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ARCTIC WARMING ALARM OF OCTOBER 2020

Posted on: October 28, 2020

Laptev Sea:: Blackbourn Geological Services

IT IS REPORTED IN THE MEDIA: LINK: https://www.theguardian.com/world/2020/oct/22/alarm-as-arctic-sea-ice-not-yet-freezing-at-latest-date-on-record that anthropogenic global warming is causing extreme and dangerous heat anomalies in the Arctic that have devastating implications in terms of feedback acceleration and the future evolution of catastrophic global warming. The Guardian has written what climate scientists have told them about this sea ice event.

WHAT CLIMATE SCIENTISTS SAY

Alarm as Arctic sea ice not yet freezing at latest date on record
Delayed freeze in Laptev Sea could have knock-on effects across polar region. Climate change is pushing warmer Atlantic currents into the Arctic and breaking up the usual stratification between warm deep waters and the cool surface. This also makes it difficult for ice to form. For the first time since records began, the main nursery of Arctic sea ice in Siberia has yet to start freezing in late October. The delayed annual freeze in the Laptev Sea has been caused by freakishly protracted warmth in northern Russia and the intrusion of Atlantic waters, say climate scientists who warn of possible knock-on effects across the polar region. Ocean temperatures in the area recently climbed to more than 5C above average, following a record breaking heatwave and the unusually early decline of last winter’s sea ice. The trapped heat takes a long time to dissipate into the atmosphere, even at this time of the year when the sun creeps above the horizon for little more than an hour or two each day. Graphs of sea-ice extent in the Laptev Sea, which usually show a healthy seasonal pulse, appear to have flat-lined. As a result, there is a record amount of open sea in the Arctic.

The lack of freeze-up so far this fall is unprecedented in the Siberian Arctic region,” said Zachary Labe, a postdoctoral researcher at Colorado State University. He says this is in line with the expected impact of human-driven climate change. 2020 is another year that is consistent with a rapidly changing Arctic. Without a systematic reduction in greenhouse gases, the likelihood of our first ‘ice-free’ summer will continue to increase by the mid-21st century,” (Zack Labe). This year’s Siberian heatwave was made at least 600 times more likely by industrial and agricultural emissions, according to an earlier study. The warmer air temperature is not the only factor slowing the formation of ice. Climate change is also pushing more balmy Atlantic currents into the Arctic and breaking up the usual stratification between warm deep waters and the cool surface. This also makes it difficult for ice to form. This continues a streak of very low extents. The last 14 years, 2007 to 2020, are the lowest 14 years in the satellite record starting in 1979,. The Arctic is now disappearing, leaving thinner seasonal ice. Overall the average thickness is half what it was in the 1980s.The downward trend is likely to continue until the Arctic has its first ice-free summer. The data and models suggest this will occur between 2030 and 2050. “It’s a matter of when, not if. Scientists are concerned the delayed freeze could amplify feedbacks that accelerate the decline of the sea ice. It is already well known that a smaller area of ice means less of a white area to reflect the sun’s heat back into space. But this is not the only reason the Arctic is warming more than twice as fast as the global average. The Laptev Sea is known as the birthplace of ice, which forms along the coast there in early winter, then drifts westward carrying nutrients across the Arctic, before breaking up in the spring in the Fram Strait between Greenland and Svalbard. If ice forms late in the Laptev, it will be thinner and thus more likely to melt before it reaches the Fram Strait. This could mean fewer nutrients for Arctic plankton, which will then have a reduced capacity to draw down carbon dioxide from the atmosphere. More open sea also means more turbulence in the upper layer of the Arctic ocean, which draws up more warm water from the depths. The sea ice trends are grim but not surprising. “It is more frustrating than shocking. This has been forecast for a long time, but there has been little substantial response by decision-makers.

Arctic Ocean: why winter sea ice has stalled, and what it means for the  rest of the world

CRITICAL COMMENTARY

ABOUT THE LAPTEV SEA: The Laptev Sea is the southern termination of the Gakkel spreading ridge. The Laptev Rift System consists of several deep subsided rifts and high standing blocks of the basement. Details of this geological feature are described by Sergey Drachev in his paper on the geology of the continental shelf of the Laptev Sea. The full text of the paper is available on request. The Arctic is geologically active and its temperature and sea ice dynamics cannot be understood exclusively in terms of the atmosphere above the sea ice without consideration of the geology of the region below the sea ice described in a related post on this site : LINK: https://tambonthongchai.com/2019/07/01/arctic/ . Further evidence of geological activity and hydrothermal venting in this regions is described in the bibliography below and in a summary of the relevant information on geological activity in the Laptev Sea area of the Arctic. Based on these data we propose that sea ice dynamics in this region cannot be understood exclusively in terms of atmospheric phenomena. Statistical analysis of Arctic sea ice dynamics does not show a correlation with atmospheric temperature phenomena. Details of this issue are presented in related posts on this site listed below.

bandicam 2019-07-01 16-29-44-526
arctic-sea-ice2

RELATED POSTS ON ARCTIC SEA ICE DYNAMICS

  1. Precipitous Decline in Arctic Sea Ice Volume https://tambonthongchai.com/2019/11/07/precipitous-decline-in-arctic-sea-ice-volume/
  2. Sea Ice Extent & Area 1979-2019 https://tambonthongchai.com/2019/09/28/sea-ice-extent-area-1979-2018/
  3. Does Global Warming Drive Changes in Arctic Sea Ice? https://tambonthongchai.com/2018/08/04/does-global-warming-drive-changes-in-arctic-sea-ice/
PDF) Structure and geology of the continental shelf of the Laptev Sea,  Eastern Russian Arctic

GEOLOGY OF THE GAKKEL RIDGE AND LAPTEV SEA RIFT SYSTEM

The Laptev Sea is south of the Gakkel slow spreading ridge. This region is geologically active with seafloor geological features consisting of episodic but intense events of hydrothermal plumes, explosive volcanism, and magmatic flows. Sea ice dynamics and extreme ocean temperature anomalies in this region cannot be understood strictly in terms of atmospheric phenomena such as anthropogenic global warming particularly so when the sea ice dynamics at issue are episodic, localized, and extreme. In light of the influence of the Gakkel Ridge, the study of sea ice and sea surface temperature events in the region must be inclusive of these geological features. The Arctic in general is a very geologically active area and the study of ice melt and ocean temperature events in there must pay attention to these significant sources of heat. A RELEVANT BIBLIOGRAPHY ON THIS TOPIC IS PROVIDED BELOW FOR REFERENCE.

arctic-sea-ice3
Hydrothermal Plume Studies - EOI Program

BGR - Projects - Deformation of Continental Lithosphere on the Laptev Sea  Shelf

The Gakkel Ridge: Bathymetry, gravity anomalies, and crustal accretion at  extremely slow spreading rates - Cochran - 2003 - Journal of Geophysical  Research: Solid Earth - Wiley Online Library

In the bibliography provided below we find strong support for intense episodic geological events in this region in the form of magmatic events, explosive volcanism, and hydrothermal plumes. It is not possible to interpret localized heat and ice melt episodic events in such locations exclusively as atmospheric phenomena or impacts of anthropogenic global warming with the implication that they can and must be attenuated by taking climate action.

PDF) Is Isostatic Rebound in Slow Spreading Gakkel Ridge of Arctic Region  Due to the Climate Change? A Case Study

THE RELEVANT BIBLIOGRAPHY

  1. Baker, Edward T., et al. “Hydrothermal venting in magma deserts: The ultraslow‐spreading Gakkel and Southwest Indian Ridges.” Geochemistry, Geophysics, Geosystems 5.8 (2004). Detailed hydrothermal surveys over ridges with spreading rates of 50–150 mm/yr have found a linear relation between spreading rate and the spatial frequency of hydrothermal venting, but the validity of this relation at slow and ultraslow ridges is unproved. Here we compare hydrothermal plume surveys along three sections of the Gakkel Ridge (Arctic Ocean) and the Southwest Indian Ridge (SWIR) to determine if hydrothermal activity is similarly distributed among these ultraslow ridge sections and if these distributions follow the hypothesized linear trend derived from surveys along fast ridges. Along the Gakkel Ridge, most apparent vent sites occur on volcanic highs, and the extraordinarily weak vertical density gradient of the deep Arctic permits plumes to rise above the axial bathymetry. Individual plumes can thus be extensively dispersed along axis, to distances >200 km, and ∼75% of the total axial length surveyed is overlain by plumes. Detailed mapping of these plumes points to only 9–10 active sites in 850 km, however, yielding a site frequency Fs, sites/100 km of ridge length, of 1.1–1.2. Plumes detected along the SWIR are considerably less extensive for two reasons: an apparent paucity of active vent fields on volcanic highs and a normal deep‐ocean density gradient that prevents extended plume rise. Along a western SWIR section (10°–23°E) we identify 3–8 sites, so Fs = 0.3–0.8; along a previously surveyed 440 km section of the eastern SWIR (58°–66°E), 6 sites yield Fs = 1.3. Plotting spreading rate (us) versus Fs, the ultraslow ridges and eight other ridge sections, spanning the global range of spreading rate, establish a robust linear trend (Fs = 0.98 + 0.015us), implying that the long‐term heat supply is the first‐order control on the global distribution of hydrothermal activity. Normalizing Fs to the delivery rate of basaltic magma suggests that ultraslow ridges are several times more efficient than faster‐spreading ridges in supporting active vent fields. This increased efficiency could derive from some combination of three‐dimensional magma focusing at volcanic centers, deep mining of heat from gabbroic intrusions and direct cooling of the upper mantle, and nonmagmatic heat supplied by exothermic serpentinization.
  2. Edwards, M. H., et al. “Evidence of recent volcanic activity on the ultraslow-spreading Gakkel ridge.” Nature 409.6822 (2001): 808-812. Seafloor spreading is accommodated by volcanic and tectonic processes along the global mid-ocean ridge system. As spreading rate decreases the influence of volcanism also decreases1,2,3,4, and it is unknown whether significant volcanism occurs at all at ultraslow spreading rates (<1.5 cm yr-1). Here we present three-dimensional sonar maps of the Gakkel ridge, Earth’s slowest-spreading mid-ocean ridge, located in the Arctic basin under the Arctic Ocean ice canopy. We acquired this data using hull-mounted sonars attached to a nuclear-powered submarine, the USS Hawkbill. Sidescan data for the ultraslow-spreading (∼1.0 cm yr-1) eastern Gakkel ridge depict two young volcanoes covering approximately 720 km2 of an otherwise heavily sedimented axial valley. The western volcano coincides with the average location of epicentres for more than 250 teleseismic events detected5,26 in 1999, suggesting that an axial eruption was imaged shortly after its occurrence. These findings demonstrate that eruptions along the ultraslow-spreading Gakkel ridge are focused at discrete locations and appear to be more voluminous and occur more frequently than was previously thought.
  3. Sohn, Robert A., et al. “Explosive volcanism on the ultraslow-spreading Gakkel ridge, Arctic Ocean.” Nature 453.7199 (2008): 1236-1238. Roughly 60% of the Earth’s outer surface is composed of oceanic crust formed by volcanic processes at mid-ocean ridges. Although only a small fraction of this vast volcanic terrain has been visually surveyed or sampled, the available evidence suggests that explosive eruptions are rare on mid-ocean ridges, particularly at depths below the critical point for seawater (3,000 m)1. A pyroclastic deposit has never been observed on the sea floor below 3,000 m, presumably because the volatile content of mid-ocean-ridge basalts is generally too low to produce the gas fractions required for fragmenting a magma at such high hydrostatic pressure. We employed new deep submergence technologies during an International Polar Year expedition to the Gakkel ridge in the Arctic Basin at 85° E, to acquire photographic and video images of ‘zero-age’ volcanic terrain on this remote, ice-covered ridge. Here we present images revealing that the axial valley at 4,000 m water depth is blanketed with unconsolidated pyroclastic deposits, including bubble wall fragments (limu o Pele)2, covering a large (>10 km2) area. At least 13.5 wt% CO2 is necessary to fragment magma at these depths3, which is about tenfold the highest values previously measured in a mid-ocean-ridge basalt4. These observations raise important questions about the accumulation and discharge of magmatic volatiles at ultraslow spreading rates on the Gakkel ridge5 and demonstrate that large-scale pyroclastic activity is possible along even the deepest portions of the global mid-ocean ridge volcanic system.
  4. Michael, P. J., et al. “Magmatic and amagmatic seafloor generation at the ultraslow-spreading Gakkel ridge, Arctic Ocean.” Nature 423.6943 (2003): 956-961. A high-resolution mapping and sampling study of the Gakkel ridge was accomplished during an international ice-breaker expedition to the high Arctic and North Pole in summer 2001. For this slowest-spreading endmember of the global mid-ocean-ridge system, predictions were that magmatism should progressively diminish as the spreading rate decreases along the ridge, and that hydrothermal activity should be rare. Instead, it was found that magmatic variations are irregular, and that hydrothermal activity is abundant. A 300-kilometre-long central amagmatic zone, where mantle peridotites are emplaced directly in the ridge axis, lies between abundant, continuous volcanism in the west, and large, widely spaced volcanic centres in the east. These observations demonstrate that the extent of mantle melting is not a simple function of spreading rate: mantle temperatures at depth or mantle chemistry (or both) must vary significantly along-axis. Highly punctuated volcanism in the absence of ridge offsets suggests that first-order ridge segmentation is controlled by mantle processes of melting and melt segregation. The strong focusing of magmatic activity coupled with faulting may account for the unexpectedly high levels of hydrothermal activity observed.
  5. Edmonds, H. N., et al. “Discovery of abundant hydrothermal venting on the ultraslow-spreading Gakkel ridge in the Arctic Ocean.” Nature 421.6920 (2003): 252-256. Submarine hydrothermal venting along mid-ocean ridges is an important contributor to ridge thermal structure1, and the global distribution of such vents has implications for heat and mass fluxes from the Earth’s crust and mantle and for the biogeography of vent-endemic organisms. Previous studies have predicted that the incidence of hydrothermal venting would be extremely low on ultraslow-spreading ridges (ridges with full spreading rates <2 cm yr-1—which make up 25 per cent of the global ridge length), and that such vent systems would be hosted in ultramafic in addition to volcanic rocks4,5. Here we present evidence for active hydrothermal venting on the Gakkel ridge, which is the slowest spreading (0.6–1.3 cm yr-1) and least explored mid-ocean ridge. On the basis of water column profiles of light scattering, temperature and manganese concentration along 1,100 km of the rift valley, we identify hydrothermal plumes dispersing from at least nine to twelve discrete vent sites. Our discovery of such abundant venting, and its apparent localization near volcanic centres, requires a reassessment of the geologic conditions that control hydrothermal circulation on ultraslow-spreading ridges.
  6. Hellebrand, Eric, Jonathan E. Snow, and Richard Mühe. “Mantle melting beneath Gakkel Ridge (Arctic Ocean): abyssal peridotite spinel compositions.” Chemical Geology 182.2-4 (2002): 227-235. The ultraslow spreading Gakkel Ridge represents one of the most extreme spreading environments on the Earth. Full spreading rates there of 0.6–1.3 cm/year and Na8.0 in basalts of 3.3 imply an extremely low degree of mantle partial melting. For this reason, the complementary degree of melting registered by abyssal peridotite melting residues is highly interesting. In a single sample of serpentinized peridotite from Gakkel Ridge, we found spinels which, though locally altered, have otherwise unzoned and thus primary compositions in the cores of the grains. These reflect a somewhat higher degree of melting of the uppermost oceanic mantle than indicated by basalt compositions. Cr/(Cr+Al) ratios of these grains lie between 0.23 and 0.24, which is significantly higher than spinels from peridotites collected along the faster spreading Mid-Atlantic and Southwest Indian Ridges. Crustal thickness at Gakkel Ridge can be calculated from the peridotite spinel compositions, and is thicker than the crustal thickness of less than 4 km estimated from gravity data, or predicted from global correlations between spreading rate and seismically determined crustal thickness. The reason for this unexpected result may be local heterogeneity due to enhanced melt focussing at an ultraslow spreading ridge.
  7. Tolstoy, M., et al. “Seismic character of volcanic activity at the ultraslow-spreading Gakkel Ridge.” Geology 29.12 (2001): 1139-1142. Never before has a volcanic eruption on a slow- or ultraslow- spreading mid-ocean ridge been both observed seismically and confirmed on the seafloor. During the first half of 1999, a long-lived volcanic-spreading event occurred on the ultraslow-spreading Gakkel Ridge in the Arctic Ocean. The seismicity associated with this event was unprecedented in duration and magnitude for a seafloor eruption. Sonar images from the U.S.S. Hawkbill, which passed over the area within four months of the start of activity, are consistent with the presence of a large, recently erupted flow and a volcanic peak directly in the area of seismic activity. Seismic activity began in mid-January and continued vigorously for three months; a reduced rate of activity persisted for an additional four months or more. In total, 252 events were large enough to be recorded on global seismic networks. Although a limited number of volcanic-spreading events have been observed globally, the duration and magnitude of the Gakkel Ridge swarm, when compared with volcanic seismicity at ridges spreading at intermediate and fast spreading rates, suggest that a negative power-law relationship may exist between these parameters and spreading rate. Fault activation, in response to magmatic emplacement, appears to have occurred over a broad region, suggesting that magma may have been tapped from mantle depths. The slow migration of the largest magnitude events along the axis of the rift valley suggests multiple magmatic pulses at depth. In combination with bathymetric setting and sidescan sonar confirmation, the seismic data for this event have provided a unique look at the scale and character of eruption processes at ultraslow-spreading rates.

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