Recurring dynamically-induced thinning during 1985-2010 on Upernavik Isstrøm, West Greenland

This is the publisher's version, also available electronically from "http://onlinelibrary.wiley.com".1] Many glaciers along the southeast and northwest coasts of Greenland have accelerated, increasing the ice sheet's contribution to global sea-level rise. In this article, we map elevation changes on Upernavik Isstrøm (UI), West Greenland, during 2003to 2009 using high-resolution ice, cloud and land elevation satellite laser altimeter data supplemented with altimeter surveys from NASA's Airborne Topographic Mapper during 2002 to 2010. To assess thinning prior to 2002, we analyze aerial photographs from 1985. We document at least two distinct periods of dynamically induced ice loss during 1985 to 2010 characterized by a rapid retreat of the calving front, increased ice speed, and lowering of the ice surface. The first period occurred before 1991, whereas the latter occurred during 2005 to 2009. Analyses of air and sea-surface temperature suggest a combination of relatively warm air and ocean water as a potential trigger for the dynamically induced ice loss. We estimate a total catchment-wide ice-mass loss of UI caused by the two events of 72.3 ± 15.8 Gt during 1985 to 2010, whereas the total melt-induced ice-mass loss during this same period is 19.8 ± 2.8 Gt. Thus, 79% of the total ice-mass loss of the UI catchment was caused by ice dynamics, indicating the importance of including dynamically induced ice loss in the total mass change budget of the Greenland ice sheet

Mass balance of the Greenland Ice Sheet from 1992 to 2018

In recent decades, the Greenland Ice Sheet has been a major contributor to global sea-level rise1,2, and it is expected to be so in the future3. Although increases in glacier flow4–6 and surface melting7–9 have been driven by oceanic10–12 and atmospheric13,14 warming, the degree and trajectory of today’s imbalance remain uncertain. Here we compare and combine 26 individual satellite measurements of changes in the ice sheet’s volume, flow and gravitational potential to produce a reconciled estimate of its mass balance. Although the ice sheet was close to a state of balance in the 1990s, annual losses have risen since then, peaking at 335 ± 62 billion tonnes per year in 2011. In all, Greenland lost 3,800 ± 339 billion tonnes of ice between 1992 and 2018, causing the mean sea level to rise by 10.6 ± 0.9 millimetres. Using three regional climate models, we show that reduced surface mass balance has driven 1,971 ± 555 billion tonnes (52%) of the ice loss owing to increased meltwater runoff. The remaining 1,827 ± 538 billion tonnes (48%) of ice loss was due to increased glacier discharge, which rose from 41 ± 37 billion tonnes per year in the 1990s to 87 ± 25 billion tonnes per year since then. Between 2013 and 2017, the total rate of ice loss slowed to 217 ± 32 billion tonnes per year, on average, as atmospheric circulation favoured cooler conditions15 and as ocean temperatures fell at the terminus of Jakobshavn Isbræ16. Cumulative ice losses from Greenland as a whole have been close to the IPCC’s predicted rates for their high-end climate warming scenario17, which forecast an additional 50 to 120 millimetres of global sea-level rise by 2100 when compared to their central estimate

Recurring dynamically induced thinning during 1985 to 2010 on Upernavik Isstrom, West Greenland

Many glaciers along the southeast and northwest coasts of Greenland have accelerated, increasing the ice sheet's contribution to global sea-level rise. In this article, we map elevation changes on Upernavik Isstrom (UI), West Greenland, during 2003 to 2009 using high-resolution ice, cloud and land elevation satellite laser altimeter data supplemented with altimeter surveys from NASA's Airborne Topographic Mapper during 2002 to 2010. To assess thinning prior to 2002, we analyze aerial photographs from 1985. We document at least two distinct periods of dynamically induced ice loss during 1985 to 2010 characterized by a rapid retreat of the calving front, increased ice speed, and lowering of the ice surface. The first period occurred before 1991, whereas the latter occurred during 2005 to 2009. Analyses of air and sea-surface temperature suggest a combination of relatively warm air and ocean water as a potential trigger for the dynamically induced ice loss. We estimate a total catchment-wide ice-mass loss of UI caused by the two events of 72.3 +/- 15.8 Gt during 1985 to 2010, whereas the total melt-induced ice-mass loss during this same period is 19.8 +/- 2.8 Gt. Thus, 79% of the total ice-mass loss of the UI catchment was caused by ice dynamics, indicating the importance of including dynamically induced ice loss in the total mass change budget of the Greenland ice sheet

Recurring dynamically induced thinning during 1985 to 2010 on Upernavik Isstrøm, West Greenland

Many glaciers along the southeast and northwest coasts of Greenland have accelerated, increasing the ice sheet's contribution to global sea-level rise. In this article, we map elevation changes on Upernavik Isstrom (UI), West Greenland, during 2003 to 2009 using high-resolution ice, cloud and land elevation satellite laser altimeter data supplemented with altimeter surveys from NASA's Airborne Topographic Mapper during 2002 to 2010. To assess thinning prior to 2002, we analyze aerial photographs from 1985. We document at least two distinct periods of dynamically induced ice loss during 1985 to 2010 characterized by a rapid retreat of the calving front, increased ice speed, and lowering of the ice surface. The first period occurred before 1991, whereas the latter occurred during 2005 to 2009. Analyses of air and sea-surface temperature suggest a combination of relatively warm air and ocean water as a potential trigger for the dynamically induced ice loss. We estimate a total catchment-wide ice-mass loss of UI caused by the two events of 72.3 +/- 15.8 Gt during 1985 to 2010, whereas the total melt-induced ice-mass loss during this same period is 19.8 +/- 2.8 Gt. Thus, 79% of the total ice-mass loss of the UI catchment was caused by ice dynamics, indicating the importance of including dynamically induced ice loss in the total mass change budget of the Greenland ice sheet

Mass balance of the Antarctic Ice Sheet from 1992 to 2017

The Antarctic Ice Sheet is an important indicator of climate change and driver of sea-level rise. Here we combine satellite observations of its changing volume, flow and gravitational attraction with modelling of its surface mass balance to show that it lost 2,720 ± 1,390 billion tonnes of ice between 1992 and 2017, which corresponds to an increase in mean sea level of 7.6 ± 3.9 millimetres (errors are one standard deviation). Over this period, ocean-driven melting has caused rates of ice loss from West Antarctica to increase from 53 ± 29 billion to 159 ± 26 billion tonnes per year; ice-shelf collapse has increased the rate of ice loss from the Antarctic Peninsula from 7 ± 13 billion to 33 ± 16 billion tonnes per year. We find large variations in and among model estimates of surface mass balance and glacial isostatic adjustment for East Antarctica, with its average rate of mass gain over the period 1992–2017 (5 ± 46 billion tonnes per year) being the least certain

Mass balance of the Antarctic Ice Sheet from 1992 to 2017

The Antarctic Ice Sheet is an important indicator of climate change and driver of sea-level rise. Here we combine satellite observations of its changing volume, flow and gravitational attraction with modelling of its surface mass balance to show that it lost 2,720 ± 1,390 billion tonnes of ice between 1992 and 2017, which corresponds to an increase in mean sea level of 7.6 ± 3.9 millimetres (errors are one standard deviation). Over this period, ocean-driven melting has caused rates of ice loss from West Antarctica to increase from 53 ± 29 billion to 159 ± 26 billion tonnes per year; ice-shelf collapse has increased the rate of ice loss from the Antarctic Peninsula from 7 ± 13 billion to 33 ± 16 billion tonnes per year. We find large variations in and among model estimates of surface mass balance and glacial isostatic adjustment for East Antarctica, with its average rate of mass gain over the period 1992–2017 (5 ± 46 billion tonnes per year) being the least certain

Mass balance of the Greenland Ice Sheet from 1992 to 2018

The Greenland Ice Sheet has been a major contributor to global sea-level rise in recent decades1,2, and it is expected to continue to be so3. Although increases in glacier flow4,5,6 and surface melting7,8,9 have been driven by oceanic10,11,12 and atmospheric13,14 warming, the magnitude and trajectory of the ice sheet’s mass imbalance remain uncertain. Here we compare and combine 26 individual satellite measurements of changes in the ice sheet’s volume, flow and gravitational potential to produce a reconciled estimate of its mass balance. The ice sheet was close to a state of balance in the 1990s, but annual losses have risen since then, peaking at 345 ± 66 billion tonnes per year in 2011. In all, Greenland lost 3,902 ± 342 billion tonnes of ice between 1992 and 2018, causing the mean sea level to rise by 10.8 ± 0.9 millimetres. Using three regional climate models, we show that the reduced surface mass balance has driven 1,964 ± 565 billion tonnes (50.3 per cent) of the ice loss owing to increased meltwater runoff. The remaining 1,938 ± 541 billion tonnes (49.7 per cent) of ice loss was due to increased glacier dynamical imbalance, which rose from 46 ± 37 billion tonnes per year in the 1990s to 87 ± 25 billion tonnes per year since then. The total rate of ice loss slowed to 222 ± 30 billion tonnes per year between 2013 and 2017, on average, as atmospheric circulation favoured cooler conditions15 and ocean temperatures fell at the terminus of Jakobshavn Isbræ16. Cumulative ice losses from Greenland as a whole have been close to the rates predicted by the Intergovernmental Panel on Climate Change for their high-end climate warming scenario17, which forecast an additional 70 to 130 millimetres of global sea-level rise by 2100 compared with their central estimate

Mass balance of the Greenland Ice Sheet from 1992 to 2018

In recent decades, the Greenland Ice Sheet has been a major contributor to global sea-level rise1,2, and it is expected to be so in the future3. Although increases in glacier flow4–6 and surface melting7–9 have been driven by oceanic10–12 and atmospheric13,14 warming, the degree and trajectory of today’s imbalance remain uncertain. Here we compare and combine 26 individual satellite measurements of changes in the ice sheet’s volume, flow and gravitational potential to produce a reconciled estimate of its mass balance. Although the ice sheet was close to a state of balance in the 1990s, annual losses have risen since then, peaking at 335 ± 62 billion tonnes per year in 2011. In all, Greenland lost 3,800 ± 339 billion tonnes of ice between 1992 and 2018, causing the mean sea level to rise by 10.6 ± 0.9 millimetres. Using three regional climate models, we show that reduced surface mass balance has driven 1,971 ± 555 billion tonnes (52 of the ice loss owing to increased meltwater runoff. The remaining 1,827 ± 538 billion tonnes (48 of ice loss was due to increased glacier discharge, which rose from 41 ± 37 billion tonnes per year in the 1990s to 87 ± 25 billion tonnes per year since then. Between 2013 and 2017, the total rate of ice loss slowed to 217 ± 32 billion tonnes per year, on average, as atmospheric circulation favoured cooler conditions15 and as ocean temperatures fell at the terminus of Jakobshavn Isbræ16. Cumulative ice losses from Greenland as a whole have been close to the IPCC’s predicted rates for their high-end climate warming scenario17, which forecast an additional 50 to 120 millimetres of global sea-level rise by 2100 when compared to their central estimate