Rapid Ice Melt Research Articles

Warm‐air advection, air mass transformation and fog causes rapid ice melt

AbstractDirect observations during intense warm‐air advection over the East Siberian Sea reveal a period of rapid sea‐ice melt. A semistationary, high‐pressure system north of the Bering Strait forced northward advection of warm, moist air from the continent. Air‐mass transformation over melting sea ice formed a strong, surface‐based temperature inversion in which dense fog formed. This induced a positive net longwave radiation at the surface while reducing net solar radiation only marginally; the inversion also resulted in downward turbulent heat flux. The sum of these processes enhanced the surface energy flux by an average of ~15 W m−2 for a week. Satellite images before and after the episode show sea‐ice concentrations decreasing from > 90% to ~50% over a large area affected by the air‐mass transformation. We argue that this rapid melt was triggered by the increased heat flux from the atmosphere due to the warm‐air advection.

Evolution and outburst risk analysis of moraine-dammed lakes in the central Chinese Himalaya

The recent evolution and outburst risk of two typical moraine-dammed lakes, Galong and Gangxi, central Chinese Himalaya, are analyzed using topographic maps from 1974 and Landsat satellite imagery acquired in 1988, 2000 and 2014. The datasets show the areas of Galong and Gangxi lakes increasing at rates of 0.45 and 0.34 km2/year during the period 1974–2014, an expansion of 501% and 107%, respectively, in the past 41 years, while the areas of the parent glaciers, Reqiang and Jipucong decreased by 44.22% and 37.76%, respectively. The accelerating retreat of the glaciers not only reflects their generally negative mass balance but is consistent with the rapid expansion of the moraine-dammed lakes. When acted upon by external forces such as earthquakes, heavy rainfall, rapid melting of glaciers and dead ice, and snow/ice/rock avalanches, these lakes can become extremely dangerous, easily forming outburst mudslides, which can potentially spread to the Poiqu river basin and develop into cross-border (China and Nepal) GLOF disasters. Therefore, there is an urgent need to strengthen integrated risk management of glacial lake outburst disasters with multiple objectives and modes.

The club within the club: the challenge of a soft law framework in a global Arctic context

Challenges to Arctic governance presented by rapid ice melt are assessed in light of structural problems facing the Arctic Council, the region’s “preeminent” soft law regime structure. This paper argues the territorializing temptations of the sub-regional Arctic 5 coastal states, which among themselves may overlap and conflict, nevertheless align to keep the Arctic Council focus on functional objectives, notwithstanding attempts at internal reform, calls for a new Arctic treaty, and emerging assessments of a global understanding of Arctic issues, as represented by the newly founded Arctic Circle Assembly. Various jurisdictional designs in the Arctic Ocean, including extended continental shelf delimitations, combine to preference Arctic 5 interests over revisions to the soft law and functional orientation of the current Arctic regime structure.

A Pathway Connecting the Monsoonal Heating to the Rapid Arctic Ice Melt*

AbstractThis study provides a monsoonal link to the rapid Arctic ice melt. Each year the planetary-scale African–Asian monsoonal outflow near the tropopause carries a large anticyclonic gyre that has a longitudinal spread that occupies nearly half of the entire tropics. In recent years, the South Asian summer monsoon has experienced increased rainfall over northwestern India and Pakistan and it has also contributed to more intense local anticyclonic outflows from this region. The western lobes of these intense upper-high-pressure areas carry outflows with large heat fluxes from the monsoon belt toward central Asia and eventually to the region of the rapid ice melt of the Canadian Arctic. In this study this spectacular pathway has been defined from airflow trajectories, heat content, and heat flux anomalies. Most of these show slow increasing trends in the last 20 years. The monsoonal connection to the rapid Arctic ice melt is a new contribution of this study. This is shown from the passage of a vertical column of large positive values of the heat content anomaly that can be traced from the Asian monsoon belt to the Canadian Arctic. The heat flux along these episodic and intermittently active pathways is shown to be considerably larger than the atmospheric poleward flux across latitude circles and from the oceans. This study contrasts these thermodynamic wave trains (defining this pathway) for the more conventional dynamic wave trains.

The influence of ground ice distribution on geomorphic dynamics since the Little Ice Age in proglacial areas of two cirque glacier systems

AbstractHolocene glaciers have contributed to an abundance of unstable sediments in mountainous environments. In permafrost environments, these sediments can contain ground ice and are subject to rapid geomorphic activity and evolution under condition of a warming climate. To understand the influence of ground ice distribution on this activity since the Little Ice Age (LIA), we have investigated the Pierre Ronde and Rognes proglacial areas, two cirque glacier systems located in the periglacial belt of the Mont Blanc massif. For the first time, electrical resistivity tomography, temperature data loggers and differential global positioning systems (dGPS) are combined with historical documents and glaciological data analysis to produce a complete study of evolution in time and space of these small landsystems since the LIA. This approach allows to explain spatial heterogeneity of current internal structure and dynamics. The studied sites are a complex assemblage of debris‐covered glacier, ice‐rich frozen debris and unfrozen debris. Ground ice distribution is related to former glacier thermal regime, isolating effect of debris cover, water supply to specific zones, and topography. In relation with this internal structure, present dynamics are dominated by rapid ice melt in the debris‐covered upper slopes, slow creep processes in marginal glacigenic rock glaciers, and weak, superficial reworking in deglaciated moraines. Since the LIA, geomorphic activity is mainly spatially restricted within the proglacial areas. Sediment exportation has occurred in a limited part of the former Rognes Glacier and through water pocket outburst flood and debris flows in Pierre Ronde. Both sites contributed little sediment supply to the downslope geomorphic system, rather by episodic events than by constant supply. In that way, during Holocene and even in a paraglacial context as the recent deglaciation, proglacial areas of cirque glaciers act mostly as sediment sinks, when active geomorphic processes are unable to evacuate sediment downslope, especially because of the slope angle weakness. Copyright © 2014 John Wiley & Sons, Ltd.

Evaluation of the CFSv2 CMIP5 decadal predictions

Retrospective decadal forecasts were undertaken using the Climate Forecast System version 2 (CFSv2) as part of Coupled Model Intercomparison Project 5. Decadal forecasts were performed separately by the National Center for Environmental Prediction (NCEP) and by the Center for Ocean-Land-Atmosphere Studies (COLA), with the centers using two different analyses for the ocean initial conditions the NCEP Climate Forecast System Reanalysis (CFSR) and the NEMOVAR-COMBINE analysis. COLA also examined the sensitivity to the inclusion of forcing by specified volcanic aerosols. Biases in the CFSv2 for both sets of initial conditions include cold midlatitude sea surface temperatures, and rapid melting of sea ice associated with warm polar oceans. Forecasts from the NEMOVAR-COMBINE analysis showed strong weakening of the Atlantic Meridional Overturning Circulation (AMOC), eventually approaching the weaker AMOC associated with CFSR. The decadal forecasts showed high predictive skill over the Indian, the western Pacific, and the Atlantic Oceans and low skill over the central and eastern Pacific. The volcanic forcing shows only small regional differences in predictability of surface temperature at 2m (T2m) in comparison to forecasts without volcanic forcing, especially over the Indian Ocean. An ocean heat content (OHC) budget analysis showed that the OHC has substantial memory, indicating potential for the decadal predictability of T2m; however, the model has a systematic drift in global mean OHC. The results suggest that the reduction of model biases may be the most productive path towards improving the model’s decadal forecasts.

Winter sea ice melting in the Atlantic Water subduction area, Svalbard Norway

AbstractHerein, we study a small area along the shelf west of Spitsbergen, near Prins Karls Forland, where warm, saline Atlantic Water of the West Spitsbergen Current currently first encounters sea ice. This sea ice is drifting in a coastal current that carries Arctic Water originating from the Barents Sea northward over the shelf. Our aim was to investigate whether melting of sea ice by Atlantic Water in this area might be a significant factor that could contribute to the formation of a cold halocline layer that isolates the sea ice from further melting from below. Observations of temperature and salinity profiles were collected during two winters, via CTD‐SRDL instruments deployed on harbor seals (Phoca vitulina), and fed into a heat and freshwater budget box model in order to quantify the importance of melting relative to other processes that could transform the shelf water mass during winter. Cross‐frontal exchange of Atlantic Water from the West Spitsbergen Current, driven by buoyancy forcing rather than Ekman upwelling, was determined to be the source of the heat that melted drift ice on the shelf. Some local sea ice formation did take place, but its importance in the total heat and freshwater budgets appeared to be minor. The data suggest that the production of a cold halocline layer was preceded by southerly winds and rapid drift ice melting.

Pink marine sediments reveal rapid ice melt and Arctic meltwater discharge during Dansgaard–Oeschger warmings

The climate of the last glaciation was interrupted by numerous abrupt temperature fluctuations, referred to as Greenland interstadials and stadials. During warm interstadials the meridional overturning circulation was active transferring heat to the north, whereas during cold stadials the Nordic Seas were ice-covered and the overturning circulation was disrupted. Meltwater discharge, from ice sheets surrounding the Nordic Seas, is implicated as a cause of this ocean instability, yet very little is known regarding this proposed discharge during warmings. Here we show that, during warmings, pink clay from Devonian Red Beds is transported in suspension by meltwater from the surrounding ice sheet and replaces the greenish silt that is normally deposited on the north-western slope of Svalbard during interstadials. The magnitude of the outpourings is comparable to the size of the outbursts during the deglaciation. Decreasing concentrations of ice-rafted debris during the interstadials signify that the ice sheet retreats as the meltwater production increases.

Rapid ice melting drives Earth's pole to the east

Space geodetic observations of polar motion show that around 2005, the average annual pole position began drifting toward the east, an abrupt departure from the drift direction seen over the past century. Satellite gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) show that about 90% of this change is due to accelerated melting of polar ice sheets and mountain glaciers and related sea level rise. The close relationship between long‐term polar motion and climate‐related mass redistribution established using GRACE data indicates that accurately measured polar motion data offer an additional tool for monitoring global‐scale ice melting and sea level rise and should be useful in bridging the anticipated gap between GRACE and follow‐on satellite gravity missions.

Milankovitch tuning of deep-sea records: Implications for maximum rates of change of sea level

The analysis of several stacked and tuned records from the deep-sea floor yields two rather different sets of values for rates of sea-level rise. One of these reflects “regular” growth and decay and the other represents rapid decay of polar ice. Typical rise rates during rapid decay are near 1.2 m per century; with higher values seemingly following an abundance distribution that may be described by a standard deviation of 0.4 m per century (one third of the typical value). Distributions are based on a millennium resolution, leaving room for higher values for selected centuries within any millennium. Nevertheless, rise values beyond 5 m per century seem highly unusual. The quality of the match between deep-sea record (taken as differential) and Milankovitch forcing is excellent for the last 400,000 years (that is, the time since the “mid-Brunhes Event,” a period that may be referred to as the “Emiliani Chron”) but is poor in certain time spans before that. Difficulties associated with precise dating and a changing level of instability of polar ice prevent identification of trigger events for deglaciation. What is observable is that during periods of rapid decay, once sea level started to rise, it kept doing so for millennia (presumably till suitable ice masses were used up). Thus, it seems that a rise of sea level is itself a positive feedback on rapid melting of ice. Negative feedback, if real (as assumed in certain hypotheses about the origin of the Younger Dryas) is an unexpected exception that presumably relies on a high threshold value of sea-level rise.

Mid-Pacific microatolls record sea-level stability over the past 5000 yr

There has been geographical variation in sea level since rapid postglacial melting of polar ice ceased similar to 6 k.y. ago, reflecting isostatic adjustments of Earth and ocean surfaces to past (and ongoing) redistribution of ice and water loads. A new data set of over 100 fossil microatolls from Christmas (Kiritimati) Island provides a Holocene sea-level record of unparalleled continuity. Living reef-flat corals grow up to a low-tide level. Adjacent fossil microatolls, long-lived Porites corals up to several meters in diameter, occur at similar elevations (±0.1 m), and extensive fossil microatolls in the island interior are at consistent elevations within each population. Collectively, they comprise an almost continuous sequence spanning the past 5 k.y., indicating that, locally, sea level has been within 0.25 m of its present position, and precluding global sea-level oscillations of one or more meters inferred from less stable locations, or using other sea-level indicators. This mid-Pacific atoll is tectonically stable and far from former ice sheets. The precisely surveyed and radiometrically dated microatolls indicate that sea level has not experienced significant oscillations, in accordance with geophysical modeling, which implies that the eustatic contribution from past ice melt and the isostatic adjustment of the ocean floor to loading largely cancel each other at this site.

Material Talk: The Arctic Continental Shelf in the Law of the Sea Convention Discussion of the United States

Abstract The legal status of a large area of the Arctic seafloor is currently being redefined as the rapid melting of polar ice is enabling the exploitation and study of resource-rich underwater areas. The United Nations Convention on the Law of the Sea contains legal rules for establishing exploitation rights to the newly accessible seafloor. The United States has not joined the Law of the Sea Convention but may be legally entitled to areas of the Arctic seafloor, which has caused an upsurge of political discussion among U.S. political elites. In this article, I examine the process by which Arctic seafloor and ice come to influence policy discussion in the United States. I highlight the way in which material policy influence can be treated as historical rather than monocausal by using new materialist theory.

Rising sea level may cause decline of fringing coral reefs

Coral reefs are major marine ecosystems and critical resources for marine diversity and fisheries. These ecosystems are widely recognized to be at risk from a number of stressors, and added to those in the past several decades is climate change due to anthropogenically driven increases in atmospheric concentrations of greenhouse gases. Most threatening to most coral reefs are elevated sea surface temperatures and increased ocean acidity [e.g., Kleypas et al., 1999; Hoegh‐Guldberg et al., 2007], but sea level rise, another consequence of climate change, is also likely to increase sedimentary processes that potentially interfere with photosynthesis, feeding, recruitment, and other key physiological processes (Figure 1). Anderson et al. [2010] argue compellingly that potential hazardous impacts to coastlines from 21st‐century sea level rise are greatly underestimated, particularly because of the rapid rate of rise. The Intergovernmental Panel on Climate Change estimates that sea level will rise in the coming century (1990–2090) by 2.2–4.4 millimeters per year, when projected with little contribution from melting ice [Meehl et al., 2007]. New studies indicate that rapid melting of land ice could substantially increase the rate of sea level rise [Grinsted et al., 2009; Milne et al., 2009].

Developing coastal adaptation to climate change in the New York City infrastructure-shed: process, approach, tools, and strategies

While current rates of sea level rise and associated coastal flooding in the New York City region appear to be manageable by stakeholders responsible for communications, energy, transportation, and water infrastructure, projections for sea level rise and associated flooding in the future, especially those associated with rapid icemelt of the Greenland and West Antarctic Icesheets, may be outside the range of current capacity because extreme events might cause flooding beyond today’s planning and preparedness regimes. This paper describes the comprehensive process, approach, and tools for adaptation developed by the New York City Panel on Climate Change (NPCC) in conjunction with the region’s stakeholders who manage its critical infrastructure, much of which lies near the coast. It presents the adaptation framework and the sea-level rise and storm projections related to coastal risks developed through the stakeholder process. Climate change adaptation planning in New York City is characterized by a multi-jurisdictional stakeholder–scientist process, state-of-the-art scientific projections and mapping, and development of adaptation strategies based on a risk-management approach.

Thermohaline water structure on the southwestern Chukchi Sea shelf under conditions of opposite regimes of atmospheric circulation in summer periods of 2003 and 2007

The results of two oceanographic surveys, carried out by TINRO-Center in August 2003 and 2007 in the southwestern part of the Chukchi Sea under conditions of opposite regimes of atmospheric circulation in the Eastern Arctic, are given. A stationary anticyclone with the center over the Beaufort Sea in 2007 favored the transport of warm air masses to the Arctic basin and more rapid ice melting. The surface layer temperature to the east of Wrangel Island reached 12°C (6–8°C above the normal). The upwelling of bottom waters was registered in the coastal zone due to the southeastern winds, the Siberian coastal current was not observed. In summer 2003, on the contrary, the cyclonic circulation type prevailed over the eastern seas of the Arctic, the northwestern winds in the coastal zone favored the spreading of the Siberian coastal current almost up to Bering Strait, the water temperature was 2–3°C below normal. The coastal thermal front was formed in both situations: in the first case, due to upwelling, in the second case, due to the spreading of cold coastal desalinated East Siberian waters.

Lacustrine evidence of early-Holocene environmental change in northern Iceland: a multiproxy palaeoecology and stable isotope study

Early-Holocene warming in Iceland caused rapid glacial ice melt which led to exposed landscapes on which soils developed and floras quickly established. Our chironomid-based records from northern Iceland suggest temperatures were up to 2—2.5°C warmer than present throughout the first two millennia post deglaciation (~10 500 to 8500 cal. BP) while sedimentary and isotopic data indicate the development of soils within the local environment throughout this period before catchment conditions started to stabilise around 8400 cal. BP. The warming trend over this period was not uniform however, but punctuated by a series of relatively short-lived climatic events. Specifically inwash events are suggested by the δ13Corganic, %TOC and C/N data around 9600 cal. BP and 8250 cal. BP and are seen at two independent sites. There is also evidence from the δ18Ocarbonate and δ13Ccarbonate records which suggests that progressive evaporation of the study lakes occurred from ~8200 cal. BP, the timing of which accords well with other isotopic records of drier conditions from around the North Atlantic.

Long-term experimental warming reduces soil nematode populations in the McMurdo Dry Valleys, Antarctica

Climate models predict significant future warming in polar regions. In the McMurdo Dry Valleys, Antarctica, projected summer climate warming is expected to increase snow and glacial melt, resulting in higher stream discharge, rising lake levels, and an increase in areas of moist soil, but the potential influence of warming and associated changes in hydrology on the soil ecosystem is poorly understood. To examine the effects of soil warming and changes in the availability of liquid water on populations of soil invertebrates and their habitat, we established a full-factorial warming and water addition experiment at one experimental site in each of the three hydrologic basins of Taylor Valley, Antarctica, and measured responses over 8 years. We hypothesized that an increase in temperature and moisture together would enhance habitat suitability for soil invertebrates thereby increasing abundance, biomass and diversity of the soil animal communities. Instead, warming treatments had an overall negative effect on density and body size of the microbial-feeding nematode Scottnema lindsayae, the dominant animal in the dry valleys, which decreased by 42% in warmed plots. While experimental moisture additions as a single annual pulse had no effect on nematodes, the surface flooding of one site from rapid melting of upslope subsurface ice (the result of an unusual natural warming event) drastically altered soil moisture, salinity, and animal communities; mortality of S. lindsayae increased and densities decreased. This extreme soil wetting event also resulted in an increase in chlorophyll a and populations of Eudorylaimus spp, a nematode species that prefers moist to wet habitats and feeds on soil micro-algae. Our results suggest that warming in the dry valleys could significantly affect soil nematode populations and species composition both directly and indirectly by altering species-specific habitat suitability for soil biota.

Isotopic-heterogeneity of the Thjorsa lava—Implications for mantle sources and crustal processes within the Eastern Rift Zone, Iceland

The Thjorsa lava in South Iceland is an early Holocene fissure lava within the Bardarbunga volcanic system—the most productive segment of the Eastern Rift Zone during the Quaternary and Holocene. The lava has a volume of 25 km 3 and is one of notably plagioclase-porphyritic early Holocene lava flows in Iceland. The possible genetic relationship between the large plagioclase phenocrysts and the host lava is investigated by analyzing carefully separated groundmass/plagioclase pairs. The groundmass was analyzed for major and trace elements and isotopic ratios of Sr, Nd and Pb. The large plagioclases were analyzed by microprobe and 87Sr/ 86Sr by mass spectrometry. The groundmass (host magma) of the host lava has a restricted range of elemental and isotopic composition. Both the groundmass and the separated plagioclases show a significant range of 87Sr/ 86Sr—but interestingly with only minor overlap between the two groups. Both are, however, within the range of values observed for the lavas of the Bardarbunga volcanic system. This lack of overlap suggests that the plagioclase and the host lava are genetically unrelated and derived from two distinct mantle sources. The suggested source for the large plagioclases is deep layered crustal gabbros formed in earlier intrusive events. The plagioclases are accompanied by minor amounts of Fo-rich olivine and occasional disintegrating Cr-diopside. There is a clear compositional gap between the An-rich (> An 80) plagioclases and the small groundmass plagioclase that appear to be in equilibrium with the groundmass composition. The parental magma of the anorthositic gabbro must have been relatively primitive, crystallizing additional olivine and Cr-diopside and with 87Sr/ 86Sr at the low end of the range observed in the Bardarbunga rift segment. During ascent of the host magma the gabbros were infiltrated and broken up by this more evolved host magma. With lowered pressures during ascent and lava effusion the Cr-diopside comes unstable with up to 5% being assimilated into the host magma mildly affecting isotopic ratios and those elements with clinopyroxene affinity. The two components—the host magma and the plagioclases are therefore genetically unrelated and with only minor mixing effect on the host magma. The results of the present study show that whole-rock chemical analyses of such rocks must be treated with caution as they may not represent actual magmatic liquids. At the beginning of the Holocene there was a large isostatic rebound in Iceland following the rapid ice melting. This was accompanied by a major pulse of basaltic eruptions and many of these eruptions, especially around Central Iceland, carry abundant large plagioclases. This is clearly not the only cause as there are a number of very plagioclase-porphyritic lavas in the Tertiary formations but may have facilitated plagioclase incorporation.

Spectral analysis of seismic noise induced by rivers: A new tool to monitor spatiotemporal changes in stream hydrodynamics

Analysis of continuous seismic data recorded by a dense passive seismological network (Hi‐CLIMB) installed across the Himalayas reveals strong spatial and temporal variations in the ambient seismic energy produced at high frequencies (>1 Hz). From June to September 2003, the high‐frequency seismic noise is observed to increase up to 20 dB (relative to (m/s)2/Hz) for all the stations located along a steep 30‐km‐long narrow and deeply incised channel of the Trisuli River, a major trans‐Himalayan river. The early summer increase in high‐frequency energy is modulated by a 24‐h periodicity where the minimum of seismic noise level is reached around noon and the maximum is reached late in the evening. A detailed study of seismic noise amplitude reveals a clear correlation with both regional meteorological and hydrological data along the Trisuli River. Seasonal increase in ambient noise coincides with the strong monsoon rainfall and a period of rapid melting of snow and ice in the high elevations. The observed 24‐h cyclicity is consistent with the daily fluctuation of the precipitation and river discharge in the region. River‐induced seismic noise is partly generated by stream turbulence, but this mechanism fails to explain the observed clockwise hysteresis of seismic noise amplitude versus water level. This pattern is better explained if a significant part of the observed seismic noise is caused by ground vibrations generated by bed load transport. This points out the potential of using background seismic noise to quantify in continuous river bed load and monitor its spatial variations, which remain difficult with classical approaches.

A “triple sea‐ice state” mechanism for the abrupt warming and synchronous ice sheet collapses during Heinrich events

Abrupt, switch‐like, changes in sea ice cover are proposed as a mechanism for the large‐amplitude abrupt warming that seemed to have occurred after each Heinrich event. Sea ice changes are also used to explain the colder‐than‐ambient glacial conditions around the time of the glacier discharge. The abrupt warming events occur in this mechanism, owing to rapid sea ice melting which warmed the atmosphere via the strong sea ice albedo and insulating feedbacks. Such abrupt sea ice changes can also account for the warming observed during Dansgaard‐Oeschger events. The sea ice changes are caused by a weak (order of 5 Sv) response of the thermohaline circulation (THC) to glacier discharges. The main point of this work is therefore that sea ice may be thought of as a very effective amplifier of a weak THC variability, explaining the abrupt temperature changes over Greenland. Synchronous ice sheet collapses from different ice sheets around the North Atlantic, indicated by some proxy records, are shown to be possible via the weak coupling between the different ice sheets by the atmospheric temperature changes caused by the sea ice changes. This weak coupling can lead to a “nonlinear phase locking” of the different ice sheets which therefore discharge synchronously. It is shown that the phase locking may also lead to “precursor” glacier discharge events from smaller ice sheets before the Laurentide Ice Sheet discharges. The precursor events in this mechanism are the result rather than the cause of the major glacier discharges from the Laurentide Ice Sheet.