scholarly journals Ice-sheet melt drove methane emissions in the Arctic during the last two interglacials

Geology ◽  
2021 ◽  
Author(s):  
P.-A. Dessandier ◽  
J. Knies ◽  
A. Plaza-Faverola ◽  
C. Labrousse ◽  
M. Renoult ◽  
...  
Keyword(s):  
Planktonic Foraminifera ◽  
Ice Sheet ◽  
Progressive Increase ◽  
Methane Emissions ◽  
The Arctic ◽  
Ca 125 ◽  
Gas Reservoirs ◽  
Glacial Ice ◽  
Ice Melt ◽  
Drill Holes

Circum-Arctic glacial ice is melting in an unprecedented mode, and release of currently trapped geological methane may act as a positive feedback on ice-sheet retreat during global warming. Evidence for methane release during the penultimate (Eemian, ca. 125 ka) interglacial, a period with less glacial sea ice and higher temperatures than today, is currently absent. Here, we argue that based on foraminiferal isotope studies on drill holes from offshore Svalbard, Norway, methane leakage occurred upon the abrupt Eurasian ice-sheet wastage during terminations of the last (Weichselian) and penultimate (Saalian) glaciations. Progressive increase of methane emissions seems to be first recorded by depleted benthic foraminiferal δ13C. This is quickly followed by the precipitation of methane-derived authigenic carbonate as overgrowth inside and outside foraminiferal shells, characterized by heavy δ18O and depleted δ13C of both benthic and planktonic foraminifera. The similarities between the events observed over both terminations advocate for a common driver for the episodic release of geological methane stocks. Our favored model is recurrent leakage of shallow gas reservoirs below the gas hydrate stability zone along the margin of western Svalbard that can be reactivated upon initial instability of the grounded, marine-based ice sheets. Analogous to this model, with the current acceleration of the Greenland ice melt, instabilities of existing methane reservoirs below and nearby the ice sheet are likely.

scholarly journals Quantification of the Greenland ice sheet contribution to Last Interglacial sea-level rise

2012 ◽  
Vol 8 (4) ◽  
pp. 2731-2776 ◽  
Author(s):  
E. J. Stone ◽  
D. J. Lunt ◽  
J. D. Annan ◽  
J. C. Hargreaves
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
The Arctic ◽  
Substantial Contribution ◽  
Orbital Forcing ◽  
Last Interglacial ◽  
Ice Melt ◽  
A Value

Abstract. The Last Interglaciation (~ 130–115 thousand years ago) was a time when the Arctic climate was warmer than today (Anderson et al., 2006; Kaspar et al., 2005) and sea-level extremely likely at least 6 m higher (Kopp et al., 2009). However, there is large uncertainty in the relative contributions to this sea-level rise from the Greenland and Antarctic ice sheets and smaller icefields (Otto-Bliesner et al., 2006; Huybrechts, 2002; Letréguilly et al., 1991; Ritz et al., 1997; Cuffey and Marshall, 2000; Tarasov and Peltier, 2003; Lhomme et al., 2005; Greve, 2005; Robinson et al., 2011; Fyke et al., 2011). By performing an ensemble of 500 coupled climate – ice sheet model simulations, constrained by paleo-data, we determine probabilistically the likely contribution of Greenland ice sheet melt to Last Interglacial sea-level rise, taking into account model uncertainty. Here we show a 90% probability that Greenland ice melt contributed at least 0.6 m but less than 10% probability it exceeded 3.5 m, a value which is lower than several recent estimates (Cuffey and Marshall, 2000; Tarasov and Peltier, 2003; Lhomme et al., 2005; Robinson et al., 2011). Our combined modelling and paleo-data approach suggests that the Greenland ice sheet is less sensitive to orbital forcing than previously thought, and implicates Antarctic melt as providing a substantial contribution to Last Interglacial sea-level rise.

scholarly journals Supplemental Material: Ice-sheet melt drove methane emissions in the Arctic during the last two interglacials

2021 ◽  
Author(s):  
Pierre-Antoine Dessandier ◽  
et al.
Keyword(s):  
Ice Sheet ◽  
Methane Emissions ◽  
The Arctic

Supplemental methods on micropaleontolgy, dating and MeBo drilling and supplemental notes on chronology and foraminiferal preservation.<br>

scholarly journals Supplemental Material: Ice-sheet melt drove methane emissions in the Arctic during the last two interglacials

2021 ◽  
Author(s):  
Pierre-Antoine Dessandier ◽  
et al.
Keyword(s):  
Ice Sheet ◽  
Methane Emissions ◽  
The Arctic

Supplemental methods on micropaleontolgy, dating and MeBo drilling and supplemental notes on chronology and foraminiferal preservation.<br>

scholarly journals A warm jet in a cold ocean

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jennifer A. MacKinnon ◽  
Harper L. Simmons ◽  
John Hargrove ◽  
Jim Thomson ◽  
Thomas Peacock ◽  
...  
Keyword(s):  
The Arctic ◽  
Bering Strait ◽  
Near Surface ◽  
Ice Melt ◽  
Beaufort Gyre ◽  
The Pacific ◽  
Climate Simulations ◽  
Initial Evolution ◽  
Forecast Models

AbstractUnprecedented quantities of heat are entering the Pacific sector of the Arctic Ocean through Bering Strait, particularly during summer months. Though some heat is lost to the atmosphere during autumn cooling, a significant fraction of the incoming warm, salty water subducts (dives beneath) below a cooler fresher layer of near-surface water, subsequently extending hundreds of kilometers into the Beaufort Gyre. Upward turbulent mixing of these sub-surface pockets of heat is likely accelerating sea ice melt in the region. This Pacific-origin water brings both heat and unique biogeochemical properties, contributing to a changing Arctic ecosystem. However, our ability to understand or forecast the role of this incoming water mass has been hampered by lack of understanding of the physical processes controlling subduction and evolution of this this warm water. Crucially, the processes seen here occur at small horizontal scales not resolved by regional forecast models or climate simulations; new parameterizations must be developed that accurately represent the physics. Here we present novel high resolution observations showing the detailed process of subduction and initial evolution of warm Pacific-origin water in the southern Beaufort Gyre.

scholarly journals A new bedrock and surface elevation dataset for modelling the Greenland ice sheet

2003 ◽  
Vol 37 ◽  
pp. 351-356 ◽  
Author(s):  
Jonathan L. Bamber ◽  
Duncan J. Baldwin ◽  
S. Prasad Gogineni
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Detailed Comparison ◽  
Radar Data ◽  
The Arctic ◽  
Small Scale ◽  
Surface Model ◽  
Rock Outcrops ◽  
Bed Topography ◽  
Elevation Model

AbstractA new digital elevation model of the surface of the Greenland ice sheet and surrounding rock outcrops has been produced from a comprehensive suite of satellite and airborne remote-sensing and cartographic datasets. The surface model has been regridded to a resolution of 5 km, and combined with a new ice-thickness grid derived from ice-penetrating radar data collected in the 1970s and 1990s. A further dataset, the International Bathymetric Chart of the Arctic Ocean, was used to extend the bed elevations to include the continental shelf. The new bed topography was compared with a previous version used for ice-sheet modelling. Near the margins of the ice sheet and, in particular, in the vicinity of small-scale features associated with outlet glaciers and rapid ice motion, significant differences were noted. This was highlighted by a detailed comparison of the bed topography around the northeast Greenland ice stream.

Advanced Weathervaning in Ice

2011 ◽  
Author(s):  
William Hidding ◽  
Guillaume Bonnaffoux ◽  
Mamoun Naciri
Keyword(s):  
Rapid Change ◽  
Ice Sheet ◽  
Model Tests ◽  
The Arctic ◽  
Mooring System ◽  
Sudden Increase ◽  
Time Step ◽  
Ice Loads ◽  
Level Ice ◽  
Drift Direction

The reported presence of one third of remaining fossil reserves in the Arctic has sparked a lot of interest from energy companies. This has raised the necessity of developing specific engineering tools to design safely and accurately arctic-compliant offshore structures. The mooring system design of a turret-moored vessel in ice-infested waters is a clear example of such a key engineering tool. In the arctic region, a turret-moored vessel shall be designed to face many ice features: level ice, ice ridges or even icebergs. Regarding specifically level ice, a turret-moored vessel will tend to align her heading (to weather vane) with the ice sheet drift direction in order to decrease the mooring loads applied by this ice sheet. For a vessel already embedded in an ice sheet, a rapid change in the ice drift direction will suddenly increase the ice loads before the weathervaning occurs. This sudden increase in mooring loads may be a governing event for the turret-mooring system and should therefore be understood and simulated properly to ensure a safe design. The paper presents ADWICE (Advanced Weathervaning in ICE), an engineering tool dedicated to the calculation of the weathervaning of ship-shaped vessels in level ice. In ADWICE, the ice load formulation relies on the Croasdale model. Ice loads are calculated and applied to the vessel quasi-statically at each time step. The software also updates the hull waterline contour at each time step in order to calculate precisely the locations of contact between the hull and the ice sheet. Model tests of a turret-moored vessel have been performed in an ice basin. Validation of the simulated response is performed by comparison with model tests results in terms of weathervaning time, maximum mooring loads, and vessel motions.

Early Holocene ocean conditions off the Zachariæ Isstrøm, Northeast Greenland

2021 ◽  
Author(s):  
Joanna Davies ◽  
Anders Møller Mathiasen ◽  
Kristiane Kristensen ◽  
Christof Pearce ◽  
Marit-Solveig Seidenkrantz
Keyword(s):  
Climate Change ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Atlantic Water ◽  
The Arctic ◽  
Future Climate Change ◽  
Polar Regions ◽  
Ice Shelf ◽  
Outlet Glacier ◽  
The Impact

&lt;p&gt;The polar regions exhibit some of the most visible signs of climate change globally; annual mass loss from the Greenland Ice Sheet (GrIS) has quadrupled in recent decades, from 51 &amp;#177; 65 Gt yr&lt;sup&gt;&amp;#8722;1&lt;/sup&gt; (1992-2001) to 211 &amp;#177; 37 Gt yr&lt;sup&gt;&amp;#8722;1&lt;/sup&gt; (2002-2011). This can partly be attributed to the widespread retreat and speed-up of marine-terminating glaciers. The Zachariae Isstr&amp;#248;m (ZI) is an outlet glacier of the Northeast Greenland Ice Steam (NEGIS), one of the largest ice streams of the GrIS (700km), draining approximately 12% of the ice sheet interior. Observations show that the ZI began accelerating in 2000, resulting in the collapse of the floating ice shelf between 2002 and 2003. By 2014, the ice shelf extended over an area of 52km&lt;sup&gt;2&lt;/sup&gt;, a 95% decrease in area since 2002, where it extended over 1040km&lt;sup&gt;2&lt;/sup&gt;. Paleo-reconstructions provide an opportunity to extend observational records in order to understand the oceanic and climatic processes governing the position of the grounding zone of marine terminating glaciers and the extent of floating ice shelves. Such datasets are thus necessary if we are to constrain the impact of future climate change projections on the Arctic cryosphere.&lt;/p&gt;&lt;p&gt;A multi-proxy approach, involving grain size, geochemical, foraminiferal and sedimentary analysis was applied to marine sediment core DA17-NG-ST8-92G, collected offshore of the ZI, on &amp;#160;the Northeast Greenland Shelf. The aim was to reconstruct changes in the extent of the ZI and the palaeoceanographic conditions throughout the Early to Mid Holocene (c.a. 12,500-5,000 cal. yrs. BP). Evidence from the analysis of these datasets indicates that whilst there has been no grounded ice at the site over the last 12,500 years, the ice shelf of the ZI extended as a floating ice shelf over the site between 12,500 and 9,200 cal. yrs. BP, with the grounding line further inland from our study site. This was followed by a retreat in the ice shelf extent during the Holocene Thermal Maximum; this was likely to have been governed, in part, by basal melting driven by Atlantic Water (AW) recirculated from Svalbard or from the Arctic Ocean. Evidence from benthic foraminifera suggest that there was a shift from the dominance of AW to Polar Water at around 7,500 cal. yrs. BP, although the ice shelf did not expand again despite of this cooling of subsurface waters.&lt;/p&gt;

Natural variability and recent warming in central Greenland ice cores

2021 ◽  
Author(s):  
Maria Hoerhold ◽  
Thomas Münch ◽  
Stefanie Weißbach ◽  
Sepp Kipfstuhl ◽  
Bo Vinther ◽  
...  
Keyword(s):  
Climate Variability ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Natural Variability ◽  
The Arctic ◽  
Last Millennium ◽  
Recent Warming ◽  
Temperature Reconstructions ◽  
Firn Core

&lt;p&gt;Climate variability of the Arctic region has been investigated by means of temperature reconstructions based on proxies from various climate archives around the Arctic, compiled over the last 2000a in the so called Arctic2k record. However, the representativeness of the Arctic2k reconstruction for central Greenland remains unclear, since only a few ice cores have been included in the reconstruction, and observations from the Greenland Ice Sheet (GIC) report ambiguous warming trends for the end of the 20th and the beginning of the 21st century which are not displayed by Arctic2k. Today, the GIC experiences periods with temperatures close to or above the freezing point at high elevations, area-wide melting and mass loss. In order to assess the recent warming as signature of global climate change, records of past climate changes with appropriate temporal and spatial coverage can serve as a benchmark for naturally driven climate variability. Instrumental records for Greenland are short and geographically sparse, and existing temperature reconstructions from single ice cores are noisy, leading to an inconclusive assessment of the recent warming for Greenland.&lt;/p&gt;&lt;p&gt;Here, we provide a Greenland firn-core stack covering the time span of the last millennium until the first decade of the 21&lt;sup&gt;st &lt;/sup&gt;century in unprecedented quality by re-drilling as well as analyzing 16 existing firn core sites. We find a strong decadal to bi-decadal natural variability in the record, and, while the record exhibits several warming events with trends that show a similar amplitude as the recent one, we find that the recent absolute values of stable oxygen isotope composition are unprecedented for the last 1000 years.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Comparing our Greenland record with the Arctic 2k temperature reconstruction shows that the correlation between the two records changes throughout the last millennium. While in the periods of 1200-1300 and 1400-1650 CE the records correlate positively, between 1300 and 1400 and 1650-1700 CE shorter periods with negative correlation are found. Since then the correlation is characterized by alternation between positive and zero correlation, with a drop towards negative values at the end of the 20&lt;sup&gt;th&lt;/sup&gt; century. Including re-analysis data, we hypothesize that the climate on top of the GIC was decoupled from the surrounding Arctic for the last decades, leading to the observed mismatch in observations of warming trends.&lt;/p&gt;&lt;p&gt;We suggest that the recently observed Greenland temperatures are a superposition of a strong natural variability with an anthropogenic long-term trend. Our findings illustrate that global warming has reached the interior of the Greenland ice sheet, which will have implications for its surface mass balance and Greenland&amp;#8217;s future contribution to sea level rise.&lt;/p&gt;&lt;p&gt;Our record complements the Arctic 2k record to a profound view on the Arctic climate variability, where regional compilations may not be representative for specific areas.&lt;/p&gt;

scholarly journals Diversity of Arctic pelagic <i>Bacteria</i> with an emphasis on photoheterotrophs: a review

2014 ◽  
Vol 11 (12) ◽  
pp. 3309-3322 ◽  
Author(s):  
D. Boeuf ◽  
F. Humily ◽  
C. Jeanthon
Keyword(s):  
Arctic Ocean ◽  
Heterotrophic Bacteria ◽  
Euphotic Zone ◽  
The Arctic ◽  
Major Influence ◽  
Distinctive Features ◽  
Ice Melt ◽  
Energy Needs ◽  
Continental Shelves ◽  
The Arctic Ocean

Abstract. The Arctic Ocean is a unique marine environment with respect to seasonality of light, temperature, perennial ice cover, and strong stratification. Other important distinctive features are the influence of extensive continental shelves and its interactions with Atlantic and Pacific water masses and freshwater from sea ice melt and rivers. These characteristics have major influence on the biological and biogeochemical processes occurring in this complex natural system. Heterotrophic bacteria are crucial components of marine food webs and have key roles in controlling carbon fluxes in the oceans. Although it was previously thought that these organisms relied on the organic carbon in seawater for all of their energy needs, several recent discoveries now suggest that pelagic bacteria can depart from a strictly heterotrophic lifestyle by obtaining energy through unconventional mechanisms that are linked to the penetration of sunlight into surface waters. These photoheterotrophic mechanisms may play a significant role in the energy budget in the euphotic zone of marine environments. Modifications of light and carbon availability triggered by climate change may favor the photoheterotrophic lifestyle. Here we review advances in our knowledge of the diversity of marine photoheterotrophic bacteria and discuss their significance in the Arctic Ocean gained in the framework of the Malina cruise.

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