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Sample records for eustatic sea level

  1. Eustatic sea level fluctuations induced by polar wander

    NASA Technical Reports Server (NTRS)

    Sabadini, Roberto; Doglioni, Carlo; Yuen, David A.

    1990-01-01

    It is shown here that polar wander of a viscoelastic, stratified earth can induce global sea level fluctuations comparable to the short-term component in eustatic sea-level curves. The sign of these fluctuations, which are very sensitive to the rheological stratification, depends on the geographical location of the observation point; rises and falls in sea level can thus be coeval in different parts of the world. This finding is a distinct contrast to the main assumption underlying the reconstruction of eustatic curves, namely that global sea-level events produce the same depositional sequence everywhere. It is proposed that polar wander should be added to the list of geophysical mechanisms that can control the third-order cycles in sea level.

  2. Eustatic sea level fluctuations induced by polar wander

    NASA Technical Reports Server (NTRS)

    Sabadini, Roberto; Doglioni, Carlo; Yuen, David A.

    1990-01-01

    It is shown here that polar wander of a viscoelastic, stratified earth can induce global sea level fluctuations comparable to the short-term component in eustatic sea-level curves. The sign of these fluctuations, which are very sensitive to the rheological stratification, depends on the geographical location of the observation point; rises and falls in sea level can thus be coeval in different parts of the world. This finding is a distinct contrast to the main assumption underlying the reconstruction of eustatic curves, namely that global sea-level events produce the same depositional sequence everywhere. It is proposed that polar wander should be added to the list of geophysical mechanisms that can control the third-order cycles in sea level.

  3. Synrift sedimentation in the Gulf of Suez rift controlled by eustatic sea level variations

    SciTech Connect

    Perry, S.K.; Schamel, S.

    1985-01-01

    Laterally persistent stratigraphic variations in the southern Gulf of Suez rift indicate that eustatic variations in sea level predominate over local tectonic effects in controlling Neogene basin-fill sedimentation. Low sea level allows extensive erosion of tilt-block crests and rift shoulders, sending clastic aprons into the intervening subbasins and allowing evaporite deposition. High sea level minimizes clastic input, allowing marls and shales to build up off structure and reefs to form on and around tilt blocks. Thus variations in sediment character indicate relative sea level. Early rifting events in the upper Oligocene are marked by deposition of continental red beds. Overlying lowest Miocene clastics and evaporites are cut by a lower Burdigalian unconformity, indicating a minor transgression in the Aquitanian. Above a disconformity, laterally varying clastics and evaporites suggest regression followed by intermittent shallow-water conditions. A higher unconformity is overlain by thick cyclic evaporites representing periodic flooding and drying of the rift, a result of sea level remaining close to the height of the Suez sill to the north. A major Messinian unconformity cuts the section, indicating major regression, and is overlain by largely clastic sediments of both continental and marine affinities, showing rapid sea level fluctuations. Regional synrift sedimentation has been controlled more by eustatic sea level change, modified by the Suez sill to the north, than by tectonic movements within the rift.

  4. Tertiary delta 18O record and glacio-eustatic sea-level fluctuations.

    USGS Publications Warehouse

    Matthews, R.K.; Poore, R.Z.

    1980-01-01

    Previous interpretation of the Tertiary delta 18O record of planktic and benthic foraminifers has emphasized comparison to the modern ocean, assumed an ice-free world prior to middle Miocene time, and thereby calculated surprisingly cool temperatures for the tropical sea surface. We propose an alternative interpretation, which compares Tertiary data to average late Pleistocene, assumes constant tropical sea-surface temperature, and thereby estimates global ice volume. This approach suggests that Earth has had a significant ice budget (and therefore glacio-eustatic sea-level fluctuations) at least since Eocene and perhaps even throughout much of Cretaceous time. -Authors

  5. New constraints on late Holocene eustatic sea-level changes from Mahé, Seychelles

    NASA Astrophysics Data System (ADS)

    Woodroffe, Sarah A.; Long, Antony J.; Milne, Glenn A.; Bryant, Charlotte L.; Thomas, Alexander L.

    2015-05-01

    This study provides new estimates of globally integrated ice sheet melt during the late Holocene (since 4 ka BP) from Seychelles in the western Indian Ocean, a tectonically stable, far field location where the necessary Glacial-Isostatic Adjustment (GIA) correction is small and is relatively insensitive to predictions using different Earth viscosity profiles. We compare sea level data from Seychelles to estimates of eustasy from two GIA models, ICE-5G and EUST3, which represent end-members in the quantity of global melt during the late Holocene. We use data from a range of coastal environments including fringing reef, present day beaches, fossil plateau and mangrove deposits on the largest island of the Seychelles archipelago, Mahé to reconstruct relative sea-level changes. Our data suggest that extensive coastal deposits of carbonate-rich sands that fringe the west coast formed in the last 2 ka and the horizontal nature of their surface topography suggests RSL stability during this period. Mangrove sediments preserved behind these deposits and in river mouths date to c. 2 ka and indicate that RSL was between -2 m and present during this interval. Correcting the reconstructed sea level data using a suite of optimal GIA models based on the two ice models mentioned above and a large number (c. 350) of Earth viscosity models gives a result that is consistent with the sedimentological constraints. When uncertainties in both model results and data are considered, it is possible to rule out eustatic sea levels below c. 2 m and more than a few decimetres above present during the past two millennia. This uncertainty is dominated by error in the reconstructions rather than the model predictions. We note, however, that our estimates of eustasy are more compatible with the EUST3 model compared to the ICE-5G model during the late Holocene (2-1 ka BP). Our evidence from Seychelles shows that the timing of when eustatic sea level first rose close to present is between the

  6. First Principles Analysis of Convection in the Earth's Mantle, Eustatic Sea Level and Earth Volume

    NASA Astrophysics Data System (ADS)

    Kinsland, G. L.

    2011-12-01

    Steady state convection (convection whereby heat leaving the mantle at the top is equal to the heat entering the mantle across the core mantle boundary and that created within the mantle) of the Earth's mantle is, to a very good approximation, both a constant mass and constant volume process. Mass or volume which moves to one place; e.g., an oceanic ridge; must be accompanied by mass or volume removed from another place. The location of removal, whether from underneath of an ocean or a continent, determines the relationship between oceanic ridge volume and eustatic sea level. If all of the volume entering a ridge were to come from under an oceanic basin then the size of the ridge would not affect eustatic sea level as it would be compensated by a lowering of the sea floor elsewhere. If the volume comes from under a continent then the hypsometry of the continent becomes important. Thus, eustatic sea level is not simply related to convection rate and oceanic ridge volume as posited by Hays and Pitman(1973). Non-steady state convection is still a constant mass process but is not a constant volume process. The mantle experiences a net gain of heat, warms and expands during periods of relatively slow convection (that being convection rate which is less than that necessary to transport incoming and internally created heat to the surface). Conversely, the mantle has a net loss of heat, cools and contracts during periods of relatively rapid convection. The Earth itself expands and contracts as the mantle does. During rapid convection more volume is delivered from the interior of the mantle to the Earth's ridge system than during slow convection. The integral of the difference of ridge system volume between fast and slow convection over a fast-slow convection cycle is a measure of the difference in volume of the mantle over a cycle. The magnitude of the Earth's volume expansion and contraction as calculated from published values for the volume of ocean ridges and is about

  7. Mid-Cretaceous Eustatic sea level fall: magnitude and timing in Gulf of Mexico

    SciTech Connect

    Vierbuchen, R.C.; Oestmann, M.A.; Greenlee, S.M.

    1987-05-01

    The magnitude and timing of a mid-Cretaceous sea level fall have been documented on the margins of the Gulf of Mexico in east Texas. Analysis of seismic, log, and paleontologic data from east Texas demonstrates that a fall of 60 to 100 m occurred at the end of Washita (mid-Cenomanian) time. This sea level fall has been identified elsewhere on the shelves of the Gulf of Mexico and is proposed to have caused the mid-Cretaceous unconformity of the deep sea and the termination of Washita carbonate deposition. They conclude that this sea level fall is of regional significance and eustatic origin. The magnitude and timing of the fall agree with those postulated by Vail and others, and Haq and others, who recognized a major sea level fall in mid-Cenomanian time. The magnitude of sea level fall is estimated from the difference in elevation between carbonate buildups on the Buda margin, which accumulated at or near sea level, and fluvial deposits in the lower Woodbine, which immediately overlie Buda carbonates and have been drilled up to 20 km basinward of the shelf margin. After constructing a datum along the preexisting Buda shelf, they measure the thickness of sediment from this datum to the onlapping fluvial, lower Woodbine siliciclastics. This measurement is then corrected for compaction, isostatic subsidence due to sediment loading, and thermotectonic subsidence. The result, 60 m, is considered a minimum estimate. A similar measurement to the lowest seismically identified coastal onlap in the lower Woodbine yields an estimate of 100 m.

  8. Ferrelo fan, California: Depositional system influenced by Eustatic sea level changes

    USGS Publications Warehouse

    Howell, D.G.; Vedder, J.G.

    1984-01-01

    Remnants of an Eocene fan system are preserved onshore at San Diego and in the central part of the southern California borderland. Even though faults and erosion have truncated its margins, geophysical data and exploratory wells indicate that remaining parts of the fan extend beneath an offshore area nearly 400-km long and 40- to 100-km wide. Environments representing fluvial, fan-delta, shelf-channel, overlapping inner- to outer-fan, and basin-plain facies are recognized or inferred. Three progradational cycles onshore and two distinct pulses of sand accumulation offshore are attributable to eustatic low sea-level stands rather than to tectonic uplift or shifts in depositional patterns. ?? 1984 Springer-Verlag New York Inc.

  9. High eustatic sea level during the middle Pliocene: Evidence from the southeastern U. S. Atlantic Coastal Plain

    SciTech Connect

    Dowsett, H.J.; Cronin, T.M. )

    1990-05-01

    The middle Pliocene, {approximately}3.5-2.5 Ma, was a period of global warmth preceding the growth of major Northern Hemisphere ice sheets. The authors report on eustatic sea level for the middle Pliocene based on microspaleontologic study of marine deposits of the Duplin Formation of South Carolina and North Carolina. The Duplin was deposited during a middle Pliocene marine transgression that formed the Orangeburg scarp, a prominent wave-cut geomorphic paleoshoreline of the southeastern U.S. Atlantic Coastal Plain. They concluded that (1) the scarp in South Carolina was formed mostly during the middle Pliocene (3.5-3.0 Ma), (2) eustatic sea level was about 35 {plus minus} 18 m higher than modern sea level (the scarp has been uplifted about 50-65 m since the middle Pliocene), and (3) ocean-water temperatures along eastern North America were warmer when the scarp was formed that they are at present.

  10. The high tide of the warm Pliocene: Implications of ~20 m Peak Eustatic Sea-Levels for Antarctic Deglaciation

    NASA Astrophysics Data System (ADS)

    Miller, K. G.; Browning, J. V.; Kulpecz, A. A.; Kominz, M. A.; Naish, T.; Rosenthal, Y.; Peltier, W. R.; Sosdian, S. M.; Wright, J. D.

    2010-12-01

    The eustatic peak of the Pliocene (ca. 3 Ma) allows evaluation of sea-level response to conditions warmer than present and with atmospheric carbon dioxide levels similar to the early 21st century. We provide new eustatic estimates for the Pliocene from backstripping shallow-marine, siliciclastic sections in Virginia, U.S.A., and New Zealand, accounting for the effects of compaction, Airy loading, and thermal subsidence. We compare our backstripped eustatic estimates with previously published estimates from a carbonate atoll (Enewetak), deep sea benthic foraminiferal oxygen isotopes, Mg-Ca, and uplifted marine terraces in the Carolinas and Alaska and conclude that the peak was 19±5 m, significantly lower than previously published estimates of 30-40 m derived from uplifted terraces. The 19-m peak implies not only the loss of the total equivalent of Greenland and West Antarctic ice sheets, but suggests volume loss of the East Antarctic Ice Sheet (EAIS) of ~4 m of sea-level equivalent. Our estimates provide helps resolve the long-standing controversy of the stability of the EAIS during the warmer-than-present Pliocene climatic optimum. The sea-level fall at MIC 100 (ca. 2.7 Ma) associated with the growth of large northern hemisphere ice sheets was remarkably large (~100 m) and may have cause a glacial isotostatic adjustment the resulted in uplift of the otherwise tectonically stable New Jersey coastal plain. Despite uncertainties in pre-ice core CO2 and global temperature measurements, the Pliocene provides a critical sea level-atmospheric CO2 calibration point for climates significantly warmer than the last major interglacial, MIC 5e.

  11. Effect of eustatic sea-level changes on saltwater-freshwater relations in the Northern Atlantic Coastal Plain

    USGS Publications Warehouse

    Meisler, Harold; Leahy, P. Patrick; Knobel, LeRoy L.

    1984-01-01

    A finite-difference computer model was used to analyze the effect of eustatic sea-level changes on the development of the transition zone between fresh ground water and underlying saltwater in the northern Atlantic Coastal Plain. The model simulates, in cross section, the sedimentary wedge from the Delaware River estuary in New Jersey to the Continental Slope. Simulated steady-state freshwater flow is separated from static saltwater by a sharp interface. The model was used to test the sensitivity of the simulated interface position to anisotropy as well as to sea-level elevation. Increasing anisotropy causes the interface to be shallower and extend farther offshore. Lowering sea level causes the interface to be deeper and to extend farther offshore. Simulations using hydraulic conductivities based on available data suggest that the transition zone is not in equilibrium with present sea level. The position of the transition zone probably reflects a long-term average sea level of between 50 and 100 ft below present sea level. The cyclic movement of salty ground water in response to sea-level fluctuations during the Quaternary and Late Tertiary caused the saltwater to mix with freshwater, thus producing a broad transition zone. The freshwater is predominantly sodium bicarbonate in character. The saltwater, from New Jersey to Virginia, probably is a sodium calcium chloride brine. In North Carolina, it is primarily seawater.

  12. Impact of eustatic sea level changes on the salt-water fresh-water interface in coastal ground waters

    NASA Astrophysics Data System (ADS)

    Riedel, Thomas; Lettmann, Karsten; Brumsack, Hans-Jürgen

    2010-05-01

    During the Holocene sea level rise has been inundating former glacial to inter-glacial deposits at the North German coast some of which are in use for municipal drinking water abstraction. Sea water intrusion into these sediments represents a serious threat to the coastal freshwater resources. To date, mechanisms and timing of salt water intrusion have not been explored. Interstitial waters from two drilling cores recovered about 3 km offshore the coastline of Northern Germany now offer the possibility of investigating the origin and possible age of the sea water intrusion. The chloride inventory shows that the sea-water fresh-water interface in the subsurface is currently not in equilibrium with the position of todaýs coastline. Furthermore, the shape of the chloride depth profile suggests that at least one regression must have intermitted the Holocene transgression. Based on these findings we conducted a transient numerical simulation to elucidate the impact of eustatic sea level changes on the salt-water fresh-water distribution within the subsurface of coastal regions. We applied a modified Henry model with an inclined surface and forced by a dynamic sea level. The results show that salt fronts in the subsurface follow the coastline during transgressions and promote a fast salinization of the model aquifer. A regression immediately leads to the freshening of surface sediments via the replacement of saline and brackish waters with meteoric waters, while flushing of deeper parts of the model aquifer with fresh-water was significantly slower. Although the coastline has moved seaward saline ground waters remained at depth because ground water velocities are slower and density-driven recirculation of sea water constantly resupplies salt water. The results indicate that the shape of the salt-water fresh-water interface in coastal aquifers may strongly be affected by eustatic sea level changes. They also provide evidence that man-made fixation of the coast line by

  13. Mean age of oceanic lithosphere drives eustatic sea-level change since Pangea breakup

    NASA Astrophysics Data System (ADS)

    Cogné, Jean-Pascal; Humler, Eric; Courtillot, Vincent

    2006-05-01

    The Atlantic and Indian Oceans and the oceanic part of the Antarctic plate have formed at the expense of Panthalassa as a result of Pangea breakup over the last 180 Myr. This major plate reorganization has changed the age vs. surface distribution of oceanic lithosphere and has been a likely driver of sea-level change. Assuming that the age/surface structure of Panthalassa has remained similar to the present-day global distribution from 180 Ma to Present, and using the isochron patterns preserved in the newly formed oceans, we model resulting relative sea-level change. We find a first (slower) phase of sea-level rise (by 90 to 110 m), culminating between 120 and 50 Ma, followed by a (faster) phase of sea-level drop. We show that this result is not strongly sensitive to our hypothesis of constant mean age of Panthalassa, for which much of the information is now erased due to subduction. When the effects of oceanic plateau formation and ice cap development are added, the predicted sea-level curve fits remarkably well the first-order variations of observed sea-level change. We conclude that the changes in mean age of the oceanic lithosphere (varying between 56 and 62 ± 0.2 Myr), which are simply the expression of the Wilson cycle following Pangea breakup, are the main control, accounting for ˜ 70%, of first-order changes in sea-level.

  14. Glaciers dominate eustatic sea-level rise in the 21st century.

    PubMed

    Meier, Mark F; Dyurgerov, Mark B; Rick, Ursula K; O'neel, Shad; Pfeffer, W Tad; Anderson, Robert S; Anderson, Suzanne P; Glazovsky, Andrey F

    2007-08-24

    Ice loss to the sea currently accounts for virtually all of the sea-level rise that is not attributable to ocean warming, and about 60% of the ice loss is from glaciers and ice caps rather than from the two ice sheets. The contribution of these smaller glaciers has accelerated over the past decade, in part due to marked thinning and retreat of marine-terminating glaciers associated with a dynamic instability that is generally not considered in mass-balance and climate modeling. This acceleration of glacier melt may cause 0.1 to 0.25 meter of additional sea-level rise by 2100.

  15. Glaciers dominate eustatic sea-level rise in the 21st century

    USGS Publications Warehouse

    Meier, Mark Frederick; Dyurgerov, M.B.; Rick, Ursula K.; Pfeffer, William Tad; Anderson, Suzanne P.; Glazovsky, Andrey F.

    2007-01-01

    Ice loss to the sea currently accounts for virtually all of the sea-level rise that is not attributable to ocean warming, and about 60% of the ice loss is from glaciers and ice caps rather than from the two ice sheets. The contribution of these smaller glaciers has accelerated over the past decade, in part due to marked thinning and retreat of marine-terminating glaciers associated with a dynamic instability that is generally not considered in mass-balance and climate modeling. This acceleration of glacier melt may cause 0.1 to 0.25 meter of additional sea-level rise by 2100.

  16. Foraminifera in elevated Bermudian caves provide further evidence for +21 m eustatic sea level during Marine Isotope Stage 11

    NASA Astrophysics Data System (ADS)

    van Hengstum, Peter J.; Scott, David B.; Javaux, Emmanuelle J.

    2009-09-01

    Two hypotheses have been proposed to explain the origin of marine isotope stage (MIS) 11 deposits in small Bermudian caves at +21 m above modern sea level: (1) a +21 m MIS 11 eustatic sea-level highstand, and (2) a MIS 11 mega-tsunami event. Importantly, the foraminifera reported in these caves have yet to be critically evaluated within a framework of coastal cave environments. After statistically comparing foraminifera in modern Bermudian littoral caves and the MIS 11 Calonectris Pocket A (+21 m cave) to the largest available database of Bermudian coastal foraminifera, the assemblages found in modern littoral caves - and Calonectris Pocket A - cannot be statistically differentiated from lagoons. This observation is expected considering littoral caves are simply sheltered extensions of a lagoon environment in the littoral zone, where typical coastal processes (waves, storms) homogenize and rework lagoonal, reefal, and occasional planktic taxa. Fossil protoconchs of the Bermudian cave stygobite Caecum caverna were also associated with the foraminifera. These results indicate that the MIS 11 Bermudian caves are fossil littoral caves (breached flank margin caves), where the total MIS 11 microfossil assemblage is preserving a signature of coeval sea level at +21 m. Brackish foraminifera ( Polysaccammina, Pseudothurammina) and anchialine gastropods (˜95%, >300 individuals) indicate a brackish anchialine habitat developed in the elevated caves after the prolonged littoral environmental phase. The onset of sea-level regression following the +21 m highstand would first lower the ancient brackish Ghyben-Herzberg lens (<0.5 m) and flood the cave with brackish water, followed by drainage of the cave to create a permanent vadose environment. These interpretations of the MIS 11 microfossils (considering both taphonomy and paleoecology) are congruent with the micropaleontological, hydrogeological and physical mechanisms influencing modern Bermudian coastal cave environments. In

  17. A 4D Framework for Ocean Basin Paleodepths and Eustatic Sea Level Change

    NASA Astrophysics Data System (ADS)

    Muller, R.; Sdrolias, M.; Gaina, C.

    2006-12-01

    A digital framework for paleobathymetry of the ocean basins requires the complete reconstruction of ocean floor through time, including the main ocean basins, back-arc basins, and now subducted ocean crust. We reconstruct paleo-oceans by creating "synthetic plates", the locations and geometry of which is established on the basis of preserved ocean crust (magnetic lineations and fracture zones), geological data, and the rules of plate tectonics. We reconstruct the spreading histories of the Pacific, Phoenix, Izanagi, Farallon and Kula plates, the plates involved in the Indian, Atlantic, Caribbean, Arctic, Tethys and Arctic oceanic domains and all plates involved in preserved backarc basins. Based mainly on the GML-standards compliant GPlates software and the Generic Mapping Tools, we have created a set of global oceanic paleo-isochrons and paleoceanic age and depth grids. We show that the late-Cretaceous sea level highstand and the subsequent long-term drop in sea level was primarily caused by the changing age-area distribution of Pacific ocean floor through time. The emplacement of oceanic plateaus has resulted in a 40 m sealevel rise between 125 and 110 Ma, and a further 60 m rise after 110 Ma, whereas the oceanic age and latitude dependence of marine sediments has resulted in a 40m sealevel rise since about 120Ma, offsetting the gradual post-80Ma drop in sealevel due to the ageing and deepening mainly of the Pacific ocean basin, with the net effect being an about 200m drop after 80 Ma. Between 140 Ma and the present, oceanic crustal production dropped by over 40% in the Pacific, but stayed roughly constant in the remaining ocean basins. Our results suggest that the overall magnitude of 1st order sealevel change implied by Haq's sea level curve is correct.

  18. 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

  19. Discovery of Lower Pleistocene Shallow-marine Deposits on Mayaguana Island, Bahamas. Implications for Eustatic Sea-Level Curves Derived From Deep-Sea Oxygen-Isotope Records

    NASA Astrophysics Data System (ADS)

    Godefroid, F.; Kindler, P.; Chiaradia, M.; Hasler, C.; Samankassou, E.

    2008-12-01

    87Sr/86Sr-dated marine and beach sediments exposed along the north shore of Mayaguana Island (Bahamas) provide new estimates of the elevation of high sea stands during the Early Pleistocene that will contribute to better calibrate eustatic sea-level curves derived from deep-sea oxygen-isotope records. A newly investigated sea cliff located to the west of Mount Misery Point on the northern coast of Mayaguana, in the SE part of the Bahamian archipelago, includes two vertically stacked sequences of shallow-marine carbonates separated and capped by paleosols and eolianites. The lower unit, reaching up to 5.5 m above modern sea level, consists of coarse laminated calcarenites containing numerous mollusk and red-algal fragments, and large in-situ coral specimens (Diploria strigosa). The second unit, exposed between 7.3 and 10 m, includes bioturbated, coral-rich limestones, overlain by thinly bedded calcarenites characterized by an early generation of fibrous rim cement. 87Sr/86Sr ratios measured from these carbonates range from 0.709123 at the base of the section to 0.709142 at its top. The first unit can be interpreted as a peri-reefal facies deposited when relative sea level was at least 5.5 m above present. The second unit corresponds to one shallowing-upward sequence of subtidal and beach deposits generated when sea level was around 9 m above its actual stand. Sr-isotope ratios indicate that both units were formed during the Early Pleistocene, likely between 1.6 and 1.0 Ma BP. Comparison with existing oxygen-isotope records from deep- sea sediments suggests that the identified sea-level highstands could correspond to negative δ18O peaks estimated at 1.45 and 1.50 Ma BP. Based on the elevation of fossil reefs dating from the last interglacial (Marine Isotope Stage 5e) and the occurrence of Upper Miocene shallow-marine deposits close to modern sea level, Mayaguana can be considered as tectonically stable. The elevation values obtained for these Early Pleistocene

  20. Isotopic Stage 3 Deposition and Stage 2 Erosion of a Clinoform in the Gulf of Papua: Regional Tectonics Versus Eustatic Sea-Level Change

    NASA Astrophysics Data System (ADS)

    Milliman, J. D.; Driscoll, N. W.; Slingerland, R.; Babcock, J.; Walsh, J. P.

    2004-12-01

    Preliminary analysis of 21 piston cores, 24 gravity cores, 1300 nmi of towed CHIRP and more than 2500 nmi of hull-mounted CHIRP seismic data in the Gulf of Papua (GoP) shows that beyond the modern clinoform lies an older, partially eroded clinoform comprising the middle shelf. Approximately 30-40 m of generally sub-parallel reflectors lie beneath a relatively hard acoustic surface and above a set of obliquely prograding reflectors. Based on stratal geometry, their stiff character when cored, and their present elevation, we deduce that this mid-shelf clinoform prograded two-thirds of the way across the pre-existing shelf in response to a relative sea-level rise during Stage 3, when the rate of tectonic subsidence outpaced the rate of eustatic sea-level fall. Deflection of the transgressive surface from horizontal yields a differential subsidence of about 1 to 2 mm/yr from the peripheral bulge in the south to near the basin depocenter in the north. On the basis of the Chappel and Shackleton eustatic sea level curve, eustatic sea level fell from ~-40 to ~-80 m between 45,000 and 25,000 years BP. During this period, tectonic subsidence is interpreted to have outpaced eustasy to create the observed 30-40 m of accommodation. In the central Gulf mid-shelf region, northeast of the Fly River mouth, this clinoform has been dissected by six major valleys ranging in width from 10 to 15 km, cut into the sub-parallel strata and separated from one another by "mesas" that stand 10-20 m higher than the valleys. The mesas also dip gently to the north, presumably reflecting regional subsidence. Cut into both the valleys and mesas are numerous channels, mostly less than ~200 m wide but as much as 30-40 m deep. We interpret this erosion to be the product of rapid eustatic fall commencing ~25,000 years BP (Stage 2) that lowered sea level to -125 m. As eustatic sea level rose from -120 to +3 m about 7,000 years BP, the former mid-shelf river channels within the river valley were

  1. The whole-rock cerium anomaly: a potential indicator of eustatic sea-level changes in shales of the anoxic facies

    NASA Astrophysics Data System (ADS)

    Wilde, Pat; Quinby-Hunt, Mary S.; Erdtmann, Bernd-Dieter

    1996-01-01

    The whole-rock cerium anomaly, tested for outer shelf-upper slope stratigraphic sections from the middle Ordovician through the lower Silurian of Scotland, is proposed as an empirical technique to develop a eustatic 3rd-order or finer-scale sea-level curve. This interval was chosen as it straddles the well-documented Late Ordovician glaciation and can be defined by graptolite zones. The anomaly is calculated from neutron activation analysis of low-carbonate, phosphate-free, fossil-free field-identified shales of the graptolite facies by comparison of the normalized cerium content with the linearized trend of the normalized composition of other rare earth elements in order of atomic number. For sections originally deposited in the main pycnocline below the surface mixed layer, values of the anomaly for a given sample would indicate its position on the redox curves developed for the early Paleozoic by Wilde (1987). Changes in the anomaly that are positive with time would indicate a lowering of sea level as the apparent depth on the redox curve would reflect more oxic conditions. Relative changes negative with time would indicate a rise in sea level as the apparent depth reflects more anoxic conditions. Depending on the vertical sample spacing and the time interval sampled, resolution of the order of 1 m.y. might be achieved. Thus the Vail et al. (1977) curves of the 3rd order (1 to 10 m.y.) or of finer scale could be obtained by this technique with the proper choice of section. Accordingly, for the early through middle Paleozoic when the main pycnocline was anoxic, this geochemical technique could be used to develop eustatic sea-level curves and additionally offer an independent calibration for seismic stratigraphy as well as an indicator of glacial-interglacial climatic sequences or eustatic changes due to fluctuations in global ridge crest volumes.

  2. Glacial-eustatic sea-level fluctuation curve for Carboniferous-Permian boundary strata based on outcrops in the North American Midcontinent and North-Central Texas

    SciTech Connect

    Boardman, D.R. . School of Geology)

    1993-02-01

    Based on lithologic and faunal analysis of uppermost Carboniferous through Lower Permian strata (Wabaunsee through lower Chase groups) exposed from southeastern Nebraska through north-central Oklahoma, a preliminary glacial-eustatic sea-level fluctuation curve is presented herein. In addition to the sea-level curve presented for the Midcontinent region, one for coeval outcropping strata (middle and upper Cisco Group) of the Eastern Shelf of the Midland Basin is also presented based on similar criteria. This sea-level curve is derived from new field studies as well as a refinement of earlier curves presented by Harrison (1973), and Boardman and Malinky (1985). The conclusion on the nature of the Carboniferous-Permian boundary strata cyclothems in the Midcontinent is mirrored by the results of that from North-Central Texas. Each of the primary biostratigraphically-based picks for the Carboniferous-Permian boundary coincide with either intermediate of major cycles in both study areas. Utilization of a glacial-eustatic maximum transgressive event for the Carboniferous-Permian boundary should result in a more correlatable level for intercontinental correlation.

  3. De-confounding of Relations Between Land-Level and Sea-Level Change, Humboldt Bay, Northern California: Uncertain Predictions of Magnitude and Timing of Tectonic and Eustatic Processes

    NASA Astrophysics Data System (ADS)

    Gilkerson, W.; Leroy, T. H.; Patton, J. R.; Williams, T. B.

    2010-12-01

    Humboldt Bay in Northern California provides a unique opportunity to investigate the effects of relative sea level change on both native flora and maritime aquiculture as influenced by both tectonic and eustatic sea-level changes. This combination of superposed influences makes quantitatively predicting relative sea-level more uncertain and consumption of the results for public planning purposes exceedingly difficult. Public digestion for practical purposes is confounded by the fact that the uncertainty for eustatic sea-level changes is a magnitude issue while the uncertainty associated with the tectonic land level changes is both a magnitude and timing problem. Secondly, the public is less well informed regarding how crustal deformation contributes to relative sea-level change. We model the superposed effects of eustatic sea-level rise and tectonically driven land-level changes on the spatial distribution of habitats suitable to native eelgrass (Zostera marina) and oyster mariculture operations in Humboldt Bay. While these intertidal organisms were chosen primarily because they have vertically restricted spatial distributions that can be successfully modeled, the public awareness of their ecologic and economic importance is also well developed. We employ easy to understand graphics depicting conceptual ideas along with maps generated from the modeling results to develop locally relevant estimates of future sea level rise over the next 100 years, a time frame consistent with local planning. We bracket these estimates based on the range of possible vertical deformation changes. These graphic displays can be used as a starting point to propose local outcomes from global and regional relative sea-level changes with respect to changes in the distribution of suitable habitat for ecologically and economically valuable species. Currently the largest sources of uncertainty for changes in relative sea-level in the Humboldt Bay area are 1) the rate and magnitude of tectonic

  4. Simulation of continental basin margin sedimentation in response to crustal movements, eustatic sea level change, and sediment accumulation rates

    SciTech Connect

    Helland-Hansen, W.; Kendall, C.G.St.C.; Lerche, I.; Nakayama, K.

    1988-10-01

    As eustasy, subsidence, and sediment accumulation vary, a 2D computer-based graphical simulation generates on-lapping and off-lapping geometries of both marine and near coastal alluvial deposits, reproducing timelines within sediment-bodies at basin margins. In the simulation, deposition is expressed by creation of new surfaces above previous ones. Thicknesses of layers are reduced by both erosion and compaction while their surfaces move vertically in response to tectonic change and loading. Simulation is divided into a series of equal time steps in which sediment is deposited as an array of en-echelon columns that mark the top of the previous depositional surface. The volume of sediment deposited in each time step is expressed as a 2D cross section and is derived from two right-angle triangles (sand and shale), whose areas are a 2D expression of the quantity of sediment deposited at that time step and whose length matches the width of the offshore sediment wedge seaward of the shoreline. Each column in the array is filled by both marine sediments up to sea level, and alluvial sediments to a surface determined by an alluvial angle that is projected landward from the shore to its intersection with the previous surface. Each time the area representing the sediment column is subtracted from the triangles, the triangle heights are reduced correspondingly. This process is repeated until the triangle heights match the position of sea level above the sediment surface, at which time the remaining area of the sediment triangle is deposited seaward as a single wedge of offshore sediments. This simulation is designed to aid interpretation of stratigraphic sequences. It can be used as a complement to seismic stratigraphy or can be used alone as an inexpensive test of stratigraphic models.

  5. Evaluating the fate of freshwater lenses on atoll islands after eustatic sea-level rise and cyclone-driven inundation: A modelling approach

    NASA Astrophysics Data System (ADS)

    Terry, James P.; Chui, Ting Fong May

    2012-05-01

    Dispersed human populations inhabiting remote atolls across the tropical Pacific Ocean are reliant on the viability of thin freshwater lenses (FWLs) contained within the island coralline sediments for their survival. Yet FWLs are uniquely fragile and easily damaged by saline intrusion. Eustatic sea-level rise (SLR) and sea flooding generated by intense tropical cyclones therefore pose special perils for continued existence on atolls. In this work, mathematical modelling is used to examine the effects on an atoll freshwater lens of various projected long-term SLR scenarios (10, 20, and 40 cm). A cyclone-driven wave washover event is then simulated in order to observe the responses and recovery of the FWL, subsequent to the SLR scenarios imposed. A key attribute of our model design is the inclusion of a topographic depression containing a low-lying fresh swamp in the atoll islet interior (which is often ignored), where seawater accumulates during inundation. Results indicate that a 40 cm SLR produces a major impact: the FWL decreases in thickness by approximately 50%, develops a brackish centre and contracts to a shrunken 'doughnut' morphology. Following cyclone inundation, observed salinity profiles are illuminating. Steep salinity gradients show how a strong saline plume forms at shallow depths, but also reveal the existence of an undisturbed fresh horizon beneath the salt plume under both present conditions and the modest 10 cm SLR scenario. Within the preserved fresh horizon, salt concentrations are maintained below 1.5 g/L (i.e. within usable limits) for at least a year. In contrast, the diminished freshwater lenses that exist after 20 and 40 cm SLR then exhibit far less resilience to saline damage over comparable post-cyclone timeframes. The findings point towards Pacific atolls becoming increasingly uninhabitable long before their complete submergence by sea-level rise, owing to irrecoverable groundwater salinisation seriously reducing the availability of

  6. Climatic, eustatic, and tectnoic controls on Quarternary deposits and landforms, Red Sea coast, Egypt

    NASA Technical Reports Server (NTRS)

    Arvidson, Raymond; Becker, Richard; Shanabrook, Amy; Luo, Wei; Sturchio, Neil; Sultan, Mohamed; Lofty, Zakaria; Mahmood, Abdel Moneim; El Alfy, Zeinhom

    1994-01-01

    The degree to which local climatic variations, eustatic sea level fluctuations, and tectonic uplift have influenced the development of Quaternary marine and fluvial landforms and deposits along the Red Sea coast, Eastern Desert, was investigated using a combination of remote sensing and field data, age determinations of corals, and numerical simulations. False color composites generated from Landsat Thematic Mapper and SPOT image data, digital elevation models derived from sterophotogrammetric analysis of SPOT data, and field observations document that a approximately 10-km wide swath inland from the coast is covered in many places with coalescing alluvial fans of Quaternary age. Wadis cutting through the fans exhibit several pairs of fluvial terraces, and wadi walls expose alluvium interbedded with corraline limestone deposits Further, three distinct coral terraces are evident along the coatline. Climatic, eustatic, and tectonic uplift controls on the overall system were simulated using a cellular automata algorithm with the following characteristics: (1) uplift as a function of position and time, as defined by the elevations and ages of corals; (2) climatic variations driven by insolation changes associated with Milankovitch cycles; (3) sea level fluctuations based on U/Th ages of coral terraces and eustatic data; and (4) parametrized fluvial erosion and deposition. Results imply that the fans and coralline limestones were generated in a setting in which the tectonic uplift rate decreased over the Quarternary to negligible values at present. Coralline limestones formed furing eustatic highstands when alluvium was trapped uspstream and wadis filled with debris. During lowstands, wadis cut into sedimentary deposits; coupled with continuing uplift, fans were dissected, leaving remnant surfaces, and wadi-related terraces were generated by down cutting. Only landforms from the past three to four eustatic sea level cycles (i.e., approximately 300 to 400 kyr) are likely

  7. Climatic, eustatic, and tectnoic controls on Quarternary deposits and landforms, Red Sea coast, Egypt

    NASA Technical Reports Server (NTRS)

    Arvidson, Raymond; Becker, Richard; Shanabrook, Amy; Luo, Wei; Sturchio, Neil; Sultan, Mohamed; Lofty, Zakaria; Mahmood, Abdel Moneim; El Alfy, Zeinhom

    1994-01-01

    The degree to which local climatic variations, eustatic sea level fluctuations, and tectonic uplift have influenced the development of Quaternary marine and fluvial landforms and deposits along the Red Sea coast, Eastern Desert, was investigated using a combination of remote sensing and field data, age determinations of corals, and numerical simulations. False color composites generated from Landsat Thematic Mapper and SPOT image data, digital elevation models derived from sterophotogrammetric analysis of SPOT data, and field observations document that a approximately 10-km wide swath inland from the coast is covered in many places with coalescing alluvial fans of Quaternary age. Wadis cutting through the fans exhibit several pairs of fluvial terraces, and wadi walls expose alluvium interbedded with corraline limestone deposits Further, three distinct coral terraces are evident along the coatline. Climatic, eustatic, and tectonic uplift controls on the overall system were simulated using a cellular automata algorithm with the following characteristics: (1) uplift as a function of position and time, as defined by the elevations and ages of corals; (2) climatic variations driven by insolation changes associated with Milankovitch cycles; (3) sea level fluctuations based on U/Th ages of coral terraces and eustatic data; and (4) parametrized fluvial erosion and deposition. Results imply that the fans and coralline limestones were generated in a setting in which the tectonic uplift rate decreased over the Quarternary to negligible values at present. Coralline limestones formed furing eustatic highstands when alluvium was trapped uspstream and wadis filled with debris. During lowstands, wadis cut into sedimentary deposits; coupled with continuing uplift, fans were dissected, leaving remnant surfaces, and wadi-related terraces were generated by down cutting. Only landforms from the past three to four eustatic sea level cycles (i.e., approximately 300 to 400 kyr) are likely

  8. Climatic, eustatic, and tectonic controls on Quaternary deposits and landforms, Red Sea coast, Egypt

    SciTech Connect

    Arvidson, R.; Becker, R.; Shanabrook, A.; Luo, W.; Sultan, M.; Sturchio, N.; Lotfy, Z.; Mahmood, A.M.; El Alfy, Z.

    1994-06-10

    The degree to which local climatic variations, eustatic sea level fluctuations, and tectonic uplift have influenced the development of Quaternary marine and fluvial landforms and deposits along the Red Sea coast, Eastern Desert, Egypt was investigated using a combination of remote sensing and field data, age determinations of corals, and numerical simulations. False color composites generated from Landsat Thematic Mapper and SPOT image data, digital elevation models derived from stereophotogrammetric analysis of SPOT data, and field observations document that a {approximately}10-km-wide swath inland from the coast is covered in many places with coalescing alluvial fans of Quaternary age. Wadis cutting through the fans exhibit several pairs of fluvial terraces, and wadi walls expose alluvium interbedded with coralline limestone deposits. Further, three distinct coral terraces are evident along the coastline. Climatic, eustatic, and tectonic uplift controls on the overall system were simulated using a cellular automata algorithm with the following characteristics: (1) uplift as a function of position and time, as defined by the elevations and ages of corals; (2) climatic variations driven by insolation changes associated with Milankovitch cycles; (3) sea level fluctuations based on U/Th ages of coral terraces and eustatic data; and (4) parameterized fluvial erosion and deposition. Results imply that the fans and coralline limestones were generated in a setting in which the tectonic uplift rate decreased over the Quaternary to negligible values at present. During lowstands, wadis cut into sedimentary deposits; coupled with continuing uplift, fans were dissected, leaving remnant surfaces, and wadi-related terraces were generated by down cutting. Only landforms from the past three to four eustatic sea level cycles (i.e., {approximately} 300 to 400 kyr) are likely to have survived erosion and deposition associated with fluvial processes. 33 refs., 18 figs., 2 tabs.

  9. Termination of carbonate platforms: Eustatic fluctuations in base level

    SciTech Connect

    Crevello, P. )

    1990-05-01

    Various processes can lead to the termination of carbonate platforms: tectonic foundering, eustatic drowning or exposure, local environmental stress, or changes in sedimentary regimes. In Liassic carbonate platforms of the High Atlas rift, Morocco, both tectonic foundering and eustatic base-level shifts are recorded in the platform stratigraphy. The stratigraphic signature of the eustatic base-level fluctuations reported here record subaerial exposure, transgressive sequences, and drowning of platforms. Regressive carbonate sequences record base-level lowering and exposure in the late Domerian. The sequences consist of progressive seaward shifts in facies belts, upward thinning in cycles and cycle bundles, cycle skipping (i.e., a decrease in number of cycles per bundle), and an increase in intensity of exposure features. Transgressive carbonate sequences mark the renewal of marine deposition across the platforms in early to middle Toarcian. These carbonates are comprised of amalgamated, noncyclic, top-truncated (i.e., erosional upper surfaces), subtidal, open-marine, oolitic and skeletal-rich (corals and megaladonts) lithofacies. Exposure surfaces separating subtidal lithofacies are evidence of fluctuating eustatic base level. Drowning of the platform along the Sahara craton is marked by the change to low-energy deposits containing the bivalve Gryphaea sp., which passes abruptly upward into downlapping( ) ammonite-bearing (middle Toarcian Bifrons zone, to Aalenian) marine shales. Over 100 m of marine shales were deposited over the Liassic platform before carbonate platform deposition resumed. Drowning of an isolated axial-rift platform, Jebel Bou Dahar, is represented by only a thin (2-3 m) condensed sequence (middle Toarcian( ) to early Aalenian) of glauconitic ammonite-brachiopod floatstones.

  10. Humboldt Bay Vertical Reference System Working Group: unraveling tectonic and eustatic factors of sea level rise in northern California, Humboldt Bay

    NASA Astrophysics Data System (ADS)

    Williams, T. B.; Anderson, J. K.; Burgette, R. J.; Gilkerson, W.; Hemphill-Haley, M.; Leroy, T. H.; Patton, J. R.; Southwick, E.; Stallman, J.; Weldon, R. J.

    2012-12-01

    Sea-level rise is a critical factor in managing estuarine ecosystems, maintaining public infrastructure, and mitigating geologic hazards along north coastal California. The coastal region between Fort Bragg, California and Vancouver Island experiences ongoing land-level changes due to Cascadia subduction zone tectonics. These tectonic land-level changes sufficiently modify relative sea level such that sea-level rise cannot be accurately estimated without determining the tectonic contribution. We use tide gages and precise level-loop surveys to observe modern land and water surface elevations around Humboldt Bay. These modern data, combined with historic survey data, will be used to deconfound the various factors contributing to relative sea level change. Independent analysis of existing NOAA tide gages and EarthScope CGPS stations indicate 2.5 mm/yr of land subsidence near Humboldt Bay and 2 mm/yr of land uplift in Crescent City. Presuming the bulk of the strain accumulation is due to the southern portion of the Cascadia subduction zone, these data suggest Humboldt Bay is west of the locked zone, not to the east as previously reported by several researchers.

  11. Paleo-surfaces of glacio-eustatically forced aggradational successions in the coastal area of Rome: Assessing interplay between tectonics and sea-level during the last ten interglacials

    NASA Astrophysics Data System (ADS)

    Marra, Fabrizio; Florindo, Fabio; Anzidei, Marco; Sepe, Vincenzo

    2016-09-01

    Recently acquired geochronological and stratigraphic data provide new information on the sedimentary successions deposited by the Paleo-Tiber River in the coastal and near-coastal area of Rome in consequence of the glacio-eustatic changes, allowing to better define their inner geometry and palaeogeographic spatial distribution. In the present work we use this revised sedimentary dataset to provide a geochronologically constrained and tectonically adjusted record of paleo sea-level indicators. Aimed at this scope, we review literature data acquired in the last 35 years and using the new geochronological constraints we pinpoint the coastal-to-fluvial terraces of MIS 5 and MIS 7, mapping their relic surfaces in an area of 30 km along the coast north and south of the Tiber River mouth, and 20 km inland of the fluvial valleys of Tiber and Aniene rivers. The geometry of these paleo-surfaces provides constraints on the relative elevation of the sea-level during the last interglacials and on the uplift rates in this region during the last 200 ka. In particular, we recognize the previously undetected terraces of MIS 5.3 and MIS 5.1 interstadials, and we assess their spatial relationship with respect to MIS 5.5, providing important information on sea-level oscillations during this time span. Comparison with sea-level indicators provided by previous aggradational successions deposited during past interglacials spanning MIS 9 through MIS 21 in the coastal area of Rome, also allows us to reconstruct the tectonic history and investigate its relationships with the Middle-Pleistocene volcanic activity of the Roman Comagmatic Region along the Tyrrhenian Sea margin of Italy in the last 900 ka.

  12. Bay sedimentation as controlled by regional crustal behaviour, local tectonics and eustatic sea-level changes: Coquimbo Formation (Miocene Pliocene), Bay of Tongoy, central Chile

    NASA Astrophysics Data System (ADS)

    Le Roux, J. P.; Olivares, Danisa M.; Nielsen, Sven N.; Smith, Norman D.; Middleton, Heather; Fenner, Juliane; Ishman, Scott E.

    2006-02-01

    The north-facing Bay of Tongoy in central Chile is flanked by topographic highs in the west and east. During the Miocene and Pliocene, the bay extended inland at least 30 km farther south than a present. It was filled with muds, sands, coquinas and gravel during a series of transgressions and regressions related to regional and local tectonic movements combined with global sea-level variations. 87Sr/ 86Sr and microfossil dating indicates transgressions between 11.9-11.2 Ma, 10.1-9.5 Ma, 9.0-7.3 Ma, 6.3-5.3 Ma, 4.3-2.2 Ma and 1.7-1.4 Ma. The regional tectonic behaviour of the crust shows general uplifting from 10.5 Ma to 6.9 Ma, associated with subduction of the Juan Fernández Ridge (JFR) beneath this part of the continent. Subsidence followed between 6.9 and 2.1 Ma, in the wake of the southeastward-migrating JFR. The subsequent subduction of an oceanic plateau similar to the JFR caused rapid uplift that led to the final emergence of the bay above sea level. The Puerto Aldea normal fault along the western limit of the study area was reactivated during the regional uplift and subsidence events, with reverse faulting occurring during the latter phase. Sporadic fault reactivation probably triggered the rapid changes in water depth reflected in the recorded vertical succession of facies.

  13. Effects of eustatic sea-level change, ocean dynamics, and iron fertilization on atmospheric pCO2 and seawater composition over the last 130 000 years

    NASA Astrophysics Data System (ADS)

    Wallmann, K.; Schneider, B.; Sarnthein, M.

    2015-06-01

    We developed and employed an earth system model to explore the forcings of atmospheric pCO2 change and the chemical and isotopic evolution of seawater over the last glacial cycle. Concentrations of dissolved phosphorus, reactive nitrogen, molecular oxygen, dissolved inorganic carbon (DIC), total alkalinity (TA), 13C-DIC and 14C-DIC were calculated for 24 ocean boxes. The bi-directional water fluxes between these model boxes were derived from a 3-D circulation field of the modern ocean (Opa 8.2, NEMO) and tuned such that tracer distributions calculated by the box model were consistent with observational data from the modern ocean. To model the last 130 kyr, we employed records of past changes in sea-level, ocean circulation, and dust deposition. According to the model, about half of the glacial pCO2 drawdown may be attributed to marine regressions. The glacial sea-level low-stands implied steepened ocean margins, a reduced burial of particulate organic carbon, phosphorus, and neritic carbonate at the margin seafloor, a decline in benthic denitrification, and enhanced weathering of emerged shelf sediments. In turn, they led to a distinct rise in the standing stocks of DIC, TA, and nutrients in the global ocean, promoted the glacial sequestration of atmospheric CO2 in the ocean, and added 13C- and 14C-depleted DIC to the ocean as recorded in benthic foraminifera signals. The other half of the glacial drop in pCO2 was linked to reduced deep ocean dynamics, a shoaling of Atlantic meridional overturning circulation, and a rise in iron fertilization. The increased transit time of deep waters in the glacial ocean led to significant 14C depletions with respect to the atmosphere. The deglacial rapid and stepwise rise in atmospheric pCO2 was induced by upwelling both in the Southern Ocean and subarctic North Pacific and promoted by a drop in dust-borne iron discharge to the Southern Ocean. The deglacial sea-level rise led to a gradual decline in nutrient, DIC, and TA stocks

  14. Eustatic and climatic control on the Upper Muschelkalk Sea (late Anisian/Ladinian) in the Central European Basin

    NASA Astrophysics Data System (ADS)

    Franz, M.; Kaiser, S. I.; Fischer, J.; Heunisch, C.; Kustatscher, E.; Luppold, F. W.; Berner, U.; Röhling, H.-G.

    2015-12-01

    The Upper Muschelkalk in the Central European Basin (CEB) is a key example of eustatic and climatic controls on inland seas. The late Anisian rapid transgression from Tethyan waters culminated in a large semi-enclosed inland sea stretching across the CEB. Subsequently, the slow but successive retreat in the early Ladinian resulted in a small remnant sea. The pronounced stratal pattern architectures are translated into a framework of 3rd- and 4th-order T-R sequences. The latest Illyrian 3rd-order maximum flooding surface corresponds to maximum abundances of carbonates and marine phytoplankton. An euryhaline marine ecology is indicated by prasinophycean algae dominating over acritarchs and δ18OP values of 18.9-22.4‰ VSMOW corresponding to Tethyan references. During the 3rd-order regressive phase successive freshening up to hyposaline conditions is indicated by up to 3‰ depleted δ18OP values, shifts to more radiogenic 87Sr/86Sr ratios and maximum abundances of terrestrial palynomorphs. Likewise, 4th-order T-R sequences are constrained by commutated stratal pattern architectures, palynofacies and geochemistry. The favourable correlation of middle Triassic 3rd-order sequences of Tethyan and peri-Tethyan basins demonstrate the principle control of circum-Tethyan eustatic cycles. 4th-order sequences are evident and, although not yet correlatable in detail, indicate 106-year scale eustatic cycles which may be attributed to glacioeustatic sea-level changes. The subordinated control of arid to semiarid low latitude and semihumid to humid temperate mid latitude climates affected the Upper Muschelkalk Sea in particular during 4th-order sea-level lowstands. Substantial fresh water input from Scandinavian sources caused temporal stratification leading to stagnant bottom waters and/or sediments as indicated by palynofacies and U/Th and Ni/Co redox indices. The herein reconstructed middle Triassic zonal climates are in agreement to previously published Late Triassic zonal

  15. Effects of eustatic sea-level change, ocean dynamics, and nutrient utilization on atmospheric pCO2 and seawater composition over the last 130 000 years: a model study

    NASA Astrophysics Data System (ADS)

    Wallmann, K.; Schneider, B.; Sarnthein, M.

    2016-02-01

    We have developed and employed an Earth system model to explore the forcings of atmospheric pCO2 change and the chemical and isotopic evolution of seawater over the last glacial cycle. Concentrations of dissolved phosphorus (DP), reactive nitrogen, molecular oxygen, dissolved inorganic carbon (DIC), total alkalinity (TA), 13C-DIC, and 14C-DIC were calculated for 24 ocean boxes. The bi-directional water fluxes between these model boxes were derived from a 3-D circulation field of the modern ocean (Opa 8.2, NEMO) and tuned such that tracer distributions calculated by the box model were consistent with observational data from the modern ocean. To model the last 130 kyr, we employed records of past changes in sea-level, ocean circulation, and dust deposition. According to the model, about half of the glacial pCO2 drawdown may be attributed to marine regressions. The glacial sea-level low-stands implied steepened ocean margins, a reduced burial of particulate organic carbon, phosphorus, and neritic carbonate at the margin seafloor, a decline in benthic denitrification, and enhanced weathering of emerged shelf sediments. In turn, low-stands led to a distinct rise in the standing stocks of DIC, TA, and nutrients in the global ocean, promoted the glacial sequestration of atmospheric CO2 in the ocean, and added 13C- and 14C-depleted DIC to the ocean as recorded in benthic foraminifera signals. The other half of the glacial drop in pCO2 was linked to inferred shoaling of Atlantic meridional overturning circulation and more efficient utilization of nutrients in the Southern Ocean. The diminished ventilation of deep water in the glacial Atlantic and Southern Ocean led to significant 14C depletions with respect to the atmosphere. According to our model, the deglacial rapid and stepwise rise in atmospheric pCO2 was induced by upwelling both in the Southern Ocean and subarctic North Pacific and promoted by a drop in nutrient utilization in the Southern Ocean. The deglacial sea-level

  16. A "chaos" of Phanerozoic eustatic curves

    NASA Astrophysics Data System (ADS)

    Ruban, Dmitry A.

    2016-04-01

    The knowledge of eustasy has changed during the past two decades. Although there is not any single global sea-level curve for the entire Phanerozoic, new curves have been proposed for all periods. For some geological time intervals, there are two and more alternative reconstructions, from which it is difficult to choose. A significant problem is the available eustatic curves are justified along different geological time scales (sometimes without proper explanations), which permits to correlate eustatic events with the possible error of 1-3 Ma. This degree of error permits to judge about only substage- or stage-order global sea-level changes. Close attention to two geological time slices, namely the late Cambrian (Epoch 3‒Furongian) and the Late Cretaceous, implies that only a few eustatic events (6 events in the case of the late Cambrian and 9 events in the case of the Late Cretaceous) appear on all available alternative curves for these periods, and different (even opposite) trends of eustatic fluctuations are shown on these curves. This reveals significant uncertainty in our knowledge of eustasy that restricts our ability to decipher factors responsible for regional transgressions and regressions and relative sea-level changes. A big problem is also inadequate awareness of the geological research community of the new eustatic developments. Generally, the situation with the development and the use of the Phanerozoic eustatic reconstructions seems to be ;chaotic;. The example of the shoreline shifts in Northern Africa during the Late Cretaceous demonstrates the far-going consequences of this situation. The practical recommendations to avoid this ;chaos; are proposed. Particularly, these claim for good awareness of all eustatic developments, their critical discussion, and clear explanation of the employed geological time scale.

  17. Tors, Eustatic Shorelines, and Mammoths: Evidence Against Ice Sheets on Wrangel Island, East Siberian/Chukchi Seas

    NASA Astrophysics Data System (ADS)

    Gualtieri, L.; Vartanyan, S.; Brigham-Grette, J.; Anderson, P.

    2001-12-01

    Assumed glacial flutings on the Chukchi Rise (Polyak et al., 2001) have reinvigorated hypotheses concerning the past presence of the same type of ice sheet or ice shelf on the Chukchi and/or East Siberian Sea shelf. Fieldwork on wrangle Island has been aimed at determining the glacial and sea level history of this geographically strategic island to address these various hypotheses. Cosmogenic isotope ages (Be and Al) on bedrock are all older that 35 ka , at a minimum, the rates of pervasive pariglacial processes. Tors, commonly forming columns 10 m high, are ubiquitous throughout the mountains of Wrangel Island. Eustatic shorelines (and not glacioisostatic shorelines) across the northern tundra plain marked by remnant marine sediments and ancient barrier beaches up to 40 m above seal level are all older than the range of radiocarbon dating and yield amino acid age estimates (D/L Aspartic as well as aIle/Ile) in excess of 400-500 ka, similar to sediments found in the Alaskan North Slope. Radiocarbon dates on mammoth borres, teeth and tusks and other animals (rhinos, bison) yield ages that range continuously through time from >38 ka to 3700 years ago indicating the local presence of large mammals during the Last Glacial Maximum (LGM) and most of the Holocene. These data preclude the presence of an ice sheet during the LGM and probably over the past half million years. Glacial ice extent on the island during the LGM was limited to a few small north facing cirque glaciers. The flutings on the Chukchi Rise could not have been formed by an ice sheet over or near Wrangel Island in at least the last four or five major glacial/interglacial cycles.

  18. Record of glacial-eustatic sea-level fluctuations in complex middle to late Pennsylvanian facies in the Northern Appalachian Basin and relation to similar events in the Midcontinent basin

    NASA Astrophysics Data System (ADS)

    Belt, Edward S.; Heckel, Philip H.; Lentz, Leonard J.; Bragonier, William A.; Lyons, Timothy W.

    2011-06-01

    Pennsylvanian cycles in the Northern Appalachian Basin (NAB) were historically considered to result from delta-lobe switching, and more recently from sea-level fluctuation with sandy deltas prograding during highstand. These interpretations are revised using new data from cores and outcrop exposures. Thick (> 5 m) channel deposits with a marked erosion surface at their base cutting down across previous cycles are re-interpreted as incised valley fill (IVF) deposits in paleovalleys, because the basal erosion surfaces are widespread, and thus reflect a record of lowstand. Most common are simple paleovalleys that contain mainly sandy fluvial deposits. Compound paleovalleys with sequence boundaries above the basal erosion surface, contain terrestrial, estuarine, and marine deposits. Early to late highstand deposits in interfluvial parts of the cycles are dominated by shale and mudstone, with paleosols, coals, and local non-marine limestone, which reflect floodbasin to lacustrine conditions. These reinterpretations are applied to previously and newly recognized cycles in ascending order: Upper Kittanning, Lower Freeport, Upper Freeport Leader (new), Upper Freeport, Piedmont (new), Mahoning, Mason interval (locally includes Upper New Galilee in the north), and Brush Creek, across a 300-km arc in the Northern Appalachian Basin. These deposits accumulated in a 'high shelf' setting that experienced fewer marine transgressions, and were interrupted by more frequent exposure and downcutting, in contrast to the thicker and more complete succession with more numerous marine units in the Midcontinent. Magnitudes of highstand transgressions into this basin, deduced from the up-dip extent of marine and brackish fossil assemblages, were greatest for the Brush Creek, less so for the Upper Kittanning and Mahoning, and least for the Lower Freeport, Upper Freeport Leader, Piedmont, and Mason. The anomalous basin-wide fresh-water roofshales and equivalents of the Upper Freeport coal may

  19. Sea-Level Changes during the Tertiary.

    ERIC Educational Resources Information Center

    Vail, Peter R.; Hardenbol, Jan

    1979-01-01

    Discussed are research procedures undertaken to determine the magnitude and timing of eustatic sea-level changes during the Tertiary Period. Data now becoming available give scientists a knowledge of conditions that may have been conducive to the formation of petroleum. (BT)

  20. Sea-Level Changes during the Tertiary.

    ERIC Educational Resources Information Center

    Vail, Peter R.; Hardenbol, Jan

    1979-01-01

    Discussed are research procedures undertaken to determine the magnitude and timing of eustatic sea-level changes during the Tertiary Period. Data now becoming available give scientists a knowledge of conditions that may have been conducive to the formation of petroleum. (BT)

  1. 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

  2. Sea level changes in the holocene

    NASA Astrophysics Data System (ADS)

    Kidson, C.

    Over the last 30 years the emphasis in studies of the recovery from low last glaciation sea levels has changed significantly. The search for a eustatic sea level curve having global relevance has ended. Studies into the rheology of the earth's crust, and recognition that the geoid has not remained stable over time, have resulted in the recognition that there must have been regional differences in eustatic response to deglaciation. As a part of this re-appraisal there has been a growing appreciation that crustal isostatic response to the removal of the weight of ice sheets has been accompanied by a consequential hydro-isostatic response, particularly in the areas of the shelf seas. In the later part of the post-war period attention has additionally been focussed on the much greater potential for error over the whole field of palaeoenvironmental reconstruction in the Holocene, including not only errors in dating, but also a large number of possible sources of errors in heighting. As a result of this, an increasing number of scientists are withholding judgement on the nature of sea level rise and, more particularly, on the problem of higher than present late Holocene eustatic sea levels. The problems outstanding in the early 1960s have not yet been resolved but the bases of uncertainty have changed.

  3. Sea Level Rise and Consequences for Navigable Coastal Inlets

    DTIC Science & Technology

    2009-01-01

    Rosati, Ph.D., P.E., and Nicholas C. Kraus, Ph.D. U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory 3909 Halls Ferry...ac- company a rise in sea level. Means of planning for and coping with this process are also discussed. SEA LEVEL RISE Global or eustatic sea...Research and Development Center,Coastal and Hydraulics Laboratory,3909 Halls Ferry Rd,Vicksburg,MS,39180 8. PERFORMING ORGANIZATION REPORT NUMBER 9

  4. Revisiting Tectonic Corrections Applied to Pleistocene Sea-Level Highstands

    NASA Astrophysics Data System (ADS)

    Creveling, J. R.; Mitrovica, J. X.; Hay, C.; Austermann, J.; Kopp, R. E.

    2015-12-01

    The robustness of stratigraphic- and geomorphic-based inferences of Quaternary peak interglacial sea levels — and equivalent minimum continental ice volumes — depends on the accuracy with which highstand markers can be corrected for vertical tectonic displacement. For sites that preserve a Marine Isotope Stage (MIS) 5e sea-level highstand marker, the customary method for estimating tectonic uplift/subsidence rate computes the difference between the local elevation of the highstand marker and a reference eustatic (i.e., global mean) MIS 5e sea-level height, typically assumed to be +6 m, and then divides this height difference by the age of the highstand marker. This rate is then applied to correct the elevation of other observed sea-level markers at that site for tectonic displacement. Subtracting a reference eustatic value from a local MIS 5e highstand marker elevation introduces two potentially significant errors. First, the commonly adopted peak eustatic MIS 5e sea-level value (i.e., +6 m) is likely too low; recent studies concluded that MIS 5e peak eustatic sea level was ~6-9 m. Second, local peak MIS 5e sea level was not globally uniform, but instead characterized by significant departures from eustasy due to glacial isostatic adjustment (GIA) in response to successive glacial-interglacial cycles and excess polar ice-sheet melt relative to present day. We present numerical models of GIA that incorporate both of these effects in order to quantify the plausible range in error of previous tectonic corrections. We demonstrate that, even far from melting ice sheets, local peak MIS 5e sea level may have departed from eustasy by 2-4 m, or more. Thus, adopting an assumed reference eustatic value to estimate tectonic displacement, rather than a site-specific GIA signal, can introduce significant error in estimates of peak eustatic sea level (and minimum ice volumes) during Quaternary highstands (e.g., MIS 11, MIS 5c and MIS 5a).

  5. The Cambrian eustatic signal: Not so grand

    SciTech Connect

    Cowan, C.A.; James, N.P. )

    1990-05-01

    Efforts to decipher potential high-frequency (fourth- and fifth-order) eustatic signals within third-order grand cycles in Cambrian strata of western Newfoundland have yielded a surprising result: the conspicuous, large-scale stratigraphic rhythms, grand cycles, were not principally a bathymetric phenomenon, grand cycles, i.e., the stratigraphic repetition of tens-of-meters-thick lithosomes, which are alternately carbonate and terrigenous clastic rich, are widely cited as evidence for lower Paleozoic third-order eustatic fluctuations. Evidence from Middle to Upper Cambrian platform strata in western Newfoundland indicates that grand cyclicity in this area was not simply a response to sea level change. Instead, the stratigraphic signal of eustasy is marked by the presence of terrigenous clastics in an otherwise carbonate-prone succession. Detailed facies analysis reveals that both terrigenous and carbonate lithosomes are locally constructed of predictable, meter-scale, coarsening-upward cycles. Lithofacies constituting meter-scale cycles in both lithosomes are bathymetrically indistinguishable with respect to environmental energy, ichnofauna, and exposure index. Meter-scale cycles in either lithosome are typically capped by the same lithology, precluding contemporaneous generation of carbonate vs. terrigenous cycles along some presumed bathymetric gradient. Obvious lithologic differences between carbonate and terrigenous meter-scale cycles obscure their common origin. Terrigenous cycles are best explained by the incursion of siliciclastic fines into a shallow-water carbonate environment irrespective of sea level change.

  6. The Sea Level Conundrum: Insights From Paleo Studies

    NASA Astrophysics Data System (ADS)

    Siddall, Mark; Clark, Peter; Thompson, Bill; Waelbroeck, Claire; Gregory, Jonathan; Stocker, Thomas

    2009-03-01

    Empirical Constraints on Future Sea Level Rise; Bern, Switzerland, 25-29 August 2008; Eustatic sea level (ESL) rise during the 21st century is perhaps the greatest threat from climate change, but its magnitude is contested. Geological records identify examples of nonlinear ice sheet response to climate forcing, suggesting a strategy for refining estimates of 21st-century sea level change. In August 2008, Past Global Changes (PAGES), International Marine Past Global Change Study (IMAGES), and the University of Bern cosponsored a workshop to address this possibility. The workshop highlighted several ways that paleoceanography studies can place limits on future sea level rise, and these are enlarged upon here.

  7. A chronology of Paleozoic sea-level changes.

    PubMed

    Haq, Bilal U; Schutter, Stephen R

    2008-10-03

    Sea levels have been determined for most of the Paleozoic Era (542 to 251 million years ago), but an integrated history of sea levels has remained unrealized. We reconstructed a history of sea-level fluctuations for the entire Paleozoic by using stratigraphic sections from pericratonic and cratonic basins. Evaluation of the timing and amplitude of individual sea-level events reveals that the magnitude of change is the most problematic to estimate accurately. The long-term sea level shows a gradual rise through the Cambrian, reaching a zenith in the Late Ordovician, then a short-lived but prominent withdrawal in response to Hirnantian glaciation. Subsequent but decreasingly substantial eustatic highs occurred in the mid-Silurian, near the Middle/Late Devonian boundary, and in the latest Carboniferous. Eustatic lows are recorded in the early Devonian, near the Mississippian/Pennsylvanian boundary, and in the Late Permian. One hundred and seventy-two eustatic events are documented for the Paleozoic, varying in magnitude from a few tens of meters to approximately 125 meters.

  8. The sea-level fingerprints of ice-sheet collapse during interglacial periods

    NASA Astrophysics Data System (ADS)

    Hay, Carling; Mitrovica, Jerry X.; Gomez, Natalya; Creveling, Jessica R.; Austermann, Jacqueline; E. Kopp, Robert

    2014-03-01

    Studies of sea level during previous interglacials provide insight into the stability of polar ice sheets in the face of global climate change. Commonly, these studies correct ancient sea-level highstands for the contaminating effect of isostatic adjustment associated with past ice age cycles, and interpret the residuals as being equivalent to the peak eustatic sea level associated with excess melting, relative to present day, of ancient polar ice sheets. However, the collapse of polar ice sheets produces a distinct geometry, or fingerprint, of sea-level change, which must be accounted for to accurately infer peak eustatic sea level from site-specific residual highstands. To explore this issue, we compute fingerprints associated with the collapse of the Greenland Ice Sheet, West Antarctic Ice Sheet, and marine sectors of the East Antarctic Ice Sheet in order to isolate regions that would have been subject to greater-than-eustatic sea-level change for all three cases. These fingerprints are more robust than those associated with modern melting events, when applied to infer eustatic sea level, because: (1) a significant collapse of polar ice sheets reduces the sensitivity of the computed fingerprints to uncertainties in the geometry of the melt regions; and (2) the sea-level signal associated with the collapse will dominate the signal from steric effects. We evaluate these fingerprints at a suite of sites where sea-level records from interglacial marine isotopes stages (MIS) 5e and 11 have been obtained. Using these results, we demonstrate that previously discrepant estimates of peak eustatic sea level during MIS5e based on sea-level markers in Australia and the Seychelles are brought into closer accord.

  9. Sea level rise and coastal erosion

    NASA Astrophysics Data System (ADS)

    Leatherman, S. P.; Zhang, K.; Douglas, B. C.

    2003-04-01

    One of the most certain consequences of global warming is an increase of global (eustatic) sea level. The resulting inundation from rising seas will heavily impact low-lying areas; at least 100 million persons live within one meter of mean sea level and are at increased risk in the coming decades. The very existence of some island states and deltaic coasts is threatened by sea level rise. An additional threat affecting some of the most heavily developed and economically valuable real estate will come from an exacerbation of sandy beach erosion. As the beach is lost, fixed structures nearby are increasingly exposed to the direct impact of storm waves, and will ultimately be damaged or destroyed unless expensive protective measures are taken. It has long been speculated that the underlying rate of long-term sandy beach erosion is two orders of magnitude greater than the rate of rise of sea level, so that any significant increase of sea level has dire consequences for coastal inhabitants. We present an analysis of a large and consistent database of shoreline positions and sea levels to show that there is an underlying highly multiplicative relation of sandy beach erosion to sea level rise. This result means that the already-severe coastal erosion problems witnessed in the 20th century will be exacerbated in the 21st century under plausible global warming scenarios.

  10. Bajocian-Bathonian (Middle Jurassic) sea-level changes in northeastern Egypt: Synthesis and further implications

    NASA Astrophysics Data System (ADS)

    Ruban, Dmitry A.; Sallam, Emad S.

    2016-08-01

    The global eustatic developments can benefit significantly from properly acquired regional information. Summarizing the available interpretations of the relative sea-level changes from two areas in northeastern Egypt, namely Gebel Maghara and Khashm El-Galala, allows better understanding of the Middle Jurassic sea-level changes. It is established that the Bajocian-Bathonian relative sea-level changes in these areas were coherent. The magnitude of changes was lower in the Bajocian than in the Bathonian. Significant sea-level rises occurred at the Bajocian-Bathonian and middle-late Bathonian transitions, and there was a clear tendency toward sea-level rise throughout the studied time interval. This evidence favors one of the two alternative global eustatic reconstructions that implies "stable" position of the shoreline in the Bajocian and general tendency to eustatic rise throughout the Jurassic. The tectonic regime of northeastern Egypt in the Middle Jurassic provided for strong eustatic control of the relative sea-level changes. The possible influence of hotspot activity is questionable. Filling the accommodation space with materials derived from the eroded continent may explain some sea-level falls that are regionally documented.

  11. Land to sea record of the mega-eustatic cycle including the Messinian Salinity Crisis in the Mediterranean Andalusia

    NASA Astrophysics Data System (ADS)

    Jouannic, Gwénaël.; Gorini, Christian; Jolivet, Laurent; Clauzon, Georges; Suc, Jean-Pierre; Gargani, Julien; Melinte-Dobrinescu, Mihaela Carmen; Meyer, Bertrand

    2010-05-01

    The outstanding event of the Messinian Salinity Crisis is very well documented in the onshore Sorbas and Vera Andalusian basins where its process and chronology are now well-known (Gautier et al., 1994, Krijgsman et al., 1999; Clauzon et al., 2009). The detailed study of these basins was at the origin of the two-step scenario of the Messinian salinity crisis (Clauzon et al., 1996) which clarified several aspects of the "deep desiccated basin" model of Hsü et al. (1973). The scenario in two steps (first step: evaporite deposition in Mediterranean marginal basins between 5.96 and 5.60 Ma; second step: evaporites deposition between 5.60 and 5.46 Ma in the almost dried up Mediterranean central basins, and subaerial erosion and deep canyons formation on the margins; Clauzon et al., 1996, 2005, 2008) has now the broadest consensus within the scientific community (CIESM, 2008). The Sorbas and Vera basins present all the markers in terms of sequence stratigraphy whatever these events were caused by moderate or excessive sea-level changes: 1, coral reefs, showing the relative sea level before the crisis; 2, gypsum (120 m in thickness) deposited during the first sea level drop (about 150 m) between 5.96 and 5.60 Ma; 3, the widespread erosion surface during the maximum sea level fall(ca. -1500 m); 4, the re-flooding at 5.46 Ma These onshore markers have also been recorded in offshore seismic profiles, allowing a continuous mapping of the Messinian canyons from land to sea. These onshore and offshore areas (Mauffret et al., 2007; Ammar et al., 2008) have also undergone a tectonics according to their proximity to the Betic cordillera (the south of the Sorbas Basin was more affected for example). Stratigraphic markers of the messinian crisis are powerful tools to reconstruct the tectonic events since 5 Ma. This work has made possible the calibration of tectonic deformations on south Andalusia present-day onshore and offshore domains. Ammar, A., Mauffret, A., Gorini, C., Jabour

  12. Lithologic prediction from the stratal architecture of Plio-Pleistocene Gulf of Mexico: Are the eustatic depositional systems tract models adequate

    SciTech Connect

    Butler, M.L.; Self, G.A. )

    1991-03-01

    Climatic/eustatic cycles of the Plio-Pleistocene have been defined in the northern Gulf of Mexico and precisely tied to their associated sequences and lithologies by means of graphic correlation. This framework has provided the data necessary for a detailed empirical evaluation of the eustatic depositional systems tract models. The key to this evaluation is a eustatic sea-level curve derived from fossil and isotope data. A curve of this type has been defined for several sequences. Using this eustatic curve the actual lithofacies and position of the various systems tracts were directly compared to those predicted by the models. The evaluation of the data with respect to eustatic sea level yielded conclusions that are significantly different from those predicted by the models. The evaluation of the data with respect to eustatic sea level yielded conclusions that are significantly different from those predicted by the model. The most significant of these differences are: (1) significant amounts of sand were deposited in deep water during transgressive and highstand intervals; (2) the observed vertical succession of eustatic depositional systems tracts within a given sequence are transgressive, highstand, and lowstand, and (3) factors other than eustacy have been the dominant influence on facies distribution within the Plio-Pleistocene sequences studied. These results demonstrate that depositional systems tracts and internal facies distribution could not be adequately described by a single model. Therefore, sequence stratigraphic analysis should be empirically based and conducted within the context of the basin, instead of being model driven.

  13. Ice volume and sea level during the last interglacial.

    PubMed

    Dutton, A; Lambeck, K

    2012-07-13

    During the last interglacial period, ~125,000 years ago, sea level was at least several meters higher than at present, with substantial variability observed for peak sea level at geographically diverse sites. Speculation that the West Antarctic ice sheet collapsed during the last interglacial period has drawn particular interest to understanding climate and ice-sheet dynamics during this time interval. We provide an internally consistent database of coral U-Th ages to assess last interglacial sea-level observations in the context of isostatic modeling and stratigraphic evidence. These data indicate that global (eustatic) sea level peaked 5.5 to 9 meters above present sea level, requiring smaller ice sheets in both Greenland and Antarctica relative to today and indicating strong sea-level sensitivity to small changes in radiative forcing.

  14. Local sea level change and future of Louisiana coast

    SciTech Connect

    Nummedal, D.

    1983-09-01

    The relative elevation of sea and land has been changing through time in response to two fundamentally different groups of factors. Global factors include changes in the volume of the ocean basins owing to tectonic processes and changes in the total amount of ocean water due to glaciation. Local factors include subsidence of continental margins and compaction of recent sediments. Over this century, global sea level (eustatic) appears to have been rising at a rate of 1.2 mm per year. Along the south-central Louisiana coast the land surface appears to be sinking at a rate of about 8 mm per year. Recent global climatic modeling suggests strongly that we are about to enter a period of rapidly accelerating warming due to increased amount of carbon dioxide in the atmosphere. As a consequence, eustatic sea level rise is predicted to accelerate because of both steric expansion of the ocean water and continued melting of polar ice caps. For the next 40 years the eustatic sea level rise may average 10 mm per year. The local relative sea level in coastal Louisiana would therefore rise at about twice its present rate over this time period. The numbers presented above are average value for the Louisiana coastal plain. Local variability in subsidence rate appear to be related to the thickness of Holocene sediments. The highest rates of subsidence are found in the modern Mississippi (birdfoot) delta and in coastal Terrebonne Parish above the late Pleistocene Mississippi trench; in both areas the Holocene section is in excess of 200 m (650 ft) thick. The high rate of local sea level rise along the Louisiana coast makes it imperative that plans for coastal development and protection consider the long-term consequences of sea level change.

  15. Sea level data and techniques for detecting vertical crustal movements

    NASA Technical Reports Server (NTRS)

    Lennon, G. W.

    1978-01-01

    An attempt is made to survey problems, requirements, and the outlook for the future in the study of sea level time series so as to determine the relative movement of land and sea levels. The basic aim is to eliminate from the record the contributions from whatever marine dynamic phenomena respond to treatment, allowing the secular element to be identified with optimum clarity. Nevertheless the concept of sea level perturbation varies according to regional experience. The recent work of the Permanent Service for Mean Sea Level helps to eliminate geodetic noise from the series and makes it possible, perhaps, to treat the global mean sea level data bank so as to define eustatic changes in ocean volume which, in the present context, may be regarded as the final goal, allowing the identification of vertical crustal motion itself.

  16. Can eustatic charts go beyond first-order? Insights from the Permo-Triassic

    NASA Astrophysics Data System (ADS)

    Guillaume, Benjamin; Monteux, Julien; Pochat, Stéphane; Husson, Laurent; Choblet, Gaël

    2016-04-01

    To the first order, eustatic charts are in accord with our understanding of the geodynamic processes that control sea level. By extrapolation, second-order features are also thought to obey to the same rules, and are thus often taken for granted. But this assumption may be jeopardized by a close examination of a characteristic example. The Permo-Triassic period is characteristic for both its purported eustatic signal and its geodynamic and climatic setting are well defined and contrasted. Both the fragmentation of the Pangean supercontinent and the late Paleozoic melting of ice sheets argue for a rise of the eustatic sea level (ESL) whereas eustatic charts show the opposite. Here we review the possible mechanisms that could explain the apparent sea level low, and find that some of them do lower the ESL while others instead only modify the referential, either uplifting continents or tilting the margins where the control points are located. In the first category, we find that (i) dynamic deflections of the Earth surface above subduction zones and their location with respect to continents primarily control absolute sea level while the Pangean supercontinent forms and breaks up, (ii) endorheism that ubiquitously developed at the time of Pangean aggregation also contributed to lowering the ESL by storing water out of the oceanic reservoir. In the second category, we show that (i) the thermal uplift associated to supercontinental insulation and (ii) the dynamic uplift associated with the emplacement of a superplume both give rates of change in the range of long-term changes of ESL. We also show that (iii) the dynamic tilting of continental margins not only produces apparent sea level changes, but also modifies the absolute sea level, which in turn may end up in the paradoxical situation wherein fingerprints of ESL drop are found in the geological record whereas ESL is actually rising. We conclude that the establishment of second to third order absolute sea level changes

  17. New evidence for the Holocene sea-level high from the inner shelf, central Great Barrier Reef, Australia

    SciTech Connect

    Beaman, R.; Larcombe, P.; Carter, R.M. . Marine Geophysical Lab.)

    1994-10-03

    Radiocarbon dates from fossil oyster beds of intertidal origin on Magnetic island, north Queensland indicate that the local Holocene maximum of relative sea level was attained no later than 5660 [+-] 50 B.P. (conventional uncorrected age) and remained at 1.6--1.7 m above modern levels until 4040 [+-] 50 B.P. Given the tectonic stability of the area, this implies that eustatic sea level remained at its Holocene peak for at least ca. 1600 yr. The new high-precision sea-level data indicate sea levels 1--5 m higher than those of the same age inferred from buried mangrove deposits on the inner shelf in north Queensland. Uncertainties in deriving relative sea level from such mangrove deposits may be a significant source of error in worldwide attempts to distinguish the eustatic and crustal warping components of relative sea-level change, especially in the tropics.

  18. Facies analysis at Triassic/Jurassic boundary: support for eustatic control of global sequence stratigraphy

    SciTech Connect

    Loughman, D.L.

    1988-02-01

    Recognition of global seismostratigraphic sequences and their eustatic interpretation has been a key geological concept of the past decade. Published criticism recently has led Exxon staff to constrain their sequence boundaries through the onshore geological record, thus placing the data base partially in the public domain. This act is a major step, since field testing of the eustatic model has been surprisingly limited, despite the latter's widespread use in interpretating basin histories. The type of field calibration required is exemplified by a comprehensive global analysis of the marine stratigraphic record from the basal Sevatian substrate (Norian) to the Semicostatum zone (Sinemurian). This 20 Ma interval was originally selected because of discrepancies between Exxon's and previous eustatic curves, and for its sound biostratigraphic control. Four key areas were studied at outcrop, in varied paleogeographic and paleotectonic settings (Peru, Nevada, northwestern Europe and pacific Canada). Fieldwork was supported by an extensive literature survey, including key areas of the eastern USSR. Interpretation involved depth assessment for each facies and the construction of bathymetric curves, which contrasts with the Exxon objective of recognizing depositional surfaces consistent with the seismostratigraphic model. A significant similarity between the 23 bathymetric curves created indicates eustatic control. The bathymetric data also constrain rates of global sea level change. Important global shallowing phases during Crickmayi zone and Angulata zone times were recognized in the study, consistent with the Exxon model. The Exxon perception of the Hettangian as a sea level lowstand is not supported and requires further discussion.

  19. Twentieth century sea level: An enigma

    PubMed Central

    Munk, Walter

    2002-01-01

    Changes in sea level (relative to the moving crust) are associated with changes in ocean volume (mostly thermal expansion) and in ocean mass (melting and continental storage): ζ(t) = ζsteric(t) + ζeustatic(t). Recent compilations of global ocean temperatures by Levitus and coworkers are in accord with coupled ocean/atmosphere modeling of greenhouse warming; they yield an increase in 20th century ocean heat content by 2 × 1023 J (compared to 0.1 × 1023 J of atmospheric storage), which corresponds to ζgreenhouse(2000) = 3 cm. The greenhouse-related rate is accelerating, with a present value ζ̇greenhouse(2000) ≈ 6 cm/century. Tide records going back to the 19th century show no measurable acceleration throughout the late 19th and first half of the 20th century; we take ζ̇historic = 18 cm/century. The Intergovernmental Panel on Climate Change attributes about 6 cm/century to melting and other eustatic processes, leaving a residual of 12 cm of 20th century rise to be accounted for. The Levitus compilation has virtually foreclosed the attribution of the residual rise to ocean warming (notwithstanding our ignorance of the abyssal and Southern Oceans): the historic rise started too early, has too linear a trend, and is too large. Melting of polar ice sheets at the upper limit of the Intergovernmental Panel on Climate Change estimates could close the gap, but severe limits are imposed by the observed perturbations in Earth rotation. Among possible resolutions of the enigma are: a substantial reduction from traditional estimates (including ours) of 1.5–2 mm/y global sea level rise; a substantial increase in the estimates of 20th century ocean heat storage; and a substantial change in the interpretation of the astronomic record. PMID:12011419

  20. Twentieth century sea level: an enigma.

    PubMed

    Munk, Walter

    2002-05-14

    Changes in sea level (relative to the moving crust) are associated with changes in ocean volume (mostly thermal expansion) and in ocean mass (melting and continental storage): zeta(t) = zeta(steric)(t) + zeta(eustatic)(t). Recent compilations of global ocean temperatures by Levitus and coworkers are in accord with coupled ocean/atmosphere modeling of greenhouse warming; they yield an increase in 20th century ocean heat content by 2 x 10(23) J (compared to 0.1 x 10(23) J of atmospheric storage), which corresponds to zeta(greenhouse)(2000) = 3 cm. The greenhouse-related rate is accelerating, with a present value zeta(greenhouse)(2000) approximately 6 cm/century. Tide records going back to the 19th century show no measurable acceleration throughout the late 19th and first half of the 20th century; we take zeta(historic) = 18 cm/century. The Intergovernmental Panel on Climate Change attributes about 6 cm/century to melting and other eustatic processes, leaving a residual of 12 cm of 20th century rise to be accounted for. The Levitus compilation has virtually foreclosed the attribution of the residual rise to ocean warming (notwithstanding our ignorance of the abyssal and Southern Oceans): the historic rise started too early, has too linear a trend, and is too large. Melting of polar ice sheets at the upper limit of the Intergovernmental Panel on Climate Change estimates could close the gap, but severe limits are imposed by the observed perturbations in Earth rotation. Among possible resolutions of the enigma are: a substantial reduction from traditional estimates (including ours) of 1.5-2 mm/y global sea level rise; a substantial increase in the estimates of 20th century ocean heat storage; and a substantial change in the interpretation of the astronomic record.

  1. Sea level controls on carbonate facies associated with Mesozoic and Cenozoic hydrocarbon fields

    SciTech Connect

    Kendall, C.G.S.C. ); Alsharhan, A. ); Stoudt, D. ); Bowen, B.

    1990-05-01

    Abundant subsurface data for the Mesozoic and Cenozoic sections of the Gulf Coast of the US and the Middle East makes it possible to track the relationship of shelf carbonates and evaporites with minor clastics to eustatic sea level. Since sedimentary stratigraphy for both regions was driven by gentle tectonic subsidence punctuated by eustatic sea level variations, the major hydrocarbon fields from these areas can be classified in terms of sea level behavior at the time of the deposition of the reservoir section. With the exception of chalks, most of these carbonate hydrocarbon fields can be related to highstand system tracts and include (1) keep-up plays with sheet-like geometry formed when carbonate accumulation matched sea level rise, aggrading to form shoaling-upward cycles during sea level highstands; (2) give-up plays in which carbonate accumulation was unable to match sea level rise and catch-up plays in which carbonate accumulation initially was unable to keep pace with the sea level rise, but then aggraded to sea level forming lense-like geometry on drowned shelves downslope from carbonate margins during and following rapid sea level rises; and (3) plays with the prograded discontinuous clinoform geometry of the platform margin, formed during stillstands by carbonate accumulation that not only kept-up with the sea level rise but accumulated in a seaward direction. Source rocks for these carbonate reservoirs often formed during rapid sea level rises whereas the reservoir seals are usually shales, dense limestones and/or evaporites.

  2. Late Holocene sea level changes along the coast of Southwestern Turkey

    NASA Astrophysics Data System (ADS)

    Kızıldaǧ, Nilhan; Özdaş, Harun; Özel, Erdeniz

    2014-05-01

    A multi-disciplinary survey has been performed along the coast of southwestern Turkey in order to determine relative sea level changes during the Late Holocene. Especially, the submergence of harbour structures of the ancient coastal settlements provides noticeable evidence for eustatic sea level rise and/or tectonic subsidence. In addition, the traces of bioerosion produced by some organisms along the limestone coasts formed at mean sea level position represent a remarkable data of paleoshorelines. These traces can be found below the current sea level nowadays due to relative sea level rise. Both archaeological and biological data provide an important source on the amount and period of relative sea level rise along the coasts of southwestern Turkey-southeastern Aegean Sea. This region is under the influence of active tectonism as a result of the collision of the Arab-African and Eurasian plates. Thus, a large number of earthquakes have occurred in this zone which must have been an impact on submergence of ancient harbour structures and geomorphological formations. This area is located very important zone in terms of being tectonically active, having a large number of ancient coastal settlements, and consisting of limestone lithology. A number of submerged archaeological structures and bioerosion formations have been investigated by measuring the depths of remains with respect to the present sea level. By comparing the eustatic sea level change, current elevations and construction time of archaeological remains, which dated taking into account construction techniques and ceramic findings, we determine the amount of relative sea level change. In addition, numerous active faults have been detected by performing seismic survey. The results indicate that the vertical tectonic movement has much more effect on submergence of archaeological and geomorphological features than eustatic sea level rise. Uncovering the role of the tectonic movement and sea level changes on the

  3. Assessing impacts of potential accelerating sea-level rise on coastal energy facilities, USA

    SciTech Connect

    Harrison, W.; Santini, D.J. ); Aubrey, D.G. . Coastal Research Center)

    1989-01-01

    The combination of worldwide (eustatic) sea-level rise (SLR) and local SLR due to consolidation of sediments or downward crustal movement is termed relative SLR'' (RSLR). Recent studies indicate that the eustatic component of RSLR may accelerate in the years ahead due to climate warming. This eustatic SLR will be augmented by ongoing consolidation of sediments and crustal subsidence along numerous stretches of the Atlantic and Gulf coasts of the United States, with attendant threats to existing and planned energy facilities. This paper provides a strategy for estimating the costs that could be incurred under various SLR scenarios for such facilities as electric generating stations, petroleum refinery/storage facilities, chemical plants, steel mills, and oil and liquefied natural gas port facilities. 15 refs., 3 figs.

  4. Evidence for sediment fan deposition on outer Texas shelf during Miocene eustatic sea level highstands

    SciTech Connect

    Riese, W.C.; Olsen, R.S.; Rosen, R.N.

    1988-02-01

    Four types of data were reviewed in an attempt to clearly define the environments of deposition for reservoir sands in the Matagorda 668 field: well log curve shapes, seismic amplitude responses, micropaleontology, and thin section sedimentary petrology. All four lines of evidence support the interpretation that these lower Miocene sands were deposited as fan complexes.

  5. On Early Holocene Ice-Sheet/Sea-Level Interactions

    NASA Astrophysics Data System (ADS)

    Tornqvist, T. E.; Hijma, M.

    2011-12-01

    Early Holocene sea-level change constitutes an imperfect, yet potentially valuable analog for future sea-level rise, given the rapidly disintegrating land-based ice under climate conditions of high-latitude Northern Hemisphere warming. The associated rates of eustatic sea-level rise (cm/yr order of magnitude) fall within the range of predictions for the latter part of the next century. However, the early Holocene eustatic sea-level history is otherwise rather poorly understood. Recent impetus has been provided by new records of both relative sea-level (RSL) change and ice-sheet retreat that are sometimes difficult to reconcile in terms of timing and magnitude of change. We first summarize the state-of-the-art on early Holocene sea-level change and then identify key near-term research needs. Recent studies have identified a number of decimeter to meter-scale sea-level jumps, several of which have been linked to catastrophic drainage of proglacial Lake Agassiz and the 8.2 ka cooling event. It is increasingly clear that this occurred by means of two successive jumps, separated by up to a few centuries, and only the latter (and final) one coinciding with the 8.2 ka climate event proper. We show that a considerable research effort, including near-field, intermediate-field, and far-field localities across the globe is needed to fully understand the timing and magnitude of these sea-level jumps. Accomplishing this goal would in addition offer a unique opportunity for rigorous testing of gravitational theory and associated sea-level fingerprinting that plays a critical role in predicting future sea-level change. A more enigmatic sea-level jump that has been identified around 7.6 ka has received renewed interest both by means of new RSL data from Fennoscandia and reconstructions of Laurentide Ice Sheet retreat. However, the proposed ~5 m abrupt rise in eustatic sea level cannot be detected in relatively nearby, detailed RSL records from NW Europe, thus presenting a

  6. Sea level change: a philosophical approach

    NASA Astrophysics Data System (ADS)

    Leinfelder, R.; Seyfried, H.

    1993-07-01

    The present Cenozoic era is an ‘icehouse’ episode characterized by a low sea level. Since the beginning of the industrial revolution, the human race has been emitting greenhouse gases, increasing the global atmospheric temperature, and causing a rise in sea level. If emissions continue to increase at the present rate, average global temperatures may rise by 1.5°C by the year 2050, accompanied by a rise of about 30 cm in sea level. However, the prediction of future climatic conditions and sea level is hampered by the difficulty in modelling the interactions between the lithosphere, kryosphere, biosphere and atmosphere; in addition, the buffering capacity of our planet is still poorly understood. As scientists cannot offer unambiguous answers to simple questions, sorcerer's apprentices fill in the gaps, presenting plans to save planet without inconveniencing us. The geological record can help us to learn about the regulation mechanisms of our planet, many of which are connected with or expressed as sea level changes. Global changes in sea level are either tectono-eustatic or glacioeustatic. Plate tectonic processes strongly control sea levels and climate in the long term. There is a strong feed-back mechanism between sea level and climate; both can influence and determine each other. Although high sea levels are a powerful climatic buffer, falling sea levels accelerate climatic accentuation, the growth of the polar ice caps and will hence amplify the drop in sea level. Important sources of fossil greenhouse gases are botanic CO2 production, CO2 released by volcanic activity, and water vapour. The latter is particularly important when the surface area of the sea increases during a rise in sea level (‘maritime greenhouse effect’). A ‘volcanogenic greenhouse effect’ (release of volcanogenic CO2) is possibly not equally important, as intense volcanic activity may take place both during icehouse episodes as well as during greenhouse episodes. The hydrosphere

  7. Global sea level rise

    SciTech Connect

    Douglas, B.C. )

    1991-04-15

    Published values for the long-term, global mean sea level rise determined from tide gauge records exhibit considerable scatter, from about 1 mm to 3 mm/yr. This disparity is not attributable to instrument error; long-term trends computed at adjacent sites often agree to within a few tenths of a millimeter per year. Instead, the differing estimates of global sea level rise appear to be in large part due to authors' using data from gauges located at convergent tectonic plate boundaries, where changes of land elevation give fictitious sea level trends. In addition, virtually all gauges undergo subsidence or uplift due to postglacial rebound (PGR) from the last deglaciation at a rate comparable to or greater than the secular rise of sea level. Modeling PGR by the ICE-3G model of Tushingham and Peltier (1991) and avoiding tide gauge records in areas of converging tectonic plates produces a highly consistent set of long sea level records. The value for mean sea level rise obtained from a global set of 21 such stations in nine oceanic regions with an average record length of 76 years during the period 1880-1980 is 1.8 mm/yr {plus minus} 0.1. This result provides confidence that carefully selected long tide gauge records measure the same underlying trend of sea level and that many old tide gauge records are of very high quality.

  8. History of coral reefs and sea level

    SciTech Connect

    Fairbridge, R.W.

    1985-01-01

    Charles Darwin proposed crustal subsidence for atoll growth, on the Beagle, between England and Brazil, before even seeing a coral reef, on the basis of charts and discussions with Captain Fitzroy. Relative change of sea level due to crustal movements was then well-accepted from evidence of raised strandlines in Scandinavia and Scotland and sunken forests in England. Darwin added global change of sea level (tectonoeustasy) caused by remote tectonic activity, as explained by Robert Chambers (1848, p. 319). The glacioeustasy concept was mooted soon afterwards, though the term itself came later. When Suess in 1888 proposed eustatic change, he had in mind Archimedian displacement of water by sediment or lava accumulation on the sea floor. Integrated ideas of reef development also came in the 20th century. The powerful arguments against Darwin were led by Murray with his solution hypothesis, which can not be judged as good observation but from a narrow viewpoint. The Royal Society reef borings at Funafuti were heroic but at the same time misread. Subsequently came isotopic geochemistry, absolute dating, the Milankovitch insolation theory, and plate tectonics. And much more field work. The result is an integrated reef growth theory.

  9. Sea level variation

    NASA Technical Reports Server (NTRS)

    Douglas, Bruce C.

    1992-01-01

    Published values for the long-term, global mean sea level rise determined from tide gauge records range from about one to three mm per year. The scatter of the estimates appears to arise largely from the use of data from gauges located at convergent tectonic plate boundaries where changes of land elevation give fictitious sea level trends, and the effects of large interdecadal and longer sea level variations on short (less than 50+ years) or sappy records. In addition, virtually all gauges undergo subsidence or uplift due to isostatic rebound from the last deglaciation at a rate comparable to or greater than the secular rise of sea level. Modeling rebound by the ICE-3G model of Tushingham and Peltier (1990) and avoiding tide gauge records in areas of converging tectonic plates produces a highly consistent set of long sea level records. A global set of 21 such stations in nine oceanic regions with an average record length of 76 years during the period 1880-1980 yields the global sea level rise value 1.8 mm/year +/- 0.1. Greenhouse warming scenarios commonly forecast an additional acceleration of global sea level in the next 5 or 6+ decades in the range 0.1-0.2 mm/yr2. Because of the large power at low frequencies in the sea level spectrum, very long tide gauge records (75 years minimum) have been examined for past apparent sea level acceleration. For the 80-year period 1905-1985, 23 essentially complete tide gauge records in 10 geographic groups are available for analysis. These yielded the apparent global acceleration -0.011 (+/- 0.012) mm/yr2. A larger, less uniform set of 37 records in the same 10 groups with 92 years average length covering the 141 years from 1850-1991 gave 0.001 (+/- 0.008) mm/yr2. Thus there is no evidence for an apparent acceleration in the past 100+ years that is significant either statistically, or in comparison to values associated with global warming. Unfortunately, the large interdecadal fluctuations of sea level severely affect

  10. Sea level variation

    NASA Technical Reports Server (NTRS)

    Douglas, Bruce C.

    1992-01-01

    Published values for the long-term, global mean sea level rise determined from tide gauge records range from about one to three mm per year. The scatter of the estimates appears to arise largely from the use of data from gauges located at convergent tectonic plate boundaries where changes of land elevation give fictitious sea level trends, and the effects of large interdecadal and longer sea level variations on short (less than 50+ years) or sappy records. In addition, virtually all gauges undergo subsidence or uplift due to isostatic rebound from the last deglaciation at a rate comparable to or greater than the secular rise of sea level. Modeling rebound by the ICE-3G model of Tushingham and Peltier (1990) and avoiding tide gauge records in areas of converging tectonic plates produces a highly consistent set of long sea level records. A global set of 21 such stations in nine oceanic regions with an average record length of 76 years during the period 1880-1980 yields the global sea level rise value 1.8 mm/year +/- 0.1. Greenhouse warming scenarios commonly forecast an additional acceleration of global sea level in the next 5 or 6+ decades in the range 0.1-0.2 mm/yr2. Because of the large power at low frequencies in the sea level spectrum, very long tide gauge records (75 years minimum) have been examined for past apparent sea level acceleration. For the 80-year period 1905-1985, 23 essentially complete tide gauge records in 10 geographic groups are available for analysis. These yielded the apparent global acceleration -0.011 (+/- 0.012) mm/yr2. A larger, less uniform set of 37 records in the same 10 groups with 92 years average length covering the 141 years from 1850-1991 gave 0.001 (+/- 0.008) mm/yr2. Thus there is no evidence for an apparent acceleration in the past 100+ years that is significant either statistically, or in comparison to values associated with global warming. Unfortunately, the large interdecadal fluctuations of sea level severely affect

  11. Sea level change

    SciTech Connect

    Meier, M.F.

    1996-12-31

    The IPCC (Intergovernmental Panel on Climate Change) 1995 Scientific Assessment, Chapter 7. Sea Level Change, presents a modest revision of the similar chapter in the 1990 Assessment. Principal conclusions on observed sea-level change and the principal terms in the sea-level equation (ocean thermal expansion, glaciers, ice sheets, and land hydrology), including our knowledge of the present-day (defined as the 20th Century) components of sea-level rise, and projections of these for the future, are presented here. Some of the interesting glaciological problems which are involved in these studies are discussed in more detail. The emphasis here is on trends over decades to a century, not on shorter variations nor on those of the geologic past. Unfortunately, some of the IPCC projections had not been agreed at the time of writing of this paper, and these projections will not be given here. 15 refs., 2 figs.

  12. Mid-Pliocene (~3 Ma) relative sea level markers around the world: searching for eustasy.

    NASA Astrophysics Data System (ADS)

    Rovere, Alessio; Raymo, Maureen; Hearty, Paul; MItrovica, Jerry; Austermann, Jacqueline; O'Leary, Michael; Sandstrom, Michael

    2014-05-01

    PLIOMAX (PLIOcene MAXimum sea level) is a five-year research project that aims to increase the accuracy of global sea level estimates for the mid-Pliocene warm period. To achieve its goals, PLIOMAX has organized several field expeditions to identify, measure and date relative sea level markers of mid-Pliocene age from around the globe, and built a network of collaborators expert in different geographic areas and disciplines. In this work we present field data obtained from South Africa, Australia, Italy, Argentina and the US East Coast. In these areas we sampled, measured and dated geological facies related to mid-Pliocene sea level. Most areas yield information on 3 Ma sea levels with an accuracy of few decimeters. In presenting our dataset, we will show how we address the following questions, including: how can we obtain accurate measurements in the field? What is the accuracy of the markers we measure in indicating past relative sea levels? To which point can we trust older literature data? We then show how the elevations of relative sea level markers obtained in the field must be corrected to obtain an estimate of eustatic sea level. These corrections use models of glacial isostatic adjustment and dynamic topography. We discuss uncertainties linked to these models as well as the main issues that are still separating us from obtaining a robust estimate of maximum eustatic sea level during the mid-Pliocene warm period.

  13. Contemporary sea level rise.

    PubMed

    Cazenave, Anny; Llovel, William

    2010-01-01

    Measuring sea level change and understanding its causes has considerably improved in the recent years, essentially because new in situ and remote sensing observations have become available. Here we report on most recent results on contemporary sea level rise. We first present sea level observations from tide gauges over the twentieth century and from satellite altimetry since the early 1990s. We next discuss the most recent progress made in quantifying the processes causing sea level change on timescales ranging from years to decades, i.e., thermal expansion of the oceans, land ice mass loss, and land water-storage change. We show that for the 1993-2007 time span, the sum of climate-related contributions (2.85 +/- 0.35 mm year(-1)) is only slightly less than altimetry-based sea level rise (3.3 +/- 0.4 mm year(-1)): approximately 30% of the observed rate of rise is due to ocean thermal expansion and approximately 55% results from land ice melt. Recent acceleration in glacier melting and ice mass loss from the ice sheets increases the latter contribution up to 80% for the past five years. We also review the main causes of regional variability in sea level trends: The dominant contribution results from nonuniform changes in ocean thermal expansion.

  14. Projecting future sea level

    USGS Publications Warehouse

    Cayan, Daniel R.; Bromirski, Peter; Hayhoe, Katharine; Tyree, Mary; Dettinger, Mike; Flick, Reinhard

    2006-01-01

    California’s coastal observations and global model projections indicate that California’s open coast and estuaries will experience increasing sea levels over the next century. Sea level rise has affected much of the coast of California, including the Southern California coast, the Central California open coast, and the San Francisco Bay and upper estuary. These trends, quantified from a small set of California tide gages, have ranged from 10–20 centimeters (cm) (3.9–7.9 inches) per century, quite similar to that estimated for global mean sea level. So far, there is little evidence that the rate of rise has accelerated, and the rate of rise at California tide gages has actually flattened since 1980, but projections suggest substantial sea level rise may occur over the next century. Climate change simulations project a substantial rate of global sea level rise over the next century due to thermal expansion as the oceans warm and runoff from melting land-based snow and ice accelerates. Sea level rise projected from the models increases with the amount of warming. Relative to sea levels in 2000, by the 2070–2099 period, sea level rise projections range from 11–54 cm (4.3–21 in) for simulations following the lower (B1) greenhouse gas (GHG) emissions scenario, from 14–61 cm (5.5–24 in) for the middle-upper (A2) emission scenario, and from 17–72 cm (6.7–28 in) for the highest (A1fi) scenario. In addition to relatively steady secular trends, sea levels along the California coast undergo shorter period variability above or below predicted tide levels and changes associated with long-term trends. These variations are caused by weather events and by seasonal to decadal climate fluctuations over the Pacific Ocean that in turn affect the Pacific coast. Highest coastal sea levels have occurred when winter storms and Pacific climate disturbances, such as El Niño, have coincided with high astronomical tides. This study considers a range of projected future

  15. Paleoshoreline record of relative Holocene sea levels on Pacific islands

    NASA Astrophysics Data System (ADS)

    Dickinson, William R.

    2001-11-01

    Understanding the history of relative Holocene sea levels on Pacific islands is important for constraining fundamental geodynamic theories, interpreting the environments of early human occupation sites, and forecasting future environmental conditions on the islands. An observational paleoshoreline record is provided by emergent paleoshoreline indicators formed at higher relative sea levels, hence standing at higher elevations than modern counterparts. Emergent paleoshoreline notches in limestone seacliffs record paleo-high-tide levels and emergent paleoreef flats record paleo-low-tide levels, whereas emergent paleobeachrock locally records paleo-intertidal levels. Both paleonotches and paleoreefs occur along the coasts of high-standing islands exposing volcanic bedrock and uplifted reef complexes, but low-lying coralline atolls lack sufficient relief to preserve paleonotches. Controls on relative Holocene sea level include global eustatic and regional hydro-isostatic changes in ambient sea level relative to island landmasses, and shifts in the elevations of islands relative to sea level caused by thermal subsidence of the oceanic lithosphere or thermally rejuvenated loci of hotspot volcanism, by flexure of the lithosphere under the load of growing volcanic edifices (Hawaii, Samoa, Society Islands), by arching of the lithosphere over trench forebulges (Loyalty Islands, Niue, Bellona-Rennell), and by tectonism within forearc belts between active volcanic chains and trenches (Mariana Islands, Tonga, Vanuatu). The dominant pattern of relative sea-level change, where not overprinted by local tectonism or lithospheric flexure, was a uniform early Holocene rise in eustatic sea level followed by a regionally variable late Holocene hydro-isostatic drawdown in sea level. The resultant was a mid-Holocene highstand in relative sea level that affected the development of shoreline morphology throughout the tropical Pacific Ocean. The earliest human migrations into intra

  16. Synthetic stratigraphy of epicontinental seas: a carbonate sedimentation model and its applications in sea level studies

    SciTech Connect

    Cisne, J.L.; Gildner, R.F.

    1984-04-01

    Carbonates from the central parts of epicontinental seas are ideal strata for detailed study of eustatic sea level change. On the basis of sedimentation model in which carbonate accumulation rate is directly proportional to water depth, we developed synthetic stratigraphies for sea level histories expected for post-glacial transgression and for constant and sinusoidally fluctuating ocean ridge volume increase. These histories give distinctly different trends for water depth as a function of stratigraphic position in the sections' bathymetric curves. In general, water depth is proportional to the rate of sea level rise. Depth-dependent sedimentation leads to a time lag between sea level fluctuation and corresponding depth fluctuation which, as examples show, can approach 10/sup 6/ years for depth fluctuations of even a few meters--a fundamental consideration for reconstructing sea level curves, time-correlating sections by bathymetric curves, and relating water depth on continents to ocean ridge volume. Bathymetric curves based on gradient analysis of fossil assemblages (coenocorrelation curves) for American Middle Ordovician sections approximate patterns expected for sinusoidally increasing sea level. The model's predictions are tested in an ''artificial experiment'' that takes advantage of differential subsidence between the craton's middle and its edge to make a difference in the bathymetric histories of sections that otherwise record the same sea level history. The depth dependence in sedimentation was that above wave base net accumulation per year was very roughly 3 x 10/sup -6/ of the water depth.

  17. Early humans and rapidly changing holocene sea levels in the Queen Charlotte Islands - Hecate Strait, British Columbia, Canada

    SciTech Connect

    Josenhans, H.; Fedje, D.; Pienitz, R.; Southon, J.

    1997-07-04

    Marine cores from the continental shelf edge of British Columbia (Canada) demonstrate that sea level at the shelf edge was 153 meters below present 14,000 calendar years ago and more than 30 meters lower than the maximum eustatic low of -120 meters. Dated artifacts, including stone tools, indicate that humans occupied this region by at least 10,200 calendar years before present (B.P.). Local sea level rose rapidly (5 centimeters per year) during the period of early human occupation as a result of eustatic sea-level rise and glacio-isostatic forebulge movement. This shelf edge site was first elevated and then subsided. The exposed shelf edge was available for human occupation and may have served as a migration route during times of lowered sea levels between 13,500 and 9500 {sup 14}C years B.P. 34 refs., 6 figs., 1 tab.

  18. Caribbean Sea Level Network

    NASA Astrophysics Data System (ADS)

    von Hillebrandt-Andrade, C.; Crespo Jones, H.

    2012-12-01

    Over the past 500 years almost 100 tsunamis have been observed in the Caribbean and Western Atlantic, with at least 3510 people having lost their lives to this hazard since 1842. Furthermore, with the dramatic increase in population and infrastructure along the Caribbean coasts, today, millions of coastal residents, workers and visitors are vulnerable to tsunamis. The UNESCO IOC Intergovernmental Coordination Group for Tsunamis and other Coastal Hazards for the Caribbean and Adjacent Regions (CARIBE EWS) was established in 2005 to coordinate and advance the regional tsunami warning system. The CARIBE EWS focuses on four areas/working groups: (1) Monitoring and Warning, (2) Hazard and Risk Assessment, (3) Communication and (4) Education, Preparedness and Readiness. The sea level monitoring component is under Working Group 1. Although in the current system, it's the seismic data and information that generate the initial tsunami bulletins, it is the data from deep ocean buoys (DARTS) and the coastal sea level gauges that are critical for the actual detection and forecasting of tsunamis impact. Despite multiple efforts and investments in the installation of sea level stations in the region, in 2004 there were only a handful of sea level stations operational in the region (Puerto Rico, US Virgin Islands, Bermuda, Bahamas). Over the past 5 years there has been a steady increase in the number of stations operating in the Caribbean region. As of mid 2012 there were 7 DARTS and 37 coastal gauges with additional ones being installed or funded. In order to reach the goal of 100 operational coastal sea level stations in the Caribbean, the CARIBE EWS recognizes also the importance of maintaining the current stations. For this, a trained workforce in the region for the installation, operation and data analysis and quality control is considered to be critical. Since 2008, three training courses have been offered to the sea level station operators and data analysts. Other

  19. 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.

  20. Antarctic glacio-eustatic contributions to late Miocene Mediterranean desiccation and reflooding

    PubMed Central

    Ohneiser, Christian; Florindo, Fabio; Stocchi, Paolo; Roberts, Andrew P.; DeConto, Robert M.; Pollard, David

    2015-01-01

    The Messinian Salinity Crisis (MSC) was a marked late Neogene oceanographic event during which the Mediterranean Sea evaporated. Its causes remain unresolved, with tectonic restrictions to the Atlantic Ocean or glacio-eustatic restriction of flow during sea-level lowstands, or a mixture of the two mechanisms, being proposed. Here we present the first direct geological evidence of Antarctic ice-sheet (AIS) expansion at the MSC onset and use a δ18O record to model relative sea-level changes. Antarctic sedimentary successions indicate AIS expansion at 6 Ma coincident with major MSC desiccation; relative sea-level modelling indicates a prolonged ∼50 m lowstand at the Strait of Gibraltar, which resulted from AIS expansion and local evaporation of sea water in concert with evaporite precipitation that caused lithospheric deformation. Our results reconcile MSC events and demonstrate that desiccation and refilling were timed by the interplay between glacio-eustatic sea-level variations, glacial isostatic adjustment and mantle deformation in response to changing water and evaporite loads. PMID:26556503

  1. Antarctic glacio-eustatic contributions to late Miocene Mediterranean desiccation and reflooding.

    PubMed

    Ohneiser, Christian; Florindo, Fabio; Stocchi, Paolo; Roberts, Andrew P; DeConto, Robert M; Pollard, David

    2015-11-10

    The Messinian Salinity Crisis (MSC) was a marked late Neogene oceanographic event during which the Mediterranean Sea evaporated. Its causes remain unresolved, with tectonic restrictions to the Atlantic Ocean or glacio-eustatic restriction of flow during sea-level lowstands, or a mixture of the two mechanisms, being proposed. Here we present the first direct geological evidence of Antarctic ice-sheet (AIS) expansion at the MSC onset and use a δ(18)O record to model relative sea-level changes. Antarctic sedimentary successions indicate AIS expansion at 6 Ma coincident with major MSC desiccation; relative sea-level modelling indicates a prolonged ∼50 m lowstand at the Strait of Gibraltar, which resulted from AIS expansion and local evaporation of sea water in concert with evaporite precipitation that caused lithospheric deformation. Our results reconcile MSC events and demonstrate that desiccation and refilling were timed by the interplay between glacio-eustatic sea-level variations, glacial isostatic adjustment and mantle deformation in response to changing water and evaporite loads.

  2. Understanding Sea Level Changes

    NASA Technical Reports Server (NTRS)

    Chao, Benjamin F.

    2004-01-01

    Today more than 100 million people worldwide live on coastlines within one meter of mean sea level; any short-term or long-term sea level change relative to vertical ground motion is of great societal and economic concern. As palm-environment and historical data have clearly indicated the existence and prevalence of such changes in the past, new scientific information regarding to the nature and causes and a prediction capability are of utmost importance for the future. The 10-20 cm global sea-level rise recorded over the last century has been broadly attributed to two effects: (1) the steric effect (thermal expansion and salinity-density compensation of sea water) following global climate; (2) mass-budget changes due to a number of competing geophysical and hydrological processes in the Earth-atmosphere-hydrosphere-cryosphere system, including water exchange from polar ice sheets and mountain glaciers to the ocean, atmospheric water vapor and land hydrological variations, and anthropogenic effects such as water impoundment in artificial reservoirs and extraction of groundwater, all superimposed on the vertical motions of solid Earth due to tectonics, rebound of the mantle from past and present deglaciation, and other local ground motions. As remote-sensing tools, a number of space geodetic measurements of sea surface topography (e.g., TOPEX/Poseidon, Jason), ice mass (e.g., ICESat), time-variable gravity (e.g. GRACE), and ground motions (SLR, VLBI, GPS, InSAR, Laser altimetry, etc.) become directly relevant. Understanding sea level changes "anywhere, anytime" in a well-defined terrestrial reference frame in terms of climate change and interactions among ice masses, oceans, and the solid Earth, and being able to predict them, emerge as one of the scientific challenges in the Solid Earth Science Working Group (SESWG, 2003) conclusions.

  3. Understanding Sea Level Changes

    NASA Technical Reports Server (NTRS)

    Chao, Benjamin F.

    2004-01-01

    Today more than 100 million people worldwide live on coastlines within one meter of mean sea level; any short-term or long-term sea level change relative to vertical ground motion is of great societal and economic concern. As palm-environment and historical data have clearly indicated the existence and prevalence of such changes in the past, new scientific information regarding to the nature and causes and a prediction capability are of utmost importance for the future. The 10-20 cm global sea-level rise recorded over the last century has been broadly attributed to two effects: (1) the steric effect (thermal expansion and salinity-density compensation of sea water) following global climate; (2) mass-budget changes due to a number of competing geophysical and hydrological processes in the Earth-atmosphere-hydrosphere-cryosphere system, including water exchange from polar ice sheets and mountain glaciers to the ocean, atmospheric water vapor and land hydrological variations, and anthropogenic effects such as water impoundment in artificial reservoirs and extraction of groundwater, all superimposed on the vertical motions of solid Earth due to tectonics, rebound of the mantle from past and present deglaciation, and other local ground motions. As remote-sensing tools, a number of space geodetic measurements of sea surface topography (e.g., TOPEX/Poseidon, Jason), ice mass (e.g., ICESat), time-variable gravity (e.g. GRACE), and ground motions (SLR, VLBI, GPS, InSAR, Laser altimetry, etc.) become directly relevant. Understanding sea level changes "anywhere, anytime" in a well-defined terrestrial reference frame in terms of climate change and interactions among ice masses, oceans, and the solid Earth, and being able to predict them, emerge as one of the scientific challenges in the Solid Earth Science Working Group (SESWG, 2003) conclusions.

  4. Sea Level Variations During Snowball Earth Formation: A Preliminary Analysis

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Peltier, W. R.

    2012-12-01

    The sea level changes that would have accompanied the "Snowball Earth" events of the Late Neoproterozoic (1000 Ma - 540 Ma) have remained enigmatic. Emplacement of the voluminous ice sheets on the continents during these events should have drawn down eustatic sea level by ~1000 m but geological evidence of this having actually occurred is scant. The only reliable estimate is apparently that based upon observations from the Otavi Group in Northern Namibia (Hoffman et al. (2007), Earth Planet Sc Lett, 258(1-2), 114-131, doi:10.1016/j.epsl.2007.03.032) which indicates a sea level change of approximately 500 m to have occurred. In this work, we provide a preliminary theoretical estimate of the extent to which the ocean surface could have fallen with respect to the continents during such snowball Earth events. Our analyses are performed by solving the Sea Level Equation for a spherically symmetric Maxwell Earth subject to extensive continental glaciation for a realistic land-sea distribution. We find, as expected, that the fall of relative sea level must have been highly non-uniform, with the collapse of the geoid least near the coastal regions and greatest in the ocean basin interiors. For a 720 Ma (Sturtian) continental configuration, the ice sheet volume in a snowball state is ~824 m sea level equivalent, but ocean surface lowering (relative to the original surface) can be as little as ~300 m near the coast of a continental fragment that was host of a major ice dome. Although the mean water depth (relative sea level) is reduced by ~824 m, because the mean elevation of the ocean floor is increased by ~193 m, the mean ocean surface fall is only ~631 m. The change of continental freeboard (which may be recorded in the sedimentary record) at the edge of the continents is usually larger than the lowering of ocean surface due to the forebulge effect, ranging from 400 - 600 m. For the 570 Ma (Marinoan) continental configuration, ice sheet volumes is ~1180 m in eustatic sea

  5. A `Pole To Pole' Holocene Sea-Level Database

    NASA Astrophysics Data System (ADS)

    Horton, B.; Vacchi, M.; Shaw, T.; Ashe, E.; Engelhart, S. E.; Khan, N.; Kopp, R. E.

    2016-12-01

    Holocene relative sea-level (RSL) records exhibit spatial and temporal variability that arises from the complex pattern of interactions among eustatic (land ice volume and thermal expansion), isostatic (glacio and hydro), tectonic (neotectonic deformation) and local (tidal range change and sediment compaction) components. Each of these components have different response timescales varying relative importance during the Holocene and among regions. 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 constructed from previously published results that were collated in a formalized and consistent methodology to facilitate the development and comparison of regional RSL records. The RSL records are mostly derived from sea-level indicators from intertidal environments. The database also includes information relevant to sediment compaction, and modelling of both modern-day and paleotidal ranges. We assess rates of RSL change by fitting the RSL records with noisy-input Gaussian process models. Holocene RSL records 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 69 m/ka. Intermediate field regions (e.g., U.S. mid-Atlantic coast, St. Croix) display variable rates of RSL rise from the cumulative effect of eustatic and isostatic factors. Fast rates of RSL rise (up to 10 m/ka) are found in the early Holocene in regions near the center of forebulge collapse. Far-field RSL records (South America) exhibit a mid-Holocene highstand, the timing and magnitude of which varies between 8 and 4 ka and <1 and 6 m, respectively. By comparing these records across a pole to pole database that spans a range of `fingerprints' from land-based ice sheets, we

  6. Late Quaternary sea-level changes of the Persian Gulf

    NASA Astrophysics Data System (ADS)

    Lokier, Stephen W.; Bateman, Mark D.; Larkin, Nigel R.; Rye, Philip; Stewart, John R.

    2015-07-01

    Late Quaternary reflooding of the Persian Gulf climaxed with the mid-Holocene highstand previously variously dated between 6 and 3.4 ka. Examination of the stratigraphic and paleoenvironmental context of a mid-Holocene whale beaching allows us to accurately constrain the timing of the transgressive, highstand and regressive phases of the mid- to late Holocene sea-level highstand in the Persian Gulf. Mid-Holocene transgression of the Gulf surpassed today's sea level by 7100-6890 cal yr BP, attaining a highstand of > 1 m above current sea level shortly after 5290-4570 cal yr BP before falling back to current levels by 1440-1170 cal yr BP. The cetacean beached into an intertidal hardground pond during the transgressive phase (5300-4960 cal yr BP) with continued transgression interring the skeleton in shallow-subtidal sediments. Subsequent relative sea-level fall produced a forced regression with consequent progradation of the coastal system. These new ages refine previously reported timings for the mid- to late Holocene sea-level highstand published for other regions. By so doing, they allow us to constrain the timing of this correlatable global eustatic event more accurately.

  7. Quaternary climates and sea levels of the U.S. atlantic coastal plain

    USGS Publications Warehouse

    Cronin, T. M.; Szabo, B. J.; Ager, T.A.; Hazel, J.E.; Owens, J.P.

    1981-01-01

    Uranium-series dating of corals from marine deposits of the U.S. Atlantic Coastal Plain coupled with paleodimatic reconstructions based on ostracode (marine) and pollen (continent) data document at least five relatively warm intervals during the last 500,000 years. On the basis of multiple paleoenvironmental criteria, we determined relative sea level positions during the warm intervals, relative to present mean sea level, were 7 ?? 5 meters at 188,000 years ago, 7.5 ??1.5 meters at 120,000 years ago, 6.5 ?? 3.5 meters at 94,000 years ago, and 7 ?? 3 meters at 72,000 years ago. The composite sea level chronology for the Atlantic Coastal Plain is inconsistent with independent estimates of eustatic sea level positions during interglacial intervals of the last 200,000 years. Hydroisostatic adjustment from glacial-interglacial sea level fluctuations, lithospheric flexure, and isostatic uplift from sediment unloading due to erosion provide possible mechanisms to account for the discrepancies. Alternatively, current eustatic sea level estimates for the middle and late Quaternary may require revision.

  8. Quaternary climates and sea levels of the u.s. Atlantic coastal plain.

    PubMed

    Cronin, T M; Szabo, B J; Ager, T A; Hazel, J E; Owens, J P

    1981-01-16

    Uranium-series dating of corals from marine deposits of the U.S. Atlantic Coastal Plain coupled with paleoclimatic reconstructions based on ostracode (marine) and pollen (continent) data document at least five relatively warm intervals during the last 500,000 years. On the basis of multiple paleoenvironmental criteria, we determined relative sea level positions during the warm intervals, relative to present mean sea level, were 7 +/- 5 meters at 188,000 years ago, 7.5 +/- 1.5 meters at 120,000 years ago, 6.5 +/- 3.5 meters at 94,000 years ago, and 7 +/- 3 meters at 72,000 years ago. The composite sea level chronology for the Atlantic Coastal Plain is inconsistent with independent estimates of eustatic sea level positions during interglacial intervals of the last 200,000 years. Hydroisostatic adjustment from glacial-interglacial sea level fluctuations, lithospheric flexure, and isostatic uplift from sediment unloading due to erosion provide possible mechanisms to account for the discrepancies. Alternatively, current eustatic sea level estimates for the middle and late Quaternary may require revision.

  9. Sea-level rise in New Jersey over the past 5000 years: Implications to anthropogenic changes

    USGS Publications Warehouse

    Miller, Kenneth G.; Sugarman, Peter J.; Browning, James V.; Horton, Benjamin P.; Stanley, Alissa; Kahn, Alicia; Uptegrove, Jane; Aucott, Michael

    2009-01-01

    We present a mid to late Holocene sea-level record derived from drilling the New Jersey coast that shows a relatively constant rise of 1.8??mm/yr from ~ 5000 to 500 calibrated calendar years before present (yrBP). This contrasts with previous New Jersey estimates that showed only 0.5??mm/yr rise since 2000??yrBP. Comparison with other Mid-Atlantic sea-level records (Delaware to southern New England) indicates surprising uniformity considering different proximities to the peripheral bulge of the Laurentide ice sheet, with a relative rise throughout the region of ~ 1.7-1.9??mm/yr since ~ 5000??yrBP. This regional sea-level rise includes both: 1) global sea-level (eustatic) rise; and 2) far-field geoidal subsidence (estimated as ~ 0.8-1.4??mm/yr today) due to removal of the Laurentide ice sheet and water loading. Correcting for geoidal subsidence, the U.S. east coast records suggest a global sea-level (eustatic) rise of ~ 0.4-1.0??mm/yr (with a best estimate of 0.7 ?? 0.3??mm/yr) since 5000??yrBP. Comparison with other records provides a best estimate of pre-anthropogenic global sea-level rise of < 1.0??mm/yr from 5000 until ~ 200??yrBP. Tide gauge data indicate a 20th century rate of eustatic rise of 1.8??mm/yr, whereas both tide gauge and satellite data suggest an increase in the rate of rise to ~ 3.3??mm/yr from 1993-2006 AD. This indicates that the modern rise (~ 3.3??mm/yr) is significantly higher than the pre-anthropogenic rise (0.7 ?? 0.3??mm/yr). ?? 2008 Elsevier B.V. All rights reserved.

  10. Depositional facies and eustatic effects in Upper Cretaceous (Maastrichtian) Ripley Formation, central and eastern Alabama

    SciTech Connect

    Skotnicki, M.C.; King, D.T. Jr. )

    1989-09-01

    In eastern and central Alabama, the Upper Cretaceous Ripley Formation (40-175 m thick) is comprised of five depositional facies. Facies 1 (barrier-island shoreface and tidal-inlet fill) is a medium to coarse, intraclastic quartzose sand that is planar and trough cross-stratified and has abundant Ophiomorpha traces. Facies 2 (back-barrier lagoon or marsh) is a bioturbated, micaceous, carbonaceous silt that contains macerated plant debris and bivalve molds and impressions. Interbedded with facies 2 is facies 3 (storm-washover deposits), a hummocky cross-stratified, micaceous fine sand. Facies 4 (back-barrier tidal flat) is a micaceous silty clay lacking body fossils and plant debris. Facies 5 (lower shoreface) is a glauconitic, clayey and micaceous, fine to medium sand that is highly bioturbated and commonly has abundant marine macrofauna. The Ripley is divided into two genetic packages of facies; the genetic packages are bounded by stratigraphic breaks or discontinuities. The package-bounding breaks are correlated biostratigraphically with discrete third-order eustatic drops on the world sea level curve. The basal Ripley break is correlated with the end of Campanian (about 74 Ma) eustatic drop, and the middle Ripley break (separating the two genetic packages) marks the mid-Maastrichtian (71 Ma) sea level drop. The basal and middle Ripley breaks are low-relief surfaces marked by sharp facies discontinuities (correlatable across 130 km) and terminal coarsening-upward cycles (5 m thick); the estimated eustatic sea level fall in both instances was about 50 m. The break at the top of the Ripley has 70 m of erosional relief and a bone bed up to 80 cm thick. This break represents a late Maastrichtian (about 68 Ma) sea level fall estimated to have been nearly 95 m. Facies of the superjacent Prairie Bluff Chalk and Providence Sand overlie the erosional surface.

  11. A Holocene sea-level database for Southeast Asia

    NASA Astrophysics Data System (ADS)

    Bender, Maren; Mann, Thomas; Stocchi, Paolo; Switzer, Adam; Horton, Benjamin P.; Lukman, Muhammad; Jompa, Jamaluddin; Rovere, Alessio

    2017-04-01

    The study of former relative sea-level (RSL) changes is essential to disentangle changes in sea level due to vertical land motion (e.g. tectonics, Glacial Isostatic Adjustment - GIA) and eustatic (e.g. ice equivalent sea level) causes. To study RSL changes at a regional scale it is essential that databases of sea-level indicators are produced following standardized protocols (Hijma et al., 2015). This has been already done in several regions (e.g. the US Atlantic coast, the Caribbean, or the Mediterranean (Engelhart and Horton, 2012) A database has been compiled for Southeast Asia but was limited in geographical extent and didn't include the influence of local process such as tidal range changes and compaction. Southeast Asia is highly vulnerable to relative sea level changes, as it is characterized by low-lying, densely populated islands and subsiding deltas. We present a database of Holocene sea-level histories in Southeast Asia and part of the Indo-Pacific from published and unpublished data, which has been evaluated and using a standardized protocol. We analyzed 526 sea level index points, defining their locations the height of former sea level and the age with their associated uncertainty. Radiocarbon ages were re-calibrated using Calib 7.0.0 / 7.1 (Stuiver et al., 2017) and the calibration curves Intcal13 or Marine13. In our database, we also indicated possible tectonic vertical land motion, and we present the results of GIA modelling for different areas in SE Asia. We also show regions of South East Asia and parts of the Indo-Pacific where there is an absence of data and where the collection of new RSL data is mostly needed.

  12. Mediterranean Sea level variations during the Messinian salinity crisis

    NASA Astrophysics Data System (ADS)

    Gargani, Julien; Rigollet, Christophe

    2007-05-01

    The Mediterranean Basin has not always been connected to the Atlantic Ocean. During the Messinian salinity crisis (MSC), the Mediterranean Sea became progressively isolated by a complex combination of tectonic and glacio-eustatic processes. When isolated, the Mediterranean water level depends on the hydrological flux and is expected to vary significantly. The amplitude and number of large water level fluctuations in the isolated Mediterranean is still controversial, despite numerous geological investigations. The observation of 3-5 surfaces of erosion in the Nile delta (Eastern Basin) provides new elements for understanding the dynamics of the MSC. Our model demonstrates that numerous water level falls of short duration may explain the preservation of a discontinuous river profile at ~-500 m and ~-1500 m in the Western Basin, as well as the existence of deep surfaces of erosion in the Eastern Basin.

  13. 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

  14. 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.

  15. Sea level in Roman time in the Central Mediterranean and implications for recent change

    NASA Astrophysics Data System (ADS)

    Lambeck, Kurt; Anzidei, Marco; Antonioli, Fabrizio; Benini, Alessandra; Esposito, Alessandra

    2004-08-01

    Instrumental records indicate that ocean volumes during the 20th century have increased so as to raise eustatic sea level by ˜1-2 mm/year and the few available records suggest that this is higher than for the previous century. Geological data indicate that ocean volumes have increased since the main phase of deglaciation about 7000 years ago but whether this continued into the recent past remains unclear. Yet, this is important for establishing whether the recent rise is associated with global warming or is part of a longer duration non-anthropogenic signal. Here, we present results for sea-level change in the central Mediterranean basin for the Roman Period using new archaeological evidence. These data provide a precise measure of local sea level of -1.35±0.07 m at 2000 years ago. Part of this change is the result of ongoing glacio-hydro isostatic adjustment of the crust subsequent to the last deglaciation. When corrected for this, using geologically constrained model predictions, the change in eustatic sea level since the Roman Period is -0.13±0.09 m. A comparison with tide-gauge records from nearby locations and with geologically constrained model predictions of the glacio-isostatic contributions establishes that the onset of modern sea-level rise occurred in recent time at ˜100±53 years before present.

  16. Holocene sea level variations on the basis of integration of independent data sets

    SciTech Connect

    Sahagian, D.; Berkman, P. . Dept. of Geological Sciences and Byrd Polar Research Center)

    1992-01-01

    Variations in sea level through earth history have occurred at a wide variety of time scales. Sea level researchers have attacked the problem of measuring these sea level changes through a variety of approaches, each relevant only to the time scale in question, and usually only relevant to the specific locality from which a specific type of data are derived. There is a plethora of different data types that can and have been used (locally) for the measurement of Holocene sea level variations. The problem of merging different data sets for the purpose of constructing a global eustatic sea level curve for the Holocene has not previously been adequately addressed. The authors direct the efforts to that end. Numerous studies have been published regarding Holocene sea level changes. These have involved exposed fossil reef elevations, elevation of tidal deltas, elevation of depth of intertidal peat deposits, caves, tree rings, ice cores, moraines, eolian dune ridges, marine-cut terrace elevations, marine carbonate species, tide gauges, and lake level variations. Each of these data sets is based on particular set of assumptions, and is valid for a specific set of environments. In order to obtain the most accurate possible sea level curve for the Holocene, these data sets must be merged so that local and other influences can be filtered out of each data set. Since each data set involves very different measurements, each is scaled in order to define the sensitivity of the proxy measurement parameter to sea level, including error bounds. This effectively determines the temporal and spatial resolution of each data set. The level of independence of data sets is also quantified, in order to rule out the possibility of a common non-eustatic factor affecting more than one variety of data. The Holocene sea level curve is considered to be independent of other factors affecting the proxy data, and is taken to represent the relation between global ocean water and basin volumes.

  17. Sea level extremes in the Caribbean Sea

    NASA Astrophysics Data System (ADS)

    Torres, R. Ricardo; Tsimplis, Michael N.

    2014-08-01

    Sea level extremes in the Caribbean Sea are analyzed on the basis of hourly records from 13 tide gauges. The largest sea level extreme observed is 83 cm at Port Spain. The largest nontidal residual in the records is 76 cm, forced by a category 5 hurricane. Storm surges in the Caribbean are primarily caused by tropical storms and stationary cold fronts intruding the basin. However, the seasonal signal and mesoscale eddies also contribute to the creation of extremes. The five stations that have more than 20 years of data show significant trends in the extremes suggesting that flooding events are expected to become more frequent in the future. The observed trends in extremes are caused by mean sea level rise. There is no evidence of secular changes in the storm activity. Sea level return periods have also been estimated. In the south Colombian Basin, where large hurricane-induced surges are rare, stable estimates can be obtained with 30 years of data or more. For the north of the basin, where large hurricane-induced surges are more frequent, at least 40 years of data are required. This suggests that the present data set is not sufficiently long for robust estimates of return periods. ENSO variability correlates with the nontidal extremes, indicating a reduction of the storm activity during positive ENSO events. The period with the highest extremes is around October, when the various sea level contributors' maxima coincide.

  18. Upper Cretaceous sequences and sea-level history, New Jersey Coastal Plain

    USGS Publications Warehouse

    Miller, K.G.; Sugarman, P.J.; Browning, J.V.; Kominz, M.A.; Olsson, R.K.; Feigenson, M.D.; Hernandez, J.C.

    2004-01-01

    We developed a Late Cretaceous sealevel estimate from Upper Cretaceous sequences at Bass River and Ancora, New Jersey (ODP [Ocean Drilling Program] Leg 174AX). We dated 11-14 sequences by integrating Sr isotope and biostratigraphy (age resolution ??0.5 m.y.) and then estimated paleoenvironmental changes within the sequences from lithofacies and biofacies analyses. Sequences generally shallow upsection from middle-neritic to inner-neritic paleodepths, as shown by the transition from thin basal glauconite shelf sands (transgressive systems tracts [TST]), to medial-prodelta silty clays (highstand systems tracts [HST]), and finally to upper-delta-front quartz sands (HST). Sea-level estimates obtained by backstripping (accounting for paleodepth variations, sediment loading, compaction, and basin subsidence) indicate that large (>25 m) and rapid (???1 m.y.) sea-level variations occurred during the Late Cretaceous greenhouse world. The fact that the timing of Upper Cretaceous sequence boundaries in New Jersey is similar to the sea-level lowering records of Exxon Production Research Company (EPR), northwest European sections, and Russian platform outcrops points to a global cause. Because backstripping, seismicity, seismic stratigraphic data, and sediment-distribution patterns all indicate minimal tectonic effects on the New Jersey Coastal Plain, we interpret that we have isolated a eustatic signature. The only known mechanism that can explain such global changes-glacio-eustasy-is consistent with foraminiferal ??18O data. Either continental ice sheets paced sea-level changes during the Late Cretaceous, or our understanding of causal mechanisms for global sea-level change is fundamentally flawed. Comparison of our eustatic history with published ice-sheet models and Milankovitch predictions suggests that small (5-10 ?? 106 km3), ephemeral, and areally restricted Antarctic ice sheets paced the Late Cretaceous global sea-level change. New Jersey and Russian eustatic estimates

  19. Late Pleistocene Sea Level Stack

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Sea level reconstructions have been created using wide variety of proxies and models. The accuracy of individual sea level reconstructions is limited by measurement, noise, local variations in salinity and temperature, and the assumptions particular to each reconstruction. To address these limitations, we have created a sea level stack (average) which increases the signal-to-noise ratio of sea level estimates by combining 5-7 sea level reconstructions over the last 800 kyr. Principal Component analysis (PCA) of seven sea level records from 0-430 kyr ago shows that 82% of the variance in these records is explained by their first principal component (i.e., the stack). Additionally, a stack of just the 5 longer records that extends to 800 kyr closely matches the timing and amplitude of our seven-record mean. We find that the mean sea level estimate for Marine Isotope Stage (MIS) 5e is 0-4 m above modern, and that the standard deviation of individual estimates is 11 m. Mean sea level estimates for MIS 11 are 12-16 m above modern with a standard deviation of 30 m. Due to the large variability between individual reconstructions, our sea level stack may provide more robust sea level estimates than any single technique.

  20. Tectonics versus eustatic control on supersequences of the Zagros Mountains of Iran

    NASA Astrophysics Data System (ADS)

    Heydari, Ezat

    2008-04-01

    At least 12 km of strata ranging in age from the latest Precambrian to the Recent are exposed in the Zagros Mountains of Iran. This sedimentary cover is characterized by distinct stratal packages separated by major unconformities forming twelve supersequences. They are informally named as: (1) Late Precambrian - Cambrian Hakhamanesh Supersequence, (2) Ordovician Kourosh Supersequence, (3) Silurian Camboojiyeh Supersequence, (4) Devonian Darioush Supersequence, (5) Mississippian - Pennsylvanian Khashayar Supersequence, (6) Permian - Triassic Ashk Supersequence, (7) Jurassic Farhad Supersequence, (8) Early Cretaceous Mehrdad Supersequence, (9) Late Cretaceous Ardavan Supersequence, (10) Paleocene - Oligocene Sassan Supersequence, (11) Oligocene - Miocene Ardeshir Supersequence, and (12) Miocene - Pleistocene Shapour Supersequence. These supersequences and their correlatives in neighboring areas have been used to infer tectonic events. The dominant interpretation has been that local or regional epeirogenic movements were responsible for the formation of these supersequences. Unconformities are considered as indications that epeirogenic movements associated with tectonic events affected the area. The present investigation provides an alternative to the established view of the Phanerozoic supersequences of the Zagros Mountains. A good correlation exists between the lithofacies of supersequences in the Zagros Mountains and the second-order eustatic sea-level changes. Deposition of deep-water, marine shales occurred during periods of eustatic sea-level rise. Platform-wide unconformities coincided with eustatic sea-level lows. In fact, supersequences of the Zagros Mountains are nearly identical to those described from the North American Craton and the Russian Platform suggesting that these stratal packages are global. These observations suggest that supersequences of the Zagros Mountains formed by second order eustatic sea-level changes and not by local or regional

  1. Late Holocene sea level variability and Atlantic Meridional Overturning Circulation

    USGS Publications Warehouse

    Cronin, Thomas M.; Farmer, Jesse R.; Marzen, R. E.; Thomas, E.; Varekamp, J.C.

    2014-01-01

    Pre-twentieth century sea level (SL) variability remains poorly understood due to limits of tide gauge records, low temporal resolution of tidal marsh records, and regional anomalies caused by dynamic ocean processes, notably multidecadal changes in Atlantic Meridional Overturning Circulation (AMOC). We examined SL and AMOC variability along the eastern United States over the last 2000 years, using a SL curve constructed from proxy sea surface temperature (SST) records from Chesapeake Bay, and twentieth century SL-sea surface temperature (SST) relations derived from tide gauges and instrumental SST. The SL curve shows multidecadal-scale variability (20–30 years) during the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA), as well as the twentieth century. During these SL oscillations, short-term rates ranged from 2 to 4 mm yr−1, roughly similar to those of the last few decades. These oscillations likely represent internal modes of climate variability related to AMOC variability and originating at high latitudes, although the exact mechanisms remain unclear. Results imply that dynamic ocean changes, in addition to thermosteric, glacio-eustatic, or glacio-isostatic processes are an inherent part of SL variability in coastal regions, even during millennial-scale climate oscillations such as the MCA and LIA and should be factored into efforts that use tide gauges and tidal marsh sediments to understand global sea level rise.

  2. Mississippi delta-lobe switching during holocene eustatic fluctuations

    SciTech Connect

    Fairbridge, R.W.; Lowrie, A.

    1988-01-01

    Delta formation plays an integral role in basin development at a passive continental margin, with depocenters under eustatic control shifting alternately landward and seaward during time frames ranging from decades to 10/sup 8/ years. The classic Gilbert delta model was hydraulic and climatogenetic, based on his Lake Bonneville experience. The authors challenge the Gilbert model applied to the Mississippi delta, in that the model requires synchronous climatic fluctuations over a 3,327,000 km/sup 2/ drainage basin. From the Mississippi delta apex to the Gulf of Mexico, the dynamic gradient is 1:55,000, although the direct slope, over approx. = 110 km, is 1:20,000. Holocene sea levels fluctuated 1-2 m. During cool periods, as in the Little Ice Age (Maximum AD 1650-1750), sea level dropped 0.5-1 m, changing the dynamic and direct gradients to 1:50,000 and 1:18,000, respectively. During warm periods, as in the Viking times 1,000 years ago, sea level rose 0.5-0.6 m, changing the gradients to 1:78,000 and 1:28,000, respectively. Such large gradient changes increase the opportunities for river entrenchment and stream stability during cool periods and delta-lobe switching during warm periods. Available radiometric dates for the 16 individual delta lobes developed since 6,000 Ma concentrated in six delta complexes and revealed that the 1,000-1,500 yr delta-switching cyclicity roughly coincides with concurrent glacial advances and retreats. C/sub 14/ dates of peats indicate regressions, comparable to those of the North SEa. Gaps in peat-derived dates indicate transgressions.

  3. Regional sea level change in the Thailand-Indonesia region

    NASA Astrophysics Data System (ADS)

    Fenoglio-Marc, L.; Becker, M. H.; Buchhaupt, C.

    2013-12-01

    It is expected that the regional sea level rise will strongly affect particular regions with direct impacts including submergence of coastal zones, rising water tables and salt intrusion into groundwaters. It can possibly also exacerbate other factors as floodings, associated to storms and hurricanes, as well as ground subsidence of anthropogenic nature. The Thailand-Vietnam-Indonesian region is one of those zones. On land, the Chao-Praya and Mekong Delta are fertile alluvial zones. The potential for sea level increases and extreme floodings due to global warming makes the Deltas a place where local, regional, and global environmental changes are converging. We investigate the relative roles of regional and global mechanisms resulting in multidecadal variations and inflections in the rate of sea level change. Altimetry and GRACE data are used to investigate the variation of land floodings. The land surface water extent is evaluated at 25 km sampling intervals over fifteen years (1993-2007) using a multisatellite methodology which captures the extent of episodic and seasonal inundations, wetlands, rivers, lakes, and irrigated agriculture, using passive and active (microwaves and visible observations. The regional sea level change is analysed during the period 1993-2012 using satellite altimetry, wind and ocean model data, tide gauge data and GPS. The rates of absolute eustatic sea level rise derived from satellite altimetry through 19-year long precise altimeter observations are in average higher than the global mean rate. Several tide gauge records indicate an even higher sea level rise relative to land. We show that the sea level change is closely linked to the ENSO mode of variability and strongly affected by changes in wind forcing and ocean circulation. We have determined the vertical crustal motion at a given tide gauge location by differencing the tide gauge sea level time-series with an equivalent time-series derived from satellite altimetry and by computing

  4. Early-mid-Cretaceous evolution in Tethyan reef communities and sea level

    SciTech Connect

    Scott, R.W.

    1988-01-01

    The replacement of corals by rudists in Early Cretaceous reefal communities spanned a 30-m.y. period when sea level rose and drowned continental shelves. During this time corals formed communities in the deeper parts of reefs and rudists occupied the shallow, high-energy habitats. By Aptian time rudists dominated reefs that fringed interior shelf basins and corals formed reefs with rudists on the outer shelf margins. By late Albian coral communities had virtually disappeared, presumably because of complex environmental changes and cycles of organic productivity. Two important events of eustatic sea level rise are represented by unconformities separating carbonate depositional sequences on the Arabian platform that correlate with sequence boundaries on the Gulf Coast platform. Graphic correlation techniques test the synchroneity of these events. A composite standard time scale dates these sea level rises at 115.8 Ma and 94.6 Ma; a third, intra-Albian event at 104.3 Ma is present in many places and may also be eustatic. Associated with these sea level rises were apparent changes in ocean water chemistry as evidenced by changes in isotopes and trace elements, where diagenetic effects can be discounted. During this time the climate became more humid and atmospheric CO/sub 2/ increased. The concomitant environmental changes in the oceanic conditions presumably stressed the deeper coral communities on reefs. The emergence of rudists as reef contributors had a profound effect on Late Cretaceous depositional conditions and the development of hydrocarbon reservoirs.

  5. Early-mid-Cretaceous evolution in Tethyan reef communities and sea level

    SciTech Connect

    Scott, R.W.

    1988-02-01

    The replacement of corals by rudists in Early Cretaceous reefal communities spanned a 30-m.y. period when sea level rose and drowned continental shelves. During this time corals formed communities in the deeper parts of reefs and rudists occupied the shallow, high-energy habitats. By Aptian time rudists dominated reefs that fringed interior shelf basins and corals formed reefs with rudists on the outer shelf margins. By late Albian coral communities had virtually disappeared, presumably because of complex environmental changes and cycles of organic productivity. Two important events of eustatic sea level rise are represented by unconformities separating carbonate depositional sequences on the Arabian platform that correlate with sequence boundaries on the Gulf Coast platform. Graphic correlation techniques test the synchroneity of these events. A composite standard time scale dates these sea level rises at 115.8 Ma and 94.6 Ma; a third, intra-Albian event at 104.3 Ma is present in many places and may also be eustatic. Associated with these sea level rises were apparent changes in ocean water chemistry as evidenced by changes in isotopes and trace elements, where diagenetic effects can be discounted. During this time the climate became more humid and atmospheric CO/sub 2/ increased. The concomitant environmental changes in the oceanic conditions presumably stressed the deeper coral communities on reefs. The emergence of rudists as reef contributors had a profound effect on Late Cretaceous depositional conditions and the development of hydrocarbon reservoirs.

  6. Sea Level Rise Data Discovery

    NASA Astrophysics Data System (ADS)

    Quach, N.; Huang, T.; Boening, C.; Gill, K. M.

    2016-12-01

    Research related to sea level rise crosses multiple disciplines from sea ice to land hydrology. The NASA Sea Level Change Portal (SLCP) is a one-stop source for current sea level change information and data, including interactive tools for accessing and viewing regional data, a virtual dashboard of sea level indicators, and ongoing updates through a suite of editorial products that include content articles, graphics, videos, and animations. The architecture behind the SLCP makes it possible to integrate web content and data relevant to sea level change that are archived across various data centers as well as new data generated by sea level change principal investigators. The Extensible Data Gateway Environment (EDGE) is incorporated into the SLCP architecture to provide a unified platform for web content and science data discovery. EDGE is a data integration platform designed to facilitate high-performance geospatial data discovery and access with the ability to support multi-metadata standard specifications. EDGE has the capability to retrieve data from one or more sources and package the resulting sets into a single response to the requestor. With this unified endpoint, the Data Analysis Tool that is available on the SLCP can retrieve dataset and granule level metadata as well as perform geospatial search on the data. This talk focuses on the architecture that makes it possible to seamlessly integrate and enable discovery of disparate data relevant to sea level rise.

  7. 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

  8. A fractal analysis of quaternary, Cenozoic-Mesozoic, and Late Pennsylvanian sea level changes

    NASA Technical Reports Server (NTRS)

    Hsui, Albert T.; Rust, Kelly A.; Klein, George D.

    1993-01-01

    Sea level changes are related to both climatic variations and tectonic movements. The fractal dimensions of several sea level curves were compared to a modern climatic fractal dimension of 1.26 established for annual precipitation records. A similar fractal dimension (1.22) based on delta(O-18/O-16) in deep-sea sediments has been suggested to characterize climatic change during the past 2 m.y. Our analysis indicates that sea level changes over the past 150,000 to 250,000 years also exhibit comparable fractal dimensions. Sea level changes for periods longer than about 30 m.y. are found to produce fractal dimensions closer to unity and Missourian (Late Pennsylvanian) sea level changes yield a fractal dimension of 1.41. The fact that these sea level curves all possess fractal dimensions less than 1.5 indicates that sea level changes exhibit nonperiodic, long-run persistence. The different fractal dimensions calculated for the various time periods could be the result of a characteristic overprinting of the sediment recored by prevailing processes during deposition. For example, during the Quaternary, glacio-eustatic sea level changes correlate well with the present climatic signature. During the Missourian, however, mechanisms such as plate reorganization may have dominated, resulting in a significantly different fractal dimension.

  9. A fractal analysis of quaternary, Cenozoic-Mesozoic, and Late Pennsylvanian sea level changes

    NASA Technical Reports Server (NTRS)

    Hsui, Albert T.; Rust, Kelly A.; Klein, George D.

    1993-01-01

    Sea level changes are related to both climatic variations and tectonic movements. The fractal dimensions of several sea level curves were compared to a modern climatic fractal dimension of 1.26 established for annual precipitation records. A similar fractal dimension (1.22) based on delta(O-18/O-16) in deep-sea sediments has been suggested to characterize climatic change during the past 2 m.y. Our analysis indicates that sea level changes over the past 150,000 to 250,000 years also exhibit comparable fractal dimensions. Sea level changes for periods longer than about 30 m.y. are found to produce fractal dimensions closer to unity and Missourian (Late Pennsylvanian) sea level changes yield a fractal dimension of 1.41. The fact that these sea level curves all possess fractal dimensions less than 1.5 indicates that sea level changes exhibit nonperiodic, long-run persistence. The different fractal dimensions calculated for the various time periods could be the result of a characteristic overprinting of the sediment recored by prevailing processes during deposition. For example, during the Quaternary, glacio-eustatic sea level changes correlate well with the present climatic signature. During the Missourian, however, mechanisms such as plate reorganization may have dominated, resulting in a significantly different fractal dimension.

  10. Mid-Carboniferous eustatic event

    SciTech Connect

    Saunders, W.B.; Ramsbottom, W.H.C.

    1986-03-01

    Stratigraphic and paleontologic evidence from mid-Carboniferous (Namurian) basin and shelf successions in widely scattered parts of the world indicates that a major eustatic event occurred about 330 Ma. The event began with a regression that is recorded in most shelf sequences, the regression was followed by a brief transgression about 328 Ma, and the event ended with a transgression that flooded large shelf areas about 325 Ma. The Mississippian-Pennsylvanian unconformity in North America is a well-known product of this event, but equally prominent and contemporaneous unconformity surfaces are also present in Europe, North Africa, and elsewhere. The event is believed to have caused numerous extinctions, and it resulted in marked fluctuations in faunal diversity. 94 references, 2 figures.

  11. Paleochannels indicating wet climate and lack of response to lower sea level, southeast Georgia

    NASA Astrophysics Data System (ADS)

    Leigh, David S.; Feeney, Thomas P.

    1995-08-01

    Large meandering paleochannels on the flood plain of the middle Ogeechee River in southeast Georgia represent wet paleoclimate during late Pleistocene and early Holocene time and show no indication of downcutting in response to eustatically lower sea level. Radiocarbon dates indicate that the paleomeanders were active at ˜31 28 ka and ˜8.5 4.5 ka. Bivariate regression models that correlate modern channel dimensions to the discharge of low-magnitude floods (1 5 yr recurrence interval) indicate that paleodischarge of floods during those times was at least double that of modern floods, thus suggesting a wetter paleoclimate. These data corroborate independent studies of pollen and paleoclimate simulations that indicate wet early to middle Holocene (9 3 ka) conditions that were characterized by intensified monsoonal circulation. Paleoclimate conditions at ˜31 28 ka are less well known. Our analysis of the middle Ogeechee River flood plain indicates the absence of base-level response (downcutting) to eustatic sea-level lowering because the beds of the paleochannels are at approximately the same elevation as the bed of the modern channel. This supports recent arguments that the geomorphic response of coastal-plain streams to sea-level lowering is most apparent in deltaic and shelf environments and may not be recognized very far upstream from the coast.

  12. Mesozoic sea level fluctuations documented on Exmouth Plateau off northwestern Australia

    SciTech Connect

    Haq, B.U.; Blome, C.D.; Bralower, T.J.; Brenner, W.; Oda, M.; Siesser, W.; Wonders, A.A.H.

    1989-03-01

    The Exmouth Plateau is uniquely suited to the study of sea level changes because of the existence of an extensive seismic grid and industry well sites, an extended Mesozoic stratigraphic record punctuated with several major unconformities, and the relatively protected position of this high plateau. Thus, documenting sea level fluctuations was one of the major objectives of drilling on the Exmouth Plateau. This documentation depends on their ability to (1) isolate the tectonic overprint from the eustatic signal by retracing the subsidence histories of the drill sites and (2) accurately date the unconformities. Two transects of sites were drilled, one with four sites on the Wombat Plateau and the other with two sites on the central Exmouth Plateau, with one site located relatively proximally and another distally to the source of sediment supply. Preliminary shipboard work indicates that the age of Mesozoic unconformities can be accurately constrained and the subsidence-related tectonic events can be effectively isolated from sea level fluctuations. Sequence stratigraphic analysis of seismic, lithofacies, biofacies, and well-log data document important Upper Triassic sequence boundaries on the Wombat Plateau between the middle and upper Carnian (Norian-Rhaetian boundary) and in the upper most Rhaetian, whose timing and relative magnitude conform well with the eustatic cycle chart. The sequence boundary and systems tracts recognized in the central Exmouth Plateau Barrow Group equivalent strata (Berriasian-Valanginian) also correspond well with the global cycle chart. These preliminary results are of considerable importance in providing a test of the validity of the eustatic model.

  13. Holocene sea level, a semi-empirical contemplation

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  14. Late Cretaceous chronology of large, rapid sea-level changes: Glacioeustasy during the greenhouse world

    USGS Publications Warehouse

    Miller, K.G.; Sugarman, P.J.; Browning, J.V.; Kominz, M.A.; Hernandez, J.C.; Olsson, R.K.; Wright, J.D.; Feigenson, M.D.; Van Sickel, W.

    2003-01-01

    We provide a record of global sea-level (eustatic) variations of the Late Cretaceous (99-65 Ma) greenhouse world. Ocean Drilling Program Leg 174AX provided a record of 11-14 Upper Cretaceous sequences in the New Jersey Coastal Plain that were dated by integrating Sr isotopic stratigraphy and biostratigraphy. Backstripping yielded a Late Cretaceous eustatic estimate for these sequences, taking into account sediment loading, compaction, paleowater depth, and basin subsidence. We show that Late Cretaceous sea-level changes were large (>25 m) and rapid (??? m.y.), suggesting a glacioeustatic control. Three large ??18O increases are linked to sequence boundaries (others lack sufficient ??18O data), consistent with a glacioeustatic cause and with the development of small (<106 km3) ephemeral ice sheets in Antarctica. Our sequence boundaries correlate with sea-level falls recorded by Exxon Production Research and sections from northwest Europe and Russia, indicating a global cause, although the Exxon record differs from backstripped estimates in amplitude and shape.

  15. Recent mass balance of polar ice sheets inferred from patterns of global sea-level change.

    PubMed

    Mitrovica, J X; Tamisiea, M E; Davis, J L; Milne, G A

    2001-02-22

    Global sea level is an indicator of climate change, as it is sensitive to both thermal expansion of the oceans and a reduction of land-based glaciers. Global sea-level rise has been estimated by correcting observations from tide gauges for glacial isostatic adjustment--the continuing sea-level response due to melting of Late Pleistocene ice--and by computing the global mean of these residual trends. In such analyses, spatial patterns of sea-level rise are assumed to be signals that will average out over geographically distributed tide-gauge data. But a long history of modelling studies has demonstrated that non-uniform--that is, non-eustatic--sea-level redistributions can be produced by variations in the volume of the polar ice sheets. Here we present numerical predictions of gravitationally consistent patterns of sea-level change following variations in either the Antarctic or Greenland ice sheets or the melting of a suite of small mountain glaciers. These predictions are characterized by geometrically distinct patterns that reconcile spatial variations in previously published sea-level records. Under the--albeit coarse--assumption of a globally uniform thermal expansion of the oceans, our approach suggests melting of the Greenland ice complex over the last century equivalent to -0.6 mm yr(-1) of sea-level rise.

  16. Ostracode turnover and sea-level changes associated with the Paleocene-Eocene thermal maximum

    NASA Astrophysics Data System (ADS)

    Speijer, Robert P.; Morsi, Abdel-Mohsen M.

    2002-01-01

    The ostracode response to oceanographic changes during the Paleocene-Eocene thermal maximum (PETM, ca. 55 Ma) is largely unknown. The Gebel Duwi section (Egypt) provides a detailed ostracode record across the PETM in a middle neritic setting. Quantitative analysis of this record reveals two significant results. (1) The PETM is marked by a sharp faunal turnover, as indicated by abundance changes, local extinctions, and immigrations. This turnover punctuated a gradual basin-wide faunal transition. (2) During the ˜60 k.y. period prior to the PETM, relative sea level fell rapidly by ˜15 m. This sea-level fall was followed by an ˜20 m sea-level rise during the PETM. A possible eustatic control on these fluctuations suggests the presence of a cryosphere and variations in its size during this time of global warmth.

  17. Sea Level Rise in Tuvalu

    NASA Astrophysics Data System (ADS)

    Lin, C. C.; Ho, C. R.; Cheng, Y. H.

    2012-04-01

    Most people, especially for Pacific Islanders, are aware of the sea level change which may caused by many factors, but no of them has deeper sensation of flooding than Tuvaluan. Tuvalu, a coral country, consists of nine low-lying islands in the central Pacific between the latitudes of 5 and 10 degrees south, has the average elevation of 2 meters (South Pacific Sea Level and Climate Monitoring Project, SPSLCMP report, 2006) up to sea level. Meanwhile, the maximum sea level recorded was 3.44m on February 28th 2006 that damaged Tuvaluan's property badly. Local people called the flooding water oozes up out of the ground "King Tide", that happened almost once or twice a year, which destroyed the plant, polluted their fresh water, and forced them to colonize to some other countries. The predictable but uncontrollable king tide had been observed for a long time by SPSLCMP, but some of the uncertainties which intensify the sea level rise need to be analyzed furthermore. In this study, a span of 18 years of tide gauge data accessed from Sea Level Fine Resolution Acoustic Measuring Equipment (SEAFRAME) are compared with the satellite altimeter data accessed from Archiving Validation and Interpretation of Satellite Data in Oceanography (AVISO). All above are processed under the limitation of same time and spatial range. The outcome revealed a 9.26cm difference between both. After the tide gauge data shifted to the same base as altimeter data, the results showed the unknown residuals are always positive under the circumstances of the sea level rise above 3.2m. Apart from uncertainties in observing, the residual reflected unknown contributions. Among the total case number of sea level rise above 3.2m is 23 times, 22 of which were recorded with oceanic warm eddy happened simultaneously. The unknown residual seems precisely matched with oceanic warm eddies and illustrates a clear future approach for Tuvaluan to care for.

  18. Intermittent sea-level acceleration

    NASA Astrophysics Data System (ADS)

    Olivieri, M.; Spada, G.

    2013-10-01

    Using instrumental observations from the Permanent Service for Mean Sea Level (PSMSL), we provide a new assessment of the global sea-level acceleration for the last ~ 2 centuries (1820-2010). Our results, obtained by a stack of tide gauge time series, confirm the existence of a global sea-level acceleration (GSLA) and, coherently with independent assessments so far, they point to a value close to 0.01 mm/yr2. However, differently from previous studies, we discuss how change points or abrupt inflections in individual sea-level time series have contributed to the GSLA. Our analysis, based on methods borrowed from econometrics, suggests the existence of two distinct driving mechanisms for the GSLA, both involving a minority of tide gauges globally. The first effectively implies a gradual increase in the rate of sea-level rise at individual tide gauges, while the second is manifest through a sequence of catastrophic variations of the sea-level trend. These occurred intermittently since the end of the 19th century and became more frequent during the last four decades.

  19. Sea-level curve for Pennsylvanian eustatic marine transgressive-regressive depositional cycles along midcontinent outcrop belt, North America

    NASA Astrophysics Data System (ADS)

    Heckel, Philip H.

    1986-04-01

    At least 55 cycles of marine inundation and withdrawal are recognized in the mid-Desmoinesian to mid-Virgilian Midcontinent outcrop sequence in North America. They range from widespread major cycles (classic cyclothems) with deep-water facies extending across the northern shelf, through intermediate cycles persisting as marine horizons across the shelf, to minor cycles developed on the lower shelf or as parts of major cycles. Biostratigraphic differentiation of the cycles should establish interbasinal correlation on a scale fine enough to allow evaluation of differential tectonics and sedimentation. Sequential groupings of cycles are more irregular than proposed megacyclothems or mesothems, but they may be obscured by the distinctness of the major cyclothems. Estimates of cycle periods range from about 40 to 120 × 103 yr for the minor cycles up to about 235 to 400 × 103 yr for the major cyclothems. The range for all cycles corresponds well to the range of periods of Earth's orbital parameters that constitute the Milankovitch insolation theory for the Pleistocene ice ages, and it further supports Gondwanan glacial control for the Pennsylvanian cycles. Even though the dominant period of the major Pennsylvanian cyclothems is up to four times longer than the dominant 100 000-yr period in the Pleistocene, the shapes of both curves display rapid marine transgression (rapid melting of ice caps) and slow interrupted regression (slow buildup of ice caps), which suggest similar linkages between the climatic effects of the orbital parameters and ice-cap formation and melting, at the two different scales, widely separated in time.

  20. Paleodepth variations on the Eratosthenes Seamount (Eastern Mediterranean): sea-level changes or subsidence?

    NASA Astrophysics Data System (ADS)

    Spezzaferri, S.; Tamburini, F.

    2007-09-01

    The Eratosthenes Seamount (Eastern Mediterranean) is interpreted as a crustal block in process of break up in response to subduction and incipient collision of the African and Eurasian Plates. Subsidence is considered to be the mechanism triggering the Messinian to Pleistocene water deepening above this unique structure. However, the application of a recently developed transfer equation of depth range distribution of benthic foraminifera indicates that sea-level changes may also have played a role, although it was generally minor. In particular, we suggest that across the Miocene/Pliocene boundary and during the Pliocene-Pleistocene, the eustatic signal is frequently coupled with uplifts and subsidence. The uplift of Cyprus across the Pliocene-Pleistocene transition is clearly recorded in the paleodepth curve. Micropaleontological studies and the use of this transfer equation based on the distribution of benthic foraminifera proves to be useful when studying the paleodepth history of complex sites, where tectonic and eustatic signals combine. We also show that marginal seas record global sea-level changes that can be identified even in tectonically active settings.

  1. Possible Evidence of Multiple Sea Level Oscillations in the Seychelles During the Last Interglacial

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    In search of a eustatic sea level signal on glacial-interglacial timescales, the Seychelles ranks as one of the best places on the planet to study. Owing to its far-field location with respect to the former margins of Northern Hemisphere ice sheets, glacio-hydro-isostatic models predict that relative sea level in the Seychelles should lie within a few meters of the globally averaged eustatic signal during interglacial periods. We have surveyed and dated fossil coral reefs from the last interglacial period to determine the magnitude of peak sea level and to assess sedimentologic evidence of potential sea level oscillations. Numerous outcrops we studied in detail exhibit a stratigraphic sequence comprised of in situ coralgal framework at the base, capped by thick coralline algae crusts, and overlain by coral rubble deposits. We also observed a succession of three stacked coralgal reefs within a single outcrop, separated by hardgrounds that have been bored by molluscs. In general, the succession within each reef unit consists of interlayered corals and crusts of coralline algae-vermetid gastropods-encrusting foraminifera. The lower two reef units are capped by a well-cemented 5 to 10 cm thick carbonate mud layer that is heavily bored by molluscs. These two surfaces may represent exposure surfaces during brief sea level oscillations, where sea level fell and exposed the top of the reef sequence, which was subsequently bored when sea level rose again and reef growth resumed. The elevations of the corals in each reef unit provide minimum elevations of sea level during each of the three pulses of sea level highstands during the last interglacial period. Significantly, since many of these corals are capped by thick coralline algae layers that contain vermetid gastropods and encrusting foraminifera that are indicative of the intertidal zone, there is strong evidence that these corals grew in extremely shallow water, providing a robust indication of sea level position. These

  2. Relative sea-level changes during Middle Ordovician through Mississippian deposition in the Iowa area, North American craton

    USGS Publications Warehouse

    Witzke, B.J.; Bunker, B.J.; ,

    1996-01-01

    The Tippecanoe and Kaskaskia cratonic megasequences in the Iowa area are subdivided into a succession of third-order transgressive-regressive (T-R) depositional cycles of ~1 to 3 m.y. duration. Cratonic deposition in the Iowa area is categorized into two broad-scale facies groupings, each dominated by shallowing-upward patterns: 1) an inner shelf with shallow subtidal to peritidal facies, and 2) a middle shelf dominated by subtidal facies. Relative changes in sea level, as documented in the cycles, are considered primarily to reflect eustatic patterns, but local variations in subsidence history and sedimentation rates complicate interpretations of the eustatic signal. Minor modification of certain sequence stratigraphic paradigms that were developed originally for continental margin settings is suggested for application to the Iowa cratonic cycles.

  3. Post-glacial sea-level change along the Pacific coast of North America

    NASA Astrophysics Data System (ADS)

    Shugar, Dan H.; Walker, Ian J.; Lian, Olav B.; Eamer, Jordan B. R.; Neudorf, Christina; McLaren, Duncan; Fedje, Daryl

    2014-08-01

    Sea-level history since the Last Glacial Maximum on the Pacific margin of North America is complex and heterogeneous owing to regional differences in crustal deformation (neotectonics), changes in global ocean volumes (eustasy) and the depression and rebound of the Earth's crust in response to ice sheets on land (isostasy). At the Last Glacial Maximum, the Cordilleran Ice Sheet depressed the crust over which it formed and created a raised forebulge along peripheral areas offshore. This, combined with different tectonic settings along the coast, resulted in divergent relative sea-level responses during the Holocene. For example, sea level was up to 200 m higher than present in the lower Fraser Valley region of southwest British Columbia, due largely to isostatic depression. At the same time, sea level was 150 m lower than present in Haida Gwaii, on the northern coast of British Columbia, due to the combined effects of the forebulge raising the land and lower eustatic sea level. A forebulge also developed in parts of southeast Alaska resulting in post-glacial sea levels at least 122 m lower than present and possibly as low as 165 m. On the coasts of Washington and Oregon, as well as south-central Alaska, neotectonics and eustasy seem to have played larger roles than isostatic adjustments in controlling relative sea-level changes.

  4. Post-Miocene diagenetic and eustatic history of Enewetak Atoll: Model and data comparison

    NASA Astrophysics Data System (ADS)

    Quinn, Terrence M.; Matthews, R. K.

    1990-10-01

    The post-Miocene diagenetic and eustatic history of Enewetak Atoll was investigated using a one-dimensional forward model. Comparison of model and data suggests that the post-Miocene history of Enewetak Atoll was dominated by multiple episodes of meteoric phreatic diagenesis attendant with high-frequency (104 to 105 yr) fluctuations in sea level and a subsidence rate of 39.0 m/m.y. Sensitivity testing indicates that subaerial erosion results in the preservation of additional subaerial unconformities because stratigraphic shortening permits a succeeding sea-level rise to flood the exposure surface and deposit sediment, whereas without subaerial erosion this sea-level rise would be recorded as a paleophreatic lens. Model results indicate that less than 10% of lapsed time is recorded by sediment deposition during periods of high-frequency changes in sea level. Incompleteness of the stratigraphic record suggests that magnetostratigraphy may give erroneous ages for shallow-marine carbonate sequences deposited during times of high-frequency changes in sea level and frequent magnetic polarity reversals.

  5. Constraining mid to late Holocene sea level change of Society Islands, French Polynesia

    NASA Astrophysics Data System (ADS)

    Juma Rashid, Rashid; Eisenhauer, Anton; Liebetrau, Volker; Fietzke, Jan; Dullo, Christian; Camoin, Gilbert; Hallmann, Nadine

    2013-04-01

    In global average rising eustatic sea level of several centimeters per decade is predicted for the near future as a consequence of seawater warming and partial melting of the Greenland ice cap (Milne et al., 2009). Beside CO2 induced ocean warming local sea-level amplitudes may also vary although no extra water has been added to or extracted from the ocean due to post-glacial geoid reorganization, as a consequence of the emergence of the once glaciated areas and the ocean siphoning effect (Milne et al., 2009; Mitrovica and Peltier, 1991; Mitrovica and Milne, 2002). However, previous research on sea level change was focused on sea-level rise that occurred between the "Last Glacial Maximum, LGM" ~18ka before present (BP) and the so called "Holocene Sea Level Maximum, HSLM" ~6ka BP. Information about sea-level change after the HSLM are rare because the Late Holocene was considered to be climatically stable with minor to negligible sea-level oscillations and amplitudes. Here we present U/Th dated fossil corals from conglomerate reef platforms of three islands (Moorea, Huahine and Bora Bora) of the Society Islands, French Polynesia. The fossil coral data constrain the timing and amplitude of sea-level variations after the HSLM. We found that sea level reached a subsidence corrected minimum position of ~1.5±0.2m above present sea level (apsl) at ~5.4ka. Sea level then remained at this position with probably minor amplitudinal variations for ~3ka and then dropped to the present position at ~1.9ka. Note, that our study does not provide any data on sea-level position from ~1.8ka to the Present. Theoretical predictions (Mitrovica and Milne, 2002) taking the ocean siphoning effect into account predicted a sea level of ~3m apsl at ~5ka and a constantly decreasing sea level from 5ka to the present. This is in contrast to our observations indicating a more or less constant sea level between 5ka and 1.9ka followed by a abrupt drop of sea level to the present position. Although

  6. Seismic sequence stratigraphy of Miocene deposits related to eustatic, tectonic and climatic events, Cap Bon Peninsula, northeastern Tunisia

    NASA Astrophysics Data System (ADS)

    Gharsalli, Ramzi; Zouaghi, Taher; Soussi, Mohamed; Chebbi, Riadh; Khomsi, Sami; Bédir, Mourad

    2013-09-01

    The Cap Bon Peninsula, belonging to northeastern Tunisia, is located in the Maghrebian Alpine foreland and in the North of the Pelagian block. By its paleoposition, during the Cenozoic, in the edge of the southern Tethyan margin, this peninsula constitutes a geological entity that fossilized the eustatic, tectonic and climatic interactions. Surface and subsurface study carried out in the Cap Bon onshore area and surrounding offshore of Hammamet interests the Miocene deposits from the Langhian-to-Messinian interval time. Related to the basin and the platform positions, sequence and seismic stratigraphy studies have been conducted to identify seven third-order seismic sequences in subsurface (SM1-SM7), six depositional sequences on the Zinnia-1 petroleum well (SDM1-SDM6), and five depositional sequences on the El Oudiane section of the Jebel Abderrahmane (SDM1-SDM5). Each sequence shows a succession of high-frequency systems tract and parasequences. These sequences are separated by remarkable sequence boundaries and maximum flooding surfaces (SB and MFS) that have been correlated to the eustatic cycles and supercycles of the Global Sea Level Chart of Haq et al. (1987). The sequences have been also correlated with Sequence Chronostratigraphic Chart of Hardenbol et al. (1998), related to European basins, allows us to arise some major differences in number and in size. The major discontinuities, which limit the sequences resulted from the interplay between tectonic and climatic phenomena. It thus appears very judicious to bring back these chronological surfaces to eustatic and/or local tectonic activity and global eustatic and climatic controls.

  7. Deciphering the mid-Carboniferous eustatic event in the central Appalachian foreland basin, southern West Virginia, USA

    USGS Publications Warehouse

    Blake, B.M.; Beuthin, J.D.

    2008-01-01

    A prominent unconformity, present across shallow shelf areas of the Euramerican paleoequatorial basins, is used to demark the boundary between the Mississippian and Pennsylvanian subsystems. This unconformity, the mid-Carboniferous eustatic event, is generally attributed to a major glacio-eustatic sea-level fall. Although a Mississippian-Pennsylvanian unconformity is recognized throughout most of the Appalachian region, the record of the mid-Carboniferous eustatic event in the structurally deepest part of the basin has been controversial. Based on early reports that suggested the most complete Pennsylvanian section was present in southern West Virginia, various conceptual depositional models postulated continuous sedimentation between the youngest Mississippian Bluestone Formation and the oldest Penn-sylvanian Pocahontas Formation. In contrast, tabular-erosion models envisioned axial drainage systems that evolved in response to changing basin dynamics. These models predicted a Mississippian-Pennsylvanian unconformity. All these models suffered from a lack of biostratigraphic control. The presence of a sub-Pocahontas paleovalley, herein named the Lashmeet paleovalley, has been confirmed in southern West Virginia. The Lashmeet paleovalley was incised over 35 m into Bluestone strata and filled by lithic sands derived from the Appalachian orogen to the northeast and east. The polygenetic Green Valley paleosol complex marks the Bluestone-Pocahontas contact on associated interfluves. Together, these features indicate a substantial period of subaerial exposure and argue strongly in favor of a Mississippian-Pennsylvanian unconformity. Paleontologic data from the Bluestone Formation, including marine invertebrates and conodonts from the marine Bramwell Member and paleofloral data, support a late, but not latest, Arnsbergian age assignment. Marine fossils are not known from the Pocahontas Formation, but macrofloral and palynomorph taxa support a Langsettian age for most of

  8. Sedimentary architecture of the Bohai Sea China over the last 1 Ma and implications for sea-level changes

    NASA Astrophysics Data System (ADS)

    Shi, Xuefa; Yao, Zhengquan; Liu, Qingsong; Larrasoaña, Juan Cruz; Bai, Yazhi; Liu, Yanguang; Liu, Jihua; Cao, Peng; Li, Xiaoyan; Qiao, Shuqing; Wang, Kunshan; Fang, Xisheng; Xu, Taoyu

    2016-10-01

    Sedimentary architecture dominated by transgression-regression cycles in the shallow Bohai shelf region contains information about global sea-level, climate and local tectonics. However, previous studies of transgression-regression cycles in this region at orbital timescales that extend back to the early Pleistocene are sparse, mainly because of the shortage of well-dated long cores. Although transgression-regression sedimentary cycles in the region have been interpreted in terms of local tectonics, sea-level, and climate change, the detailed structure of marine transgressions and their significance for Quaternary global sea-level variations remains to be examined. In this study, we present an integrated sedimentological, geochemical and paleontological study of a 212.4 m (∼1 Ma) core (BH08) recovered from the Bohai Sea, China, for which an astronomically-based age model is available. Correspondence between marine-terrestrial sedimentary cycles and global sea-level fluctuations suggests that stacking of marine and terrestrial sediments was driven mainly by glacio-eustatic sea-level fluctuations in a context in which tectonic subsidence was largely balanced by sediment supply over the last ∼1 Ma. We report a dominant 100-kyr cycle beginning at ∼650 ka, which reflects the worldwide influence of the mid-Pleistocene transition (MPT) in sea-level records. We find that neritic deposits after the MPT were relatively thicker than before the MPT, which indicates an important control of the MPT on sedimentary architecture through lengthening of the duration of sea-level highstands.

  9. 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.

  10. Glaciers and Sea Level Rise

    NASA Image and Video Library

    2017-09-28

    This ice cave in Belcher Glacier (Devon Island, Canada) was formed by melt water flowing within the glacier ice. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Angus Duncan, University of Saskatchewan 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

  11. Glaciers and Sea Level Rise

    NASA Image and Video Library

    2017-09-28

    Melt water ponded at surface in the accumulation zone of Columbia Glacier, Alaska, in July 2008. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: W. Tad Pfeffer, University of Colorado at Boulder 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

  12. Glaciers and Sea Level Rise

    NASA Image and Video Library

    2017-09-28

    Summit camp on top of the Austfonna Ice Cap in Svalbard (Norwegian Arctic). To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Thorben Dunse, University of Oslo 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

  13. Glaciers and Sea Level Rise

    NASA Image and Video Library

    2007-05-17

    Small valley glacier exiting the Devon Island Ice Cap in Canada. To learn about the contributions of glaciers to sea level rise, visit: http://www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Alex Gardner, Clark University 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

  14. Eustatic and tectonic control of sedimentation in the Pennsylvanian strata of the Central Appalachian Basin

    SciTech Connect

    Chesnut, D.R. Jr. . Kentucky Geological Survey)

    1992-01-01

    Analysis of the Breathitt Group of the Central Appalachian Basin reveals three orders of depositional cycles or trends. The Breathitt coarsening-upward trend (20 million years (my)) represents increasing intensity of the Alleghenian Orogeny. The major transgression (MT) cycle (2.5 my) was controlled by an unknown eustatic or tectonic mechanism. The major coal beds and intervening strata make up the coal-clastic cycle (CC cycle) (=Appalachian cyclothem) which has a 0.4 my periodicity. This periodicity supports eustatic control of sedimentation modulated by an orbital periodicity. Extensive coastal peats deposited at lowstand (CC cycle) were preserved as coals, whereas highstand peats were eroded during the subsequent drop in sea level. Autocyclic processes such as delta switching and avulsion occurred within CC cycles. An Early Pennsylvanian unconformity represents uplift and erosion of mid-Carboniferous foreland basin deposits. Alluvial deposits (Breathitt Group) derived from the highlands were transported to the northwest toward the forebulge. During lowstand, the only outlet available to further sediment transport (Lee sandstones) was toward the southwest (Ouachita Trough), along the Black Warrior-Appalachian foreland basins. The Middle Pennsylvanian marks a period of intermittent overfilling of the foreland basin and cresting of the forebulge. Marine transgressions entered through the foreland basins and across saddles in the forebulge. After the Ouachita Trough was destroyed during the late Middle Pennsylvanian, marine transgressions migrated only across saddles in the forebulge. In the Late Pennsylvanian, marine waters entered the basin only across the diminished forebulge north of the Jessamine Dome.

  15. Sea level change and glacio-hydro isostasy deduced from some Italian marine notches

    NASA Astrophysics Data System (ADS)

    Antonioli, F.; Carulli, G. B.; Marocco, R.

    2003-04-01

    Sea level change along the Italian coast is the sum of eustatic, glacio-hydro-isostatic, and tectonic factors (Lambeck et al.,submitted 2003). Marine notches are frequently found in limestones lithologies. A marine notch is normally carved in 2-5 centuries and this range depends upon the lithology. The use of notches as sea level marker in a low-tide seas as Mediterranean, is crucial to study the sea level change. In many Italian tectonically active coastal zone uplifting (eastern Sicily) o subsiding (Trieste, north Adriatic sea) the Present day marine notches are lacking because the tectonic ratea are faster than the possibility of carving. A submerged marine notch was discovered at Trieste at an altitude (tidally corrected) of -1.9 m; a similar notch, at an altitude of -0.6, was measured by Fouache et al., (2000) along Croatian coast, but while at Trieste the Present day marine notch is lacking, along Croatian coast, instead, this notch is well carved. This should result from complex equilibrium between eustatic sea level, hydro-glacio isostasy and tectonic that must be different between Trieste and Croatian coast. The deeper submerged marine notch on limestones of Trieste is suitable with an Plio-quaternary tilting of the Carso plateau, gently dipping to NW, as illustrated by other observations by Carulli et al.,(1980). This fact may be related also to the increasing weight of the external fronts of the South-alpine chain and to the External Dinarides one. Both, characterized by strong seismic activity and consequent neotectonics effects, are rising and advancing not far from Trieste. In a tectonically stable zone as Gaeta (Central Tyrrhenian sea) the submerged cliff immediately belove the present day marine notch was monitored (Antonioli, 1989) and was discovered a smoothed morphology similar to a very large marine notch. Such composite morphology made off from two different notches (in 4-5 meters of submerged cliff) is present also as fossil and related to

  16. Sea level change since the Pliocene - a new formalism for predicting sea level in the presence of dynamic topography and isostasy

    NASA Astrophysics Data System (ADS)

    Austermann, Jacqueline; Rovere, Alessio; Moucha, Robert; Mitrovica, Jerry X.; Rowley, David B.; Forte, Alessandro M.; Raymo, Maureen E.

    2014-05-01

    Dynamic topography (DT), as reflected in local sea level change, provides a unique lens for studying the imprint of deep Earth dynamics on the Earth's surface. The elevation of paleo-shorelines over long time scales is, however, not only perturbed by DT but also by glacial isostatic adjustment (GIA) and eustatic changes in sea level. Isolating these contributions is essential for efforts to constrain past changes in ice volume or mantle convection models. Previous studies have performed this separation by modeling dynamic topography and superimposing the signal on the elevation of a GIA-corrected paleo-shoreline. However, this approach neglects deformation of the Earth in response to changes in the ocean load and geometry driven by DT. We describe a generalized, gravitationally self-consistent framework for computing sea-level changes that incorporates DT and GIA. The formalism is based on a sea-level theory developed within the GIA community that takes accurate account of viscoelastic deformation of the solid Earth, perturbations in the gravity field, migration of shorelines and the feedback into sea-level of contemporaneous (load-induced) changes in Earth rotation. Specifically, dynamic topography is introduced as a perturbation to the elevation of the solid surface that does not load the Earth because it is dynamically supported. However, water that is displaced by DT is allowed to redistribute, perturb the gravitational field and load (or unload) the ocean floor wherever the water column is increased (or decreased). The problem is complicated by plate tectonics, which (in a tectonic reference frame) leaves changes in topography and DT undefined in areas of the ocean floor where plates have been subducted. We interpolate these regions by imposing mass conservation of both the solid Earth and water on the reconstructed topography. We use the new formalism to calculate sea level change since the mid-Pliocene (3 Ma) using recent global simulations of dynamic

  17. Late mid-Holocene sea-level oscillation: A possible cause

    NASA Astrophysics Data System (ADS)

    Scott, D. B.; Collins, E. S.

    Sea level oscillated between 5500 and 3500 years ago at Murrells Inlet, South Carolina, Chezzetcook and Baie Verte, Nova Scotia and Montmagny, Quebec. The oscillation is well constrained by foraminiferal marsh zonations in three locations and by diatoms in the fourth one. The implications are: (1) there was a eustatic sea-level oscillation of about 2-10 m in the late mid-Holocene on the southeast coast of North America (South Carolina to Quebec) that is not predicted by present geophysical models of relative sea-level change; (2) this oscillation coincides with oceanographic cooling on the east coast of Canada that we associate with melting ice; and (3) this sea- level oscillation/climatic event coincides exactly with the end of pyramid building in Egypt which is suggested to have resulted from a climate change (i.e. drought, cooling). This sea-level/climatic change is a prime example of feedback where climatic warming in the mid-Holocene promoted ice melt in the Arctic which subsequently caused climatic cooling by opening up Arctic channels releasing cold water into the Inner Labrador Current that continued to intensify until 4000 years ago. This sea-level event may also be the best way of measuring when the final ice melted since most estimates of the ages of the last melting are based on end moraine dates in the Arctic which may not coincide with when the last ice actually melted out, since there is no way of dating the final ice positions.

  18. Holocene Sea-Level Database For The Caribbean Region

    NASA Astrophysics Data System (ADS)

    Khan, N. S.; Horton, B.; Engelhart, S. E.; Peltier, W. R.; Scatena, F. N.; Vane, C. H.; Liu, S.

    2013-12-01

    Holocene relative sea-level (RSL) records from far-field locations are important for understanding the driving mechanisms controlling the nature and timing of the mid-late Holocene reduction in global meltwaters and providing background rates of late Holocene RSL change with which to compare the magnitude of 20th century RSL rise. The Caribbean region has traditionally been considered far-field (i.e., with negligible glacio-isostatic adjustment (GIA) influence), although recent investigations indicate otherwise. Here, we consider the spatial variability in glacio-isostatic, tectonic and local contributions on RSL records from the circum-Caribbean region to infer a Holocene eustatic sea-level signal. We have constructed a database of quality-controlled, spatially comprehensive, Holocene RSL observations for the circum-Caribbean region. The database contains over 500 index points, which locate the position of RSL in time and space. The database incorporates sea-level observations from a latitudinal range of 5°N to 25°N and longitudinal range of 55°W to 90°W. We include sea-level observations from 11 ka BP to present, although the majority of the index points in the database are younger than 8 ka BP. The database is sub-divided into 13 regions based on the distance from the former Laurentide Ice Sheet and regional tectonic setting. The index points were primarily derived from mangrove peat deposits, which in the Caribbean form in the upper half of the tidal range, and corals (predominantly Acropora palmata), the growth of which is constrained to the upper 5 m of water depth. The index points are classified on the basis of their susceptibility to compaction (e.g., intercalated, basal). The influence of temporal changes in tidal range on index points is also considered. The sea-level reconstructions demonstrate that RSL did not exceed the present height (0 m) during the Holocene in the majority of locations, except at sites in Suriname/Guayana and possibly Trinidad

  19. The sea level budget along the Northwest Atlantic coast: GIA, mass changes and deep sea-shelf interaction

    NASA Astrophysics Data System (ADS)

    Frederikse, T.; Riva, R.; Simon, K.; Kleinherenbrink, M.

    2016-12-01

    Sea level along the Atlantic coast of the United States north of Cape Hatteras shows trends and accelerations above the global average. In this study we look at the individual contributors to sea level changes in this region over the period 1958-2014 and compare the sum of contributors with observations from tide gauges and GPS stations. Both observations are analyzed in a self-consistent framework that takes eustatic effects, geoid changes and solid earth deformation, resulting from both Glacial Isostatic Adjustment (GIA) and present-day mass redistribution into account. An updated data-driven model is used to constrain the GIA signal in the region, of which large parts are affected by the forebulge collapse, causing subsidence. The GIA signal explains the largest part of the observed sea level and vertical land motion trends, as well as a large fraction of the inter-station trend differences. Present-day mass redistribution caused by ice sheet and glacier melt, dam retention and groundwater depletion account for a smaller fraction of the observed trends. Altimetry and hydrographic observations and model results show that deep steric variability in the Northwest Atlantic results in a bottom pressure signal over the shelf, which explains, after removing regional meteorological effects, the vast majority of the observed decadal coastal variability and is responsible for a substantial upward trend. The sum of the individual processes explain most of the observed decadal sea level variability, as well as the observed linear trends in both sea level and vertical land motion. The trends in present-day ice mass loss and dynamic sea level do not deviate substantially from global-mean values. A significant sea level acceleration is observed, of which about half can be attributed to mass redistribution processes. The other half can be attributed to steric expansion in the Northwest Atlantic, although separating a secular acceleration from internal variability remains a

  20. Dynamics of sea level variations in the coastal Red Sea

    NASA Astrophysics Data System (ADS)

    Churchill, James; Abulnaja, Yasser; Nellayaputhenpeedika, Mohammedali; Limeburner, Richard; Lentz, Steven

    2016-04-01

    Sea level variations in the central Red Sea coastal zone span a range of roughly 1.2 m. Though relatively small, these water level changes can significantly impact the environment over the shallow reef tops prevalent in the central Red Sea, altering the water depth by a factor or two or more. While considerable scientific work has been directed at tidal and seasonal variations of Red Sea water level, very little attention has been given to elevation changes in an 'intermediate' frequency band, with periods of 2-30 d, even though motions in this band account for roughly half of the sea level variance in central Red Sea. We examined the sea level signal in this band using AVISO sea level anomaly (SLA) data, COARDAS wind data and measurements from pressure sensors maintained for more than five years at a number of locations in Saudi Arabian coastal waters. Empirical orthogonal function analysis of the SLA data indicates that longer-period (10-30 d) sea level variations in the intermediate band are dominated by coherent motions in a single mode that extends over most of the Red Sea axis. Idealized model results indicate that this large-scale mode of sea level motion is principally due to variations in the large-scale gradient of the along-axis wind. Our analysis indicates that coastal sea level motions at shorter periods (2-10 d) are principally generated by a combination of direct forcing by the local wind stress and forcing associated with large-scale wind stress gradients. However, also contributing to coastal sea level variations in the intermediate frequency band are mesoscale eddies, which are prevalent throughout the Red Sea basin, have a sea level signal of 10's of cm and produce relatively small-scale (order 50 km) changes in coastal sea level.

  1. Cold climate deglaciation prior to termination 2 implied by new evidence for high sea-levels at 132 KA

    SciTech Connect

    Johnson, R.G. . Dept. of Geology and Geophysics)

    1992-01-01

    Radioisotope dating of corals from reefs and beaches suggests a high sea stand just prior to termination 2. Lack of precision in the ages, stratigraphic uncertainties, and possible diagenetic alterations in the corals have prevented a widespread acceptance of this sea stand. These disadvantages can be avoided by an approach that uses differential uplift measurements to determine the duration of the interval of generally high sea-levels. The last interglacial terrace on Barbados has features indicating two intervals of constant sea-level: an older wave-cut at the inshore edge of the terrace, and a younger cut formed near present eustatic sea-level, below the crest, and just before the earliest Wisconsin glacial buildup. The differential uplift between these two features, measured at five locations having uplift rates between 0.18 and 0.39m/ka, yields a eustatic sea-level differences of 5.4m and a minimal duration of 12.1 [+-] 0.6ka between the two still stands. The assigned age of the younger wave-cut is 120 [+-] 0.5ka, based on sea-level regression due to ice sheet buildup implied by a Little Ice Age analog and rapidly falling Milankovitch summer insolation. The resulting minimal age of the first high sea-stand is 132.1 [+-] 1.1ka, about 7ka before termination 2. This age implies a major early deglaciation caused by a deficit of moisture transported to the great ice sheets, and occurring under relatively cold climate conditions.

  2. A new Holocene sea-level database for the US Gulf Coast: Improving constraints for past and future sea levels

    NASA Astrophysics Data System (ADS)

    Hijma, M.; Tornqvist, T. E.; Hu, P.; Gonzalez, J.; Hill, D. F.; Horton, B. P.; Engelhart, S. E.

    2011-12-01

    The interpretation of present-day sea-level change, as well as the prediction of future relative sea-level (RSL) rise and its spatial variability, depend increasingly on the ability of glacial isostatic adjustment (GIA) models to reveal non-eustatic components of RSL change. GIA results from the redistribution of mass due to the growth and decay of ice sheets. As a consequence, formerly ice-covered areas are still rebounding and currently experience RSL fall, while in other areas the rate of RSL rise is enhanced due to glacial forebulge collapse. The development of GIA models relies to a large extent on the availability of quality-controlled Holocene RSL data. There is thus an urgent need for systematically compiled and publicly available databases of geological RSL data that can be used not only for the purposes mentioned above, but also can serve to underpin coastal management and policy decisions. We have focused our efforts to develop a Holocene sea-level database for the Atlantic and Gulf coasts of the US. Many of the research problems that can be addressed with this sea-level database revolve around the identification of crustal motions due to glacial forebulge collapse that affects the entire region and likely extends beyond South Florida. For the east coast, GIA-related subsidence rates have been calculated with unprecedented precision: <0.8 mm a-1 in Maine, increasing to rates of 1.7 mm a-1 in Delaware, and a return to rates <0.9 mm a-1 in the Carolinas. Here, we first define our methodology to reconstruct RSL, with particular reference to the quantification of age and elevation errors. Many sea-level indicators are related to a specific tide level (e.g., peat that formed between highest astronomical tide and mean high water level). We use paleotidal modeling to account for any changes during the Holocene. We furthermore highlight a number of errors associated with 14C dating that have rarely, if ever, been considered in previous studies of this nature

  3. Glaciers and Sea Level Rise

    NASA Image and Video Library

    2017-09-27

    Calving front of the Perito Moreno Glacier (Argentina). Contrary to the majority of the glaciers from the southern Patagonian ice field, the Perito Moreno Glacier is currently stable. It is also one of the most visited glaciers in the world. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Etienne Berthier, Université de Toulouse 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

  4. Glaciers and Sea Level Rise

    NASA Image and Video Library

    2017-09-27

    Calving front of the Upsala Glacier (Argentina). This glacier has been thinning and retreating at a rapid rate during the last decades – from 2006 to 2010, it receded 43.7 yards (40 meters) per year. During summer 2012, large calving events prevented boat access to the glacier. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Etienne Berthier, Université de Toulouse 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

  5. Glaciers and Sea Level Rise

    NASA Image and Video Library

    2017-09-28

    Peripheral glaciers and ice caps (isolated from the main ice sheet, which is seen in the upper right section of the image) in eastern Greenland. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Frank Paul, University of Zurich 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

  6. Glaciers and Sea Level Rise

    NASA Image and Video Library

    2017-09-28

    The Aletsch Glacier in Switzerland is the largest valley glacier in the Alps. Its volume loss since the middle of the 19th century is well-visible from the trimlines to the right of the image. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Frank Paul, University of Zurich 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

  7. Glaciers and Sea Level Rise

    NASA Image and Video Library

    2017-09-27

    An airplane drops essential support on the Austfonna Ice Cap in Svalbard (Norwegian Arctic). The triangular structure is a corner reflector used as ground reference for airborne radar surveys. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Andrea Taurisano, Norwegian Polar Institute 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

  8. Glaciers and Sea Level Rise

    NASA Image and Video Library

    2013-01-01

    Calving front of the Perito Moreno Glacier (Argentina). Contrary to the majority of the glaciers from the southern Patagonian ice field, the Perito Moreno Glacier is currently stable. It is also one of the most visited glaciers in the world. To learn about the contributions of glaciers to sea level rise, visit: http://www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Etienne Berthier, Université de Toulouse 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

  9. Glaciers and Sea Level Rise

    NASA Image and Video Library

    2008-08-25

    Aerial view of the Sverdrup Glacier, a river of ice that flows from the interior of the Devon Island Ice Cap (Canada) into the ocean. To learn about the contributions of glaciers to sea level rise, visit: http://www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Alex Gardner, Clark University 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

  10. Tectonic vs. eustatic controls on Ordovician deposition in the Alabama Appalachians

    SciTech Connect

    Benson, D.J. . Dept. of Geology)

    1992-01-01

    The Lower Ordovician section consists of a thick (> 1,500 ft.) sequence of peritidal to shallow subtidal carbonates deposited on a broad, stable platform. Initial Taconic orogenic activity during Late Canadian time downwarped the southeastern margin of the continent and resulted in deposition of a unique subtidal unit. A fall in eustatic sea level during Early Whiterockian time exposed the majority of the platform and produced the Post-Knox unconformity, a major regional unconformity that truncates Upper Cambrian-Lower Ordovician carbonates across the Alabama Appalachians. Middle Ordovician deposition began as a result of eustatic sea level rise and continued downwarping of the SE margin of the North American continent. Initial Middle Ordovician deposits are peritidal carbonates that onlap the Post-Knox unconformity from SE to NW. Continued loading of the margin of the continent led to formation of a deep-water basin to the SE and the concurrent development of a peripheral bulge in the vicinity of what is now the Birmingham anticlinorium. Peritidal carbonates to the SE pass upward into shallow ramp carbonates, deep-ramp mixed carbonate/clastic deposits, and, finally, basinal organic shales. As the deep-water basin evolved, shallow ramp carbonates onlapped the peripheral bulge to the NW. The rapidly evolving basin trapped terrigeneous deposits shed from tectonic highlands to the E and SE permitting deposition of shallow to deep ramp, skeletal carbonates to the NW. Continued tectonic loading led to migration and the ultimate inundation of the peripheral bulge. By Late Mohawkian time, filling of the basin allowed terrigeneous sediments derived from the tectonic highlands to prograde westward, onlap and carbonate ramp, and, finally, terminate carbonate deposition.

  11. Clathrate eustasy: Methane hydrate melting as a mechanism for geologically rapid sea-level fall

    SciTech Connect

    Bratton, J.F.

    1999-10-01

    Although submarine methane hydrates or clathrates have been highlighted as potential amplifiers of modern global climate change and associated glacio-eustatic sea-level rise, their potential role in sea-level fall has not been appreciated. Recent estimates of the total volume occupied by gas hydrates in marine sediments vary 20-fold, from 1.2 x 10{sup 14} to 2.4 x 10{sup 15} m{sup 3}. Using a specific volume change on melting of {minus}21%, dissociation of the current global inventory of hydrate would result in a decrease of submarine hydrate volume of 2.4 x 10{sup 13} to 5.0 x 10{sup 14} m{sup 3}. Release of free gas bubbles present beneath hydrates would increase these volumes by 1.1 --2.0 x 10{sup 13} m{sup 3}. The combined effects of hydrate melting and subhydrate gas release would result conservatively in a global sea-level fall of 10--146 cm. Such a mechanism may offset some future sea-level rise associated with thermal expansion of the oceans. It could also explain anomalous sea-level drops during ice-free periods such as the early Eocene, the Cretaceous, and the Devonian.

  12. Clathrate eustasy: Methane hydrate melting as a mechanism for geologically rapid sea-level fall

    USGS Publications Warehouse

    Bratton, J.F.

    1999-01-01

    Although submarine methane hydrates or clathrates have been highlighted as potential amplifiers of modern global climate change and associated glacio-eustatic sea-level rise, their potential role in sea-level fall has not been appreciated Recent estimates of the total volume occupied by gas hydrates in marine sediments vary 20-fold, from 1.2 ?? 1014 to 2.4 ?? 1015 m3. Using a specific volume change on melting of-21%, dissociation of the current global inventory of hydrate would result in a decrease of submarine hydrate volume of 2.4 ?? 1013 to 5.0??1014 m3. Release of free gas bubbles present beneath hydrates would increase these volumes by 1.1-2.0 ?? 1013 m3. The combined effects of hydrate melting and subhydrate gas release would result conservatively in a global sea-level fall of 10-146 cm. Such a mechanism may offset some future sea-level rise associated with thermal expansion of the oceans. It could also explain anomalous sea-level drops during ice-free periods such as the early Eocene, the Cretaceous, and the Devonian.

  13. Holocene relative sea level rise and subsidence in northern Gulf of Mexico

    SciTech Connect

    Penland, S.; Sutter, J.R.; Ramsey, K.E.; McBride, R.D.

    1988-01-01

    The analysis of more than 90 tidal gauge records, 10,000-km high resolution seismic profiles, 500 vibracores, and 250 radiocarbon dates led to the development of a new sea level history for the Louisiana coastal zone and adjacent continental shelf for the last 8,000 years. Now reinterpreted, the original single delta plain is seen as actually two individual, imbricated shelf-phase delta plains deposited at different sea levels. Termed the modern and late Holocene, these two delta plains are separated by a regional shoreface refinement surface, which can be traced updip to the relict-transgressive Teche shoreline. The Late Holocene delta plain was deposited during a sea level stillstand 6 m below the present, 3,000-7,2000 years ago. A 5 to 6-m eustatic-enhanced relative rise in sea level, 2,5000-3,000 years ago at a rate of 1-1.2 cm/yr led to the complete transgresive submergence of the lower late Holocene delta plain. Sea level reached its approximate position about 2,500 years ago, and since then the Mississippi River has built the modern delta plain consisting of the abandoned St. Bernard and Lafourche delta complexes and the active Balize and Atchafalaya delta complexes.

  14. 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.

  15. Sea-Level Projections from the SeaRISE Initiative

    NASA Technical Reports Server (NTRS)

    Nowicki, Sophie; Bindschadler, Robert

    2011-01-01

    SeaRISE (Sea-level Response to Ice Sheet Evolution) is a community organized modeling effort, whose goal is to inform the fifth IPCC of the potential sea-level contribution from the Greenland and Antarctic ice sheets in the 21st and 22nd century. SeaRISE seeks to determine the most likely ice sheet response to imposed climatic forcing by initializing an ensemble of models with common datasets and applying the same forcing to each model. Sensitivity experiments were designed to quantify the sea-level rise associated with a change in: 1) surface mass balance, 2) basal lubrication, and 3) ocean induced basal melt. The range of responses, resulting from the multi-model approach, is interpreted as a proxy of uncertainty in our sea-level projections. http://websrv.cs .umt.edu/isis/index.php/SeaRISE_Assessment.

  16. Cycle stacking and long-term sea-level history in the Lower Cretaceous (Gavrovo Platform, NW Greece)

    SciTech Connect

    Groetsch, J.

    1996-07-01

    The stacking pattern of peritidal shallowing-upward cycles of a continuously exposed Barremian to upper Albian section from an isolated carbonate platform in the Gavrovo-Tripolitza Zone (NW Greece) has been analyzed. The 541 m thick succession is located in an intraplatform setting with an overall mud-dominated facies development. It comprises 252 peritidal cycles, which show a systematic increase in cycle thickness from the Barremian to Albian. Comparison of the cycle stacking pattern of the section, which spans 35 m.y., and several published curves of long-term eustatic sea-level history show striking similarities. Comparison of cycle stacking pattern in Greece with a time-equivalent section measured near Potrero Garcia in Mexico suggests preservation of similar trends in Fischer plots in the two areas even though a difference in mean cycle thickness indicates different rates of subsidence in Greece and Mexico. This implies that the shallow-water carbonates of the Gavrovo platform are recording second-order eustatic sea-level variations. Closely spaced samples throughout the section allow evaluation of the degree of early diagenetic alteration of depositional facies within the shallowing-upward cycles. The degree of vadose diagenetic overprinting of intertidal and subtidal facies and multiple overprinting of individual cycles support a predominantly allocyclic control of deposition by low-amplitude, high-frequency sea-level fluctuations during Early Cretaceous greenhouse climate.

  17. North Sea coast levelling net: A model case for the determination of vertical movements in Western Europe

    NASA Astrophysics Data System (ADS)

    Augath, W.; Pelzer, H.

    In Northern Germany, permanent tide gauge records have been available for investigations since about 1850. As a result of such investigations it was found that in the North Sea the mean sea level (MSL) seems to increase by an amount of approximately 2 mm/year being nearly twice the amount of the eustatic change of the MSL recorded all over the world. This result suggested a coastal subsidence of about 1 mm/year. In order to study this effect in more detail a special precise leveling net (North Sea Coast Leveling Net, NKN) was established after 1910 and observed repeatedly. A tendency toward land subsidence was discovered, the amounts determined lying within their statistical confidence regions. The Hanover analysis was established for the computation of vertical crustal movements. The computation and results are detailed.

  18. Freeboard, sea level and dynamic topography during aggregation of a supercontinent

    NASA Astrophysics Data System (ADS)

    Guillaume, B.; Husson, L.; Choblet, G.

    2012-04-01

    The long-term evolution of sea level is a combination of eustatic mechanisms (tectono-eustatism, distribution of continental masses through orogenesis and sedimentation) and non-uniform processes (dynamic topography, geoid, wander of the Earth rotation pole). Given the potentially similar amplitude of both factors, there is a bias in the observation of absolute sea level. Moreover, over large time-scales, and more specifically over the Wilson cycle time-scale, plate aggregation and separation are associated both with (i) variations of the flow pattern and (ii) thermal state in the mantle, which in turn may induce specific vertical motions of the surface. By changing the size of the oceanic and continental water reservoirs, large-scale dynamic topography associated with subduction or the presence of mantle plumes controls rises or drops of sea level, which in turn controls part of the stratigraphic record. The Earth has known periods of continental aggregation and fragmentation that redistribute the location of plate boundaries, especially the location and the length of subduction zones, that could potentially affect sea level. The distribution of mass anomalies in the mantle with respect to continents may therefore have a significant impact. To test the possible correlation between sea level changes and the Wilson cycle, we decide to first focus on the Pangea, which is known to be a period during which most subductions took place beneath continents. We run a set of Earth-like instantaneous flow model using the OEDIPUS (Origin, Evolution and Dynamics of the Interiors of Planets Using Simulation) tool, which allows spherical geometries with lateral viscosity variations. In these models, Pangea is modeled by a spherical continental cap, covering 29% of the planet surface, and floating above a two-layered viscous mantle. We vary parameters such as the dip of the subducting panel, the depth reached by the slab, the viscosity structure and the plate thickness within

  19. Diagenesis and porosity development associated with major sea level fluctuations, Upper Permian, Jameson land, east Greenland

    SciTech Connect

    Scholle, P.A.; Ulmer, D.S. ); Stemmerik, L. )

    1990-05-01

    The Upper Permian of Jameson Land includes two major carbonate sequences, represented by the Karstryggen and Wegener Halvoe formations. The initial Karstryggen transgression led to the development of a shallow marine platform with structurally controlled evaporite basins (salinas) separated by stromatolitic, peloidal, or micritic carbonate depositional areas. The Wegener Havloe sequence reflects more rapid and extensive transgression with the deposition of three subcycles of fully marine, platform, or biohermal carbonates containing minor evaporites near the basin margins. Bioherms (bryozoan-brachiopod-marine cement mounds) show > 100 m of relief, indicating that large relative sea level changes were involved. Both the Karstryggen and Wgener Havloe cycles were terminated by major regressions, which led to karstic and/or fluvial incision of the underlying sequences. Not surprisingly, carbonate and evaporite diagenesis was greatly affected by these regional or eustatic sea level fluctuations. Evaporites dissolved or were replaced by calcite and celestite under the influence of meteoric waters. Limestones show collapse brecciation, grain leaching, soil development, and characteristic vadose and phreatic cements. Most significantly meteoric flushing led to massive dissolution of botryoidal marine cements (aragonite and probable high-Mg calcite) within biohermal facies on the Wegener Peninsula. This early porosity resurrection led to the preservation of porous bioherm core zones until hydrocarbon migration. Only late (posthydrocarbon), probably hydrothermal fluid flow led to cementation of the bioherm cores while expelling most of the reservoired hydrocarbons. If the sea level changes affecting the Greenlandic Permian are eustatic, then this study may provide significant clues to porosity development throughout the largely unexplored northern Zechstein basin.

  20. CO2 and sea level

    NASA Astrophysics Data System (ADS)

    Bell, Peter M.

    There is considerable discussion currently about the potential effects of carbon dioxide build-up in the atmosphere over the next several decades. The sources of information are two Government funded reports, one by the National Research Council (NRC), the other by the Environment Protection Agency (EPA), both were released within the last five months. The reports were described recently as being conservative, although the consequences of the resulting greenhouse effects are deemed inevitable. Atmospheric warming on a global scale of as much as 5°C cannot be avoided, only perhaps delayed by a few years at best (Environ. Sci. Technol, 18, 45A-46A, 1984). The cause is the burning of fossil fuels. Oil will not be too important because its supplies are predictably exhausted on the time scale of 50-100 years. Coal burning is considered as the main source of carbon dioxide. Among the more spectacular results of a global temperature rise over the next 100 years is the expected rise in sea level of a minimum of 70 cm (Oceanus, Winter, 1983/84). If the West Antarctic Ice Sheet breaks up and melts, the rise could be in the several meter range. Sea level rose only 15 cm in the past century.

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

    USGS Publications Warehouse

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

    2009-01-01

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

  2. Global change and relative sea level rise at Venice: what impact in term of flooding

    NASA Astrophysics Data System (ADS)

    Carbognin, Laura; Teatini, Pietro; Tomasin, Alberto; Tosi, Luigi

    2010-11-01

    Relative sea level rise (RSLR) due to climate change and geodynamics represents the main threat for the survival of Venice, emerging today only 90 cm above the Northern Adriatic mean sea level (msl). The 25 cm RSLR occurred over the 20th century, consisting of about 12 cm of land subsidence and 13 cm of sea level rise, has increased the flood frequency by more than seven times with severe damages to the urban heritage. Reasonable forecasts of the RSLR expected to the century end must be investigated to assess the suitability of the Mo.S.E. project planned for the city safeguarding, i.e., the closure of the lagoon inlets by mobile barriers. Here we consider three RSLR scenarios as resulting from the past sea level rise recorded in the Northern Adriatic Sea, the IPCC mid-range A1B scenario, and the expected land subsidence. Available sea level measurements show that more than 5 decades are required to compute a meaningful eustatic trend, due to pseudo-cyclic 7-8 year long fluctuations. The period from 1890 to 2007 is characterized by an average rate of 0.12 ± 0.01 cm/year. We demonstrate that linear regression is the most suitable model to represent the eustatic process over these 117 year. Concerning subsidence, at present Venice is sinking due to natural causes at 0.05 cm/year. The RSLR is expected to range between 17 and 53 cm by 2100, and its repercussions in terms of flooding frequency are associated here to each scenario. In particular, the frequency of tides higher than 110 cm, i.e., the value above which the gates would close the lagoon to the sea, will increase from the nowadays 4 times per year to a range between 20 and 250. These projections provide a large spread of possible conditions concerning the survival of Venice, from a moderate nuisance to an intolerable aggression. Hence, complementary solutions to Mo.S.E. may well be investigated.

  3. 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.

  4. Sea-level control of limestone composition: New data from quaternary carbonates in the Bahamas

    SciTech Connect

    Kindler, P. . Geology Dept.); Hearty, P.J. )

    1993-03-01

    Comprehensive petrographic analysis of limestone in the Bahamas reveals that their composition was ultimately controlled by climatic and sea-level changes during the Quaternary. These results demonstrate that facies analysis of limestone is not only useful for local and regional correlations, but also represents a powerful tool for unraveling the sea-level history of carbonate platforms. Ongoing stratigraphic research across the Bahamas leads to the recognition of nine platform-wide depositional units showing distinctive geomorphic, sedimentologic, petrologic and geochemical features. These units were deposited during major transgressive episodes from the middle Pleistocene to the late Holocene. They are bounded by glacial-age reddish paleosols. Petrographic variations between units do not occur randomly and are not uniquely determined by morphological controls (e.g. bank margin orientation). They are more likely related to climatic and eustatic changes. Oolitic/peloidal units were deposited during warm intervals when the Bahamian platform was totally submerged. Formation of skeletal units reflects cooler periods and partial flooding of the platform when carbonate production was limited to bank-fringing reefs. In conclusion, the limestone units exposed in the Bahamas are sensitive indicators of past sea-level fluctuations. Their composition is controlled by the degree of platform flooding and the rate of sea-level rise, while microfacies analysis has proven useful for paleoclimatic reconstruction.

  5. Regionally differentiated contribution of mountain glaciers and ice caps to future sea-level rise

    NASA Astrophysics Data System (ADS)

    Radić, Valentina; Hock, Regine

    2011-02-01

    The contribution to sea-level rise from mountain glaciers and ice caps has grown over the past decades. They are expected to remain an important component of eustatic sea-level rise for at least another century, despite indications of accelerated wastage of the ice sheets. However, it is difficult to project the future contribution of these small-scale glaciers to sea-level rise on a global scale. Here, we project their volume changes due to melt in response to transient, spatially differentiated twenty-first century projections of temperature and precipitation from ten global climate models. We conduct the simulations directly on the more than 120,000 glaciers now available in the World Glacier Inventory, and upscale the changes to 19 regions that contain all mountain glaciers and ice caps in the world (excluding the Greenland and Antarctic ice sheets). According to our multi-model mean, sea-level rise from glacier wastage by 2100 will amount to 0.124+/-0.037m, with the largest contribution from glaciers in Arctic Canada, Alaska and Antarctica. Total glacier volume will be reduced by 21+/-6%, but some regions are projected to lose up to 75% of their present ice volume. Ice losses on such a scale may have substantial impacts on regional hydrology and water availability.

  6. Climate-induced variations in lake levels: A mechanism for short-term sea level change during non-glacial times

    SciTech Connect

    Jacobs, D. ); Sahagian, D. . Dept of Geological Sciences)

    1992-01-01

    Variations in insolation due to periodic orbital parameters can cause climatic changes and associated variations in the intensity of monsoonal circulation. This can lead to significant variations in the levels of internally draining lakes on timescales of 10,000 to 100,000 years in regions affected by the monsoon (20,000 years for orbital precession). These variations may be responsible for small scale (few meters) eustatic sea level changes in an ice-free Earth, and may contribute to sea level changes in the presence of ice as well. The authors have estimated the volume of empty present lake basins in the regions of Asia and North Africa influenced by the monsoon. The surface water volume alone of these basins is equivalent to a two meter difference in sea level, but is considerably augmented by groundwater associated with an increase in lake level. The lake variation mechanism for sea level change has its basis in the Quaternary record of climate change and associated explanatory models. However, the argument also applies to earlier, non-glacial periods of geologic time. Clear evidence for the presence of ice in the Triassic is lacking. However, there is evidence for short-term periodic fluctuations of lake levels as well as sea level during that time. These sea level changes, as well as those in the Devonian, Jurassic, and Cretaceous, may be driven by periodic fluctuation in lacustrine and groundwater storage resulting from orbitally forced changes in monsoon intensity, even in the absence of significant glacial ice.

  7. Responses of a deltaic system to minor relative sea level variations (Middle Jurassic, Cleveland basin, England): Consequences on the reservoir geometry

    SciTech Connect

    Eschard, R.; Ravenne, C. )

    1990-05-01

    In the Middle Jurassic series of the Cleveland basin (England), an accurate three-dimensional reconstruction of depositional sequences from outcrops, cores, and wireline logs show that minor sea level variations control the evolution of a deltaic system. Because of low subsidence and sediment supply rates, rapid sea level rises induce several landward shifts of the shoreline, whereas minor sea level drops produce the incision of small paleovalleys. The deltaic series, 200 m thick at the basin depocenter, are subdivided into five depositional sequences. During the first two sequences, the sediment supply rate exceeds the relative sea level rate and the delta progrades. The delta aggrades during the third depositional sequence and retrogrades in the fourth depositional sequence when the relative sea level rise rate balances then exceeds the sediment supply rate. Finally, a relative sea level drop induces the incision of a paleovalley progressively infilled during the following sea level rise. Several orders of bathymetric cycles are deduced from detailed correlations of the unconformities and from the comparison of the vertical facies succession between low and high subsiding areas. The general evolution of the delta is related to a 5-m.y. bathymetric cycle due to a eustatic sea level rise and fall. Pne to 3-m.y. bathymetric cycles control the main aggradation patterns of the delta. These patterns are related to third-order eustatic cycles or to local tectonic events. Less than 0.5 m.y. bathymetric cycles are registrated by parasequences or minor depositional sequences which are correlated all over the basin. The controlling parameters of the sequences are discussed. Minor bathymetric cycles (0.2 m.y.) reflect small-scale sea level oscillations or autocyclic evolution of the sedimentary bodies. The authors focus on the reservoir geometry within each bathymetric cycle.

  8. Analysis of sea level and sea surface temperature changes in the Black Sea

    NASA Astrophysics Data System (ADS)

    Betul Avsar, Nevin; Jin, Shuanggen; Kutoglu, Hakan; Erol, Bihter

    2016-07-01

    The Black Sea is a nearly closed sea with limited interaction with the Mediterranean Sea through the Turkish Straits. Measurement of sea level change will provide constraints on the water mass balance and thermal expansion of seawaters in response to climate change. In this paper, sea level changes in the Black Sea are investigated between January 1993 and December 2014 using multi-mission satellite altimetry data and sea surface temperature (SST) data. Here, the daily Maps of Sea Level Anomaly (MSLA) gridded with a 1/8°x1/8° spatial resolution from AVISO and the NOAA 1/4° daily Optimum Interpolation Sea Surface Temperature (OISST) Anomaly data set are used. The annual cycles of sea level and sea surface temperature changes reach the maximum values in November and January, respectively. The trend is 3.16±0.77 mm/yr for sea level change and -0.06±0.01°C/yr for sea surface temperature during the same 22-year period. The observed sea level rise is highly correlated with sea surface warming for the same time periods. In addition, the geographical distribution of the rates of the Black Sea level and SST changes between January 1993 and December 2014 are further analyzed, showing a good agreement in the eastern Black Sea. The rates of sea level rise and sea surface warming are larger in the eastern part than in the western part except in the northwestern Black Sea. Finally, the temporal correlation between sea level and SST time series are presented based on the Empirical Orthogonal Function (EOF) analysis.

  9. Sea level regulated tetrapod diversity dynamics through the Jurassic/Cretaceous interval

    PubMed Central

    Tennant, Jonathan P.; Mannion, Philip D.; Upchurch, Paul

    2016-01-01

    Reconstructing deep time trends in biodiversity remains a central goal for palaeobiologists, but our understanding of the magnitude and tempo of extinctions and radiations is confounded by uneven sampling of the fossil record. In particular, the Jurassic/Cretaceous (J/K) boundary, 145 million years ago, remains poorly understood, despite an apparent minor extinction and the radiation of numerous important clades. Here we apply a rigorous subsampling approach to a comprehensive tetrapod fossil occurrence data set to assess the group's macroevolutionary dynamics through the J/K transition. Although much of the signal is exclusively European, almost every higher tetrapod group was affected by a substantial decline across the boundary, culminating in the extinction of several important clades and the ecological release and radiation of numerous modern tetrapod groups. Variation in eustatic sea level was the primary driver of these patterns, controlling biodiversity through availability of shallow marine environments and via allopatric speciation on land. PMID:27587285

  10. Sea level regulated tetrapod diversity dynamics through the Jurassic/Cretaceous interval

    NASA Astrophysics Data System (ADS)

    Tennant, Jonathan P.; Mannion, Philip D.; Upchurch, Paul

    2016-09-01

    Reconstructing deep time trends in biodiversity remains a central goal for palaeobiologists, but our understanding of the magnitude and tempo of extinctions and radiations is confounded by uneven sampling of the fossil record. In particular, the Jurassic/Cretaceous (J/K) boundary, 145 million years ago, remains poorly understood, despite an apparent minor extinction and the radiation of numerous important clades. Here we apply a rigorous subsampling approach to a comprehensive tetrapod fossil occurrence data set to assess the group's macroevolutionary dynamics through the J/K transition. Although much of the signal is exclusively European, almost every higher tetrapod group was affected by a substantial decline across the boundary, culminating in the extinction of several important clades and the ecological release and radiation of numerous modern tetrapod groups. Variation in eustatic sea level was the primary driver of these patterns, controlling biodiversity through availability of shallow marine environments and via allopatric speciation on land.

  11. 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.

  12. Rapid rise in effective sea-level in southwest Bangladesh: Its causes and contemporary rates

    NASA Astrophysics Data System (ADS)

    Pethick, John; Orford, Julian D.

    2013-12-01

    Evidence is presented from three estuarine tide gauges located in the Sundarban area of southwest Bangladesh of relative sea level rise substantially in excess of the generally accepted rates from altimetry, as well as previous tide-gauge analyses. It is proposed that the difference arises from the use of Relative Mean Sea Level (RMSL) to characterise the present and future coastal flood hazard, since RMSL can be misleading in estuaries in which tidal range is changing. Three tide gauges, one located in the uninhabited mangrove forested area (Sundarban) of southwest Bangladesh, the others in the densely populated polder zone north of the present Sundarban, show rates of increase in RMSL ranging from 2.8 mm a- 1 to 8.8 mm a- 1. However, these trends in RMSL disguise the fact that high water levels in the polder zone have been increasing at an average rate of 15.9 mm a- 1 and a maximum of 17.2 mm a- 1. In an area experiencing tidal range amplification, RMSL will always underestimate the rise in high water levels; consequently, as an alternative to RMSL, the use of trends in high water maxima or ‘Effective Sea Level Rise’ (ESLR) is adopted as a more strategic parameter to characterise the flooding hazard potential. The rate of increase in ESLR is shown to be due to a combination of deltaic subsidence, including sediment compaction, and eustatic sea level rise, but principally as a result of increased tidal range in estuary channels recently constricted by embankments. These increases in ESLR have been partially offset by decreases in fresh water discharge in those estuaries connected to the Ganges. The recognition of increases of the effective sea level in the Bangladesh Sundarban, which are substantially greater than increases in mean sea level, is of the utmost importance to flood management in this low-lying and densely populated area.

  13. Delta growth and river valleys: the influence of climate and sea level changes on the South Adriatic shelf (Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Maselli, V.; Trincardi, F.; Asioli, A.; Ceregato, A.; Rizzetto, F.; Taviani, M.

    2014-09-01

    Incised valleys across continental margins represent the response of fluvial systems to changes in their equilibrium dynamics, mainly driven by base level fall forced by glacial-eustatic cycles. The Manfredonia Incised Valley formed during the last glacial sea level lowstand, when most of the southern Adriatic shelf was sub-aerially exposed but the outer shelf remained under water. The pronounced upstream deepening of the valley is ascribed to river incision of the MIS5e highstand coastal prism and related subaqueous clinoform under the influence of MIS5-4 sea level fluctuations, while the downstream shallowing and narrowing mainly reflects the impact of increased rates of sea level fall at the MIS3-2 transition on a flatter mid-outer shelf. Until 15 ka BP, the valley fed an asymmetric delta confined to the mid-outer shelf, testifying that continental and deep marine systems remained disconnected during the lowstand. Sea level rise reached the inner shelf during the Early Holocene, drowning the valley and leading to the formation of a sheltered embayment confined toward the land: at this time part of the incision remained underfilled with a marked bathymetric expression. This mini-basin was rapidly filled by sandy bayhead deltas, prograding from both the northern and southern sides of the valley. In this environment, protected by marine reworking and where sediment dispersal was less effective, the accommodation space was reduced and autogenic processes forced the formation of multiple and coalescing delta lobes. Bayhead delta progradations occurred in few centuries, between 8 and 7.2 ka cal BP, confirming the recent hypothesis that in this area the valley was filled during the formation of sapropel S1. This proximal valley fill, representing the very shallow-water equivalent of the cm-thick sapropel layers accumulated offshore in the deeper southern Adriatic basin, is of key importance in following the signature of the sapropel in a facies-tract ideally from the

  14. Stratigraphic signature of sub-orbital climate and sea-level changes in the Gulf of Lions (NW Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Berne, S. P.; Bassetti, M. A.; Baumann, J.; Dennielou, B.; Jouet, G.; Mauffrey, M.; Sierro, F. J.

    2014-12-01

    The Promess boreholes in the Gulf of Lions (NW Mediterranean) provide precise chrono-stratigraphic constraints of the last ca 500 ky, that were nicely preserved at the shelf edge due to high accommodation and important sediment supply from the Rhone River. The major stratigraphic elements in this physiographic domain are Falling Stage Systems Tracts (in the sense of SEPM) linked to 100-ky eustatic cycles. They form wedges pinching out on the middle shelf, and thickening seaward on the outer shelf/upper slope (about 30-40m thick on the outer shelf). Within the uppermost sequence, linked to the last Glacial-Interglacial cycle, internal discontinuities were long described, but they were assigned to autogenic processes such as lobe avulsion or bedform migration. However, careful interpretation of a dense grid of very high resolution seismic data, together with precise chronostratigraphic constraints from borehole data and long piston cores, reveal that distinct parasequences, correlable at the regional scale, correspond to relatively minor sea-level changes linked (a) to Bond Cycles during the end of the Last Glacial, and (b) to an early Melt Water Pulse at the onset of Deglacial sea-level rise. These regressive and transgressive (respectively) parasequences are particularly well preserved in canyon heads, due to better accommodation. We propose that such features are important building blocks of the stratigraphic record, that might be recognized elsewhere on modern continental margins, as well as in the rock record.

  15. Long Term Sea Level Change in the Black Sea

    NASA Astrophysics Data System (ADS)

    Cokacar, Tulay; Emin, Özsoy

    2016-04-01

    Since 1992, altimeter missions have dramatically improved our knowledge and understanding of the oceans.This study investigates the long term sea level change during 1992-2015 in the Black Sea. The satellite altimeter data of the Topex-Poseidon, ERS-1 ands ERS-2 missions and sea level variations of 25 tide gauge stations and temperature/salinity data of 25 Argo float observed in the Black Sea are used for the analysis. The altimeter data are assessed and compared with the data from tide gauges and Argo floats in the Black Sea. First ARGO T/S profiles are used to assess the discrepancies observed between the altimeters. Then in situ measurements are compared with multiple altimeter data to detect in situ measurement anomalies and the corrections applied to improve the consistency of the data sets.

  16. Patch-reef morphology as a proxy for Holocene sea-level variability, Northern Florida Keys, USA

    USGS Publications Warehouse

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

    2008-01-01

    A portion of the northern Florida Keys reef tract was mapped with the NASA Experimental Advanced Airborne Research Lidar (EAARL) and the morphology of patch reefs was related to variations in Holocene sea level. Following creation of a lidar digital elevation model (DEM), geospatial analyses delineated morphologic attributes of 1,034 patch reefs (reef depth, basal area, height, volume, and topographic complexity). Morphometric analysis revealed two morphologically different populations of patch reefs associated with two distinct depth intervals above and below a water depth of 7.7 m. Compared to shallow reefs, the deep reefs were smaller in area and volume and showed no trend in topographic complexity relative to water depth. Shallow reefs were more variable in area and volume and became flatter and less topographically complex with decreasing water depth. The knoll-like morphology of deep reefs was interpreted as consistent with steady and relatively rapidly rising early Holocene sea level that restricted the lateral growth of reefs. The morphology of shallow 'pancake-shaped' reefs at the highest platform elevations was interpreted as consistent with fluctuating sea level during the late Holocene. Although the ultimate cause for the morphometric depth trends remains open to interpretation, these interpretations are compatible with a recent eustatic sea-level curve that hindcasts fluctuating late Holocene sea level. Thus it is suggested that the morphologic differences represent two stages of reef accretion that occurred during different sea-level conditions. ?? 2008 Springer-Verlag.

  17. Caribbean mangroves adjust to rising sea level through biotic controls on change in soil elevation

    USGS Publications Warehouse

    McKee, K.L.; Cahoon, D.R.; Feller, Ilka C.

    2007-01-01

    Aim The long-term stability of coastal ecosystems such as mangroves and salt marshes depends upon the maintenance of soil elevations within the intertidal habitat as sea level changes. We examined the rates and processes of peat formation by mangroves of the Caribbean Region to better understand biological controls on habitat stability. Location Mangrove-dominated islands on the Caribbean coasts of Belize, Honduras and Panama were selected as study sites. Methods Biological processes controlling mangrove peat formation were manipulated (in Belize) by the addition of nutrients (nitrogen or phosphorus) to Rhizophora mangle (red mangrove), and the effects on the dynamics of soil elevation were determined over a 3-year period using rod surface elevation tables (RSET) and marker horizons. Peat composition and geological accretion rates were determined at all sites using radiocarbon-dated cores. Results The addition of nutrients to mangroves caused significant changes in rates of mangrove root accumulation, which influenced both the rate and direction of change in elevation. Areas with low root input lost elevation and those with high rates gained elevation. These findings were consistent with peat analyses at multiple Caribbean sites showing that deposits (up to 10 m in depth) were composed primarily of mangrove root matter. Comparison of radiocarbon-dated cores at the study sites with a sea-level curve for the western Atlantic indicated a tight coupling between peat building in Caribbean mangroves and sea-level rise over the Holocene. Main conclusions Mangroves common to the Caribbean region have adjusted to changing sea level mainly through subsurface accumulation of refractory mangrove roots. Without root and other organic inputs, submergence of these tidal forests is inevitable due to peat decomposition, physical compaction and eustatic sea-level rise. These findings have relevance for predicting the effects of sea-level rise and biophysical processes on tropical

  18. Quaternary Sea-Level History from the US Atlantic Coastal Plain

    NASA Astrophysics Data System (ADS)

    Poirier, R. K.; Cronin, T. M.; Katz, M. E.; Browning, J. V.; Miller, K. G.; Willard, D. A.

    2014-12-01

    Analyses of emerged Quaternary paleo-shorelines and marine deposits aid in the reconstruction of environmental conditions and variability surrounding recent ice volume and sea-level histories derived from oxygen isotope records. We present preliminary results from a project designed to analyze the age, elevation, and paleoclimate history of Quaternary sediments deposited during sea level highstands along the United States Atlantic Coastal Plain (ACP) from Maryland to Florida. Prior studies have shown that, depending on the region, ACP sediments correlate with past interglacial periods corresponding to Marine Isotope Stages (MIS) 5, 7, possibly 9, and 11. Stratigraphy, marine micropaleontology, and palynology indicate at least two major marine transgressive sequences on the Delmarva Peninsula in Virginia corresponding to MIS 5a and 11, the Nassawadox Formation and Accomack beds of the Omar Formation, respectively. These depositional sequences represent sea-level positions of approximately +10m and +15m, relative to today. Despite generally corresponding to glacio-eustatic sea levels of +5-9m for MIS 5a-e (Potter & Lambeck, 2003; Kopp et al., 2009), and of +6-13m for MIS 11 (Raymo & Mitrovica, 2012), the relative sea-level positions during both interglacial periods were likely affected by glacio-isostatic adjustment in the region. Corresponding marine units and paleo-shorelines, identified by pronounced inland scarps separated by intermittent terraces on the western side of the Chesapeake Bay, are likely from MIS 5, 7, and 11. Ostracode and foraminifera assemblages identify significant environmental variability within these transgressive interglacial deposits, likely driven by relatively minor, suborbital climatic and sea-level oscillations.

  19. Sequence stratigraphy and a revised sea-level curve for the Middle Devonian of eastern North America

    USGS Publications Warehouse

    Brett, Carlton E.; Baird, G.C.; Bartholomew, A.J.; DeSantis, M.K.; Ver Straeten, C.A.

    2011-01-01

    The well-exposed Middle Devonian rocks of the Appalachian foreland basin (Onondaga Formation; Hamilton Group, Tully Formation, and the Genesee Group of New York State) preserve one of the most detailed records of high-order sea-level oscillation cycles for this time period in the world. Detailed examination of coeval units in distal areas of the Appalachian Basin, as well as portions of the Michigan and Illinois basins, has revealed that the pattern of high-order sea-level oscillations documented in the New York-Pennsylvania section can be positively identified in all areas of eastern North America where coeval units are preserved. The persistence of the pattern of high-order sea-level cycles across such a wide geographic area suggests that these cycles are allocyclic in nature with primary control on deposition being eustatic sea-level oscillation, as opposed to autocylic controls, such as sediment supply, which would be more local in their manifestation. There is strong evidence from studies of cyclicity and spectral analysis that these cycles are also related to Milankovitch orbital variations, with the short and long-term eccentricity cycles (100. kyr and 405. kyr) being the dominant oscillations in many settings. Relative sea-level oscillations of tens of meters are likely and raise considerable issues about the driving mechanism, given that the Middle Devonian appears to record a greenhouse phase of Phanerozoic history. These new correlations lend strong support to a revised high-resolution sea-level oscillation curve for the Middle Devonian for the eastern portion of North America. Recognized third-order sequences are: Eif-1 lower Onondaga Formation, Eif-2: upper Onondaga and Union Springs formations; Eif-Giv: Oatka Creek Formation; Giv-1: Skaneateles, Giv-2: Ludlowville, Giv-3: lower Moscow, Giv-4: upper Moscow-lower Tully, and Giv-5: middle Tully-Geneseo formations. Thus, in contrast with the widely cited eustatic curve of Johnson et al. (1985), which

  20. Eustatic and tectonic control on localization of porosity and permeability, Mid-Permian, Bighorn Basin, Wyoming

    SciTech Connect

    Simmons, S.P.; Scholle, P.A. )

    1990-05-01

    The Goose Egg Formation of the northeastern Bighorn basin was deposited in an arid shoreline (sabkha) environment during a time of global cyclic sea level variations and local tectonic uplift Eustatic sea level lows are represented by terrestrial red beds (seals), whereas highs resulted in the deposition of supratidal to shallow subtidal carbonates (reservoirs). Pennsylvanian and Permian differential uplift along the present basin margin localized a broken chain of barrier islands and shoals during deposition of the Ervay and earlier carbonate members, as recognized in outcrop at Sheep and Little Sheep Mountain anticlines. The Ervay Member on these paleohighs is typified by fenestral dolomite, containing abundant tepees and pisoids. This fabric is interpreted to have folded in the highest intertidal to supratidal sabkha environment which developed on the leeward shores of these islands. The fenestral carbonates grade basinward (westward) into narrow bioclastic grainstone beach deposits and then to open-shelf fossiliferous packstones and wackestone. To the east lie laminated lagoonal micritic limestones and dolomites. Outcrop and core study has shown the fenestral facies to be limited to areas coincident with present-day basin margin anticlines. Not only are these the locations of the most porous facies, but tight Laramide folding of the Goose Egg carbonates resulted in pervasive fracturing and thus very high permeabilities in the same structures. The close association of Laramide folds and productive Permian carbonate horizons in the northeast Bighorn basin could well be characteristic for other yet to be explored structures along the basin-margin trend.

  1. Eustatic and structural control of submarine-fan sedimentation, Conception fan, Santa Barbara basin, California

    SciTech Connect

    Thor, D.R.

    1984-04-01

    Eustatic sea level lows provide an opportunity for submarine-fan development; topography and structure, however, can control depositional-sequence geometry. Analysis of high-resolution seismic data provides a basis to evaluate to the evolution and geometry of the Pleistocene-Holocene Conception fan. The fan formed in the restricted, tectonically active Santo Barbara basin. It consists of 4 vertically stacked depositional sequences, each bounded by nondepositional unconformities. The unconformities are defined by seismic-sequence boundaries and were formed during sea-level falls that are related to Pleistocene glacioeustatic changes. Each depositional sequence consists of lowstand, sandrich facies (fan channel, levee, and lobe) topped by highstand, mud-rich facies. The geometry of the depositional sequences tends to be rectilinear, not arcuate, because lateral progradation is restricted by topographically high structures. The modern fan surface and the Holocene depositional sequence provide a good analog for the older, underlying depositional sequences. The fan surface is characterized by 4 main channels, 2 of which head into submarine canyons incised into the shelf. Submarine canyons that fed the other 2 channels are now filled and have no topographic expression. In addition, numerous partially buried channel segments occur in the interchannel areas. The Holocene depositional sequence consists of lenticular and sheet-drape deposits interpreted to be channel, levee, and lobe facies. The facies geometry suggests that Mutti's topographic compensation, channel migration, and avulsion were typical processes on Conception fan.

  2. Causes for contemporary regional sea level changes.

    PubMed

    Stammer, Detlef; Cazenave, Anny; Ponte, Rui M; Tamisiea, Mark E

    2013-01-01

    Regional sea level changes can deviate substantially from those of the global mean, can vary on a broad range of timescales, and in some regions can even lead to a reversal of long-term global mean sea level trends. The underlying causes are associated with dynamic variations in the ocean circulation as part of climate modes of variability and with an isostatic adjustment of Earth's crust to past and ongoing changes in polar ice masses and continental water storage. Relative to the coastline, sea level is also affected by processes such as earthquakes and anthropogenically induced subsidence. Present-day regional sea level changes appear to be caused primarily by natural climate variability. However, the imprint of anthropogenic effects on regional sea level-whether due to changes in the atmospheric forcing or to mass variations in the system-will grow with time as climate change progresses, and toward the end of the twenty-first century, regional sea level patterns will be a superposition of climate variability modes and natural and anthropogenically induced static sea level patterns. Attribution and predictions of ongoing and future sea level changes require an expanded and sustained climate observing system.

  3. Late Holocene Sea-Level Changes in French Polynesia, South-Central Pacific

    NASA Astrophysics Data System (ADS)

    Camoin, G.; Hallmann, N.; Eisenhauer, A.; Samankassou, E.; Milne, G. A.

    2013-12-01

    Camoin, G.1, Hallmann, N.1, Eisenhauer, A.2, Vella, C.1, Samankassou, E.3, Fietzke, J.2, Milne, G.A.4 1 Aix-Marseille Université, CNRS, IRD, CEREGE UM34, Europôle Méditerranéen de l'Arbois, BP80, 13545 Aix-en-Provence cedex 4, France 2 Helmholtz-Zentrum für Ozeanforschung GEOMAR, Kiel, Wischhofstrasse 1-3, 24148 Kiel, Germany 3 University of Geneva, Rue des Maraîchers 13, CH-1205 Geneva, Switzerland 4 University of Ottawa, Department of Earth Sciences, Ottawa, Ontario, K1N 6N5, Canada Knowledge of the timing and course of sea-level changes provides an essential framework for conceptual models aimed at understanding the dynamics of melting of large ice sheets and their effects on the isostasy of the Earth. The marked variability of local Holocene sea levels, responding both to ice-sheet unloading and the redistribution of water masses in the global ocean, demonstrates the need to constrain geophysical processes that include hydro-isostasy, equatorial ocean syphoning and tectonic movements affecting relative sea-level positions. A regional reconstruction of Late Holocene sea-level changes (i.e., the last 6,000 yrs) in French Polynesia is based on the accurate U-series dating of in situ sea-level indicators (coral colonies including microatolls; bivalves) and their precise vertical and horizontal GPS positioning in five atolls (Fakarava, Hao, Manihi, Rangiroa, Tikehau) from the Tuamotu Archipelago and six high islands (Bora Bora, Mangareva, Maupiti, Moorea, Raivavae, Rurutu) from the Society, Gambier and Austral Archipelagos. These islands provide the opportunity to reconstruct accurately Late Holocene sea-level changes that are well-suited to estimate eustatic and isostatic changes because : 1) they exhibit unique coral reef records including valuable sea-level indicators, such as corals and bivalves in growth position, emerged coral conglomerates and beachrocks, 2) their subsidence rates are negligible for the Late Holocene period, thus excluding any tectonic

  4. Sea-level changes over the past 6,000 years in the Society and Tuamotu Islands, French Polynesia

    NASA Astrophysics Data System (ADS)

    Hallmann, N.; Camoin, G.; Eisenhauer, A.; Vella, C.; Samankassou, E.; Fietzke, J.; Milne, G. A.

    2013-12-01

    Tropical coral reefs are unique recorders of sea-level and environmental changes. They are therefore of pivotal importance to resolving the rates of millennial-scale eustatic changes, to clarifying the mechanisms that drive glacial-interglacial cycles and to constraining geophysical models. A detailed regional study of Late Holocene (i.e., the past 6,000 years) relative sea-level changes is based on coral reef records of two high islands from the Society Islands (Bora Bora, Moorea) and two atolls from the Tuamotu Archipelago (Rangiroa, Tikehau), French Polynesia, South-Central Pacific. Different sea-level indicators, such as in situ coral colonies, bivalves and exposed coral conglomerates, were used in order to reconstruct relative sea-level changes. A special attention has been given to microatolls which are circular coral colonies that grow predominantly laterally as their upward growth is constrained by the water level, thus providing an accurate record of the low-tide level. The reconstruction of sea-level changes has been based on the accurate dating (U/Th (MC-ICPMS) dating with a 2σ error of 3-36 years) of pristine coral and bivalve samples and the precise measurement of their position (especially altitude) via GPS (vertical and horizontal precision of 1-3 cm and a few millimetres, respectively). Former studies have reported that sea level in French Polynesia was approximately 1 m higher than present between 5,000 and 1,250 yrs BP and that a highstand was reached between 2,000 and 1,500 yrs BP (Pirazzoli and Montaggioni, 1988) and persisted until 1,200 yrs BP in the Tuamotu Archipelago (Pirazzoli and Montaggioni, 1986). In contrast to these former studies, our study reveals that sea level reached its present level at around 5,000 yrs BP and continued to rise from at least 4,951 to 2,535 yrs BP when it was at least 1.3 m above the present level. These results will be integrated in a regional study of Late Holocene sea-level changes in various islands from

  5. Contribution of climate-driven change in continental water storage to recent sea-level rise

    USGS Publications Warehouse

    Milly, P.C.D.; Cazenave, A.; Gennero, M.C.

    2003-01-01

    Using a global model of continental water balance, forced by interannual variations in precipitation and near-surface atmospheric temperature for the period 1981-1998, we estimate the sea-level changes associated with climate-driven changes in storage of water as snowpack, soil water, and ground water; storage in ice sheets and large lakes is not considered. The 1981-1998 trend is estimated to be 0.12 mm/yr, and substantial interannual fluctuations are inferred; for 1993-1998, the trend is 0.25 mm/yr. At the decadal time scale, the terrestrial contribution to eustatic (i.e., induced by mass exchange) sea-level rise is significantly smaller than the estimated steric (i.e., induced by density changes) trend for the same period, but is not negligibly small. In the model the sea-level rise is driven mainly by a downtrend in continental precipitation during the study period, which we believe was generated by natural variability in the climate system.

  6. Sea level variations during snowball Earth formation: 1. A preliminary analysis

    NASA Astrophysics Data System (ADS)

    Liu, Yonggang; Richard Peltier, W.

    2013-08-01

    A preliminary theoretical estimate of the extent to which the ocean surface could have fallen with respect to the continents during the snowball Earth events of the Late Neoproterozoic is made by solving the Sea Level Equation for a spherically symmetric Maxwell Earth. For a 720 Ma (Sturtian) continental configuration, the ice sheet volume in a snowball state is ~750 m sea level equivalent, but ocean surface lowering (relative to the original surface) is ~525 m due to ocean floor rebounding. Because the land is depressed by ice sheets nonuniformly, the continental freeboard (which may be recorded in the sedimentary record) at the edge of the continents varies between 280 and 520 m. For the 570 Ma (Marinoan) continental configuration, ice volumes are ~1013 m in eustatic sea level equivalent in a "soft snowball" event and ~1047 m in a "hard snowball" event. For this more recent of the two major Neoproterozoic glaciations, the inferred freeboard generally ranges from 530 to 890 m with most probable values around 620 m. The thickness of the elastic lithosphere has more influence on the predicted freeboard values than does the viscosity of the mantle, but the influence is still small (~20 m). We therefore find that the expected continental freeboard during a snowball Earth event is broadly consistent with expectations (~500 m) based upon the inferences from Otavi Group sediments.

  7. NOAA Regional Sea Level Trends and Scenarios

    NASA Astrophysics Data System (ADS)

    Sweet, W.; Zervas, C.; Leuliette, E. W.

    2016-12-01

    NOAA has a new website to help coastal communities recognize past changes in regional sea level to better plan for a range of possible rise scenarios this century. The site compares 11 regionalized and coherent tide-gauge and satellite-altimeter sea level series from around the U.S. to estimate multi-decadal changes that have occurred in response to regional sea surface height-related trends and variability. Local relative trends are obtainable even without data from a local tide gauge when combined with estimates of vertical land motion, which can be obtained from several years of record from a GPS-based continuously operating reference system (CORS). The regionalized series will be updated annually and displayed relative to the most recent sea level rise scenarios of the (i.e., 2014) National Climate Assessment to characterize the regional sea level change trajectory for future planning of associated impacts.

  8. Difference of sea level rising rate from steric and altimeter sea level in the regional Yellow and East China Seas

    NASA Astrophysics Data System (ADS)

    Kang, S. K.; Cherniawsky, J. Y.; Foreman, M. G. G.; Kim, E.

    2016-12-01

    Regional sea level rise is examined in the Yellow and East China Seas (YECS) for the Topex/Poseidon and Jason altimetry period. Coastal tidal data, altimetry and steric sea level data are examined and compared from 1993 to 2015. As usual, temperature and salinity data sampled at regular intervals are available for only a limited number of stations around the Korean Peninsula. The regional sea level rising rate from altimetry compares well with the sea level rising rate from coastal sea level data around Korean Peninsula and Japanese islands around the YECS where data are available. However, differences between the sea level rising rate from altimetry and the steric sea level rising rate are rather large, as expected, since mass effects can not be reflected in the steric sea level rising rate. This is significantly different from the results of the sea level rising trend in the deep East/Japan Sea where thermosteric sea level compares well with the altimetry sea level trend during 9 year period from 1992 to 2001 (Kang et al., 2005). This may suggest that the cause of variability in sea level rising may change with the global trend change in sea level rise with increasing melting effect.The difference of steric sea level and altimetry data for the last 23 years (1993-2015) is expected to be mainly due to mass effects or the addition of mass and dynamic effects. The limited number of data from CTD stations may cause inaccuracies in estimating regional steric sea level in the YECS. The steric sea level rising rate computed from Argo data in the northwestern Pacific (D. Roemmich, 2013), upstream of East China Sea, seems to indicate a negative steric sea level rising pattern during 2006-2013. This suggests that water characteristics affecting the East China Seas through the Kuroshio may contribute to a negative sea level rising trend. More discussion will be given during the meeting.This work is partially supported from research funds from KIOST project (PE99392).

  9. Common Era Sea-Level Change

    NASA Astrophysics Data System (ADS)

    Horton, B.; Kemp, A.; Kopp, R. E., III

    2014-12-01

    The Atlantic coast of North America provides a sedimentary record of Common Era sea levels with the resolution to identify the mechanisms that cause spatial variability in sea-level rise. 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, the western North Atlantic Ocean is sensitive to spatial variability in sea-level change, because of static equilibrium effects from melting of the Greenland Ice Sheet, ocean circulation and wind-driven variability in the Gulf Stream and GIA induced land-level change from ongoing collapse of Laurentide forbuldge. We reveal three distinct patters in sea-level during the Common Era along the North American Atlantic coast, likely linked to wind-driven changes in the Gulf Stream: (1) Florida, sea level is essentially flat, with the record dominated by long-term geological processes; (2) North Carolina, sea level falls to a minimum near the beginning of the second millennium, climbing to an early Little Ice Age maximum in the fifteenth century, and then declining through most of the nineteenth century; and (3) New Jersey, a sea-level maximum around 900 CE, a sea-level minimum around 1500 CE, and a long-term sea-level rise through the second half of the second millennium. We combine the salt-marsh data from North American Atlantic coast with tide-gauge records and lower resolution proxies from the northern and southern hemispheres. We apply a noisy-input Gaussian process spatio-temporal modeling framework, which identifies a long-term falling global mean sea-level (GMSL), 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 Common Era.

  10. Sea-level rise impacts on scour at coastal bridges in the southeastern United States

    NASA Astrophysics Data System (ADS)

    Froehlich, D.

    2003-04-01

    Sea level, which has risen by 10 to 20 cm (4 to 8 inches) in the past century along most of the US coastline, is projected to rise an additional 48 cm (19 inches) by 2100, with a possible range of 13 cm to 95 cm (26 to 37 inches). Eustatic increases in sea level are being caused largely by melting glaciers and ice sheets on land, and thermal expansion of ocean water. Sea level rise will continue to accelerate beyond 2100 as a result of the great amount of time needed for oceans and ice sheets to approach equilibrium under the long-term perturbations anticipated with climate change. Tropical storms, hurricanes, typhoons, and similar extreme atmospheric phenomena along the southeastern coast of the US generate high winds that in turn create large waves and currents. Resulting storm surges can temporarily raise water levels by as much as 23 feet (7 meters) above normal. Although these events are sporadic, they are a primary cause of scour at bridges along most of the US coastline. Even if storm magnitudes and frequencies do not change as a result of global warming, an important impact of future storms, whether tropical or extratropical, will be their superposition on a rising sea level. Thus sea-level rise will increase impacts to the coast by a storm of a given magnitude by increasing the baseline water level for extreme storms. Because many coastal bridges were designed to withstand erosion produced by storm surges having 1 percent annual chance of occurrence (that is, 100-year storm surge), as sea levels increase the statistics used to design these structures changes. For example, a 50-year storm surge following an increase in sea level could scour a bridge as severely as would the current 100-year storm surge. Impacts of rising sea levels on scour at coastal bridges in the southeastern US are illustrated by an analysis of the Cape Fear River estuary system in North Carolina. A numerical model of fully-coupled flow and sediment transport in open channels was used

  11. Reconstruction of Late Holocene sea-level change in French Polynesia, South Pacific, based on coral reef records

    NASA Astrophysics Data System (ADS)

    Hallmann, Nadine; Camoin, Gilbert; Eisenhauer, Anton; Vella, Claude

    2013-04-01

    Fossil reefs provide valuable sea-level indicators, which help to improve the understanding of past sea-level fluctuations and the prediction of future changes. Recent sea-level changes were reconstructed from emerged reef platforms of two high islands from the Society Islands (Bora Bora, Moorea) and two atolls from the Tuamotu Archipelago (Rangiroa, Tikehau), French Polynesia. These mid-ocean islands can be regarded as tectonically stable for the past few thousand years. Therefore, they are well suited for sea-level studies because they register Holocene eustatic changes, which are not overprinted by tectonic changes. Furthermore, the study sites are located distant from former ice sheets (far field location), which reduces the influence of the glacio-isostatic rebound. Several sea-level indicators, such as in situ coral colonies, including coral microatolls (Porites sp.), bivalves (mainly Tridacna sp.), conglomerates, beachrock, and sediments were analyzed in order to reconstruct Late Holocene relative sea-level changes. Microatolls are discoid corals that develop laterally when upward growth is limited by sea-level. Therefore, they are very accurate recorders of past sea-level. This study provides a detailed sea-level history for French Polynesia using high-precision U/Th (TIMS) dating and GPS measurements with a vertical and horizontal precision of 1-3 cm and a few millimetres, respectively. All samples were analyzed by X-ray diffraction and examined petrographically to exclude diagenetically altered material. The Holocene mean sea level in French Polynesia was thought to have been higher than present (+0.8/+1.0 m) between 5000 and 1250 yr BP, reached a highstand between 2000 and 1500 yr BP and then decreased to the present level (Pirazzoli and Montaggioni, 1988). The highstand has been reported until 1200 yr BP in the Tuamotu Archipelago (Pirazzoli and Montaggioni, 1986). However, sea-level indicators analyzed in this study reveal a highstand of at least 1.5 m

  12. As the sea level rises the Earth does not stand still

    NASA Astrophysics Data System (ADS)

    Hagen, S. C.; Alizad, K.; Bilskie, M. V.; Hovenga, P. A.; Medeiros, S. C.; Passeri, D. L.; Wang, D.

    2015-12-01

    Global mean sea level rise was largely linear over the 20th century; however, according to global satellite altimetry, the rate of rise has increased from approximately 1.6 to 3.4 mm/year. It is clear that this eustatic sea level rise has been predominantly caused by thermal expansion of ocean water (i.e., it is a manifestation of an increase in the average annual global temperature). Future projections of increased global temperatures, among others, introduce additional contributions (e.g., land ice loss and changes in land water storage) resulting in higher sea level rise that can only be accommodated by accelerations in the rate of the rise. Increased temperatures lead to changes in evapotranspiration rates, precipitation rates and patterns, etc. As the sea level changes the Earth experiences many other directly or indirectly related processes (e.g., population growth and migration, local variation in subsidence, etc.). Proper assessment of the local, regional and global impacts of relative sea level rise should include as many of these linear and nonlinear processes as possible. This presentation will explain our approach to understanding the relationships between these processes and their impacts to better equip adaptation strategies and enhance coastal resiliency. References Bilskie, M. V., et al. "Dynamics of sea level rise and coastal flooding on a changing landscape." Geophys. Res. Lett., 41(3), 2014, 927-934, doi:10.1002/2013GL058759 Church, J. A. and N. J. White, "A 20th century acceleration in global sea-level rise." Geophys. Res. Lett., 33(1), 2006, L01602 Passeri, D.L., et al. "The dynamic effects of sea level rise on low-gradient coastal landscapes: a review." Earth's Future, Online, 2015. doi:10.1002/2015EF000298 Passeri, D.L., et al. "On the significance of incorporating shoreline changes for evaluating coastal hydrodynamics under sea level rise scenarios." Nat. Haz., 75 (2), 2015, 1599-1617. doi:10.1007/s11069-014-1386-y Wang, D., et al. "Climate

  13. Climate Adaptation and Sea Level Rise

    EPA Pesticide Factsheets

    EPA supports the development and maintenance of water utility infrastructure across the country. Included in this effort is helping the nation’s water utilities anticipate, plan for, and adapt to risks from flooding, sea level rise, and storm surge.

  14. Global sea level linked to global temperature

    PubMed Central

    Vermeer, Martin; Rahmstorf, Stefan

    2009-01-01

    We propose a simple relationship linking global sea-level variations on time scales of decades to centuries to global mean temperature. This relationship is tested on synthetic data from a global climate model for the past millennium and the next century. When applied to observed data of sea level and temperature for 1880–2000, and taking into account known anthropogenic hydrologic contributions to sea level, the correlation is >0.99, explaining 98% of the variance. For future global temperature scenarios of the Intergovernmental Panel on Climate Change's Fourth Assessment Report, the relationship projects a sea-level rise ranging from 75 to 190 cm for the period 1990–2100. PMID:19995972

  15. Mangrove dieback during fluctuating sea levels.

    PubMed

    Lovelock, Catherine E; Feller, Ilka C; Reef, Ruth; Hickey, Sharyn; Ball, Marilyn C

    2017-05-10

    Recent evidence indicates that climate change and intensification of the El Niño Southern Oscillation (ENSO) has increased variation in sea level. Although widespread impacts on intertidal ecosystems are anticipated to arise from the sea level seesaw associated with climate change, none have yet been demonstrated. Intertidal ecosystems, including mangrove forests are among those ecosystems that are highly vulnerable to sea level rise, but they may also be vulnerable to sea level variability and extreme low sea level events. During 16 years of monitoring of a mangrove forest in Mangrove Bay in north Western Australia, we documented two forest dieback events, the most recent one being coincident with the large-scale dieback of mangroves in the Gulf of Carpentaria in northern Australia. Diebacks in Mangrove Bay were coincident with periods of very low sea level, which were associated with increased soil salinization of 20-30% above pre-event levels, leading to canopy loss, reduced Normalized Difference Vegetation Index (NDVI) and reduced recruitment. Our study indicates that an intensification of ENSO will have negative effects on some mangrove forests in parts of the Indo-Pacific that will exacerbate other pressures.

  16. Tectono-eustatic controls on carbonate platform development, Permian basin outcrop-subsurface

    SciTech Connect

    Sarg, J.F.; Romine, K.; Vail, P.R.

    1987-05-01

    Integration of seismic stratigraphic concepts, detailed field studies, and geohistory analysis provides powerful interpretation leverage for deciphering the geologic history of the Permian carbonate platform complexes. The structural history of the Permian basin during the Permian shows two subsidence cycles of 10 to 20 m.y. duration. These subsidence cycles played a major role in the long-term (millions to tens of millions of years) development of the Permian carbonate platforms. During periods of relatively rapid subsidence, aggradation was dominant; during times of slow subsidence, major basinward platform progradation occurred. Superimposed on the long-term tectonic cycles are a series of third-order eustatic cycles (0.5-3 m.y.) which controlled development of 23 depositional sequences. Each sequence is composed of three depositional systems tracts: (1) a lower basin-restricted wedge interpreted to have been deposited during a relative fall and lowstand of sea level; (2) a transgressive systems tract of variable thickness; and (3) an upper aggradational to progradational carbonate platform system interpreted to have been deposited during a relative highstand in sea level. The lowstand systems tracts are composed dominantly of quartz sandstone, commonly intercalated with carbonate debris beds at the toe-of-slope. Two highstand depositional styles are differentiated here: (1) a keep-up system which maintains pace with periodic rises in relative sea level and displays a mounded-oblique stratal geometry at the platform margin and (2) a catch-up system which represents a relatively slow rate of accumulation and displays a sigmoid profile at the platform margin. Sequence boundaries display erosional truncation (subaerial on shelf or at shelf edge; subaqueous on slope) and/or subaerial exposure.

  17. Future high sea levels in south Sweden

    SciTech Connect

    Blomgren, S.H.; Hanson, H.

    1997-12-31

    An estimation of future mean high water levels in Oeresund and the southwest Baltic Sea is presented together with a discussion of probable consequences for Falsterbo Peninsula, a trumpet-shaped sandy formation of some 25 km{sup 2} size situated in the very southwest corner of Sweden. A literature review coupled with sea-level measurements and observations made in the area every four hours since October 1945 are given and comprise the base for the present analysis.

  18. Reconciling Holocene Sea-Level History on the US Gulf Coast: Is the Mississippi Delta the Rosetta Stone?

    NASA Astrophysics Data System (ADS)

    Tornqvist, T. E.; Gonzalez, J. L.; Newsom, L. A.; van der Borg, K.; de Jong, A. F.; Kurnik, C. W.

    2003-12-01

    The threat of future sea-level rise is a major concern for the US Gulf Coast in general and the Misissippi Delta in particular. Published Holocene relative sea-level (RSL) curves for the US Gulf Coast are in mutual conflict, with some characterized by a smooth RSL rise akin to widely accepted eustatic sea-level curves vs. others, including several recent ones, that are characterized by a conspicuous "stair-step" pattern with prolonged (millennium-scale) RSL stillstands alternating with rapid rises. In addition, recent work in Texas and Alabama has revitalized the notion of a Middle Holocene RSL highstand, estimated at about 2 m above present mean sea level. An extensive sampling program in the Mississippi Delta (Louisiana) focuses on the collection of basal peats that accumulated during the initial transgression of the pre-existing, consolidated Pleistocene basement. We preferentially select plant macrofossils indicative of brackish to saline conditions from these basal peats and subject them to AMS 14C dating. The first data set of approximately 30 sea-level index points from a 20 sq km study area on the eastern margin of the delta provides conclusive evidence that RSL rise followed a smooth, negative exponential trend for the time interval 8000-3000 cal yr BP, thus invalidating the occurrence of RSL stillstands. Although a true Middle Holocene highstand never occurred in this subsiding setting, the high level of detail of our time series enables a rigorous test of this hypothesis. Correction of our data set for a hypothetical subsidence rate of 1.1 m/ka (we assume a linear subsidence rate compared to the tectonically relatively stable adjacent Texas Coast) leads to sea levels of 1-2 m above present during the time interval 6000-4000 cal yr BP. However, this model also implies a RSL position near -2 m around 8000 cal yr BP, which is inconsistent both with data of this age from Texas, as well as with eustatic sea-level data. We therefore conclude that a Middle

  19. Glacier Contributions to Sea Level Rise

    NASA Astrophysics Data System (ADS)

    Gardner, A. S.; Cogley, J. G.; Moholdt, G.; Wouters, B.; Wiese, D. N.

    2015-12-01

    Global mean sea level is rising in response to two primary factors: warming oceans and diminishing glaciers and ice sheets. If melted completely, glaciers would raise sea levels by half a meter, much less than that the 80 meters or so that would result from total melt of the massive Greenland and Antarctic ice sheets. That is why glacier contributions to sea level rise have been less studied, allowing estimates of to vary widely. Glacier contributions to sea level change are challenging to quantify as they are broadly distributed, located in remote and poorly accessible high latitude and high altitude regions, and ground observations are sparse. Advances in satellite altimetry (ICESat) and gravimetry (GRACE) have helped, but they also have their own challenges and limitations. Here we present an updated (2003-2014) synthesis of multiple techniques adapted for varying regions to show that rates of glacier loss change little between the 2003-2009 and 2003-2014 periods, accounting for roughly one third of global mean sea level rise. Over the next century and beyond glaciers are expected to continue to contribute substantial volumes of water to the world's oceans, motivating continued study of how glaciers respond to climate change that will improve projections of future sea levels.

  20. Thermosteric sea level rise for the past 50 years; comparison with tide gauges and inference on water mass contribution

    NASA Astrophysics Data System (ADS)

    Lombard, Alix; Cazenave, Anny; DoMinh, Kien; Cabanes, Cecile; Nerem, R. Steven

    2005-10-01

    In this paper we compare sea level trends observed at a few selected tide gauges of good quality records with thermosteric (i.e., due to ocean temperature change) sea level trends over 1950-1998 using different gridded ocean temperature data sets from Levitus et al. (2000) [Levitus, S., Stephens, C., Antonov, J.I., Boyer, T.P., 2000. Yearly and Year-Season Upper Ocean Temperature Anomaly Fields, 1948-1998. U.S. Gov. Printing Office, Washington, D.C. pp. 23.], Ishii et al. (2003) [Ishii, M., Kimoto, M., Kachi, M., 2003. Historical ocean subsurface temperature analysis with error estimates, Mon. Weather Rev., 131, 51-73.] and Levitus et al. (2005) [Levitus S., Antonov, J.I., Boyer, T.P., 2005. Warming of the world ocean, 1955-2003. Geophys. Res. Lett. 32, L02604. doi:10.1029/2004GL021592.]. When using the Levitus data, we observe very high thermosteric rates at sites located along the northeast coast of the US, north of 37°N. Such high rates are not observed with the Ishii data. Elsewhere, thermosteric rates agree reasonably well whatever the data set. Excluding the northeast US coastline sites north of 37°N, we compare tide gauge-based sea level trends with thermosteric trends and note that, in spite of a significant correlation, the latter are too small to explain the observed trends. After correcting for thermosteric sea level trends, residual (observed minus thermosteric) trends have an average value of 1.4 ± 0.5 mm/year, which should have an eustatic (i.e., due to ocean mass change) origin. This result supports the recent investigation by Miller and Douglas (2004) [Miller, L., Douglas, B.C., 2004. Mass and volume contributions to 20th century global sea level rise. Nature 428, 406-408.] which suggests that a dominant eustatic contribution is needed to explain the rate of sea level rise of the last decades observed by tide gauges, and shows that Cabanes et al. (2001) [Cabanes, C., Cazenave, A., Le Provost, C., 2001. Sea level rise during past 40 years

  1. Shallow stratigraphy and sedimentation history during high-frequency sea-level changes on the central California shelf

    USGS Publications Warehouse

    Grossman, E.E.; Eittreim, S.L.; Field, M.E.; Wong, F.L.

    2006-01-01

    Analyses of high-resolution seismic-reflection data and sediment cores indicate that an extensive sediment deposit on the central California continental shelf is comprised of several late-Pleistocene to Holocene age facies. Offshore of the littoral zone, in water depths of 30-90 m, a 3-6 m thick veneer of fine sediment referred to as the mid-shelf mudbelt has formed along 50-100 km of the coast. The mudbelt drapes a parasequence characterized by prograding clinoforms that in places overlies a 1-3 m thick basal transgressive lag deposit. These facies overlie a prominent erosional unconformity that extends from the shore to the outer shelf. Eighteen calibrated 14CAMS ages of marine molluscs and terrestrial wood detritus sampled in cores range 15,800 yr BP to modern indicating a postglacial age for these sediments (one >55,000 yr BP represents relict sand). We model accumulation of these facies using (1) the topography of the underlying erosional unconformity interpreted from seismic reflection profiles, (2) observed sediment facies (grain size) distribution across the shelf (a proxy for wave/current sediment partitioning), and published estimates of (3) eustatic sea-level history, and (4) regional tectonics. Our model and data indicate that deposition of the transgressive lag began during early, slow postglacial sea-level rise and that a notable change in depositional environment occurred across an area of more than 200 km2 of the outer shelf likely in response to abrupt drowning during Meltwater Pulse 1B (11,500 yr BP). We propose that rapid progradation of clinoforms may have occurred during transgression because of the unique interaction of modest rates of sediment input and tectonic uplift, variable rates of eustatic sea-level rise and a complex stepped antecedent topography.

  2. Tritium level along Romanian Black Sea Coast

    SciTech Connect

    Varlam, C.; Stefanescu, I.; Popescu, I.; Faurescu, I.

    2008-07-15

    Establishing the tritium level along the Romanian Black Sea Coast, after 10 years of exploitation of the nuclear power plant from Cernavoda, is a first step in evaluating its impact on the Black Sea ecosystem. The monitoring program consists of tritium activity concentration measurement in sea water and precipitation from Black Sea Coast between April 2005 and April 2006. The sampling points were spread over the Danube-Black Sea Canal - before the locks Agigea and Navodari, and Black Sea along the coast to the Bulgarian border. The average tritium concentration in sea water collected from the sampling locations had the value of 11.1 {+-} 2.1 TU, close to tritium concentration in precipitation. Although an operating nuclear power plant exists in the monitored area, the values of tritium concentration in two locations are slightly higher than those recorded elsewhere. To conclude, it could be emphasized that until now, Cernavoda NPP did not had any influence on the tritium concentration of the Black Sea Shore. (authors)

  3. Development of the Bulgarian Sea Level Service

    NASA Astrophysics Data System (ADS)

    Palazov, Atanas

    2013-04-01

    Systematic sea level measurements have been started in Bulgaria in the beginning of 20th century and nowadays there are 16 coastal sea level stations in operation. Operators of sea level stations are: National Institute of Meteorology and Hydrology, Bulgarian Academy of Sciences (NIMH) - 6 stations, Cadastre Agency, Ministry of Regional Development and Public Works (CA) - 4 stations, Port Infrastructure (PI) - 5 stations and Institute of Oceanology, Bulgarian Academy of Sciences (IO-BAS) - 1 station. Six of them are able to provide real time data. The sea level observations in the network of NIMH, performed at six main Bulgarian ports using standard poles, started in 1910. The program, implemented on the NIMH stations, includes daily measurements of the sea level with water gauges (poles). The position of a zero mark of the water gauge is checked once per year. The sea level network of the CA consists of 4 stations: Varna and Burgas (operational since 1928), Irakly and Ahtopol (since 1971). These stations are equipped with stilling-well tide gauges and with mechanical writing devices which draws sea level changes on paper. A mechanical paper writing instruments were installed in Varna and Burgas during 1928 and in 1971, a new paper writing instruments of type SUM (Russian) were installed in the stations of Irakly and Ahtopol. A set of five sea level stations in the ports of Balchik, Varna west, Pomorie, Burgas and Oil port Burgas was build during 2009 in the frame of Port Operational Marine Observing System (POMOS), equipped with high accuracy microwave instruments and operated by PI. In 2010 a new sea level station was set up in the IO-BAS coastal research base Shkorpolovtci. The station is equipped with high accuracy microwave instrument. These six stations are providing real time data. According to the decision of the Council of Ministers in 2012 sea level stations in Varna, Irakly, Burgas and Ahtopol will be operated jointly by Bulgarian Academy of Sciences and

  4. A benchmark study of the sea-level equation in GIA modelling

    NASA Astrophysics Data System (ADS)

    Martinec, Zdenek; Klemann, Volker; van der Wal, Wouter; Riva, Riccardo; Spada, Giorgio; Simon, Karen; Blank, Bas; Sun, Yu; Melini, Daniele; James, Tom; Bradley, Sarah

    2017-04-01

    The sea-level load in glacial isostatic adjustment (GIA) is described by the so called sea-level equation (SLE), which represents the mass redistribution between ice sheets and oceans on a deforming earth. Various levels of complexity of SLE have been proposed in the past, ranging from a simple mean global sea level (the so-called eustatic sea level) to the load with a deforming ocean bottom, migrating coastlines and a changing shape of the geoid. Several approaches to solve the SLE have been derived, from purely analytical formulations to fully numerical methods. Despite various teams independently investigating GIA, there has been no systematic intercomparison amongst the solvers through which the methods may be validated. The goal of this paper is to present a series of benchmark experiments designed for testing and comparing numerical implementations of the SLE. Our approach starts with simple load cases even though the benchmark will not result in GIA predictions for a realistic loading scenario. In the longer term we aim for a benchmark with a realistic loading scenario, and also for benchmark solutions with rotational feedback. The current benchmark uses an earth model for which Love numbers have been computed and benchmarked in Spada et al (2011). In spite of the significant differences in the numerical methods employed, the test computations performed so far show a satisfactory agreement between the results provided by the participants. The differences found can often be attributed to the different approximations inherent to the various algorithms. Literature G. Spada, V. R. Barletta, V. Klemann, R. E. M. Riva, Z. Martinec, P. Gasperini, B. Lund, D. Wolf, L. L. A. Vermeersen, and M. A. King, 2011. A benchmark study for glacial isostatic adjustment codes. Geophys. J. Int. 185: 106-132 doi:10.1111/j.1365-

  5. Tectonic and glacio-eustatic influences on Late Cambrian-Early Devonian first-order stratigraphic and faunal suites in the Great Basin

    SciTech Connect

    Berry, W.B.N. )

    1991-02-01

    The Late Cambrian to middle Devonian stratigraphic and faunal record i the western United States may be divided into at least five first-order or primary depositional cycles delimited by tectonically controlled sea level changes. These tectonically controlled sea level changes essentially are changes in rate of platform subsidence. Rate of platform subsidence is reflected in changes in the succession of depositional environments. Tectonically controlled sea level changes are reflected in the succession of faunas as well as in the depositional environment record. The primary rate of subsidence-related sea level changes took place at the following times: latest Cambrian, latest Ibexian (Early Ordovician), and late Early Devonian. A prominent set of glacio-eustatic sea level changes occurred in the latest Ordovician-earliest Silurian. That glacial interval was one in which significant mass mortalities and subsequent re-radiations took place among marine invertebrates. Although the boundaries of the first-order cycles, both in the stratigraphic depositional cycles appear to be diachronous across the Great Basin, the rock suites comprising the cycles are delimited clearly. Second-order cycles may be recognized within the first-order cycles, both in the stratigraphic and faunal record. The second-order cycles also reflect sea level changes. Major oceanic surface water currents were deflected around plate and related platform margins during intervals of regression from the platform, enhancing upwelling along the plate margins during such intervals.

  6. 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

  7. Sea Level Rise Impacts On Infrastructure Vulnerability

    NASA Astrophysics Data System (ADS)

    Pasqualini, D.; Mccown, A. W.; Backhaus, S.; Urban, N. M.

    2015-12-01

    Increase of global sea level is one of the potential consequences of climate change and represents a threat for the U.S.A coastal regions, which are highly populated and home of critical infrastructures. The potential danger caused by sea level rise may escalate if sea level rise is coupled with an increase in frequency and intensity of storms that may strike these regions. These coupled threats present a clear risk to population and critical infrastructure and are concerns for Federal, State, and particularly local response and recovery planners. Understanding the effect of sea level rise on the risk to critical infrastructure is crucial for long planning and for mitigating potential damages. In this work we quantify how infrastructure vulnerability to a range of storms changes due to an increase of sea level. Our study focuses on the Norfolk area of the U.S.A. We assess the direct damage of drinking water and wastewater facilities and the power sector caused by a distribution of synthetic hurricanes. In addition, our analysis estimates indirect consequences of these damages on population and economic activities accounting also for interdependencies across infrastructures. While projections unanimously indicate an increase in the rate of sea level rise, the scientific community does not agree on the size of this rate. Our risk assessment accounts for this uncertainty simulating a distribution of sea level rise for a specific climate scenario. Using our impact assessment results and assuming an increase of future hurricanes frequencies and intensities, we also estimate the expected benefits for critical infrastructure.

  8. Solution notches, earthquakes, and sea level, Haiti

    NASA Astrophysics Data System (ADS)

    Schiffman, C. R.; Mildor, B. S.; Bilham, R. G.

    2010-12-01

    Shortly after the 12 January 2010 Haiti earthquake, we installed an array of five tide gauges to determine sea level and its variability in the region of uplifted corals on the coast SW of Leogane, Haiti, that had been uplift ≤30 cm during the earthquake. Each gauge consists of a pressure transducer bolted 50-80 cm below mean sea level, which samples the difference between atmospheric pressure and sea pressure every 10 minutes. The data are transmitted via the Iridium satellite and are publically available with a latency of 10 minutes to 2 hours. The measurements reveal a maximum tidal range of ≈50 cm with 2-4 week oscillations in mean sea level of several cm. Sea slope, revealed by differences between adjacent gauges, varies 2-5 cm per 10 km at periods of 2-5 weeks, which imposes a disappointing limit to the utility of the gauges in estimating post seismic vertical motions. A parallel study of the form and elevation of coastal notches and mushroom rocks (rocks notched on all sides, hence forming a mushroom shape), along the coast west of Petit Goave suggests that these notches may provide an uplift history of the region over the past several hundreds of years. Notch sections in two areas were contoured, digitized, and compared to mean sea level. The notches mimic the histogram of sea level, suggesting that they are formed by dissolution by acidic surface waters. Notches formed two distinct levels, one approximately 58 cm above mean sea level, and the other approximately 157 cm above mean sea level. Several landslide blocks fell into the sea during the 2010 earthquake, and we anticipate these are destined for conversion to future mushroom rocks. Surfaces have been prepared on these blocks to study the rate of notch formation in situ, and samples are being subjected to acid corrosion in laboratory conditions, with the hope that the depth of notches may provide an estimate of the time of fall of previous rocks to help constrain the earthquake history of this area

  9. Results of TOPEX/Poseidon-Jason Calibration and Recent Changes in Global Mean Sea Level

    NASA Astrophysics Data System (ADS)

    Leuliette, E. W.; Nerem, R. S.; Mitchum, G. T.

    2003-12-01

    The Jason-1 radar altimetry mission was designed to resolve changes in global mean sea level variation to provide for studies of interannual sea level change. We have completed a calibration of the Jason-1 measurements as part of an effort to continue the 10-year time series of sea level change measurements compiled by the TOPEX/ POSEIDON (T/P) mission. We have completed detailed comparisons of the T/P and Jason-1 sea level measurements, including each of the measurement corrections using the latest instrument and geophysical corrections, including precise orbits and sea-state bias models. We present the results of cross-satellite and independent tide gauge calibrations. In late 2002 global mean sea level (GMSL) as measured by Jason-1 and TOPEX/POSEIDON satellite altimetry surged by 15 mm over a period of a few weeks. This anomaly is on the order of the longer surge seen during the strong El Niño event of 1998. Interannual and low-frequency signals in sea level variability can have significant effects on the recovery of secular trends in short records. Nerem et al. [1999] estimated that one would need at least 10 years of continuous altimeter coverage to resolve a 2 mm yr-1 secular trend with an accuracy of 0.5 mm yr-1 in the presence of ENSO variability. Similarly, Chambers et al. [2002] have observed that long-term GMSL from tide gauges is significantly affected by El Niño/Southern Oscillation (ENSO) climate cycles, although the size of the Southern Oscillation Index (SOI) does not predict the magnitude of change in GMSL. Sea level anomalies associated with El Niño events are mostly attributable to steric changes in the ocean. However, thermal affects mask eustatic changes due to the addition of water to the ocean, such as surges in glacier melt [Dyurgerov, 2002]. We use results from satellite altimetry, Expendable Bathythermograph, and the Estimating the Circulation and Climate of the Ocean (ECCO) model to investigate the spatial extent and depth distribution

  10. Contribution of mountain glaciers and ice caps to sea-level rise

    NASA Astrophysics Data System (ADS)

    Hock, R. M.; de Woul, M.; Radic, V.; Dyurgerov, M.

    2009-12-01

    Mountain glaciers and ice caps (MG&IC) have been identified as primary source of eustatic sea level rise, ahead of the ice sheets, during recent decades. The Intergovernmental Panel on Climate Change (IPCC) estimates that the sum of all contributions to sea-level rise for the period 1961-2004 was 1.1± 0.5 mm a-1, leaving 0.7±0.7 of the 1.8±0.5 mm a-1 observed sea-level rise unexplained. Here, we compute the global surface mass balance of all mountain glaciers and ice caps and find that part of this much-discussed gap can be attributed to a larger contribution than previously assumed from mass loss of MG&IC, especially those around the Antarctic Peninsula. We find a global surface mass loss of all MG&IC of 0.79±0.34 mm a-1 sea-level equivalent compared to IPCC’s 0.50±0.18 mm a-1. The Antarctic MG&IC contributed 28% of the global estimate due to exceptional warming around the Antarctic Peninsula and high mass-balance sensitivities to temperature similar to those we find in maritime Iceland, Patagonia and Alaska. Our results highlight the role of the MG&IC around the Antarctic Peninsula where climate is distinctly different from the cold conditions of the ice sheet, and large mass balance sensitivities to temperature, exceptional warming and large area combine to yield large potential for glacier mass loss. We emphasize an urgent need for improved glacier inventory and in-situ mass balance data from this region especially in light of recently accelerated mass loss from MG&IC.

  11. Sea level and diagenesis: a case study on Pleistocene beaches, Whalebone Bay, Bermuda

    NASA Astrophysics Data System (ADS)

    Vollbrecht, R.; Meischner, D.

    1993-07-01

    Pleistocene fluctuations of sea level have left marine and aeolian limestones intercalated with glacial red soils on the Bermuda Carbonate Platform (Atlantic, 64°50'W, 32°20'N). Successive eustatic highstands of similar amplitude drowned the tectonically stable platform and piled up similar sets of sediments. Up to three Pleistocene beaches are stacked in shorelines sections. Post-depositional diagenetic histories of these beaches can be linked to repeated changes in sea level and pore waters. This paper presents field evidence and petrographic results (microscope, X-ray, cathodoluminescence, SEMEDAX) for the diagenetic histories of two superimposed Pleistocene beaches in Whalebone Bay, Bermuda North Shore. The younger beach was deposited during isotopic stage 5e, about 120 ka ago. The age of the older beach may be isotopic stage 9 or older. Diagenesis drastically altered the older beach before the stage 5e transgression. Primary high-Mg calcite (HMC) and aragonite were no longer present. Marine skeletal grains were instead leached or recrystallized to low-Mg calcite (LMC). Primary and secondary pore space were largely reduced by LMC cement. Lines of needle relics reminiscent of marine aragonite cement occur as inclusions within syntaxial rim cements around echinoderm grains, indicating that a marine influence had at least once interrupted this period of freshwater alteration. Finally, before the rocks became buried by the sediments of the younger beach, a crust of marine, bladed HMC cement was precipitated throughout the pore space. The younger beach consists of skeletal grains that are, apart from the effects of non-selective dissolution, essentially unaltered. The sediments are only weakly lithified by cryptocrystalline LMC showing an alveolar texture, tangential fibres and other features characteristic of calichification. A younger post-depositional marine influence is not recorded. These results suggest that, under favourable conditions, diagenetic processes

  12. Cenomanian sea level high: a global signal modified by long wavelength deformations of mantellic origin

    NASA Astrophysics Data System (ADS)

    Robin, Cecile; Ostanciaux, Emilie; Guillocheau, François; Husson, Laurent; Trotin, Guillaume

    2013-04-01

    Late Cenomanian (93 Ma) is expected to be the period of highest sea-level of all Meso-Cenozoic times, with a value of more than 250 m above present-day sea level (Haq et al., 1987). This maximum marine flooding is not observed in many areas of the world (e.g. South-western Africa, northern Australia, etc…). This suggests that other very long wavelength processes can be superimposed, such as vertical movements due to mantle dynamic (dynamic topography). In order to evaluate the space and time evolution of relative sea level variations, we compiled world-scale transgression and regression maps for two time-lines: the Albian-Cenomanian boundary and the Cenomanian-Turonian boundary. This study is based on published stratigraphic and sedimentologic data, quite heterogenous in resolution and quality. Results show that the Cenomanian transgressive phase is essentially present around the Tethys, whereas regression prevails at higher latitudes (northern Canada and Europe - southwestern Africa and Australia) and along the pacific margin of eastern Asia. We tested two processes (1) dynamic topography using the models of Muller et al. (2008) and Flament et al. (2012) and (2) vertical movements due to mantle global cooling in response to continental break-up (Coltice et al., 2009; Phillips & Coltice, 2010). For the subduction zones (e.g. southern Europe or eastern Asia), dynamic topography and the change of slab buoyancy can explained the observed transgression and regression. On the contrary, the decrease of the temperature below the continents inherited from the Pangea break-up can explained the relative sea level variations along the Atlantic margins. In conclusion, the stratigraphic record in the world sedimentary basins is controlled by an eustatic signal due to the volume change of the ocean, on which is superimposed long wavelength deformations due to mantle dynamic or temperature changes below the continent lithosphere.

  13. 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.

  14. 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

  15. Estimating the sources of global sea level rise with data assimilation techniques

    NASA Astrophysics Data System (ADS)

    Hay, Carling C.; Morrow, Eric; Kopp, Robert E.; Mitrovica, Jerry X.

    2013-02-01

    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.

  16. Bayesian Prediction and Projection of Sea Levels

    NASA Astrophysics Data System (ADS)

    Berliner, M.

    2014-12-01

    I will begin with a brief review of Bayesian hierarchical modeling and then turn to a model for sea levels. It is well-accepted that global sea levels have been rising in response to rising global temperatures. The strategy is the development of a Bayesian hierarchical model of sea levels. The hierarchical nature of the model is formulated to enable inference at various spatial scales. Further, temperature is incorporated in the model as a predictor or explanatory variable. Hence, information regarding future sea levels provided by the model rely on information regarding future temperatures. Forming predictions of future temperatures can be done in severalways, depending on the goals of the analysis. I consider two classes of goals. In the first we seek short-term or medium-range forecasts as in weather-like forecasting. In the second we seek projections of sea levels under various emissions scenarios as in studies of the impacts of climate change. I illustrate methods and results for each class and suggest how results can contribute to decision support.

  17. Upper Limit for Regional Sea Level Projections

    NASA Astrophysics Data System (ADS)

    Jevrejeva, Svetlana; Jackson, Luke; Riva, Riccardo; Grinsted, Aslak; Moore, John

    2016-04-01

    With more than 150 million people living within 1 m of high tide future sea level rise is one of the most damaging aspects of warming climate. The latest Intergovernmental Panel on Climate Change report (AR5 IPCC) noted that a 0.5 m rise in mean sea level will result in a dramatic increase the frequency of high water extremes - by an order of magnitude, or more in some regions. Thus the flood threat to the rapidly growing urban populations and associated infrastructure in coastal areas are major concerns for society. Hence, impact assessment, risk management, adaptation strategy and long-term decision making in coastal areas depend on projections of mean sea level and crucially its low probability, high impact, upper range. With probabilistic approach we produce regional sea level projections taking into account large uncertainties associated with Greenland and Antarctica ice sheets contribution. We calculate the upper limit (as 95%) for regional sea level projections by 2100 with RCP8.5 scenario, suggesting that for the most coastlines upper limit will exceed the global upper limit of 1.8 m.

  18. Eustatic and tectonic controls on development and demise of Waulsortian carbonate buildups, Montana

    SciTech Connect

    Precht, W.F.; Shepard, W.

    1989-03-01

    Deeper water Waulsortian carbonate buildups of Kinderhookian age are known from four localities in Montana. These buildups are situated within rhythmically bedded carbonate mudstones in the Paine Member of the Lodgepole formation. These buildups are mud-rich, byrozoan-crinoid mounds which contain abundant stromatactoid-like spar-filled cavities. The buildups are located along downdropped blocks on bounding faults of the Central Montana trough related to reactivation of a middle Proterozoic intracratonic rift margin (aulacogen). Sequence stratigraphic analyses of the Lodgepole throughout central Montana forms the basis for interpretation of buildup development and demise. Opening of the trough coupled with sea level rise formed three distinct members of the Lodgepole, including (1) a transgressive surface marked by shallow-water deposits of the Cottonwood Canyon Member, (2) a transgressive systems tract of the Paine Member which can be separated into two distinct facies - a condensed section of deeper water carbonate mudstones to wackestones and the Waulsortian buildup facies which are encased within these rhythmically bedded deposits, and (3) a high-stand systems tract characterized by high-energy, cyclic, shoaling-upward crinoidal grainstones and oolites of the Woodhurst Member. Rapid eustatic rise and syntectonic subsidence during the transgressive systems tract outpassed buildup development and led to subsequent drowning. The lack of rapid reef building metazoans during the Mississippian is also suspect in explaining Waulsortian buildup demise.

  19. Late Quaternary climatic events and sea-level changes recorded by turbidite activity, Dakar Canyon, NW Africa

    NASA Astrophysics Data System (ADS)

    Pierau, Roberto; Hanebuth, Till J. J.; Krastel, Sebastian; Henrich, Rüdiger

    2010-03-01

    The relationship of sea-level changes and short-term climatic changes with turbidite deposition is poorly documented, although the mechanisms of gravity-driven sediment transport in submarine canyons during sea-level changes have been reported from many regions. This study focuses on the activity of the Dakar Canyon off southern Senegal in response to major glacial/interglacial sea-level shifts and variability in the NW-African continental climate. The sedimentary record from the canyon allows us to determine the timing of turbidite events and, on the basis of XRF-scanning element data, we have identified the climate signal at a sub-millennial time scale from the surrounding hemipelagic sediments. Over the late Quaternary the highest frequency in turbidite activity in the Dakar Canyon is confined to major climatic terminations when remobilisation of sediments from the shelf was triggered by the eustatic sea-level rise. However, episodic turbidite events coincide with the timing of Heinrich events in the North Atlantic. During these times continental climate has changed rapidly, with evidence for higher dust supply over NW Africa which has fed turbidity currents. Increased aridity and enhanced wind strength in the southern Saharan-Sahelian zone may have provided a source for this dust.

  20. Extended Late Pleistocene Sea Level Record

    NASA Astrophysics Data System (ADS)

    Fairbanks, R. G.; Cao, L.; Mortlock, R. A.

    2006-12-01

    Several hundred new closed system 230Th/234U and radiocarbon dates and the addition of more cores and coral samples from the islands of Barbados, Kiritimati and Araki contribute to an enhanced sea level record for the late Pleistocene ranging from the present to 240,000 yrs BP. Application of more rigorous sample screening criteria, including redundant 231Pa/235U dates have resulted in more closed system ages and better sea level resolution. In addition, a multibeam survey has mapped an extensive glacial lowstand reef on a ridge south of Barbados that is capped by a set of pinnacle reefs that grew during the early deglaciation. Among our new observations, the more detailed Barbados sea level record now resolves a Younger Dryas still- stand and a sea level drop between 16,140 and 14,690, overlapping the timing of H1 by some age estimates. The coral ages bracketing melt water pulse 1A have been further refined to 14,082 +/- 28 yrs BP and 13,632 +/- 32 yrs BP (2-sigma). The Isotope Stage 3 interstadial ended with sea level near 87.5 meters below present at 29,500 years ago before dropping to full glacial levels. The last glacial sea level lowstand began as early as 26,000 yrs BP. Extensive dating of Marine Isotope Stage 3 interstadial reefs on the islands of Araki and Barbados have added considerable resolution to this time interval and reliably bracket lowstand intervals separating the interstadials. A new diagenesis model has improved our prospecting success for closed system ages from older reefs and added some critical dates to the sparse closed-system data set for MIS-5 and MIS-7 high stand reefs..

  1. 3000 Years of Sea Level Change.

    NASA Astrophysics Data System (ADS)

    Tanner, William F.

    1992-03-01

    Sea level change is generally taken to indicate climate change, and may be more nearly global than what we perceive to be climate change. Close to the beach, even a small sea level change (such as 1-3 m) produces important changes in local depositional conditions. This effect can be deduced from a study of properly selected beach deposits.Various measures of beach-sand grain size indicate conditions of deposition. The best of these parameters is the kurtosis; it is a reliable indicator of surf-zone wave energy density. An abrupt energy-level shift, after centuries with little change, indicates sea level rise or drop. Kurtosis, within stated limits, shows this.Beach ridge systems (successive, distinct old beach deposits) span the last several thousand years. A sequence of sand samples across such a deposit provides grain-size evidence for alternating high and low sea level. Changes were 1 to 3 m vertically, and took place at rates of about 1 ern yr1. There were at least seven such events in the last 3000 years.The two most recent changes were the drop and subsequent rise that marked the Little Ice Age (starting about 1200 A.D.). One cannot say, from these data, that the planet has come fully out of the Little ice Age. Predictions about what sea level will do in the near future should be based on the many small changes (1 to 3 m) in the last few thousand years, rather than on the arbitrary, fictitious, and unrealistic absolute sea level that appears to underlie various popular forecasts.

  2. Insights about the interaction between sea-level rise, sediment accumulation and subsidence: the example of the Ganges Brahmaputra Delta during the Holocene

    NASA Astrophysics Data System (ADS)

    Grall, C.; Steckler, M. S.; Pickering, J.; Goodbred, S. L., Jr.; Sincavage, R.; Hossain, S.; Paola, C.; Spiess, V.

    2016-12-01

    The hazard associated with sea-level rise (shoreline erosion, flooding and wetlands loss) may dramatically increase when human interventions interfere with the natural responses of the coastal regions to the eustatic rise. We here provide insights about such natural processes, by documenting the manner in which subsidence, sediment input and sediment distribution interact together during the well-known Holocene eustatic rise period, in the Ganges- Brahmaputra-Meghna Delta (GBMD) in Bangladesh. The dataset combines more than 400 hand-drilled stratigraphic wells, 185 radiocarbon ages, and seismic reflection imaging data (255 km of high resolution multichannel seismic dataset), collected thanks to recent research in the BanglaPIRE project. We use two independent approaches for analyzing this broad dataset. First, we estimate the total volume of Holocene sediments in the GBMD. In doing so, we define empirical laws to build up a virtual model of sediment accumulation that takes into account the contrasts in accumulation between rivers and alluvial plains as well as the regional seaward gradient of sediment accumulation. As the evolution of river occupation over the Holocene at the regional scale is now relatively well constrained, we estimate the total volume of sediment deposited in the Delta during the Holocene. Secondly, we use detailed age-models of sediment accumulation at 92 sites (based on 185 radiocarbon ages) for distinguishing the effects of eustasy and subsidence on the sediment accumulation in the different domains of the delta (namely the tidal dominated plain and the fluvial dominated plain). Using these two independent approaches, we are able to quantify the natural subsidence and the relative distribution of subsidence. We emphasize the difference between the subsidence and the sediment accumulation, by showing that sediment accumulation is more than twice the subsidence on average during the Holocene, which allows us to quantify the increase of sediment

  3. Visualizing Sea Level Rise with Augmented Reality

    NASA Astrophysics Data System (ADS)

    Kintisch, E. S.

    2013-12-01

    Looking Glass is an application on the iPhone that visualizes in 3-D future scenarios of sea level rise, overlaid on live camera imagery in situ. Using a technology known as augmented reality, the app allows a layperson user to explore various scenarios of sea level rise using a visual interface. Then the user can see, in an immersive, dynamic way, how those scenarios would affect a real place. The first part of the experience activates users' cognitive, quantitative thinking process, teaching them how global sea level rise, tides and storm surge contribute to flooding; the second allows an emotional response to a striking visual depiction of possible future catastrophe. This project represents a partnership between a science journalist, MIT, and the Rhode Island School of Design, and the talk will touch on lessons this projects provides on structuring and executing such multidisciplinary efforts on future design projects.

  4. Sea Level Rise in Santa Clara County

    NASA Technical Reports Server (NTRS)

    Milesi, Cristina

    2005-01-01

    Presentation by Cristina Milesi, First Author, NASA Ames Research Center, Moffett Field, CA at the "Meeting the Challenge of Sea Level Rise in Santa Clara County" on June 19, 2005 Santa Clara County, bordering with the southern portion of the San Francisco Bay, is highly vulnerable to flooding and to sea level rise (SLR). In this presentation, the latest sea level rise projections for the San Francisco Bay will be discussed in the context of extreme water height frequency and extent of flooding vulnerability. I will also present preliminary estimations of levee requirements and possible mitigation through tidal restoration of existing salt ponds. The examples will draw mainly from the work done by the NASA Climate Adaptation Science Investigators at NASA Ames.

  5. Sea level trends and interannual variability in the Caribbean Sea

    NASA Astrophysics Data System (ADS)

    Torres, R.; Tsimplis, M.

    2012-04-01

    Sea level trends and interannual variability has been investigated in the Caribbean Sea using altimetry and tide gauge time series from 19 stations. Relative sea level trends range between -2.0 and 10.7 mm/y depending on the length of the available record. Records from stations longer than 40 years converge toward values between 1.2 - 5.2 mm/yr, still a significant range which in some stations is less and in some other significantly larger than the global average. The longest station, Cristobal (102 years) shows a trend of 1.9 mm/yr and, in addition a significant acceleration of 1.6±0.3 mm/y/cy. The observed sea level trends are not affected by the atmospheric pressure effect, within the levels of significance. They are also the same (within the levels of significance) at all seasons. Altimetry shows trends (over 18 years of data) with values up to 5.2 mm/y. In some areas the values are statistically insignificant, but at no areas statistically significant negative values are found. Steric trends from the top 800 m (over the period of altimetric observations) have a basin average trend of 1 mm/y, but it shows large spatial variability with negative trends of -7 mm/y in the Yucatan Basin and positive trends up to 4.9 mm/y in the Venezuela Basin. Decadal trends were found to vary significantly at tide-gauge records as well as altimetric and steric measurements. We further explore the residual interannual variability by comparison with surface wind and climatic indices. This analysis is supported by the Lloyd's Register Trust Fund project Marine Extremes.

  6. The Sea Level Fingerprints of Global Change

    NASA Astrophysics Data System (ADS)

    Mitrovica, J. X.; Hay, C.; Kopp, R. E., III; Morrow, E.

    2014-12-01

    It may be difficult to persuade those living in northern Europe that the sea level changes that their coastal communities face depends less on the total melting of polar ice sheets and glaciers than on the individual contributions to this total. In particular, melting of a specific ice sheet or mountain glacier drives deformational, gravitational and rotational perturbations to the Earth system that are manifest in a unique geometry, or fingerprint, of global sea level change. For example, melting from the Greenland Ice Sheet equivalent to 1 mm/yr of global mean sea level (GMSL) rise will lead to sea level rise of ~0 mm/yr in Dublin, ~0.2 mm/yr in Amsterdam, ~0.4 mm/yr in Boston and ~1.2 mm/yr in Cape Town. In contrast, if the same volume of ice melted from the West Antarctic Ice Sheet, all of the above sites would experience a sea level rise in the range 1.1-1.2 mm/yr. These fingerprints of modern ice melting, together with ocean thermal expansion and dynamic effects, and the ongoing signal from glacial isostatic adjustment in response to the last ice age, combine to produce a sea level field with significant geographic variability. In this talk I will highlight an analysis of global tide gauge records that takes full advantage of this variability to estimate both GMSL and the sources of meltwater over the last century, and to project GMSL to the end of the current century.

  7. Aptian-Albian sea level history from Guyots in the western Pacific

    NASA Astrophysics Data System (ADS)

    RöHl, Ursula; Ogg, James G.

    1996-10-01

    Relative sea level fluctuations are an important control on patterns of sedimentation on continental margins and provide a valuable tool for regional correlations. One of the main objectives of combined Ocean Drilling Program Legs 143 and 144 was drilling the thick carbonate caps of a suite of seamounts, called guyots, scattered over the northwestern Pacific. The array of drowned Cretaceous banks includes four carbonate banks of Aptian-Albian age. These particular carbonate banks display emergent surfaces if regional sea level falls faster than the rate of guyot subsidence, or intervals of condensed parasequences and well-cemented peritidal crypto-algal flats if the rate of sea level fall is slightly less than guyot subsidence. Rapid rises of sea level following these sequence boundaries are recorded as drowning of the emergent horizons or as pronounced deepening of facies. The cored lithologies and downhole geophysical and geochemical logs were used to identify depositional sequences and surfaces of exceptional shallowing or deepening. A combination of biostratigraphic datums, carbon and strontium isotope curves, relative magnitude of surfaces of emergence, relative thicknesses of depositional sequences, sea level events, and counts of upward shallowing cycles or parasequences were used to correlate sequences among the four sites. After compensating for thermal subsidence rates at each guyot, an identical pattern of major Aptian-Albian eustatic sea level events is evident throughout this large portion of the Pacific Ocean. There are approximately 12 Aptian and 12 Albian significant sequence boundaries, of which a third were associated with major episodes of emergence. When these events are compared with Aptian-Albian relative sea level changes observed in European shelf successions, the major sequence boundaries and transgressive surges can be easily correlated, and it appears that both regions also display the same number of minor events. Therefore we can apply

  8. Diagenesis in limestone-dolostone successions after 1 million years of rapid sea-level fluctuations: A case study from Grand Cayman, British West Indies

    NASA Astrophysics Data System (ADS)

    Ren, Min; Jones, Brian

    2016-08-01

    Meteoric diagenesis in young marine carbonate sediments has commonly been linked to fluctuations in Quaternary glacio-eustatic sea levels. The extent to which these sea-level changes are recorded in these carbonate successions, however, remains questionable. This is amply demonstrated by the diagenetic record found in the limestones and dolostones of the Cayman Formation (Miocene) on the Cayman Islands. On the eastern part of Grand Cayman, dolomitization that ceased by 1 million years ago created an architecture whereby the limestones in the central part of the island were surrounded by dolostones in coastal areas of the island. Since then, the upper 90 m of the Cayman Formation has been repeatedly cycled through many different marine and meteoric diagenetic zones as large, rapid eustatic oscillations in sea level affected the island. The records of these diagenetic cycles in the dolostones and limestones are, however, different and impossible to match to the cyclic changes in sea level. In the peripheral dolostones, post-dolomitization diagenetic features are sparse. In contrast, the limestones in the interior of the island exhibit a wider variety of meteoric diagenetic features, including extensive dissolution and calcite cementation. The dolostones have low porosity (< 10%) and permeability, whereas the limestones are characterized by high porosity (up to 50%), especially in the lower and middle parts of the studied limestone succession. The different phases of diagenesis found in the limestones, however, cannot be specifically matched to any sea-level fluctuations that have affected these successions. This issue is further exemplified by the fact that that the last marine transgression over the last ~ 16,000 years ago appears to have left no tangible record. The analysis of this succession clearly demonstrates that not all diagenetic regimes will be recorded in the fabrics of limestones or dolostones.

  9. Superstatistical analysis of sea-level fluctuations

    NASA Astrophysics Data System (ADS)

    Rabassa, Pau; Beck, Christian

    2015-01-01

    We perform a statistical analysis of measured time series of sea levels at various coastal locations in the UK, measured at time differences of 15 min over the past 20 years. When the astronomical tide and other deterministic components are removed from the record, a stochastic signal corresponding to the meteorological component remains, and this is well-described by a superstatistical model. We do various tests on the measured time series, and compare the data at 5 different UK locations. Overall the χ2-superstatistics is best suitable to describe the data, in particular when one looks at the dynamics of sea-level differences on short time scales.

  10. Eustatic and tectonic control of deposition of the lower and middle Pennsylvanian strata of the Central Appalachian Basin

    USGS Publications Warehouse

    Chesnut, D.R.

    1997-01-01

    . Previously, tectonic subsidence of the basin was considered to be the dominant control on deposition of the coal-bearing rocks of the basin. However, new calculations show that eustatic rates are more significant than averaged subsidence rates for the Pennsylvanian Appalachian Basin. Accordingly, sea-level changes are considered to be a dominant control on coastal sedimentation during the Pennsylvanian. However, tectonic subsidence created the accomodation space for preservation of various orders of cyclic sedimentation; the preserved order of cycles was dependent upon the rate of subsidence from basin margin to axis.

  11. Monthly variations of the Caspian sea level and solar activity.

    NASA Astrophysics Data System (ADS)

    Romanchuk, P. R.; Pasechnik, M. N.

    The connection between 11-year cycle of solar activity and the Caspian sea level is investigated. Seasonal changes of the Caspian sea level and annual variations of the sea level with variations of solar activity are studied. The results of the verifications of the sea level forecasts obtained with application of the rules discovered by the authors are given.

  12. 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

  13. Eustatic control on epicontinental basins: The example of the Stuttgart Formation in the Central European Basin (Middle Keuper, Late Triassic)

    NASA Astrophysics Data System (ADS)

    Franz, M.; Nowak, K.; Berner, U.; Heunisch, C.; Bandel, K.; Röhling, H.-G.; Wolfgramm, M.

    2014-11-01

    The deposition of the Stuttgart Formation ('Schilfsandstein'), commonly considered as a type-example of the Carnian Pluvial Event, was controlled by high frequent 4th order sequences that resulted in pre-, intra- and post-Schilfsandstein transgressions from Tethyan waters into the epicontinental Central European Basin (CEB). The pre-Schilfsandstein transgression flooded the CEB trough gates to the Southeast and resulted in a wide-spread inland sea that was characterised by increased biological productivity, predominantly oxic conditions and enabled the immigration of euryhaline marine fauna with plankton, ostracodes, fishes, bivalves and the gastropods Omphaloptychia suebica n. sp. and Settsassia stuttgartica n. sp. The rather short-term intra- and post-Schilfsandstein transgressions flooded the CEB from the Southwest and Southeast and established a shallow brackish inland sea that stretched up to North Germany. Both, the 4th and 3rd order sequences derived from the succession in the CEB correlate well with those derived from successions of Tethyan shelfs. Therefore pronounced circum-Tethyan eustatic cycles are evidenced and may have had considerable impact on prominent middle Carnian events: Reingraben turnover, Carnian Pluvial Event, Carnian Crisis and Mid Carnian Wet Intermezzo. The broad circum-Tethyan evidence of 106-year scale cycles suggests glacioeustatic sea-level changes even in the Triassic Greenhouse period.

  14. Sudden change: Climate and sea level

    SciTech Connect

    Tanner, W.F.

    1995-10-01

    Dates, magnitudes and rates of Holocene sea-level changes were reviewed at the 1995 meeting of the American Association for the Advancement of Science. Richard B. Alley (Penn. State U.) described laminae in Greenland ice cores, with details at the annual level. A major event of unknown nature occurred at roughly 8,000 B.P. Gerard Bond (Lamont-Doherty Observ., N.Y.) described sediment cores from the North Atlantic, with a major event at 8,000 B.P. Published work of K.S. Petersen (Danish Geol. Survey) from a well near Vust (Denmark) was reviewed: A rapid sea level rise (25 m), then a similar drop centered at 8,000 B.P. at 8-15 cm/yr. W.F. Tanner (Florida State U.) described the beach ridge plain in northern Denmark, where a sequence of more than 270 Holocene ridges shows the date of the big Mid-Holocene sea level change couplet, 8,000 B.P., with a magnitude of {open_quotes}more than 14 m,{close_quotes} plus smaller changes. These data showed vertical magnitudes of the larger sea level events (except the Mid-Holocene catastrophe) in the range of 1-to-5 meters. W.C. Parker (Florida State) sought possible cycles in the same sequence, but they were too poorly defined for detailed forecasts. Charles R. Bentley (U. of Wisconsin) examined the possibility of an early collapse of the West Antarctic marine ice sheet, with a sea level rise of about 5 meters, but concluded that it is unlikely.

  15. Sea Grant Education at the University Level.

    ERIC Educational Resources Information Center

    Fiske, Shirley J.

    1998-01-01

    Sea Grant's investment in university-level education shows a diversity of avenues for supporting students from experience-based internships, merit scholarships, and fellowships to team-based multidisciplinary undergraduate education. Describes such programs as Undergraduate Research Opportunities in ocean engineering, graduate research…

  16. Annotated Bibliography of Relative Sea Level Change

    DTIC Science & Technology

    1991-09-01

    Quaternary sea-level changes. Former studies of Tasmanian Quaternary shorelines assumed that stable or quasi-stable tectonic conditions prevailed (Lewis...that moved through Devils Hole-- an open fault zone at Ash Meadows, Nevada--between 50 and 310 ka (thousand years ago). The configuration of the versus

  17. Sea Level Rise National Coastal Property Model

    EPA Science Inventory

    The impact of sea level rise on coastal properties depends critically on the human response to the threat, which in turn depends on several factors, including the immediacy of the risk, the magnitude of property value at risk, options for adapting to the threat and the cost of th...

  18. Sea Level Rise National Coastal Property Model

    EPA Science Inventory

    The impact of sea level rise on coastal properties depends critically on the human response to the threat, which in turn depends on several factors, including the immediacy of the risk, the magnitude of property value at risk, options for adapting to the threat and the cost of th...

  19. Sea Grant Education at the University Level.

    ERIC Educational Resources Information Center

    Fiske, Shirley J.

    1998-01-01

    Sea Grant's investment in university-level education shows a diversity of avenues for supporting students from experience-based internships, merit scholarships, and fellowships to team-based multidisciplinary undergraduate education. Describes such programs as Undergraduate Research Opportunities in ocean engineering, graduate research…

  20. Analysis of Sea Level Rise in Action

    NASA Astrophysics Data System (ADS)

    Gill, K. M.; Huang, T.; Quach, N. T.; Boening, C.

    2016-12-01

    NASA's Sea Level Change Portal provides scientists and the general public with "one-stop" source for current sea level change information and data. Sea Level Rise research is a multidisciplinary research and in order to understand its causes, scientists must be able to access different measurements and to be able to compare them. The portal includes an interactive tool, called the Data Analysis Tool (DAT), for accessing, visualizing, and analyzing observations and models relevant to the study of Sea Level Rise. Using NEXUS, an open source, big data analytic technology developed at the Jet Propulsion Laboratory, the DAT is able provide user on-the-fly data analysis on all relevant parameters. DAT is composed of three major components: A dedicated instance of OnEarth (a WMTS service), NEXUS deep data analytic platform, and the JPL Common Mapping Client (CMC) for web browser based user interface (UI). Utilizing the global imagery, a user is capable of browsing the data in a visual manner and isolate areas of interest for further study. The interfaces "Analysis" tool provides tools for area or point selection, single and/or comparative dataset selection, and a range of options, algorithms, and plotting. This analysis component utilizes the Nexus cloud computing platform to provide on-demand processing of the data within the user-selected parameters and immediate display of the results. A RESTful web API is exposed for users comfortable with other interfaces and who may want to take advantage of the cloud computing capabilities. This talk discuss how DAT enables on-the-fly sea level research. The talk will introduce the DAT with an end-to-end tour of the tool with exploration and animating of available imagery, a demonstration of comparative analysis and plotting, and how to share and export data along with images for use in publications/presentations. The session will cover what kind of data is available, what kind of analysis is possible, and what are the outputs.

  1. Benchmarking and testing the "Sea Level Equation

    NASA Astrophysics Data System (ADS)

    Spada, G.; Barletta, V. R.; Klemann, V.; van der Wal, W.; James, T. S.; Simon, K.; Riva, R. E. M.; Martinec, Z.; Gasperini, P.; Lund, B.; Wolf, D.; Vermeersen, L. L. A.; King, M. A.

    2012-04-01

    The study of the process of Glacial Isostatic Adjustment (GIA) and of the consequent sea level variations is gaining an increasingly important role within the geophysical community. Understanding the response of the Earth to the waxing and waning ice sheets is crucial in various contexts, ranging from the interpretation of modern satellite geodetic measurements to the projections of future sea level trends in response to climate change. All the processes accompanying GIA can be described solving the so-called Sea Level Equation (SLE), an integral equation that accounts for the interactions between the ice sheets, the solid Earth, and the oceans. Modern approaches to the SLE are based on various techniques that range from purely analytical formulations to fully numerical methods. Despite various teams independently investigating GIA, we do not have a suitably large set of agreed numerical results through which the methods may be validated. Following the example of the mantle convection community and our recent successful Benchmark for Post Glacial Rebound codes (Spada et al., 2011, doi: 10.1111/j.1365-246X.2011.04952.x), here we present the results of a benchmark study of independently developed codes designed to solve the SLE. This study has taken place within a collaboration facilitated through the European Cooperation in Science and Technology (COST) Action ES0701. The tests involve predictions of past and current sea level variations, and 3D deformations of the Earth surface. In spite of the signi?cant differences in the numerical methods employed, the test computations performed so far show a satisfactory agreement between the results provided by the participants. The differences found, which can be often attributed to the different numerical algorithms employed within the community, help to constrain the intrinsic errors in model predictions. These are of fundamental importance for a correct interpretation of the geodetic variations observed today, and

  2. Late Cretaceous sea level from a paleoshoreline

    SciTech Connect

    McDonough, K.J.; Cross, T.A. )

    1991-04-10

    The contemporary elevation of a Late Cenomanian ({approx}93 Ma) shoreline was determined at five localities along the tectonically stable, eastern margin of the Cretaceous Western Interior Seaway, North America. This shoreline, represented by marine-to-nonmarine facies transitions in strata of the Greenhorn sequence (UZA-2 cycle of Haq et al. (1987)), was identified from outcrop and borehole data. Biostratigraphic zonations constrained the geologic age at each locality. Sequence stratigraphic correlations, based on identifying discrete progradational units and the surfaces that separate them, were used to refine age correlations to better than 100 kyr between localities. A single Cenomanian shoreline was correlated within a single progradational unit, and its elevation was determined at five localities. This paleostrandline occurs 265-286m above present-day sea level, at an average elevation of 276 m. Isostatic and flexural corrections were applied to remove the effects of postdepositional vertical movement, including sediment compaction by loading, uplift due to erosion, and glacial loading and rebound. Errors inherent in each measurement and each correction were estimated. Corrections and their cumulative error estimates yield a Late Cenomanian elevation of 269{plus minus}87 m above present sea level. The corrected elevation approximates sea level at 93 Ma and provides a measure of Late Cenomanian eustasy prior to the Early Turonian highstand. Establishing the absolute value for eustasy at a single point in geologic time provides a frame of reference for calibrating relative sea level curves, as well as constraining the magnitudes of tectonic subsidence, sediment flux, and other variables that controlled water depth and relative sea level.

  3. Soil Accretionary Dynamics, Sea-Level Rise and the Survival of Wetlands in Venice Lagoon: A Field and Modelling Approach

    NASA Astrophysics Data System (ADS)

    Day, J. W.; Rybczyk, J.; Scarton, F.; Rismondo, A.; Are, D.; Cecconi, G.

    1999-11-01

    Over the past century, Venice Lagoon (Italy) has experienced a high rate of wetland loss. To gain an understanding of the factors leading to this loss, from March 1993 until May 1996 the soil accretionary dynamics of these wetlands were studied. Vertical accretion, short term sedimentation, soil vertical elevation change and horizontal shoreline change were measured at several sites with varying sediment availability and wave energy. Short term sedimentation averaged 3-7 g dry m -2day -1per site with a maximum of 76 g m -2 day -1. The highest values were measured during strong pulsing events, such as storms and river floods, that mobilized and transported suspended sediments. Accretion ranged from 2-23 mm yr -1and soil elevation change ranged from -32 to 13·8 mm yr -1. The sites with highest accretion were near a river mouth and in an area where strong wave energy resuspended bottom sediments that were deposited on the marsh surface. A marsh created with dredged spoil had a high rate of elevation loss, probably due mainly to compaction. Shoreline retreat and expansion of tidal channels also occurred at several sites due to high wave energy and a greater tidal prism. The current rate of elevation gain at some sites was not sufficient to offset relative sea-level rise. The results suggest that reduction of wave energy and increasing sediment availability are needed to offset wetland loss in different areas of the lagoon. Using the data collected as part of this project, we developed a wetland elevation model designed to predict the effect of increasing rates of eustatic sea-level rise on wetland sustainability. The advantage of this model, in conjunction with measured short-term rates of soil elevation change, to determine sustainability is that the model integrates the effects of long term processes (e.g. compaction and decomposition) and takes into account feedback mechanisms that affect elevation. Specifically, changes in elevation can result in changes in

  4. Inconsistencies in sea level pressure trends between different atmospheric products. Impact on sea level trend estimation

    NASA Astrophysics Data System (ADS)

    Gomis, D.; Jordà, G.

    2012-04-01

    Long term climate datasets are of great importance to understand the processes behind climate variability, to evaluate the performance of climate models and to identify signals of climate change. Among the different atmospheric variables, sea level pressure (SLP) is the basic dynamical variable and is the most widely analyzed quantity. From the ocean perspective, SLP is of crucial importance for a dynamical interpretation of sea level records. In order to isolate the contribution to sea level variability of circulation and heat and freshwater contents, a common practice is to remove the sea level fluctuations induced by SLP. At seasonal and longer time scales, sea level is expected to react as an inverted barometer (IB) to changes in SLP. Therefore, provided that accuracy of available SLP data is high enough, the atmospheric contribution to sea level variability can be isolated and removed from sea level records. This is routinely done for tide gauge records, altimetry or sea level reconstructions. Different atmospheric gridded products spanning the last decades are nowadays available. On the one hand, there are historical SLP datasets where observations from land stations and ocean observations have been interpolated into a regular grid. On the other hand, there are reanalyses where an atmospheric model is run assimilating the historical data. Both kind of products have been extensively used in recent years either directly (i.e. to analyse the SLP evolution) or indirectly (i.e. through the removal of IB effect on sea level records). However, it is well known that the quality of those products may not be homogeneous on time. In this contribution, we compare long term SLP trends from different atmospheric products (reanalysis and gridded historical datasets), and evaluate the uncertainties introduced by them in the sea level trend estimations. The results show that discrepancies between datasets can induce an uncertainty up to 0.5 mm/yr for the period 1958-2001 on

  5. Turonian-Santonian depositional and sea level history of the Tarfaya Atlantic coastal basin, SW Morocco

    NASA Astrophysics Data System (ADS)

    Aquit, Mohamed; Kuhnt, Wolfgang; Holbourn, Ann; Hassane Chellai, El; Lees, Jacqueline A.; Kluth, Oliver; Jabour, Haddou; Delaporte, Jean-Pierre

    2013-04-01

    The Turonian to Santonian organic-rich successions deposited in the continuously subsiding Tarfaya Atlantic coastal basin (SW Morocco) allow detailed reconstruction of depositional environments and correlation to eustatic sea level changes. We present high-resolution X-ray fluorescence (XRF) scanning and natural gamma-ray (NGR) records from a newly drilled sedimentary core Tarfaya SN°2 (27° 57´ 43.1´´N, 12° 48´ 37.0´´W), which recovered a continuous sedimentary succession from a middle to outer shelf environment. In the latest Turonian, the late Coniacian, and the middle and latest Santonian, high NGR and Al with low Mn and Ca content indicate pronounced dysoxic horizons that reflect impingement of the oxygen minimum zone on the shelf during sea level highstands. In contrast, lower NGR and Al with higher Mn and Ca values indicate high detrital carbonate content and more oxic conditions related to regressive events in the late Turonian, early to middle Conacian and early Santonian. Exceptionally high sedimentation rates (>10cm/kyr) characterize the late Turonian, and spectral analyses of XRF and NGR data reveal that sedimentation was mostly controlled by obliquity and precession, suggesting an overriding glacioeustatic control. However, the response to orbital forcing weakened during the latest Turonian, when sedimentation rates declined markedly to ~2 cm/kyr. We will extend this study to three newly drilled cores nearby that recovered sediment sequences from the late Albian to late Turonian and from the late Santonian to Campanian in order to retrace the complete Late Cretaceous depositional history of the Tarfaya Basin and to develop a high-resolution carbon isotope stratigraphy allowing correlation to records from other continental margins. Key words: Late Cretaceous, Tarfaya Basin, XRF scanning, natural gamma-ray, oxygen minimum zone, sea level, orbital forcing.

  6. A NOAA/NOS Sea Level Advisory

    NASA Astrophysics Data System (ADS)

    Sweet, W.

    2011-12-01

    In order for coastal communities to realize current impacts and become resilient to future changes, sea level advisories/bulletins are necessary that systematically monitor and document non-tidal anomalies (residuals) and flood-watch (elevation) conditions. The need became apparent after an exceptional sea level anomaly along the U.S. East Coast in June - July of 2009 when higher than normal sea levels coincided with a perigean-spring tide and flooded many coastal regions. The event spurred numerous public inquiries to the National Oceanic and Atmospheric Administration's (NOAA) Center for Operational Oceanographic Products and Services (CO-OPS) from coastal communities concerned because of the lack of any coastal storm signatures normally associated with such an anomaly. A subsequent NOAA report provided insight into some of the mechanisms involved in the event and methods for tracking their reoccurrences. NOAA/CO-OPS is the U.S. authority responsible for defining sea level datums and tracking their relative changes in support of marine navigation and national and state land-use boundaries. These efforts are supported by the National Water Level Observation Network (NWLON), whose long-term and widespread observations largely define a total water level measurement impacting a coastal community. NWLON time series provide estimates of local relative sea level trends, a product increasingly utilized by various stakeholders planning for the future. NWLON data also capture significant short-term changes and conveyance of high-water variations (from surge to seasonal scale) provides invaluable insight into inundation patterns ultimately needed for a more comprehensive planning guide. A NOAA/CO-OPS Sea Level Advisory Project will enhance high-water monitoring capabilities by: - Automatically detecting sea level anomalies and flood-watch occurrences - Seasonally calibrating the anomaly thresholds to a locality in terms of flood potential - Alerting for near

  7. Geochronology and subsurface stratigraphy of Pukapuka and Rakahanga atolls, Cook Islands: Late Quaternary reef growth and sea level history

    USGS Publications Warehouse

    Gray, S.C.; Hein, J.R.; Hausmann, R.; Radtke, U.

    1992-01-01

    Eustatic sea-level cycles superposed on thermal subsidence of an atoll produce layers of high sea-level reefs separated by erosional unconformities. Coral samples from these reefs from cores drilled to 50 m beneath the lagoons of Pukapuka and Rakahanga atolls, northern Cook Islands give electron spin resonance (ESR) and U-series ages ranging from the Holocene to 600,000 yr B.P. Subgroups of these ages and the stratigraphic position of their bounding unconformities define at least 5 periods of reef growth and high sea-level (0-9000 yr B.P., 125,000-180,000 yr B.P., 180,000-230,000 yr B.P., 300,000-460,000 yr B.P., 460,000-650,000 yr B.P.). Only two ages fall within error of the last interglacial high sea-level stand (???125,000-135,000 yr B.P.). This paucity of ages may result from extensive erosion of the last intergracial reef. In addition, post-depositional isotope exchange may have altered the time ages of three coral samples to apparent ages that fall within glacial stage 6. For the record to be preserved, vertical accretion during rising sea-level must compensate for surface lowering from erosion during sea-level lowstands and subsidence of the atoll; erosion rates (6-63 cm/1000 yr) can therefore be calculated from reef accretion rates (100-400 cm/1000 yr), subsidence rates (2-6 cm/1000 yr), and the duration of island submergence (8-15% of the last 600,000 yr). The stratigraphy of coral ages indicates island subsidence rates of 4.5 ?? 2.8 cm/1000 yr for both islands. A model of reef growth and erosion based on the stratigraphy of the Cook Islands atolls suggests average subsidence and erosion rates of between 3-6 and 15-20 cm/1000 yr, respectively. ?? 1992.

  8. A 3-D coupled ice sheet - sea level model applied to Antarctica through the last 40,000 years

    NASA Astrophysics Data System (ADS)

    Pollard, D.; Gomez, N. A.; Mitrovica, J. X.

    2012-12-01

    A 3-D ice sheet-shelf model is coupled to a gravitationally self-consistent global sea-level model valid for a self-gravitating, viscoelastically deforming Earth, and applied to Antarctica through the last 40,000 years. The sea-level model simulates far-field and near-field departures in ocean depths from a simple eustatic (i.e., globally uniform) curve. The coupled model captures interactions due to the gravitational effect of varying ice mass on the proximal ocean and grounding-line depths, which is a negative feedback tending to slow down marine grounding-line retreat especially in West Antarctica. The parameterized ice-sheet forcing includes sub-ice-shelf oceanic melting based on the cavity-box model of Olbers and Hellmer (Ocean Dynamics, 2010), driven by circum-Antarctic ocean temperatures over the last 22,000 yr from the A-OGCM results of Liu et al. (Science, 2009). Northern Hemispheric ice variations required as input to the sea-level model are adopted from the ICE-5G ice sheet history (Peltier, Ann. Rev. Earth Plan. Sci., 2004). The coupled model output includes 3-D ice distributions and global maps of bedrock elevation and sea level, from 40,000 yr BP to the present. Presented results will focus on total ice volume through time, ice distributions and sea levels at the Last Glacial Maximum and present, grounding-line retreat patterns though the last deglaciation, and relative sea level curves at selected locations. Sensitivities to coupled vs. uncoupled versions, model resolution, and several other key parameters will be assessed.

  9. Ice sheet systems and sea level change.

    NASA Astrophysics Data System (ADS)

    Rignot, E. J.

    2015-12-01

    Modern views of ice sheets provided by satellites, airborne surveys, in situ data and paleoclimate records while transformative of glaciology have not fundamentally changed concerns about ice sheet stability and collapse that emerged in the 1970's. Motivated by the desire to learn more about ice sheets using new technologies, we stumbled on an unexplored field of science and witnessed surprising changes before realizing that most were coming too fast, soon and large. Ice sheets are integrant part of the Earth system; they interact vigorously with the atmosphere and the oceans, yet most of this interaction is not part of current global climate models. Since we have never witnessed the collapse of a marine ice sheet, observations and exploration remain critical sentinels. At present, these observations suggest that Antarctica and Greenland have been launched into a path of multi-meter sea level rise caused by rapid climate warming. While the current loss of ice sheet mass to the ocean remains a trickle, every mm of sea level change will take centuries of climate reversal to get back, several major marine-terminating sectors have been pushed out of equilibrium, and ice shelves are irremediably being lost. As glaciers retreat from their salty, warm, oceanic margins, they will melt away and retreat slower, but concerns remain about sea level change from vastly marine-based sectors: 2-m sea level equivalent in Greenland and 23-m in Antarctica. Significant changes affect 2/4 marine-based sectors in Greenland - Jakobshavn Isb. and the northeast stream - with Petermann Gl. not far behind. Major changes have affected the Amundsen Sea sector of West Antarctica since the 1980s. Smaller yet significant changes affect the marine-based Wilkes Land sector of East Antarctica, a reminder that not all marine-based ice is in West Antarctica. Major advances in reducing uncertainties in sea level projections will require massive, interdisciplinary efforts that are not currently in place

  10. DUACS: Toward High Resolution Sea Level Products

    NASA Astrophysics Data System (ADS)

    Faugere, Y.; Gerald, D.; Ubelmann, C.; Claire, D.; Pujol, M. I.; Antoine, D.; Desjonqueres, J. D.; Picot, N.

    2016-12-01

    The DUACS system produces, as part of the CNES/SALP project, and the Copernicus Marine Environment and Monitoring Service, high quality multimission altimetry Sea Level products for oceanographic applications, climate forecasting centers, geophysic and biology communities... These products consist in directly usable and easy to manipulate Level 3 (along-track cross-calibrated SLA) and Level 4 products (multiple sensors merged as maps or time series) and are available in global and regional version (Mediterranean Sea, Arctic, European Shelves …).The quality of the products is today limited by the altimeter technology "Low Resolution Mode" (LRM), and the lack of available observations. The launch of 2 new satellites in 2016, Jason-3 and Sentinel-3A, opens new perspectives. Using the global Synthetic Aperture Radar mode (SARM) coverage of S3A and optimizing the LRM altimeter processing (retracking, editing, ...) will allow us to fully exploit the fine-scale content of the altimetric missions. Thanks to this increase of real time altimetry observations we will also be able to improve Level-4 products by combining these new Level-3 products and new mapping methodology, such as dynamic interpolation. Finally these improvements will benefit to downstream products : geostrophic currents, Lagrangian products, eddy atlas… Overcoming all these challenges will provide major upgrades of Sea Level products to better fulfill user needs.

  11. Paleoglobal change during deposition of cyclothems: calculating the contributions of tectonic subsidence, glacial eustasy and long-term climate influences on Pennsylvanian sea-level change

    NASA Astrophysics Data System (ADS)

    Klein, George D.

    1993-07-01

    change. The remaining change in sea level is controlled by both short-term glacial eustasy (Milankovitch orbital forcing; approximately up to 70% of sea-level change in the Midcontinent) and long-term climate change (~ 15% of sea-level change in the Midcontinent). These findings suggest that away from orogenic belts, climatic change is the principal driving mechanism controlling sea level change, whereas within orogenic belts, climate becomes somewhat more subordinate as a driving mechanism for Pennsylvanian sea level change even though indicators of climatic change itself are preserved. Methods developed herein permit estimating magnitudes of both tectonic and glacio-eustatic components of sea-level change influencing Pennsylvanian cyclothem deposition, and may be applicable to other cyclic sequences.

  12. The future for the Global Sea Level Observing System (GLOSS) Sea Level Data Rescue

    NASA Astrophysics Data System (ADS)

    Bradshaw, Elizabeth; Matthews, Andrew; Rickards, Lesley; Aarup, Thorkild

    2016-04-01

    Historical sea level data are rare and unrepeatable measurements with a number of applications in climate studies (sea level rise), oceanography (ocean currents, tides, surges), geodesy (national datum), geophysics and geology (coastal land movements) and other disciplines. However, long-term time series are concentrated in the northern hemisphere and there are no records at the Permanent Service for Mean Sea Level (PSMSL) global data bank longer than 100 years in the Arctic, Africa, South America or Antarctica. Data archaeology activities will help fill in the gaps in the global dataset and improve global sea level reconstruction. The Global Sea Level Observing System (GLOSS) is an international programme conducted under the auspices of the WMO-IOC Joint Technical Commission for Oceanography and Marine Meteorology. It was set up in 1985 to collect long-term tide gauge observations and to develop systems and standards "for ocean monitoring and flood warning purposes". At the GLOSS-GE-XIV Meeting in 2015, GLOSS agreed on a number of action items to be developed in the next two years. These were: 1. To explore mareogram digitisation applications, including NUNIEAU (more information available at: http://www.mediterranee.cerema.fr/logiciel-de-numerisation-des-enregistrements-r57.html) and other recent developments in scanning/digitisation software, such as IEDRO's Weather Wizards program, to see if they could be used via a browser. 2. To publicise sea level data archaeology and rescue by: • maintaining and regularly updating the Sea Level Data Archaeology page on the GLOSS website • strengthening links to the GLOSS data centres and data rescue organisations e.g. linking to IEDRO, ACRE, RDA • restarting the sea level data rescue blog with monthly posts. 3. Investigate sources of funding for data archaeology and rescue projects. 4. Propose "Guidelines" for rescuing sea level data. These action items will aid the discovery, scanning, digitising and quality control

  13. Stratigraphic signatures of the tectonic and eustatic effects during the post-rift history of the tethyan margin in the southern Vercors (France)

    SciTech Connect

    Jacquin, T.; Magniez-Jannin, F. ); Vail, P.R. ); Arnaud, H. ); Dardeau, G. ); Graciansky, P. ); Lemoine, M. ); Marchand, D. ); Ravenne, C. )

    1990-05-01

    The stratigraphic record of the southern European peri-tethyan platforms displays numerous major transgressive/regressive facies cycles with a duration of more than 10 m.y. during Mesozoic time. In the sub-Alpine basin, southeastern France, shaly sediments dominate during transgressive phases, and calcareous sediments dominate during regressive phases. These major facies cycles relate to major tectonic events associated with the tethyan passive margin history. It appears that these major facies cycles are formed in time intervals bracketed by periods of significant increases in the rate of tectonic subsidence. They are interpreted as second-order tectonic events (the evolution of the sedimentary basin being of first order). At a smaller scale, depositional sequences with lowstand, transgressive and highstand systems tracts are recognizable within the major transgressive/regressive facies cycles. They are interpreted to be caused by third-order eustatic cycles. During periods of high rates of tectonic subsidence, the accommodation space increases on the shelf. Thick transgressive and highstand systems tracts develop. These thick shelfal sequences are characteristic of the transgressive phase of the major facies cycles. When the rate of tectonic subsidence decreases, the accommodation space on the shelf also decreases, which greatly enhances the effect of eustatic sea level falls. During the regressive phase of the major facies cycles, depositional sequences develop thick lowstand systems tracts in the basin and major subaerial exposure surfaces on the shelf.

  14. Sea level changes in the Holocene

    SciTech Connect

    Tanner, W.F. )

    1993-03-01

    Beach ridge data provide much information on the history of sea level changes through all of Holocene time. Two data sets start at about 12,000 B.P., one of them essentially continuous to now with data every 40--50 yrs. Another starting at 7,600 B.P. is continuous to the present. Others span the last 3,200 years. These records agree reasonably closely, and show the Little Ice Age (since 1,200 A.D.). The sea level changes in these data include the following: (a) Early Holocene crisis, about 8,000 B.P. The Swedish (Baltic Sea) record ends about this time, the Hudson Bay record starts at roughly this time, and the Danish record has a 300--500-year gap at about this time. From the latter, it appears that sea level rose sharply, shortly before 8,000 B.P., and fell again shortly after 8,000 B.P. These were the largest changes in Holocene time. The vertical change may have been as much as 12--18 meters, and the rate of change as much as 5--8 cm/yr, perhaps the maximum possible. In stable areas, evidence for these changes are now 25--30 meters below sea level. (b) Early Holocene general rise, up to about 8,000 B.P. Evidence for this is now known only on uplifted coasts. (c) Middle Holocene high, 2 m above present MSL 7,000--5,500 B.P. (d) Middle Holocene low, 3--4 m below present MSL 5,000--3,500 B.P. (e) Several changes up to 2 meters, especially since 3,000 B.P. In general, rates of change have been close to 1 cm/yr (major exceptions noted above). The only persistent interval was that between beach ridges; each ridge and its associated swale seem to have been built by a sea-level rise-and-fall couplet, having dimensions so small (perhaps 5--30 cm) that they could be overlooked easily on tide-gauge records. The average apparent time interval was 35--50 years.

  15. Global Mean Sea Level during 2004-2008 from Jason, GRACE, and Argo: A Discussion of Systematic Errors (Invited)

    NASA Astrophysics Data System (ADS)

    Ray, R. D.; Beckley, B. D.; Boy, J.; Jacob, S.; Lemoine, F. G.; Luthcke, S. B.; Zelensky, N. P.

    2009-12-01

    The global mean sea level curve as measured by Jason satellite altimetry represents the combined signal of steric and eustatic sea-level variations. In principle, the former can be determined by the Argo hydrographic network (excepting that part arising from the abyssal depths) and the latter by GRACE satellite gravity measurements. For the period 2004 through 2008 the consistency between these systems for both the mean sea level trend and the seasonal cycle is encouraging; see recent work by Cazenave, Leuliette, and others. Yet all three systems are susceptible to an astonishing variety of systematic errors. This paper attempts to bound a few of them. For the satellite systems (Jason and GRACE) errors in the terrestrial reference frame, including the location of the geocenter, continue to be problematic. Jason results are also affected by calibration issues, especially for the radiometer. Tide gauge comparisons are critical, but they do not completely solve calibration uncertainties. For Argo we highlight uncertainties related to (a) interpolation across empty stretches of ocean and (b) aliasing from high-wavenumber variability, but as Willis et al. have shown, instrumental calibration errors can be even more important.

  16. Consequences of sea level variability and sea level rise for Cuban territory

    NASA Astrophysics Data System (ADS)

    Hernández, M.; Martínez, C. A.; Marzo, O.

    2015-03-01

    The objective of the present paper was to determine a first approximation of coastal zone flooding by 2100, taking into account the more persistent processes of sea level variability and non-accelerated linear sea level rise estimation to assess the main impacts. The annual linear rate of mean sea level rise in the Cuban archipelago, obtained from the longest tide gauge records, has fluctuated between 0.005 cm/year at Casilda and 0.214 cm/year at Siboney. The main sea level rise effects for the Cuban coastal zone due to climate change and global warming are shown. Monthly and annual mean sea level anomalies, some of which are similar to or higher than the mean sea level rise estimated for halfway through the present century, reinforce the inland seawater penetration due to the semi-daily high tide. The combination of these different events will result in the loss of goods and services, and require expensive investments for adaption.

  17. Influence of relative sea level on a marginal sea environment and its implication for reconstructing ice volume changes using IODP Expedition 346, Site U1427

    NASA Astrophysics Data System (ADS)

    Sagawa, T.; Tada, R.; Murray, R. W.; Alvarez Zarikian, C. A.

    2014-12-01

    Pleistocene climate is characterized by glacial-interglacial changes in the ice volume. Reconstruction of ice volume is essential for understanding past climate change and is usually based on variations in the oxygen isotope composition of benthic foraminifera shells, which in turn are influenced by bottom water temperature. Another approach is to use the oxygen isotope composition of planktonic foraminifer in semi-enclosed seas, where the surface environments are sensitive to sea level change. The oceanographic condition at the sea north of Japanese islands is also largely influenced by the eustatic change. The Japanese islands and inter island shallow straits (sill depth less than 130 m) limit seawater exchange between the North Pacific and the marginal seas. The oxygen isotope record in this area show a unique feature and is a candidate for reconstructing global sea level history. During the Integrated Ocean Drilling Program (IODP) Expedition 346 "Asian Monsoon" (29 July-27 September 2013), a shallow marine sediment sequence was recovered from the slope of north coast of western Japan, Site U1427. The shipboard data highlight the sediment contains well-preserved foraminifer and has high sedimentation rate of ~40 cm/kyr. A complete splice down to ~400 m provides the potential for a continuous record for the last ~1.4 Ma. Preliminary isotope results show isotopic variations correspond to lithological change and therefore show similar variation to physical properties of the sediment, such as bulk density, natural gamma ray, and so on. The result suggests that the oxygen isotope of foraminifer in this area may provide key information on past global ice volume changes.

  18. Sea-level changes before large earthquakes

    USGS Publications Warehouse

    Wyss, M.

    1978-01-01

    Changes in sea level have long been used as a measure of local uplift and subsidence associated with large earthquakes. For instance, in 1835, the British naturalist Charles Darwin observed that sea level dropped by 2.7 meters during the large earthquake in Concepcion, CHile. From this piece of evidence and the terraces along the beach that he saw, Darwin concluded that the Andes had grown to their present height through earthquakes. Much more recently, George Plafker and James C. Savage of the U.S Geological Survey have shown, from barnacle lines, that the great 1960 Chile and the 1964 Alaska earthquakes caused several meters of vertical displacement of the shoreline. 

  19. Hurricanes, sea level rise, and coastal change

    USGS Publications Warehouse

    Sallenger,, Asbury H.; Wang, Ping; Rosati, Julie D.; Roberts, Tiffany M.

    2011-01-01

    Sixteen hurricanes have made landfall along the U.S. east and Gulf coasts over the past decade. For most of these storms, the USGS with our partners in NASA and the U.S. Army Corps of Engineers have flown before and after lidar missions to detect changes in beaches and dunes. The most dramatic changes occurred when the coasts were completely submerged in an inundation regime. Where this occurred locally, a new breach was cut, like during Hurricane Isabel in North Carolina. Where surge inundated an entire island, the sand was stripped off leaving marshy outcrops behind, like during Hurricane Katrina in Louisiana. Sea level rise together with sand starvation and repeated hurricane impacts could increase the probabilities of inundation and degrade coasts more than sea level rise alone.

  20. Coastal subsidence and relative sea level rise

    USGS Publications Warehouse

    Ingebritsen, Steven E.; Galloway, Devin L.

    2014-01-01

    Subsurface fluid-pressure declines caused by pumping of groundwater or hydrocarbons can lead to aquifer-system compaction and consequent land subsidence. This subsidence can be rapid, as much as 30 cm per year in some instances, and large, totaling more than 13 m in extreme examples. Thus anthropogenic subsidence may be the dominant contributor to relative sea-level rise in coastal environments where subsurface fluids are heavily exploited. Maximum observed rates of human-induced subsidence greatly exceed the rates of natural subsidence of unconsolidated sediments (~0.1–1 cm yr−1) and the estimated rates of ongoing global sea-level rise (~0.3 cm yr−1).

  1. Rising Sea Levels: Truth or Scare?

    ERIC Educational Resources Information Center

    Peacock, Alan

    2007-01-01

    When "ITV News" ran an item that shocked the author, about rising sea levels that will have caused the entire evacuation of the islands by the end of this year, he began to wonder whether the Pacific Ocean is really rising as fast as this. The media reporting of such things can be a double-edged sword. On the one hand, it brought to the author's…

  2. Rising Sea Levels: Truth or Scare?

    ERIC Educational Resources Information Center

    Peacock, Alan

    2007-01-01

    When "ITV News" ran an item that shocked the author, about rising sea levels that will have caused the entire evacuation of the islands by the end of this year, he began to wonder whether the Pacific Ocean is really rising as fast as this. The media reporting of such things can be a double-edged sword. On the one hand, it brought to the author's…

  3. Synsedimentary tectonics, mud-mounds and sea-level changes on a Palaeozoic carbonate platform margin: a Devonian Montagne Noire example (France)

    NASA Astrophysics Data System (ADS)

    Bourrouilh, Robert; Bourque, Pierre-André; Dansereau, Pauline; Bourrouilh-Le Jan, Françoise; Weyant, Pierre

    1998-06-01

    The Devonian sedimentary succession of the southern flank of the Montagne Noire (France) was deposited along a divergent margin. This paper is a contribution to describe and evaluate biogenic, sedimentary, geochemical and micropalaeontological features as indicators of sea-level changes and global history of the Devonian in this area. Following transgression and shallow-water environments during Early Devonian time (Lochkovian to early Emsian), biogenic mud-rich mounds with stromatactis developed during latest Emsian at the platform margin. The depth of the Devonian sea was increasing and the seafloor passed below the photic zone and the lower limit of storm wave base during the Emsian. Growth and seismic faults affected the mounds and created Neptunian cracks and crevices, quickly filled with sedimentary material (pisoids) and cements (Neptunian dykes and veins). Light and CL-microscopy, and stable isotope geochemistry show that stromatactis, cements of Neptunian dykes, veins and pisoid cortices are early marine, whereas the red finely crystalline material that forms the bulk of the mound has been cemented in the near-surface diagenetic environment, after the early marine cementation of stromatactis and Neptunian dykes and veins, by meteoric or hydrothermal fluids. The sedimentary rocks overlying the stromatactis mounds exhibit regularly condensed iron and manganese-rich layers, interrupted by the Kellwasser hypoxic horizon. These condensed deposits developed up to the Famennian in a context of carbonate gravity sedimentation and became more and more rhythmic and frequent up section. The occurrence and irregular distribution of large-scale submarine mass flows during Frasnian and Famennian times can be related to block faulting on which Lower Devonian stromatactis mounds could have been uplifted by this block faulting to form seamounts. The sea-level fluctuations detected in the southern flank of Montagne Noire are compared to the Devonian eustatic sea-level curve

  4. Late Pliocene and early Pleistocene sea-level timing and amplitudes derived from fossil ostracod assemblages: Canterbury Basin, New Zealand

    NASA Astrophysics Data System (ADS)

    Nakamura, M.; Kusunoki, S.; Yamada, K.; Hoyanagi, K.

    2013-12-01

    IODP Expedition 317 cruise drilled cores at three shelf sites (U1353, U1354 and U1351) and one slope site (U1352), in water depths between 85 and 344 m, to understand relationships between sea-level change and sequence stratigraphy. The shelf sites are well suited to reconstruction of high-resolution sea-level fluctuations because of high sedimentation rates from the uplifting Southern Alps. We examined fossil ostracod assemblages from the shelf sites to reconstruct paleo-water depth fluctuations and their amplitudes. We identified 178 ostracod species and 70 genera from more than 160 samples. Q-mode factor analysis was performed on ostracod taxa with abundances of >3.5 % in each sample containing >50 specimens. Six varimax factors were explained 70.8% of the total variance. Paleo-water depths in each factor were calibrated with reference to recent ostracodes occurring around the sites as follows: first factor, middle shelf (50-80 m); second factor, middle to outer shelf (60-130 m); third factor, middle to outer shelf (55-115 m); fourth factor, lagoon, estuary and inner shelf (0-50 m); fifth factor, middle to outer shelf (80-200 m); sixth factor, outer shelf (130-200 m). Factor analysis of ostracod assemblages reveal at least, eight transgressive- and regressive-cycles at Site U1353, seventeen at Site U1354 and two at Site U1351. These cycles probably correspond to a subset of MIS stages between MIS M2 and MIS 40. Furthermore, amplitudes of these paleo-water-depth cycles are expected to equate to eustatic amplitudes because shelf sedimentation has been continuous and minimal subsidence can have occurred during the short time period involved. We therefore estimate that eustatic amplitudes were: 10 - 30 m from 3.1 to 2.8 Ma, ca. 100 m from 2.8 to 2.6 Ma, and 30 - 115 m from 1.8 to1.2 Ma. These amplitudes, together with the timing of the increase in amplitudes (~2.7 Ma), agree with estimates derived from oxygen isotopic records (Raymo et al., 2005), suggesting that

  5. The Cenomanian/Turonian carbon burial event, Bass River, NJ, USA: Geochemical, paleoecological, and sea-level changes

    USGS Publications Warehouse

    Sugarman, P.J.; Miller, K.G.; Olsson, R.K.; Browning, J.V.; Wright, J.D.; De Romero, L. M.; White, T.S.; Muller, F.L.; Uptegrove, J.

    1999-01-01

    The Bass River borehole (ODP Leg 174AX) recovered approximately 200 ft (61 m) of upper Cenomanian to lower Turonian strata from the New Jersey Coastal Plain, USA, including the expression of a global carbon burial event. The Cenomanian/Turonian (C/T) boundary is recognized at Bass River at ???1935.5 ft (589.9 m) based on the contact of nannofossil Microstaurus chiastius and Eiffellithus eximius Subzones of the Parhabdolithus asper Zone. Carbon isotopic records of both Gavelinella and Epistomina show a large (>2???) increase immediately below the C/T boundary, with maximum values of 6??? in Epistomina and 4.3??? in Gavelinella. The ??13C offset between these taxa is constant and we conclude that Epistomina, like Gavelinella, faithfully records seawater ??13C changes. Above the sharp ??13C increase, elevated ??13C and sedimentary organic carbon (>0.9%) values continue into the lower Turonian, culminating in a sharp ??13C decrease. High ??13C values in the uppermost Cenomanian-lower Turonian at Bass River correlate with a global carbon burial event recorded in Europe and the U.S. Western Interior; we estimate the duration of this event at Bass River as 400-500 k.y. Although the carbon burial event occurred during a long-term eustatic rise (10 m.y. scale), it occurs within a 1-2 m.y. long sequence at Bass River that indicates no relationship with sea-level lowering on the m.y. scale. The carbon burial event does not appear to be associated with maximum flooding either, indicating little correlation with sea-level rise on a m.y. scale. Within the sequence spanning the carbon event, there are at least 4 shallowing-upward parasequences (durations ???350-460 k.y.) indicated by changes in abundance and type of Epistomina species, ??18O variations, and minor lithologic variations. The highest occurrences of 6 Epistomina species and the origination of Epistomina sliteri Olsson n. sp. are associated with the parasequences and possibly with higher ??18O values. There is no

  6. Assessment of the sensitivity of the southern coast of the Gulf of Corinth (Peloponnese, Greece) to sea-level rise

    NASA Astrophysics Data System (ADS)

    Karymbalis, Efthimios; Chalkias, Christos; Chalkias, George; Grigoropoulou, Eleni; Manthos, George; Ferentinou, Maria

    2012-12-01

    The eustatic sea-level rise due to global warming is predicted to reach approximately 18-59 cm by the year 2100, which necessitates the identification and protection of sensitive sections of coastline. In this study, the classification of the southern coast of the Gulf of Corinth according to the sensitivity to the anticipated future sealevel rise is attempted by applying the Coastal Sensitivity Index (CSI), with variable ranges specifically modified for the coastal environment of Greece, utilizing GIS technology. The studied coastline has a length of 148 km and is oriented along the WNW-ESE direction. CSI calculation involves the relation of the following physical variables, associated with the sensitivity to long-term sea-level rise, in a quantifiable manner: geomorphology, coastal slope, relative sea-level rise rate, shoreline erosion or accretion rate, mean tidal range and mean wave height. For each variable, a relative risk value is assigned according to the potential magnitude of its contribution to physical changes on the coast as the sea-level rises. Every section of the coastline is assigned a risk ranking based on each variable, and the CSI is calculated as the square root of the product of the ranked variables divided by the total number of variables. Subsequently, a CSI map is produced for the studied coastline. This map showed that an extensive length of the coast (57.0 km, corresponding to 38.7% of the entire coastline) is characterized as highly and very highly sensitive primarily due to the low topography, the presence of erosionsusceptible geological formations and landforms and fast relative sea-level rise rates. Areas of high and very high CSI values host socio-economically important land uses and activities.

  7. Global increasing of mean sea level and erroneous treatment of a role of thermal factors

    NASA Astrophysics Data System (ADS)

    Barkin, Yu. V.

    2009-04-01

    Satellite methods of studies of the ocean surface - methods of altimetry - have been obtained intensive development in the last decades (since 1993). However, altimetry studies with the help of special satellites such as TOPEX-Poseidon not only have not cleared up understanding of the phenomenon of increase of sea level (SLR), but have even more confused and without that a complex question on the reasons of increase of sea level. Appeared, that classical determinations of average velocity of increase of sea level on coastal observations (1.4-1.7 mm / yr) approximately for 0.8-1.0 mm / yr it is less, rather than by modern satellite determinations of satellites TOPEX - Poseidon etc. (2.5 - 2.8 mm / yr). On the basis of the data of altimetry observations of TOPEX-Poseidon and Jason for the period 1993-2003 for geocentric velocity of increase of sea level (of global ocean) the value 2.8+/-0.4 mm / yr [1] has been obtained. In the given report the full answer is actually is given to a question put by leading experts on research of the sea level: "The TOPEX/Poseidon and Jason satellite altimeter missions provided a 12 year record of sea level change, which show increase of global mean sea level of 2.8+/-0.4 mm/yr, with considerable geographic variation. An important question for climate studies is to determine the cause of this change - specifically how much of the change is due to steric (heating) versus eustatic (runoff, melting ice, etc.) contribution?" [1]. There is, a big value of average velocity of increase of the sea level on the satellite data, it is possible to explain only by kinematical effect in data of observations. The motion of the satellite "is concerned" to the centre of mass of our planet, and its position is determined by a geocentric radius - vector. Therefore northern drift of the centre of mass in the Earth body [2] as though results in reduction of distances from the satellite up to the sea surface in the southern hemisphere and to their reduction

  8. 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.

  9. Challenges of Holocene sea-level reconstructions in area of low uplift rate

    NASA Astrophysics Data System (ADS)

    Grudzinska, Ieva; Vassiljev, Jüri; Stivrins, Normunds

    2017-04-01

    Isolated coastal water bodies provide an excellent sedimentary archive of the evolutionary stages of the coastal regions. It is relatively easy to determine lake isolation threshold, time and contact, where marine and brackish diatoms are replaced by halophilous and subsequently by freshwater diatoms, in areas with high land uplift rates and hard bedrock. Whereas, in areas where the land uplift rate is near zero and sedimentary cover of sand, silt and/or clay exists, determination of the lake isolation threshold and time is a rather complicated task. Such an area is the coast of the Gulf of Riga, where the apparent land uplift is about 1 mm yr-1 in the northern part and near zero in the southern part of the area. The aim of the study is to improve the understanding of the nature and extent of the Holocene sea level changes in the eastern Baltic Sea region, in the area with low land uplift rate. This study marks the first attempt to reconstruct sea level changes for a wide variety of settings based on high-resolution bio-, litho-, and chronostratigraphical evidence from sediment records of isolation basins in Latvia. In total, eight lakes were studied in order to revise the relative sea level (RSL) changes at the southern coast of the Gulf of Riga based on new litho- and biostratigraphical data and radiocarbon datings. The palaeogeographical reconstruction was challenging because we had to take into account that the process of isolation was influenced by various factors, such as gradual eustatic sea level (ESL) rise, river delta infilling by sediments and long-shore sediment transport. The water level in the Baltic Sea basin until 8,500 cal BP was influenced primarily by deglaciation dynamics, whereas in the last 8,500 years, the main factor was complicated interplay between the ESL rise and the land uplift rate. According to diatom composition and radiocarbon dates, the Litorina Sea transgression was a long-lasting event (ca. 2,200 years) in the southern part of

  10. 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.

  11. Mid Pliocene sea levels: A combined analysis of field data, models of glacial isostasy and dynamic topography, and eustasy. (Invited)

    NASA Astrophysics Data System (ADS)

    Rovere, A.; Raymo, M. E.; Hearty, P. J.; Austermann, J.; Mitrovica, J. X.; Michael, O.; Moucha, R.; Forte, A. M.; Rowley, D. B.

    2013-12-01

    Determining the eustatic elevation of former sea levels (SL), or equivalently ice volumes, is a central goal of paleoclimate research. SL estimates for the Mid-Pliocene warm period (MPWP, ˜3.3 to 2.9 Ma) are of particular interest as CO2 levels at that time (between 350 and 450 ppmv) were similar to today (> 400 ppmv as of May 2013). However, despite general agreement on other climate variables, SL estimates for the MPWP and the stability of polar ice sheets during this interval remain largely unconstrained. In this regard, inferring ice volumes from SL indicators of MPWP age is complicated by several factors. First, relatively few robust records of MPWP SL have been obtained from tectonically stable areas. Second, the potentially significant contaminating signals due to glacial isostatic adjustment (GIA) and dynamic topography associated with mantle convective flow (DT) have rarely, and only recently, been accounted for. Within the framework of PLIOMAX project, we are collecting accurate MPWP indicators at widely distributed sites using a combination of classic field methods, state of the art GPS and GIS techniques. Moreover, the analysis of the data involves the participation of both field geologists and geodynamic modelers. In this talk, we present data collected in three specific areas: Republic of South Africa, Western Australia and the southeastern United States. We will report on the present day elevation of MPWP shoreline indicators in each region. Moreover, we will combine this data set with a broad suite of numerical models of GIA and DT to establish current uncertainties on the estimate of eustatic SL during the MPWP, as well as comment on possible strategies for improving the accuracy of this estimate.

  12. Sea level forecasts using neural networks

    NASA Astrophysics Data System (ADS)

    Röske, Frank

    1997-03-01

    In this paper, a new method for predicting the sea level employing a neural network approach is introduced. It was designed to improve the prediction of the sea level along the German North Sea Coast under standard conditions. The sea level at any given time depends upon the tides as well as meteorological and oceanographic factors, such as the winds and external surges induced by air pressure. Since tidal predictions are already sufficiently accurate, they have been subtracted from the observed sea levels. The differences will be predicted up to 18 hours in advance. In this paper, the differences are called anomalies. The prediction of the sea level each hour is distinguished from its predictions at the times of high and low tide. For this study, Cuxhaven was selected as a reference site. The predictions made using neural networks were compared for accuracy with the prognoses prepared using six models: two hydrodynamic models, a statistical model, a nearest neighbor model, which is based on analogies, the persistence model, and the verbal forecasts that are broadcast and kept on record by the Sea Level Forecast Service of the Federal Maritime and Hydrography Agency (BSH) in Hamburg. Predictions were calculated for the year 1993 and compared with the actual levels measured. Artificial neural networks are capable of learning. By applying them to the prediction of sea levels, learning from past events has been attempted. It was also attempted to make the experiences of expert forecasters objective. Instead of using the wide-spread back-propagation networks, the self-organizing feature map of Kohonen, or “Kohonen network”, was applied. The fundamental principle of this network is the transformation of the signal similarity into the neighborhood of the neurons while preserving the topology of the signal space. The self-organization procedure of Kohonen networks can be visualized. To make predictions, these networks have been subdivided into a part describing the

  13. Eustatic curve for the middle Jurassic-Cretaceous based on Russian platform and Siberian stratigraphy: Zonal resolution

    SciTech Connect

    Sahagian, D.; Pinous, O.; Olferiev, A.; Zakharov, V.

    1996-09-01

    We have used the stratigraphy of the central part of the Russian platform and surrounding regions to construct a calibrated eustatic curve for the Bajocian through the Santonian. The study area is centrally located in the large Eurasian continental craton, and was covered by shallow seas during much of the Jurassic and Cretaceous. The geographic setting was a very low-gradient ramp that was repeatedly flooded and exposed. Analysis of stratal geometry of the region suggests tectonic stability throughout most of Mesozoic marine deposition. The paleogeography of the region led to extremely low rates of sediment influx. As a result, accommodation potential was limited and is interpreted to have been determined primarily by eustatic variations. The central part of the Russian platform thus provides a useful frame of reference for the quantification of eustatic variations throughout the Jurassic and Cretaceous. The biostratigraphy of the Russian platform provides the basis for reliably determining age and eustatic events. The Mesozoic section of the central part of the Russian platform is characterized by numerous hiatuses. In this study, we filled the sediment gaps left by unconformities in the central part of the Russian platform with data from stratigraphic information from the more continuous stratigraphy of the neighboring subsiding regions, such as northern Siberia. Although these sections reflect subsidence, the time scale of variations in subsidence rate is probably long relative to the duration of the stratigraphic gaps to be filled, so the subsidence rate can be calculated and filtered from the stratigraphic data. We thus have compiled a more complete eustatic curve than would be possible on the basis of Russian platform stratigraphy alone.

  14. Sea-level and climate forcing of the Sr isotope composition of marginal basins in the late Miocene Mediterranean Basin

    NASA Astrophysics Data System (ADS)

    Schildgen, T. F.; Cosentino, D.; Frijia, G.; Castorina, F.; Dudas, F. O.; Iadanza, A.; Cipollari, P.; Caruso, A.; Bowring, S. A.; Strecker, M. R.

    2013-12-01

    Sr isotope records from marginal marine basins track the mixing between sea water and local continental runoff. Because changes in sea level determine the amount of mixing between global marine and continental water, and climate affects the amount of continental runoff, both sea-level and climate changes can potentially be recorded in marine fossil Sr isotope composition. Our 128 new 87Sr/86Sr analyses on 73 oyster, foraminifera, and coral samples from eight late Miocene stratigraphic sections in southern Turkey, Crete, and Sicily show that 87Sr/86Sr in Mediterranean marginal basins started to depart from global ocean values several million years before the Messinian Salinity Crisis (MSC), with sub-basin 87Sr/86Sr commonly dropping 0.000100 below contemporaneous global ocean values. The marked departure coincided with tectonic uplift and basin shallowing along the margins of the Mediterranean Basin. In contrast, centrally-located basins within the Mediterranean (e.g., Cyprus, Sicily, Crete) only record departures during the MSC. Besides this general trend, our 57 new 87Sr/86Sr analyses from the astronomically tuned Lower Evaporite unit deposited during the MSC in the central Apennines (Italy) allow us to explore in detail the effect of sea-level and humidity changes on 87Sr/86Sr . Most of the variation in 87Sr/86Sr that we observe can be explained by changes in eustatic sea level, with greatest departures from global ocean values (with differences up to 0.000150) occurring during sea-level lowstands, which were characterized by relatively arid conditions in the Mediterranean. However, in a few cases, the greatest 87Sr/86Sr departures (up to 0.000300) occur during sea-level highstands, which are marked by more humid conditions. Because the correlations between peaks in Sr departures and highstands (humid conditions) occur only after episodes of prolonged aridity, variations of residence time of continental water (particularly groundwater) could have affected its Sr

  15. MIS 5e sea level: up to what point can we use literature reviews to answer the most pressing questions on the Last Interglacial ice sheets?

    NASA Astrophysics Data System (ADS)

    Rovere, A.; Raymo, M. E.

    2014-12-01

    During MIS 5e (between ~128 and 116 kyr BP) greenhouse gas concentrations were comparable to pre-industrial levels, summer insolation was higher by ~10% at high latitudes and polar temperatures in both hemispheres were about 3-5 °C warmer than today. Sea level (SL) at this time has been a subject of numerous studies (and some debate) with ~1000 sites with MIS 5e sea level markers recognized worldwide. Recently, Kopp et al. (Nature, 2009) and Dutton & Lambeck (Science, 2012) analyzed worldwide datasets of sea level markers pertaining to the last interglacial. After accounting for GIA, they reached similar conclusions that eustatic (i.e., globally averaged) sea level (ESL) was between +5 and +9.4 m above modern during MIS 5e. Furthermore, Kopp et al. (Nature, 2009; GJI, 2013) suggest that sea level was not uniform during the LIG, but instead underwent at least two rapid oscillations including a rapid late 5e rise first proposed by Hearty et al. (QSR, 2007) and later by O'Leary et al. (Nat. Geo., 2013). Investigating the temporal and geographic variability of MIS 5e sea level opens new lines of research, in particular the possibility to fingerprint (Hay et al., QSR, 2014) the source of the proposed rapid ice sheet collapse near the end of the Last Interglacial. In this presentation we ask: can we use a database of published sea level estimates for this purpose? To answer this question, we built a relative sea level (RSL) database using RSLcalc 2.0; this is a relational database specifically designed to review relative sea level data points while keeping all the relevant information contained in the original publications. RSlcalc allows to estimate the measurement error (on the actual elevation of the SL feature), the error on the indicative range (the elevation range occupied by a sea level indicator) as well as the reference water level (the relationship between the marker and the former sea level). We show that the majority of published data have an accuracy of few

  16. Past Sea Level Reconstruction and Variability of Sea Level Trend Patterns over 1958-2005 in the Mediterranean Sea basin

    NASA Astrophysics Data System (ADS)

    Meyssignac, B.; Cazenave, A. A.; Morrow, R. A.; Llovel, W.; Maisongrande, P.; Fenoglio-Marc, L.

    2009-12-01

    For the past decades, there are no direct basin-scale observations informing on the spatial trend patterns in Mediterranean sea level. Yet it is important to know the dominant modes of regional variability on interannual/decadal/multidecadal time scale in the Mediterranean basin and their driving mechanisms. For that purpose, we have developed a reconstruction method of past Mediterranean sea level (since 1958) that combines long tide gauge records of limited coverage and 2-D sea level patterns based on runs from two different Ocean General Circulation Models (OGCMs). Instead of using 2-D spatial patterns from satellite altimetry (as done in previous studies; e.g., Calafat et al., 2009), here we prefer to use OGCM runs on the past few decades on the assumption that they better capture the decadal variability of the spatial trend patterns. The two OGCMs considered are the ORCA05 run (without data assimilation) over 1958-2005 available from the DRAKKAR project and the SODA reanalyse over 1958-2005 available from GODAE (Carton et al., 2008), assimilating all available in situ temperature, salinity and sea level data. The two sea level reconstructions are compared to each other as well as with previous studies (e.g., Calafat et al., 2009). The dominant modes of temporal variability are discussed and sea level hindcasts at tide gauge sites not used in the analysis are compared to actual observations. Comparisons with steric sea level patterns based on in situ hydrographic data are also presented and discussed with regard to the conclusions of past studies based on tide gauge records analysis.

  17. The influence of sea-level changes on tropical coastal lowlands; the Pleistocene Coropina Formation, Suriname

    NASA Astrophysics Data System (ADS)

    Wong, Th. E.; de Kramer, R.; de Boer, P. L.; Langereis, C.; Sew-A-Tjon, J.

    2009-04-01

    The Pleistocene Coropina Formation largely constitutes the Old Coastal Plain of Suriname. It is exposed fully only in open-pit bauxite mines in the central coastal plain as part of the unconsolidated overburden of Paleocene-Eocene bauxites. This study deals with the stratigraphy, sedimentology and chronology of this formation, and is based on a study in the recently closed Lelydorp-III bauxite mine operated by N.V. BHP Billiton Maatschappij Suriname. The Coropina Formation consists of the Para and Lelydorp Members. We present a detailed lithological subdivision of these members. In the Para Member, four units are discerned which are grouped in two transgressive cycles, both ranging upward from terrestrial towards chenier and coastal mudflat deposits reflecting glacio-eustatic sea-level changes. The sandy sediments represent fluviatile and beach-bar (chenier) deposits, and were supplied by rivers from the Precambrian basement and to a lesser extent by westward longshore coastal drift. Clays, largely derived from the Amazon River and transported alongshore over the shelf, were deposited in extensive coastal mudflats. The Lelydorp Member, also comprising four units, represents a depositional system that is closely comparable to the recent Suriname coastal setting, i.e., a lateral and vertical alternation of mudflat and chenier deposits formed over a period characterised by more or less constant sea level. Palaeomagnetic data indicate a dominantly reversed magnetic polarity in the Para Member, whereas the Lelydorp Member shows a normal magnetic polarity with a minor reversed polarity overprint. The reversed polarities of the Para Member exclude a Brunhes Chron (0.78-0.0 Ma) age, and thus assign it to the Matuyama Chron (2.58-0.78 Ma). This implies that the Coropina Formation is much older than hitherto assumed, and that one or more (long-term) hiatuses are not recognizable in the lithological succession.

  18. Sea-level transitioning dual bell nozzles

    NASA Astrophysics Data System (ADS)

    Stark, Ralf; Génin, Chloé

    2017-09-01

    A detailed study was conducted to evaluate the impact of sea-level transitioning dual bell nozzles on the payload mass delivered into geostationary transfer orbit by Ariane 5 ECA. For this purpose, a multitude of Vulcain 2 and Vulcain 2.1 nozzle extension contours were designed. The two variable parameters were the position of the wall inflection and the constant wall pressure of the nozzle extension. Accounting for the two variable parameters, an approved analytical method was applied to predict the impact of the dual bell nozzles on the payload mass.

  19. Mid-Cenomanian Event I (MCE I, 96 Ma): elemental and osmium isotope evidence for sea level, climate, and palaeocirculation changes in the NW European epicontinental sea

    NASA Astrophysics Data System (ADS)

    Jarvis, Ian; Roest-Ellis, Sascha; Selby, David

    2017-04-01

    Cenomanian times (100.5-93.9 Ma) represent perhaps the best documented episode of eustatic rise in sea level in Earth history and the beginning of the Late Mesozoic thermal maximum, driving global expansion of epicontinental seas and the onset of widespread pelagic and hemipelagic carbonate (chalk) deposition. Significant changes occurred in global stable-isotope records, including two prominent perturbations of the carbon cycle -Mid-Cenomanian Event I (MCEI; 96.5-96.2 Ma) and Oceanic Anoxic Event 2 (OAE2; 94.5-93.8 Ma). OAE2 was marked by the widespread deposition of black shales in the deep ocean and epicontinental seas, and a global positive carbon stable-isotope excursion of 2.0 - 2.5‰ δ13C in marine carbonates. Osmium isotopes and other geochemical data indicate that OAE2 was associated with a major pulse of LIP-associated volcanism, with coincident changes in eustatic sea level, rising atmospheric pCO2 and warming climate, but including a transient phase of global cooling - the Plenus Cold Event. MCEI, by contrast, shows a <1‰ δ13Ccarb excursion, and has no associated black shales in most areas, yet it also displays evidence of two episodes of cooling, comparable to the Plenus Cold Event. MCEI marks a major breakpoint on long-term carbon-isotope profiles, from relatively constant to very slowly rising δ13C values through the Lower Cenomanian, to a trend of generally increasing δ13C values through the Middle and Upper Cenomanian. This represents a significant long-term change in the global carbon cycle starting with MCEI. Here, we present new high-resolution major- (Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K, P) and trace-element (Ba, Cr, Re, Os, Sr, Zr) data and 187Os/188Os isotope results for MCEI from an English Chalk reference section at Folkestone. Our results are compared to published δ13Ccarb, δ18Ocarb, δ13Corg stable isotope and neodymium isotope ɛNd(t) data from the same section. Elemental proxies (Mn, Ti/Al, Zr/Al, Si/Al) define key sequence

  20. Eustatic and tectonic effects in sequences stratigraphy of the paralic-shelfal marine section, upper cretaceous, Alabama

    SciTech Connect

    King, D.T. Jr. )

    1993-09-01

    In Alabama, sequence stratigraphic facies relations within the late Santonian to latest Maastrichtian (85-67 Ma) marine section have been strongly influenced by second-, third-, and fourth-order sea level changes related both to global eustasy and regional tectonics. Through detailed lithostratigraphic and biochronostratigraphic correlations, one can delineate the dictating mechanism (eustasy versus tectonics). In the outcrop region, the marine section is 450 m thick and is comprised to paralic and shelfal facies turn, make up the 13 genetic packages (i.e., stratigraphic sequences) of the total marine section. Second-order eustatic oscillations of 3.5-5.0-m.y. duration dictated the paleogeographic (depositional) strike and the characteristics of lateral and vertical facies relations along paleogeographic strike. Third-order sea level oscillations (0.5-3.5 m.y.) are related to either eustasy or regional tectonics. Oscillations driven by eustasy produced stratigraphic breaks with appreciable relief, significant regional paleogeographic reorganizations, increased lateral and vertical facies entropy, and notable faunal changes. Stratigraphy of tectonically induced third-order oscillations generally lacks most or all of these features. Fourth-order sea level oscillations (less than 0.5 m.y.) are related most closely to minor regional tectonic adjustments coeval with the onset of episodic, Farallon-North American plate interactions. the episodic (rather than periodic) nature of fourth-order shelfal parasequences in the area, their fining-upward textural signature, characteristic transitional benthic-to-pelagic fossil record, and stratigraphic correlations with thin, prograding clastic tongues (paralic facies) collectively demonstrate a non-Milankovitch origin of the shelfal parasequences.

  1. Regional, holocene records of the human dimension of global change: sea-level and land-use change in prehistoric Mexico

    NASA Astrophysics Data System (ADS)

    Sluyter, Andrew

    1997-02-01

    Regional, Holocene records hold particular relevance for understanding the reciprocal nature of global environmental change and one of its major human dimensions: "sustainable agriculture", i.e., food production strategies which entail fewer causes of and are less susceptible to environmental change. In an epoch of accelerating anthropogenic transformation, those records reveal the protracted regional causes and consequences of change (often agricultural) in the global system as well as informing models of prehistoric, intensive agriculture which, because of long tenures and high productivities, suggest strategies for sustainable agricultural in the present. This study employs physiographic analysis and the palynological, geochemical record from cores of basin fill to understand the reciprocal relation between environmental and land-use change in the Gulf of Mexico tropical lowland, focusing on a coastal basin sensitive to sea-level change and containing vestiges of prehistoric settlement and wetland agriculture. Fossil pollen reveals that the debut of maize cultivation in the Laguna Catarina watershed dates to ca. 4100 BC, predating the earliest evidence for that cultivar anywhere else in the lowlands of Middle America. Such an early date for a cultivar so central to Neotropical agroecology and environmental change, suggests the urgency of further research in the study region. Moreover, the longest period of continuous agriculture in the basin lasted nearly three millennia (ca. 2400 BC-AD 550) despite eustatic sea-level rise. Geochemical fluxes reveal the reciprocity between land-use and environmental change: slope destabilization, basin aggradation, and eutrophication. The consequent theoretical implications pertain to both applied and basic research. Redeploying ancient agroecologies in dynamic environments necessitates reconstructing the changing operational contexts of putative high productivity and sustainability. Adjusting land use in the face of global

  2. Holocene sea-level changes in King George Island, West Antarctica, by virtue of geomorphological coastal evidences and diatom assemblages of sediment sections.

    NASA Astrophysics Data System (ADS)

    Poleshchuk, Ksenia; Verkulich, Sergey; Pushina, Zina; Jozhikov, Ilya

    2015-04-01

    A new curve of relative sea-level change is presented for the Fildes peninsula, King George Island, West Antarctic. This work is based on renewed paleogeography data, including coastal geomorphological evidence, diatom assemblages of lakes bottom sediments and radiocarbon datings of organics. The new data were obtained in several sections of quaternary sediments and groups of terraces, and allows us to expand and improve relevant conception about relative sea level changes in the King George Island region. The new radiocarbon datings of organics (mosses and shells) allows reconstructing Holocene conditions that maintain and cause the sea-level changes. Sea diatom assemblages of Dlinnoye lake bottom sediment core (that complies period about 8000 years B.P.) mark altitude of marine water penetrated into the lake. The altitudes of shell remains, which have certain life habits and expect specific salinity and depth conditions, coupled with their absolute datings, indicate the probable elevation of the past sea level. The Mid-Holocene marine transgression reached its maximum level of 18-20 m by 5760 years B.P. The transgression influenced the deglaciation of the Fildes peninsula and environment conditions integrally. The ratio of glacio-isostatic adjustment velocity and Holocene transgression leaded to the decrease of relative sea level during the Late Holocene excluding the short period of rising between 2000 and 1300 years B.P. Comparing this data with the curve for Bunger oasis, East Antarctica, introduced earlier gives an interesting result. Despite the maximum altitudes of relative sea-level rise in King George region were higher and occurred later than in Bunger oasis region, the short-term period of Late Holocene sea-level rising contemporizes. Besides that, this work allow to realize a correlation between regions of Antarctica and adjacent territory. That, in turn, lets answer the question of tectonic and eustatic factors ratio and their contribution to the

  3. Towards data-driven regional sea level projections

    NASA Astrophysics Data System (ADS)

    Larson, J.; Nerem, R. S.; Landerer, F. W.; Hamlington, B.

    2016-12-01

    Sea level change will be one of the greatest environmental challenges facing society in the coming century. Projecting future regional sea level change remains a challenge due to the underlying complexity of the Earth system. The standard method for projecting sea level relies on physics-based, global climate models. While these models are robust, they fail to account for processes and feedbacks that we do not yet fully understand, such as ocean-driven mass loss at ice sheet margins. To account for uncertainty in the underlying physics of the climate system, an alternative, observation-driven modeling approach can be taken. One increasingly popular observation driven model, referred to as the semi-empirical method, combines statistical relationships between past climate observations with physical constraints to understand how sea level has responded to global temperature in the past. This knowledge can then be combined with global temperature projections to forecast sea level forward in time. The semi-empirical method has been successfully applied to global mean sea level but has never been used to project regional sea level change, which can differ significantly from the global average. However, a regional approach requires developing separate semi-empirical models for each component of sea level change. Here we use historic sea level data and sea level fingerprint models to push the semi-empirical method into the regional domain to better project sea level along the coasts.

  4. Intraplate stresses and continental margin stratigraphy: New constraints on the relative contributions of tectonics and eustasy to the record of sea level changes

    SciTech Connect

    Cloetingh, S.; Kool, H. )

    1990-05-01

    Recent advances in modeling the tectonics of intraplate regions have established a causal relation between changes in plate-tectonic regimes and short-term changes in the orientation and magnitude of stress fields in the lithosphere. These temporal changes in stress produce vertical motions of the crust with a rate and magnitude consistent with magnitudes inferred from records of (apparent) sea level changes. Stress-induced vertical motions of the lithosphere could provide a tectonic explanation of short-term changes in sea level, such as the second-order and third-order Exxon cycles. The sea level record can be used as an independent source of information for the analysis of paleostress fields in the plates. Geodynamic modeling studies were conducted, therefore, to discriminate the relative contributions of tectonics and glacio-eustasy to the apparent sea level record and to discriminate global vs. regional tectonic components in the sea level record. Modeling strongly suggests that even in a passive margin tectonic setting, the effects of tectonics generally overwhelm eustatic contributions to the sea level record. The studies also show a close correlation between changes in intraplate-tectonic regimes in the North Atlantic caused in plate kinematics and plate interactions and the timing of changes in sea level shown in global Exxon charts. These results suggest that the charts, which are based primarily on data from the northern/central Atlantic and the North Sea reflect to a large extent the plate-tectonic evolution of this area. Apart from emphasizing the need to develop further rigorous stratigraphic criteria to separate of tectonics and eustasy on an intrabasinal scale, the studies emphasize the need to test the Vail concept in areas outside the North Atlantic. For this purpose, stratigraphic modeling for continental margins of other ocean basins based on recent ODP (Ocean Drilling Program).

  5. Late Glacial to Holocene evolution and sea-level history of Gulf of Gemlik, Sea of Marmara, Turkey

    NASA Astrophysics Data System (ADS)

    Sabuncu, Asen; Kadir Eriş, K.; Kaslilar, Ayse; Namık Çaǧatay, M.; Gasperini, Luca; Filikçi, Betül

    2016-04-01

    The Gulf of Gemlik is an E-W elongated trans-tensional basin with a maximum depth of 113 m, located on the middle strand of the North Anatolian Fault (NAF) in the south eastern part of the Sea of Marmara (SoM). While during the Holocene the sea level in the Gulf of Gemlik changed in tandem with the water level changes in the SoM, it may have been different in the late glacial when the Sea of Marmara was lacustrine. Beside the tectonic activity related to the NAFZ, eustatic sea level changes would have controlled the basin evolution and consequent sedimentary history during the different paleocanographic phases of the SoM. Considering the limited studies on the late glacial-Holocene stratigraph of the Gulf of Gemlik, this study aims to investigate the depositional units and their environments with respect to different allogenic and autogenic controls. For these purposes, we analyzed over 300 2 - 7 kHz bandwidth high-resolution gridded seismic sub-bottom CHIRP profiles together with 70 kHz high resolution multibeam bathymetry with backscatter data. Four seismic stratigraphic units were defined and correlated with chronstratigraphic units in five piston cores covering the last 15.8 ka BP according to radiocarbon ages (14C). The depth-scale accuracy of chronostratigraphic units in cores is of key importance for the precise calculation of sedimentation rates. Correlation between the seismic profiles and cores were made by matching Multi-Sensor Core-Logger (MSCL) data and seismic reflection coefficients and amplitudes for different stratigraphic units. The impedance data derived from the logger were used to generate a synthetic seismogram. We used an approach to display, estimate, and correct the depth-scale discrepancies due to oversampling affecting the upper part of sedimentary series during piston coring. The method is based on the resynchronization of synthetic seismograms computed from high-quality physical property logs to the corresponding CHIRP profiles. Each

  6. Holocene Sea-Level Rise in New Jersey and W. North Atlantic Reefs: Untangling Natural and Anthropogenic Effects

    NASA Astrophysics Data System (ADS)

    Stanley, A. M.; Miller, K. G.; Sugarman, P. J.; Browning, J. V.

    2004-12-01

    The history of pre-anthropogenic Holocene global sea level has not been well constrained. We provide Holocene sea-level estimates for five new boreholes on the New Jersey (NJ) coast (Rainbow Island, Great Bay I, Great Bay II, Cape May, and Island Beach). We analyzed facies, radiocarbon dated marsh deposits, and derived a sea-level record by compiling new and previously published NJ data. Our sea-level record shows a constant rise of ˜2 mm/yr from ˜7000 yrBP to present. This contrasts sharply with previous NJ estimates that suggested a slowing in rise since 2000 yrBP. Comparison with other NJ locations suggests surprising uniformity in the rate of rise amongst sites as far flung as Cape May and Cheesequake (200 km apart), suggesting a far-field response to the Laurentide ice sheet. The "Barbados/western North Atlantic reefs sea-level" record shows a major decrease in the rate of rise from 12 mm/yr to ˜2 mm/yr between 7000 and 8000 yrBP. Data from NJ and western North Atlantic reefs indicate a constant rate of rise of ˜2 mm/yr since ˜7000 yrBP. This suggests a background, pre-anthropogenic sea-level rise of 2 mm/yr for the entire east coast of the U.S. This background includes both the global (water volume) rise and far-field geoidal subsidence due to removal of the Laurentide ice sheet and water loading (estimated as 1 mm/yr in the modern). Applying the modern subsidence rate to the Holocene suggests a eustatic rise of ˜1 mm/yr since 7000 yrBP. Based on tide gauge data, regional sea-level rise averaged 3 mm/yr from 1900-1995, with higher rates (4 mm/yr) locally due to compaction and groundwater withdrawal. We conclude that the anthropogenically induced rise in sea level was ˜1 mm/yr from 1900-1995.

  7. 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

  8. Updating Maryland's sea-level rise projections

    USGS Publications Warehouse

    Boesch, Donald F.; Atkinson, Larry P.; Boicourt, William C.; Boon, John D.; Cahoon, Donald R.; Dalrymple, Robert A.; Ezer, Tal; Horton, Benjamin P.; Johnson, Zoe P.; Kopp, Robert E.; Li, Ming; Moss, Richard H.; Parris, Adam; Sommerfield, Christopher K.

    2013-01-01

    With its 3,100 miles of tidal shoreline and low-lying rural and urban lands, “The Free State” is one of the most vulnerable to sea-level rise. Historically, Marylanders have long had to contend with rising water levels along its Chesapeake Bay and Atlantic Ocean and coastal bay shores. Shorelines eroded and low-relief lands and islands, some previously inhabited, were inundated. Prior to the 20th century, this was largely due to the slow sinking of the land since Earth’s crust is still adjusting to the melting of large masses of ice following the last glacial period. Over the 20th century, however, the rate of rise of the average level of tidal waters with respect to land, or relative sea-level rise, has increased, at least partially as a result of global warming. Moreover, the scientific evidence is compelling that Earth’s climate will continue to warm and its oceans will rise even more rapidly. Recognizing the scientific consensus around global climate change, the contribution of human activities to it, and the vulnerability of Maryland’s people, property, public investments, and natural resources, Governor Martin O’Malley established the Maryland Commission on Climate Change on April 20, 2007. The Commission produced a Plan of Action that included a comprehensive climate change impact assessment, a greenhouse gas reduction strategy, and strategies for reducing Maryland’s vulnerability to climate change. The Plan has led to landmark legislation to reduce the state’s greenhouse gas emissions and a variety of state policies designed to reduce energy consumption and promote adaptation to climate change.

  9. Influence of Sea Level Rise on the Dynamics of Salt Inflows in the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Hordoir, R.; Axell, L.; Löptien, U.; Dietze, H.; Kuznetsov, I.

    2016-02-01

    The Baltic Sea is a marginal sea, located in a highly industrialized region in Central Northern Europe.Salt water inflows from the North Sea and associated ventilation of the deep exert crucial control on the entire Baltic Sea ecosystem.This study explores the impact of anticipated sea level changes on the dynamics of those inflows. We usea numerical oceanic general circulation model covering both the Baltic andthe North Sea. The model sucessfully retraces the essential ventilation dynamicsthroughout the period 1961 to 2007. A suite of idealized experiments suggests thatrising sea level is associated with intensified ventilation as salt water inflowsbecome stronger, longer and more frequent. Expressed quantitatively as a salinityincrease in the deep central Baltic Sea we find that a sea level rise of 1 m triggers asaltening of more than 1 PSU. This substantial increase in ventilation is theconsequence of the increasing cross section in the Danish Straits amplified bya reduction of vertical mixing.

  10. 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.

  11. Differences between mean tide level and mean sea level

    NASA Astrophysics Data System (ADS)

    Woodworth, P. L.

    2017-01-01

    This paper discusses the differences between mean tide level (MTL) and mean sea level (MSL) as demonstrated using information from a global tide gauge data set. The roles of the two main contributors to differences between MTL and MSL (the M4 harmonic of the M2 semidiurnal tide, and the combination of the diurnal tides K1 and O1) are described, with a particular focus on the spatial scales of variation in MTL-MSL due to each contributor. Findings from the tide gauge data set are contrasted with those from a state-of-the-art global tide model. The study is of interest within tidal science, but also has practical importance regarding the type of mean level used to define land survey datums. In addition, an appreciation of MTL-MSL difference is important in the use of the historical sea level data used in climate change research, with implications for some of the data stored in international databanks. Particular studies are made of how MTL and MSL might differ through the year, and if MTL is measured in daylight hours only, as has been the practice of some national geodetic agencies on occasions in the past.

  12. On how climate variability influences regional sea level change

    NASA Astrophysics Data System (ADS)

    Brunnabend, Sandra-Esther; Kusche, Jürgen; Rietbroek, Roelof; Forootan, Ehsan

    2016-04-01

    Regional trends in sea level change are strongly influenced by climate variations, such as ENSO (El-Nino Southern Oscillation), the IOD (Indian Ocean Dipole), or the PDO (Pacific Decadal Oscillation). Hence, before computing long term regional sea level change, these sea level variations need to be taken into account as they lead to strong dependencies of computed regional sea level trends on the time period of the investigation. In this study, sea level change during the years 1993 to 2013 is analysed to identify the dominant modes of sea level change caused by climate variations. Here, two different gridded altimetry products are analysed, namely ESA's combined CCI SeaLevel v1.1 ECV product (doi: 10.5270/esa-sea_level_cci-1993_2013-v_1.1-201412), and absolute dynamic topography produced by Ssalto/Duacs and distributed by Aviso, with support from Cnes (http://www.aviso.altimetry.fr/duacs/). Reconstructions using the different decomposition techniques including the standard principle component analysis (PCA), rotated empirical orthogonal functions (REOF) and independent component analysis (ICA) method are analysed. They are compared with sea level change modelled with the global finite-element sea-ice ocean model (FESOM). The results indicate that from the applied methods, ICA is most suitable to separate the individual climate variability signals in independent modes of sea level change. This especially holds for extracting the ENSO contribution in sea level changes, which was better separated by applying ICA, from both altimetry and modelled sea level products. In addition, it is presented how modelled sea level change reflects climate variations compared to that identified in the altimetry products.

  13. Long-term Caspian Sea level change

    NASA Astrophysics Data System (ADS)

    Chen, J. L.; Pekker, T.; Wilson, C. R.; Tapley, B. D.; Kostianoy, A. G.; Cretaux, J.-F.; Safarov, E. S.

    2017-07-01

    Caspian Sea level (CSL) has undergone substantial fluctuations during the past several hundred years. The causes over the entire historical period are uncertain, but we investigate here large changes seen in the past several decades. We use climate model-predicted precipitation (P), evaporation (E), and observed river runoff (R) to reconstruct long-term CSL changes for 1979-2015 and show that PER (P-E + R) flux predictions agree very well with observed CSL changes. The observed rapid CSL increase (about 12.74 cm/yr) and significant drop ( -6.72 cm/yr) during the periods 1979-1995 and 1996-2015 are well accounted for by integrated PER flux predictions of +12.38 and -6.79 cm/yr, respectively. We show that increased evaporation rates over the Caspian Sea play a dominant role in reversing the increasing trend in CSL during the past 37 years. The current long-term decline in CSL is expected to continue into the foreseeable future, under global warming scenarios.

  14. Sea level trends for all sections of the Baltic Sea coastline

    NASA Astrophysics Data System (ADS)

    Madsen, Kristine S.; Høyer, Jacob L.; Suursaar, Ülo; Knudsen, Per; She, Jun

    2016-04-01

    To better understand influence of sea level rise on societal vulnerability and coastal erosion processes, it is important to know the sea level trend. The coastline of the Baltic Sea is not uniformly exposed, and therefore we will determine the sea level trend of the last 10, 50 and 100 years for all sections of the coastline. The observational record of sea level in the Baltic Sea is quite unique with several records of more than 100 years of data. However, the information is confined to the tide gauge locations. Here, we utilize a statistical method based on least squares regression and originally developed for short term sea level variability (Madsen et al. 2015, JGR, doi:10.1002/2015JC011070) to spread out the sea level information from selected tide gauges to all sections of the Baltic Sea coast. Monthly mean tide gauge observations are retrieved from PSMSL and supplemented with Estonian observations. The spatial distribution of the sea level is obtained from model reanalysis from the Copernicus Marine Service and satellite altimetry observations and land rise information is taken into account. Results are validated against independent tide gauges, providing a consistent record of 20th century sea level trends and variability, including uncertainties, for the entire Baltic Sea coastline. This work is sponsored by the EMODnet project Baltic Checkpoint.

  15. Distinguishing Between Natural and Anthropogenic Part of Sea Level Trends

    NASA Astrophysics Data System (ADS)

    Becker, M.; Karpytchev, M.; Lennartz-Sassinek, S.

    2014-12-01

    Detection and attribution of human influence on sea level rise are important topics that have not yet been explored in depth. From the perspective of assessing the contribution of human activities to climate changes, the sea level drivers can be partitioned in anthropogenic and natural forcing. In this study we try to answer the following two questions: (1) How large a sea level trend could be expected as result of natural internal variability? (2) Whether the sea level changes observed over the past century were natural in origin. We suppose that natural behavior of sea level consists of increases and decreases occurring with frequencies following a power law distribution and the monthly sea level records are power law long-term correlated time series. Then we search for the presence of unnatural external sea level trend by applying statistics of Lennartz and Bunde [2009]. We estimate the minimum anthropogenic sea level trend as a lower bound of statistically significant external sea level trend in the longest tide-gauge records worldwide. We apply this new method to distinguish between the trend-like natural oscillations and the external trends in the longest available sea level records and in global mean sea level reconstructions. The results show that the long-term persistence impacts strongly on sea level rise estimation. We provide statistical evidences that the observed sea level changes, at global and regional scales, are beyond its natural internal variability and cannot be explained without human influence. We found that sea level change during the past century contains an external component at 99% significance level in two thirds of the available longest tidal records worldwide. The anthropogenic sea level trend is about 1 mm/yr in global sea level reconstructions that is more than half of the total observed sea level trend during the XXth century, which is about 1.7 mm/yr. This work provides the first estimate of the minimal anthropogenic contribution

  16. Global sea level change: Determination and interpretation

    NASA Astrophysics Data System (ADS)

    Douglas, Bruce C.

    1995-07-01

    The notion of sea level rise brings to the popular mind the specter of deep inundation of coastal regions. One pictures skyscrapers emerging from the waters like so many sleeping flamingos standing in the shallows of a lake. Of course if all of the world's ice sheets suddenly melted or collapsed, this vision would apply to New York City and its coastal counterparts. But there is a general consensus that such a calamity is not an immediate threat [Houghton et al, 1990]. The actual situation for the recent historical past and near future appears to be more benign, but with nonetheless extremely significant, even devastating impacts due to erosion and flooding of coastal areas.

  17. Sea-level rise and coastal wetlands.

    PubMed

    Blankespoor, Brian; Dasgupta, Susmita; Laplante, Benoit

    2014-12-01

    This paper seeks to quantify the impact of a1-m sea-level rise on coastal wetlands in 86 developing countries and territories. It is found that approximately 68 % of coastal wetlands in these countries are at risk. A large percentage of this estimated loss is found in Europe and Central Asia, East Asia, and the Pacific, as well as in the Middle East and North Africa. A small number of countries will be severely affected. China and Vietnam(in East Asia and the Pacific), Libya and Egypt (in the Middle East and North Africa), and Romania and Ukraine (in Europe and Central Asia) will bear most losses. In economic terms, the loss of coastal wetlands is likely to exceed $703 million per year in 2000 US dollars.

  18. 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.

  19. New Constraints on Relative Sea-Level Change in Northern Greenland from Marine Bivalves; Implications for Ice History and GIA Models

    NASA Astrophysics Data System (ADS)

    Glueder, A.; Mix, A. C.; Milne, G. A.; Lecavalier, B.; Reilly, B. T.; Clark, J.; Holm, C.; Padman, J.; Ross, A.; Southon, J. R.

    2016-12-01

    The Greenland Ice Sheet (GIS) holds an ice-mass equivalent to about 6 meters of eustatic sea level equivalent. Understanding its melt dynamics and placing its vulnerability within the climatic context of the Holocene is essential in order to better constrain glacio-isostatic adjustment (GIA) models and predict future GIS contributions to global sea level. Radiocarbon dates obtained from bivalve samples collected on raised marine deposits during the Petermann15 Expedition (July 2015), in Hall Land, Washington Land of NW Greenland, and the Cape Baird region of Ellesmere Island, constrain relative sea-level histories. We applied a depth habitat correction based on δ18O. Both raw data and habitat corrected data suggest a significant mismatch with previously employed GIA models, both in amplitude and rate of relative sea level change. These findings suggest the need for new views of ice load history in Northern Greenland, inclusion of marine ice dynamics in models of ice retreat, and perhaps better constraints on regional variations in viscosity in GIA ice-models.

  20. Ice-sheet collapse and sea-level rise at the Bølling warming 14,600 years ago.

    PubMed

    Deschamps, Pierre; Durand, Nicolas; Bard, Edouard; Hamelin, Bruno; Camoin, Gilbert; Thomas, Alexander L; Henderson, Gideon M; Okuno, Jun'ichi; Yokoyama, Yusuke

    2012-03-28

    Past sea-level records provide invaluable information about the response of ice sheets to climate forcing. Some such records suggest that the last deglaciation was punctuated by a dramatic period of sea-level rise, of about 20 metres, in less than 500 years. Controversy about the amplitude and timing of this meltwater pulse (MWP-1A) has, however, led to uncertainty about the source of the melt water and its temporal and causal relationships with the abrupt climate changes of the deglaciation. Here we show that MWP-1A started no earlier than 14,650 years ago and ended before 14,310 years ago, making it coeval with the Bølling warming. Our results, based on corals drilled offshore from Tahiti during Integrated Ocean Drilling Project Expedition 310, reveal that the increase in sea level at Tahiti was between 12 and 22 metres, with a most probable value between 14 and 18 metres, establishing a significant meltwater contribution from the Southern Hemisphere. This implies that the rate of eustatic sea-level rise exceeded 40 millimetres per year during MWP-1A.

  1. Dinoflagellate cysts as indicators of palaeoenvironmental and sea-level change: the Late Cenomanian - Early Coniacian (Cretaceous) of Europe

    NASA Astrophysics Data System (ADS)

    Olde, Kate; Jarvis, Ian; Pearce, Martin; Tocher, Bruce

    2014-05-01

    The Late Cretaceous represented a period of greenhouse climate of Earth history, and was characterised by high temperatures, high atmospheric CO2 and high eustatic sea level, with large areas of shallow, warm, epicontinental sea. Understanding the dynamics of the Late Cretaceous climate is important for understanding the Earth System and the impact of modern climate change. The productive Late Cretaceous oceans led to the deposition of a large portion of the world's oil and gas resources, so reconstruction of depositional environments and refinement of stratigraphic correlation are important for the petroleum industry. Dinoflagellates were a prolific and diverse group within the phyto- and zooplankton throughout Late Cretaceous oceans, and their cysts display good preservation across different facies, and so are a good group for biostratigraphic and palaeoenvironmental study. Selected results from a high-resolution quantitative study of the palynology from 5 European Upper Cenomanian to the Lower Coniacian (Upper Cretaceous) sections are summarised, along with their carbon stable-isotope chemostratigraphy. The sections are from a range of palaeolatitudes and basins, including the North Sea Basin, the Anglo-Paris Basin, the Bohemian Basin, the Polish Trough and the Vocontian Basin. Palynological assemblages differ between sections in the concentration of palynomorphs, proportions of terrestrial and marine palynomorphs, and in the diversity and varying proportions of species of dinoflagellate cysts (dinocysts). Dinocyst distribution is considered to have been controlled largely by nutrient levels, but was also impacted by temperature, sea level, and water mass changes. Influxes of certain species are related to changes in salinity, changes in temperature, and water mass change, and increased communication between basins. High dinocyst abundance, and particularly a high proportion of peridinioid cysts (which are thought to be derived from eutrophy

  2. Sea Level Rise and Decadal Variations in the Ligurian Sea Inferred from the Medimaremetre Measurements.

    NASA Astrophysics Data System (ADS)

    Karpytchev, M.; Coulomb, A.; Vallee, M.

    2015-12-01

    Estimations of sea level rise over the last centuries are mostly based on the rare historical sea level records from tide gauge stations usually designed for navigational purposes. In this study, we examine the quality of sea level measurements performed by a mean sea level gauge operated in Nice from 1887 to 1909 and transferred to the nearby town of Villefranche-sur-Mer in 1913 where it stayed in operation untill 1974. The mean sea level gauges, called medimaremetres, were invented for geodetic studies and installed in many French ports since the end of the XIX century. By construction, the medimaremetre was connected to the sea through a porous porcelain crucible in order to filter out the tides and higher frequency sea level oscillations. Ucontrolled properties of the crucible and some systematic errors made the medimaremetre data to be ignored in the current sea level researches. We demonstrate that the Nice-Villefranche medimaremetre measurements are coherent with two available historical tide gauge records from Marseille and Genova and a new century-scale sea level series can be build up by combining the medimaremetre data with the those recorded by a tide gauge operating in Nice since the 1980s. We analyse the low frequency variabilities in Marseille, Nice-Villefranche and Genova and get new insights on the decadal sea level variations in the Ligurian Sea since the end of the XIX century.

  3. Using δ18O of Conodont Apatite and Sequence Stratigraphy to Understand Early Triassic (Smithian) Sea-Level Change

    NASA Astrophysics Data System (ADS)

    Yurchyk, S.; Elrick, M.; Atudorei, V.

    2009-12-01

    The Early Triassic climate is conventionally interpreted to have been warm and ice-free. During this time, three globally recognized depositional sequences developed in response to My-scale eustatic sea-level changes. The rates of My-scale sea-level rise and fall are too fast to attribute to changes in mid-ocean ridge activity and too slow to attribute to typical ~20-400 ky orbital cycles that drive glacio-eustasy. Previous studies in the Middle Devonian, Late Cretaceous, and Middle Eocene greenhouse climates have suggested that significant glacio-eustatic sea-level changes were responsible for sequence development. This suggests that these particular greenhouse periods were not uniformly warm and ice-free. We are testing the hypothesis that My- and orbital-scale sea-level changes in the Early Triassic (Smithian) were driven by glacio- and/or thermo-eustasy. To test this hypothesis, Smithian marine successions from two localities in the western United States (Lower Thaynes Formation) were described on a bed-by-bed basis to provide facies and depositional environment interpretations, as well as put the sections into a sequence stratigraphic framework. Samples were collected from both locations for high-resolution (~1-10 m) oxygen isotopic analysis of conodont apatite. Conodont elements are excellent biostratigraphic indicators and the apatite is less susceptible to diagenetic alteration than carbonate minerals, making conodont apatite a reliable proxy for determining changes in ice volume and seawater temperatures in deep time. In northeastern Utah (Weber Canyon), the Smithian sequence (~240 m) is composed of a mixed carbonate-siliciclastic lowstand systems tract (>40 m) and transgressive systems tract (~110 m), a black shale maximum flooding zone (~15 m), and a carbonate-dominated highstand systems tract (~75 m). In western Utah (Confusion Range), the sequence is composed of a coarse-grained, carbonate-dominated transgressive systems tract (>40 m) and a mixed

  4. Carbon-isotope composition of Lower Cretaceous fossil wood: Ocean-atmosphere chemistry and relation to sea-level change

    SciTech Connect

    Groecke, D.R.; Hesselbo, S.P.; Jenkyns, H.C.

    1999-02-01

    The carbon-isotope composition of fossil wood fragments, collected through a biostratigraphically well-constructed Aptian (Lower Cretaceous) shallow-marine siliciclastic succession on the Isle of Wight, southern Britain, shows distinct variations with time. The results indicate that the stratigraphic signature of {delta}{sup 13}C{sub wood} through the Aptian was influenced primarily by fluctuations in the isotopic composition of CO{sub 2} in the global ocean-atmosphere system, as registered in marine carbonates elsewhere, and was not governed by local paleoenvironmental and/or paleoecological factors. Negative and positive excursions in {delta}{sup 13}C{sub wood} through the lower Aptian occur in phase with inferred transgressions and regressions, respectively -- a pattern that contrasts with that observed in many previous studies for different time intervals. The relationship between {delta}{sup 13}C variations and relative sea-level change is tentatively interpreted as a response to various climatic and eustatic factors, relating to rapid sea-floor spreading, thermal uplift of ocean floor, emplacement of plateaus, volcanic CO{sub 2} emissions, weathering, and sedimentary rate.

  5. Timescales for detecting a significant acceleration in sea level rise

    PubMed Central

    Haigh, Ivan D.; Wahl, Thomas; Rohling, Eelco J.; Price, René M.; Pattiaratchi, Charitha B.; Calafat, Francisco M.; Dangendorf, Sönke

    2014-01-01

    There is observational evidence that global sea level is rising and there is concern that the rate of rise will increase, significantly threatening coastal communities. However, considerable debate remains as to whether the rate of sea level rise is currently increasing and, if so, by how much. Here we provide new insights into sea level accelerations by applying the main methods that have been used previously to search for accelerations in historical data, to identify the timings (with uncertainties) at which accelerations might first be recognized in a statistically significant manner (if not apparent already) in sea level records that we have artificially extended to 2100. We find that the most important approach to earliest possible detection of a significant sea level acceleration lies in improved understanding (and subsequent removal) of interannual to multidecadal variability in sea level records. PMID:24728012

  6. Global sea-level changes during the past century

    NASA Technical Reports Server (NTRS)

    Gornitz, Vivien; Lebedeff, Sergej

    1987-01-01

    A novel technique, initially developed for climate studies, is used to reevaluate the estimate of relative sea-level change over the past century. The technique produces a composite regional average sea-level curve from the tide-gage data of individual stations. The effects of glacioisostasy and long-term tectonism are accounted for using late Holocene sea-level indicators. Along the east coast of North America, an apparent maximum sea-level rise is detected in both tide-gage and late Holocene sea-level indicators between Chesapeake Bay and New Jersey. Sea-level changes in western North America reveal greater spatial variations than for the east coast, which can be related to more active tectonism in California and British Columbia and to strong localized isostatic rebound in Alaska.

  7. Global sea-level changes during the past century

    NASA Technical Reports Server (NTRS)

    Gornitz, Vivien; Lebedeff, Sergej

    1987-01-01

    A novel technique, initially developed for climate studies, is used to reevaluate the estimate of relative sea-level change over the past century. The technique produces a composite regional average sea-level curve from the tide-gage data of individual stations. The effects of glacioisostasy and long-term tectonism are accounted for using late Holocene sea-level indicators. Along the east coast of North America, an apparent maximum sea-level rise is detected in both tide-gage and late Holocene sea-level indicators between Chesapeake Bay and New Jersey. Sea-level changes in western North America reveal greater spatial variations than for the east coast, which can be related to more active tectonism in California and British Columbia and to strong localized isostatic rebound in Alaska.

  8. Timescales for detecting a significant acceleration in sea level rise.

    PubMed

    Haigh, Ivan D; Wahl, Thomas; Rohling, Eelco J; Price, René M; Pattiaratchi, Charitha B; Calafat, Francisco M; Dangendorf, Sönke

    2014-04-14

    There is observational evidence that global sea level is rising and there is concern that the rate of rise will increase, significantly threatening coastal communities. However, considerable debate remains as to whether the rate of sea level rise is currently increasing and, if so, by how much. Here we provide new insights into sea level accelerations by applying the main methods that have been used previously to search for accelerations in historical data, to identify the timings (with uncertainties) at which accelerations might first be recognized in a statistically significant manner (if not apparent already) in sea level records that we have artificially extended to 2100. We find that the most important approach to earliest possible detection of a significant sea level acceleration lies in improved understanding (and subsequent removal) of interannual to multidecadal variability in sea level records.

  9. Global sea level trend in the past century

    NASA Technical Reports Server (NTRS)

    Gornitz, V.; Lebedeff, S.; Hansen, J.

    1982-01-01

    Data derived from tide-gauge stations throughout the world indicate that the mean sea level rose by about 12 centimeters in the past century. The sea level change has a high correlation with the trend of global surface air temperature. A large part of the sea level rise can be accounted for in terms of the thermal expansion of the upper layers of the ocean. The results also represent weak indirect evidence for a net melting of the continental ice sheets.

  10. Global sea level trend in the past century

    NASA Technical Reports Server (NTRS)

    Gornitz, V.; Lebedeff, S.; Hansen, J.

    1982-01-01

    Data derived from tide-gauge stations throughout the world indicate that the mean sea level rose by about 12 centimeters in the past century. The sea level change has a high correlation with the trend of global surface air temperature. A large part of the sea level rise can be accounted for in terms of the thermal expansion of the upper layers of the ocean. The results also represent weak indirect evidence for a net melting of the continental ice sheets.

  11. New estimate of the current rate of sea level rise from a sea level budget approach

    NASA Astrophysics Data System (ADS)

    Dieng, H. B.; Cazenave, A.; Meyssignac, B.; Ablain, M.

    2017-04-01

    We revisit the global mean sea level (GMSL) budget during the whole altimetry era (January 1993 to December 2015) using a large number of data sets. The budget approach allows quantifying the TOPEX A altimeter drift (amounting 1.5 ± 0.5 mm/yr over 1993-1998). Accounting for this correction and using ensemble means for the GMSL and components lead to closure of the sea level budget (trend of the residual time series being 0.0 ± 0.22 mm/yr). The new GMSL rate over January 1993 to December 2015 is now close to 3.0 mm/yr. An important increase of the GMSL rate, of 0.8 mm/yr, is found during the second half of the altimetry era (2004-2015) compared to the 1993-2004 time span, mostly due to Greenland mass loss increase and also to slight increase of all other components of the budget.

  12. Global sea level fluctuations and uncertainties through a Wilson cycle based on ocean basin volume reconstructions

    NASA Astrophysics Data System (ADS)

    Wright, Nicky; Seton, Maria; Williams, Simon E.; Dietmar Müller, R.

    2017-04-01

    Variations in the volume of ocean basins is the main driving force for (long-wavelength) changes in eustatic sea level in an ice-free world, i.e. most of the Mesozoic and Cenozoic. The volume of ocean basins is largely dependent on changes in the seafloor spreading history, which can be reconstructed based on an age-depth relationship for oceanic crust and an underlying global plate kinematic model. Ocean basin volume reconstructions need to include: (1) a predicted history of back-arc basin formation, including where geological evidence exists for the opening and closing of back-arc basins within a single Wilson cycle, (2) the emplacement and subsidence of oceanic plateaus (LIPs), (3) variations in sediment thickness through time, and (4) a reconstruction of the depth of continental margins and fragments. Unfortunately, due to subduction of oceanic crust, we must rely on synthetically modelled ocean crust for much of Earth's history, for which it is impossible to ground truth the history of LIPs and sediment thickness. In order to improve reconstructions of sea level on geologic time scales and assess the uncertainty in deriving the volume of ocean basins based on a global plate kinematic model, we investigate the influence of these poorly constrained features (e.g. LIPs, back-arc basins, sediment thickness, passive margins) on ocean basin volume since 230 Ma (i.e. throughout an entire Wilson cycle). We assess the characteristics for each feature at present-day and during well-constrained times during the Cenozoic, and create suites of alternative paleobathymetry grids which incorporate varying degrees of each feature's influence. Further, we derive a global sea level curve based only on the reconstruction of ocean basin volume (i.e. excluding effects such as dynamic topography and glaciation), and present the influence of each component and their uncertainties through time. We find that by incorporating reasonable predictions for these components during times

  13. The social values at risk from sea-level rise

    SciTech Connect

    Graham, Sonia; Barnett, Jon; Fincher, Ruth; Hurlimann, Anna; Mortreux, Colette; Waters, Elissa

    2013-07-15

    Analysis of the risks of sea-level rise favours conventionally measured metrics such as the area of land that may be subsumed, the numbers of properties at risk, and the capital values of assets at risk. Despite this, it is clear that there exist many less material but no less important values at risk from sea-level rise. This paper re-theorises these multifarious social values at risk from sea-level rise, by explaining their diverse nature, and grounding them in the everyday practices of people living in coastal places. It is informed by a review and analysis of research on social values from within the fields of social impact assessment, human geography, psychology, decision analysis, and climate change adaptation. From this we propose that it is the ‘lived values’ of coastal places that are most at risk from sea-level rise. We then offer a framework that groups these lived values into five types: those that are physiological in nature, and those that relate to issues of security, belonging, esteem, and self-actualisation. This framework of lived values at risk from sea-level rise can guide empirical research investigating the social impacts of sea-level rise, as well as the impacts of actions to adapt to sea-level rise. It also offers a basis for identifying the distribution of related social outcomes across populations exposed to sea-level rise or sea-level rise policies.

  14. Ice-sheet and sea-level changes.

    PubMed

    Alley, Richard B; Clark, Peter U; Huybrechts, Philippe; Joughin, Ian

    2005-10-21

    Future sea-level rise is an important issue related to the continuing buildup of atmospheric greenhouse gas concentrations. The Greenland and Antarctic ice sheets, with the potential to raise sea level approximately 70 meters if completely melted, dominate uncertainties in projected sea-level change. Freshwater fluxes from these ice sheets also may affect oceanic circulation, contributing to climate change. Observational and modeling advances have reduced many uncertainties related to ice-sheet behavior, but recently detected, rapid ice-marginal changes contributing to sea-level rise may indicate greater ice-sheet sensitivity to warming than previously considered.

  15. Sea-level rise and its impact on coastal zones.

    PubMed

    Nicholls, Robert J; Cazenave, Anny

    2010-06-18

    Global sea levels have risen through the 20th century. These rises will almost certainly accelerate through the 21st century and beyond because of global warming, but their magnitude remains uncertain. Key uncertainties include the possible role of the Greenland and West Antarctic ice sheets and the amplitude of regional changes in sea level. In many areas, nonclimatic components of relative sea-level change (mainly subsidence) can also be locally appreciable. Although the impacts of sea-level rise are potentially large, the application and success of adaptation are large uncertainties that require more assessment and consideration.

  16. Demographic responses to sea level rise in California

    SciTech Connect

    Constable, A. |; Van Arsdol, M.D. Jr.; Sherman, D.J.; Wang, J.; McMullin-Messier, P.A.; Rollin, L.

    1996-12-31

    Human consequences of sea level rise in California coastal counties reflect increasing population densities. Populations of coastal counties potentially affected by sea level rise are projected to increase from 26.2 million persons in 1990 to 63.3 million persons in 2040. Urbanization dominates Los Angeles and the South Coast and San Francisco Bay and Delta regions. California shoreline populations subject to potential disruption impacts of sea level rise are increasing rapidly. Enhanced risk zones for sea level rise are specified for the Oxnard Plain of Ventura County on the south coast of California. Four separate sea level rise scenarios are considered: (1) low (sea level rise only); (2) moderate (adding erosion); (3) high (adding erosion and storm surges); and (4) a maximum case, a 3 m enhanced risk zone. Population impacts are outlined for the 3 m zone. More serious impacts from storm surges are expected than from sea level rise and erosion. Stakeholders who support or oppose policies which may expose populations to sea level rise include energy, commercial, financial, industrial, public agency, private interest and governmental organizations. These organizations respond to extreme events from differing positions. Vested interests determine the degree of mitigation employed by stakeholders to defer impacts of sea level rise.

  17. Timing and Estimates of Plio-Pleistocene Sea-Level Highstands from the Republic of South Africa (RSA)

    NASA Astrophysics Data System (ADS)

    Hearty, Paul; Raymo, Maureen; Sandstrom, Michael; Rovere, Alessio; O'Leary, Michael

    2016-04-01

    The rapid rise in atmospheric CO2 exceeding 400 ppmv is driving an urgent need to better understand past sea level, ice sheet dynamics, and climate change associated with past warmer geological intervals. The LR04 record reveals sustained intervals during the Pliocene (5.6-2.6 Ma) when δ18O exceeded the present levels, indicating a possible decrease in the volume of polar ice sheets. Other shorter intervals of likely decreased ice volume occur during Pleistocene interglacials including MIS 5e, 11, 31, and 37.Here we focus on the middle Pliocene warm period (MPWP; 3.3 to 2.9 Ma), an interval during which Earth experienced CO2 levels around 400 ppmv (Fedorov et al., 2013). The intra-plate coastal margin of western South Africa, a region of relative tectonic stability and relative insensitivity to uncertainty in mantle viscosity as is effects corrections for glacial isostatic adjustment, is a promising region for deriving estimates of eustatic sea level (ESL; thus ice volumes) at the end of the MPWP (Rovere et al., 2014). During a field expedition covering several thousand kilometres along coastlines of western and southern coasts of RSA, we documented the stratigraphy, geomorphology, and geochronology of Pliocene and Pleistocene shorelines with differential GPS providing decimeter scale accuracy to stratigraphic contacts and sea-level indicators. From about twenty sites, precise elevations (as yet uncorrected for GIA) of multiple sea stands were recorded. Strontium isotopes were used to date the shell material from many of the marine sites, but only three sites yielded reliable age data that passed screening criteria for diagenesis. The oldest shoreline evidence, from Cliffs Point on the west coast near the Olifants River, is observed at 34.9 ±0.2 m asl and yields an age 4.70 ± 0.20 Ma; a younger shoreline from the southern coast Bredasdorp site is observed at >24.0 ± 1.5 m asl and yields ages from 3.00 ± 0.45 to 3.55 ± 0.31 Ma, the interval of the MPWP. . A

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

    NASA Astrophysics Data System (ADS)

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

    2017-07-01

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

  19. Estimation of Holocene Land Movement and Sea Level Changes in Southwest Scandinavia - Results From Interpretation of Relative Sea Level Curves

    NASA Astrophysics Data System (ADS)

    Nielsen, L.; Hede, M.; Clemmensen, L. B.; Morten Hansen, J.; Noe-Nygaard, N.; Sander, L.; Bendixen, M.; Kroon, A.; Murray, A. S.; Pejrup, M.

    2013-12-01

    Relative sea level curves from different localities in Denmark, southwest Scandinavia, are used for estimation of Holocene vertical land movement and absolute sea level variations in the gateway between the North Sea and the Baltic Sea. Two previous independent studies conducted in the area show that ground penetrating radar reflection images of internal beach ridge and swale architecture form a strong basis for estimation of relative sea level variation. Sediments are dated using optically stimulated luminescence (OSL); this shows that the beach ridges and swales were last exposed to daylight between ~6500 and 0 years ago. Time periods with characteristic changes in the rate of relative sea level change are identified at different localities. The observed relative sea level change rates differ in the study area, mainly because the different localities have experienced different isostatic rebound since the latest glaciation. Variations in uplift rates and absolute sea level change for the region are estimated by inversion of the observed relative sea level changes. The values obtained for the different time periods put constraints on absolute sea level variation during the Holocene and have implications for our understanding of the lithosphere's temporal response to the unloading caused by melting of the thick ice sheet formed during the latest glaciation in Scandinavia.

  20. Quantifying the impact of basin dynamics on the regional sea level rise in the Black Sea

    NASA Astrophysics Data System (ADS)

    Kubryakov, Arseny A.; Stanichny, Sergey V.; Volkov, Denis L.

    2017-06-01

    Satellite altimetry measurements show that the magnitude of the Black Sea sea level trends is spatially uneven. While the basin-mean sea level rise from 1993 to 2014 was about 3.15 mm yr-1, the local rates of sea level rise varied from 1.5-2.5 mm yr-1 in the central part to 3.5-3.8 mm yr-1 at the basin periphery and over the northwestern shelf and to 5 mm yr-1 in the southeastern part of the sea. We show that the observed spatial differences in the dynamic sea level (anomaly relative to the basin-mean) are caused by changes in the large- and mesoscale dynamics of the Black Sea. First, a long-term intensification of the cyclonic wind curl over the Black Sea, observed in 1993-2014, strengthened divergence in the center of the basin and led to the rise of the sea level in coastal and shelf areas and a lowering in the basin's interior. Second, an extension of the Batumi anticyclone to the west resulted in ˜ 1.2 mm yr-1 higher rates of sea level rise in the southeastern part of the sea. Further, we demonstrate that the large-scale dynamic sea level variability in the Black Sea can be successfully reconstructed using the wind curl obtained from an atmospheric reanalysis. This allows for the correction of historical tide gauge records for dynamic effects in order to derive more accurate estimates of the basin-mean sea level change in the past, prior to the satellite altimetry era.

  1. Applications of ESR dating and18O Paleotemperature data for studies on Quaternary sea-level changes

    NASA Astrophysics Data System (ADS)

    Huang, Peihua; Peng, Zicheng; Jin, Sizhao; Liang, Renyou; Quan, Yucai; Wang, Zhaorong

    1989-03-01

    Electron Spin Resonance (ESR) dating is a relatively new technique applicable also to the dating of materials from littoral zones and shallow sea regions, such as shells, corals, bones and teeth, foraminifera, diatoms, etc. ESR dating can span the time interval between the older limit of14C dating and the younger limit of the K-Ar dating, an interval of 103 106 years. Therefore, ESR technique is very suitatie for the measurement of the age of Quaternary sea—level changes. This paper gives some samples’ results by ESR dating from Early Pleistoncene to Holocene. The Quaternary sea—level changes in China were mainly eustatisms that corresponded to the paleotemperature variation. We have just begun study on the18O Paleotemperature in our continental area. Preliminary results show the temperature curve of the stalagmitic growth in caves corresponds well to the sea—level changes in 76 55×103 years B. P. ESR dating and studies of the18O Paleotemperature in East China will raise studies on Quaternary sea—level changes to a higher scientific basis.

  2. Climate variability, extremes and trends of total sea level variations of the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Lehmann, Andreas; Herrford, Josefine; Höflich, Katharina; Getzlaff, Klaus

    2017-04-01

    The total sea level change of the Baltic Sea is a combination of wind-driven large volume changes (LVCs), local sea level variations (water level raised by wind and seiche) and wind waves including the sea level change by climatic-driven water density changes and the global sea level rise. The ocean surface velocity is a combination of Ekman surface flow, baroclinic and barotropic flow components and Stokes drift. The first two components can be calculated by standard hydrodynamic 3-dimensional ocean circulation models. But the calculation of the Stokes drift needs an additional approach. The Stokes velocity is a function of the significant wave height and period. It is important for the generation of Langmuir circulation which in turn contributes to the vertical mixing near the ocean surface and to the wind-driven surface transport. We used the Kiel Baltic Sea ice-ocean model (BSIOM) coupled with a simple fully integrated wave model to determine total sea level changes of the entire Baltic Sea for the period 1979-2016. BSIOM has been forced by ERA-Interim reanalysis data (1979-2016). The coupled model system allows the calculation of the total sea level change on a 2.5 km model grid of the entire Baltic Sea as a combination of large volume changes (LVCs), local sea level variations and wind waves including the sea level rise due to climatic-driven water density changes. Thus, combining sea level changes of different time and space scales. Different areas of the Baltic Sea show different trends in significant wave heights over different seasons. During winter, an increase of significant wave height is mainly associated with the retreat of the sea ice cover. There is also an increase of significant wave height of about 5 cm/decade in the eastern Gotland basin during winter. In summer and autumn we found negative trends strongest in the south-western Baltic Sea. Extreme total sea level variations occur if LVCs coincide with local sea level variations and wind waves.

  3. Sea-level fluctuations during the last glacial cycle

    NASA Astrophysics Data System (ADS)

    Siddall, M.; Rohling, E. J.; Almogi-Labin, A.; Hemleben, Ch.; Meischner, D.; Schmelzer, I.; Smeed, D. A.

    2003-06-01

    The last glacial cycle was characterized by substantial millennial-scale climate fluctuations, but the extent of any associated changes in global sea level (or, equivalently, ice volume) remains elusive. Highstands of sea level can be reconstructed from dated fossil coral reef terraces, and these data are complemented by a compilation of global sea-level estimates based on deep-sea oxygen isotope ratios at millennial-scale resolution or higher. Records based on oxygen isotopes, however, contain uncertainties in the range of +/-30m, or +/-1°C in deep sea temperature. Here we analyse oxygen isotope records from Red Sea sediment cores to reconstruct the history of water residence times in the Red Sea. We then use a hydraulic model of the water exchange between the Red Sea and the world ocean to derive the sill depth-and hence global sea level-over the past 470,000 years (470kyr). Our reconstruction is accurate to within +/-12m, and gives a centennial-scale resolution from 70 to 25kyr before present. We find that sea-level changes of up to 35m, at rates of up to 2cmyr-1, occurred, coincident with abrupt changes in climate.

  4. Mean sea level determination from satellite altimetry

    NASA Technical Reports Server (NTRS)

    Kahn, W. D.; Agrawal, B. B.; Brown, R. D.

    1979-01-01

    The primary experiment on the Geodynamics Experimental Ocean Satellite-3 (GEOS-3) is the radar altimeter. This experiment's major objective is to demonstrate the utility of measuring the geometry of the ocean surface; i.e., the geoid. Results obtained from this experiment so far indicate that the planned objectives of measuring the topography of the ocean surface with an absolute accuracy of + or - 5 m can be met and perhaps exceeded. The GEOS-3 satellite altimeter measurements have an instrument precision in the range of + or - 25 cm to + or - 50 cm when the altimeter is operating in the 'short pulse' mode. After one year's operations of the altimeter, data from over 5000 altimeter passes have been collected. With the mathematical models developed and the altimeter data presently available, mapping of local areas of ocean topography has been realized to the planned accuracy levels and better. This paper presents the basic data processing methods employed and some interesting results achieved with the early data. Plots of mean sea surface heights as inferred by the altimeter measurements are compared with a detailed 1 by 1 deg gravimetric geoid.

  5. Detecting anthropogenic footprints in sea level rise

    PubMed Central

    Dangendorf, Sönke; Marcos, Marta; Müller, Alfred; Zorita, Eduardo; Riva, Riccardo; Berk, Kevin; Jensen, Jürgen

    2015-01-01

    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. PMID:26220773

  6. Wave transformation across coral reefs under changing sea levels

    NASA Astrophysics Data System (ADS)

    Harris, Daniel; Power, Hannah; Vila-Conejo, Ana; Webster, Jody

    2015-04-01

    The transformation of swell waves from deep water across reef flats is the primary process regulating energy regimes in coral reef systems. Coral reefs are effective barriers removing up to 99% of wave energy during breaking and propagation across reef flats. Consequently back-reef environments are often considered low energy with only limited sediment transport and geomorphic change during modal conditions. Coral reefs, and specifically reef flats, therefore provide important protection to tropical coastlines from coastal erosion and recession. However, changes in sea level could lead to significant changes in the dissipation of swell wave energy in coral reef systems with wave heights dependent on the depth over the reef flat. This suggests that a rise in sea level would also lead to significantly higher energy conditions exacerbating the transgressive effects of sea level rise on tropical beaches and reef islands. This study examines the potential implications of different sea level scenarios on the transformation of waves across the windward reef flats of One Tree Reef, southern Great Barrier Reef. Waves were measured on the reef flats and back-reef sand apron of One Tree Reef. A one-dimensional wave model was calibrated and used to investigate wave processes on the reef flats under different mean sea level (MSL) scenarios (present MSL, +1 m MSL, and +2 m MSL). These scenarios represent both potential future sea level states and also the paleo sea level of the late Holocene in the southern Great Barrier Reef. Wave heights were shown to increase under sea level rise, with greater wave induced orbital velocities affecting the bed under higher sea levels. In general waves were more likely to entrain and transport sediment both on the reef flat and in the back reef environment under higher sea levels which has implications for not only forecasted climate change scenarios but also for interpreting geological changes during the late Holocene when sea levels were 1

  7. 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.

  8. Numerical study of the Azov Sea level seiche oscillations

    NASA Astrophysics Data System (ADS)

    Matishov, G. G.; Inzhebeikin, Yu. I.

    2009-08-01

    Seiche oscillations of the Azov Sea level are studied on the basis of the developed two-dimensional numerical hydrodynamic model grounded on the shallow water theory and recent data on the morphometric characteristics of the Sea of Azov. Frequency and spatial characteristics of the first five modes corresponding to seiche oscillations of the Azov Sea level are computed. It is shown that the frequency and spatial characteristics of the first five modes obtained for the Sea of Azov level changes correspond to seiche oscillations. The calculated parameters are compared with the field observations, which show their realistic character.

  9. Impact of sea-level rise on sea water intrusion in coastal aquifers.

    PubMed

    Werner, Adrian D; Simmons, Craig T

    2009-01-01

    Despite its purported importance, previous studies of the influence of sea-level rise on coastal aquifers have focused on specific sites, and a generalized systematic analysis of the general case of the sea water intrusion response to sea-level rise has not been reported. In this study, a simple conceptual framework is used to provide a first-order assessment of sea water intrusion changes in coastal unconfined aquifers in response to sea-level rise. Two conceptual models are tested: (1) flux-controlled systems, in which ground water discharge to the sea is persistent despite changes in sea level, and (2) head-controlled systems, whereby ground water abstractions or surface features maintain the head condition in the aquifer despite sea-level changes. The conceptualization assumes steady-state conditions, a sharp interface sea water-fresh water transition zone, homogeneous and isotropic aquifer properties, and constant recharge. In the case of constant flux conditions, the upper limit for sea water intrusion due to sea-level rise (up to 1.5 m is tested) is no greater than 50 m for typical values of recharge, hydraulic conductivity, and aquifer depth. This is in striking contrast to the constant head cases, in which the magnitude of salt water toe migration is on the order of hundreds of meters to several kilometers for the same sea-level rise. This study has highlighted the importance of inland boundary conditions on the sea-level rise impact. It identifies combinations of hydrogeologic parameters that control whether large or small salt water toe migration will occur for any given change in a hydrogeologic variable.

  10. A search for scale in sea-level studies

    USGS Publications Warehouse

    Larsen, C.E.; Clark, I.

    2006-01-01

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

  11. Sea-level variability in the Mediterranean Sea from altimetry and tide gauges

    NASA Astrophysics Data System (ADS)

    Bonaduce, Antonio; Pinardi, Nadia; Oddo, Paolo; Spada, Giorgio; Larnicol, Gilles

    2016-04-01

    Sea-level variability in the Mediterranean Sea was investigated by means of in-situ (tide-gauge) and satellite altimetry data over a period spanning two decades (from 1993 to 2012). The paper details the sea-level variations during this time period retrieved from the two data sets. Mean sea-level (MSL) estimates obtained from tide-gauge data showed root mean square differences (RMSDs) in the order of 40-50 % of the variance of the MSL signal estimated from satellite altimetry data, with a dependency on the number and quality of the in-situ data considered. Considering the individual time-series, the results showed that coastal tide-gauge and satellite sea-level signals are comparable, with RMSDs that range between 2.5 and 5 cm and correlation coefficients up to the order of 0.8. A coherence analysis and power spectra comparison showed that two signals have a very similar energetic content at semi-annual temporal scales and below, while a phase drift was observed at higher frequencies. Positive sea-level linear trends for the analysis period were estimated for both the mean sea-level and the coastal stations. From 1993 to 2012, the mean sea-level trend (2.44 ± 0.5 mm yr-1) was found to be affected by the positive anomalies of 2010 and 2011, which were observed in all the cases analysed and were mainly distributed in the eastern part of the basin. Ensemble Empirical Mode Decomposition (EEMD) showed that these events were related to the processes that have dominant periodicities of ˜10 years, and positive residual sea-level trend were generally observed in both data-sets. In terms of mean sea-level trends, a significant positive sea-level trend (> 95 %) in the Mediterranean Sea was found on the basis of at least 15 years of data.

  12. Sea-level variability in the Mediterranean Sea from altimetry and tide gauges

    NASA Astrophysics Data System (ADS)

    Bonaduce, A.; Pinardi, N.; Oddo, P.; Spada, G.; Larnicol, G.

    2016-11-01

    Sea-level variability in the Mediterranean Sea was investigated by means of in-situ (tide-gauge) and satellite altimetry data over a period spanning two decades (from 1993 to 2012). The paper details the sea-level variations during this time period retrieved from the two data sets. Mean sea-level (MSL) estimates obtained from tide-gauge data showed root mean square differences (RMSDs) in the order of 40-50 % of the variance of the MSL signal estimated from satellite altimetry data, with a dependency on the number and quality of the in-situ data considered. Considering the individual time-series, the results showed that coastal tide-gauge and satellite sea-level signals are comparable, with RMSDs that range between 2.5 and 5 cm and correlation coefficients up to the order of 0.8. A coherence analysis and power spectra comparison showed that two signals have a very similar energetic content at semi-annual temporal scales and below, while a phase drift was observed at higher frequencies. Positive sea-level linear trends for the analysis period were estimated for both the mean sea-level and the coastal stations. From 1993 to 2012, the mean sea-level trend (2.44± 0.5 mm year^{-1}) was found to be affected by the positive anomalies of 2010 and 2011, which were observed in all the cases analysed and were mainly distributed in the eastern part of the basin. Ensemble empirical mode decomposition showed that these events were related to the processes that have dominant periodicities of ˜10 years, and positive residual sea-level trend were generally observed in both data-sets. In terms of mean sea-level trends, a significant positive sea-level trend (>95 %) in the Mediterranean Sea was found on the basis of at least 15 years of data.

  13. Global sea-level change during the next 10,000 years: the end of an icehouse?

    NASA Astrophysics Data System (ADS)

    Van Breedam, Jonas; Huybrechts, Philippe; Goelzer, Heiko; Loutre, Marie-France; Fichefet, Thierry

    2015-04-01

    Because of the long life-time of atmospheric CO2, any realized future warming is likely to persist for many centuries to millennia. As a consequence, sea-level rise will continue on a multi-millennial timescale, especially from the slower components such as oceanic thermal expansion and above all, from melting of the Greenland and Antarctic ice sheets. The two polar ice sheets have the potential to produce a global eustatic sea-level rise of about 65 m, at least an order of magnitude larger than thermal expansion under extreme forcing scenarios. Other components contributing to sea-level change are the melting of glaciers and ice caps and haline contraction of the ocean from fresh water delivery from land ice, but are less important. We have made projections of future sea-level rise over the next 10,000 years with the Earth System Model of Intermediate Complexity LOVECLIM, which includes high resolution models of the Greenland and Antarctic ice sheets. Four different model parameter sets are considered to explore the model uncertainty. The climate forcing is based on prolonged Radiative Concentration Pathway (RCP) scenarios with an assumed exponential falloff for carbon dioxide concentrations according to global carbon cycle simulations. Six different forcing scenarios are constructed where the highest scenario includes a positive feedback due to the destabilization of methane hydrates and the subsequent emission of methane. By far the largest contribution in the global sea-level projections arises from the polar ice sheets. For the Greenland ice sheet, the ablation is larger than the accumulation for all forcing scenarios shortly after the start of the experiments. The ice sheet continuously melts and nearly disappears in all cases. The Antarctic ice sheet grows during the first decades under low to intermediate forcing scenarios due to increased accumulation. However, the spread between the different scenarios is very large. Under the highest prolonged RCP

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  15. The Paris Agreement's imprint on 2300 sea level rise

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    The 2015 Paris Agreement aims at reducing climate-related risks by putting a limit to global mean temperature increase. Furthermore, global greenhouse gas emissions should peak as soon as possible and reach net-zero in the second half of the 21st century under the agreement. Sea level rise is one of the major impacts of climate change and will continue for long after emissions have ceased. Here we quantify the effect of near-term and long-term emissions constraints of the Paris Agreement on climate-driven sea level rise until 2300 using a contribution-based methodology that is consistent with the IPCC AR5 sea level estimates. We study median sea level rise for scenarios stabilizing global mean temperatures between 1.5° C and 2° C above pre-industrial levels and net-zero greenhouse gas emission scenarios that lead to declining temperatures. Once global mean temperatures pass 1.5 °C, sea level rise below one meter until 2300 is out of reach for temperature stabilization scenarios. Net-zero emissions can reduce sea level rise caused by temperature overshoot only within limits. By linking sea level rise to near-term mitigation action, we find that delayed near-term mitigation action leads to increased sea level rise far beyond 2100.

  16. Late Quaternary depositional history, Holocene sea-level changes, and vertical crustal movement, southern San Francisco Bay, California

    USGS Publications Warehouse

    Atwater, Brian F.; Hedel, Charles W.; Helley, Edward J.

    1977-01-01

    tectonic subsidence in less than 1.5 million years (<0.07 mm/yr) relative to the likely elevation of the lowest Pleistocene land surface; (2) the deepest Sangamon estuarine deposits subsided tectonically about 20–40 m in about 0.1 million years (0.2±0.1–0.4±0.1 mm/yr) relative to the assumed initial elevations of the thalwegs buried by these sediments; and (3) Holocene salt-marsh deposits have undergone about 5 m of tectonic and possibly isostatic subsidence in about 6,000 years (0.8±.0.7 mm/yr) relative to elevations which might be expected from eustatic sea-level changes alone.

  17. Regional Long-Term Sea Level and Sea Surface Temperature Characteristics from Satellite Observations

    NASA Astrophysics Data System (ADS)

    Andersen, O. B.; Knudsen, P.; Beckley, B.

    2006-07-01

    For a the large portion of the world's population liv ing in coastal zones forecasts of long- term sea lev el change is importan t for a var iety of environmen tal and socio- economic r easons. Satellite altimetry offers a unique opportunity for improving our knowledge about glob al and r egional sea level change on bo th global and reg ional scale. Joint TOPEX/PO SEIDON(T/P) +JASON-1 sea level observations and Reyno lds AVH RR sea surface temperature observ ations over th e most recen t 12 years hav e qualitativ ely been used to study regional correlations between long-term changes in sea level and sea surface temper ature. Long-term is here tak en to be lin ear signals in the 12-year time per iod Consistent in creases in both sea level and sea surface temp eratures ar e found in large parts of the world's oceans over this per iod. In the Indian Ocean and particularly th e Pacif ic Ocean , the trends in both sea level and temper ature are domin ated by the larg e changes associated w ith th e El N iño Southern Oscillation (ENSO) . Co mparison with similar trend estimates u sing only 8 years of satellite data shows the incr eased decoupling with ENSO and th e imp act of inter-annual variability on sea lev el tr end estimates.

  18. Developing advanced tools for modelling extreme sea level climate change in European Seas

    NASA Astrophysics Data System (ADS)

    She, Jun; Murawski, Jens; Hintz, Kasper S.

    2017-04-01

    With increasing speed of global warming, sea level rise in the European coasts has become increasing threats to our social-economy and safety. "Hundred-year storm surge events" have been reported in different locations in recent years. Ocean hydrodynamic modelling is one of the major tools for reconstructing and predicting sea level changes in climate scales. Although storm surge modelling is one of the most classic applications of ocean models, there still exist changes in producing accurate sea level variability in all European Sea coasts, especially for the extreme events. This presentation addresses major challenges in pan-European storm surge modelling, presenting sea level simulation results from a two-way nested pan-European Sea (with 10 sub-domains) three-dimensional hydrodynamic model HIROMB-BOOS (HBM). The difference of using two-dimensional and three-dimensional models for storm surge prediction is also analyzed based on past years' operational experiences.

  19. Future Extreme Sea Level Variability in the Tropical Pacific

    NASA Astrophysics Data System (ADS)

    Widlansky, M. J.; Timmermann, A.; Stuecker, M. F.; McGregor, S.; Cai, W.; Chikamoto, Y.

    2014-12-01

    During strong El Niño events, sea level drops around tropical western Pacific islands by up to 20-30 cm. Such extreme events (referred to in Samoa as 'taimasa') expose shallow reefs, thereby damaging associated coastal ecosystems and contributing to the formation of 'flat topped coral heads' often referred to as microatolls. We show that during the termination of strong El Niño events, a southward movement of weak trade winds prolongs extreme low sea levels in the southwestern Pacific. Whereas future sea levels are projected to gradually rise, recent modeling evidence suggests that the frequency of strong El Niño events (which alter local trade winds and sea level) is very likely to increase with greenhouse warming. Such changes could exacerbate El Niño-related sea level drops, especially in the tropical southwestern Pacific. Using present-generation coupled climate models forced with increasing greenhouse-gas concentrations, we assess how the interplay between global mean sea level rise, on one hand, and more frequent interannual sea level drops, on the other, will affect future coastal sea levels in the tropical Pacific.

  20. Arctic Sea Level During the Satellite Altimetry Era

    NASA Astrophysics Data System (ADS)

    Carret, A.; Johannessen, J. A.; Andersen, O. B.; Ablain, M.; Prandi, P.; Blazquez, A.; Cazenave, A.

    2016-11-01

    Results of the sea-level budget in the high latitudes (up to 80°N) and the Arctic Ocean during the satellite altimetry era. We investigate the closure of the sea-level budget since 2002 using two altimetry sea-level datasets based on the Envisat waveform retracking: temperature and salinity data from the ORAP5 reanalysis, and Gravity Recovery And Climate Experiment (GRACE) space gravimetry data to estimate the steric and mass components. Regional sea-level trends seen in the altimetry map, in particular over the Beaufort Gyre and along the eastern coast of Greenland, are of halosteric origin. However, in terms of regional average over the region ranging from 66°N to 80°N, the steric component contributes little to the observed sea-level trend, suggesting a dominant mass contribution in the Arctic region. This is confirmed by GRACE-based ocean mass time series that agree well with the altimetry-based sea-level time series. Direct estimate of the mass component is not possible prior to GRACE. Thus, we estimated the mass contribution from the difference between the altimetry-based sea level and the steric component. We also investigate the coastal sea level with tide gauge records. Twenty coupled climate models from the CMIP5 project are also used. The models lead us to the same conclusions concerning the halosteric origin of the trend patterns.

  1. Upper limit for sea level projections by 2100

    NASA Astrophysics Data System (ADS)

    Jevrejeva, S.; Grinsted, A.; Moore, J. C.

    2014-10-01

    We construct the probability density function of global sea level at 2100, estimating that sea level rises larger than 180 cm are less than 5% probable. An upper limit for global sea level rise of 190 cm is assembled by summing the highest estimates of individual sea level rise components simulated by process based models with the RCP8.5 scenario. The agreement between the methods may suggest more confidence than is warranted since large uncertainties remain due to the lack of scenario-dependent projections from ice sheet dynamical models, particularly for mass loss from marine-based fast flowing outlet glaciers in Antarctica. This leads to an intrinsically hard to quantify fat tail in the probability distribution for global mean sea level rise. Thus our low probability upper limit of sea level projections cannot be considered definitive. Nevertheless, our upper limit of 180 cm for sea level rise by 2100 is based on both expert opinion and process studies and hence indicates that other lines of evidence are needed to justify a larger sea level rise this century.

  2. Sea-level-rise impacts: Questioning inevitable migration

    NASA Astrophysics Data System (ADS)

    Kniveton, Dominic

    2017-08-01

    It is assumed that sea-level rise due to climate change will be so severe that those living near sea level will be forced to relocate. However, new research around a series of islands that have suffered subsidence due to a recent earthquake suggests that instead, island residents remain and use a range of strategies to adapt to regular flooding.

  3. Separating decadal global water cycle variability from sea level rise.

    PubMed

    Hamlington, B D; Reager, J T; Lo, M-H; Karnauskas, K B; Leben, R R

    2017-04-20

    Under a warming climate, amplification of the water cycle and changes in precipitation patterns over land are expected to occur, subsequently impacting the terrestrial water balance. On global scales, such changes in terrestrial water storage (TWS) will be reflected in the water contained in the ocean and can manifest as global sea level variations. Naturally occurring climate-driven TWS variability can temporarily obscure the long-term trend in sea level rise, in addition to modulating the impacts of sea level rise through natural periodic undulation in regional and global sea level. The internal variability of the global water cycle, therefore, confounds both the detection and attribution of sea level rise. Here, we use a suite of observations to quantify and map the contribution of TWS variability to sea level variability on decadal timescales. In particular, we find that decadal sea level variability centered in the Pacific Ocean is closely tied to low frequency variability of TWS in key areas across the globe. The unambiguous identification and clean separation of this component of variability is the missing step in uncovering the anthropogenic trend in sea level and understanding the potential for low-frequency modulation of future TWS impacts including flooding and drought.

  4. Does Sea Level Change when a Floating Iceberg Melts?

    ERIC Educational Resources Information Center

    Lan, Boon Leong

    2010-01-01

    On the answer page to a recent "Figuring Physics" question, the cute mouse asks another question: "Does the [sea] water level change if the iceberg melts?" The conventional answer is "no." However, in this paper I will show through a simple analysis involving Archimedes' principle that the sea level will rise. The analysis shows the wrong…

  5. Sea level oscillations over minute timescales: a global perspective

    NASA Astrophysics Data System (ADS)

    Vilibic, Ivica; Sepic, Jadranka

    2016-04-01

    Sea level oscillations occurring over minutes to a few hours are an important contributor to sea level extremes, and a knowledge on their behaviour is essential for proper quantification of coastal marine hazards. Tsunamis, meteotsunamis, infra-gravity waves and harbour oscillations may even dominate sea level extremes in certain areas and thus pose a great danger for humans and coastal infrastructure. Aside for tsunamis, which are, due to their enormous impact to the coastlines, a well-researched phenomena, the importance of other high-frequency oscillations to the sea level extremes is still underrated, as no systematic long-term measurements have been carried out at a minute timescales. Recently, Intergovernmental Oceanographic Commission (IOC) established Sea Level Monitoring Facility portal (http://www.ioc-sealevelmonitoring.org), making 1-min sea level data publicly available for several hundred tide gauge sites in the World Ocean. Thereafter, a global assessment of oscillations over tsunami timescales become possible; however, the portal contains raw sea level data only, being unchecked for spikes, shifts, drifts and other malfunctions of instruments. We present a quality assessment of these data, estimates of sea level variances and contributions of high-frequency processes to the extremes throughout the World Ocean. This is accompanied with assessment of atmospheric conditions and processes which generate intense high-frequency oscillations.

  6. Glacial Isostatic Adjustment and Contemporary Sea Level Rise: An Overview

    NASA Astrophysics Data System (ADS)

    Spada, Giorgio

    2017-01-01

    Glacial isostatic adjustment (GIA) encompasses a suite of geophysical phenomena accompanying the waxing and waning of continental-scale ice sheets. These involve the solid Earth, the oceans and the cryosphere both on short (decade to century) and on long (millennia) timescales. In the framework of contemporary sea-level change, the role of GIA is particular. In fact, among the processes significantly contributing to contemporary sea-level change, GIA is the only one for which deformational, gravitational and rotational effects are simultaneously operating, and for which the rheology of the solid Earth is essential. Here, I review the basic elements of the GIA theory, emphasizing the connections with current sea-level changes observed by tide gauges and altimetry. This purpose is met discussing the nature of the "sea-level equation" (SLE), which represents the basis for modeling the sea-level variations of glacial isostatic origin, also giving access to a full set of geodetic variations associated with GIA. Here, the SLE is employed to characterize the remarkable geographical variability of the GIA-induced sea-level variations, which are often expressed in terms of "fingerprints". Using harmonic analysis, the spatial variability of the GIA fingerprints is compared to that of other components of contemporary sea-level change. In closing, some attention is devoted to the importance of the "GIA corrections" in the context of modern sea-level observations, based on tide gauges or satellite altimeters.

  7. Late Holocene sea-level change in Arctic Norway

    NASA Astrophysics Data System (ADS)

    Barnett, Robert L.; Gehrels, W. Roland; Charman, Dan J.; Saher, Margot H.; Marshall, William A.

    2015-01-01

    Relative sea-level data from the pre-industrial era are required for validating geophysical models of glacio-isostatic adjustment as well as for testing models used to make sea-level predictions based on future climate change scenarios. We present the first late Holocene (past ˜3300 years) relative sea-level reconstruction for northwestern Norway based on investigations in South Hinnøya in the Vesterålen - Lofoton archipelago. Sea-level changes are reconstructed from analyses of salt-marsh and estuarine sediments and the micro-organisms (foraminifera and testate amoebae) preserved within. The 'indicative meaning' of the microfauna is established from their modern distributions. Records are dated by radiocarbon, 201Pb, 137Cs and chemostratigraphical analyses. Our results show a continuous relative sea-level decline of 0.7-0.9 mm yr-1 for South Hinnøya during the late Holocene. The reconstruction extends the relative sea-level trend recorded by local tide gauge data which is only available for the past ˜25 years. Our reconstruction demonstrates that existing models of shoreline elevations and GIA overpredict sea-level positions during the late Holocene. We suggest that models might be adjusted in order to reconcile modelled and reconstructed sea-level changes and ultimately improve understanding of GIA in Fennoscandia.

  8. Uncertainties in sea level reconstructions due to GIA corrections

    NASA Astrophysics Data System (ADS)

    Jevrejeva, S.; Moore, J. C.; Grinsted, A.

    2012-12-01

    We use 1277 tide gauge records since 1807 to compose a global sea level reconstruction and analyse the evolution of sea level trend and acceleration. There is a good agreement between the rate of sea level rise (3.2 mm/yr) calculated from satellite altimetry and the rate of 3.1 mm/yr from tide gauge based reconstruction for the overlapping time period (1993-2009). The new reconstruction suggests a linear trend of 1.9 mm/yr during the 20th century, with only 1.5 mm/yr since 1960. Regional linear trends for 14 ocean basins since 1960 show the fastest sea level rise for the Arctic (3.8 mm/yr), Antarctica (3.5 mm/yr) and North West Pacific region (3.3 mm/yr). Choice of GIA correction is critical in the trends for the local and regional sea level, introducing up to 6 mm/yr uncertainties for individual tide gauge records, up to 2 mm/yr for regional curves and up to 0.8 mm/yr in global sea level reconstruction. We calculate an acceleration of 0.02 mm/yr in global sea level (1807-2010). In comparison the steric component of sea level shows and acceleration of 0.006 mm/yr 2 and mass loss of glaciers accelerates at 0. 003 mm/yr2 over 200 year long time series.

  9. Does Sea Level Change when a Floating Iceberg Melts?

    ERIC Educational Resources Information Center

    Lan, Boon Leong

    2010-01-01

    On the answer page to a recent "Figuring Physics" question, the cute mouse asks another question: "Does the [sea] water level change if the iceberg melts?" The conventional answer is "no." However, in this paper I will show through a simple analysis involving Archimedes' principle that the sea level will rise. The analysis shows the wrong…

  10. Arctic Sea Level During the Satellite Altimetry Era

    NASA Astrophysics Data System (ADS)

    Carret, A.; Johannessen, J. A.; Andersen, O. B.; Ablain, M.; Prandi, P.; Blazquez, A.; Cazenave, A.

    2017-01-01

    Results of the sea-level budget in the high latitudes (up to 80°N) and the Arctic Ocean during the satellite altimetry era. We investigate the closure of the sea-level budget since 2002 using two altimetry sea-level datasets based on the Envisat waveform retracking: temperature and salinity data from the ORAP5 reanalysis, and Gravity Recovery And Climate Experiment (GRACE) space gravimetry data to estimate the steric and mass components. Regional sea-level trends seen in the altimetry map, in particular over the Beaufort Gyre and along the eastern coast of Greenland, are of halosteric origin. However, in terms of regional average over the region ranging from 66°N to 80°N, the steric component contributes little to the observed sea-level trend, suggesting a dominant mass contribution in the Arctic region. This is confirmed by GRACE-based ocean mass time series that agree well with the altimetry-based sea-level time series. Direct estimate of the mass component is not possible prior to GRACE. Thus, we estimated the mass contribution from the difference between the altimetry-based sea level and the steric component. We also investigate the coastal sea level with tide gauge records. Twenty coupled climate models from the CMIP5 project are also used. The models lead us to the same conclusions concerning the halosteric origin of the trend patterns.

  11. Estuaries May Face Increased Parasitism as Sea Levels Rise

    NASA Astrophysics Data System (ADS)

    Wendel, JoAnna

    2014-12-01

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

  12. Future extreme sea level seesaws in the tropical Pacific

    PubMed Central

    Widlansky, Matthew J.; Timmermann, Axel; Cai, Wenju

    2015-01-01

    Global mean sea levels are projected to gradually rise in response to greenhouse warming. However, on shorter time scales, modes of natural climate variability in the Pacific, such as the El Niño–Southern Oscillation (ENSO), can affect regional sea level variability and extremes, with considerable impacts on coastal ecosystems and island nations. How these shorter-term sea level fluctuations will change in association with a projected increase in extreme El Niño and its atmospheric variability remains unknown. Using present-generation coupled climate models forced with increasing greenhouse gas concentrations and subtracting the effect of global mean sea level rise, we find that climate change will enhance El Niño–related sea level extremes, especially in the tropical southwestern Pacific, where very low sea level events, locally known as Taimasa, are projected to double in occurrence. Additionally, and throughout the tropical Pacific, prolonged interannual sea level inundations are also found to become more likely with greenhouse warming and increased frequency of extreme La Niña events, thus exacerbating the coastal impacts of the projected global mean sea level rise. PMID:26601272

  13. Time of emergence for regional sea-level change

    NASA Astrophysics Data System (ADS)

    Lyu, Kewei; Zhang, Xuebin; Church, John A.; Slangen, Aimée B. A.; Hu, Jianyu

    2014-11-01

    Determining the time when the climate change signal from increasing greenhouse gases exceeds and thus emerges from natural climate variability (referred to as the time of emergence, ToE) is an important climate change issue. Previous ToE studies were mainly focused on atmospheric variables. Here, based on three regional sea-level projection products available to 2100, which have increasing complexity in terms of included processes, we estimate the ToE for sea-level changes relative to the reference period 1986-2005. The dynamic sea level derived from ocean density and circulation changes alone leads to emergence over only limited regions. By adding the global-ocean thermal expansion effect, 50% of the ocean area will show emergence with rising sea level by the early-to-middle 2040s. Including additional contributions from land ice mass loss, land water storage change and glacial isostatic adjustment generally enhances the signal of regional sea-level rise (except in some regions with decreasing total sea levels), which leads to emergence over more than 50% of the ocean area by 2020. The ToE for total sea level is substantially earlier than that for surface air temperature and exhibits little dependence on the emission scenarios, which means that our society will face detectable sea-level change and its potential impacts earlier than surface air warming.

  14. Future extreme sea level seesaws in the tropical Pacific.

    PubMed

    Widlansky, Matthew J; Timmermann, Axel; Cai, Wenju

    2015-09-01

    Global mean sea levels are projected to gradually rise in response to greenhouse warming. However, on shorter time scales, modes of natural climate variability in the Pacific, such as the El Niño-Southern Oscillation (ENSO), can affect regional sea level variability and extremes, with considerable impacts on coastal ecosystems and island nations. How these shorter-term sea level fluctuations will change in association with a projected increase in extreme El Niño and its atmospheric variability remains unknown. Using present-generation coupled climate models forced with increasing greenhouse gas concentrations and subtracting the effect of global mean sea level rise, we find that climate change will enhance El Niño-related sea level extremes, especially in the tropical southwestern Pacific, where very low sea level events, locally known as Taimasa, are projected to double in occurrence. Additionally, and throughout the tropical Pacific, prolonged interannual sea level inundations are also found to become more likely with greenhouse warming and increased frequency of extreme La Niña events, thus exacerbating the coastal impacts of the projected global mean sea level rise.

  15. Improved estimates of global sea level change from Ice Sheets, glaciers and land water storage using GRACE

    NASA Astrophysics Data System (ADS)

    Velicogna, I.; Hsu, C. W.; Ciraci, E.; Sutterley, T. C.

    2015-12-01

    We use observations of time variable gravity from GRACE to estimate mass changes for the Antarctic and Greenland Ice Sheets, the Glaciers and Ice Caps (GIC) and land water storage for the time period 2002-2015 and evaluate their total contribution to sea level. We calculate regional sea level changes from these present day mass fluxes using an improved scaling factor for the GRACE data that accounts for the spatial and temporal variability of the observed signal. We calculate a separate scaling factor for the annual and the long-term components of the GRACE signal. To estimate the contribution of the GIC, we use a least square mascon approach and we re-analyze recent inventories to optimize the distribution of mascons and recover the GRACE signal more accurately. We find that overall, Greenland controls 43% of the global trend in eustatic sea level rise, 16% for Antarctica and 29% for the GIC. The contribution from the GIC is dominated by the mass loss of the Canadian Arctic Archipelago, followed by Alaska, Patagonia and the High Mountains of Asia. We report a marked increase in mass loss for the Canadian Arctic Archipelago. In Greenland, following the 2012 high summer melt, years 2013 and 2014 have slowed down the increase in mass loss, but our results will be updated with summer 2015 observations at the meeting. In Antarctica, the mass loss is still on the rise with increased contributions from the Amundsen Sea sector and surprisingly from the Wilkes Land sector of East Antarctica, including Victoria Land. Conversely, the Queen Maud Land sector experienced a large snowfall in 2009-2013 and has now resumed to a zero mass gain since 2013. We compare sea level changes from these GRACE derived mass fluxes after including the atmospheric and ocean loading signal with sea level change from satellite radar altimetry (AVISO) corrected for steric signal of the ocean using Argo measurements and find an excellent agreement in amplitude, phase and trend in these estimates

  16. Understanding Sea Level Change: A Physics Based Approach

    NASA Astrophysics Data System (ADS)

    Kim, K. Y.

    2014-12-01

    Sea level change is an issue of immense importance in conjunction with global warming. The advent of satellite measurements offers a unique opportunity to address the global patterns of sea level height change associated with global warming. The rate of sea level change, however, is still uncertain due to the relatively short length of the satellite measurements, which began in 1993. In the present study, the contribution of global warming was separated from natural variability via cyclostationary EOF analysis in a sea level reconstruction dataset covering 1950-2010. Global sea level change due to the warming signal is within the range of fluctuations of the global average sea level computed directly from the data but is much less contaminated by natural variability as in the globally averaged sea level heights. A quadratic polynomial fit to the global warming signal indicates that the rate of sea level rise has increased by 0.2 mm yr-1 per decade and is 1.3 mm yr-1 as of 2010. The current rate of sea level rise is lower than that estimated from the globally averaged sea level heights by 0.2 mm yr-1 but is in the 1s range of the estimate (1.3 - 1.8 mm yr-1). Separation of the global warming mode from natural variability allow us to estimate the magnitude of natural variability and the relative significance of sea level change due to global warming. It appears that the sea level change due to global warming is, in general, comparable to natural variability in magnitude so far. Notable exceptions are over the southern tropical Indian, equatorial Pacific, tropical Atlantic, and along the extensions of the western boundary currents. Sea level rise due to warming is expected to exceed several standard deviations of natural variability by 2060 over the majority of the world oceans. This implies that coastal regions will be much more prone to disasters (such as hurricanes) due to warming-induced sea level rise.

  17. Greenhouse effect, sea level rise, and coastal zone management

    SciTech Connect

    Titus, J.G.

    1986-01-01

    Increasing concentrations of carbon dioxide and other gases are expected to warm the earth several degrees in the next century by a mechanism known as the greenhouse effect. Such a warming could cause sea level to rise two to five feet by expanding ocean water, melting mountain glaciers, and perhaps eventually causing polar glaciers to melt and slide into the oceans. A rise in sea level of even three feet could cause substantial erosion of beaches and coastal wetlands, increased flooding, and intrusion of salt water into rivers, bays, and aquifer. Fortunately, many of the adverse consequences can be avoided by taking timely measures in anticipation of sea level rise. Nevertheless, many coastal zone managers are reluctant to take these measures until the prospect of sea level rise becomes more certain. This article examines the implications of future sea level rise and identifies anticipatory measures that may be appropriate today in spite of current uncertainties. 46 references, 4 figures, 1 table.

  18. Continuous assimilation of simulated Geosat altimetric sea level into an eddy-resolving numerical ocean model. I - Sea level differences. II - Referenced sea level differences

    NASA Technical Reports Server (NTRS)

    White, Warren B.; Tai, Chang-Kou; Holland, William R.

    1990-01-01

    The optimal interpolation method of Lorenc (1981) was used to conduct continuous assimilation of altimetric sea level differences from the simulated Geosat exact repeat mission (ERM) into a three-layer quasi-geostrophic eddy-resolving numerical ocean box model that simulates the statistics of mesoscale eddy activity in the western North Pacific. Assimilation was conducted continuously as the Geosat tracks appeared in simulated real time/space, with each track repeating every 17 days, but occurring at different times and locations within the 17-day period, as would have occurred in a realistic nowcast situation. This interpolation method was also used to conduct the assimilation of referenced altimetric sea level differences into the same model, performing the referencing of altimetric sea sevel differences by using the simulated sea level. The results of this dynamical interpolation procedure are compared with those of a statistical (i.e., optimum) interpolation procedure.

  19. 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.

  20. Eastern tropical Pacific vegetation response to rapid climate change and sea level rise: A new pollen record from the Gulf of Tehuantepec, southern Mexico

    NASA Astrophysics Data System (ADS)

    Hendy, I. L.; Minckley, T. A.; Whitlock, C.

    2016-08-01

    A 30,000-year-long pollen record from the Gulf of Tehuantepec, southern Mexico shows the varying influence of air temperature, precipitation and eustatic sea-level rise on changes in coastal and upland vegetation patterns. During the late-glacial period, pine-juniper forests grew in the Sierra Madre del Sur along the Pacific Slope with broadleaf forests present at low elevations. Coastal wetland and riparian vegetation were limited in distribution. Significant cooling associated with Heinrich 1 (17,000-15,000 cal yr BP) resulted in an expansion of pine-juniper woodland. By the time of Bølling-Allerød warming (14,700-13,000 cal yr BP), extensive mangrove forest development was assisted by sea-level rise and reduced precipitation associated with a more southerly position of the Intertropical Convergence Zone (ITCZ) than at present. Concurrently, the expansion of oak into pine woodlands was promoted by warmer conditions than before. Increased summer precipitation in the early Holocene and stabilizing sea levels limited mangrove forests along the coast and allowed mixed conifer and hardwood forest to become more widespread inland. The onset of a more seasonal climate, driven by a weakening of the Mexican monsoon and a southerly shift in ITCZ position led to the establishment of modern open forests of pine and oak after 4300 cal yr BP.

  1. Sea level rise and variability around Peninsular Malaysia

    NASA Astrophysics Data System (ADS)

    Tkalich, Pavel; Luu, Quang-Hung; Tay, Tze-Wei

    2014-05-01

    Peninsular Malaysia is bounded from the west by Malacca Strait and the Andaman Sea, both connected to the Indian Ocean, and from the east by South China Sea being largest marginal sea in the Pacific Basin. As a result, sea level along Peninsular Malaysia coast is assumed to be governed by various regional phenomena associated with the adjacent parts of the Indian and Pacific Oceans. At annual scale, sea level anomalies (SLAs) are generated by the Asian monsoon; interannual sea level variability is determined by the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD); whilst long term sea level trend is coordinated by the global climate change. To quantify the relative impacts of these multi-scale phenomena on sea level trend and variability surrounding the Peninsular Malaysia, long-term tide gauge record and satellite altimetry are used. During 1984-2011, relative sea level rise (SLR) rates in waters of Malacca Strait and eastern Peninsular Malaysia are found to be 2.4 ± 0.8 mm/yr and 2.7 ± 0.6 mm/yr, respectively. Discounting for their vertical land movements (0.8 ± 2.6 mm/yr and 0.9 ± 2.2 mm/yr, respectively), their pure SLR rates are 1.6 ± 3.4 mm/yr and 1.8 ± 2.8 mm/yr, respectively, which are lower than the global tendency. At interannual scale, ENSO affects sea level over the Malaysian east coast in the range of ± 5 cm with very high correlation coefficient. Meanwhile, IOD modulates sea level anomalies in the Malacca Strait in the range of ± 2 cm with high correlation coefficient. Interannual regional sea level drops are associated with El Niño events and positive phases of the IOD index; while the rises are correlated with La Niña episodes and the negative periods of the IOD index. Seasonally, SLAs are mainly monsoon-driven, in the order of 10-25 cm. Geographically, sea level responds differently to the monsoon: two cycles per year are observed in the Malacca Strait, presumably due to South Asian - Indian Monsoon; while single

  2. Satellite Altimeter Observations of Black Sea Level Variations

    NASA Technical Reports Server (NTRS)

    Korotaev, G. K.; Saenko, O. A.; Koblinsky, C. J.

    1998-01-01

    Satellite altimeter data from TOPEX/POSEIDON and ERS-1 are used to examine seasonal and mesoscale variability of the Black Sea level. Consistent processing procedures of the altimeter measurements make it possible to determine the dynamical Black Sea level with an rms accuracy about 3 cm. It is shown that the Black Sea circulation intensifies in the winter-spring seasons and attenuates in summer-autumn. The seasonal variability of sea level is accompanied by a radiation of Rossby waves from the eastern coast of the basin. Mesoscale oscillations of the dynamical sea level are found to vary spatially and temporarily. Usually, strong eddy intensity is associated with instabilities of the Rim Current. Away from this circulation feature, in the deep basin, mesoscale variability is much smaller. Mesoscale variability has a strong seasonal signal, which is out of phase with the strength of the Rim Current.

  3. Sea-Level Rise Impacts on Hudson River Marshes

    NASA Astrophysics Data System (ADS)

    Hooks, A.; Nitsche, F. O.

    2015-12-01

    The response of tidal marshes to increasing sea-level rise is uncertain. Tidal marshes can adapt to rising sea levels through vertical accretion and inland migration. Yet tidal marshes are vulnerable to submergence if the rate of sea-level rise exceeds the rate of accretion and if inland migration is limited by natural features or development. We studied how Piermont and Iona Island Marsh, two tidal marshes on the Hudson River, New York, would be affected by sea-level rise of 0.5m, 1m, and 1.5m by 2100. This study was based on the 2011-2012 Coastal New York LiDAR survey. Using GIS we mapped sea-level rise projections accounting for accretion rates and calculated the submerged area of the marsh. Based on the Hudson River National Estuarine Research Reserve Vegetation 2005 dataset, we studied how elevation zones based on vegetation distributions would change. To evaluate the potential for inland migration, we assessed land cover around each marsh using the National Land Cover Database 2011 Land Cover dataset and examined the slope beyond the marsh boundaries. With an accretion rate of 0.29cm/year and 0.5m of sea-level rise by 2100, Piermont Marsh would be mostly unchanged. With 1.5m of sea-level rise, 86% of Piermont Marsh would be flooded. For Iona Island Marsh with an accretion rate of 0.78cm/year, sea-level rise of 0.5m by 2100 would result in a 4% expansion while 1.5m sea-level rise would cause inundation of 17% of the marsh. The results indicate that Piermont and Iona Island Marsh may be able to survive rates of sea-level rise such as 0.5m by 2100 through vertical accretion. At rates of sea-level rise like 1.5m by 2100, vertical accretion cannot match sea-level rise, submerging parts of the marshes. High elevations and steep slopes limit Piermont and Iona Island Marsh's ability to migrate inland. Understanding the impacts of sea-level rise on Piermont and Iona Island Marsh allows for long-term planning and could motivate marsh conservation programs.

  4. Using Sea Level Change as a Climate Indicator

    NASA Astrophysics Data System (ADS)

    Masters, D. S.; Nerem, R. S.

    2014-12-01

    Sea level rise is one the more important risks due to climate change. Multiple satellite altimeters flying on the same repeating ground track have allowed estimation of global and regional sea level for the past 20 years, and the time series has yielded information about how sea level is responding to climate change. Due to the duration, consistency, and inter-calibration of the altimeter measurements, the time series is now considered a climate data record. The time series has also shown the strong dependence of sea level on interannual signals such as the ENSO and PDO. Global mean sea level change as estimated by the altimeters is arguably one of the most sensitive indicators of climate change because it varies almost entirely due to thermal expansion/contraction and the exchange of water between the land and oceans. Contributions to the latter include melting land ice and changes in the hydrologic cycle. While thermal expansion does not vary greatly on interannual time-scales, variations in the global hydrologic cycle and land ice melt can contribute to large variations in the sea level record. Isolating and understanding the causes and scales of these variations is important in interpreting the observed global and regional sea level change, especially for decision-makers assessing risk and planning for adaptation and/or mitigation. Since 1992, satellite altimeter measurements from the TOPEX/Poseidon and Jason missions, have been providing precise estimates of sea level change between ±66° latitude every 10 days. We have been using these measurements to monitor both global average and regional sea level change. The GRACE mission has provided monthly estimates of the time-varying gravity field for the last 10 years. These measurements can estimate variations in global ocean mass, mass changes in the polar ice sheets and mountain glaciers, as well as changes in the land surface water storage. These data sets can be used to inform us about the sea level change

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  6. Climate variabilities of sea level around the Korean Peninsula

    NASA Astrophysics Data System (ADS)

    Youn, Yong-Hoon; Oh, Im Sang; Park, Young-Hyang; Kim, Ki-Hyun

    2004-08-01

    In order to study the climate variabilities of the sea level around the Korean Peninsula, tidal data observed at local stations in Korea were compared against those obtained using TOPEX/POSEIDON (T/P) altimetric sea level data. In the course of our study, the amount of sea level rise was estimated using the tidal data from 9 stations selected by an anomaly coherency analysis. The results indicated that the sea level has risen by 0.28 cm yr-1 around the Korean Peninsula over the past two decades. The extent of such a rise is about two times higher than that of the global increase (0.1 0.2 cm yr-1). However, because most global warming effects occurred mainly over mid- and high-latitudes, this level of change appears to be realistic. According to the spectral analysis (at a spectral window of k = 2, k is the number of subdivisions), the decadal band of sea level variability is computed at 30% of the energy. Its spectral peak is found at 12.8 years. In the interannual band, the predominant sea level variability is in the 1.4 1.9-year band, with a sharp peak at 1.6 years. A secondary peak, although marginal, has a period of 2.2 years. Based on our estimates of sea level height from Topex/Poseidon, the quasi-biennial periodicity of 1.6 years is the representative interannual sea level variability in the seas adjacent to Korea. Trends vary greatly according to the geographical location, from a maximum of 1.0 cm yr-1 (the southern sector of the East Sea) to a minimum of 0.17 cm yr-1 (the northern sector of the East Sea). This is fairly consistent with the qualitative description already given with reference to the global map. As an analogue to the pattern seen in Korea, that of the Yellow Sea reveals practically the same trend as that of the adjacent seas (0.56 cm yr-1). However, in the case of TOPEX/POSEIDON (T/P) data, there is no clear evidence of a linkage between the interannual sea level variability around the Korean Peninsula and ENSO.

  7. Global mapping of nonseismic sea level oscillations at tsunami timescales

    PubMed Central

    Vilibić, Ivica; Šepić, Jadranka

    2017-01-01

    Present investigations of sea level extremes are based on hourly data measured at coastal tide gauges. The use of hourly data restricts existing global and regional analyses to periods larger than 2 h. However, a number of processes occur at minute timescales, of which the most ruinous are tsunamis. Meteotsunamis, hazardous nonseismic waves that occur at tsunami timescales over limited regions, may also locally dominate sea level extremes. Here, we show that nonseismic sea level oscillations at tsunami timescales (<2 h) may substantially contribute to global sea level extremes, up to 50% in low-tidal basins. The intensity of these oscillations is zonally correlated with mid-tropospheric winds at the 99% significance level, with the variance doubling from the tropics and subtropics to the mid-latitudes. Specific atmospheric patterns are found during strong events at selected locations in the World Ocean, indicating a globally predominant generation mechanism. Our analysis suggests that these oscillations should be considered in sea level hazard assessment studies. Establishing a strong correlation between nonseismic sea level oscillations at tsunami timescales and atmospheric synoptic patterns would allow for forecasting of nonseismic sea level oscillations for operational use, as well as hindcasting and projection of their effects under past, present and future climates. PMID:28098195

  8. Global mapping of nonseismic sea level oscillations at tsunami timescales

    NASA Astrophysics Data System (ADS)

    Vilibić, Ivica; Šepić, Jadranka

    2017-01-01

    Present investigations of sea level extremes are based on hourly data measured at coastal tide gauges. The use of hourly data restricts existing global and regional analyses to periods larger than 2 h. However, a number of processes occur at minute timescales, of which the most ruinous are tsunamis. Meteotsunamis, hazardous nonseismic waves that occur at tsunami timescales over limited regions, may also locally dominate sea level extremes. Here, we show that nonseismic sea level oscillations at tsunami timescales (<2 h) may substantially contribute to global sea level extremes, up to 50% in low-tidal basins. The intensity of these oscillations is zonally correlated with mid-tropospheric winds at the 99% significance level, with the variance doubling from the tropics and subtropics to the mid-latitudes. Specific atmospheric patterns are found during strong events at selected locations in the World Ocean, indicating a globally predominant generation mechanism. Our analysis suggests that these oscillations should be considered in sea level hazard assessment studies. Establishing a strong correlation between nonseismic sea level oscillations at tsunami timescales and atmospheric synoptic patterns would allow for forecasting of nonseismic sea level oscillations for operational use, as well as hindcasting and projection of their effects under past, present and future climates.

  9. Global mapping of nonseismic sea level oscillations at tsunami timescales.

    PubMed

    Vilibić, Ivica; Šepić, Jadranka

    2017-01-18

    Present investigations of sea level extremes are based on hourly data measured at coastal tide gauges. The use of hourly data restricts existing global and regional analyses to periods larger than 2 h. However, a number of processes occur at minute timescales, of which the most ruinous are tsunamis. Meteotsunamis, hazardous nonseismic waves that occur at tsunami timescales over limited regions, may also locally dominate sea level extremes. Here, we show that nonseismic sea level oscillations at tsunami timescales (<2 h) may substantially contribute to global sea level extremes, up to 50% in low-tidal basins. The intensity of these oscillations is zonally correlated with mid-tropospheric winds at the 99% significance level, with the variance doubling from the tropics and subtropics to the mid-latitudes. Specific atmospheric patterns are found during strong events at selected locations in the World Ocean, indicating a globally predominant generation mechanism. Our analysis suggests that these oscillations should be considered in sea level hazard assessment studies. Establishing a strong correlation between nonseismic sea level oscillations at tsunami timescales and atmospheric synoptic patterns would allow for forecasting of nonseismic sea level oscillations for operational use, as well as hindcasting and projection of their effects under past, present and future climates.

  10. Decadal sea level variability in the East China Sea linked to the North Pacific Gyre Oscillation

    NASA Astrophysics Data System (ADS)

    Moon, Jae-Hong; Song, Y. Tony

    2017-07-01

    In view of coastal community's need for adapting to sea level rise (SLR), understanding and predicting regional variability on decadal to longer time scales still remain a challenging issue in SLR research. Here, we have examined the low-frequency sea level signals in the East China Sea (ECS) from the 50-year hindcast of a non-Boussinesq ocean model in comparison with data sets from altimeters, tide-gauges, and steric sea level produced by in-situ profiles. It is shown that the mean sea levels in the ECS represent significant decadal fluctuations over the past 50 years, with a multi-decadal trend shift since the mid-1980s compared to the preceding 30 years. The decadal fluctuations in sea level are more closely linked to the North Pacific Gyre Oscillation (NPGO) rather than the Pacific Decadal Oscillation, which reflects the multi-decadal trend shift. A composite analysis indicates that wind patterns associated with the NPGO is shown to control the decadal variability of the western subtropical North Pacific. A positive NPGO corresponds to cyclonic wind stress curl anomaly in the western subtropical regions that results in a higher sea level in the ECS, particularly along the continental shelf, and lower sea levels off the ECS. The reverse occurs in years of negative NPGO.

  11. Improving sea level simulation in Mediterranean regional climate models

    NASA Astrophysics Data System (ADS)

    Adloff, Fanny; Jordà, Gabriel; Somot, Samuel; Sevault, Florence; Arsouze, Thomas; Meyssignac, Benoit; Li, Laurent; Planton, Serge

    2017-08-01

    For now, the question about future sea level change in the Mediterranean remains a challenge. Previous climate modelling attempts to estimate future sea level change in the Mediterranean did not meet a consensus. The low resolution of CMIP-type models prevents an accurate representation of important small scales processes acting over the Mediterranean region. For this reason among others, the use of high resolution regional ocean modelling has been recommended in literature to address the question of ongoing and future Mediterranean sea level change in response to climate change or greenhouse gases emissions. Also, it has been shown that east Atlantic sea level variability is the dominant driver of the Mediterranean variability at interannual and interdecadal scales. However, up to now, long-term regional simulations of the Mediterranean Sea do not integrate the full sea level information from the Atlantic, which is a substantial shortcoming when analysing Mediterranean sea level response. In the present study we analyse different approaches followed by state-of-the-art regional climate models to simulate Mediterranean sea level variability. Additionally we present a new simulation which incorporates improved information of Atlantic sea level forcing at the lateral boundary. We evaluate the skills of the different simulations in the frame of long-term hindcast simulations spanning from 1980 to 2012 analysing sea level variability from seasonal to multidecadal scales. Results from the new simulation show a substantial improvement in the modelled Mediterranean sea level signal. This confirms that Mediterranean mean sea level is strongly influenced by the Atlantic conditions, and thus suggests that the quality of the information in the lateral boundary conditions (LBCs) is crucial for the good modelling of Mediterranean sea level. We also found that the regional differences inside the basin, that are induced by circulation changes, are model-dependent and thus not

  12. 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.

  13. 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

  14. Mapping the Causes and Impacts of Decadal Sea Level Variability

    NASA Astrophysics Data System (ADS)

    Hamlington, B.

    2016-12-01

    Under a warming climate, increased variability in the water cycle and changes in precipitation patterns over land are expected to occur, subsequently impacting the terrestrial water cycle/balance. On global scales, such changes in terrestrial water storage (TWS) will be reflected in the water contained in the ocean and manifest as sea level variations. Thus, naturally occurring climate-driven water storage variability can potentially serve to obscure the long-term trend in sea level rise, in addition to modulating the impacts of sea level rise through natural periodic undulation in regional and global sea level. Here, we use a broad suite of observations, focusing on those from satellites in particular, to examine the link between sea level variability and TWS on decadal timescales. We find that decadal sea level variability centered in the Pacific Ocean is closely tied to the occurrence of extended periods of increased and decreased TWS in many areas across the globe. Identifying this variability has important implications for uncovering the background trend in sea level, and we examine how separating decadal variability from the satellite altimetry record impacts the ability the estimate an acceleration from the relatively short satellite record. The results here also demonstrate that precipitation-driven variability that is regional in nature can lead to decadal changes in the exchange of water between land and ocean that is measurable on global scales. While on a basic level the resulting relationship between global mean sea level, precipitation and TWS is not unexpected, extracting a signal from multiple climate variables that persists for a decade and undergoes regular shifts in phase as evidenced by the historical record establishes an important link between sea level, TWS, and precipitation that can be tracked and monitored in the future.

  15. Sea level rise with warming above 2 degree

    NASA Astrophysics Data System (ADS)

    Jevrejeva, Svetlana; Jackson, Luke; Riva, Riccardo; Grinsted, Aslak; Moore, John

    2017-04-01

    Holding the increase in the global average temperature to below 2 °C above pre-industrial levels, and pursuing efforts to limit the temperature increase to 1.5 °C, has been agreed by the representatives of the 196 parties of United Nations, as an appropriate threshold beyond which climate change risks become unacceptably high. Sea level rise is one of the most damaging aspects of warming climate for the more than 600 million people living in low-elevation coastal areas less than 10 meters above sea level. Fragile coastal ecosystems and increasing concentrations of population and economic activity in coastal areas, are reasons why future sea level rise is one of the most damaging aspects of the warming climate. Furthermore, sea level is set to continue to rise for centuries after greenhouse gas emissions concentrations are stabilised due to system inertia and feedback time scales. Impact, risk, adaptation policies and long-term decision making in coastal areas depend on regional and local sea level rise projections and local projections can differ substantially from the global one. Here we provide probabilistic sea level rise projections for the global coastline with warming above the 2 degree goal. A warming of 2°C makes global ocean rise on average by 20 cm, but more than 90% of coastal areas will experience greater rises, 40 cm along the Atlantic coast of North America and Norway, due to ocean dynamics. If warming continues above 2°C, then by 2100 sea level will rise with speeds unprecedented throughout human civilization, reaching 0.9 m (median), and 80% of the global coastline will exceed the global ocean sea level rise upper 95% confidence limit of 1.8 m. Coastal communities of rapidly expanding cities in the developing world, small island states, and vulnerable tropical coastal ecosystems will have a very limited time after mid-century to adapt to sea level rises.

  16. Past sea level reconstruction and variability of sea level trend patterns over 1970-2001 in the Mediterranean Sea basin derived from Altimetry and 2 long OGCM runs.

    NASA Astrophysics Data System (ADS)

    Meyssignac, Benoit; Cazenave, Anny; Morrow, Rosemary; Marcos, Marta; Calafat, Francisco; Llovel, William

    2010-05-01

    For the past decades, there are no direct basin-scale sea level observations concerning the spatial sea level patterns and their evolution in the Mediterranean Sea. In order to understand physical processes driving sea level variability it is important to know the dominant modes of regional variability on interannual/decadal/multidecadal time scale in the Mediterranean basin. It is also of interest for assessing ocean circulation models dedicated to the Mediterranean Sea. For these purposes, we have developed a reconstruction method of past Mediterranean sea level (since 1970) that combines long tide gauge records of limited spatial coverage and 2-D sea level patterns based on the AVISO altimetry dataset and on runs from two different Ocean General Circulation Models (OGCMs). In the latter case, we use runs from the ORCA05 model (without data assimilation) over 1958-2005 available from the DRAKKAR project and the SODA reanalysis over 1958-2005 available from GODAE (Carton et al., 2008), assimilating all available in situ temperature, salinity and sea level data. We also perform the past sea level reconstruction over the Mediterranean Sea using 2-D spatial patterns from satellite altimetry. The three sea level reconstructions are inter-compared, together with results from a published study (Calafat and Gomis, 2009). The dominant modes of temporal variability are discussed and sea level hindcasts at tide gauge sites not used in the analysis are compared to actual observations. Comparisons with steric sea level patterns based on in situ hydrographic data are also presented and discussed with regard to the conclusions of past studies based on tide gauge records analysis. .

  17. Sea Level Data Archaeology for the Global Sea Level Observing System (GLOSS)

    NASA Astrophysics Data System (ADS)

    Bradshaw, Elizabeth; Matthews, Andy; Rickards, Lesley; Jevrejeva, Svetlana

    2015-04-01

    The Global Sea Level Observing System (GLOSS) was set up in 1985 to collect long term tide gauge observations and has carried out a number of data archaeology activities over the past decade, including sending member organisations questionnaires to report on their repositories. The GLOSS Group of Experts (GLOSS GE) is looking to future developments in sea level data archaeology and will provide its user community with guidance on finding, digitising, quality controlling and distributing historic records. Many records may not be held in organisational archives and may instead by in national libraries, archives and other collections. GLOSS will promote a Citizen Science approach to discovering long term records by providing tools for volunteers to report data. Tide gauge data come in two different formats, charts and hand-written ledgers. Charts are paper analogue records generated by the mechanical instrument driving a pen trace. Several GLOSS members have developed software to automatically digitise these charts and the various methods were reported in a paper on automated techniques for the digitization of archived mareograms, delivered to the GLOSS GE 13th meeting. GLOSS is creating a repository of software for scanning analogue charts. NUNIEAU is the only publically available software for digitising tide gauge charts but other organisations have developed their own tide gauge digitising software that is available internally. There are several other freely available software packages that convert image data to numerical values. GLOSS could coordinate a comparison study of the various different digitising software programs by: Sending the same charts to each organisation and asking everyone to digitise them using their own procedures Comparing the digitised data Providing recommendations to the GLOSS community The other major form of analogue sea level data is handwritten ledgers, which are usually observations of high and low waters, but sometimes contain higher

  18. Lower bounds to future sea-level rise

    NASA Astrophysics Data System (ADS)

    Zecca, Antonio; Chiari, Luca

    2012-12-01

    Sea-level rise is among the most important changes expected as a consequence of anthropogenic global warming. Climate model-based projections made until the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) yield a 21st century rise spanning nearly 20-60 cm. However, it is known that current climate models are likely to underestimate sea-level change in response to rapid climatic variations. Recent alternative semi-empirical approaches predict a much higher sea-level rise than the IPCC AR4 projections. Nevertheless, the underway depletion of conventional fossil fuels might, at least in principle, constrain future fossil CO2 emissions and, in turn, affect also the extent of sea-level rise. Here we project 2000-2200 sea-level rise with a semi-empirical method coupled to a simple climate model that is run under a range of fossil-fuel exhaustion scenarios. We find that, in spite of fossil-fuel depletion, sea level is predicted to rise by at least ~ 80 cm at the end of this century and is expected to continue rising for at least the next two hundred years. The present results support the need for prompt and substantial emission cuts in order to slow down future sea-level rise and implement adaptation measures.

  19. Sea level change: lessons from the geologic record

    USGS Publications Warehouse

    ,

    1995-01-01

    Rising sea level is potentially one of the most serious impacts of climatic change. Even a small sea level rise would have serious economic consequences because it would cause extensive damage to the world's coastal regions. Sea level can rise in the future because the ocean surface can expand due to warming and because polar ice sheets and mountain glaciers can melt, increasing the ocean's volume of water. Today, ice caps on Antarctica and Greenland contain 91 and 8 percent of the world's ice, respectively. The world's mountain glaciers together contain only about 1 percent. Melting all this ice would raise sea level about 80 meters. Although this extreme scenario is not expected, geologists know that sea level can rise and fall rapidly due to changing volume of ice on continents. For example, during the last ice age, about 18,000 years ago, continental ice sheets contained more than double the modem volume of ice. As ice sheets melted, sea level rose 2 to 3 meters per century, and possibly faster during certain times. During periods in which global climate was very warm, polar ice was reduced and sea level was higher than today.

  20. The Phanerozoic record of global sea-level change.

    PubMed

    Miller, Kenneth G; Kominz, Michelle A; Browning, James V; Wright, James D; Mountain, Gregory S; Katz, Miriam E; Sugarman, Peter J; Cramer, Benjamin S; Christie-Blick, Nicholas; Pekar, Stephen F

    2005-11-25

    We review Phanerozoic sea-level changes [543 million years ago (Ma) to the present] on various time scales and present a new sea-level record for the past 100 million years (My). Long-term sea level peaked at 100 +/- 50 meters during the Cretaceous, implying that ocean-crust production rates were much lower than previously inferred. Sea level mirrors oxygen isotope variations, reflecting ice-volume change on the 10(4)- to 10(6)-year scale, but a link between oxygen isotope and sea level on the 10(7)-year scale must be due to temperature changes that we attribute to tectonically controlled carbon dioxide variations. Sea-level change has influenced phytoplankton evolution, ocean chemistry, and the loci of carbonate, organic carbon, and siliciclastic sediment burial. Over the past 100 My, sea-level changes reflect global climate evolution from a time of ephemeral Antarctic ice sheets (100 to 33 Ma), through a time of large ice sheets primarily in Antarctica (33 to 2.5 Ma), to a world with large Antarctic and large, variable Northern Hemisphere ice sheets (2.5 Ma to the present).

  1. On the relationship between sea level and Spartina alterniflora production

    USGS Publications Warehouse

    Kirwan, Matthew L.; Christian, Robert R.; Blum, Linda K.; Brinson, Mark M.

    2012-01-01

    A positive relationship between interannual sea level and plant growth is thought to stabilize many coastal landforms responding to accelerating rates of sea level rise. Numerical models of delta growth, tidal channel network evolution, and ecosystem resilience incorporate a hump-shaped relationship between inundation and plant primary production, where vegetation growth increases with sea level up to an optimum water depth or inundation frequency. In contrast, we use decade-long measurements of Spartina alterniflora biomass in seven coastal Virginia (USA) marshes to demonstrate that interannual sea level is rarely a primary determinant of vegetation growth. Although we find tepid support for a hump-shaped relationship between aboveground production and inundation when marshes of different elevation are considered, our results suggest that marshes high in the intertidal zone and low in relief are unresponsive to sea level fluctuations. We suggest existing models are unable to capture the behavior of wetlands in these portions of the landscape, and may underestimate their vulnerability to sea level rise because sea level rise will not be accompanied by enhanced plant growth and resultant sediment accumulation.

  2. Upper Limit for Sea Level Projections by 2100

    NASA Astrophysics Data System (ADS)

    Jevrejeva, S.; Grinsted, A.; Moore, J. C.

    2014-12-01

    With more than 150 million people living within 1 m of high tide future sea level rise is one of the most damaging aspects of warming climate. The latest Intergovernmental Panel on Climate Change report (AR5 IPCC) noted that a 0.5 m rise in mean sea level will result in a dramatic increase the frequency of high water extremes - by an order of magnitude, or more in some regions. Thus the flood threat to the rapidly growing urban populations and associated infrastructure in coastal areas are major concerns for society. Hence, impact assessment, risk management, adaptation strategy and long-term decision making in coastal areas depend on projections of mean sea level and crucially its low probability, high impact, upper range. We construct the probability density function of global sea level at 2100, estimating that sea level rises larger than 180 cm are less than 5% probable. An upper limit for global sea level rise of 190 cm is assembled by summing the highest estimates of individual sea level rise components simulated by process based models with the RCP8.5 scenario. The agreement between the methods may suggest more confidence than is warranted since large uncertainties remain due to the lack of scenario-dependent projections from ice sheet dynamical models, particularly for mass loss from marine-based fast flowing outlet glaciers in Antarctica.

  3. Upper Limit for Sea Level Projections by 2100

    NASA Astrophysics Data System (ADS)

    Jevrejeva, Svetlana; Grinsted, Aslak; Moore, John

    2015-04-01

    With more than 150 million people living within 1 m of high tide future sea level rise is one of the most damaging aspects of warming climate. The latest Intergovernmental Panel on Climate Change report (AR5 IPCC) noted that a 0.5 m rise in mean sea level will result in a dramatic increase the frequency of high water extremes - by an order of magnitude, or more in some regions. Thus the flood threat to the rapidly growing urban populations and associated infrastructure in coastal areas are major concerns for society. Hence, impact assessment, risk management, adaptation strategy and long-term decision making in coastal areas depend on projections of mean sea level and crucially its low probability, high impact, upper range. We construct the probability density function of global sea level at 2100, estimating that sea level rises larger than 180 cm are less than 5% probable. An upper limit for global sea level rise of 190 cm is assembled by summing the highest estimates of individual sea level rise components simulated by process based models with the RCP8.5 scenario. The agreement between the methods may suggest more confidence than is warranted since large uncertainties remain due to the lack of scenario-dependent projections from ice sheet dynamical models, particularly for mass loss from marine-based fast flowing outlet glaciers in Antarctica.

  4. 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

  5. Late Holocene sea level changes and tectonic movements inferred from fossil diatom assemblages in Tainohama, Tokushima prefecture, Japan

    NASA Astrophysics Data System (ADS)

    Chiba, T.; Fujino, S.; Kobori, E.

    2014-12-01

    freshwater species, suggesting paleo-sea level changes. The sea level in this area declined gradually to modern sea level from +50cm higher level than modern by eustatic sea level fall during the late Holocene (Sato 2014), thus the fluctuations suggest co-seismic or inter-seismic crustal movements of the past interplate earthquakes along the Nankai Trough.

  6. Analysis of Sea Level Rise in Singapore Strait

    NASA Astrophysics Data System (ADS)

    Tkalich, Pavel; Luu, Quang-Hung

    2013-04-01

    Sea level in Singapore Strait is governed by various scale phenomena, from global to local. Global signals are dominated by the climate change and multi-decadal variability and associated sea level rise; at regional scale seasonal sea level variability is caused by ENSO-modulated monsoons; locally, astronomic tides are the strongest force. Tide gauge records in Singapore Strait are analyzed to derive local sea level trend, and attempts are made to attribute observed sea level variability to phenomena at various scales, from global to local. It is found that at annual scale, sea level anomalies in Singapore Strait are quasi-periodic, of the order of ±15 cm, the highest during northeast monsoon and the lowest during southwest monsoon. Interannual regional sea level falls are associated with El Niño events, while the rises are related to La Niña episodes; both variations are in the range of ±9 cm. At multi-decadal scale, sea level in Singapore Strait has been rising at the rate 1.2-1.9 mm/year for the period 1975-2009, 2.0±0.3 mm/year for 1984-2009, and 1.3-4.7 mm/year for 1993-2009. When compared with the respective global trends of 2.0±0.3, 2.4, and 2.8±0.8 mm/year, Singapore Strait sea level rise trend was weaker at the earlier period and stronger at the recent decade.

  7. Subsidence and Relative Sea-level Rise in Threatened Deltas

    NASA Astrophysics Data System (ADS)

    Syvitski, J. P.; Higgins, S.

    2014-12-01

    In determining the risk lowland deltaic topography, as threatened by sea level rise and land subsidence, a number of important processes must be evaluated. Sea level rise is a global process but with local manifestations. Asian deltas have been experiencing higher rates of sea level rise due to the steric impact on dynamic (ocean) topography. Other large scale geophysical impacts on relative sea level at the local scale include the isostatic and flexural response to Holocene sea level history, Holocene sediment loads, and in former ice sheet zones --- glacial rebound. Tectonism does play a role on relative sea level rise, particularly in South America where the Eastern coastline, particularly Argentina, is rising relative to regional sea levels. Subsidence is impacted by both natural ground compaction, and accelerated compaction due to, for example, peat oxidation that often has a human driver (e.g. swamp reclammation). Subsidence is also impacted by the extraction of deeper deposits of petroleum and water. Rates of delta subsidence vary widely, depending on the magnitude of the anthropogenic driver, from a few mm/y to 100's of mm/y. Ground water withdrawal is the dominant reason behind much of the world's coastal subsidence, with important exceptions. On average subsidence rates (all causes) now contribute to local sea level innundations at rates four times faster then sea level is rising. New technologies, particularly InSAR and GPS methods, can often pin point the local cause (e.g. water withdrawl for agriculture versus for aquaculture). Subsurface soil or rock heterogeneity, and other very local geological patterns such as historical river pathways, also influence the temporal and spatial patterns associated with delta subsidence.

  8. Precise mean sea level measurements using the Global Positioning System

    NASA Technical Reports Server (NTRS)

    Kelecy, Thomas M.; Born, George H.; Parke, Michael E.; Rocken, Christian

    1994-01-01

    This paper describes the results of a sea level measurement test conducted off La Jolla, California, in November of 1991. The purpose of this test was to determine accurate sea level measurements using a Global Positioning System (GPS) equipped buoy. These measurements were intended to be used as the sea level component for calibration of the ERS 1 satellite altimeter. Measurements were collected on November 25 and 28 when the ERS 1 satellite overflew the calibration area. Two different types of buoys were used. A waverider design was used on November 25 and a spar design on November 28. This provided the opportunity to examine how dynamic effects of the measurement platform might affect the sea level accuracy. The two buoys were deployed at locations approximately 1.2 km apart and about 15 km west of a reference GPS receiver located on the rooftop of the Institute of Geophysics and Planetary Physics at the Scripps Institute of Oceanography. GPS solutions were computed for 45 minutes on each day and used to produce two sea level time series. An estimate of the mean sea level at both locations was computed by subtracting tide gage data collected at the Scripps Pier from the GPS-determined sea level measurements and then filtering out the high-frequency components due to waves and buoy dynamics. In both cases the GPS estimate differed from Rapp's mean altimetric surface by 0.06 m. Thus, the gradient in the GPS measurements matched the gradient in Rapp's surface. These results suggest that accurate sea level can be determined using GPS on widely differing platforms as long as care is taken to determine the height of the GPS antenna phase center above water level. Application areas include measurement of absolute sea level, of temporal variations in sea level, and of sea level gradients (dominantly the geoid). Specific applications would include ocean altimeter calibration, monitoring of sea level in remote regions, and regional experiments requiring spatial and

  9. Precise mean sea level measurements using the Global Positioning System

    NASA Technical Reports Server (NTRS)

    Kelecy, Thomas M.; Born, George H.; Parke, Michael E.; Rocken, Christian

    1994-01-01

    This paper describes the results of a sea level measurement test conducted off La Jolla, California, in November of 1991. The purpose of this test was to determine accurate sea level measurements using a Global Positioning System (GPS) equipped buoy. These measurements were intended to be used as the sea level component for calibration of the ERS 1 satellite altimeter. Measurements were collected on November 25 and 28 when the ERS 1 satellite overflew the calibration area. Two different types of buoys were used. A waverider design was used on November 25 and a spar design on November 28. This provided the opportunity to examine how dynamic effects of the measurement platform might affect the sea level accuracy. The two buoys were deployed at locations approximately 1.2 km apart and about 15 km west of a reference GPS receiver located on the rooftop of the Institute of Geophysics and Planetary Physics at the Scripps Institute of Oceanography. GPS solutions were computed for 45 minutes on each day and used to produce two sea level time series. An estimate of the mean sea level at both locations was computed by subtracting tide gage data collected at the Scripps Pier from the GPS-determined sea level measurements and then filtering out the high-frequency components due to waves and buoy dynamics. In both cases the GPS estimate differed from Rapp's mean altimetric surface by 0.06 m. Thus, the gradient in the GPS measurements matched the gradient in Rapp's surface. These results suggest that accurate sea level can be determined using GPS on widely differing platforms as long as care is taken to determine the height of the GPS antenna phase center above water level. Application areas include measurement of absolute sea level, of temporal variations in sea level, and of sea level gradients (dominantly the geoid). Specific applications would include ocean altimeter calibration, monitoring of sea level in remote regions, and regional experiments requiring spatial and

  10. Impact of global seismicity on sea level change assessment

    NASA Astrophysics Data System (ADS)

    Melini, D.; Piersanti, A.

    2006-03-01

    We analyze the effect of seismic activity on sea level variations by computing the time-dependent vertical crustal movement and geoid change due to coseismic deformations and postseismic relaxation effects. Seismic activity can affect both the absolute sea level, changing the Earth's gravity field and hence the geoid height, and the relative sea level (RSL), i.e., the radial distance between seafloor and geoid level. By using comprehensive seismic catalogs we assess the net effect of seismicity on tidal relative sea level measurements as well as on the global oceanic surfaces, and we obtain an estimate of absolute sea level variations of seismic origin. We modified the approach adopted in our previous analysis, considering the issue of water volume conservation by applying the sealevel equation, and we improved our computational methods, enabling us to evaluate the effect of an extremely large number of earthquakes on large grids covering the whole oceanic surface. These new potentialities allow us to perform more detailed investigations and to discover a quantitative explanation for the overall tendency of earthquakes to produce a positive global relative sea level variation. Our results confirm the finding of a previous analysis that on a global scale most of the signal is associated with a few giant thrust events and that RSL estimates obtained using tide gauge data can be sensibly affected by the seismically driven sea level signal. The recent measures of sea level obtained by satellite altimetry show a wide regional variation of sea level trends over the oceanic surface, with the largest deviations from the mean trend occurring in tectonically active regions. While our estimates of average absolute sea level variations turn out to be orders of magnitude smaller than the satellite-measured variations, we can still argue that the mass redistribution associated with aseismic tectonic processes may contribute to the observed regional variability of sea level

  11. Sea water intrusion by sea-level rise: scenarios for the 21st century.

    PubMed

    Loáiciga, Hugo A; Pingel, Thomas J; Garcia, Elizabeth S

    2012-01-01

    This study presents a method to assess the contributions of 21st-century sea-level rise and groundwater extraction to sea water intrusion in coastal aquifers. Sea water intrusion is represented by the landward advance of the 10,000 mg/L iso-salinity line, a concentration of dissolved salts that renders groundwater unsuitable for human use. A mathematical formulation of the resolution of sea water intrusion among its causes was quantified via numerical simulation under scenarios of change in groundwater extraction and sea-level rise in the 21st century. The developed method is illustrated with simulations of sea water intrusion in the Seaside Area sub-basin near the City of Monterey, California (USA), where predictions of mean sea-level rise through the early 21st century range from 0.10 to 0.90 m due to increasing global mean surface temperature. The modeling simulation was carried out with a state-of-the-art numerical model that accounts for the effects of salinity on groundwater density and can approximate hydrostratigraphic geometry closely. Simulations of sea water intrusion corresponding to various combinations of groundwater extraction and sea-level rise established that groundwater extraction is the predominant driver of sea water intrusion in the study aquifer. The method presented in this work is applicable to coastal aquifers under a variety of other scenarios of change not considered in this work. For example, one could resolve what changes in groundwater extraction and/or sea level would cause specified levels of groundwater salinization at strategic locations and times.

  12. An alternative to reduction of surface pressure to sea level

    NASA Technical Reports Server (NTRS)

    Deardorff, J. W.

    1982-01-01

    The pitfalls of the present method of reducing surface pressure to sea level are reviewed, and an alternative, adjusted pressure, P, is proposed. P is obtained from solution of a Poisson equation over a continental region, using the simplest boundary condition along the perimeter or coastline where P equals the sea level pressure. The use of P would avoid the empiricisms and disadvantages of pressure reduction to sea level, and would produce surface pressure charts which depict the true geostrophic wind at the surface.

  13. Coastal Impact Underestimated From Rapid Sea Level Rise

    NASA Astrophysics Data System (ADS)

    Anderson, John; Milliken, Kristy; Wallace, Davin; Rodriguez, Antonio; Simms, Alexander

    2010-06-01

    A primary effect of global warming is accelerated sea level rise, which will eventually drown low-lying coastal areas, including some of the world's most populated cities. Predictions from the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) suggest that sea level may rise by as much as 0.6 meter by 2100 [Solomon et al., 2007]. However, uncertainty remains about how projected melting of the Greenland and Antarctic ice sheets will contribute to sea level rise. Further, considerable variability is introduced to these calculations due to coastal subsidence, especially along the northern Gulf of Mexico (see http://tidesandcurrents.noaa.gov/sltrends/sltrends.shtml).

  14. Sea level trend and variability around Peninsular Malaysia

    NASA Astrophysics Data System (ADS)

    Luu, Q. H.; Tkalich, P.; Tay, T. W.

    2015-08-01

    Sea level rise due to climate change is non-uniform globally, necessitating regional estimates. Peninsular Malaysia is located in the middle of Southeast Asia, bounded from the west by the Malacca Strait, from the east by the South China Sea (SCS), and from the south by the Singapore Strait. The sea level along the peninsula may be influenced by various regional phenomena native to the adjacent parts of the Indian and Pacific oceans. To examine the variability and trend of sea level around the peninsula, tide gauge records and satellite altimetry are analyzed taking into account vertical land movements (VLMs). At annual scale, sea level anomalies (SLAs) around Peninsular Malaysia on the order of 5-25 cm are mainly monsoon driven. Sea levels at eastern and western coasts respond differently to the Asian monsoon: two peaks per year in the Malacca Strait due to South Asian-Indian monsoon; an annual cycle in the remaining region mostly due to the East Asian-western Pacific monsoon. At interannual scale, regional sea level variability in the range of ±6 cm is correlated with El Nino-Southern Oscillation (ENSO). SLAs in the Malacca Strait side are further correlated with the Indian Ocean Dipole (IOD) in the range of ±5 cm. Interannual regional sea level falls are associated with El Nino events and positive phases of IOD, whilst rises are correlated with La Nina episodes and negative values of the IOD index. At seasonal to interannual scales, we observe the separation of the sea level patterns in the Singapore Strait, between the Raffles Lighthouse and Tanjong Pagar tide stations, likely caused by a dynamic constriction in the narrowest part. During the observation period 1986-2013, average relative rates of sea level rise derived from tide gauges in Malacca Strait and along the east coast of the peninsula are 3.6±1.6 and 3.7±1.1 mm yr-1, respectively. Correcting for respective VLMs (0.8±2.6 and 0.9±2.2 mm yr-1), their corresponding geocentric sea level rise rates

  15. Sea-level variability over five glacial cycles.

    PubMed

    Grant, K M; Rohling, E J; Ramsey, C Bronk; Cheng, H; Edwards, R L; Florindo, F; Heslop, D; Marra, F; Roberts, A P; Tamisiea, M E; Williams, F

    2014-09-25

    Research on global ice-volume changes during Pleistocene glacial cycles is hindered by a lack of detailed sea-level records for time intervals older than the last interglacial. Here we present the first robustly dated, continuous and highly resolved records of Red Sea sea level and rates of sea-level change over the last 500,000 years, based on tight synchronization to an Asian monsoon record. We observe maximum 'natural' (pre-anthropogenic forcing) sea-level rise rates below 2 m per century following periods with up to twice present-day ice volumes, and substantially higher rise rates for greater ice volumes. We also find that maximum sea-level rise rates were attained within 2 kyr of the onset of deglaciations, for 85% of such events. Finally, multivariate regressions of orbital parameters, sea-level and monsoon records suggest that major meltwater pulses account for millennial-scale variability and insolation-lagged responses in Asian monsoon records.

  16. Developing a Coastal Risk Indicator for Sea Level Rise

    NASA Astrophysics Data System (ADS)

    Masters, D. S.; Nerem, R.

    2012-12-01

    Coastal sea level rise is one the most important potential environmental risks. Multiple satellite altimeters flying on the same repeat orbit track have allowed estimation of global mean sea level for the past 20 years, and the time series has yielded information about the average rate of sea level increase over that time. Due to the duration, consistency, and inter-calibration of the altimeter measurements, the time series is now considered a climate record. The time series has also shown the strong dependence of sea level on interannual signals such as the ENSO and the NAO. But the most important sea level effects of climate change will be felt on the regional and local scales. At these smaller scales, local effects due to topography, tides, earth deformation (glacial isostatic adjustment (GIA), subsidence, etc.), and storm surges must also be considered when estimating the risks of sea level change to coastal communities. Recently, work has begun to understand the methods applicable to estimating the risks of expected sea level change to coastal communities (Strauss et al., 2012; Tebaldi et al., 2012). Tebaldi et al (2012) merged the expected global mean sea level increase from the semi-empirical model of Vermeer and Rahmstorf (2009) with historical local tide gauges to predict increases in storm surge risk posed by increasing sea level. In this work, we will further explore the currently available data and tools that can potentially be used to provide a sea level climate change indicator and local risk assessment along US coasts. These include global and regional sea level trends from the satellite altimetry climate record, in situ tide gauge measurements and the historical extremes at each location, local tide and storm surge models, topographic surveys of vulnerable coastlines, GIA models, and measurements of local subsidence and crustal deformation rates. We will also evaluate methods to estimate the increased risk to communities from sea level change

  17. Regional patterns of sea level change in the German North Sea in a worldwide context

    NASA Astrophysics Data System (ADS)

    Wahl, Thomas; Frank, Torsten; Jensen, Jürgen

    2010-05-01

    Sea Level Rise (SLR) is one of the major consequences we are facing in times of a warming climate and it is obvious that a higher sea level influences the heights of occurring storm surges and thus results in a higher risk of inundation for the affected coastal areas. Therefore, regional and global sea level rise are subjects to many recent scientific publications. In contrast, the mean sea level (MSL) and its variability over the last centuries in the German North Sea area have not been analysed in detail up to now. A methodology to analyse observed sea level rise (SLR) in the German Bight, the shallow south-eastern part of the North Sea, is presented. The contribution focuses on the description of the methods used to generate and analyse high quality mean sea level (MSL) time series. Parametric fitting approaches as well as non-parametric data adaptive filters, such as Singular System Analysis (SSA) are applied. For padding non-stationary sea level time series, an advanced approach named Monte-Carlo autoregressive padding (MCAP) is introduced. This approach allows the specification of uncertainties of the behaviour of smoothed time series near the boundaries. The results for the North Sea point to a weak negative acceleration of SLR since 1844 with a strong positive acceleration at the end of the 19th century, to a period of almost no SLR around the 1970s with subsequent positive acceleration and to high recent rates. The comparison between the German North Sea and a global sea level reconstruction clearly reveals the existence of different patterns of SLR. A stronger SLR in the German North Sea area is detected for a period covering some decades starting at the end of the 19th century and for another period covering the last ten to fifteen years. These findings and the indications for the natural variability of this complex system and further research topics will be discussed. This is a German Coastal Engineering Research Council (KFKI) project, funded by the

  18. Using Holocene relative sea-level data to inform future sea-level predictions: An example from southwest England

    NASA Astrophysics Data System (ADS)

    Gehrels, W. Roland; Dawson, David A.; Shaw, Jon; Marshall, William A.

    2011-08-01

    Holocene relative sea-level data contain information on vertical land movements along coasts and, hence, can provide vital input for predictions of future sea-level change. At Thurlestone, in southwest England, late Holocene coastal sediments were cored and sampled in coastal back-barrier marshes. The presence of a basal sedimentary unit containing salt-marsh microfossils made it possible to obtain precise estimates of late Holocene relative sea-level change from the sediments. This is important because previous studies have suggested that the southwest of England is experiencing the fastest rates of land subsidence in the British Isles. Ten new late Holocene basal sea-level index points fill an important gap in the palaeosea-level data set for southwest England. Another 15 early and middle Holocene sea-level index points are available from previous work. The data show that relative sea level rose by about 10 m between 9000 and 7000 cal. yr BP and a further 8 m in the last 7000 yr. In the last 2000 yr, relative sea level rose on average by 0.9 mm/yr. The coast is currently subsiding by 1.1 mm/yr due to ongoing glacial isostatic adjustment (GIA). The Bradley et al. (2009) GIA model, which is used in the United Kingdom to determine land-motion rates for input into future sea-level predictions, underestimates the rate of coastal subsidence by about 0.16 mm/yr, but performs better than other models. Our data validate the land-motion rates currently used in regional sea-level projections.

  19. Identifying Glacio-Eustatic Forcing of Unconformities In The Canterbury Basin (IODP Exp 317) Based on Oxygen Isotope Analysis Of The Fine Fraction

    NASA Astrophysics Data System (ADS)

    Huck, C.; John, C. M.; Shevenell, A.; Shipboard Scientific Party, E.

    2010-12-01

    /kyr) and few hiatuses provide us with the best opportunity for a high-resolution δ18OFF record (0.1-0.5 my). The δ18OFF record indicates glacial intervals that we tie to the sequence stratigraphic record of the shelf. Constraining the amplitude of sea level change requires further paired analyses of the δ18O and Mg/Ca of well-preserved benthic foraminifers. Benthic foraminifers were visually assessed and only well preserved specimens were used in our pilot study. Our more accurate geochemical record of sea level change will be coupled with backstripping studies from other workers to offer insight into how the Canterbury Basin responded to eustatic, paleoceanographic, and tectonic change during the Plio-Pleistocene.

  20. Continental Shelf Morphology and Stratigraphy Offshore San Onofre, CA: The Interplay Between Rates of Eustatic Change and Sediment Supply

    USGS Publications Warehouse

    Klotsko, Shannon; Driscoll, Neal W.; Kent, Graham; Brothers, Daniel

    2016-01-01

    New high-resolution CHIRP seismic data acquired offshore San Onofre, southern California reveal that shelf sediment distribution and thickness are primarily controlled by eustatic sea level rise and sediment supply. Throughout the majority of the study region, a prominent abrasion platform and associated shoreline cutoff are observed in the subsurface from ~ 72 to 53 m below present sea level. These erosional features appear to have formed between Melt Water Pulse 1A and Melt Water Pulse 1B, when the rate of sea-level rise was lower. There are three distinct sedimentary units mapped above a regional angular unconformity interpreted to be the Holocene transgressive surface in the seismic data. Unit I, the deepest unit, is interpreted as a lag deposit that infills a topographic low associated with an abrasion platform. Unit I thins seaward by downlap and pinches out landward against the shoreline cutoff. Unit II is a mid-shelf lag deposit formed from shallower eroded material and thins seaward by downlap and landward by onlap. The youngest, Unit III, is interpreted to represent modern sediment deposition. Faults in the study area do not appear to offset the transgressive surface. The Newport Inglewood/Rose Canyon fault system is active in other regions to the south (e.g., La Jolla) where it offsets the transgressive surface and creates seafloor relief. Several shoals observed along the transgressive surface could record minor deformation due to fault activity in the study area. Nevertheless, our preferred interpretation is that the shoals are regions more resistant to erosion during marine transgression. The Cristianitos fault zone also causes a shoaling of the transgressive surface. This may be from resistant antecedent topography due to an early phase of compression on the fault. The Cristianitos fault zone was previously defined as a down-to-the-north normal fault, but the folding and faulting architecture imaged in the CHIRP data are more consistent with a

  1. Lowstand versus highstand eustatic models for peat preservation: The coal-bearing rocks of the Breathitt Group, Eastern Kentucky

    SciTech Connect

    Chesnut, D.R. Jr.; Greb, S.F. . Kentucky Geological Survey)

    1992-01-01

    Stratigraphic and chronologic studies suggest that the alternation between major coal beds and clastic rocks of the Lower and Middle Pennsylvanian Breathitt Group (Central Appalachian Basin) resulted from glacial eustacy. The typical Coal-Clastic cycle starts at the top of a major coal bed and consists of a coarsening-upward sequence of marine or brackish-water strata which is commonly truncated and overlain by a fining-upward sequence. The fining-upward sequence is overlain by a rooted paleosol which is overlain by a coal bed. In one scenario, the peat is deposited during the stable highstand period. Because of subsidence, the highstand peat deposit is drowned and covered by marine sediments. During the subsequent lowstand the marine strata are eroded to varying degrees and bare channels are developed, causing an erosional unconformity surface on the marine strata. During transgression, the rise in base-level causes sediments to aggrade within the channels, creating fining-upward sequences above the marine strata. Paleosol development and peat deposition begin again at the next highstand. In another scenario peats are deposited in a coastal setting during lowstand. As transgression proceeds from lowstand, channels backfill and all low-lying areas including peat are covered by coarsening-upward sequences. Peats are then deposited on exposed platforms during highstand. During the subsequent drop in sea level, channels are incised and highstand peats and part of the coarsening-upward sediment package is eroded. The second scenario implies a preservation bias to cyclothems caused by eustatic rates being greater than subsidence rates. Peats are probably deposited during both lowstand and highstand, but lowstand peats are more likely to be preserved.

  2. The multimillennial sea-level commitment of global warming.

    PubMed

    Levermann, Anders; Clark, Peter U; Marzeion, Ben; Milne, Glenn A; Pollard, David; Radic, Valentina; Robinson, Alexander

    2013-08-20

    Global mean sea level has been steadily rising over the last century, is projected to increase by the end of this century, and will continue to rise beyond the year 2100 unless the current global mean temperature trend is reversed. Inertia in the climate and global carbon system, however, causes the global mean temperature to decline slowly even after greenhouse gas emissions have ceased, raising the question of how much sea-level commitment is expected for different levels of global mean temperature increase above preindustrial levels. Although sea-level rise over the last century has been dominated by ocean warming and loss of glaciers, the sensitivity suggested from records of past sea levels indicates important contributions should also be expected from the Greenland and Antarctic Ice Sheets. Uncertainties in the paleo-reconstructions, however, necessitate additional strategies to better constrain the sea-level commitment. Here we combine paleo-evidence with simulations from physical models to estimate the future sea-level commitment on a multimillennial time scale and compute associated regional sea-level patterns. Oceanic thermal expansion and the Antarctic Ice Sheet contribute quasi-linearly, with 0.4 m °C(-1) and 1.2 m °C(-1) of warming, respectively. The saturation of the contribution from glaciers is overcompensated by the nonlinear response of the Greenland Ice Sheet. As a consequence we are committed to a sea-level rise of approximately 2.3 m °C(-1) within the next 2,000 y. Considering the lifetime of anthropogenic greenhouse gases, this imposes the need for fundamental adaptation strategies on multicentennial time scales.

  3. The multimillennial sea-level commitment of global warming

    PubMed Central

    Levermann, Anders; Clark, Peter U.; Marzeion, Ben; Milne, Glenn A.; Pollard, David; Radic, Valentina; Robinson, Alexander

    2013-01-01

    Global mean sea level has been steadily rising over the last century, is projected to increase by the end of this century, and will continue to rise beyond the year 2100 unless the current global mean temperature trend is reversed. Inertia in the climate and global carbon system, however, causes the global mean temperature to decline slowly even after greenhouse gas emissions have ceased, raising the question of how much sea-level commitment is expected for different levels of global mean temperature increase above preindustrial levels. Although sea-level rise over the last century has been dominated by ocean warming and loss of glaciers, the sensitivity suggested from records of past sea levels indicates important contributions should also be expected from the Greenland and Antarctic Ice Sheets. Uncertainties in the paleo-reconstructions, however, necessitate additional strategies to better constrain the sea-level commitment. Here we combine paleo-evidence with simulations from physical models to estimate the future sea-level commitment on a multimillennial time scale and compute associated regional sea-level patterns. Oceanic thermal expansion and the Antarctic Ice Sheet contribute quasi-linearly, with 0.4 m °C−1 and 1.2 m °C−1 of warming, respectively. The saturation of the contribution from glaciers is overcompensated by the nonlinear response of the Greenland Ice Sheet. As a consequence we are committed to a sea-level rise of approximately 2.3 m °C−1 within the next 2,000 y. Considering the lifetime of anthropogenic greenhouse gases, this imposes the need for fundamental adaptation strategies on multicentennial time scales. PMID:23858443

  4. The anatomy of recent large sea level fluctuations in the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Landerer, Felix W.; Volkov, Denis L.

    2013-02-01

    Abstract During the boreal winter months of 2009/2010 and 2010/2011, Mediterranean mean <span class="hlt">sea</span> <span class="hlt">level</span> rose 10 cm above the average monthly climatological values. The non-seasonal anomalies were observed in <span class="hlt">sea</span> surface height (from altimetry), as well as ocean mass (from gravimetry), indicating they were mostly of barotropic nature. These relatively rapid basin-wide fluctuations occurred over time scales of 1-5 months. Here we use observations and re-analysis data to attribute the non-seasonal <span class="hlt">sea</span> <span class="hlt">level</span> and ocean mass fluctuations in the Mediterranean <span class="hlt">Sea</span> to concurrent wind stress anomalies over the adjacent subtropical Northeast Atlantic Ocean, just west of the Strait of Gibraltar, and extending into the strait itself. The observed Mediterranean <span class="hlt">sea</span> <span class="hlt">level</span> fluctuations are strongly anti-correlated with the monthly North-Atlantic-Oscillation (NAO) index.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMED13C3467T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMED13C3467T"><span>Climate And <span class="hlt">Sea</span> <span class="hlt">Level</span>: It's In Our Hands Now</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Turrin, M.; Bell, R. E.; Ryan, W. B. F.</p> <p>2014-12-01</p> <p>Changes in <span class="hlt">sea</span> <span class="hlt">level</span> are measurable on both a local and a global scale providing an accessible way to connect climate to education, yet engaging teachers and students with the complex science that is behind the change in <span class="hlt">sea</span> <span class="hlt">level</span> can be a challenge. Deciding how much should be included and just how it should be introduced in any single classroom subject area can be an obstacle for a teacher. The <span class="hlt">Sea</span> <span class="hlt">Level</span> Rise Polar Explorer App developed through the PoLAR CCEP grant offers a guided tour through the many layers of science that impact <span class="hlt">sea</span> <span class="hlt">level</span> rise. This map-based data-rich app is framed around a series of questions that move the user through map layers with just the <span class="hlt">level</span> of complexity they chose to explore. For a quick look teachers and students can review a 3 or 4 sentence introduction on how the given map links to <span class="hlt">sea</span> <span class="hlt">level</span> and then launch straight into the interactive touchable map. For a little more in depth look they can listen to (or read) a one-minute recorded background on the data displayed in the map prior to launching in. For those who want more in depth understanding they can click to a one page background piece on the topic with links to further visualizations, videos and data. Regardless of the <span class="hlt">level</span> of complexity selected each map is composed of clickable data allowing the user to fully explore the science. The different options for diving in allow teachers to differentiate the learning for either the subject being taught or the user <span class="hlt">level</span> of the student group. The map layers also include a range of complexities. Basic questions like "What is <span class="hlt">sea</span> <span class="hlt">level</span>?" talk about shorelines, past <span class="hlt">sea</span> <span class="hlt">levels</span> and elevations beneath the <span class="hlt">sea</span>. Questions like "Why does <span class="hlt">sea</span> <span class="hlt">level</span> change?" includes slightly more complex issues like the role of ocean temperature, and how that differs from ocean heat content. And what is the role of the warming atmosphere in <span class="hlt">sea</span> <span class="hlt">level</span> change? Questions about "What about <span class="hlt">sea</span> <span class="hlt">level</span> in the past?" can bring challenges for students who have</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.5762L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.5762L"><span>Two Decades of Global and Regional <span class="hlt">Sea</span> <span class="hlt">Level</span> Observations from the ESA Climate Change Initiative <span class="hlt">Sea</span> <span class="hlt">Level</span> Project</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Legeais, JeanFrancois; Larnicol, Gilles; Cazenave, Anny; Ablain, Michael; Benveniste, Jérôme; Lucas, BrunoManuel; Timms, Gary; Johannessen, Johnny; Knudsen, Per; Cipollini, Paolo; Roca, Monica; Rudenko, Sergei; Fernandes, Joana; Balmaseda, Magdalena; Quartly, Graham; Fenoglio-Marc, Luciana; Scharfennberg, Martin; Meyssignac, Benoit; Guinle, Thierry; Andersen, Ole</p> <p>2015-04-01</p> <p><span class="hlt">Sea</span> <span class="hlt">level</span> is a very sensitive index of climate change and variability. <span class="hlt">Sea</span> <span class="hlt">level</span> integrates the ocean warming, mountain glaciers and ice sheet melting. Understanding the <span class="hlt">sea</span> <span class="hlt">level</span> variability and changes implies an accurate monitoring of the <span class="hlt">sea</span> <span class="hlt">level</span> variable at climate scales, in addition to understanding the ocean variability and the exchanges between ocean, land, cryosphere, and atmosphere. That is why <span class="hlt">Sea</span> <span class="hlt">Level</span> is one of the Essential Climate Variables (ECV) selected in the frame of the ESA Climate Change Initiative (CCI) program. It aims at providing long-term monitoring of the <span class="hlt">sea</span> <span class="hlt">level</span> ECV with regular updates, as required for climate studies. After a first phase (2011-2013), the program has started in 2014 a second phase of 3 years. The objectives of this second phase are to involve the climate research community, to refine their needs and collect their feedbacks on product quality, to develop, test and select the best algorithms and standards to generate an updated climate time series and to produce and validate the <span class="hlt">Sea</span> <span class="hlt">Level</span> ECV product. This will better answer the climate user needs by improving the quality of the <span class="hlt">Sea</span> <span class="hlt">Level</span> products and maintain a sustain service for an up-to-date production. To this extent, the ECV time series has been extended and it now covers the period 1993-2013. We will firstly present the main achievements of the ESA CCI <span class="hlt">Sea</span> <span class="hlt">Level</span> Project. On the one hand, the major steps required to produce the 21 years climate time series are briefly described: collect and refine the user requirements, development of adapted algorithms for climate applications and specification of the production system. On the other hand, the product characteristics are described as well as the results from product validation, performed by several groups of the ocean and climate modeling community. At last, the work plan and key challenges of the second phase of the project are described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70020486','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70020486"><span>Cenozoic global <span class="hlt">sea</span> <span class="hlt">level</span>, sequences, and the New Jersey transect: Results from coastal plain and continental slope drilling</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Miller, K.G.; Mountain, Gregory S.; Browning, J.V.; Kominz, M.; Sugarman, P.J.; Christie-Blick, N.; Katz, M.E.; Wright, J.D.</p> <p>1998-01-01</p> <p>The New Jersey <span class="hlt">Sea</span> <span class="hlt">Level</span> Transect was designed to evaluate the relationships among global <span class="hlt">sea</span> <span class="hlt">level</span> (<span class="hlt">eustatic</span>) change, unconformity-bounded sequences, and variations in subsidence, sediment supply, and climate on a passive continental margin. By sampling and dating Cenozoic strata from coastal plain and continental slope locations, we show that sequence boundaries correlate (within ??0.5 myr) regionally (onshore-offshore) and interregionally (New Jersey-Alabama-Bahamas), implicating a global cause. Sequence boundaries correlate with ??18O increases for at least the past 42 myr, consistent with an ice volume (glacioeustatic) control, although a causal relationship is not required because of uncertainties in ages and correlations. Evidence for a causal connection is provided by preliminary Miocene data from slope Site 904 that directly link ??18O increases with sequence boundaries. We conclude that variation in the size of ice sheets has been a primary control on the formation of sequence boundaries since ~42 Ma. We speculate that prior to this, the growth and decay of small ice sheets caused small-amplitude <span class="hlt">sea</span> <span class="hlt">level</span> changes (<20 m) in this supposedly ice-free world because Eocene sequence boundaries also appear to correlate with minor ??18O increases. Subsidence estimates (backstripping) indicate amplitudes of short-term (million-year scale) lowerings that are consistent with estimates derived from ??18O studies (25-50 m in the Oligocene-middle Miocene and 10-20 m in the Eocene) and a long-term lowering of 150-200 m over the past 65 myr, consistent with estimates derived from volume changes on mid-ocean ridges. Although our results are consistent with the general number and timing of Paleocene to middle Miocene sequences published by workers at Exxon Production Research Company, our estimates of <span class="hlt">sea</span> <span class="hlt">level</span> amplitudes are substantially lower than theirs. Lithofacies patterns within sequences follow repetitive, predictable patterns: (1) coastal plain sequences consist</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.4218K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.4218K"><span><span class="hlt">Sea-level</span> variability over the Common Era</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kopp, Robert; Horton, Benjamin; Kemp, Andrew; Engelhart, Simon; Little, Chris</p> <p>2017-04-01</p> <p>The Common Era (CE) <span class="hlt">sea-level</span> 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 <span class="hlt">sea</span> <span class="hlt">level</span> with sufficient spatial and temporal resolution to inform mechanisms underlying regional and global <span class="hlt">sea</span> <span class="hlt">level</span> variability and their relationship to other climate proxies. This coast has a small tidal range, improving the precision of <span class="hlt">sea-level</span> reconstructions. Coastal subsidence (from glacial isostatic adjustment, GIA) creates accommodation space that is filled by salt-marsh peat and preserves accurate and precise <span class="hlt">sea-level</span> indicators and abundant material for radiocarbon dating. In addition to longer term GIA induced land-<span class="hlt">level</span> change from ongoing collapse of the Laurentide forebulge, these records are ideally situated to capture climate-driven <span class="hlt">sea</span> <span class="hlt">level</span> changes. The western North Atlantic Ocean <span class="hlt">sea</span> <span class="hlt">level</span> 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 <span class="hlt">sea-level</span> during the CE along the United States Atlantic coast: (1) South of Cape Hatteras, North Carolina, to Florida <span class="hlt">sea-level</span> 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, <span class="hlt">sea</span> <span class="hlt">level</span> rise to maximum around 1000CE, a <span class="hlt">sea-level</span> minimum around 1500 CE, and a long-term <span class="hlt">sea-level</span> rise through the second half of the second millennium. The northern-intensified <span class="hlt">sea-level</span> fall beginning 1000 is coincident with shifts toward persistent positive NAO-like atmospheric states inferred from other proxy records and is consistent with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMED43A0678M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMED43A0678M"><span>Hazard Risk to Near <span class="hlt">Sea-Level</span> Populations due to Tropical Cyclone Intensification and <span class="hlt">Sea-Level</span> Rise</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Montain, J.; Byrne, J. M.; Elsner, J.</p> <p>2010-12-01</p> <p>Tropical cyclone (TC) intensification has been well documented in the science literature. TC intensification combined with <span class="hlt">sea-level</span> rise contributes to an enhanced risk to huge populations living near <span class="hlt">sea</span> <span class="hlt">level</span> around the world. This study will apply spatial analysis techniques to combine the best available TC intensification data on storm surge, wave height and wind speeds; with digital elevation models and global population density estimates, to provide a first <span class="hlt">level</span> evaluation of the increasing risk to human life and health.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1710077E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1710077E"><span>Characterization of extreme <span class="hlt">sea</span> <span class="hlt">level</span> at the European coast</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Elizalde, Alberto; Jorda, Gabriel; Mathis, Moritz; Mikolajewicz, Uwe</p> <p>2015-04-01</p> <p>Extreme high <span class="hlt">sea</span> <span class="hlt">levels</span> arise as a combination of storm surges and particular high tides events. Future climate simulations not only project changes in the atmospheric circulation, which induces changes in the wind conditions, but also an increase in the global mean <span class="hlt">sea</span> <span class="hlt">level</span> by thermal expansion and ice melting. Such changes increase the risk of coastal flooding, which represents a possible hazard for human activities. Therefore, it is important to investigate the pattern of <span class="hlt">sea</span> <span class="hlt">level</span> variability and long-term trends at coastal areas. In order to analyze further extreme <span class="hlt">sea</span> <span class="hlt">level</span> events at the European coast in the future climate projections, a new setup for the global ocean model MPIOM coupled with the regional atmosphere model REMO is prepared. The MPIOM irregular grid has enhanced resolution in the European region to resolve the North and the Mediterranean <span class="hlt">Seas</span> (up to 11 x 11 km at the North <span class="hlt">Sea</span>). The ocean model includes as well the full luni-solar ephemeridic tidal potential for tides simulation. To simulate the air-<span class="hlt">sea</span> interaction, the regional atmospheric model REMO is interactively coupled to the ocean model over Europe. Such region corresponds to the EuroCORDEX domain with a 50 x 50 km resolution. Besides the standard fluxes of heat, mass (freshwater), momentum and turbulent energy input, the ocean model is also forced with <span class="hlt">sea</span> <span class="hlt">level</span> pressure, in order to be able to capture the full variation of <span class="hlt">sea</span> <span class="hlt">level</span>. The hydrological budget within the study domain is closed using a hydrological discharge model. With this model, simulations for present climate and future climate scenarios are carried out to study transient changes on the <span class="hlt">sea</span> <span class="hlt">level</span> and extreme events. As a first step, two simulations (coupled and uncoupled ocean) driven by reanalysis data (ERA40) have been conducted. They are used as reference runs to evaluate the climate projection simulations. For selected locations at the coast side, time series of <span class="hlt">sea</span> <span class="hlt">level</span> are separated on its different</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.1563H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.1563H"><span>The importance of <span class="hlt">sea-level</span> research (Plinius Medal Lecture)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Horton, Benjamin</p> <p>2016-04-01</p> <p>200 million people worldwide live in coastal regions less than 5 meters above <span class="hlt">sea</span> <span class="hlt">level</span>. By the end of the 21st century, this figure is estimated to increase to 500 million. These low-lying coastal regions are vulnerable to changes in <span class="hlt">sea</span> <span class="hlt">level</span> brought about by climate change, storms or earthquakes. But the historic and instrumental record is too short to fully understand the climate relationships and capture the occurrence of the rare, but most destructive events. The coastal sedimentary record provides a long-term and robust paleo perspective on the rates, magnitudes and spatial variability of <span class="hlt">sea-level</span> rise and the frequency (recurrence interval) and magnitude of destructive events. Reconstructions of paleo <span class="hlt">sea</span> <span class="hlt">level</span> are important for identifying the meltwater contributions, constraining parameters in Earth-Ice models, and estimating past and present rates of spatially variable <span class="hlt">sea-level</span> change associated glacial isostatic adjustment, sediment compaction and tidal range variability. <span class="hlt">Sea-level</span> reconstructions capture multiple phases of climate and <span class="hlt">sea-level</span> behavior for model calibration and provide a pre-anthropogenic background against which to compare recent trends. Pre-historic earthquakes (Mw>8.0) are often associated with abrupt and cyclical patterns of vertical land-motion that are manifest in coastal sedimentary archives as abrupt changes in relative <span class="hlt">sea</span> <span class="hlt">level</span>. Geologic evidence of paleoearthquakes elucidates characteristic and repeated pattern of land-<span class="hlt">level</span> movements associated with the earthquake-deformation cycle. Tsunamis and storms leave behind anomalous and characteristic sediment that is incorporated into the coastal sedimentary record often as evidence of a high-energy event affecting a low-energy, depositional environment. Records of tsunamis developed from the sedimentary deposits they leave behind improve understanding of tsunami processes and frequency by expanding the age range of events available for study. Reconstructions of paleo storms</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6830903','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6830903"><span>Greenhouse effect, <span class="hlt">sea</span> <span class="hlt">level</span> rise, and coastal wetlands</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Titus, J.G.</p> <p>1988-07-01</p> <p>To further society's understanding of how to rationally respond to the possibility of a substantial rise in <span class="hlt">level</span>, EPA has undertaken assessments of the impacts of <span class="hlt">sea</span> <span class="hlt">level</span> rise on economic development, beach erosion control strategies, salinity of estuaries and aquifers, and coastal drainage and sewage systems. Those studies have generally found that even a one-foot rise in a <span class="hlt">sea</span> <span class="hlt">level</span> has important implications for the planning and design of coastal facilities. This report examines the potential impacts of <span class="hlt">sea</span> <span class="hlt">level</span> on coastal wetlands in the United States. Coastal marshes and swamps are generally within a few feet of <span class="hlt">sea</span> <span class="hlt">level</span>, and hence could be lost if seal <span class="hlt">level</span> rises significantly. Although new wetlands could form where new areas are flooded, this cannot happen where the land adjacent to today's wetlands is developed and protected from the rising <span class="hlt">sea</span>. Once built, neighborhoods can be expected to last a century or longer. Therefore, todays coastal development could limit the ability of coastal wetlands to survive <span class="hlt">sea</span> <span class="hlt">level</span> in the next century. Chapter 1 provides an overview of the greenhouse effect, projections of future <span class="hlt">sea</span> <span class="hlt">level</span> rise, the basis for expecting significant impacts on coastal wetlands, and possible responses. Chapters 2 and 3 present case studies of the potential impacts on wetlands around Charleston, South Carolina, and Long Beach Island, New Jersey, based on field surveys. Chapter 4 presents a first attempt to estimate the nationwide impact, based on topographic maps. Finally, Chapter 5 describes measures that wetland protection officials can take today. This report neither examines the impact of <span class="hlt">sea</span> <span class="hlt">level</span> rise on specific federal programs nor recommends specific policy changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010OcSci...6..311I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010OcSci...6..311I"><span>Seasonal variability of the Caspian <span class="hlt">Sea</span> three-dimensional circulation, <span class="hlt">sea</span> <span class="hlt">level</span> and air-<span class="hlt">sea</span> interaction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ibrayev, R. A.; Özsoy, E.; Schrum, C.; Sur, H. I.</p> <p>2010-03-01</p> <p>A three-dimensional primitive equation model including <span class="hlt">sea</span> ice thermodynamics and air-<span class="hlt">sea</span> interaction is used to study seasonal circulation and water mass variability in the Caspian <span class="hlt">Sea</span> under the influence of realistic mass, momentum and heat fluxes. River discharges, precipitation, radiation and wind stress are seasonally specified in the model, based on available data sets. The evaporation rate, sensible and latent heat fluxes at the <span class="hlt">sea</span> surface are computed interactively through an atmospheric boundary layer sub-model, using the ECMWF-ERA15 re-analysis atmospheric data and model generated <span class="hlt">sea</span> surface temperature. The model successfully simulates <span class="hlt">sea-level</span> changes and baroclinic circulation/mixing features with forcing specified for a selected year. The results suggest that the seasonal cycle of wind stress is crucial in producing basin circulation. Seasonal cycle of <span class="hlt">sea</span> surface currents presents three types: cyclonic gyres in December-January; Eckman south-, south-westward drift in February-July embedded by western and eastern southward coastal currents and transition type in August-November. Western and eastern northward sub-surface coastal currents being a result of coastal local dynamics at the same time play an important role in meridional redistribution of water masses. An important part of the work is the simulation of <span class="hlt">sea</span> surface topography, yielding verifiable results in terms of <span class="hlt">sea</span> <span class="hlt">level</span>. The model successfully reproduces <span class="hlt">sea</span> <span class="hlt">level</span> variability for four coastal points, where the observed data are available. Analyses of heat and water budgets confirm climatologic estimates of heat and moisture fluxes at the <span class="hlt">sea</span> surface. Experiments performed with variations in external forcing suggest a sensitive response of the circulation and the water budget to atmospheric and river forcing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009OcScD...6.1913I',