequently, pollen would mostly have derived from the exposed continental shelf in the northern SCS. By contrast, pollen concentrations were very low due to a much greater transport distance (318 km at present, core STD 235) under higher sea levels, and windblown pollen played a more important role because of the limitation of riverine input into the deep ocean during this highstand period. Such alternation of pollen flux and source distance should be repeated during all glacial-interglacial cycles, reflecting closely sea level and climate dynamics. According to fossil pollen assemblages from Core STD 235, we conclude that wetland and/or grassland communities with sparse subtropical trees dominated most of the exposed shelf during the LGM rather than forest that characterizes the region today. The existence of a predominantly open landscape on the exposed continental shelf suggests lower precipitation during the LGM, which in turn indicates a weaker Asian summer monsoon. This finding is supported by other records from the Okinawa Trough and the East China Sea, suggesting that a weaker summer monsoon was a key characteristic of the LGM in East Asia.

Factors Contributing to the Interrupted Decay of Hurricane Joaquin (2015) in a Moderate Vertical Wind Shear Environment

DTIC Science & Technology

2017-06-01

at 1200 UTC 3 October with maximum winds of 135 knots (kt) and minimum sea-level pressure of 934 millibars (mb). The time frame for the interrupted ...DeMaria et al. (2005). Figure 17. SHIPS Shear and 200 mb Divergence Since 1800 UTC 4 October was the time of the interruption of the rapid decay of...right) calculations. 43 Time series of CIMSS VWS magnitude (m/s, red line) and direction (degrees, blue line) from which the VWS vector is coming

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.

Cyanobacteria toxins in the Salton Sea

PubMed Central

Carmichael, Wayne W; Li, RenHui

2006-01-01

Background The Salton Sea (SS) is the largest inland body of water in California: surface area 980 km2, volume 7.3 million acre-feet, 58 km long, 14–22 km wide, maximum depth 15 m. Located in the southeastern Sonoran desert of California, it is 85 m below sea level at its lowest point. It was formed between 1905 and 1907 from heavy river flows of the Colorado River. Since its formation, it has attracted both people and wildlife, including flocks of migratory birds that have made the Salton Sea a critical stopover on the Pacific flyway. Over the past 15 years wintering populations of eared grebe (Podiceps nigricollis) at the Salton Sea, have experienced over 200,000 mortalities. The cause of these large die-offs remains unknown. The unique environmental conditions of the Salton Sea, including salinities from brackish freshwater at river inlets to hypersaline conditions, extreme daily summer temperatures (>38°C), and high nutrient loading from rivers and agricultural drainage favor eutrophic conditions that encourage algal blooms throughout the year. A significant component of these algal blooms are the prokaryotic group – the Cyanophyta or blue-green algae (also called Cyanobacteria). Since many Cyanobacteria produce toxins (the cyanotoxins) it became important to evaluate their presence and to determine if they are a contributing factor in eared-grebe mortalities at the Salton Sea. Results From November 1999 to April 2001, 247 water and sediment samples were received for phytoplankton identification and cyanotoxin analyses. Immunoassay (ELISA) screening of these samples found that eighty five percent of all water samples contained low but detectable levels of the potent cyclic peptide liver toxin called microcystins. Isolation and identification of cyanobacteria isolates showed that the picoplanktonic Synechococcus and the benthic filamentous Oscillatoria were dominant. Both organisms were found to produce microcystins dominated by microcystin-LR and YR. A laboratory strain of Synechococcus was identified by PCR as being closest to known marine forms of this genus. Analyses of affected grebe livers found microcystins at levels that may account for some of the acute mortalities. Conclusion The production of microcystins by a marine Synechococcus indicates that microcystins may be a more common occurrence in marine environments – a finding not recognized before this work. Further research should be done to define the distribution of microcystin producing marine cyanobacteria and to determine exposure/response effects of microcystins and possibly other cyanotoxins in the Salton Sea. Future efforts to reduce avian mortalities and remediate the Salton Sea should evaluate vectors by which microcystins enter avian species and ways to control and mitigate toxic cyanobacteria waterblooms at the Salton Sea. PMID:16623944

Colonization of the deep sea by fishes

PubMed Central

Priede, I G; Froese, R

2013-01-01

Analysis of maximum depth of occurrence of 11 952 marine fish species shows a global decrease in species number (N) with depth (x; m): log10N = −0·000422x + 3·610000 (r2 = 0·948). The rate of decrease is close to global estimates for change in pelagic and benthic biomass with depth (−0·000430), indicating that species richness of fishes may be limited by food energy availability in the deep sea. The slopes for the Classes Myxini (−0·000488) and Actinopterygii (−0·000413) follow this trend but Chondrichthyes decrease more rapidly (−0·000731) implying deficiency in ability to colonize the deep sea. Maximum depths attained are 2743, 4156 and 8370 m for Myxini, Chondrichthyes and Actinopterygii, respectively. Endemic species occur in abundance at 7–7800 m depth in hadal trenches but appear to be absent from the deepest parts of the oceans, >9000 m deep. There have been six global oceanic anoxic events (OAE) since the origin of the major fish taxa in the Devonian c. 400 million years ago (mya). Colonization of the deep sea has taken place largely since the most recent OAE in the Cretaceous 94 mya when the Atlantic Ocean opened up. Patterns of global oceanic circulation oxygenating the deep ocean basins became established coinciding with a period of teleost diversification and appearance of the Acanthopterygii. Within the Actinopterygii, there is a trend for greater invasion of the deep sea by the lower taxa in accordance with the Andriashev paradigm. Here, 31 deep-sea families of Actinopterygii were identified with mean maximum depth >1000 m and with >10 species. Those with most of their constituent species living shallower than 1000 m are proposed as invasive, with extinctions in the deep being continuously balanced by export of species from shallow seas. Specialized families with most species deeper than 1000 m are termed deep-sea endemics in this study; these appear to persist in the deep by virtue of global distribution enabling recovery from regional extinctions. Deep-sea invasive families such as Ophidiidae and Liparidae make the greatest contribution to fish fauna at depths >6000 m. PMID:24298950

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.

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.

Palaeoclimatic implications of aeolian sediments on the Miaodao Islands, Bohai Sea, East China, based on OSL dating and proxies

NASA Astrophysics Data System (ADS)

Xu, Shujian; Ding, Xinchao; Yu, Lupeng; Ni, Zhichao

2015-12-01

The loess-paleosol sequences in Shandong Province, East China, is an important aeolian archive, which can provide information for aeolian activity, palaeoclimatic change and sea level change in eastern coast of China since the last interglacial period. However, for so long, most of the studies about loess have been focused on the Chinese Loess Plateau, remaining many questions and disputes about the loess in East China. The Xianjingyuan (XJY) section on the TIA, Bohai Sea, is a representative aeolian section for islands off the eastern coast of China. In this study, optically stimulated luminescence (OSL) dating, particle size and magnetic susceptibility were applied to date and analysis the loess-paleosol sequences in this section. The results show that: (1) The OSL ages at the depths of 0.8 m, 2.5 m, and 3.9 m are 12.6 ± 1.0 ka, 19.2 ± 1.1 ka and 56.9 ± 2.6 ka, respectively, and the loess started to accumulate at ca. 86.5 ka according to the depositional rates (2) The loess accumulated mainly during the Marine Isotope Stage (MIS) 2, i.e., Last glacial maximum and deglaciation, MIS4 and MIS3b with higher depositional rate, coarser grain size, and higher magnetic susceptibility; while paleosol mainly developed during MIS3a, MIS3c and MIS5 with lower depositional rate, finer grain size and lower magnetic susceptibility. (3) The palaeoclimatic changes and aeolian sediments evolution were mainly controlled by the changes of East Asian summer monsoon and sea levels.

Thermal stability of the complex formed between carotenoids from sea buckthorn (Hippophae rhamnoides L.) and bovine β-lactoglobulin

NASA Astrophysics Data System (ADS)

Aprodu, Iuliana; Ursache, Florentina-Mihaela; Turturică, Mihaela; Râpeanu, Gabriela; Stănciuc, Nicoleta

2017-02-01

Sea buckthorn has gained importance as a versatile nutraceutical, due to its high nutritive value in terms of carotenoids content. β-Lactoglobulin (β-LG) is a natural carrier for various bioactive compounds. In this study, the effect of thermal treatment in the temperature range of 25 to 100 °C for 15 min on the complex formed by β-LG and carotenoids from sea buckthorn was reported, based on fluorescence spectroscopy, molecular docking and molecular dynamics simulation results. Also, the berries extracts were analyzed for their carotenoids content. The chromatographic profile of the sea buckthorn extracts revealed the presence of zeaxanthin and β-carotene, as major compounds. The Stern-Volmer constants and binding parameters between β-LG and β-carotene were estimated based on quenching experiments. When thermally treating the β-LG-carotenoids mixtures, an increase in intrinsic and extrinsic fluorescence intensity up to 90 °C was observed, together with blue-shifts in maximum emission in the lower temperature range and red-shifts at higher temperature. Based on fluorescence spectroscopy results, the unfolding of the protein molecules at high temperature was suggested. Detailed information obtained at atomic level revealed that events taking place in the complex heated at high temperature caused important changes in the β-carotene binding site, therefore leading to a more thermodynamically stable assembly. This study can be used to understand the changes occurring at molecular level that could help food operators to design new ingredients and functional foods, and to optimize the processing methods in order to obtain healthier food products.

Hydrographic survey in the dying Aral Sea

NASA Astrophysics Data System (ADS)

Zavialov, P. O.; Kostianoy, A. G.; Emelianov, S. V.; Ni, A. A.; Ishniyazov, D.; Khan, V. M.; Kudyshkin, T. V.

2003-07-01

We report the results of a hydrographic survey conducted in November, 2002, in the Uzbekistan part of the western basin of the dying Aral Sea. There were very few hydrographic measurements in this region since at least early 1990s. The salinity in the western deep basin of the Aral Sea varied from about 82 psu at the surface to over 94 psu at the bottom. The absolute lake surface level was about 30.5 m. Hence, the observed salinity values were much higher, and the level much lower, than expected according to earlier predictions. The density in the western basin exhibited an extremely strong stratification of ~11 kg/m3 per ~20 m in the bottom layer. The picnocline was accompanied by a temperature inversion whose magnitude was ~4°C. The observed density stratification effectively isolating the lower part of the water column from surface exchanges may be responsible for the increase of summer SSTs and evaporation rates reported in previous studies. We discovered the hydrogen sulphide contamination in the bottom layer whose upper limit was at the depth of approximately 22 m. Estimates suggest that the western basin salinization occurs not only because of the local evaporation, but also because of the assimilation of the saltier eastern basin water in the course of the interbasin exchange through the connecting channel. The satellite imagery analysis, in particular the Maximum Cross-Correlation method, suggests that the circulation pattern in the Aral Sea in its present limits is cyclonic under the eastern winds that are predominant in the region throughout the year.

Latest Word on Retreat of the West Antarctic Ice Sheet

NASA Technical Reports Server (NTRS)

Bindschadler, R.

2000-01-01

The West Antarctic ice sheet during the Last Glacial Maximum (LGM) is estimated to have been three times its present volume and to have extended close to the edge of the continental shelf Holocene retreat of this ice sheet in the Ross Sea began between 11,000 and 12,000 years ago. This history implies an average contribution of this ice sheet to sea level of 0.9 mm/a. Evidence of dateable past grounding line positions in the Ross sector are broadly consistent with a linear retreat model. However, inferred rates of retreat for some of these grounding line positions are not consistent with a linear retreat model. More rapid retreat approximately 7600 years ago and possible near-stability in the Ross Sea sector at present suggest a slow rate of initial retreat followed by a more rapid-than-average retreat during the late Holocene, returning to a near-zero rate of retreat currently. This model is also consistent with the mid-Holocene high stand observations of eustatic sea level. Recent compilation of Antarctic bed elevations (BEDMAP) illustrates that the LGM and present grounding lines occur in the shallowest waters, further supporting the model of a middle phase of rapid retreat bracketed by an older and a more recent phase of modest retreat. Extension of these hypotheses into the future make subsequent behavior of the West Antarctic ice sheet more difficult to predict but suggest that if it loses its hold on the present shallow bed, the final retreat of the ice sheet could be very rapid.

The Increase of the Ice-free Season as Further Indication of the Rapid Decline of the Arctic sea ice

NASA Astrophysics Data System (ADS)

Rodrigues, J.

2008-12-01

The unprecedented depletion of sea ice in large sectors of the Arctic Ocean in the summer of 2007 has been the subject of many publications which highlight the spectacular disappearance of the sea ice at the time of minimum ice cover or emphasise the losses at very high latitudes. However, minimum values can be strongly affected by specific circumstances occurring in a comparatively short time interval. The unusually clear skies and the presence of a particular wind pattern over the Arctic Ocean may partly explain the record minimum attained in September 2007. In this contribution, instead of limiting ourselves to the September minimum or the March maximum, we consider the ice conditions throughout the year, opting for a less used, and hopefully more convenient approach. We chose as variables to describe the evolution of the sea ice situation in the Arctic Ocean and peripheral seas in the 1979-2007 period the length of the ice- free season (LIFS) and the inverse sea ice index (ISII). The latter is a quantity that measures the degree of absence of sea ice in a year and varies between zero (when there is a perennial ice cover) and one (when there is open water all year round). We used sea ice concentration data obtained from passive microwave satellite imagery and processed with the Bootstrap algorithm for the SMMR and SSM/I periods, and with the Enhanced NASA Team algorithm for the AMSR-E period. From a linear fit of the observed data, we found that the average LIFS in the Arctic went from 118 days in the late 1970s to 148 days in 2006, which represents an average rate of increase of 1.1 days/year. In the period 2001-2007 the LIFS increased monotonically at an average rate of 5.5 days/year, in good agreement with the general consensus that the Arctic sea ice is currently in an accelerated decline. We also found that 2007 was the longest ice- free season on record (168 days). The ISII also reached a maximum in 2007 . We also investigated what happened at the regional level. For example, the Northwest Passage and the Northern Sea Route are especially relevant to assess the maritime transport between the Atlantic and the Pacific, changes in the ice cover in oil rich areas such as the north coast of Alaska will attract the attention of the oil industry, and the disappearance of the sea ice in Hudson Bay will strongly affect its wildlife. We divided the Arctic in 85 regions and examined how the LIFS and the ISII changed in each of them since 1979. 53 regions enjoyed their longest ice-free seasons in 2006 or 2007. 2006 was special for the Canadian Arctic (longest ice-free season on record for about half of the regions) while 2007 was the year of the Russian Arctic (with the longest ice-free season in the period under study for more than half of the regions). Some of the largest variations were observed in the Russian Arctic, where the average LIFS increased from 84 days in the late 1970s to 129 around 2006, to reach a maximum of 171 days in 2007. Let us quote the changes in the White Sea (105 days between 1979 and 2006), in the South Barents Sea (70 days), in the South East Siberian Sea (60 days) and in the mid-latitude Chukchi Sea (66 days). Other areas where important changes took place include the Gulf of Finland (101 days), the Gulf of Riga (111 days) and the West coast of Spitsbergen (61 days). In the Canadian Arctic it is worth mentioning the increase of 62 days in Hudson Strait, 36 days in Hudson and Baffin Bays, and 52 days in Davis St. In almost all straits and sounds of the High Canadian Arctic the increase has been clearly non-linear and we prefer to compare the average LIFS in the periods 1979-1983 and 2002-2006. We quote an increase of 87 days in Lancaster Sound and of 74 days in Coronation Gulf. class="ab'>

Detecting anthropogenic footprints in sea level rise

NASA Astrophysics Data System (ADS)

Dangendorf, Sönke; Marcos, Marta; Müller, Alfred; Zorita, Eduardo; Riva, Riccardo; Berk, Kevin; Jensen, Jürgen

2015-07-01

While there is scientific consensus that global and local mean sea level (GMSL and LMSL) has risen since the late nineteenth century, the relative contribution of natural and anthropogenic forcing remains unclear. Here we provide a probabilistic upper range of long-term persistent natural GMSL/LMSL variability (P=0.99), which in turn, determines the minimum/maximum anthropogenic contribution since 1900. To account for different spectral characteristics of various contributing processes, we separate LMSL into two components: a slowly varying volumetric component and a more rapidly changing atmospheric component. We find that the persistence of slow natural volumetric changes is underestimated in records where transient atmospheric processes dominate the spectrum. This leads to a local underestimation of possible natural trends of up to ~1 mm per year erroneously enhancing the significance of anthropogenic footprints. The GMSL, however, remains unaffected by such biases. On the basis of a model assessment of the separate components, we conclude that it is virtually certain (P=0.99) that at least 45% of the observed increase in GMSL is of anthropogenic origin.

The salinity, temperature, and delta18O of the glacial deep ocean.

PubMed

Adkins, Jess F; McIntyre, Katherine; Schrag, Daniel P

2002-11-29

We use pore fluid measurements of the chloride concentration and the oxygen isotopic composition from Ocean Drilling Program cores to reconstruct salinity and temperature of the deep ocean during the Last Glacial Maximum (LGM). Our data show that the temperatures of the deep Pacific, Southern, and Atlantic oceans during the LGM were relatively homogeneous and within error of the freezing point of seawater at the ocean's surface. Our chloride data show that the glacial stratification was dominated by salinity variations, in contrast with the modern ocean, for which temperature plays a primary role. During the LGM the Southern Ocean contained the saltiest water in the deep ocean. This reversal of the modern salinity contrast between the North and South Atlantic implies that the freshwater budget at the poles must have been quite different. A strict conversion of mean salinity at the LGM to equivalent sea-level change yields a value in excess of 140 meters. However, the storage of fresh water in ice shelves and/or groundwater reserves implies that glacial salinity is a poor predictor of mean sea level.

Precipitation variability in East Timor during Younger Dryas

NASA Astrophysics Data System (ADS)

Chen, J.; Shen, C.; Mii, H.; Sone, T.; Lin, Y.; Chen, Y.

2012-12-01

Here we present a δ18O record of stalagmite collected from Lekiraka cave, East Timor ( 8o47'10.8"S, 126o23'31.1"E; 626 m above sea level). This stalagmite stable oxygen isotope record, covering an age interval of 13.5-10.8 thousand years ago (ka, before 1950 AD) by an age model using 230Th dates. Featured with an increasing precipitation trend during Younger Dryas (YD), this record is similar to the Gunung Buda cave record in Borneo(Partin et al., Nature, 2007, 449, 452-455) and Liang Luar cave record from Flores(Griffiths et al., Nature Geosciences, 2009, 2, 636-639). However, the detailed YD precipitation variability in Lekiraka record is not completely consistent with that in the nearby Liang Luar record with a precipitation maximum at ~12.4 ka. We propose the intensified precipitation in YD period was attributed to an enhanced Australian-Indonesian summer monsoon and was responded to sea level rise and a southward shift of Intertropical Convergence Zone (ITCZ), which was driven by oceanic/atmospheric circulation change originally from the North Atlantic at the YD.

Potential of ikaite to record the evolution of oceanic δ18O

NASA Astrophysics Data System (ADS)

Rickaby, R. E. M.; Shaw, S.; Bennitt, G.; Kennedy, H.; Zabel, M.; Lennie, A.

2006-06-01

A challenge in the quest to understand the sensitivity of the climate system is the separation of the competing effects of ice volume or sea level, salinity, and temperature on foraminiferal δ18O. We present precipitation experiments on the mineral ikaite, a hydrated form of calcium carbonate found in organic carbon rich deep-marine sediments, that show that the hydration waters within the ikaite crystal capture the δ18O of seawater (δ18Osw) with a fractionation factor of 1.0029 (±0.0002). The δ18Osw measures the volume of continental ice, with an overprint of local salinity. Isolation of δ18Osw by analysis of the hydration waters of sedimentary ikaite preserved at temperatures <4 °C could be exploited to create a record of sea level during the Pleistocene. Preliminary data of δ18Osw from hydration waters of ikaite at the Last Glacial Maximum agree with estimates from modeling of pore waters that Antarctic Bottom Water was +1.4‰ ± 0.2‰ heavier.

Pore fluids and the LGM ocean salinity-Reconsidered

NASA Astrophysics Data System (ADS)

Wunsch, Carl

2016-03-01

Pore fluid chlorinity/salinity data from deep-sea cores related to the salinity maximum of the last glacial maximum (LGM) are analyzed using estimation methods deriving from linear control theory. With conventional diffusion coefficient values and no vertical advection, results show a very strong dependence upon initial conditions at -100 ky. Earlier inferences that the abyssal Southern Ocean was strongly salt-stratified in the LGM with a relatively fresh North Atlantic Ocean are found to be consistent within uncertainties of the salinity determination, which remain of order ±1 g/kg. However, an LGM Southern Ocean abyss with an important relative excess of salt is an assumption, one not required by existing core data. None of the present results show statistically significant abyssal salinity values above the global average, and results remain consistent, apart from a general increase owing to diminished sea level, with a more conventional salinity distribution having deep values lower than the global mean. The Southern Ocean core does show a higher salinity than the North Atlantic one on the Bermuda Rise at different water depths. Although much more sophisticated models of the pore-fluid salinity can be used, they will only increase the resulting uncertainties, unless considerably more data can be obtained. Results are consistent with complex regional variations in abyssal salinity during deglaciation, but none are statistically significant.

What Causes the North Sea Level to Rise Faster over the Last Decade ?

NASA Astrophysics Data System (ADS)

Karpytchev, Mikhail; Letetrel, Camille

2013-04-01

We combined tide gauge records (PSMSL) and satellite altimetry data (TOPEX/POSEIDON-JASON 1-2) to reconstruct the mean level of the North Sea and the Norwegian Sea Shelf (NS-NSS) over 1950-2012. The reconstructed NS-NSS mean sea level fluctuations reveal a pronounced interannual variability and a strong sea level acceleration since the mid-1990's. In order to understand the causes of this acceleration, the NS-NSS mean sea level was cross-correlated with the North Atlantic Oscillation and Arctic Oscillation indices. While the interannual variability of the mean sea level correlates well with the NAO/AO indices, the observed acceleration in the NS-NSS mean level is not linked linearly to the NAO/AO fluctuations. On the other hand, the Empirical Orthogonal Functions (EOF) analysis of steric sea level variations in the eastern North Atlantic gives a dominant EOF pattern (55% of variance explained) that varies on a decadal scale very closely to the NS-NSS mean level flcutuations. Also, the amplification in the temporal amplitude of the dominant steric sea level EOF corresponds to the acceleration observed in the NS-NSS mean sea level signal. This suggests that decadal variations in the mean level of the North Sea - the Norwegian Sea Shelf reflect changes in the Subpolar Front currents (Rossby, 1996).

Sedimentary evolution of the Holocene subaqueous clinoform off the southern Shandong Peninsula in the Western South Yellow Sea

NASA Astrophysics Data System (ADS)

Qiu, Jiandong; Liu, Jian; Saito, Yoshiki; Yang, Zigeng; Yue, Baojing; Wang, Hong; Kong, Xianghuai

2014-10-01

Based on the stratigraphic sequence formed since the last glaciation and revealed by 3000 km long high-resolution shallow seismic profiles and the core QDZ03 acquired recently off the southern Shandong Peninsula, we addressed the sedimentary characteristics of a Holocene subaqueous clinoform in this paper. Integrated analyses were made on the core QDZ03, including sedimentary facies, sediment grain sizes, clay minerals, geochemistry, micro paleontology, and AMS 14C dating. The result indicates that there exists a Holocene subaqueous clinoform, whose bottom boundary generally lies at 15-40 m below the present sea level with its depth contours roughly parallel to the coast and getting deeper seawards. The maximum thickness of the clinoform is up to 22.5 m on the coast side, and the thickness contours generally spread in a banded way along the coastline and becomes thinner towards the sea. At the mouths of some bays along the coast, the clinoform stretches in the shape of a fan and its thickness is evidently larger than that of the surrounding sediments. This clinoform came into being in the early Holocene (about 11.2 cal kyr BP) and can be divided into the lower and upper depositional units (DU 2 and DU 1, respectively). The unit DU 2, being usually less than 3 m in thickness and formed under a low sedimentation rate, is located between the bottom boundary and the Holocene maximum flooding surface (MFS), and represents the sediment of a post-glacial transgressive systems tract; whereas the unit DU 1, the main body of the clinoform, sits on the MFS, belonging to the sediment of a high-stand systems tract from middle Holocene (about 7-6 cal kyr BP) to the present. The provenance of the clinoform differs from that of the typical sediments of the Yellow River and can be considered as the results of the joint contribution from both the Yellow River and the proximal coastal sediments of the Shandong Peninsula, as evidenced by the sediment geochemistry of the core. As is controlled mainly by coactions of multiple factors such as the Holocene sea-level changes, sediment supplies and coastal dynamic conditions, the development of the clinoform is genetically related with the synchronous clinoform or subaqueous deltas around the northeastern Shandong Peninsula and in the northern South Yellow Sea in the spatial distribution and sediment provenance, as previously reported, with all of them being formed from the initial stage of the Holocene up to the present.

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.

Deriving depths of deep chlorophyll maximum and water inherent optical properties: A regional model

NASA Astrophysics Data System (ADS)

Xiu, Peng; Liu, Yuguang; Li, Gang; Xu, Qing; Zong, Haibo; Rong, Zengrui; Yin, Xiaobin; Chai, Fei

2009-10-01

The Bohai Sea is a semi-enclosed inland sea with case-2 waters near the coast. A comprehensive set of optical data was collected during three cruises in June, August, and September 2005 in the Bohai Sea. The vertical profile measurements, such as chlorophyll concentration, water turbidity, downwelling irradiance, and diffuse attenuation coefficient, showed that the Bohai Sea was vertically stratified with a relative clear upper layer superimposed on a turbid lower layer. The upper layer was found to correspond to the euphotic zone and the deep chlorophyll maximum (DCM) occurs at the base of this layer. By tuning a semi-analytical model (Lee et al., 1998, 1999) for the Bohai Sea, we developed a method to derive water inherent optical properties and the depth of DCM from above-surface measurements. Assuming a 'fake' bottom in the stratified water, this new method retrieves the 'fake' bottom depth, which is highly correlated with the DCM depth. The average relative error between derived and measured values is 33.9% for phytoplankton absorption at 440 nm, 25.6% for colored detrital matter (detritus plus gelbstoff) absorption at 440 nm, and 24.2% for the DCM depth. This modified method can retrieve water inherent optical properties and monitor the depth of DCM in the Bohai Sea, and the method is also applicable to other stratified waters.

2015 Arctic Sea Ice Maximum Annual Extent Is Lowest On Record

NASA Image and Video Library

2015-03-19

The sea ice cap of the Arctic appeared to reach its annual maximum winter extent on Feb. 25, according to data from the NASA-supported National Snow and Ice Data Center (NSIDC) at the University of Colorado, Boulder. At 5.61 million square miles (14.54 million square kilometers), this year’s maximum extent was the smallest on the satellite record and also one of the earliest. Read more: 1.usa.gov/1Eyvelz Credit: NASA's Goddard Space Flight Center NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Maternal Steller sea lion diets elevate fetal mercury concentrations in an area of population decline.

PubMed

Rea, Lorrie D; Castellini, J Margaret; Correa, Lucero; Fadely, Brian S; O'Hara, Todd M

2013-06-01

Total mercury concentrations ([THg]) measured in western Aleutian Island Steller sea lion pup hair were the highest maximum [THg] documented in this endangered species to date. Some pups exceeded concentrations at which other fish-eating mammals can exhibit adverse neurological and reproductive effects (21% and 15% pups above 20 and 30 μg/g in hair, respectively). Of particular concern is fetal exposure to mercury during a particularly vulnerable stage of neurological development in late gestation. Hair and blood [THg] were highly correlated and 20% of pups sampled in the western Aleutian Islands of Alaska exceeded mammalian risk thresholds established for each of these tissues. Higher nitrogen isotope ratios suggested that pups accumulated the highest [THg] when their dams fed on higher trophic level prey during late gestation. Copyright © 2013 Elsevier B.V. All rights reserved.

A decision analysis approach to climate adaptation: comparing multiple pathways for multi-decadal decision making

NASA Astrophysics Data System (ADS)

Lin, B. B.; Little, L.

2013-12-01

Policy planners around the world are required to consider the implications of adapting to climatic change across spatial contexts and decadal timeframes. However, local level information for planning is often poorly defined, even though climate adaptation decision-making is made at this scale. This is especially true when considering sea level rise and coastal impacts of climate change. We present a simple approach using sea level rise simulations paired with adaptation scenarios to assess a range of adaptation options available to local councils dealing with issues of beach recession under present and future sea level rise and storm surge. Erosion and beach recession pose a large socioeconomic risk to coastal communities because of the loss of key coastal infrastructure. We examine the well-known adaptation technique of beach nourishment and assess various timings and amounts of beach nourishment at decadal time spans in relation to beach recession impacts. The objective was to identify an adaptation strategy that would allow for a low frequency of management interventions, the maintenance of beach width, and the ability to minimize variation in beach width over the 2010 to 2100 simulation period. 1000 replications of each adaptation option were produced against the 90 year simulation in order to model the ability each adaptation option to achieve the three key objectives. Three sets of adaptation scenarios were identified. Within each scenario, a number of adaptation options were tested. The three scenarios were: 1) Fixed periodic beach replenishment of specific amounts at 20 and 50 year intervals, 2) Beach replenishment to the initial beach width based on trigger levels of recession (5m, 10m, 20m), and 3) Fixed period beach replenishment of a variable amount at decadal intervals (every 10, 20, 30, 40, 50 years). For each adaptation option, we show the effectiveness of each beach replenishment scenario to maintain beach width and consider the implications of more frequent replenishment with that of implementation cost. We determine that a business as usual scenario, where no adaptation is implemented, would lead to an average beach recession of 12.02 meters and a maximum beach recession of 33.23 meters during the period of 2010-2100. The best adaptation option modeled was a fixed replenishment of 5 meters every 20 years leading to 4 replenishment events with an average beach recession of 2.99 meters and a maximum beach recession of 15.02 meters during the period of 2010-2100. The presented simulations explicitly address the uncertainty of future impacts due to sea level rise and storm surge and show a range of options that could be considered by a local council to meet their policy objectives. The simulation runs provide managers the ability to consider the utility of various adaptation options and the timing and costs of implementation. Such information provides an evidence-based practice to decision-making and allows policy makers to transparently make decisions based on best estimates of modeled climate change.

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.

33 CFR 164.35 - Equipment: All vessels.

Code of Federal Regulations, 2010 CFR

2010-07-01

... to alter course 90 degrees with maximum rudder angle and constant power settings, for either full and...: (i) Calm weather—wind 10 knots or less, calm sea; (ii) No current; (iii) Deep water conditions—water...: (1) Calm weather—wind 10 knots or less, calm sea; (2) No current; (3) Water depth twice the vessel's...

33 CFR 164.35 - Equipment: All vessels.

Code of Federal Regulations, 2011 CFR

2011-07-01

... to alter course 90 degrees with maximum rudder angle and constant power settings, for either full and...: (i) Calm weather—wind 10 knots or less, calm sea; (ii) No current; (iii) Deep water conditions—water...: (1) Calm weather—wind 10 knots or less, calm sea; (2) No current; (3) Water depth twice the vessel's...

Satellite-observed variability of phytoplankton size classes associated with a cold eddy in the South China Sea.

PubMed

Lin, Junfang; Cao, Wenxi; Wang, Guifen; Hu, Shuibo

2014-06-15

Ocean-color remote sensing has been used as a tool to detect phytoplankton size classes (PSCs). In this study, a three-component model of PSC was reparameterized using seven years of pigment measurements acquired in the South China Sea (SCS). The model was then used to infer PSC in a cyclonic eddy which was observed west of Luzon Island from SeaWiFS chlorophyll-a (chla) and sea-surface height anomaly (SSHA) products. Enhanced productivity and a shift in the PSC were observed, which were likely due to upwelling of nutrient-rich water into the euphotic zone. The supply of nutrients promoted the growth of larger cells (micro- and nanoplankton), and the PSC shifted to greater sizes. However, the picoplankton were still important and contributed ∼48% to total chla concentration. In addition, PSC time series revealed a lag period of about three weeks between maximum eddy intensity and maximum chlorophyll, which may have been related to phytoplankton growth rate and duration of eddy intensity. Copyright © 2014 Elsevier Ltd. All rights reserved.

Fluxes and burial of particulate organic carbon along the Adriatic mud-wedge (Mediterranean Sea)

NASA Astrophysics Data System (ADS)

Tesi, T.; Langone, L.; Giani, M.; Ravaioli, M.; Miserocchi, S.

2012-04-01

Clinoform-shaped deposits are ubiquitous sedimentological bodies of modern continental margins, including both carbonate and silicoclastic platforms. They formed after the attainment of the modern sea level high-stand (mid-late Holocene) when river outlets and shoreline migrated landward. As clinoform-shape deposits are essential building blocks of the infill of sedimentary basins, they are sites of intense organic carbon (OC) deposition and account for a significant fraction of OC burial in the ocean during interglacial periods. In this study, we focused on sigmoid clinoforms that are generally associated with low-energy environments. In particular, we characterized the modern accumulation and burial of OC along the late-Holocene sigmoid in the Western Adriatic Sea (Mediterranean Sea). This sedimentary body consists of a mud wedge recognizable on seismic profiles as a progradational unit lying on top the maximum flooding surface that marks the time of maximum landward shift of the shoreline attained around 5.5 kyr cal BP. In the last two decades, several projects have investigated sediment dynamics and organic geochemistry along the Adriatic mud wedge (e.g., PRISMA, EURODELTA, EuroSTRATAFORM, PASTA, CIPE, VECTOR). All these studies increased our understanding of strata formation and organic matter cycling in this epicontinental margin. The overarching goal of this study was to combine the results gained during these projects with newly acquired data to assess fluxes to seabed and burial efficiency of organic carbon along the uppermost strata of the Adriatic mud-wedge. Our study benefited of an extensive number of radionuclide-based (Pb-210, and Cs-137) sediment accumulation rates and numerous biogeochemical data of surface sediments and sediment cores (organic carbon, total nitrogen, radiocarbon measurements, carbon stable isotopes, and biomarkers). In addition, because the accumulation of river-borne sediment may or may not be linked to a specific source, another important goal of this study was to characterize the spatial distribution of OC deposition/burial along the Adriatic mud wedge.

Spatial variation of biogenic sulfur in the south Yellow Sea and the East China Sea during summer and its contribution to atmospheric sulfate aerosol.

PubMed

Zhang, Sheng-Hui; Yang, Gui-Peng; Zhang, Hong-Hai; Yang, Jian

2014-08-01

Spatial distributions of biogenic sulfur compounds including dimethylsulfide (DMS), dissolved and particulate dimethylsulfoniopropionate (DMSPd and DMSPp) were investigated in the South Yellow Sea (SYS) and the East China Sea (ECS) in July 2011. The concentrations of DMS and DMSPp were significantly correlated with the levels of chlorophyll a in the surface water. Simultaneously, relatively high ratio values of DMSP/chlorophyll a and DMS/chlorophyll a occurred in the areas where the phytoplankton community was dominated by dinoflagellates. The DMSPp and chlorophyll a size-fractionation showed that larger nanoplankton (5-20 μm) was the most important producer of DMSPp in the study area. The vertical profiles of DMS and DMSP were characterized by a maximum at the upper layer and the bottom concentrations were also relatively higher compared with the overlying layer of the bottom. In addition, a positive linear correlation was observed between dissolved dimethylsulfoxide (DMSOd) and DMS concentrations in the surface waters. The sea-to-air fluxes of DMS in the study area were estimated to be from 0.03 to 102.35 μmol m(-2) d(-1) with a mean of 16.73 μmol m(-2) d(-1) and the contribution of biogenic non-sea-salt SO4(2-) (nss-SO4(2-)) to the measured total nss-SO4(2-) in the atmospheric aerosol over the study area varied from 1.42% to 30.98%, with an average of 8.2%. Copyright © 2014 Elsevier B.V. All rights reserved.