Chapter 22 Modern glaciers and climate change

1997 ◽  
Vol 17 (1) ◽  
pp. 436-448
Author(s):  
Julian A. Dowdeswell ◽  
Evelyn K. Dowdeswell
Keyword(s):  
Ocean Circulation ◽  
General Circulation ◽  
Barents Sea ◽  
General Circulation Models ◽  
High Arctic ◽  
Ice Age ◽  
Svalbard Archipelago ◽  
Air Masses ◽  
Ice Caps ◽  
Novaya Zemlya

By the start of the Holocene, the decay of the large ice sheet over Svalbard and the Barents Sea region was nearing completion, and glacier ice was approaching its present distribution (Elverhøi et al. 1993; Siegert & Dowdeswell 1995). Throughout most of the last 10 000 years, the extent of glaciers and ice caps over the archipelago has been no greater than that observed today, with the exception of minor readvances in the relatively cold 'Little Ice Age', which terminated at the beginning of the twentieth century. Nonetheless, ice today covers about 62% of the 62 000 km2 Svalbard archipelago (Fig. 22.1).Svalbard is one of four heavily ice-covered archipelagos in the Eurasian High Arctic; those to the east are Russian Franz Josef Land, Severnaya Zemlya and Novaya Zemlya. The ice cover on each archipelago is a function of topography and the location of each along the strong west-east gradient in climate across the Eurasian Arctic. Svalbard, as the most westerly of the four, is the warmest and receives the highest precipitation. This is due to its proximity to the relatively warm oceanic North Atlantic Drift and to the depression tracks transferring relatively temperate, moist air masses northward through the Norwegian-Greenland Sea. This position at the northernmost limit of both warm water and air masses makes the archipelago and its glaciers very sensitive to changes in atmospheric and ocean circulation. In addition, General Circulation Models (GCMs) predict that any future C02-induced warming will be most significant at high northern latitudes

scholarly journals A Time History of Pre- and Post-Bomb Radiocarbon in the Barents Sea Derived from Arcto-Norwegian Cod Otoliths

Radiocarbon ◽  
2001 ◽  
Vol 43 (2B) ◽  
pp. 843-855 ◽  
Author(s):  
John M Kalish ◽  
Reidar Nydal ◽  
Kjell H Nedreaas ◽  
George S Burr ◽  
Gro L Eine
Keyword(s):  
Time Series ◽  
Ocean Circulation ◽  
General Circulation ◽  
Barents Sea ◽  
Dissolved Inorganic Carbon ◽  
Time History ◽  
General Circulation Models ◽  
Fine Tuning ◽  
Birth Date ◽  
The Barents Sea

Radiocarbon measured in seawater dissolved inorganic carbon (DIC) can be used to investigate ocean circulation, atmosphere/ocean carbon flux, and provide powerful constraints for the fine-tuning of general circulation models (GCMs). Time series of 14C in seawater are derived most frequently from annual bands of hermatypic corals. However, this proxy is unavailable in temperate and polar oceans. Fish otoliths, calcium carbonate auditory, and gravity receptors in the membranous labyrinths of teleost fishes, can act as proxies for 14C in most oceans and at most depths. Arcto-Norwegian cod otoliths are suited to this application due to the well-defined distribution of this species in the Barents Sea, the ability to determine ages of individual Arcto-Norwegian cod with a high level of accuracy, and the availability of archived otoliths collected for fisheries research over the past 60 years. Using measurements of 14C derived from Arcto-Norwegian cod otoliths, we present the first pre- and post-bomb time series (1919–1992) of 14C from polar seas and consider the significance of these data in relation to ocean circulation and atmosphere/ocean flux of 14C. The data provide evidence for a minor Suess effect of only 0.2‰ per year between 1919 and 1950. Bomb 14C was evident in the Barents Sea as early as 1957 and the highest 14C value was measured in an otolith core from a cod with a birth date of 1967. The otolith 14C data display key features common to records of 14C obtained from a Georges Bank mollusc and corals from the tropical and subtropical North Atlantic.

Lower Cretaceous Barents Sea strata: epicontinental basin configuration, timing, correlation and depositional dynamics

2019 ◽  
Vol 157 (3) ◽  
pp. 458-476 ◽  
Author(s):  
Ivar Midtkandal ◽  
Jan Inge Faleide ◽  
Thea Sveva Faleide ◽  
Christopher Sæbø Serck ◽  
Sverre Planke ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Early Cretaceous ◽  
Barents Sea ◽  
Source Area ◽  
High Arctic ◽  
Large Igneous Province ◽  
Long Distance ◽  
Svalbard Archipelago ◽  
Control Factors ◽  
Architectural Patterns

AbstractA comprehensive dataset is collated in a study on sediment transport, timing and basin physiography during the Early Cretaceous Period in the Boreal Basin (Barents Sea), one of the world’s largest and longest active epicontinental basins. Long-wavelength tectonic tilt related to the Early Cretaceous High Arctic Large Igneous Province (HALIP) set up a fluvial system that developed from a sediment source area in the NW, which flowed SE across the Svalbard archipelago, terminating in a low-accommodation shallow sea within the Bjarmeland Platform area of the present-day Barents Sea. The basin deepened to the SE with a ramp-like basin floor with gentle dip. Seismic data show sedimentary lobes with internal clinoform geometry that advanced from the NW. These lobes interfingered with, and were overlain by, another younger depositional system with similar lobes sourced from the NE. The integrated data allow mapping of architectural patterns that provide information on basin physiography and control factors on source-to-sink transport and depositional patterns within the giant epicontinental basin. The results highlight how low-gradient, low-accommodation sediment transport and deposition has taken place along proximal to distal profiles for several hundred kilometres, in response to subtle changes in base level and by intra-basinal highs and troughs. Long-distance correlation along depositional dip is therefore possible, but should be treated with caution to avoid misidentification of timelines for diachronous surfaces.

scholarly journals Historical droughts in Mediterranean regions during the last 500 years: a data/model approach

2007 ◽  
Vol 3 (2) ◽  
pp. 355-366 ◽  
Author(s):  
S. Brewer ◽  
S. Alleaume ◽  
J. Guiot ◽  
A. Nicault
Keyword(s):  
Drought Stress ◽  
General Circulation ◽  
Distance Measure ◽  
Severity Index ◽  
General Circulation Models ◽  
Ice Age ◽  
Drought Severity ◽  
Atmospheric Circulation Patterns ◽  
Dry Conditions ◽  
Simulated Climate

Abstract. We present here a new method for comparing the output of General Circulation Models (GCMs) with proxy-based reconstructions, using time series of reconstructed and simulated climate parameters. The method uses k-means clustering to allow comparison between different periods that have similar spatial patterns, and a fuzzy logic-based distance measure in order to take reconstruction errors into account. The method has been used to test two coupled ocean-atmosphere GCMs over the Mediterranean region for the last 500 years, using an index of drought stress, the Palmer Drought Severity Index. The results showed that, whilst no model exactly simulated the reconstructed changes, all simulations were an improvement over using the mean climate, and a good match was found after 1650 with a model run that took into account changes in volcanic forcing, solar irradiance, and greenhouse gases. A more detailed investigation of the output of this model showed the existence of a set of atmospheric circulation patterns linked to the patterns of drought stress: 1) a blocking pattern over northern Europe linked to dry conditions in the south prior to the Little Ice Age (LIA) and during the 20th century; 2) a NAO-positive like pattern with increased westerlies during the LIA; 3) a NAO-negative like period shown in the model prior to the LIA, but that occurs most frequently in the data during the LIA. The results of the comparison show the improvement in simulated climate as various forcings are included and help to understand the atmospheric changes that are linked to the observed reconstructed climate changes.

scholarly journals Historical droughts in Mediterranean regions during the last 500 years: a data/model approach

2006 ◽  
Vol 2 (5) ◽  
pp. 771-800 ◽  
Author(s):  
S. Brewer ◽  
S. Alleaume ◽  
J. Guiot ◽  
A. Nicault
Keyword(s):  
Drought Stress ◽  
General Circulation ◽  
Distance Measure ◽  
Severity Index ◽  
General Circulation Models ◽  
Ice Age ◽  
Drought Severity ◽  
Atmospheric Circulation Patterns ◽  
Mediterranean Regions ◽  
Dry Conditions

Abstract. We present here a new method for comparing the output of General Circulation Models (GCMs) with proxy-based reconstructions, using time series of reconstructed and simulated climate parameters. The method uses k-means clustering to allow comparison between different periods that have similar spatial patterns, and a fuzzy logic-based distance measure in order to take reconstruction errors into account. The method has been used to test two coupled ocean-atmosphere GCMs over the Mediterranean region for the last 500 years, using an index of drought stress, the Palmer Drought Severity Index. The results showed that, whilst no model was able to exactly simulate the reconstructed changes, all simulations were an improvement over using the mean climate. Further, a good match was found after 1650 with a model run that took into account changes in volcanic forcing, solar irradiance, and greenhouse gases. A more detailed investigation of the output of this model showed the existence of a set of atmospheric circulation patterns linked to the patterns of drought stress: 1) a blocking pattern over northern Europe linked to dry conditions in the south prior to the Little Ice Age (LIA) and during the 20th century; 2) a NAO-positive like pattern with increased westerlies during the LIA; 3) a NAO-negative like period shown in the model prior to the LIA, but that occurs most frequently in the data during this period. The results of the comparison emphasise the importance of the inclusion of the various forcings in the models and help to understand the atmospheric changes connected to reconstructed climate changes.

scholarly journals Preformed and regenerated phosphate in ocean general circulation models: can right total concentrations be wrong?

2012 ◽  
Vol 9 (5) ◽  
pp. 1797-1807 ◽  
Author(s):  
O. Duteil ◽  
W. Koeve ◽  
A. Oschlies ◽  
O. Aumont ◽  
D. Bianchi ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
General Circulation ◽  
General Circulation Models ◽  
Global Ocean ◽  
Volume Distribution ◽  
Total Phosphate ◽  
Biogeochemical Models ◽  
Ocean General Circulation Models ◽  
Carbon Pump ◽  
Biological Carbon Pump

Abstract. Phosphate distributions simulated by seven state-of-the-art biogeochemical ocean circulation models are evaluated against observations of global ocean nutrient distributions. The biogeochemical models exhibit different structural complexities, ranging from simple nutrient-restoring to multi-nutrient NPZD type models. We evaluate the simulations using the observed volume distribution of phosphate. The errors in these simulated volume class distributions are significantly larger when preformed phosphate (or regenerated phosphate) rather than total phosphate is considered. Our analysis reveals that models can achieve similarly good fits to observed total phosphate distributions for a~very different partitioning into preformed and regenerated nutrient components. This has implications for the strength and potential climate sensitivity of the simulated biological carbon pump. We suggest complementing the use of total nutrient distributions for assessing model skill by an evaluation of the respective preformed and regenerated nutrient components.

scholarly journals Distribution, Composition, and Vertical Fluxes of Particulate Matter in Bays of Novaya Zemlya Archipelago, Vaigach Island at the End of Summer

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
N. V. Politova ◽  
V. P. Shevchenko ◽  
V. V. Zernova
Keyword(s):  
Particulate Matter ◽  
Barents Sea ◽  
Field Studies ◽  
Northwestern Part ◽  
Novaya Zemlya Archipelago ◽  
Svalbard Archipelago ◽  
Novaya Zemlya ◽  
Open Sea ◽  
Distribution Composition ◽  
Migration Pathways

An analysis of suspended particulate matter (SPM) and phytoplankton distribution, composition and vertical particle fluxes in Russkaya Gavan’ Bay (Northern Island of the Novaya Zemlya), Bezymyannaya Bay (Southern Island of the Novaya Zemlya), Dolgaya Bay (northwestern part of the Vaigach Island) in comparison with the data from the Svalbard Archipelago is presented. Field studies were carried out by the authors during the 9th expedition of the RV “Professor Logachev” in September 1994, the 11th, 13th, and 14th expeditions of the RV “Akademik Sergey Vavilov” in September-October 1997 and August-September 1998. The data about Spitsbergen fjords are from literature. Our results show that, on the bays of the Barents Sea islands, most SPM stays in the bays (fjords) and only small part of it reaches the open sea. This is due to the hydrodynamic conditions in the bays, the large size of the particles, flocculation, and often to the morphological barriers in the relief at the bay entrances. It is important for ecological purposes to map out migration pathways of the SPM with pollutants from bays to the open sea. Results of our investigation indicate that the western bays of the Novaya Zemlya act as traps for SPM derived from glaciers and coastal abrasion.

Possible pathways to a Dansgaard-Oeschger (DO) PMIP protocol

2021 ◽  
Author(s):  
Irene Malmierca-Vallet ◽  
Louise C. Sime ◽  
Paul J. Valdes
Keyword(s):  
General Circulation ◽  
Climate Changes ◽  
General Circulation Models ◽  
Ice Age ◽  
Climate Change Projections ◽  
The Past ◽  
External Perturbations ◽  
Mis 3 ◽  
Last Ice Age ◽  
Earth System Models

<p>The DO events of the last ice age represent one of the best studied abrupt climate transitions, yet we still lack a comprehensive explanation for them. There is uncertainty whether current IPCC-relevant models can effectively represent the processes that cause DO events. Current Earth system models (ESMs) seem overly stable against external perturbations and incapable of reproducing most abrupt climate changes of the past (Valdes, 2011). If this holds true, this could noticeably influence their capability to predict future abrupt transitions, with significant consequences for the delivery of precise climate change projections.  In this task, the objectives of this study are (1) to cross compare existing simulations that show spontaneous DO-type oscillations using a common set of diagnostics so we can compare the mechanisms and the characteristics of the oscillations, and (2) to formulate possible pathways to a DO PMIP protocol that could help investigate cold-period instabilities through a range of insolation-, freshwater-, GHG-, and NH ice sheet-related forcings, as well as evaluating the possibility of spontaneous internal oscillations.</p><p>Although most abrupt DO events happened during MIS3, only few studies investigate DO events in coupled general circulation models under MIS 3 conditions (e.g., Kawamura et al., 2017; Zhang and Prange, 2020). Here, we thus propose that the MIS3 period could be the focus of such a DO-event modelling protocol. More specific sensitivity experiments performed under MIS 3 boundary conditions are needed in order to (1) better understand the mechanisms behind millennial-scale climate variability, (2) explore AMOC variability under intermediate glacial conditions, and (3) help answer the question: “are models too stable?”.</p>

Variability in Southern Hemisphere Ocean Circulation from the 1980s to the 2000s

2013 ◽  
Vol 43 (9) ◽  
pp. 1981-2007 ◽  
Author(s):  
K. Katsumata ◽  
S. Masuda
Keyword(s):  
Southern Hemisphere ◽  
Ocean Circulation ◽  
General Circulation ◽  
Antarctic Circumpolar Current ◽  
General Circulation Models ◽  
Polar Front ◽  
Inverse Model ◽  
Meridional Overturning Circulation ◽  
Steady Increase ◽  
Circumpolar Current

Abstract Interannual-to-decadal variability of ocean circulation in the Southern Hemisphere was examined using data from the 1980s to the 2000s in a box inverse model to estimate transport across hydrographic sections and three ocean general circulation models (OGCMs). The westerly wind stress over the OGCM Southern Ocean showed a steady increase of 5%–8% decade−1. The meridional overturning circulation was quantified by the transport across 30°S. The OGCMs suggested a slight strengthening [from 0.2 ± 1.0 to 0.8 ± 1.3 Sv decade−1 (1 Sv ≡ 106 m3 s−1)] of the upper meridional cell (Deacon cell) and two OGCMs showed a weakening (−0.8 ± 0.6 and −1.0 ± 0.3 Sv decade−1) of the lower meridional [Antarctic Bottom Water (AABW)] cell, partly explained by contraction of the AABW volume. The box inverse estimates did not contradict these two findings. For Antarctic Circumpolar Current transport, quantified by zonal transport across four key sections, the box inverse model estimated a decrease of 5–21 Sv. Decomposition of the decrease into baroclinic transport by the Subantarctic and Polar Fronts, barotropic transport, and others shows that the decrease is mostly due to barotropic transport and transport carried by the flow north of the Subantarctic Front and south of the Polar Front. In the OGCMs, the variability of transport across key sections is often correlated with transport carried by a flow south of the Polar Front and with the southern annular mode index. In all models, then, the transport of the Antarctic Circumpolar Current, defined as the transport carried by the fronts, has not decreased significantly over the study period.

scholarly journals Impact of Timanian thrust systems on the late Neoproterozoic–Phanerozoic tectonic evolution of the Barents Sea and Svalbard

Solid Earth ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 85-115
Author(s):  
Jean-Baptiste P. Koehl ◽  
Craig Magee ◽  
Ingrid M. Anell
Keyword(s):  
Plate Tectonics ◽  
Barents Sea ◽  
Magnetic Data ◽  
Svalbard Archipelago ◽  
Northern Norway ◽  
Novaya Zemlya ◽  
Tectonic History ◽  
The Barents Sea ◽  
Late Neoproterozoic ◽  
Northwestern Russia

Abstract. The Svalbard Archipelago consists of three basement terranes that record a complex Neoproterozoic–Phanerozoic tectonic history, including four contractional events (Grenvillian, Caledonian, Ellesmerian, and Eurekan) and two episodes of collapse- to rift-related extension (Devonian–Carboniferous and late Cenozoic). Previous studies suggest that these three terranes likely accreted during the early to mid-Paleozoic Caledonian and Ellesmerian orogenies. Yet recent geochronological analyses show that the northwestern and southwestern terranes of Svalbard both record an episode of amphibolite (–eclogite) facies metamorphism in the latest Neoproterozoic, which may relate to the 650–550 Ma Timanian Orogeny identified in northwestern Russia, northern Norway, and the Russian Barents Sea. However, discrete Timanian structures have yet to be identified in Svalbard and the Norwegian Barents Sea. Through analysis of seismic reflection, as well as regional gravimetric and magnetic data, this study demonstrates the presence of continuous thrust systems that are several kilometers thick, NNE-dipping, deeply buried, and extend thousands of kilometers from northwestern Russia to northeastern Norway, the northern Norwegian Barents Sea, and the Svalbard Archipelago. The consistency in orientation and geometry, as well as apparent linkage between these thrust systems and those recognized as part of the Timanian Orogeny in northwestern Russia and Novaya Zemlya, suggests that the mapped structures are likely Timanian. If correct, these findings would imply that Svalbard's three basement terranes and the Barents Sea were accreted onto northern Norway during the Timanian Orogeny and should hence be attached to Baltica and northwestern Russia in future Neoproterozoic–early Paleozoic plate tectonics reconstructions. In the Phanerozoic, the study suggests that the interpreted Timanian thrust systems represent major preexisting zones of weakness that were reactivated, folded, and overprinted by (i.e., controlled the formation of new) brittle faults during later tectonic events. These faults are still active at present and can be linked to folding and offset of the seafloor.

scholarly journals A Closer look at the Proposed Late-Wisconsin-Weichselian Arctic Ice Sheet

1979 ◽  
Vol 24 (90) ◽  
pp. 497-500
Author(s):  
J. L. Fastook ◽  
R. Sweet ◽  
T. J. Hughes
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
High Arctic ◽  
Ice Age ◽  
Arctic Seas ◽  
Ice Caps ◽  
Atmospheric Circulation Patterns ◽  
Circulation Patterns ◽  
Arctic Ice ◽  
The Tropics

AbstractThe CLIMAP 18000 years b.p. experiment required reconstructing late-Wisconsin-Weichselian ice sheets. In the Northern Hemisphere, the greatest uncertainty in these reconstructions is the area covered by ice sheets. Two schools of thought exist (Hughes and others, in press). The minimum-ice-sheet school holds that ice sheets originated from present ice caps in the High Arctic islands, but the northern seaward margins of these ice sheets retreated as the southern landward margins advanced. This occurred because northern margins became isolated from sources of precipitation as Arctic seas became permanently ice-covered and the advancing southern margin changed atmospheric circulation patterns. In this view, these ice sheets stay about the same size and migrate southward during an ice age. Northern margins rarely reach sea-level during the later stage of the ice age so no marine portions form and ablation is by melting or sublimation. Marine portions formed only when the ice sheets migrated across shallow seas between the High Arctic islands and the mainland. At the end of the ice age, huge amounts of heat had to be transferred from the tropics to the ice sheets in order to account for late-Wisconsin-Weichselian and Holocene retreat-rates by melting along ice-sheet margins.

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