3.3 Regional variations in sea level rise
10 min read•august 21, 2024
Sea level rise varies significantly across regions, impacting coastal communities differently. Understanding these variations is crucial for developing effective coastal resilience strategies. Engineers must consider factors like , ocean circulation, and land movements when designing protection measures.
Monitoring sea level changes through and tide gauges provides vital data for coastal planning. This information helps identify hotspots of rapid sea level rise and areas experiencing sea level fall. Adaptation strategies range from hard engineering approaches to nature-based solutions, with becoming a consideration for highly vulnerable areas.
Global sea level trends
- Sea level trends play a crucial role in coastal resilience engineering by influencing the design and implementation of protective measures
- Understanding global patterns helps engineers anticipate future challenges and develop long-term strategies for coastal communities
- Regional variations in sea level rise necessitate localized approaches to coastal protection and adaptation
Eustatic vs relative sea level
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- Eustatic sea level refers to the global average ocean surface height relative to the center of the Earth
- Relative sea level measures the local height of the ocean surface relative to land, incorporating both water level changes and vertical land movements
- Eustatic sea level rise primarily driven by thermal expansion of oceans and melting of land-based ice (glaciers, ice sheets)
- Relative sea level can differ significantly from eustatic due to local factors (land , tectonic activity, sediment compaction)
Satellite altimetry measurements
- Satellite altimetry uses radar to measure sea surface height with high precision and global coverage
- Provides continuous, near-real-time data on sea level variations since the early 1990s
- Allows detection of regional differences in sea level rise rates and patterns
- Key satellites include TOPEX/Poseidon, Jason series, and Sentinel-6 Michael Freilich
- Accuracy of measurements has improved over time, now reaching millimeter-level precision
Tide gauge records
- Tide gauges measure local sea level relative to a fixed point on land
- Provide long-term historical data, with some records dating back to the 18th century
- Network of tide gauges distributed globally, but with uneven spatial coverage
- Used to calculate local sea level trends and validate satellite altimetry data
- Limitations include potential land movement at gauge locations and gaps in spatial coverage
Drivers of regional variations
- Regional variations in sea level rise significantly impact coastal resilience engineering strategies
- Understanding these drivers helps engineers develop targeted solutions for specific coastal areas
- Coastal resilience plans must account for the complex interplay of multiple factors affecting local sea levels
Thermal expansion patterns
- Oceans absorb over 90% of excess heat from global warming, leading to thermal expansion
- Expansion rates vary regionally due to differences in water temperature and salinity
- Deeper, warmer waters experience more significant expansion than shallower, cooler areas
- Western boundary currents (Gulf Stream, Kuroshio) show higher rates of thermal expansion
- Contributes to sea level rise "hotspots" in regions like the Western Pacific and North Atlantic
Ocean circulation changes
- Alterations in ocean currents and circulation patterns influence regional sea levels
- Weakening of the Atlantic Meridional Overturning Circulation (AMOC) affects sea levels along the US East Coast
- Changes in wind patterns and ocean gyres redistribute water masses, causing regional sea level variations
- -Southern Oscillation (ENSO) events temporarily shift water between the eastern and western Pacific
- Long-term changes in circulation patterns can lead to persistent regional sea level anomalies
Gravitational effects
- Melting of large ice sheets alters Earth's gravitational field, affecting regional sea levels
- As ice sheets lose mass, their gravitational pull on surrounding ocean waters decreases
- Leads to counterintuitive effects, such as sea level fall near rapidly melting ice sheets
- Regions far from melting ice sheets experience higher-than-average sea level rise
- Gravitational effects from Greenland and Antarctic ice sheet melt contribute to regional variations
Vertical land movements
- Vertical land motion significantly influences relative sea level changes at local scales
- Glacial isostatic adjustment (GIA) causes land in formerly glaciated regions and subsidence in peripheral areas
- Tectonic activity can lead to rapid land uplift or subsidence in seismically active regions
- Sediment compaction and groundwater extraction cause land subsidence in many coastal areas
- Human activities (oil and gas extraction, urbanization) can accelerate local land subsidence rates
Hotspots of sea level rise
- Sea level rise hotspots present unique challenges for coastal resilience engineering
- These areas require more immediate and extensive adaptation measures
- Understanding the causes of accelerated sea level rise in hotspots informs the development of targeted solutions
US East Coast
- Experiencing faster-than-average sea level rise, particularly in the Mid-Atlantic region
- Factors contributing to accelerated rise include land subsidence, changes in Gulf Stream dynamics, and gravitational effects
- Norfolk, Virginia, and Charleston, South Carolina, face increased flooding frequency and intensity
- Coastal communities implementing various adaptation strategies (elevating structures, improving drainage systems, constructing sea walls)
- Long-term planning considers managed retreat options for highly vulnerable areas
Western Pacific
- Region experiencing some of the highest rates of sea level rise globally
- Small island nations (Tuvalu, Marshall Islands, Kiribati) particularly vulnerable to sea level rise impacts
- Factors driving rapid rise include thermal expansion, changes in trade wind patterns, and gravitational effects
- Adaptation strategies focus on enhancing natural coastal defenses (coral reef restoration, mangrove planting)
- Some islands exploring innovative solutions like artificial island construction or floating structures
Indian Ocean
- Parts of the Indian Ocean basin showing accelerated sea level rise
- Bay of Bengal region particularly vulnerable due to low-lying coastal areas and high population density
- Maldives facing existential threat from sea level rise, with over 80% of land area less than 1 meter above sea level
- Factors contributing to rapid rise include thermal expansion, changes in monsoon patterns, and gravitational effects
- Adaptation efforts include coastal protection measures, raising island elevations, and exploring relocation options
Areas of sea level fall
- Regions experiencing sea level fall present unique challenges for coastal engineering and management
- Understanding the causes of sea level fall is crucial for developing appropriate adaptation strategies
- These areas often require different approaches compared to regions facing sea level rise
Glacial isostatic adjustment regions
- GIA causes land uplift in formerly glaciated areas, leading to relative sea level fall
- Scandinavia experiencing land uplift rates of up to 1 cm per year in some areas
- Hudson Bay region in Canada also showing significant land uplift and relative sea level fall
- Coastal infrastructure in these regions may need adaptation to changing water levels (harbor facilities, coastal defenses)
- Long-term planning must consider continued land uplift and its effects on coastal ecosystems and human activities
Tectonic uplift zones
- Tectonic activity can cause rapid land uplift, resulting in local sea level fall
- Alaska's coastline experiencing uplift due to plate tectonics and post-glacial rebound
- Parts of Chile's coast show uplift following major earthquakes (2010 Maule earthquake raised coastline by up to 2 meters)
- Coastal management in these areas must account for sudden changes in land elevation
- Adaptation strategies include reassessing flood risk zones and adjusting coastal infrastructure designs
Temporal variability
- Temporal variability in sea level rise poses challenges for coastal resilience engineering
- Understanding different timescales of variability is crucial for effective planning and adaptation
- Engineers must consider short-term fluctuations and long-term trends when designing coastal protection measures
Interannual fluctuations
- Sea levels exhibit significant year-to-year variations due to natural climate patterns
- El Niño-Southern Oscillation (ENSO) causes temporary sea level changes of up to 20-30 cm in the Pacific
- Indian Ocean Dipole affects sea levels in the Indian Ocean basin on interannual timescales
- influences sea levels along European and North American coasts
- Coastal resilience strategies must account for these short-term fluctuations in addition to long-term trends
Decadal oscillations
- Longer-term climate patterns cause sea level variations over periods of 10-30 years
- Pacific Decadal Oscillation (PDO) affects sea levels in the North Pacific region
- Atlantic Multidecadal Oscillation (AMO) influences sea levels in the North Atlantic basin
- These oscillations can temporarily accelerate or decelerate regional sea level rise rates
- Understanding decadal variability helps in distinguishing long-term trends from natural fluctuations
Long-term projections
- IPCC projections provide estimates of future sea level rise under different emissions scenarios
- Global mean sea level rise likely to reach 0.43-0.84 m by 2100 under high emissions scenario (RCP8.5)
- Regional variations in sea level rise expected to persist and potentially intensify
- Long-term projections consider factors such as ice sheet dynamics, ocean circulation changes, and land subsidence
- Coastal resilience planning must incorporate uncertainty in long-term projections and adopt adaptive management approaches
Impacts on coastal communities
- Understanding impacts of sea level rise on coastal communities is crucial for resilience engineering
- Coastal engineers must consider multiple interconnected effects when designing adaptation strategies
- Impacts vary regionally, requiring localized assessments and tailored solutions
Flooding frequency
- Sea level rise increases the frequency and severity of coastal flooding events
- Nuisance flooding (sunny day flooding) becoming more common in low-lying coastal areas
- Storm surge impacts exacerbated by higher baseline sea levels
- Flood risk maps and insurance rates require regular updates to reflect changing conditions
- Adaptation measures include improved drainage systems, flood barriers, and elevation of critical infrastructure
Saltwater intrusion
- Rising sea levels push saltwater further inland, contaminating freshwater aquifers
- Threatens drinking water supplies and agricultural productivity in coastal regions
- Miami-Dade County, Florida, facing challenges with saltwater intrusion into the Biscayne Aquifer
- Adaptation strategies include desalination plants, water conservation measures, and managed aquifer recharge
- Long-term planning may require relocation of water supply wells further inland
Coastal erosion patterns
- Sea level rise accelerates coastal erosion processes, threatening beaches and coastal infrastructure
- Erosion rates vary depending on local geology, wave climate, and sediment supply
- Barrier islands particularly vulnerable to increased erosion and potential breaching
- Adaptation approaches include beach nourishment, construction of groins and breakwaters, and managed realignment
- Nature-based solutions (dune restoration, wetland creation) gaining popularity for erosion control
Adaptation strategies
- Coastal resilience engineering employs various adaptation strategies to address sea level rise challenges
- Effective adaptation requires a combination of approaches tailored to local conditions and needs
- Engineers must consider long-term sustainability and flexibility when designing adaptation measures
Hard vs soft engineering approaches
- Hard engineering involves construction of physical structures to protect coastlines
- Examples include sea walls, levees, storm surge barriers, and groins
- Soft engineering focuses on working with natural processes to enhance coastal resilience
- Soft approaches include beach nourishment, dune restoration, and wetland creation
- Hybrid solutions combining hard and soft techniques gaining popularity (living shorelines)
Managed retreat options
- Managed retreat involves planned relocation of people and assets away from high-risk coastal areas
- Increasingly considered as a long-term strategy for highly vulnerable communities
- Challenges include social and economic impacts, land acquisition, and community resistance
- Successful examples include relocation of Soldiers Grove, Wisconsin, away from flood-prone areas
- Requires comprehensive planning, stakeholder engagement, and financial support mechanisms
Nature-based solutions
- Nature-based solutions harness ecosystem services to enhance coastal resilience
- Mangrove restoration provides natural storm protection and carbon sequestration benefits
- Coral reef rehabilitation helps dissipate wave energy and reduce coastal erosion
- Constructed wetlands act as natural buffers against storm surge and improve water quality
- (rain gardens, bioswales) manages stormwater runoff in urban coastal areas
Monitoring and prediction
- Effective monitoring and prediction systems are essential for coastal resilience engineering
- Accurate data and forecasts inform decision-making and adaptive management strategies
- Continuous improvement of monitoring technologies enhances our understanding of sea level dynamics
Tide gauge networks
- Global network of tide gauges provides long-term sea level observations at coastal locations
- Data used for tidal predictions, storm surge warnings, and long-term sea level trend analysis
- GLOSS (Global Sea Level Observing System) coordinates international tide gauge network
- Modern tide gauges equipped with GPS to account for vertical land motion
- Integration of with satellite observations improves overall sea level monitoring
Satellite observations
- Satellite altimetry provides global coverage of sea surface height measurements
- Gravity missions (GRACE, GRACE-FO) monitor changes in ice sheet mass and ocean mass distribution
- InSAR (Interferometric Synthetic Aperture Radar) measures land subsidence in coastal areas
- Satellite-derived wind and wave data support coastal hydrodynamic modeling
- Future missions (SWOT) will improve monitoring of coastal and estuarine water levels
Numerical modeling techniques
- Hydrodynamic models simulate coastal processes and predict impacts of sea level rise
- Coupled atmosphere-ocean models project future sea level changes under different scenarios
- Data assimilation techniques combine observations with models to improve forecasts
- Machine learning algorithms increasingly used for pattern recognition and prediction in sea level data
- Ensemble modeling approaches account for uncertainties in sea level projections
Policy implications
- Coastal resilience engineering intersects with policy decisions at local, national, and international levels
- Effective policies support the implementation of adaptation strategies and long-term planning
- Engineers play a crucial role in informing policy decisions through technical expertise and risk assessments
Risk assessment frameworks
- Standardized risk assessment methodologies help prioritize adaptation efforts
- Incorporate multiple factors (sea level rise projections, exposure, vulnerability, adaptive capacity)
- IPCC risk framework widely used for climate change impact assessments
- US Army Corps of Engineers sea level change curves guide infrastructure planning
- Regular updates to risk assessments necessary to reflect latest scientific understanding
Coastal zone management
- Integrated Coastal Zone Management (ICZM) approaches coordinate multiple stakeholders and sectors
- Coastal setback policies regulate development in high-risk areas
- Building codes and zoning regulations adapted to account for future sea level rise
- Ecosystem-based management approaches integrate natural systems into coastal planning
- Adaptive management strategies allow for flexibility in response to changing conditions
International cooperation efforts
- Sea level rise is a global challenge requiring international collaboration
- Paris Agreement includes provisions for climate change adaptation and resilience
- Small Island Developing States (SIDS) advocate for increased support in international forums
- Regional initiatives (Mediterranean Action Plan, Baltic Sea Region Climate Change Adaptation Strategy) address shared challenges
- Knowledge sharing platforms (C40 Cities, 100 Resilient Cities) facilitate exchange of best practices in coastal resilience
Key Terms to Review (18)
Absolute sea level rise: Absolute sea level rise refers to the increase in the overall height of the ocean surface measured relative to a fixed point on land. This phenomenon is primarily caused by two key factors: thermal expansion of seawater as it warms and the addition of water from melting ice sheets and glaciers. Understanding absolute sea level rise is essential for assessing regional variations, as different areas experience varying rates due to factors like land subsidence, ocean currents, and local climate conditions.
Coastal topography: Coastal topography refers to the physical features and configurations of the land along coastlines, including the shapes, elevations, and contours of the land that meet the sea. It plays a crucial role in understanding how these coastal features interact with natural processes such as tides, waves, and sea level rise, influencing both ecological systems and human development in coastal areas.
Displacement: Displacement refers to the forced movement of people or communities from their homes or traditional lands, often due to environmental changes, natural disasters, or human-induced factors. This phenomenon can lead to significant social, economic, and cultural challenges as affected populations struggle to adapt to new environments or rebuild their lives, especially in the context of increasing storm intensity, coastal flooding, and rising sea levels.
El Niño: El Niño is a climate pattern characterized by the periodic warming of ocean surface temperatures in the central and eastern Pacific Ocean, which significantly influences global weather patterns. This phenomenon can lead to various regional climate impacts, including increased rainfall and flooding in some areas and droughts in others. Understanding El Niño is essential for predicting and managing its effects on sea level rise, particularly in coastal regions.
Glacial melting: Glacial melting refers to the process in which glaciers and ice sheets lose mass due to the effects of rising temperatures, resulting in the transformation of solid ice into liquid water. This phenomenon is a significant contributor to sea level rise and has varying impacts on different regions around the world, influencing ocean currents, ecosystems, and weather patterns.
Green Infrastructure: Green infrastructure refers to a strategically planned network of natural and semi-natural areas that provide environmental, economic, and social benefits, especially in urban settings. It integrates natural processes with built environments to manage stormwater, enhance biodiversity, and improve air quality while also offering recreational spaces and aesthetic value.
Kerry Emanuel: Kerry Emanuel is a prominent climate scientist known for his research on hurricanes and the impact of climate change on storm intensity. His work has significantly contributed to understanding how regional variations in sea level rise can influence hurricane behavior and coastal resilience. By examining the interplay between atmospheric conditions and oceanic factors, he highlights the importance of considering these elements in assessing future storm risks and vulnerabilities along coastlines.
Managed retreat: Managed retreat is a strategic approach to climate adaptation that involves relocating human populations and infrastructure away from vulnerable coastal areas to reduce risks associated with sea level rise, flooding, and erosion. This concept balances the need for human safety with environmental sustainability by allowing natural coastal processes to occur while minimizing human impact.
North Atlantic Oscillation: The North Atlantic Oscillation (NAO) is a climatic phenomenon characterized by fluctuating atmospheric pressure differences between the Azores high and the Icelandic low, influencing weather patterns across the North Atlantic region. It plays a significant role in determining storm tracks, precipitation patterns, and temperature variations in Europe and North America. Changes in the NAO can lead to extreme weather events, affecting both storm intensity and sea level rise through various interconnected processes.
Relative sea level rise: Relative sea level rise refers to the change in the height of sea levels in relation to a specific point on land, taking into account factors such as land subsidence and ocean dynamics. This concept is crucial for understanding how different regions experience varying degrees of sea level changes due to both global sea level rise and local geological conditions.
Robert Nicholls: Robert Nicholls is a prominent researcher in coastal engineering and resilience, recognized for his contributions to understanding the impacts of climate change on coastal systems. His work emphasizes the importance of integrating scientific research with policy and management strategies to enhance coastal resilience and address issues related to sea level rise, which is crucial for coastal livelihoods and economies as well as regional variations in sea level rise.
Satellite altimetry: Satellite altimetry is a remote sensing technology that measures the distance between a satellite and the Earth's surface to determine variations in sea surface height. This technique provides critical data for monitoring sea level rise, understanding ocean dynamics, and assessing changes in regional sea levels, making it essential for various studies related to coastal resilience and climate change.
Subsidence: Subsidence is the gradual sinking or settling of the Earth's surface due to various factors, including geological processes, the extraction of resources, or the compaction of sediments. This phenomenon can lead to significant hazards, particularly in coastal regions where land sinks and increases vulnerability to flooding and erosion, as well as impacting land stability in areas prone to landslides.
Thermal expansion: Thermal expansion is the process by which matter increases in volume as its temperature rises. This phenomenon is significant in the context of oceans, as the warming of seawater due to climate change leads to an increase in ocean volume, contributing to rising sea levels. Understanding thermal expansion is crucial for analyzing global sea level trends and regional variations, particularly how different areas may experience varying impacts from climate-induced changes in temperature.
Tidal Range: Tidal range refers to the vertical difference between high tide and low tide in a particular coastal area. This measurement is crucial as it influences various natural processes, including sediment transport, coastal erosion, and habitat dynamics. Understanding tidal range also plays an important role in managing coastal development and anticipating the effects of sea level rise on coastal communities.
Tide Gauge Data: Tide gauge data refers to the information collected by instruments that measure the change in sea level relative to a fixed point on land over time. These measurements are essential for understanding patterns of sea level rise, as they provide localized and historical context. By analyzing tide gauge data, scientists can identify regional variations in sea level change, which are influenced by factors such as land subsidence, ocean currents, and climate change impacts.
Uplift: Uplift refers to the geological process where the Earth's crust is raised due to tectonic forces, volcanic activity, or other natural phenomena. This process can significantly influence regional sea levels, as areas that experience uplift may see a relative decrease in sea level, while adjacent regions may not experience the same effects. Understanding uplift is crucial for assessing regional variations in sea level rise and how it impacts coastal resilience.
Vulnerability Assessment: A vulnerability assessment is a systematic process used to identify, evaluate, and prioritize the weaknesses and risks faced by a community, ecosystem, or infrastructure due to environmental hazards. This assessment helps in understanding how various factors, such as coastal erosion, extreme weather events, and rising sea levels, can impact communities and their resilience against these threats.