Modeling sea level changes and geodetic variations by glacial isostasy: the improved SELEN code

We describe the basic features of SELEN, an open source Fortran 90 program for the numerical solution of the so-called "Sea Level Equation" for a spherical, layered, non-rotating Earth with Maxwell viscoelastic rheology. The Sea Level Equation was introduced in the 70s to model the sea level variations in response to the melting of late-Pleistocene ice-sheets, but it can be also employed for predictions of geodetic quantities such as vertical and horizontal surface displacements and gravity variations on a global and a regional scale. SELEN (acronym of SEa Level EquatioN solver) is particularly oriented to scientists at their first approach to the glacial isostatic adjustment problem and, according to our experience, it can be successfully used in teaching. The current release (2.9) considerably improves the previous versions of the code in terms of computational efficiency, portability and versatility. In this paper we describe the essentials of the theory behind the Sea Level Equation, the purposes of SELEN and its implementation, and we provide practical guidelines for the use of the program. Various examples showing how SELEN can be configured to solve geodynamical problems involving past and present sea level changes and current geodetic variations are also presented and discussed

Global and regional sea level variations in the recent past and future: insight from observations and modeling

This work is focused on the analysis of sea–level change (last century), based mainly on instrumental observations. During this period, individual components of sea–level change are investigated, both at global and regional scales. Some of the geophysical processes responsible for current sea-level change such as glacial isostatic adjustments and current melting terrestrial ice sources, have been modeled and compared with observations. A new value of global mean sea level change based of tide gauges observations has been independently assessed in 1.5 mm/year, using corrections for glacial isostatic adjustment obtained with different models as a criterion for the tide gauge selection. The long wavelength spatial variability of the main components of sea–level change has been investigated by means of traditional and new spectral methods. Complex non–linear trends and abrupt sea–level variations shown by tide gauges records have been addressed applying different approaches to regional case studies. The Ensemble Empirical Mode Decomposition technique has been used to analyse tide gauges records from the Adriatic Sea to ascertain the existence of cyclic sea-level variations. An Early Warning approach have been adopted to detect tipping points in sea–level records of North East Pacific and their relationship with oceanic modes. Global sea–level projections to year 2100 have been obtained by a semi-empirical approach based on the artificial neural network method. In addition, a model-based approach has been applied to the case of the Mediterranean Sea, obtaining sea-level projection to year 2050

The Bering Transitory Archipelago: stepping stones for the first Americans

Retrospective sea-level mapping advances a promising geographic solution to the longstanding mystery about when, where, and how the first Americans crossed over from Asia. A paleotopographic reconstruction accounting for Glacial Isostatic Adjustment digitally explores an archipelago about 1400 km long that likely existed from $>$30,000 BP to 8000 BP. Here the authors examine this Bering Transitory Archipelago in regard to established hypotheses—Clovis-first, Ice-free (deglaciation) Corridor, Kelp Highway, and Beringian Standstill hypotheses—and a new Stepping-Stones hypothesis. Scores of islands at that time would meet all requirements previously proposed for a viable hypothesis: a source population in Asia, a pathway with abundant sustenance, settlements in North America soon after but not before, and an isolated sanctuary where Beringians could have become genetically distinct

The Bering Transitory Archipelago: stepping stones for the first Americans

Retrospective sea-level mapping advances a promising geographic solution to the longstanding mystery about when, where, and how the first Americans crossed over from Asia. A paleotopographic reconstruction accounting for Glacial Isostatic Adjustment digitally explores an archipelago about 1400 km long that likely existed from $>$30,000 BP to 8000 BP. Here the authors examine this Bering Transitory Archipelago in regard to established hypotheses—Clovis-first, Ice-free (deglaciation) Corridor, Kelp Highway, and Beringian Standstill hypotheses—and a new Stepping-Stones hypothesis. Scores of islands at that time would meet all requirements previously proposed for a viable hypothesis: a source population in Asia, a pathway with abundant sustenance, settlements in North America soon after but not before, and an isolated sanctuary where Beringians could have become genetically distinct

How future surgery will benefit from SARS-COV-2-related measures: a SPIGC survey conveying the perspective of Italian surgeons

COVID-19 negatively affected surgical activity, but the potential benefits resulting from adopted measures remain unclear. The aim of this study was to evaluate the change in surgical activity and potential benefit from COVID-19 measures in perspective of Italian surgeons on behalf of SPIGC. A nationwide online survey on surgical practice before, during, and after COVID-19 pandemic was conducted in March-April 2022 (NCT:05323851). Effects of COVID-19 hospital-related measures on surgical patients' management and personal professional development across surgical specialties were explored. Data on demographics, pre-operative/peri-operative/post-operative management, and professional development were collected. Outcomes were matched with the corresponding volume. Four hundred and seventy-three respondents were included in final analysis across 14 surgical specialties. Since SARS-CoV-2 pandemic, application of telematic consultations (4.1% vs. 21.6%; p < 0.0001) and diagnostic evaluations (16.4% vs. 42.2%; p < 0.0001) increased. Elective surgical activities significantly reduced and surgeons opted more frequently for conservative management with a possible indication for elective (26.3% vs. 35.7%; p < 0.0001) or urgent (20.4% vs. 38.5%; p < 0.0001) surgery. All new COVID-related measures are perceived to be maintained in the future. Surgeons' personal education online increased from 12.6% (pre-COVID) to 86.6% (post-COVID; p < 0.0001). Online educational activities are considered a beneficial effect from COVID pandemic (56.4%). COVID-19 had a great impact on surgical specialties, with significant reduction of operation volume. However, some forced changes turned out to be benefits. Isolation measures pushed the use of telemedicine and telemetric devices for outpatient practice and favored communication for educational purposes and surgeon-patient/family communication. From the Italian surgeons' perspective, COVID-related measures will continue to influence future surgical clinical practice

Sea-level rise in the Mediterranean Sea by 2050: Roles of terrestrial ice melt, steric effects and glacial isostatic adjustment

To assess the regional pattern of future low-frequency sea-level variations in the Mediterranean Sea, we combine the terrestrial ice melt, the glacio-isostatic and the steric sea-level components. The first is obtained from global scenarios for the future mass balance of the Greenland and Antarctica ice sheets, glaciers and ice caps. The second is based on modeling, using different assumptions about the Earth's rheology and the chronology of deglaciation since the Last Glacial Maximum. The third is obtained from published simulations based on regional atmosphere–ocean coupled models. From a minimum and a maximum scenario by 2040–2050, we find that the total, basin averaged sea-level rise will be 9.8 and 25.6 cm. The terrestrial ice melt component will exceed the steric contribution, which however will show the strongest regional imprint. Glacial isostatic adjustment will have comparatively minor effects. According to our estimates, at the Mediterranean Sea tide gauges, the rate of sea-level change will increase, by 2050, by a factor of ~ 1–6 relative to the observed long-term rates

Linear and non-linear sea-level variations in the Adriatic Sea from tide gauge records (1872-2012)

We have analyzed tide gauge data from the Adriatic Sea in order to assess the secular sea-level trend, its acceleration and the existence of possible cyclic variation. Analyzing the sea-level stack of all Adriatic tide gauges, we have obtained a trend of (1.25\ub10.04) mm yr-1, in agreement with that observed for the last century in the Mediterranean Sea, and an acceleration that is negligibile compared to the average global values. By means of the Ensemble Empirical Mode Decomposition technique, we have evidenced an energetic oscillation with a period of 3c20 years that we relate with the recurrence of opposite phases in the Atlantic Multi\u2013decadal Oscillation and North Atlantic Oscillation indices. We suggest that anomalously high sea-level values observed at all the Adriatic tide gauges during 2010 and 2011 can be explained by the rising phase of this 20 years cycl

Tide gauge observations in Antarctica (1958–2014) and recent ice loss

Several historical sea level time series from Antarctic tide gauges, available from the Permanent Service for Mean Sea Level, are analysed. Two sea level curves, obtained by averaging data from the Antarctic Peninsula and West Antarctica, for 1958–2014, show trends of (2.0±0.1) and (1.8 ± 0.2) mm yr-1, respectively. By empirical mode decomposition, cyclic and non-cyclic components of sea level change were separated. A periodicity of 4–5 years was confirmed and attributed to the effects of the Antarctic Circumpolar Wave. The non-cyclic components were found to show a ‘levelling off’ of ≈ 1 mm yr-1 since c. 2000, which cannot be attributed to the isostatic response to Holocene ice melting. Using assessed mass balance data from the West Antarctic Ice Sheet and the Antarctic Peninsula, we studied the response to current ice loss in the region and found that the levelling off could be partly explained by accelerated melting during the last approximately two decades. This may represent the first evidence of sea level fingerprints of glacial melting in Antarctica

Extent and dynamic evolution of the lost land aquaterra since the Last Glacial Maximum

We study the evolution of a recently recognised global geographical feature, named aquaterra, enclosing those lands that in previous glacial cycles have been repeatedly exposed and flooded. So far, the geography of aquaterra has been studied as a first approximation neglecting the isostatic effects and assuming globally uniform (i.e. eustatic) sea-level variations. Focussing on the last deglaciation and considering both global and regional aspects, we show that isostatic effects related with mantle dynamics have indeed played a significant role in the evolution of aquaterra. Our analysis is based upon paleogeographic reconstructions in the framework of well-established Glacial Isostatic Adjustment theories