are a critical aspect of Coastal Resilience Engineering. Historical records, including and geological evidence, provide insights into past sea levels, while offers precise modern measurements. Understanding these trends is crucial for predicting future coastal changes and developing .
Sea level rise results from complex interactions between oceans, atmosphere, and ice. of oceans and melting land-based ice are major contributors. Regional variations, caused by factors like and , complicate the global picture. This knowledge is essential for effective coastal management and engineering solutions.
Historical sea level records
Sea level records provide crucial insights into past climate conditions and help predict future coastal changes in Coastal Resilience Engineering
Understanding historical sea level trends informs adaptation strategies for coastal communities and
Combining multiple data sources enhances the accuracy and reliability of long-term sea level reconstructions
Tide gauge measurements
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ESSD - North SEAL: a new dataset of sea level changes in the North Sea from satellite altimetry View original
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OS - Metrics - Global sea level reconstruction for 1900–2015 reveals regional variability in ... View original
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Global Warming: How much will sea levels rise in the 21st Century? | Small Epiphanies View original
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ESSD - North SEAL: a new dataset of sea level changes in the North Sea from satellite altimetry View original
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Top images from around the web for Tide gauge measurements
ESSD - North SEAL: a new dataset of sea level changes in the North Sea from satellite altimetry View original
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OS - Metrics - Global sea level reconstruction for 1900–2015 reveals regional variability in ... View original
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Global Warming: How much will sea levels rise in the 21st Century? | Small Epiphanies View original
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ESSD - North SEAL: a new dataset of sea level changes in the North Sea from satellite altimetry View original
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OS - Metrics - Global sea level reconstruction for 1900–2015 reveals regional variability in ... View original
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Continuous sea level observations recorded by mechanical float gauges since the 18th century
Network of tide gauges globally measures local sea level changes relative to a fixed point on land
Longest tide gauge record from Amsterdam dates back to 1700
Challenges include accounting for vertical land movements and uneven global distribution of gauges
Geological evidence
Provides sea level data over much longer timescales (thousands to millions of years)
Includes analysis of coral reefs, marine terraces, and sediment cores
Microfossils (foraminifera) in sediment cores indicate past sea levels and environmental conditions
Reconstructs sea level history during past warm periods (interglacials) for comparison with current trends
Satellite altimetry data
Space-based measurements of global sea surface height since 1992
Satellites (TOPEX/Poseidon, Jason series) use radar to measure distance between satellite and sea surface
Provides near-global coverage and high-precision measurements (accuracy of a few centimeters)
Allows detection of regional variations and short-term fluctuations in sea level
Causes of global sea level rise
Global sea level rise results from complex interactions between ocean, atmosphere, and cryosphere systems
Understanding these causes is essential for accurate projections and effective coastal management strategies
Coastal Resilience Engineering must account for multiple contributing factors to develop comprehensive adaptation plans
Thermal expansion of oceans
Occurs as seawater warms and increases in volume
Responsible for about 30-50% of observed global sea level rise since 1971
Rate of thermal expansion varies with depth and location in the ocean
Deeper, colder waters expand more than surface waters for the same temperature increase
Melting of land-based ice
Contributes freshwater to the oceans, raising global sea level
Major sources include glaciers, ice caps, and ice sheets (Greenland and Antarctica)
Greenland Ice Sheet loss has accelerated, contributing about 0.7 mm/year to sea level rise
Antarctic Ice Sheet contribution remains uncertain but potentially significant for future sea level rise
Groundwater extraction vs storage
Groundwater depletion adds water to the oceans, raising sea level
Estimated contribution of 0.3-0.4 mm/year to global sea level rise
Counteracted by increased water storage in artificial reservoirs and dams
Net effect on sea level depends on balance between extraction and storage over time
Regional variations in sea level
Sea level changes are not uniform globally, with significant regional differences
Understanding regional variations crucial for local coastal management and adaptation planning
Coastal Resilience Engineering must consider site-specific sea level trends for effective design and implementation
Vertical land movements
Caused by geological processes (tectonics, isostatic rebound) and human activities (subsidence)
Post-glacial rebound raises land in formerly glaciated regions (Scandinavia, Canada)
Subsidence in delta regions due to sediment compaction and
Can amplify or reduce relative sea level rise at local scales
Ocean circulation patterns
Influence regional sea level through redistribution of heat and mass
Changes in major currents (Gulf Stream, Antarctic Circumpolar Current) affect local sea levels
El Niño-Southern Oscillation (ENSO) causes temporary sea level variations in the Pacific
Long-term changes in ocean circulation can lead to persistent regional sea level anomalies
Gravitational effects
Redistribution of mass from melting ice sheets alters Earth's gravitational field
Leads to lower sea level rise near melting ice sheets and higher rise in distant locations
Greenland ice loss causes sea level to fall nearby but rise more in the Southern Hemisphere
Complicates global sea level projections and requires consideration in regional assessments
Observed global sea level trends
Monitoring global sea level trends essential for understanding on coastal systems
Observed trends inform policy decisions and adaptation strategies in Coastal Resilience Engineering
Combining multiple data sources provides a comprehensive picture of past and present sea level changes
20th century rates
Average rate of global sea level rise during the 20th century estimated at 1.7 mm/year
Acceleration observed in the latter half of the century
Tide gauge records show significant spatial and temporal variability
Reconstruction methods combine tide gauge data with proxy records to estimate global trends
Recent acceleration
Satellite altimetry reveals global mean sea level rise of 3.3 mm/year since 1993
Acceleration detected in the altimetry record, with rates increasing to 4.5 mm/year in recent years
Increased contributions from ice sheet melting and thermal expansion drive acceleration
Observed acceleration consistent with projections from climate models
Projections for 21st century
IPCC projects global mean sea level rise of 0.43-0.84 m by 2100 under intermediate emissions scenario
High-end scenarios suggest potential rise exceeding 1 m by 2100
Long-term projections indicate continued sea level rise for centuries due to thermal inertia of oceans
Uncertainties in future emissions and ice sheet dynamics affect projection accuracy
Impacts on coastal systems
Sea level rise poses significant challenges to coastal environments and human settlements
Coastal Resilience Engineering focuses on mitigating these impacts through adaptive strategies
Understanding and quantifying impacts essential for effective coastal management and planning
Coastal erosion and flooding
Increased wave energy and storm surge heights exacerbate
Low-lying areas face more frequent and severe flooding events
Shoreline retreat threatens coastal infrastructure and habitats
Adaptation measures include beach nourishment, , and
Saltwater intrusion
Rising sea levels push saltwater further inland in coastal aquifers and estuaries
Threatens freshwater resources for drinking water and agriculture
Alters soil chemistry and impacts coastal vegetation
Mitigation strategies include improved water management and desalination technologies
Ecosystem changes
Inundation of coastal wetlands and mangroves leads to habitat loss
Shifts in species distribution and composition of coastal ecosystems
Coral reefs face increased stress from sea level rise combined with ocean warming and acidification
(living shorelines) can enhance ecosystem resilience to sea level rise
Measurement techniques and technologies
Accurate and precise measurements crucial for understanding sea level changes
Advances in technology improve spatial and temporal resolution of sea level data
Integration of multiple measurement techniques enhances overall understanding of sea level dynamics
Tide gauges vs satellite altimetry
Tide gauges provide long-term local records but limited spatial coverage
Satellite altimetry offers near-global coverage but shorter time series
Combining both methods allows for cross-validation and improved accuracy
Tide gauges essential for calibrating satellite measurements and studying local effects
GPS and geodetic observations
GPS measurements track vertical land movements at tide gauge locations
Improves accuracy of relative sea level trends derived from tide gauges
Geodetic techniques (VLBI, SLR) provide reference frame for satellite altimetry
Continuous GPS networks monitor regional land deformation patterns
Gravimetry for mass changes
GRACE satellite mission measures changes in Earth's gravity field
Allows estimation of ocean mass changes contributing to sea level rise
Distinguishes between steric (thermal expansion) and mass-related sea level changes
Provides insights into ice sheet mass balance and terrestrial water storage variations
Uncertainties and challenges
Addressing uncertainties crucial for improving sea level projections and risk assessments
Challenges in sea level science inform research priorities and data collection strategies
Understanding limitations essential for effective communication of sea level risks to stakeholders
Data quality and coverage
Historical tide gauge records have varying quality and may contain gaps
Uneven global distribution of tide gauges limits understanding of regional variations
Satellite altimetry faces challenges in coastal areas and high latitudes
Efforts to digitize historical records and expand monitoring networks ongoing
Natural variability vs long-term trends
Interannual to decadal climate oscillations (ENSO, PDO) influence sea level
Distinguishing natural variability from anthropogenic trends requires long time series
Statistical methods (empirical mode decomposition) help separate different timescales
Understanding natural variability crucial for detecting acceleration in sea level rise
Model limitations
Climate models struggle to accurately represent all processes affecting sea level
Ice sheet dynamics and ocean-ice interactions not fully captured in current models
Uncertainties in future emissions scenarios affect long-term projections
Ensemble approaches and model intercomparison projects address model limitations
Future scenarios and projections
Projecting future sea level rise essential for long-term coastal planning and adaptation
Multiple scenarios consider different emissions pathways and socioeconomic developments
Coastal Resilience Engineering must account for range of possible future sea level scenarios