35-13 Glacial Retreat in Iceland, and New Metrics for Loss of Global Ice Mass and the Radial Momentum of Global Mean Sea Level (GMSL)

Session: Ice sheets, glaciers, and landscapes, oh my! (Posters)

Presenting Author:

Author:

Abstract:

Guðmundsson et al. (2020) documented glacial retreat in southeastern Iceland from the late 1800’s through 2018.  I extend this research to 2025 for the Fjallsjökull glacial tongue at the southeast margin of Vatnajökull ice sheet.  Its terminal lake has grown to cover an area ≥4.25 km².  Retreat of this and other glacial tongues accelerated over the last 20 years.  Radar/laser altimetry and gravimetric studies are documenting the mass lost from many glaciers, but it’s feasible to estimate global cryosphere melt by analyzing GMSL.  Sea-level rise has three components: (1)meltwaters flowing into the seas, (2)thermosteric expansion of warming upper oceanic layers, and (3)continental drying (net water loss from continents including permafrost decay).  Relative fractions of these vary somewhat yearly.  Glacial melt causes 44-60% of annual GMSL rise, which is used to calculate the volume range and global mass of ice lost.  Latent heat of fusion is then used to analyze the cumulative energy required to melt that global mass, multiplying the total by 334 joules/gram.  The derived energy range is astounding, ~2.1─2.8 × 10²⁰ joules, numbers so large they're best described in nuclear terms.  For 2024 the glacial melt energy was equivalent to ~2000-2700 Trinity nuclear tests, converting ALL their energy to ice melt.  That is also annually equivalent to >80-times the cumulative energy of all historic nuclear tests by all countries.   It’s no wonder that massive meltwater volumes are surging into the oceans.  Only the fact that Earth is a water planet has prevented more drastic warming.  The oceans have so far been absorbing great quantities of CO₂ and heat.  Earth’s ice sheets are essentially acting as “sacrificial anodes” in absorbing massive heat energy.  I also introduce the astrophysical parameter of radial momentum of sea-level rise, applicable for equipotential ocean surfaces.  Although the rate of GMSL rise doubled in a 20-year period, its globally-averaged radial momentum rose by a factor of five.  It is concerning that two step increases in GMSL rise occurred in that short time.  Associated impulses are calculated.  What will happen to this and future generations when even more of Earth’s reflective ice is gone?   Global warming and GMSL will continue to rise with increasing levels of atmospheric CO₂ and other potent greenhouse gases (CH₄, N₂O, and SF₆).

Geological Society of America Abstracts with Programs. Vol. 58, No. 2, 2026

© Copyright 2026 The Geological Society of America (GSA), all rights reserved.