scholarly journals Fluctuations of a Greenlandic tidewater glacier driven by changes in atmospheric forcing: observations and modelling of Kangiata Nunaata Sermia, 1859–present

2014 ◽  
Vol 8 (6) ◽  
pp. 2031-2045 ◽  
Author(s):  
J. M. Lea ◽  
D. W. F. Mair ◽  
F. M. Nick ◽  
B. R. Rea ◽  
D. van As ◽  
...  
Keyword(s):  
Numerical Models ◽  
Atmospheric Temperature ◽  
Ice Age ◽  
Band Model ◽  
Glacier Change ◽  
Atmospheric Forcing ◽  
Climate Anomalies ◽  
Tidewater Glacier ◽  
Primary Driver ◽  
Oceanic Forcing

Abstract. Many tidewater glaciers in Greenland are known to have undergone significant retreat during the last century following their Little Ice Age maxima. Where it is possible to reconstruct glacier change over this period, they provide excellent records for comparison to climate records, as well as calibration/validation for numerical models. These glacier change records therefore allow for tests of numerical models that seek to simulate tidewater glacier behaviour over multi-decadal to centennial timescales. Here we present a detailed record of behaviour from Kangiata Nunaata Sermia (KNS), SW Greenland, between 1859 and 2012, and compare it against available oceanographic and atmospheric temperature data between 1871 and 2012. We also use these records to evaluate the ability of a well-established one-dimensional flow-band model to replicate behaviour for the observation period. The record of terminus change demonstrates that KNS has advanced/retreated in phase with atmosphere and ocean climate anomalies averaged over multi-annual to decadal timescales. Results from an ensemble of model runs demonstrate that observed dynamics can be replicated. Model runs that provide a reasonable match to observations always require a significant atmospheric forcing component, but do not necessarily require an oceanic forcing component. Although the importance of oceanic forcing cannot be discounted, these results demonstrate that changes in atmospheric forcing are likely to be a primary driver of the terminus fluctuations of KNS from 1859 to 2012. We propose that the detail and length of the record presented makes KNS an ideal site for model validation exercises investigating links between climate, calving rates, and tidewater glacier dynamics.

scholarly journals Fluctuations of a Greenlandic tidewater glacier driven by changes in atmospheric forcing: observations and modelling of Kangiata Nunaata Sermia, 1859–present

2014 ◽  
Vol 8 (2) ◽  
pp. 2005-2041
Author(s):  
J. M. Lea ◽  
D. W. F. Mair ◽  
F. M. Nick ◽  
B. R. Rea ◽  
D. van As ◽  
...  
Keyword(s):  
Numerical Models ◽  
Atmospheric Temperature ◽  
Ice Age ◽  
Band Model ◽  
Atmospheric Forcing ◽  
Tidewater Glaciers ◽  
Climate Anomalies ◽  
Tidewater Glacier ◽  
Primary Driver ◽  
Oceanic Forcing

Abstract. Many tidewater glaciers in Greenland are known to have undergone significant retreat during the last century following their Little Ice Age maxima. Where it is possible to reconstruct glacier change over this period, they provide excellent records for comparison to climate records, and calibration/validation for numerical models. These records therefore allow tests of numerical models that seek to simulate tidewater glacier behaviour over multi-decadal to centennial timescales. Here we present a detailed record of behaviour from Kangiata Nunaata Sermia (KNS), SW Greenland, between 1859–2012 and compare it against available oceanographic and atmospheric temperature variability between 1871–2012. We also use these records to evaluate the ability of a well-established one-dimensional flow-band model to replicate behaviour for the observation period. The record of terminus change demonstrates that KNS has advanced/retreated in phase with atmosphere and ocean climate anomalies averaged over multi-annual to decadal timescales. Results from an ensemble of model runs demonstrate that observed dynamics can be replicated, with changes in atmospheric forcing not needing to be offset by changes in oceanic forcing sensitivity. Furthermore, successful runs always require a significant atmospheric forcing component, while an oceanic forcing component is not always needed. Although the importance of oceanic forcing cannot be discounted, these results demonstrate that changes in atmospheric forcing are likely to be a primary driver of the terminus fluctuations of KNS from 1859–2012.

scholarly journals Post-LIA glacier changes along a latitudinal transect in the Central Italian Alps

2014 ◽  
Vol 8 (6) ◽  
pp. 2235-2252 ◽  
Author(s):  
R. Scotti ◽  
F. Brardinoni ◽  
G. B. Crosta
Keyword(s):  
Atmospheric Temperature ◽  
Winter Precipitation ◽  
Ice Age ◽  
Glacier Change ◽  
Mass Balances ◽  
Italian Alps ◽  
Temperature Trends ◽  
Continental Divide ◽  
Latitudinal Transect ◽  
Order Of Magnitude

Abstract. The variability of glacier response to atmospheric temperature rise in different topo-climatic settings is still a matter of debate. To address this question in the Central Italian Alps, we compile a post-LIA (Little Ice Age) multitemporal glacier inventory (1860–1954–1990–2003–2007) along a latitudinal transect that originates north of the continental divide in the Livigno Mountains and extends south through the Disgrazia and Orobie ranges, encompassing continental-to-maritime climatic settings. In these sub-regions, we examine the area change of 111 glaciers. Overall, the total glacierized area has declined from 34.1 to 10.1 km2, with a substantial increase in the number of small glaciers due to fragmentation. The average annual decrease (AAD) in glacier area has risen by about 1 order of magnitude from 1860–1990 (Livigno: 0.45; Orobie: 0.42; and Disgrazia: 0.39 % a−1) to 1990–2007 (Livigno: 3.08; Orobie: 2.44; and Disgrazia: 2.27 % a−1). This ranking changes when considering glaciers smaller than 0.5 km2 only (i.e., we remove the confounding caused by large glaciers in Disgrazia), so that post-1990 AAD follows the latitudinal gradient and Orobie glaciers stand out (Livigno: 4.07; Disgrazia: 3.57; and Orobie: 2.47 % a−1). More recent (2007–2013) field-based mass balances in three selected small glaciers confirm post-1990 trends showing the consistently highest retreat in continental Livigno and minimal area loss in maritime Orobie, with Disgrazia displaying transitional behavior. We argue that the recent resilience of glaciers in Orobie is a consequence of their decoupling from synoptic atmospheric temperature trends, a decoupling that arises from the combination of local topographic configuration (i.e., deep, north-facing cirques) and high winter precipitation, which ensures high snow-avalanche supply, as well as high summer shading and sheltering. Our hypothesis is further supported by the lack of correlations between glacier change and glacier attributes in Orobie, as well as by the higher variability in ELA,sub>0 positioning, post-LIA glacier change, and interannual mass balances, as we move southward along the transect.

scholarly journals Post-LIA glacier changes along a latitudinal transect in the Central Italian Alps

2014 ◽  
Vol 8 (4) ◽  
pp. 4075-4126 ◽  
Author(s):  
R. Scotti ◽  
F. Brardinoni ◽  
G. B. Crosta
Keyword(s):  
Atmospheric Temperature ◽  
Winter Precipitation ◽  
Ice Age ◽  
Glacier Change ◽  
Mass Balances ◽  
Italian Alps ◽  
Temperature Trends ◽  
Continental Divide ◽  
Latitudinal Transect ◽  
Order Of Magnitude

Abstract. The variability of glacier response to atmospheric temperature rise in different topo-climatic settings is still matter of debate. To address this question in the Central Italian Alps we compile a post-LIA (Little Ice Age) multitemporal glacier inventory (1860-1954-1990-2003-2007) along a latitudinal transect that originates north of the continental divide in the Livigno mountains, and extends south through the Disgrazia and Orobie ranges, encompassing continental-to-maritime climatic settings. In these sub-regions we examine area change of 111 glaciers. Overall, total glacierized area has declined from 34.1 to 10.1 km2, with a substantial increase in the number of small glaciers due to fragmentation. Average annual decrease (AAD) in glacier area has risen of about an order of magnitude from 1860–1990 (Livigno: 0.45; Orobie: 0.42; and Disgrazia: 0.39 % a−1) to 1990–2007 (Livigno: 3.08; Orobie: 2.44; and Disgrazia: 2.27 % a−1). This ranking changes when considering glaciers <0.5 km2 only (i.e., we remove the confounding caused by large glaciers in Disgrazia), so that post-1990 AAD follows the latitudinal gradient and Orobie glaciers stand out (Livigno: 4.07; Disgrazia: 3.57; and Orobie: 2.47 % a−1). More recent (2007–2013) field-based mass balances in three selected small glaciers confirm post-1990 trends showing consistent highest retreat in continental Livigno and minimal area loss in maritime Orobie, with Disgrazia displaying a transitional behaviour. We argue that the recent resilience of glaciers in Orobie is a consequence of their decoupling from synoptic atmospheric temperature trends. A decoupling that arises from the combination of local topographic configuration (i.e., deep, north-facing cirques) and high winter precipitation, which ensures high snow-avalanche supply, as well as high summer shading and sheltering. Our hypothesis is further supported by the lack of correlations between glacier change and glacier attributes in Orobie, as well by the higher variability in ELA0 positioning, post-LIA glacier change, and inter-annual mass balances, as we move southward along the transect.

scholarly journals Atmospheric forcing of rapid marine-terminating glacier retreat in the Canadian Arctic Archipelago

2019 ◽  
Vol 5 (3) ◽  
pp. eaau8507 ◽  
Author(s):  
Alison J. Cook ◽  
Luke Copland ◽  
Brice P. Y. Noël ◽  
Chris R. Stokes ◽  
Michael J. Bentley ◽  
...  
Keyword(s):  
Canadian Arctic ◽  
Atmospheric Temperature ◽  
Climate System ◽  
Glacier Retreat ◽  
Relative Influence ◽  
Canadian Arctic Archipelago ◽  
Atmospheric Forcing ◽  
Ocean Climate ◽  
Subsurface Ocean ◽  
Primary Driver

The Canadian Arctic Archipelago contains >300 glaciers that terminate in the ocean, but little is known about changes in their frontal positions in response to recent changes in the ocean-climate system. Here, we examine changes in glacier frontal positions since the 1950s and investigate the relative influence of oceanic temperature versus atmospheric temperature. Over 94% of glaciers retreated between 1958 and 2015, with a region-wide trend of gradual retreat before ~2000, followed by a fivefold increase in retreat rates up to 2015. Retreat patterns show no correlation with changes in subsurface ocean temperatures, in clear contrast to the dominance of ocean forcing in western Greenland and elsewhere. Rather, significant correlations with surface melt indicate that increased atmospheric temperature has been the primary driver of the acceleration in marine-terminating glacier frontal retreat in this region.

scholarly journals The sensitivity of the Greenland Ice Sheet to glacial–interglacial oceanic forcing

2018 ◽  
Vol 14 (4) ◽  
pp. 455-472 ◽  
Author(s):  
Ilaria Tabone ◽  
Javier Blasco ◽  
Alexander Robinson ◽  
Jorge Alvarez-Solas ◽  
Marisa Montoya
Keyword(s):  
Sea Level ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
High Sensitivity ◽  
Glacial Cycles ◽  
The Past ◽  
Primary Driver ◽  
Oceanic Forcing ◽  
Atmospheric Variations

Abstract. Observations suggest that during the last decades the Greenland Ice Sheet (GrIS) has experienced a gradually accelerating mass loss, in part due to the observed speed-up of several of Greenland's marine-terminating glaciers. Recent studies directly attribute this to warming North Atlantic temperatures, which have triggered melting of the outlet glaciers of the GrIS, grounding-line retreat and enhanced ice discharge into the ocean, contributing to an acceleration of sea-level rise. Reconstructions suggest that the influence of the ocean has been of primary importance in the past as well. This was the case not only in interglacial periods, when warmer climates led to a rapid retreat of the GrIS to land above sea level, but also in glacial periods, when the GrIS expanded as far as the continental shelf break and was thus more directly exposed to oceanic changes. However, the GrIS response to palaeo-oceanic variations has yet to be investigated in detail from a mechanistic modelling perspective. In this work, the evolution of the GrIS over the past two glacial cycles is studied using a three-dimensional hybrid ice-sheet–shelf model. We assess the effect of the variation of oceanic temperatures on the GrIS evolution on glacial–interglacial timescales through changes in submarine melting. The results show a very high sensitivity of the GrIS to changing oceanic conditions. Oceanic forcing is found to be a primary driver of GrIS expansion in glacial times and of retreat in interglacial periods. If switched off, palaeo-atmospheric variations alone are not able to yield a reliable glacial configuration of the GrIS. This work therefore suggests that considering the ocean as an active forcing should become standard practice in palaeo-ice-sheet modelling.

scholarly journals Magnetic Study of the Heated and Unheated Sedimentary Fillings of Sebkha Mhabeul, Southeast Tunisia: A Geophysical Method for Paleoclimatic Investigation and Tephrochronological Dating

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Elhoucine Essefi ◽  
Samir Mefteh ◽  
Mounir Medhioub ◽  
Chokri Yaich
Keyword(s):  
Magnetic Susceptibility ◽  
Spectral Analysis ◽  
Little Ice Age ◽  
Complete Loss ◽  
The Other ◽  
Ice Age ◽  
Geophysical Method ◽  
Climate Anomalies ◽  
The Core ◽  
Southeast Tunisia

This paper is meant to investigate the climatic and volcanic signals within the sedimentary filling of sebkha Mhabeul through a thermomagnetic study of a 37 cm length core. Values of the magnetic susceptibility at ambient temperature show that the core encompasses four climatic stages: the Warming Present (WP), the Little Ice Age (Late LIA), Early Little Ice Age (ELIA), and the Medieval Climate Anomalies (MCA). Added to the subcycles, the spectral analysis shows the individualization of an 888 yr cycle probably related to solar activity. The heating at 250°C is good-for-nothing since it was useful neither for climatic investigation nor for tephras layers detection. Heating at 700°C generated the complete loss of the climatic signal. On the other hand, it allowed the detection of the previously identified tephras layers. Further, it highlighted the presence of other tephras layers. The extraction by the bromoform confirms the presence of these tephras. The use of the same methodology may allow the detection of tephras layers within other sebkhas.

scholarly journals Spatially distributed runoff at the grounding line of a large Greenlandic tidewater glacier inferred from plume modelling

2017 ◽  
Vol 63 (238) ◽  
pp. 309-323 ◽  
Author(s):  
DONALD SLATER ◽  
PETER NIENOW ◽  
ANDREW SOLE ◽  
TOM COWTON ◽  
RUTH MOTTRAM ◽  
...  
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
Time Lapse ◽  
Atmospheric Temperature ◽  
Recent Change ◽  
Grounding Line ◽  
Tidewater Glacier ◽  
Spatially Distributed ◽  
Basal Sliding ◽  
Catchment Runoff

ABSTRACTUnderstanding the drivers of recent change at Greenlandic tidewater glaciers is of great importance if we are to predict how these glaciers will respond to climatic warming. A poorly constrained component of tidewater glacier processes is the near-terminus subglacial hydrology. Here we present a novel method for constraining near-terminus subglacial hydrology with application to marine-terminating Kangiata Nunata Sermia in South-west Greenland. By simulating proglacial plume dynamics using buoyant plume theory and a general circulation model, we assess the critical subglacial discharge, if delivered through a single compact channel, required to generate a plume that reaches the fjord surface. We then compare catchment runoff to a time series of plume visibility acquired from a time-lapse camera. We identify extended periods throughout the 2009 melt season where catchment runoff significantly exceeds the discharge required for a plume to reach the fjord surface, yet we observe no plume. We attribute these observations to spatial spreading of runoff across the grounding line. Persistent distributed drainage near the terminus would lead to more spatially homogeneous submarine melting and may promote more rapid basal sliding during warmer summers, potentially providing a mechanism independent of ocean forcing for increases in atmospheric temperature to drive tidewater glacier acceleration.

The contribution of numerical models to our understanding of the Phanerozoic CO2 history

2020 ◽  
Author(s):  
Yves Godderis ◽  
Yannick Donnadieu
Keyword(s):  
Carbon Cycle ◽  
Numerical Models ◽  
Continental Drift ◽  
Ice Age ◽  
Mountain Range ◽  
Climatic Trend ◽  
Carbon Cycle Model ◽  
Physically Based ◽  
Continental Weathering ◽  
The Many

&lt;p&gt;Our understanding of the geological regulation of the carbon cycle has been deeply influenced by the contribution of Bob Berner with his well-known model GEOCARB. Here, we will present a fundamentally different carbon cycle model that explicitly accounts for the effect of the paleogeography using physically based climate simulations and using 22 continental configurations spanning the whole Phanerozoic (GEOCLIM, geoclimmodel.wordpress.com). We will show that several key features of the Phanerozoic climate can be simply explained by the modulation of the carbon cycle by continental drift with the notable exception of the Late Paleozoic Ice Age, which is explained by the intense weathering of the Hercynian mountain range. In particular, the continental drift may have strongly impacted the runoff intensity as well as the weathering flux during the transition from the hot Early Cambrian world to the colder Ordovician world. Another fascinating example is the large atmospheric CO&lt;sub&gt;2&lt;/sub&gt; decrease simulated during the Triassic owing to the northward drift of Pangea exposing large continental area to humid sub-tropics and boosting continental weathering. Conversely, our model fails to reproduce the climatic trend of the last 100 Ma. This is due to the highly dispersed continental configurations of the last 100 Ma that optimize the consumption of CO&lt;sub&gt;2&lt;/sub&gt; through continental weathering. This discrepancy may be reduced if we account for a larger influence of the Earth degassing flux on the atmospheric CO&lt;sub&gt;2&lt;/sub&gt; evolution, which could come from the increase contribution of the pelagic component on the oceanic crust on the global carbonate flux and from the many sub-marine LIPs occurring during the Late Cretaceous.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals How can a glacial inception be predicted?

The Holocene ◽  
2011 ◽  
Vol 21 (5) ◽  
pp. 831-842 ◽  
Author(s):  
Michel Crucifix
Keyword(s):  
Greenhouse Gas ◽  
Numerical Models ◽  
Climate System ◽  
Ice Age ◽  
Glacial Cycles ◽  
The Holocene ◽  
Stochastic Dynamical System ◽  
Northern Summer ◽  
External Forcings ◽  
Inference Network

The Early Anthropogenic Hypothesis considers that greenhouse gas concentrations should have declined during the Holocene in absence of humankind activity, leading to glacial inception around the present. It partly relies on the fact that present levels of northern summer incoming solar radiation are close to those that, in the past, preceded a glacial inception phenomenon, associated with declines in greenhouse gas concentrations. However, experiments with various numerical models of glacial cycles show that next glacial inception may still be delayed by several tens of thousands of years, even with the assumption of a decline in greenhouse gas concentrations during the Holocene. Furthermore, as we show here, conceptual models designed to capture the gross dynamics of the climate system as a whole suggest also that small disturbances may sometimes cause substantial delays in glacial events, causing a fair level of unpredictability on ice age dynamics. This suggests the need for a validated mathematical description of climate system dynamics that allows us to quantify uncertainties on predictions. Here, it is proposed to organise our knowledge about the physics and dynamics of glacial cycles through a Bayesian inference network. Constraints on the physics and dynamics of climate can be encapsulated into a stochastic dynamical system. These constraints include, in particular, estimates of the sensitivity of the components of climate to external forcings, inferred from plans of experiments with large simulators of the atmosphere, oceans and ice sheets. On the other hand, palaeoclimate observations are accounted for through a process of parameter calibration. We discuss promises and challenges raised by this programme.

scholarly journals Asynchronous Coupling of Ice-Sheet and Atmospheric Forcing Models

1990 ◽  
Vol 14 ◽  
pp. 247-251 ◽  
Author(s):  
David Pollard ◽  
Isabelle Muszynski ◽  
Stephen H. Schneider ◽  
Starley L. Thompson
Keyword(s):  
Ice Sheet ◽  
Ice Age ◽  
Ice Thickness ◽  
Atmospheric Forcing ◽  
Weather Variability ◽  
Stochastic Forcing ◽  
Albedo Feedback

Asynchronous coupling schemes between ice sheet and atmospheric forcing models are evaluated for use in long-term ice-age simulations. In these schemes the ice sheet and atmospheric forcing are run together for short synchronous periods (Ts), alternating with longer asynchronous periods (TA) during which the ice sheet is run with atmospheric information extrapolated from the previous synchronous period(s). Two simple ice-sheet models are used that predict ice thickness as a function of latitude, and the atmosphere is represented by a prescribed pattern of net annual accumulation minus ablation. The pattern is shifted vertically to represent long-term orbital variations, stochastic inter-annual weather variability and ice-sheet albedo feedback.Several asynchronous schemes are evaluated by comparing results with those from fully synchronous runs. The best overall results are obtained using a scheme in which the forcing during each asynchronous period is linearly extrapolated from its means in the previous two synchronous periods. Differences from the synchronous results are caused primarily by poor sampling of the stochastic forcing component, which exaggerates the stochastic ice-sheet fluctuations. We examine how these errors depend on Ts and TA, and outline implications for GCM ice-age simulations.

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