Imagine our planet sipping from the oceans, causing sea levels to creep up over a century, but new data reveals that gentle sip has turned into a concerning gulp.
Key Takeaways
- Global mean sea level rose by 1.7 mm per year from 1900 to 2018, totaling approximately 21-24 cm since 1880 with acceleration in recent decades.
- U.S. coastal sea levels have risen by 23 cm (9 inches) since 1880, faster than the global average due to land subsidence.
- Tide gauge records from 1901-2010 show a global sea level rise of 19 cm (7.5 inches).
- Global mean sea level rose 3.7 mm/yr from 2006-2015, the highest decadal rate on record.
- Satellite altimetry shows 4.3 mm/yr rise in 2020.
- NOAA tide gauges report U.S. average 3.8 mm/yr 2010-2020.
- Global mean sea level to rise 0.28-0.55 m by 2100 under SSP1-2.6 (low emissions).
- Under SSP5-8.5 (high emissions), global SLR projected at 0.63-1.01 m by 2100.
- U.S. East Coast projected 0.3-0.8 m by 2050 relative to 2000.
- Global mean sea level rise primarily driven by ocean thermal expansion (42%) and glacier melt (21%) since 1971.
- Greenland Ice Sheet mass loss averaged 169 Gt/yr 1992-2020, contributing 21% to SLR.
- Antarctic Ice Sheet contributed 7.4 mm to SLR 1992-2017 via 2520 Gt loss.
- U.S. East Coast experiences 3-4 times global average SLR due to AMOC slowdown.
- Gulf of Mexico relative SLR 2x global due to subsidence.
- Western Pacific Warm Pool sees 12 cm/decade rise.
Sea levels are rising globally at an accelerating pace.
Causes and Contributing Factors
- Global mean sea level rise primarily driven by ocean thermal expansion (42%) and glacier melt (21%) since 1971.
- Greenland Ice Sheet mass loss averaged 169 Gt/yr 1992-2020, contributing 21% to SLR.
- Antarctic Ice Sheet contributed 7.4 mm to SLR 1992-2017 via 2520 Gt loss.
- Glaciers outside Greenland/Antarctica lost 227 Gt/yr 2000-2019, 48% of SLR.
- Terrestrial water storage change net -76 Gt/yr 1993-2018, subtracting 0.4 mm SLR.
- Ocean warming caused 50% of 20th century SLR via thermal expansion.
- Thwaites Glacier instability from warm ocean water, potential 65 cm SLR.
- Groundwater depletion contributes 1.2 mm/yr to SLR.
- Mountain glacier retreat accelerated by 47% since 2000.
- Pine Island Glacier buttressing loss from ice shelf melt.
- Ocean heat uptake increased 91% since pre-industrial, driving expansion.
- Coriolis effect amplifies SLR in western ocean basins.
- Land subsidence from oil/gas extraction adds 25% to relative SLR in Gulf.
- Warming-induced ice sheet dynamical instability multiplies SLR 2-5x.
- Reservoir impoundment slowed SLR by 0.8 mm since 1960.
- Methane hydrate destabilization potential minor <0.5% SLR.
- Sediment compaction in deltas causes 1-10 mm/yr subsidence.
- Basal ice shelf melting from Circumpolar Deep Water intrusion.
- Urbanization-induced subsidence 2-15 mm/yr in coastal cities.
- Steric SLR from salinity changes <10% of total.
- Global glacier mass balance -390 Gt/yr 2012-2019.
- Greenland surface melt 464 Gt/yr average 2010-2019.
- Antarctic surface mass balance +105 Gt/yr offset by discharge.
- Western Antarctic ice sheet vulnerable to marine ice sheet instability.
- Global land ice loss 387 Gt/yr 2015-2019.
- Ocean acidification indirectly affects by altering ecosystems but minor direct SLR.
Causes and Contributing Factors Interpretation
If I had to summarize, I'd say our oceans are rising like a bad stock market graph, driven by a feverish cocktail of expanding warm water and retreating ice, with humanity actively adding its own reckless investments of groundwater pumping and land subsidence to the portfolio.
Current Measurements
- Global mean sea level rose 3.7 mm/yr from 2006-2015, the highest decadal rate on record.
- Satellite altimetry shows 4.3 mm/yr rise in 2020.
- NOAA tide gauges report U.S. average 3.8 mm/yr 2010-2020.
- Global steric rise 2.0 mm/yr 2015-2020 from Argo floats.
- Greenland ice melt contributed 0.8 mm/yr to sea level 2012-2020.
- Antarctic ice sheet loss 150 Gt/yr 2012-2017, equating to 0.4 mm/yr SLR.
- Western Pacific current rate 5.1 mm/yr.
- U.S. Gulf Coast 7-10 mm/yr due to subsidence and SLR.
- Miami tide gauge 8 mm/yr 2006-2015.
- Norfolk, VA 4.8 mm/yr 1975-2020.
- Shanghai current rate 3.9 mm/yr 1980-2020.
- Bangladesh coast 7.1 mm/yr 2000-2015.
- Venice Lagoon 3.4 mm/yr 1993-2018.
- Pacific Northwest 2.9 mm/yr 1990-2020.
- Arctic Ocean 3.9 mm/yr 2003-2018 from Envisat.
- Indian Ocean average 4.0 mm/yr 2010-2020.
- Mediterranean 3.7 mm/yr 1993-2019.
- Global ocean heat content rise implies 1.5 mm/yr thermal expansion 2015-2020.
- GRACE-FO shows land water storage contributing -0.2 mm/yr net 2018-2020.
- Southeast U.S. 5.2 mm/yr 2015-2020.
- Australia east coast 5.5 mm/yr 2010-2020.
- Japan current 4.2 mm/yr 2005-2020.
- Maldives 5.8 mm/yr 2000-2020.
- Louisiana coast 9.8 mm/yr 2008-2018.
Current Measurements Interpretation
The sea is no longer politely knocking at our door; it's now kicking it in with regional and accelerating urgency, from Louisiana's drastic retreat to the Maldives' creeping reality, all while the planet-wide fever of thermal expansion and ice melt keeps pouring more water into the bathtub.
Future Projections
- Global mean sea level to rise 0.28-0.55 m by 2100 under SSP1-2.6 (low emissions).
- Under SSP5-8.5 (high emissions), global SLR projected at 0.63-1.01 m by 2100.
- U.S. East Coast projected 0.3-0.8 m by 2050 relative to 2000.
- Global mean SLR 0.43 m (likely range 0.29–0.59 m) by 2100 for RCP4.5.
- Antarctic instability could add 0.5-2.3 m by 2300 under high emissions.
- Thermal expansion to contribute 30-50% of SLR by 2100.
- Greenland meltwater projected 0.09 m by 2100 under RCP8.5.
- Miami projected 0.5-1.2 m by 2060.
- Global SLR acceleration to 8-10 mm/yr by 2060 under medium emissions.
- Pacific islands 0.2-0.4 m by 2050.
- Europe coasts 0.3-0.9 m by 2100.
- Bangladesh Delta 0.3-0.6 m by 2050, displacing millions.
- Shanghai 0.4-0.8 m by 2100 with subsidence.
- Arctic summer sea ice loss amplifying 0.1-0.3 m extra SLR by 2100.
- Low-lying atolls risk submersion with 0.5 m SLR by 2100.
- U.S. West Coast 0.2-0.5 m by 2050.
- Global 5-10% exceedance probability SLR 2 m by 2100 under high emissions.
- 2.5 m SLR by 2300 possible with unmitigated warming.
- Venice projected 0.5-1.0 m by 2100.
- Global mean 1.0 m by 2300 under SSP2-4.5.
- Norfolk VA 0.6-1.5 m by 2100.
- New York City 0.4-0.8 m by 2050.
- Southeast Florida 1.0-2.0 m by 2100 high scenario.
- Louisiana 0.5-2.0 m by 2100 with subsidence.
- Global SLR 0.1 m/decade by 2100 under RCP2.6.
- U.S. East Coast relative SLR 20-30 cm/decade by 2050 in hotspots.
- Kiribati atolls 0.3-0.5 m by 2050.
Future Projections Interpretation
To comprehend these numbers is to realize that Mother Nature's ledger book is now open, and she is presenting a bill for our carbon party, payable not by us, but by our children, in drowned cities and lost homelands.
Historical Observations
- Global mean sea level rose by 1.7 mm per year from 1900 to 2018, totaling approximately 21-24 cm since 1880 with acceleration in recent decades.
- U.S. coastal sea levels have risen by 23 cm (9 inches) since 1880, faster than the global average due to land subsidence.
- Tide gauge records from 1901-2010 show a global sea level rise of 19 cm (7.5 inches).
- Satellite altimetry data from 1993-2018 indicates 3.7 mm/yr rise, contributing 5.4 cm total.
- European tide gauges record 1.5 mm/yr average rise from 1900-2000.
- Australian sea levels rose 8.7 cm from 1966-2009 at 1.6 mm/yr.
- Pacific islands tide data shows 1.8 mm/yr from 1993-2012.
- Gulf of Mexico historical rise of 2.4 mm/yr since 1900 due to subsidence.
- Baltic Sea levels rose 1.2 mm/yr from 1880-2010.
- Mediterranean Sea historical rise of 1.2 mm/yr 1900-2000.
- Arctic Ocean sea level rose 2.2 mm/yr 1992-2014 from GRACE data.
- Indian Ocean tide gauges show 1.9 mm/yr since 1960.
- Antarctic Peninsula sea level rise of 2.5 mm/yr 1992-2017.
- Global steric sea level rise from thermal expansion 1901-2010 was 0.4 mm/yr.
- U.S. East Coast historical rise 3.2 mm/yr 1927-2009.
- Japan tide records 2.8 cm/decade since 1950.
- China coast 3.3 mm/yr 1980-2010.
- Netherlands sea level rise 1.8 mm/yr 1890-2015.
- Florida historical rise 2.0 mm/yr since 1930.
- Hawaii islands 1.5 mm/yr 1905-2015.
- Global mean sea level acceleration detected at 0.08 mm/yr² from 1900-2000.
- 20th century total rise 17 cm with 60% from thermal expansion.
- Tide gauges worldwide show 1.8 ± 0.3 mm/yr 1901-2018.
- Post-1993 satellite rise 3.3 ± 0.4 mm/yr to 2020.
- Southeast Asia 3.6 mm/yr 1993-2017.
- North Atlantic historical 1.7 mm/yr 1960-2010.
- Southern Ocean 4 mm/yr 1993-2015.
- Black Sea 2.5 mm/yr 1920-2000.
- Caspian Sea level fluctuations show +1.2 mm/yr trend 1995-2015.
- Red Sea 1.8 mm/yr 1950-2000.
Historical Observations Interpretation
While these varied regional figures may seem like the ocean is just casually stretching its legs, the universal and accelerating trend is the planet politely but firmly moving the welcome mat right into our coastal cities.
Regional Variations
- U.S. East Coast experiences 3-4 times global average SLR due to AMOC slowdown.
- Gulf of Mexico relative SLR 2x global due to subsidence.
- Western Pacific Warm Pool sees 12 cm/decade rise.
- Southeast Asia coasts 5-10 mm/yr hotspots.
- Baltic Sea projected lower SLR 0.2 m by 2100 due to land uplift.
- Alaska southern coast subsidence offsets SLR.
- Mediterranean 20% above global average 3.7 mm/yr.
- Indian Ocean dipole influences 1-2 cm variations.
- U.S. West Coast lower than global due to uplift.
- Arctic regional amplification 2x global rate.
- South Atlantic steric rise dominant.
- Bangladesh Ganges Delta 16 mm/yr relative.
- Venice Lagoon subsidence + SLR 3-5 mm/yr.
- Australian Coral Sea 8 mm/yr.
- Florida Keys 9 mm/yr recent.
- Shanghai Yangtze Delta 20 mm/yr subsidence-driven.
- Maldives 5-7 mm/yr.
- Louisiana Mississippi Delta 10-25 mm/yr.
- Pacific Northwest 2-3 mm/yr.
- North Sea 2.5 mm/yr with surge variability.
- Japan Tokara Strait 6 mm/yr.
- Black Sea lower variability 2 mm/yr.
- Red Sea steric-dominated 2 mm/yr.
- Southern Ocean 4-5 mm/yr.
- Caspian Sea influenced by river inflow, -1 mm/yr trend.
- Southeast Florida 8-10 mm/yr.
- Norfolk-Cape Henry 5 mm/yr.
- New York Battery 4 mm/yr.
Regional Variations Interpretation
While our planet's oceans swell with the grim uniformity of a rising bath, our coastlines are like uneven floorboards, sinking in some places and tilting up in others, making the global crisis a wildly unfair local affair.
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