Query: Wu et al (2010) use a new method to calculate ice sheet mass balance.

Relevant passages:
Retreat of glaciers since 1850 <=SEP=> The retreat of glaciers since 1850 affects the availability of fresh water for irrigation and domestic use , mountain recreation , animals and plants that depend on glacier-melt , and , in the longer term , the level of the oceans . Studied by glaciologists , the temporal coincidence of glacier retreat with the measured increase of atmospheric greenhouse gases is often cited as an evidentiary underpinning of global warming . Mid-latitude mountain ranges such as the Himalayas , Alps , Rocky Mountains , Cascade Range , and the southern Andes , as well as isolated tropical summits such as Mount Kilimanjaro in Africa , are showing some of the largest proportionate glacial losses .   Glacier mass balance is the key determinant of the health of a glacier . If the amount of frozen precipitation in the accumulation zone exceeds the quantity of glacial ice lost due to melting or in the ablation zone a glacier will advance ; if the accumulation is less than the ablation , the glacier will retreat . Glaciers in retreat will have negative mass balances , and if they do not find an equilibrium between accumulation and ablation , will eventually disappear .   The Little Ice Age was a period from about 1550 to 1850 when the world experienced relatively cooler temperatures compared to the present . Subsequently , until about 1940 , glaciers around the world retreated as the climate warmed substantially . Glacial retreat slowed and even reversed temporarily , in many cases , between 1950 and 1980 as global temperatures cooled slightly . Since 1980 , a significant global warming has led to glacier retreat becoming increasingly rapid and ubiquitous , so much so that some glaciers have disappeared altogether , and the existences of many of the remaining glaciers are threatened . In locations such as the Andes of South America and Himalayas in Asia , the demise of glaciers in these regions has the potential to affect water supplies in those areas .   The retreat of mountain glaciers , notably in western North America , Asia , the Alps and tropical and subtropical regions of South America , Africa and Indonesia , provide evidence for the rise in global temperatures since the late 19th century . The acceleration of the rate of retreat since 1995 of key outlet glaciers of the Greenland and West Antarctic ice sheets may foreshadow a rise in sea level , which would affect coastal regions .

Post-glacial rebound <=SEP=> Post-glacial rebound ( also called either isostatic rebound or crustal rebound ) is the rise of land masses that were depressed by the huge weight of ice sheets during the last glacial period , through a process known as isostatic depression . Post-glacial rebound and isostatic depression are different parts of a process known as either glacial isostasy , glacial isostatic adjustment , or glacioisostasy . Glacioisostasy is the solid Earth deformation associated with changes in ice mass distribution . The most obvious and direct effects of post-glacial rebound are readily apparent in parts of Northern Eurasia , Northern America , Patagonia , and Antarctica . However , through processes known as ocean siphoning and continental levering , the effects of post-glacial rebound on sea level are felt globally far from the locations of current and former ice sheets .

Sea level rise <=SEP=> A sea level rise is an increase in the volume of water in the world 's oceans , resulting in an increase in global mean sea level . Sea level rise is usually attributed to global climate change by thermal expansion of the water in the oceans and by melting of Ice sheets and glaciers on land . Melting of floating ice shelves or icebergs at sea raises sea levels only slightly .   Sea level rise at specific locations may be more or less than the global average . Local factors might include tectonic effects , subsidence of the land , tides , currents , storms , etc. .  Sea level rise is expected to continue for centuries . Because of the slow inertia , long response time for parts of the climate system , it has been estimated that we are already committed to a sea-level rise of approximately 2.3 m for each degree Celsius of temperature rise within the next 2,000 years . IPCC Summary for Policymakers , AR5 , 2014 , indicated that the global mean sea level rise will continue during the 21st century , very likely at a faster rate than observed from 1971 to 2010 . Projected rates and amounts vary . A January 2017 NOAA report suggests a range of GMSL rise of 0.3 -- 2.5 m possible during the 21st century .   Sea level rises can considerably influence human populations in coastal and island regions and natural environments like marine ecosystems .

Geoid <=SEP=> The geoid is the shape that the surface of the oceans would take under the influence of Earth 's gravity and rotation alone , in the absence of other influences such as winds and tides . This surface is extended through the continents ( such as with very narrow hypothetical canals ) . All points on a geoid surface have the same gravitational potential energy ( the sum of gravitational potential energy and centrifugal potential energy ) . The geoid can be defined at any value of gravitational potential such as within the Earth 's crust or far out in space , not just at sea level . The force of gravity acts everywhere perpendicular to the geoid , meaning that plumb lines point perpendicular and water levels parallel to the geoid if only gravity and rotational acceleration were at work .   Specifically , the geoid is the equipotential surface that would coincide with the mean ocean surface of Earth if the oceans and atmosphere were in equilibrium , at rest relative to the rotating Earth , and extended through the continents ( such as with very narrow canals ) . According to Gauss , who first described it , it is the `` mathematical figure of Earth '' , a smooth but highly irregular surface whose shape results from the uneven distribution of mass within and on the surface of Earth . It does not correspond to the actual surface of Earth 's crust , but to a surface which can only be known through extensive gravitational measurements and calculations . Despite being an important concept for almost two hundred years in the history of geodesy and geophysics , it has only been defined to high precision since advances in satellite geodesy in the late 20th century . It is often described as the true physical figure of the Earth , in contrast to the idealized geometrical figure of a reference ellipsoid .   The surface of the geoid is higher than the reference ellipsoid wherever there is a positive gravity anomaly ( mass excess ) and lower than the reference ellipsoid wherever there is a negative gravity anomaly ( mass deficit ) .