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Posted on: December 6, 2020


Extensive Early Melting Detected Along the Antarctic Peninsula

In mid-November, about a month before the start of summer in the southern hemisphere, the Antarctic melting season is usually just starting. By that time this year, vast areas along the Antarctic Peninsula were already painted blue with meltwater. The satellite image shows that the sea ice anchored to the peninsula’s coast appears light blue where the surface ice has melted. The white ice farther off the coast is a mixture of broken sea ice and small icebergs. Dark areas indicate open water. By the end of November 2020, much of the meltwater on the ice had refrozen. But scientists want to know if this event was similar to a strong early season melt that launched the 2019-2020 melt season. Last year, unusually warm air and water led to record-breaking melting across the Larsen C Ice Shelf. It is the largest remaining ice shelf along the Antarctic Peninsula, even though it lost a Delaware-sized iceberg in 2017. Widespread melting on Larsen C, located just south of this image, was not apparent in natural-color satellite images. But scientists are watching how this season progresses. The ice shelf surface on the Larsen A was full of ponded meltwater just before its complete collapse in 1995; the same thing occurred before the near-complete collapse of Larsen B in 2002.Only a small remnant of the Larsen B Ice Shelf remains today, stabilized by fast ice in front of the shelf. Loss of the fast ice can destabilize the floating shelf ice, which in turn would allow glacial ice on land to flow unimpeded into the ocean. The effect has already been observed in the Larsen A and upper Larsen B embayments. The second image, acquired on November 11, 2020, offers a detailed view of melting near the northernmost end of the Peninsula. The high temperature recorded that day at Esperanza Base measured 8°C (47°F). That was warmer than average for November, but not nearly as hot as the record-breaking 18.3°C (64.9°F) reached on February 6, 2020. Time will tell if temperatures this melt season will continue to climb and how the ice will respond.

RESPONSE TO ALARM#1: The three images below show lower troposphere average November temperatures in the left frame and decadal trends in those temperatures in the right frame for the South Polar region. The three image present land and ocean, land only, and ocean only temperatures respectively. What we see in these images is that the steep rise in November temperature used to explain the observed ice melt is seen only in ocean temperatures and not in land temperatures. Therefore, although the temperature data are consistent with the attribution of the observed sea ice melt to the observed warming, they do not explain the unusual land ice melt event on the Larsen ice shelf that sits more than 30 meters above the sea surface. Moreover, it should be noted that the location of these ice melt events in terms of their extreme localization to the Antarctic Peninsula, an area known to be geologically active with significant geothermal heat sources, raises serious questions about their attribution to climate phenomena without the any evidence for it. The relevant geological features of the Antarctic Peninsula in terms of the West Antarctic Rift system are described in a related post on this site: LINK: . A brief bibliography on these features of the Antarctic Peninsula is presented below.





  1. Scambos, Ted A., et al. “The link between climate warming and break-up of ice shelves in the Antarctic Peninsula.” Journal of Glaciology 46.154 (2000): 516-530.  A review of in situ and remote-sensing data covering the ice shelves of the Antarctic Peninsula provides a series of characteristics closely associated with rapid shelf retreat: deeply embayed ice fronts; calving of myriad small elongate bergs in punctuated events; increasing flow speed; and the presence of melt ponds on the ice-shelf surface in the vicinity of the break-ups. As climate has warmed in the Antarctic Peninsula region, melt-season duration and the extent of ponding have increased. Most break-up events have occurred during longer melt seasons, suggesting that meltwater itself, not just warming, is responsible. Regions that show melting without pond formation are relatively unchanged. Melt ponds thus appear to be a robust harbinger of ice-shelf retreat. We use these observations to guide a model of ice-shelf flow and the effects of meltwater. Crevasses present in a region of surface ponding will likely fill to the brim with water. We hypothesize (building on Weertman (1973), Hughes (1983) and Van der Veen (1998)) that crevasse propagation by meltwater is the main mechanism by which ice shelves weaken and retreat. A thermodynamic finite-element model is used to evaluate ice flow and the strain field, and simple extensions of this model are used to investigate crack propagation by meltwater. The model results support the hypothesis.
  2. Convey, P., et al. “The flora of the South Sandwich Islands, with particular reference to the influence of geothermal heating.” Journal of Biogeography 27.6 (2000): 1279-1295.  Data obtained in 1997 are combined with updated records from the only previous survey (in 1964) to provide a baseline description of the flora of the archipelago, which currently includes 1 phanerogam, 38 mosses, 11 liverworts, 5 basidiomycete fungi, 41 lichenised fungi and 16 diatoms with, additionally, several taxa identified only to genus. Major elements of the moss and liverwort floras are composed of South American taxa (32% and 73%, respectively), with a further 45% of mosses having bipolar or cosmopolitan distributions. These two groups show low levels of Antarctic endemicity (11% and 18%, respectively). In contrast, 52% of lichens and 80% of basidiomycete fungi are endemic to the Antarctic. A further 36% of lichens are bipolar/cosmopolitan, with only 5% of South American origin. The flora of the South Sandwich Islands is clearly derived from those of other Antarctic zones. The flora of unheated ground is closely related to that of the maritime Antarctic, although with a very limited number of species represented. That of heated ground contains both maritime and sub‐Antarctic elements, confirming the importance of geothermal heating for successful colonisation of the latter group. The occurrence of several maritime Antarctic species only on heated ground confirms the extreme severity of the archipelago’s climate in comparison with well‐studied sites much further south in this biogeographical zone.
  3. Smith, RI Lewis. “The bryophyte flora of geothermal habitats on Deception Island, Antarctica.” The Journal of the Hattori Botanical Laboratory 97 (2005): 233-248.  Deception Island is one of the most volcanically active sites south of 60°S. Between 1967 and 1970 three major eruptions devastated large expanses of the landscape and its predominantly cryptogamic vegetation. Since 1970 extensive recolonisation has occurred on the more stable surfaces. Unheated ground supports several bryophyte and lichen communities typical of much of the maritime Antarctic, but geothermal habitats possess remarkable associations of bryophytes, many of the species being unknown or very rare elsewhere in the Antarctic. Nine geothermal sites were located and their vegetation investigated in detail. Communities associated with more transient sites have disappeared when the geothermal activity ceased. Mosses and liverworts occur to within a few centimetres of fumarole vents where temperatures reach 90-95℃, while temperatures within adjacent moss turf can reach 35-50℃ or more and remain consistently between 25 and 45℃. Most of the bryoflora has a Patagonian-Fuegian provenance and it is presumed that, unlike most species, the thermophiles are not pre-adapted to the Antarctic environment, being able to colonise only where the warm and humid conditions prevail.
  4. Vieira, Gonçalo, et al. “Geomorphological observations of permafrost and ground-ice degradation on Deception and Livingston Islands, Maritime Antarctica.” (2008): 1939-1844. The Antarctic Peninsula is experiencing one of the fastest increases in mean annual air temperatures (ca. 2.5oC in the last 50 years) on Earth. If the observed warming trend continues as indicated by climate models, the region could suffer widespread permafrost degradation. This paper presents field observations of geomorphological features linked to permafrost and ground-ice degradation at two study areas: northwest Hurd Peninsula (Livingston Island) and Deception Island along the Antarctic Peninsula. These observations include thermokarst features, debris flows, active-layer detachment slides, and rockfalls. The processes observed may be linked not only to an increase in temperature, but also to increased rainfall, which can trigger debris flows and other processes. On Deception Island some thermokarst (holes in the ground produced by the selective melting of permafrost)  features may be related to anomalous geothermal heat flux from volcanic activity.
  5. Mulvaney, Robert, et al. “Recent Antarctic Peninsula warming relative to Holocene climate and ice-shelf history.” Nature 489.7414 (2012): 141-144.  Rapid warming over the past 50 years on the Antarctic Peninsula is associated with the collapse of a number of ice shelves and accelerating glacier mass loss1,2,3,4,5,6,7. In contrast, warming has been comparatively modest over West Antarctica and significant changes have not been observed over most of East Antarctica8,9, suggesting that the ice-core palaeoclimate records available from these areas may not be representative of the climate history of the Antarctic Peninsula. Here we show that the Antarctic Peninsula experienced an early-Holocene warm period followed by stable temperatures, from about 9,200 to 2,500 years ago, that were similar to modern-day levels. Our temperature estimates are based on an ice-core record of deuterium variations from James Ross Island, off the northeastern tip of the Antarctic Peninsula. We find that the late-Holocene development of ice shelves near James Ross Island was coincident with pronounced cooling from 2,500 to 600 years ago. This cooling was part of a millennial-scale climate excursion with opposing anomalies on the eastern and western sides of the Antarctic Peninsula. Although warming of the northeastern Antarctic Peninsula began around 600 years ago, the high rate of warming over the past century is unusual (but not unprecedented) in the context of natural climate variability over the past two millennia. The connection shown here between past temperature and ice-shelf stability suggests that warming for several centuries rendered ice shelves on the northeastern Antarctic Peninsula vulnerable to collapse. Continued warming to temperatures that now exceed the stable conditions of most of the Holocene epoch is likely to cause ice-shelf instability to encroach farther southward along the Antarctic Peninsula.
  6. Fraser, Ceridwen I., et al. “Geothermal activity helps life survive glacial cycles.” Proceedings of the National Academy of Sciences 111.15 (2014): 5634-5639.  The evolution and maintenance of diversity through cycles of past climate change have hinged largely on the availability of refugia (places where life can survive through a period of unfavorable conditions such as glaciation). Geothermal refugia may have been particularly important for survival through past glaciations. Our spatial modeling of Antarctic biodiversity indicates that some terrestrial groups likely survived throughout intense glacial cycles on ice-free land or in sub-ice caves associated with areas of geothermal activity, from which recolonization of the rest of the continent took place. These results provide unexpected insights into the responses of various species to past climate change and the importance of geothermal regions in promoting biodiversity. Furthermore, they indicate the likely locations of biodiversity “hotspots” in Antarctica, suggesting a critical focus for future conservation efforts.
  7. An, Meijian, et al. “Temperature, lithosphere‐asthenosphere boundary, and heat flux beneath the Antarctic Plate inferred from seismic velocities.” Journal of Geophysical Research: Solid Earth 120.12 (2015): 8720-8742.  We estimate the upper mantle temperature of the Antarctic Plate based on the thermoelastic properties of mantle minerals and S velocities using a new 3‐D shear velocity model, AN1‐S. Crustal temperatures and surface heat fluxes are then calculated from the upper mantle temperature assuming steady state thermal conduction. The temperature at the top of the asthenosphere beneath the oceanic region and West Antarctica is higher than the dry mantle solidus, indicating the presence of melt. From the temperature values, we generate depth maps of the lithosphere‐asthenosphere boundary and the Curie temperature isotherm. The maps show that East Antarctica has a thick lithosphere similar to that of other stable cratons, with the thickest lithosphere (~250 km) between Domes A and C. The thin crust and lithosphere beneath West Antarctica are similar to those of modern subduction‐related rift systems in East Asia. A cold region beneath the Antarctic Peninsula is similar in spatial extent to that of a flat‐subducted slab beneath the southern Andes, indicating a possible remnant of the Phoenix Plate, which was subducted prior to 10 Ma. The oceanic lithosphere generally thickens with increasing age, and the age‐thickness correlation depends on the spreading rate of the ridge that formed the lithosphere. Significant flattening of the age‐thickness curves is not observed for the mature oceanic lithosphere of the Antarctic Plate.
  8. Dziadek, Ricarda, et al. “Geothermal heat flux in the Amundsen Sea sector of West Antarctica: New insights from temperature measurements, depth to the bottom of the magnetic source estimation, and thermal modeling.” Geochemistry, Geophysics, Geosystems 18.7 (2017): 2657-2672[FULL TEXT]  Focused research on the Pine Island and Thwaites glaciers, which drain the West Antarctic Ice Shelf (WAIS) into the Amundsen Sea Embayment (ASE), revealed strong signs of instability in recent decades that result from variety of reasons, such as inflow of warmer ocean currents and reverse bedrock topography, and has been established as the Marine Ice Sheet Instability hypothesis. Geothermal heat flux (GHF) is a poorly constrained parameter in Antarctica and suspected to affect basal conditions of ice sheets, i.e., basal melting and subglacial hydrology. Thermomechanical models demonstrate the influential boundary condition of geothermal heat flux for (paleo) ice sheet stability. Due to a complex tectonic and magmatic history of West Antarctica, the region is suspected to exhibit strong heterogeneous geothermal heat flux variations. We present an approach to investigate ranges of realistic heat fluxes in the ASE by different methods, discuss direct observations, and 3‐D numerical models that incorporate boundary conditions derived from various geophysical studies, including our new Depth to the Bottom of the Magnetic Source (DBMS) estimates. Our in situ temperature measurements at 26 sites in the ASE more than triples the number of direct GHF observations in West Antarctica. We demonstrate by our numerical 3‐D models that GHF spatially varies from 68 up to 110 mW m−2.
  9. Martos, Yasmina M., et al. “Heat flux distribution of Antarctica unveiled.” Geophysical Research Letters 44.22 (2017): 11-417.  [FULL TEXT]  Antarctica is the largest reservoir of ice on Earth. Understanding its ice sheet dynamics is crucial to unraveling past global climate change and making robust climatic and sea level predictions. Of the basic parameters that shape and control ice flow, the most poorly known is geothermal heat flux. Direct observations of heat flux are difficult to obtain in Antarctica, and until now continent‐wide heat flux maps have only been derived from low‐resolution satellite magnetic and seismological data. We present a high‐resolution heat flux map and associated uncertainty derived from spectral analysis of the most advanced continental compilation of airborne magnetic data. Small‐scale spatial variability and features consistent with known geology are better reproduced than in previous models, between 36% and 50%. Our high‐resolution heat flux map and its uncertainty distribution provide an important new boundary condition to be used in studies on future subglacial hydrology, ice sheet dynamics, and sea level change.
  10. Burton‐Johnson, Alex, et al. “A new heat flux model for the Antarctic Peninsula incorporating spatially variable upper crustal radiogenic heat production.” Geophysical Research Letters 44.11 (2017): 5436-5446.  A new method for modeling heat flux shows that the upper crust contributes up to 70% of the Antarctic Peninsula’s subglacial heat flux and that heat flux values are more variable at smaller spatial resolutions than geophysical methods can resolve. Results indicate a higher heat flux on the east and south of the Peninsula (mean 81 mW m−2) where silicic rocks predominate, than on the west and north (mean 67 mW m−2) where volcanic arc and quartzose sediments are dominant. While the data supports the contribution of heat‐producing element‐enriched granitic rocks to high heat flux values, sedimentary rocks can be of comparative importance dependent on their provenance and petrography. Models of subglacial heat flux must utilize a heterogeneous upper crust with variable radioactive heat production if they are to accurately predict basal conditions of the ice sheet. Our new methodology and data set facilitate improved numerical model simulations of ice sheet dynamics.  
New Paper: Geothermal Heat A Leading Driver Of Surface Temperatures

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