Sea & Ice
Global mean sea level has risen substantially since satellite altimetry began in 1993, driven by thermal expansion and accelerating melt from glaciers and ice sheets. Alongside that long-term rise, this page tracks monthly Arctic and Antarctic sea ice extent, global anomalies against the 1991-2020 baseline, and annual trends in sea ice cover and ocean surface temperature. A suite of correlation charts then shows how rising CO₂, warming oceans, and shrinking ice reinforce each other to explain the acceleration in global mean sea level.
Current Readings
Monthly Indicators
Global Sea Ice Extent
Arctic + Antarctic Combined · Absolute Extent
Last 60 months. Thick line shows 12-month rolling average – Arctic loss exceeds Antarctic variability.
Source: NSIDC via global-warming.org
Ocean Temperature
Global Ocean · Absolute Temperature
Ocean covers ~71% of Earth's surface, so its temperature moves the global average more than any other single factor.
Source: NOAA Climate at a Glance
Arctic Sea Ice - 1978–2026
One line per year since satellite records began. 2026 is highlighted; the lowest Aug on record (2012) is picked out in red.
Record low for Aug: Aug 2012 at 4.72 Mkm². Source: NSIDC Sea Ice Index v4 · monthly averages · 1991–2020 climatology.
Antarctic Sea Ice - 1978–2026
One line per year since satellite records began. 2026 is highlighted; the lowest Aug on record (2023) is picked out in red.
Record low for Aug: Aug 2023 at 15.57 Mkm². Source: NSIDC Sea Ice Index v4 · monthly averages · 1991–2020 climatology.
Ice Extent Time-Lapse
Polar Ice Extent
Corresponding Temperatures & Sea Level
Source: NSIDC Sea Ice Index v4.0 – September monthly polygon shapefiles · NASA GISS · NOAA
How It All Connects
Warming Drives Rising Seas
Temperature anomaly (left axis) vs sea level change in mm (right axis)
Warmer air melts ice and warmer water expands – both pushing sea levels higher. Sources: NASA GISS / NOAA (temperature) · NOAA Satellite Altimetry (sea level).
Melting Ice, Rising Seas
Global sea ice extent in M km² (left axis) vs sea level change in mm (right axis)
Declining sea ice signals broader ice loss – and accelerates warming through the ice-albedo feedback loop. Sources: NSIDC / NOAA (ice) · NOAA Satellite Altimetry (sea level).
Warming Destroys Ice
Temperature anomaly (left axis) vs global sea ice extent in M km² (right axis)
Higher temperatures melt ice, exposing dark ocean that absorbs more heat – a self-reinforcing cycle. Sources: NASA GISS / NOAA (temperature) · NSIDC (ice).
Warmer Oceans, Higher Seas
Ocean surface anomaly (left axis) vs sea level change in mm (right axis)
Oceans absorb over 90% of excess heat. As water warms it expands – the single largest contributor to sea level rise. Sources: NOAA (ocean) · NOAA Satellite Altimetry (sea level).
Rising Carbon, Rising Seas
CO₂ concentration (left axis) vs sea level change in mm (right axis)
CO₂ traps heat, which warms oceans and melts ice – both pushing sea levels higher in an accelerating trend. Sources: NOAA GML (CO₂) · NOAA Satellite Altimetry (sea level).
Sea Level and Sea Ice
Global Mean Sea Level
Annual average sea level change (mm) – satellite era
Satellite altimetry has tracked sea level since 1993, revealing an accelerating rise driven by thermal expansion and ice melt. Source: NOAA Laboratory for Satellite Altimetry (1993–present).
Global Sea Ice Extent
Annual average sea ice extent (million km²)
Global sea ice (Arctic + Antarctic combined) reflects sunlight back into space. As it melts, darker ocean absorbs more heat – accelerating warming in a feedback loop. Source: NSIDC / NOAA via global-warming.org.
Explore
Explore Climate Data
FAQs
FAQs
What does the sea levels and ice page show?
Live indicators of how Earth's ice and oceans are responding to warming: global mean sea level from satellite altimetry, Arctic and Antarctic sea-ice extent, global ocean surface temperature, and Greenland and Antarctic ice sheet mass change. Current values and long-term trends are shown in the live panels above.
What is the difference between sea ice and land ice?
Sea ice is frozen sea water floating on the ocean (Arctic and Antarctic). Its extent changes each year between summer and winter, and shrinking sea ice does not directly raise sea level because it is already displacing water. Land ice (the Greenland and Antarctic ice sheets, plus mountain glaciers) sits on land - when it melts it adds new water to the ocean and is the main driver of long-term sea level rise alongside thermal expansion.
Where does the data come from?
Sea level: NASA satellite altimetry (TOPEX/Poseidon, Jason and Sentinel missions) and the tide-gauge network. Sea ice: National Snow and Ice Data Center (NSIDC), based on NOAA passive microwave satellite observations. Ocean temperature: NOAA Climate at a Glance global ocean surface record. Ice sheet mass: GRACE and GRACE-FO satellite missions, archived by NASA JPL.
What baseline is used for the anomalies?
Sea ice anomalies use the 1981-2010 reference period (NSIDC standard). Sea level anomalies use a 1993-2008 satellite-altimetry reference. Ice-mass change is reported as cumulative gigatonnes lost since the start of each satellite record. Ocean temperature is shown as the actual sea surface temperature rather than an anomaly. The baseline is labelled on each chart.
How often is this page updated?
Sea-ice extent feeds refresh daily during the melt and freeze seasons. Sea level and ice-mass data refresh monthly as the source agencies release new processed values, typically with a one- to two-month lag.