ice sheet – Page 2 – Desdemona Despair

(a) Ocean thermal forcing (shaded areas) at the ocean bottom or 1000 m (whichever is shallower) and annual submarine melt rate (filled squares) at Greenland’s marine-terminating glaciers. The black dotted line shows the 1,000 m isobath and delineates the extent of the continental shelf. The black dashed regions on the ice sheet delineate the hydrological catchments for three large example glaciers: Jakobshavn Isbrae (JI), Helheim (HH) and Kangerdlugssuaq (KG). The five ice sheet regions considered throughout the paper—south (SO), central-west (CW), northwest (NW), northeast (NE) and north (NO)—are delineated by the black ticks. Other labels are the Irminger Sea (Irm), Davis Strait (Dav) and Denmark Strait (Den). Bathymetry is from ref. 42 and ref. 43. (b) Subglacial discharge (x axis, note logarithmic scale) and ocean thermal forcing (y axis) for each marine-terminating glacier. The background shading shows the resulting submarine melt rate. Glaciers are coloured by their regional grouping. The larger squares and error bars show the median and interquartile range for each region, respectively. (c) Submarine melt rate versus grounding line depth by region with fitted linear trends (all significant at the 5% level) as dashed lines. All the results shown in these plots are annually averaged over 1979–2018. Graphic: Slater and Straneo, 2022 / Nature Geoscience

October 21, 2022

Warmer air and warmer water are combining to melt Greenland ice sheet – “This unfortunately adds to the overwhelming body of evidence showing the sensitivity of the Greenland ice sheet to climate change”

By Rachel Koning Beals 17 October 2022 (MarketWatch) – The Greenland ice sheet — one of the two most important glaciers of its kind on Earth — may be even more sensitive to the warming climate than scientists previously thought. The findings, published in the journal Nature Geoscience, shed fresh light on the forces driving ice […]

The location of climate tipping elements in the cryosphere (blue), biosphere (green) and ocean/atmosphere (orange), and global warming levels their tipping points will likely be triggered at 1.5°C. Researchers see signs of destabilisation already in parts of the West Antarctic and Greenland ice sheets, in permafrost regions, the Amazon rainforest, and potentially the Atlantic overturning circulation as well. Graphic: Earth Commission / Globaïa

September 25, 2022

World at risk of passing multiple climate tipping points above 1.5°C global warming

8 September 2022 (Stockholm Resilience Centre) – Multiple climate tipping points could be triggered if global temperature rises beyond 1.5°C above pre-industrial levels, according to a major new analysis published in the journal Science. Even at current levels of global heating the world is already at risk of passing five dangerous climate tipping points, and risks […]

Greenland ice sheet flow sectors, individual catchments and peripheral ice caps with regional correspondence between annual values of mass balance and accumulation area ratio (AAR). The whiskers and ± quantities indicate ensemble single s.d. The ice sector outlines are after Morlighem, et al., 2017. Graphic: Box, et al., 2022 / Nature Climate Change

September 18, 2022

Glaciers and “zombie ice”: The planet is melting at both poles, research finds – “We are already into dangerous levels of greenhouse gases that will have consequences far beyond 10 inches of sea level rise”

By Matthew Rozsa 7 September 2022 (Salon) – That sea levels will rise as Earth’s ice melts is a prophecy that began to come true long ago, at the dawn of industrial civilization when humans began pumping vast amounts of greenhouse gases into the atmosphere. Yet the timeline for sea level rise is not yet fully understood, nor do we really […]

A scientist with PROMIS/GEUS checks instruments on the Greenland ice sheet, 1 September 2021. The ice is darkened by an unprecedented algae bloom caused by persistent cloudy and rainy conditions in 2021 that promoted ice algae growth. Photo: GEUS

January 8, 2022

Algae blooms darken Greenland ice sheet after unprecedented rainfall in 2021 – “I never saw the ice as dark as this”

5 January 2022 (PROMICE) – GEUS and PROMICE professor Jason Box recently made the front page in Danish national media with testimony of algal blooms and rain on the Greenland ice sheet. PROMICE field work helps quantify the ice algae blooms and their effect on melting. In Autumn 2021, Professor Jason Box and two PROMICE […]

Atlantic Meridional Overturning Circulation (AMOC) sea surface temperature (SST) fingerprint. Multimodel mean correlation map between the low-frequency AMOC at 26°N and SST (12). Stars numbered 1 to 16 denote location of sites referred in the figures. The reconstructed AMV at South Sawtooth Lake (1), August temperature in Vøring Plateau off Norway (2), Eastern Fram Strait IRD (3), Atlantic water influence based on C. neoteresis in Western Fram Strait (4), East Greenland Strait N. labradorica (5), North Icelandic shelf temperature based on δ18O from bivalve shells (6), IRD in Denmark Strait (7), the RAPiD-35-COM δ18O T. quinqueloba (8), percentage of Atlantic species in Disko Bugt (9), the RAPID-21-COM sortable silt in the ISOW (10), Gulf of Maine reconstructed SST from bivalve shells (11), titanium (%) in the Cariaco Basin (12), Quelccaya ice record δ18O (13), Huagapo speleothem δ18O (14), and Lake Bosumtwi lake level inferred from δ18O (15). The James Ross Island ice core record with annually resolved δD is shown (16). Graphic: Lapointe and Bradley, 2021 / Science Advances

December 25, 2021

Researchers uncover the surprising cause of the Little Ice Age – “We may be underestimating future ice loss from the Greenland ice sheet”

AMHERST, Massachusetts, 15 December 2021 (University of Massachusetts Amherst) – New research from the University of Massachusetts Amherst provides a novel answer to one of the persistent questions in historical climatology, environmental history and the earth sciences: what caused the Little Ice Age? The answer, we now know, is a paradox: warming. The Little Ice […]

Map showing trends of early-warning indicators of Atlantic Meridional Overturning Circulation (AMOC) collapse. a, Linear trends of the corrected restoring rate λ estimated from the HadISST dataset assuming autocorrelated noise. b, Same as (a) but for the EN4 salinity dataset. c, Linear trends of the variance estimated from the HadISST dataset. d, Same as (c) but for the EN4 salinity dataset. e, Linear trends of the AC1 estimated from the HadISST dataset. f, Same as (e) but for the EN4 salinity dataset. Note the high positive values in the northern Atlantic and the subpolar gyre region in particular for λ and AC1, but also in the southern Atlantic ocean where a salinity pileup has recently been associated with an AMOC slowdown. Graphic: Boers, 2021 / Nature Climate Change

August 22, 2021

Gulf Stream could be veering toward irreversible decline, a new analysis warns – Atlantic current “approaching a critical threshold beyond which the circulation system could collapse”

By Ben Turner 6 August 2021 (LiveScience) – One of the most crucial ocean current systems for regulating the Northern Hemisphere’s climate could be on the verge of total collapse due to climate change, a new study has revealed. The Atlantic Meridional Overturning Circulation (AMOC), which includes the Gulf Stream and is responsible for moderating […]

Deep water underneath the Thwaites ice shelf front is lighter than water outside the ice shelf. (A) Map of trough T3 showing the AUV path color coded by latitude. Shaded region indicates the ice shelf front, and black contours are depth contours. (B) Conservative temperature θ (in degrees Celsius) versus absolute salinity SA (in grams per kilogram) for the AUV data points shown in (A), colors as in (A). Contours show potential density (9) relative to 900 m, and blue arrow indicates isopycnal mixing, i.e., water that has the same density but different temperatures and salinities. Green circles in (A) and (B) show the dense saline deep water found in trough T3 discussed in the main text. (C) Absolute salinity SA (in grams per kilogram) as a function of depth for the AUV data in trough T3 and the CTD data (colors indicate station as in Fig. 3). (D) Potential density (in kilograms per cubic meter) as a function of depth for the AUV data in trough T3 and the CTD data (colors indicate station as in Figs. 3 and 4). Red and blue arrows indicate the two deep water masses discussed in the main text from Pine Island Bay and Thwaites Trough. Dissolved oxygen versus θ and SA is shown in fig. S6. Graphic: Wåhlin, et al., 2021 / Science Advances

April 11, 2021

Exploration of ocean currents beneath the “Doomsday Glacier” by an autonomous underwater vehicle – Net melting of 75 cubic km of ice per year means “the glacier is not stable over time”

9 April 2021 (University of Gothenburg) – For the first time, researchers have been able to obtain data from underneath Thwaites Glacier, also known as the “Doomsday Glacier”. They find that the supply of warm water to the glacier is larger than previously thought, triggering concerns of faster melting and accelerating ice flow. With the […]

Millennium-scale evolution of the Atlantic Meridional Overturning Circulation (AMOC), 400 - 2020. SST-based AMOC reconstructions (light and dark blue) compared to various proxy reconstructions, including land and sea surface temperature reconstructions, sortable silt data, δ18O in benthic foraminifera, δ15N of deep-sea gorgonian corals, and relative abundance of Turborotalita quinqueloba. Since at least 400 AD relatively stable, the AMOC began to decline during the 19th Century which is evident in all proxy records. Around 1950 a phase of particularly rapid decline started that is found in several, largely independent proxies. A short-lived recovery is evident in the 1990s before a return to decline from the mid-2000s. Together these data consistently show that the modern AMOC slowdown is unprecedented in over a thousand years. Graphic: Levke Caesar

March 21, 2021

Gulf Stream System at its weakest in more than a millennium – “This could bring us dangerously close to the tipping point at which the flow becomes unstable”

25 February 2021 (PIK) – Never before in over 1000 years the Atlantic Meridional Overturning Circulation (AMOC), also known as Gulf Stream System, has been as weak as in the last decades. This is the result of a new study by scientists from Ireland, Britain, and Germany. The researchers compiled so-called proxy data – taken […]

Observed sea-level rise in Rockport, Texas, 1969-2020 and projected to 2050. Rockport has the second-highest annual rise rate (7.1 mm/year in 2020), and the highest projected sea-level rise for 2050 at 0.82 meters (2.69 ft) above mean sea level in 1992. Graphic: VIMS

February 28, 2021

U.S. sea-level report cards: 2020 again trends toward acceleration – Water levels at 26 of 32 stations rose at higher rate than in 2019

By David Malmquist 24 January 2021 (VIMS) – Sea level “report cards” issued annually by researchers at William & Mary’s Virginia Institute of Marine Science add further evidence of an accelerating rate of sea-level rise during 2020 at nearly all tidal stations along the U.S. coastline. The team’s web-based report cards project sea level to […]

Map showing the age of sea ice in the Arctic at winter maximum in 2000 (left, week of March 18) and 2020 (right, week of March 21). Ice older than 5 years (white) is very rare today; only a small ribbon remains along the islands of the Canadian Arctic. Age is a stand-in for ice thickness and durability; young ice is thinner and more likely to melt in the summer. NOAA Climate.gov map, based on data from the National Snow and Ice Data Center. Graphic: NOAA

December 14, 2020

Sea ice loss and extreme wildfires mark another year of Arctic change – “The transformation of the Arctic to a warmer, less frozen, and biologically changed region is well underway”

8 December 2020 (NOAA) – NOAA’s 15th Arctic Report Card catalogs for 2020 the numerous ways that climate change continues to disrupt the polar region, with second-highest air temperatures and second-lowest summer sea ice driving a cascade of impacts, including the loss of snow and extraordinary wildfires in northern Russia. The Arctic Report Card is […]