GY411 Lecture 2: Cryosphere and Sea Level Changes

A comprehensive vocabulary review deck detailing emission scenarios (RCPs/SSPs), cryospheric components, glacio-isostatic and eustatic sea level mechanisms, permafrost systems, and the Coastal Hazard Wheel framework.

Representative Concentration Pathways (RCPs)

Greenhouse gas concentration trajectories adopted by the IPCC (used in AR5 and the SROCC) that describe potential future radiative forcing pathways and warming projections through 2100.

Shared Socioeconomic Pathways (SSPs)

A framework of five narrative pathways used in the IPCC Sixth Assessment Report that combine socioeconomic developments (such as population, education, and economy) with greenhouse gas emission projections.

SSP1 (Sustainability – Taking the Green Road)

A socioeconomic development pathway characterized by low challenges to both climate change mitigation and adaptation, prioritizing inclusive development, environmental respect, and rapid emission cuts.

SSP3 (Regional Rivalry – A Rocky Road)

A socioeconomic development pathway characterized by high challenges to both mitigation and adaptation, marked by regional security focus, national competitiveness, and slow technological progress.

SSP5 (Fossil-Fueled Development – Taking the Highway)

A socioeconomic development pathway characterized by high challenges to mitigation but low challenges to adaptation, driven by rapid economic growth reliant on energy-intensive fossil fuel exploitation.

Sea Level Equivalent (SLE)

The total global mean sea level rise that would result if a given grounded ice mass, such as the Antarctic Ice Sheet ($58\,\text{m}$ SLE) or Greenland Ice Sheet ($7\,\text{m}$ SLE), melted completely into the ocean.

Glacio-Eustatic Sea Level Change

A global sea level change resulting from variations in the volume of ocean water caused by the growth or melting of land-based glacial ice sheets and glaciers.

Eustatic Sea Level

The absolute altitude of the global ocean surface determined by the total volume of ocean water and the capacity of the global ocean basins.

Relative Sea Level Change

Local or regional changes in the position of sea level relative to the land surface, determined by a combination of vertical land movements (uplift or subsidence) and changes in the ocean surface altitude.

Glacio-Isostatic Adjustment (GIA)

The ongoing vertical deformation and adjustment of the Earth's crust and mantle in response to the loading and unloading of mass from continental ice sheets.

Forebulge

A flexural upward bulge of the Earth's lithosphere surrounding an ice sheet, caused by the displacement of mantle material under the weight of the ice sheet, which subsequently collapses during post-glacial rebound.

Marine Terrace

A wave-cut coastal platform or erosional bench abandoned above present sea level due to tectonic uplift, glacio-isostatic rebound, or relative sea level fall.

Paleo-Tidal Notch

An uplifted or submerged undercut indentation in a coastal cliff produced by bio-erosion, chemical dissolution, and wave action at the former intertidal level.

Elevation Dependent Warming (EDW)

The phenomenon wherein higher-elevation mountainous regions experience significantly higher warming rates than adjacent lower-altitude surrounding regions.

Glacial Lake Outburst Flood (GLOF)

A sudden, catastrophic release of meltwater stored in a proglacial or supraglacial lake caused by the collapse of a moraine or ice dam.

Permafrost

Any ground (rock, soil, or sediment) that remains at or below $0^\circ\text{C}$ for at least two consecutive years, defined strictly by thermal state rather than ice content.

Active Layer

The upper layer of ground overlying permafrost that undergoes seasonal cycles of freezing in winter and thawing in summer.

Active Layer Thickness (ALT)

The maximum vertical depth to which the seasonally thawed layer of soil or sediment extends above the underlying permafrost during the warm season.

Continuous Permafrost

A permafrost distribution zone where permanently frozen ground underlies greater than $90\%$ of the exposed land area.

Discontinuous Permafrost

A permafrost distribution zone where frozen ground underlies between $50\%$ and $90\%$ of the regional land area.

Sporadic Permafrost

A permafrost distribution zone where permafrost underlies between $10\%$ and $50\%$ of the regional landscape.

Isolated Permafrost

A permafrost distribution zone characterized by individual patches of frozen ground underlying less than $10\%$ of the regional terrain.

Thermokarst

An irregular, uneven land surface of depressions, sinkholes, and thaw slumps produced by the melting of ground ice in degrading permafrost terrain.

Patterned Ground

Distinct geometric surface forms (such as stone rings, polygons, circles, or stripes) created by repeated cryoturbation and frost heave in periglacial areas.

Permafrost Carbon Feedback

A self-reinforcing positive feedback cycle in which warming thaws permafrost, allowing microbes to decompose ancient organic carbon and release $\text{CO}_2$ and $\text{CH}_4$, further intensifying atmospheric warming.

Coastal Hazard

A threatening event or the probability of occurrence of a damaging physical phenomenon within a given coastal area and time period.

Coastal Risk

The expected loss of life, injury, property damage, and economic disruption resulting from a coastal hazard, calculated mathematically as the product of hazard, vulnerability, and exposure.

Coastal Vulnerability

The degree to which a human, infrastructural, or ecological coastal system is susceptible to, and unable to cope with, adverse effects or harm.

Coastal Resilience

The inherent ability of a geomorphic, ecological, or socioeconomic coastal system to absorb shocks or major disturbances (such as extreme storms) and bounce back to a functional state.

Coastal Adaptation Responses

Strategies deployed to address sea level rise and coastal hazards, classified into six main types: no response, advance, protection, retreat, accommodation, and ecosystem-based adaptation.

Sendai Framework for Disaster Risk Reduction

A United Nations agreement (2015–2030) outlining four priority actions and seven global targets to substantially reduce disaster mortality, affected populations, and direct economic losses.

Coastal Hazard Wheel (CHW)

A universal decision-support system and coastal classification methodology dividing coastlines into 131 environments to assess multi-hazards, determine management actions, and standardize coastal risk language.

Sedimentary Plain Coast

A coastal geological layout category in the CHW composed of soft sedimentary deposits with an average elevation of less than $6\text{--}8\,\text{m}$ within $500\,\text{m}$ inland of Mean Sea Level.

Barrier Coast

A low-lying coastal system consisting of shore-parallel sedimentary bodies that separate open-water wave environments seaward from sheltered lagoonal or backbarrier waters landward.

Sloping Soft Rock Coast

A coastal geological layout category in the CHW composed of soft, erodible rock material forming cliffs or gentle slopes with an elevation greater than $6\text{--}8\,\text{m}$ within $500\,\text{m}$ inland.

Coral Island Coast

A low-lying tropical oceanic landform consisting either of coral atolls formed on subsiding volcanic bases or coral cays constructed from wave-accumulated biogenic reef sediments.

Tidal Inlet / Sand Spit / River Mouth (T/S/R)

A high-priority dynamic geological sector in the CHW encompassing active river mouths, barrier breach channels, and elongate drift-aligned spits.

Micro-Tidal Environment

A tidal regime defined within the Coastal Hazard Wheel system by an astronomical spring tidal range of less than $2\,\text{m}$.

Meso/Macro-Tidal Environment

A combined tidal category in the CHW encompassing coastlines with tidal ranges of $2\text{--}4\,\text{m}$ (meso-tidal) and greater than $4\,\text{m}$ (macro-tidal).

Sediment Balance (CHW)

A dynamic coastal classification parameter evaluating whether a sedimentary or soft-rock coastline is in net balance/deficit ($\text{B/D}$) or surplus ($\text{Sur}$), evaluated via historical coastal vegetation lines.

Gradual Inundation (CHW Hazard)

The progressive long-term submergence of coastal lowlands resulting directly from projected relative sea level rise under global climate change.

Salt Water Intrusion (CHW Hazard)

The landward penetration and contamination of coastal freshwater aquifers, estuaries, and surface soils by marine saline water.

Ecosystem Disruption (CHW Hazard)

The potential collapse, alteration, or state shift in coastal ecological habitats (such as salt marshes, mangroves, and biogenic reefs) due to climate change impacts.

Ecosystem-Based Adaptation (EbA)

An adaptation approach that harnesses nature-based features, such as mangroves, dune systems, and coastal wetlands, to reduce wave impact, limit storm surges, and buffer sea level rise.