Welcome to DU!
The truly grassroots left-of-center political community where regular people, not algorithms, drive the discussions and set the standards.
Join the community:
Create a free account
Support DU (and get rid of ads!):
Become a Star Member
Latest Breaking News
General Discussion
The DU Lounge
All Forums
Issue Forums
Culture Forums
Alliance Forums
Region Forums
Support Forums
Help & Search
History, mass loss, structure, and dynamic behavior of the Antarctic Ice Sheet
The paper I'll discuss in this post is this one, a review article: History, mass loss, structure, and dynamic behavior of the Antarctic Ice Sheet (Robin E. Bell1, Helene Seroussi, Science, Vol. 367, Issue 6484, pp. 1321-1325)
First, a diversion appropriate to the times:
Une manière commode de faire la connaissance d’une ville est de chercher comment on y travaille, comment on y aime et comment on y meurt. Dans notre petite ville, est-ce l’effet du climat, tout cela se fait ensemble, du même air frénétique et absent. C’est-à-dire qu’on s’y ennuie et qu’on s’y applique à prendre des habitudes. Nos concitoyens travaillent beaucoup, mais toujours pour s’enrichir. Ils s’intéressent surtout au commerce et ils s’occupent d’abord, selon leur expression, de faire des affaires. Naturellement ils ont du goût aussi pour les joies simples, ils aiment les femmes, le cinéma et les bains de mer. Mais, très raisonnablement, ils réservent ces plaisirs pour le samedi soir et le dimanche, essayant, les autres jours de la semaine, de gagner beaucoup d’argent. Le soir, lorsqu’ils quittent leurs bureaux, ils se réunissent à heure fixe dans les cafés, ils se promènent sur le même boulevard ou bien ils se mettent à leurs balcons. Les désirs des plus jeunes sont violents et brefs, tandis que les vices des plus âgés ne dépassent pas les associations de boulomanes, les banquets des amicales et les cercles où l’on joue gros jeu sur le hasard des cartes.
- Albert Camus, "La Peste" (The Plague).
"An easy way to get to know a town is to look for how one works there, how one loves there, how one dies there. In our small town, these are all done together, an effect of the climate, in an atmosphere that is frenetic and absent..."
(Perhaps our planet is more a smaller town and less a giant world than we know.)
"...One is bored there and one starts to take on habits. Our citizens work a lot, but always to enrich themselves. Above all, their primary interest, as seen in their expressions, is in commerce and in doing business..."
(Well yeah, in our small world...)
"...Naturally, they have a taste for simple joys; they love women, films and swimming in the sea. But quite reasonably they reserve these pleasures for Saturday night, and Sunday; the other days of the week they work to get lots of money. In the evenings, when they leave their offices, they gather at a regular time in cafes, they walk the same streets, or happily set themselves on their balconies. The desires of the young are violent and brief, while those vices of the older ones go little beyond shooting clubs,
friendly banquets, or gambling in high stakes card games."
(Shooting clubs...gambling...high stakes... in our small world.)
Under the circumstances, The Plague has a familiar ring, does it not? In that book, the rats crawl out first, and die, and people wonder to themselves why the authorities don't do something about the rats, while the authorities seek to cover the whole matter up, declaring it unimportant.
The signature of the temporary decline, world wide, in the use of cars will show up in the atmosphere, but the effect will most likely be temporary. At the end of Camus's simultaneously allegorical and observational book, the world goes back to normal when the plague is over, which I assume is going back to being "good for business," but one wonders whether normal is itself a plague.
"Business as usual," as they say time and time again in the IPCC climate reports, report after report after report, a metronome of disaster.
The fact is that we are very much involved in high stakes gambling, with the entire planetary atmosphere, a point made in the paper referenced at the outset. It's a review article discussing papers discussing the Antarctic ice sheets.
From the introduction to the paper:
Two hundred years ago, an expedition led by Fabian Gottlieb von Bellingshausen and Mikhail Lazarev discovered mainland Antarctica, the most remote and inhospitable continent. Today, Antarctic is an ice-covered continent where change is emblematic of the impacts humans have on the global climate. Hidden beneath the ice sheets are a rich diversity of terrains and hydrologic systems of mountains, lakes, and dynamic subglacial water networks (1, 2). The changes we are now witnessing (3–5) are concentrated in the low-elevation regions as well as the Antarctic Peninsula, the furthest north part of the continent. Evidence of change comes from satellite measurements of ice mass, velocity (4), and elevations (3). Large floating ice shelves have disintegrated (6), and the location where the ice goes afloat is moving inland (7). Future vulnerabilities arise from interactions with the warming ocean, melting of the ice surface, and the disappearance of the ice shelves. Looking forward, coastal communities around the globe need to know how much sea level will rise, and how much Antarctica will change is one of the greatest unknowns. Both improved models and observations are essential to improve the scientific community’s response to the question of how much sea level will rise over the coming decades and centuries...
...Over the past 100 million years or more, Antarctica shifted from a green tree-covered continent (8) to a continent encased in ice as it became tectonically isolated while the global climate cooled (9). The tectonic isolation of the continent began more than 200 million years ago, when it was at the center of the Gondwana supercontinent with a climate similar to that of modern New Zealand. The supercontinent breakup occurred slowly, first with Africa (170 million years ago), then India (145 million years ago), and last, Australia (90 million years ago), shifting away from what today is Antarctica as the Southern Ocean began to form. The final step occurred 34 million years ago as the Drake Passage (10), between South America and the Antarctic Peninsula, and the Tasmanian Gateway, south of Australia, opened. The global oceans thereby were effectively linked. The Antarctic Circumpolar Current, the strongest ocean current on the planet, began to circulate around the continent, and Antarctica was isolated...
...Over the past 100 million years or more, Antarctica shifted from a green tree-covered continent (8) to a continent encased in ice as it became tectonically isolated while the global climate cooled (9). The tectonic isolation of the continent began more than 200 million years ago, when it was at the center of the Gondwana supercontinent with a climate similar to that of modern New Zealand. The supercontinent breakup occurred slowly, first with Africa (170 million years ago), then India (145 million years ago), and last, Australia (90 million years ago), shifting away from what today is Antarctica as the Southern Ocean began to form. The final step occurred 34 million years ago as the Drake Passage (10), between South America and the Antarctic Peninsula, and the Tasmanian Gateway, south of Australia, opened. The global oceans thereby were effectively linked. The Antarctic Circumpolar Current, the strongest ocean current on the planet, began to circulate around the continent, and Antarctica was isolated...
A picture:
The caption:
Fig. 1 Development of Antarctic ice together with global CO2 and ocean surface temperature.
(Top) Global CO2. (Bottom) Ocean surface temperature. Onset of East Antarctic ice occurred 34 million years ago as ocean temperatures and CO2 dropped (53, 54). Development of West Antarctica marine ice sheet at 14 million years ago began with the next major drop in global temperature. Two extreme modes of Antarctic ice have occurred since the onset of glaciation in West Antarctica was first covered with ice: ice extending all the way to the continental shelf during cold periods, such as the Last Glacial Maximum 25,000 years ago, and retreat beyond the present extent, with partial collapse of marine portions of Antarctica during some past warm periods (16).
(Top) Global CO2. (Bottom) Ocean surface temperature. Onset of East Antarctic ice occurred 34 million years ago as ocean temperatures and CO2 dropped (53, 54). Development of West Antarctica marine ice sheet at 14 million years ago began with the next major drop in global temperature. Two extreme modes of Antarctic ice have occurred since the onset of glaciation in West Antarctica was first covered with ice: ice extending all the way to the continental shelf during cold periods, such as the Last Glacial Maximum 25,000 years ago, and retreat beyond the present extent, with partial collapse of marine portions of Antarctica during some past warm periods (16).
Later on the authors say:
..There are three major components of an ice sheet system: grounded slow-moving ice, fast-flowing ice streams or outlet glaciers and floating ice shelves (Fig. 2). The grounded slow-moving ice contains the vast majority of the ice (Fig. 2) and is in contact with the underlying rocks. This ice moves very slowly by means of internal deformation at rates on the order of 1 m/year (4) and is up to 4775 m thick (17). The fast flowing ice streams and outlet glaciers are conveyor belts that move the ice toward the ocean, are up to 100 km across, and slide rapidly over the underlying topography at rates of up to 4 km/year (4). Although the surface of glaciers and ice streams are fractured by crevasses, water and till (water-saturated sediments) at their base reduce the basal friction and enable their fast flow (18). The grounded Antarctic holds enough ice to raise sea level rise by 58 m (19)...
...East Antarctica is the largest ice sheet on the planet, with thicknesses greater than 4600 m (19). In some areas, the bedrock underlying the ice is above sea level, but extensive portions are below sea level. The top of the ice sheet, Dome A, is at 4200 m over the Gamburtsev Mountains (Figs. 2 and 3), whereas the deepest point, carved by erosion during successive advance and retreat of an ice stream, is located more than 3500 m below sea level under Denman Glacier (19). Beneath the thick ice are large lakes—Vostok (21), 90°E, and Sovietskaya (22)—with up to 1000 m of water (Figs. 2 and 3). These systems have been sealed from the atmosphere for ~34 million years since the onset of Antarctic glaciation. The iconic ice core records of temperature and CO2 come from the deep cores at Vostok [400,000 years (14)], Dome C [800,000 years (23)], and Dome F [720,000 years (24)].
...East Antarctica is the largest ice sheet on the planet, with thicknesses greater than 4600 m (19). In some areas, the bedrock underlying the ice is above sea level, but extensive portions are below sea level. The top of the ice sheet, Dome A, is at 4200 m over the Gamburtsev Mountains (Figs. 2 and 3), whereas the deepest point, carved by erosion during successive advance and retreat of an ice stream, is located more than 3500 m below sea level under Denman Glacier (19). Beneath the thick ice are large lakes—Vostok (21), 90°E, and Sovietskaya (22)—with up to 1000 m of water (Figs. 2 and 3). These systems have been sealed from the atmosphere for ~34 million years since the onset of Antarctic glaciation. The iconic ice core records of temperature and CO2 come from the deep cores at Vostok [400,000 years (14)], Dome C [800,000 years (23)], and Dome F [720,000 years (24)].
The bold is mine.
Figure 2:
The caption:
Fig. 2 Structure of the Antarctic Ice Sheet.
(A) East and (B) West Antarctic cross section profiles. (C and D) Location of profiles are shown on (C) surface velocity and (D) subglacial bed topography (17). West Antarctica maximum elevation of 2200 m is nested in the deep Byrd Subglacial Basin, with depths 2500 m below sea level. The East Antarctic Ice Sheet nucleated on the high Gamburtsev Mountains, with the maximum elevation at Dome A reaching 4200 m, covers deep subglacial lakes such as Lake Vostok and has portions that are marine. The portions of the ice sheets with bedrock elevation below sea level are shaded blue.
(A) East and (B) West Antarctic cross section profiles. (C and D) Location of profiles are shown on (C) surface velocity and (D) subglacial bed topography (17). West Antarctica maximum elevation of 2200 m is nested in the deep Byrd Subglacial Basin, with depths 2500 m below sea level. The East Antarctic Ice Sheet nucleated on the high Gamburtsev Mountains, with the maximum elevation at Dome A reaching 4200 m, covers deep subglacial lakes such as Lake Vostok and has portions that are marine. The portions of the ice sheets with bedrock elevation below sea level are shaded blue.
Figure 3:
The caption:
Fig. 3 Radar cross sections over the Gamburtsev Mountains, Lake Vostok, and West Antarctica.
(Top) Gamburtsev Mountains. (Middle) Lake Vostok. (Bottom) West Antarctica. Location of profiles are approximately along the profiles shown in Fig. 2. Radar layers indicate ice stratigraphy. Ice is deformed as it flows over mountains, but layers remain flat as the ice flows over Lake Vostok, the location of the first deep ice core. The color shading highlights the age of the ice sheets. Basal freeze-on is observed in the Gamburtsev Mountain profile
(Top) Gamburtsev Mountains. (Middle) Lake Vostok. (Bottom) West Antarctica. Location of profiles are approximately along the profiles shown in Fig. 2. Radar layers indicate ice stratigraphy. Ice is deformed as it flows over mountains, but layers remain flat as the ice flows over Lake Vostok, the location of the first deep ice core. The color shading highlights the age of the ice sheets. Basal freeze-on is observed in the Gamburtsev Mountain profile
...Evidence for change
The evidence for recent changes of Antarctic ice is quantified by three independent measurements primarily derived from satellite and airborne systems: decreasing mass from gravity, dropping surface elevation, and increased surface velocities (Fig. 4).
Changes in ice mass are measured from space with the pair of GRACE (Gravity Recovery and Climate Experiment) satellites, which capture changes in the gravity field experienced by each spacecraft as they orbit Earth together (28). The original pair of satellites resolved monthly changes in Antarctic ice mass from 2002 to 2017 (Fig. 4), and a new pair of satellites, GRACE Follow-On, was launched in 2018 to continue the record of the Earth and Antarctic mass changes. The observed changes must be corrected for modeled changes in motion of the solid Earth to include the crust and the mantle rebound owing to past and ongoing ice mass changes. Determining both the Earth structure and the history of past ice sheet changes are the greatest challenges in separating the observed mass changes into the solid Earth component and the changes in ice mass. The GRACE data (28) show mass loss in West Antarctica, focused in the Amundsen and Bellingshausen Sea sectors, and mass gain in some regions of East Antarctica and along Kamb Ice Stream (Fig. 4).
Lowering of the surface elevation has been measured with altimeters from space and aircraft in the same regions where mass loss is observed. Both radar (Cryosat and European Remote Sensing satellites) and laser altimeters [Ice, Cloud, and land Elevation Satellite 1 (ICESat1) and ICESat2 satellites, Operation IceBridge airborne] are used to measure ice surface elevation. Laser observations are impeded by cloud cover, whereas radar measurements penetrate into the upper portions of the snowpack, introducing some ambiguity. Dropping elevation over the 25-year altimetry period is pronounced in the Amundsen and Bellingshausen Sea sectors of West Antarctica and Wilkes Land in East Antarctica (3). Pine Island, Thwaites, and Smith-Pope-Kohler Glaciers experienced the greatest elevation drop over this period, with changes of up to 9 m/year (Fig. 4). Supporting the observed GRACE mass gain, some margins of East Antarctica are increasing in elevation because of increased snowfall (Fig. 4) (29). Along the Siple Coast, the interior of Kamb Ice Stream has thickened at a rate of ~0.65 m/year over the past 20 years because of its stagnation (Fig. 4) (3). Velocity measurements based on interferometric synthetic aperture radar (SAR) measurements and speckle tracking (4) allow the flow of large regions to be observed with accuracies of several tens of meters per year. The changes in ice sheet velocity are striking in the Peninsula, where a substantial acceleration of glaciers feeding the Larsen ice shelves was observed after their collapse, as well as in the Amundsen Sea sector. In this region, Pine Island Glacier’s velocity doubled from the 1990s to the 2010s (Fig. 4), while its grounding line position, accurately estimated by differential interferometric SAR, retreated by more than 30 km (7). The velocity observations are used to calculate the flux of ice discharge into the ocean and, combined with modeled surface accumulation, to estimate the ice mass gain or loss for the different catchment basins. Through an international collaboration, the scientific community has demonstrated the robust agreement between these three different methods and highlighted the ongoing changes of the Antarctic Ice Sheet (5).
Between 1950 and 2000, the average air temperature in the Peninsula increased by 4°C (30). During this warming period, the Larsen A and B ice shelves collapsed in 1995 and 2002, respectively (Fig. 4). The glaciers feeding the Larsen B Ice Shelf sped up after the loss of the backward stress or buttressing (6, 31). Before the Larsen B collapse, the surface of the ice shelf surface was covered by lakes, indicating that warming air temperatures and surface meltwater can destabilize ice shelves, leading to faster flow of Antarctic ice into the global oceans and highlighting the protecting role of ice shelves (32)...
The evidence for recent changes of Antarctic ice is quantified by three independent measurements primarily derived from satellite and airborne systems: decreasing mass from gravity, dropping surface elevation, and increased surface velocities (Fig. 4).
Changes in ice mass are measured from space with the pair of GRACE (Gravity Recovery and Climate Experiment) satellites, which capture changes in the gravity field experienced by each spacecraft as they orbit Earth together (28). The original pair of satellites resolved monthly changes in Antarctic ice mass from 2002 to 2017 (Fig. 4), and a new pair of satellites, GRACE Follow-On, was launched in 2018 to continue the record of the Earth and Antarctic mass changes. The observed changes must be corrected for modeled changes in motion of the solid Earth to include the crust and the mantle rebound owing to past and ongoing ice mass changes. Determining both the Earth structure and the history of past ice sheet changes are the greatest challenges in separating the observed mass changes into the solid Earth component and the changes in ice mass. The GRACE data (28) show mass loss in West Antarctica, focused in the Amundsen and Bellingshausen Sea sectors, and mass gain in some regions of East Antarctica and along Kamb Ice Stream (Fig. 4).
Lowering of the surface elevation has been measured with altimeters from space and aircraft in the same regions where mass loss is observed. Both radar (Cryosat and European Remote Sensing satellites) and laser altimeters [Ice, Cloud, and land Elevation Satellite 1 (ICESat1) and ICESat2 satellites, Operation IceBridge airborne] are used to measure ice surface elevation. Laser observations are impeded by cloud cover, whereas radar measurements penetrate into the upper portions of the snowpack, introducing some ambiguity. Dropping elevation over the 25-year altimetry period is pronounced in the Amundsen and Bellingshausen Sea sectors of West Antarctica and Wilkes Land in East Antarctica (3). Pine Island, Thwaites, and Smith-Pope-Kohler Glaciers experienced the greatest elevation drop over this period, with changes of up to 9 m/year (Fig. 4). Supporting the observed GRACE mass gain, some margins of East Antarctica are increasing in elevation because of increased snowfall (Fig. 4) (29). Along the Siple Coast, the interior of Kamb Ice Stream has thickened at a rate of ~0.65 m/year over the past 20 years because of its stagnation (Fig. 4) (3). Velocity measurements based on interferometric synthetic aperture radar (SAR) measurements and speckle tracking (4) allow the flow of large regions to be observed with accuracies of several tens of meters per year. The changes in ice sheet velocity are striking in the Peninsula, where a substantial acceleration of glaciers feeding the Larsen ice shelves was observed after their collapse, as well as in the Amundsen Sea sector. In this region, Pine Island Glacier’s velocity doubled from the 1990s to the 2010s (Fig. 4), while its grounding line position, accurately estimated by differential interferometric SAR, retreated by more than 30 km (7). The velocity observations are used to calculate the flux of ice discharge into the ocean and, combined with modeled surface accumulation, to estimate the ice mass gain or loss for the different catchment basins. Through an international collaboration, the scientific community has demonstrated the robust agreement between these three different methods and highlighted the ongoing changes of the Antarctic Ice Sheet (5).
Between 1950 and 2000, the average air temperature in the Peninsula increased by 4°C (30). During this warming period, the Larsen A and B ice shelves collapsed in 1995 and 2002, respectively (Fig. 4). The glaciers feeding the Larsen B Ice Shelf sped up after the loss of the backward stress or buttressing (6, 31). Before the Larsen B collapse, the surface of the ice shelf surface was covered by lakes, indicating that warming air temperatures and surface meltwater can destabilize ice shelves, leading to faster flow of Antarctic ice into the global oceans and highlighting the protecting role of ice shelves (32)...
They continue:
Vulnerabilities
These remote sensing observations allow scientists to observe ice sheet changes and decipher the causes of such changes. Both the ocean surrounding Antarctica and the atmosphere, especially in the Peninsula region, have warmed over the 25-year observational record of ice change (33, 34). Antarctica is losing most of its mass through increased ice flow of the outlet glaciers and ice streams. This contrasts with the Greenland Ice Sheet, where half of the loss is due to faster ice flow and half is due to increased melting of the ice sheet surface (35). Surface melt is not yet a major contributor to ice loss in Antarctica, and global climate models suggest that an increase in snowfall in East Antarctica could partially offset the dynamic mass loss (36). Although these changes have been ongoing for the past three decades, more rapid and dramatic mass loss cannot be excluded...
...The concentration of changes in West Antarctica points to the dominant role the warming ocean plays in recently observed change (39, 40). At the base of the outlet glaciers in the Amundsen Sea, the topography beneath the ice either rises inland or drops. A bed topography dropping inland with ice getting thicker is referred to as a reverse slope. This reverse slope for a marine ice sheet has long been at the core of a concept called the marine ice sheet instability (37). As a glacier retreats across a reverse slope, glacier retreat means thicker ice at the grounding line, and therefore, more ice is leaving the ice sheet, while the region that accumulates snow is reduced. The ice sheet is out of balance. The greater flux of ice results in thinning and additional retreat until a region with an inland rising slope is encountered to stabilize the grounding line (38). In addition to this, ice dynamics imbalance on a reverse slope; the thicker ice at the grounding line means more ice is exposed to warming ocean waters (40). A perturbation can nudge an outlet glacier off a stable point into a region with a reverse slope and have consequences for decades (39, 41). An extreme El Nino event in the 1940s appears to have triggered the grounding line retreat still ongoing in the Pine Island catchment in West Antarctica (42)
Another trigger for rapid and sustained increased ice flux is the collapse of buttressing ice shelves. This concept was widely debated in the science community until the acceleration of the ice flow in the glaciers feeding the Larsen B ice shelf after its collapse in 2003 was observed (6, 31). Shortly before the collapse, this ice shelf surface was covered with lakes, leading to the hypothesis that hydrofracture and loading from lakes can damage an ice shelf sufficiently to induce a catastrophic collapse (32). This mechanism has been incorporated into some ice sheet models (41) but assumes that meltwater is stationary and that little water is transported across an ice shelf. It is now clear that surface water can flow from the grounded ice onto ice shelves (43) and coalesce into rivers atop the ice surface that end as waterfalls at their front (44). Hydrology could therefore have a stabilizing impact on ice sheet mass balance as the distribution of meltwater increases...
These remote sensing observations allow scientists to observe ice sheet changes and decipher the causes of such changes. Both the ocean surrounding Antarctica and the atmosphere, especially in the Peninsula region, have warmed over the 25-year observational record of ice change (33, 34). Antarctica is losing most of its mass through increased ice flow of the outlet glaciers and ice streams. This contrasts with the Greenland Ice Sheet, where half of the loss is due to faster ice flow and half is due to increased melting of the ice sheet surface (35). Surface melt is not yet a major contributor to ice loss in Antarctica, and global climate models suggest that an increase in snowfall in East Antarctica could partially offset the dynamic mass loss (36). Although these changes have been ongoing for the past three decades, more rapid and dramatic mass loss cannot be excluded...
...The concentration of changes in West Antarctica points to the dominant role the warming ocean plays in recently observed change (39, 40). At the base of the outlet glaciers in the Amundsen Sea, the topography beneath the ice either rises inland or drops. A bed topography dropping inland with ice getting thicker is referred to as a reverse slope. This reverse slope for a marine ice sheet has long been at the core of a concept called the marine ice sheet instability (37). As a glacier retreats across a reverse slope, glacier retreat means thicker ice at the grounding line, and therefore, more ice is leaving the ice sheet, while the region that accumulates snow is reduced. The ice sheet is out of balance. The greater flux of ice results in thinning and additional retreat until a region with an inland rising slope is encountered to stabilize the grounding line (38). In addition to this, ice dynamics imbalance on a reverse slope; the thicker ice at the grounding line means more ice is exposed to warming ocean waters (40). A perturbation can nudge an outlet glacier off a stable point into a region with a reverse slope and have consequences for decades (39, 41). An extreme El Nino event in the 1940s appears to have triggered the grounding line retreat still ongoing in the Pine Island catchment in West Antarctica (42)
Another trigger for rapid and sustained increased ice flux is the collapse of buttressing ice shelves. This concept was widely debated in the science community until the acceleration of the ice flow in the glaciers feeding the Larsen B ice shelf after its collapse in 2003 was observed (6, 31). Shortly before the collapse, this ice shelf surface was covered with lakes, leading to the hypothesis that hydrofracture and loading from lakes can damage an ice shelf sufficiently to induce a catastrophic collapse (32). This mechanism has been incorporated into some ice sheet models (41) but assumes that meltwater is stationary and that little water is transported across an ice shelf. It is now clear that surface water can flow from the grounded ice onto ice shelves (43) and coalesce into rivers atop the ice surface that end as waterfalls at their front (44). Hydrology could therefore have a stabilizing impact on ice sheet mass balance as the distribution of meltwater increases...
Figure 4:
The caption:
Fig. 4 Evolution of the Antarctic Ice Sheet over the past two decades.
(A) Spatial ice mass loss (m.w.e.) estimated from GRACE-collected data over the 2002–2017 period (28). Gray areas show the extension of the floating ice shelves that do not contribute directly to sea level rise. (B) Ice front retreat in the Antarctic Peninsula for the Larsen A, B, and C ice shelves between 1995 and 2017 (6, 31). (C) Change in ice velocity between 2005 and 2017 (meters per year) for glaciers in the Amundsen Sea Sector (4). Black lines represent the ice front and grounding lines. (D) Time series of mass loss (gigatons) and associated uncertainties estimated from GRACE-collected data (28).
(A) Spatial ice mass loss (m.w.e.) estimated from GRACE-collected data over the 2002–2017 period (28). Gray areas show the extension of the floating ice shelves that do not contribute directly to sea level rise. (B) Ice front retreat in the Antarctic Peninsula for the Larsen A, B, and C ice shelves between 1995 and 2017 (6, 31). (C) Change in ice velocity between 2005 and 2017 (meters per year) for glaciers in the Amundsen Sea Sector (4). Black lines represent the ice front and grounding lines. (D) Time series of mass loss (gigatons) and associated uncertainties estimated from GRACE-collected data (28).
Unknowns and future directions
...Increasingly, communities around the globe are asking how much the sea level will rise in the coming decades. Although we now know that the answer for each community must incorporate knowledge of local processes, such as isostatic uplift from unloading of ice at the end of the last glacial period and subsidence owing to sediment compaction, changing ocean volume from Antarctic mass loss remains one of the largest contributors to communities’ unknown future. Gaps in our fundamental knowledge of the bathymetry close to the ice sheet and in regions covered by sea ice and ice shelves, the temperature of the deep water masses, the fate of surface meltwater, and the basal conditions beneath the ice sheets introduce limits into our ability to project the future. It is essential that we refine our projections through expanded observational efforts and improved ice sheet models.
Protecting individual cities with walls and barriers only protects those living behind the protection. An ice sheet–based solution might be more equitable...
...Increasingly, communities around the globe are asking how much the sea level will rise in the coming decades. Although we now know that the answer for each community must incorporate knowledge of local processes, such as isostatic uplift from unloading of ice at the end of the last glacial period and subsidence owing to sediment compaction, changing ocean volume from Antarctic mass loss remains one of the largest contributors to communities’ unknown future. Gaps in our fundamental knowledge of the bathymetry close to the ice sheet and in regions covered by sea ice and ice shelves, the temperature of the deep water masses, the fate of surface meltwater, and the basal conditions beneath the ice sheets introduce limits into our ability to project the future. It is essential that we refine our projections through expanded observational efforts and improved ice sheet models.
Protecting individual cities with walls and barriers only protects those living behind the protection. An ice sheet–based solution might be more equitable...
The review's conclusion:
Conclusions
Over the 200 years since Antarctica was first spotted, our knowledge of the continent has shifted from the notion of a stagnant piece of ice to a constantly evolving continent interacting with the ocean around, the atmosphere above, and the solid Earth under it and affected by human activities. Advancing our knowledge of the basic history and fundamental processes that control the ice sheet evolution is crucial to future generations...
Over the 200 years since Antarctica was first spotted, our knowledge of the continent has shifted from the notion of a stagnant piece of ice to a constantly evolving continent interacting with the ocean around, the atmosphere above, and the solid Earth under it and affected by human activities. Advancing our knowledge of the basic history and fundamental processes that control the ice sheet evolution is crucial to future generations...
My feeling is that we don't care all that much for future generations any more than to despise them.
The plague will end, and "Naturally, [we will] have a taste for simple joys; they love women, films and swimming in the sea. But quite reasonably they reserve these pleasures for Saturday night, and Sunday; the other days of the week they work to get lots of money. In the evenings, when they leave their offices, they gather at a regular time in cafes, they walk the same streets, or happily set themselves on their balconies. The desires of the young are violent and brief, while those vices of the older ones go little beyond shooting clubs, friendly banquets, or gambling in high stakes card games."
Business as usual, but our problems will still be here.
This issue of Science is the Antarctic issue.
Times are hard, but I hope you will still make the best of the weekend.
