scholarly journals Migration of Barchan Dunes in Qatar—Controls of the Shamal, Teleconnections, Sea-Level Changes and Human Impact

2018 ◽  
Author(s):  
Max Engel ◽  
Fabian Boesl ◽  
Helmut Brückner
Keyword(s):  
Sea Level ◽  
Human Impact ◽  
Decadal Variability ◽  
Arabian Gulf ◽  
Sea Level Changes ◽  
Migration Rates ◽  
The North ◽  
Sand Supply ◽  
Barchan Dunes ◽  
Dune Migration

Barchan dune fields are a dominant landscape feature in SE Qatar and a key element of the peninsula’s geodiversity. The migration of barchan dunes is mainly controlled by dune size, wind pattern, vegetation cover and human impact. We investigate the variability of dune migration in Qatar over a time period of 50 years using high-resolution satellite and aerial imagery and explore its relation to the regional Shamal wind system, teleconnection patterns, and limitations in sand supply associated with the transgression of the Arabian Gulf. We detect strong size-dependent differences in migration rates of individual dunes as well as significant decadal variability on a dune-field scale, which was found to be correlating with the intensity of the North Atlantic Oscillation (NAO) and the Indian Summer Monsoon (ISM). High uncertainties associated with the extrapolation of migration rates back into the Holocene, however, do not permit to further specify the timing of the loss of sand supply and the onset of the mid-Holocene relative sea-level (RSL) highstand. For the youngest phase considered in this study (2006–2015), human impact is anticipated to have accelerated dune migration under a weakening Shamal regime through sand mining and excessive vehicle frequentation upwind of the core study area.

scholarly journals Interdecadal Baroclinic Sea Level Changes in the North Pacific Based on Historical Ocean Hydrographic Observations

2015 ◽  
Vol 28 (11) ◽  
pp. 4585-4594 ◽  
Author(s):  
Tatsuo Suzuki ◽  
Masayoshi Ishii
Keyword(s):  
Sea Level ◽  
Wind Stress ◽  
North Pacific ◽  
Water Mass ◽  
Mass Density ◽  
Baroclinic Mode ◽  
Sea Level Changes ◽  
The North ◽  
Basin Scale ◽  
The North Pacific

Abstract Using historical ocean hydrographic observations, decadal to multidecadal sea level changes from 1951 to 2007 in the North Pacific were investigated focusing on vertical density structures. Hydrographically, the sea level changes could reflect the following: changes in the depth of the main pycnocline, density gradient changes across the pycnocline, and modification of the water mass density structure within the pycnocline. The first two processes are characterized as the first baroclinic mode. The changes in density stratification across the pycnocline are sufficiently small to maintain the vertical profile of the first baroclinic mode in this analysis period. Therefore, the first mode should represent mainly the dynamical response to the wind stress forcing. Meanwhile, changes in the composite of all modes of order greater than 1 (remaining baroclinic mode) can be attributed to water mass modifications above the pycnocline. The first baroclinic mode is associated with 40–60-yr fluctuations in the subtropical gyre and bidecadal fluctuations of the Kuroshio Extension (KE) in response to basin-scale wind stress changes. In addition to this, the remaining baroclinic mode exhibits strong variability around the recirculation region south of the KE and regions downstream of the KE, accompanied by 40–60-yr and bidecadal fluctuations, respectively. These fluctuations follow spinup/spindown of the subtropical gyre and meridional shifts of the KE shown in the first mode, respectively. A lag correlation analysis suggests that interdecadal sea level changes due to water mass density changes are a secondary consequence of changes in basin-scale wind stress forcing related to the ocean circulation changes associated with the first mode.

A global decadal mode in a high-end climate model and in observations: Any connection to the solar cycle?

2021 ◽  
Author(s):  
Michael Ghil ◽  
Yizhak Feliks ◽  
Justin Small
Keyword(s):  
Solar Cycle ◽  
Sea Level ◽  
North Atlantic ◽  
Climate Model ◽  
Decadal Variability ◽  
Singular Spectrum Analysis ◽  
Coupled System ◽  
The North ◽  
Spatio Temporal ◽  
Decadal Mode

<p>The present work addresses two persistent quandaries of the climate sciences: (i) the existence of global oscillatory modes in the coupled ocean–atmosphere system; and (ii) solar effects on this coupled system. Interannual oscillatory modes, atmospheric and oceanic, are present in several large regions of the globe. We examine here interannual-to-decadal variability over the entire globe in the Community Earth System Model (CESM) and in the NCEP-NCAR reanalysis, and apply multichannel singular spectrum analysis (MSSA) to these two datasets.</p><p>In the fully coupled CESM1.1 model, with its resolution of 0.1 × 0.1 degrees in the ocean and 0.25 × 0.25 degrees in the atmosphere, the fields analyzed are surface temperatures, sea level pressures and  the 200-hPa geopotential. The simulation is 100-yr long and the last 66 yr are used in the analysis. The two statistically significant periodicities in this IPCC-class model are 11 and 3.4 yr.</p><p>In the reanalysis, the fields of sea level pressure and of 200-hPa geopotential are analyzed at its resolution of 2.5 × 2.5 degrees over the 68-yr interval 1949–2016. Oscillations with periods of 12 and 3.6 yr are found to be statistically significant in this dataset. The spatio-temporal patterns  of the oscillations in the two datasets are quite similar. The spatial pattern of these  global oscillations over the North Pacific and North Atlantic resemble the Pacific Decadal Oscillation and the interannual variability found in the western North Atlantic, respectively.</p><p>The two global modes, with their 11–12-yr and 3.4–3.6-yr periodicities, are quite robust, suggesting potential contributions of both to predictability at 1–3-yr horizons. On the other hand, the CESM run has no year-to-year changes in the prescribed insolation, excluding any role of the solar cycle in the model’s 11-yr mode. The solar cycle is present, however, in the reanalysis, since it is present in nature and hence it does affect the observations. We speculate, therefore, that regional oscillations — with their distinct near-periodicities and spatial patterns — are synchronized  over the globe, thus yielding both the global oscillatory modes found in CESM. In nature, the decadal mode could be further synchronized with the solar cycle, but that does not seem to be the case, given the slight difference in period — 12 yr for the reanalysis and 11 yr for the solar cycle, which makes them drift in and out of phase.</p><p>The work’s tentative conclusion is, therefore: (i) yes, there are global oscillatory modes in the climate system, especially a decadal mode; but (ii) no, this mode has little or nothing to do with the solar cycle.</p>

scholarly journals Origin of the Late Ordovician Lepidocyclus brachiopod fauna in North America and its biogeographic significance

1992 ◽  
Vol 6 ◽  
pp. 149-149
Author(s):  
Jisuo Jin
Keyword(s):  
North America ◽  
Sea Level ◽  
North American ◽  
Plate Tectonics ◽  
Late Ordovician ◽  
Sea Level Changes ◽  
Stepping Stones ◽  
Shell Size ◽  
Larval Stages ◽  
The North

Three rhynchonellid brachiopod genera, Hiscobeccus, Lepidocyclus, and Hypsiptycha, are the most diagnostic elements of the Lepidocyclus fauna of North America in Late Ordovician time. These are characterized by relatively large, strongly biconvex to globular shells with coarse imbricating growth lamellae and, internally, with septiform cardinal processes in brachial valves. Among the three genera, Hiscobeccus appears the earliest, now known from rocks of late Trentonian-Edenian age in the Canadian Rocky Mountains and Mackenzie Mountains. Morphologically, Hiscobeccus is distinguished from the other two genera by its open delthyrium in the pedicle valve. Early forms of Hiscobeccus show close morphological similarity to Rhynchotrema in their non-globular biconvex shells covered by strong growth lamellae only in the anterior portions. It has been suggested that Hiscobeccus evolved from the Rhynchotrema wisconsinense stock through increase in shell size, globosity, and strength of growth lamellae. Earliest species of Rhynchotrema has been documented convincingly from rocks of early Trentonian age, and the derivation of Hiscobeccus most likely took place during the mid-Trentonian. Lepidocyclus and Hypsiptycha evolved from either Rhynchotrema or Hiscobeccus by developing a pair of deltidial plates covering the delthyrium.Rhynchotrema and other rhynchonellids that evolved before mid-Trentonian time are common to the North American (Laurentian) and the Siberia-Kazakhstan paleocontinents. In contrast, Hiscobeccus, Lepidocyclus, and Hypsiptycha that evolved after the mid-Trentonian are virtually restricted to Laurentia. Therefore, Rhynchotrema marked the last successful intercontinental migration of rhynchonellids during their Llandeilian-Caradocian cosmopolitanism. The pronounced provincialism of the North American Lepidocyclus fauna may have been caused by a number of factors. Facies control is not likely the explanation because these rhynchonellids occur in nearly all the inland and marginal platform seas of Laurentia and commonly are found together in the same types of rocks. Plate tectonics and sea-level changes are considered major causes. The Ordovician rhynchonellids lived in shallow marine (intertidal-subtidal) environments and were incapable of crossing vast, deep oceanic barriers because of their sedentary mode of life and short-lived motile larval stages. The widening of the ocean between North America and Siberia, coupled with high sea-level stand, may have created a sufficiently wide oceanic barrier to interrupt faunal mixing between the two paleocontinents by late Trentonian time. Moreover, the rise in sea level would have resulted in the disappearance of island faunas, which could have served as stepping stones for intercontinental migration of shallow-water benthic faunas during low sea-level stand.

scholarly journals Annual Sea Level Changes on the North American Northeast Coast: Influence of Local Winds and Barotropic Motions

2016 ◽  
Vol 29 (13) ◽  
pp. 4801-4816 ◽  
Author(s):  
Christopher G. Piecuch ◽  
Sönke Dangendorf ◽  
Rui M. Ponte ◽  
Marta Marcos
Keyword(s):  
Sea Level ◽  
Wind Stress ◽  
Ocean Circulation ◽  
Tide Gauge ◽  
Sea Level Changes ◽  
Tide Gauge Records ◽  
Barotropic Model ◽  
The North ◽  
Ocean Reanalyses ◽  
Coastal Sea

Abstract Understanding the relationship between coastal sea level and the variable ocean circulation is crucial for interpreting tide gauge records and projecting sea level rise. In this study, annual sea level records (adjusted for the inverted barometer effect) from tide gauges along the North American northeast coast over 1980–2010 are compared to a set of data-assimilating ocean reanalysis products as well as a global barotropic model solution forced with wind stress and barometric pressure. Correspondence between models and data depends strongly on model and location. At sites north of Cape Hatteras, the barotropic model shows as much (if not more) skill than ocean reanalyses, explaining about 50% of the variance in the adjusted annual tide gauge sea level records. Additional numerical experiments show that annual sea level changes along this coast from the barotropic model are driven by local wind stress over the continental shelf and slope. This result is interpreted in the light of a simple dynamic framework, wherein bottom friction balances surface wind stress in the alongshore direction and geostrophy holds in the across-shore direction. Results highlight the importance of barotropic dynamics on coastal sea level changes on interannual and decadal time scales; they also have implications for diagnosing the uncertainties in current ocean reanalyses, using tide gauge records to infer past changes in ocean circulation, and identifying the physical mechanisms responsible for projected future regional sea level rise.

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

2009 ◽  
Vol 28 (17-18) ◽  
pp. 1725-1736 ◽  
Author(s):  
B.P. Horton ◽  
W.R. Peltier ◽  
S.J. Culver ◽  
R. Drummond ◽  
S.E. Engelhart ◽  
...  
Keyword(s):  
North Carolina ◽  
Sea Level ◽  
Glacial Isostatic Adjustment ◽  
Sea Level Changes ◽  
Isostatic Adjustment ◽  
The North ◽  
Holocene Sea Level

Tremadocian (Lower Ordovician) sea-level changes and biotas on the Avalon microcontinent

2011 ◽  
Vol 85 (4) ◽  
pp. 678-694 ◽  
Author(s):  
ED Landing ◽  
Richard A. Fortey
Keyword(s):  
Sea Level ◽  
Sea Level Changes ◽  
Low Oxygen ◽  
Cape Breton Island ◽  
Lower Upper ◽  
The North ◽  
Cape Breton ◽  
Lower Ordovician ◽  
Bottom Waters ◽  
History Of

The Chesley Drive Group, an Upper Cambrian-Lower Ordovician mudstone-dominated unit, is part of the Ediacaran–Ordovician cover sequence on the North American part of the Avalon microcontinent. The upper Chesley Drive Group on McLeod Brook, Cape Breton Island (previously “McLeod Brook Formation”), has two lithofacies-specific Tremadocian biotas. An older low-diversity benthic assemblage (shallow burrowers, Bathysiphon, phosphatic brachiopods, asaphid trilobites) is in lower upper Tremadocian green-gray mudstone. This wave-influenced, slightly dysoxic facies has Bathysiphon–brachiopod shell lags in ripple troughs. The upper fauna (ca. 483 +/- 1 Ma) is in dysoxic-anoxic (d-a), unburrowed, dark gray-black, upper upper (but not uppermost) Tremadocian mudstone with a “mass kill” of the olenid Peltocare rotundifrons (Matthew)—a provincial trilobite in Avalonian North America that likely tolerated low oxygen bottom waters. Scandodus avalonensis Landing n. sp. and Lagenochitina aff. conifundus (Poumot), probable nektic elements and the first upper Tremadocian conodont and chitinozoan reported from Avalon, occur in diagenetic calcareous nodules in the dark gray-black mudstone. An upper Tremadocian transition from lower greenish to upper black mudstone is not exposed on McLeod Brook, but is comparable to a coeval green-black mudstone transition in Avalonian England. The successions suggest that late late Tremadocian (probable Baltic Hunnebergian Age) sea level was higher in Avalon than is suggested from successions on other paleocontinents. The Tremadocian sea-level history of Avalon was a shoaling-deepening-shoaling sequence from d-a black mudstone (lower Tremadocian), to dysoxic green mudstone (lower upper Tremadocian), and back to black mudstone (upper upper Tremadocian).Scandodus Lindström is emended, with the early species S. avalonensis Landing n. sp. assigned to the emended Family Protopanderodontidae. Triangulodus Van Wamel is considered a junior synonym of Scandodus. Peltocare rotundifrons is emended on the basis of complete specimens.

scholarly journals North SEAL: a new dataset of sea level changes in the North Sea from satellite altimetry

2021 ◽  
Vol 13 (8) ◽  
pp. 3733-3753
Author(s):  
Denise Dettmering ◽  
Felix L. Müller ◽  
Julius Oelsmann ◽  
Marcello Passaro ◽  
Christian Schwatke ◽  
...  
Keyword(s):  
Sea Level ◽  
North Sea ◽  
Tide Gauge ◽  
Sea Level Changes ◽  
Adaptation Measures ◽  
Isostatic Adjustment ◽  
The North ◽  
Sea Level Anomalies ◽  
Vertical Land Motion ◽  
The North Sea

Abstract. Information on sea level and its temporal and spatial variability is of great importance for various scientific, societal, and economic issues. This article reports about a new sea level dataset for the North Sea (named North SEAL) of monthly sea level anomalies (SLAs), absolute sea level trends, and amplitudes of the mean annual sea level cycle over the period 1995–2019. Uncertainties and quality flags are provided together with the data. The dataset has been created from multi-mission cross-calibrated altimetry data preprocessed with coastal dedicated approaches and gridded with an innovative least-squares procedure including an advanced outlier detection to a 6–8 km wide triangular mesh. The comparison of SLAs and tide gauge time series shows good consistency, with average correlations of 0.85 and maximum correlations of 0.93. The improvement with respect to existing global gridded altimetry solutions amounts to 8 %–10 %, and it is most pronounced in complicated coastal environments such as river mouths or regions sheltered by islands. The differences in trends at tide gauge locations depend on the vertical land motion model used to correct relative sea level trends. The best consistency with a median difference of 0.04±1.15 mm yr−1 is reached by applying a recent glacial isostatic adjustment (GIA) model. With the presented sea level dataset, for the first time, a regionally optimized product for the entire North Sea is made available. It will enable further investigations of ocean processes, sea level projections, and studies on coastal adaptation measures. The North SEAL data are available at https://doi.org/10.17882/79673 (Müller et al., 2021).

Sign in / Sign up

Export Citation Format

Share Document