The Impact of the Little Ice Age on Coccolithophores in the Central Mediterranea Sea

Abstract. The Little Ice Age (LIA) is the last episode of a series of Holocene climatic anomalies. There is still little knowledge on the response of the marine environment to the pronounced cooling of the LIA and to the transition towards the 20th century global warming. Here we present decadal-scale coccolithophore data from four short cores recovered from the central Mediterranean Sea (northern Sicily Channel and Tyrrhenian Sea), which on the basis of 210Pb activity span the last 200–350 years. The lowermost part of the record of one of the cores from the Sicily Channel, Station 407, which extends down to 1650 AD, is characterized by drastic changes in productivity. Specifically, below 1850 AD, the decrease in abundance of F. profunda and the increase of placoliths, suggest increased productivity. The chronology of this change is related to the main phase of the Little Ice Age, which might have impacted the hydrography of the southern coast of Sicily and promoted vertical mixing in the water column. The comparison with climatic forcings points out the importance of stronger and prolonged northerly winds, together with decreased solar irradiance.

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Calcareous nannofossil assemblages from the Central Mediterranean Sea over the last four centuries: the impact of the little ice age

Climate of the Past Discussions ◽

10.5194/cpd-6-817-2010 ◽

2010 ◽

Vol 6 (3) ◽

pp. 817-866 ◽

Cited By ~ 5

Author(s):

A. Incarbona ◽

P. Ziveri ◽

E. Di Stefano ◽

F. Lirer ◽

G. Mortyn ◽

...

Keyword(s):

Mediterranean Sea ◽

Little Ice Age ◽

Ice Age ◽

Tyrrhenian Sea ◽

Calcareous Nannofossil ◽

Central Mediterranean ◽

Decadal Scale ◽

Central Mediterranean Sea ◽

Sicily Channel ◽

The Impact

Abstract. We present decadal-scale calcareous nannofossil data from four short cores (Station 272, 37° 17' N, 12° 48' E, 226 m depth; St 342, 36° 42' N, 13° 55' E, 858.2 m depth; St 407, 36° 23' N, 14° 27' E, 345.4 m depth; C90-1M, 40° 36' N, 14° 42' E, 103.4 m depth) recovered in the central Mediterranean Sea (northern Sicily Channel and Tyrrhenian Sea), which, on the basis of 210Pb activity span the last 200–350 years. Assemblages are dominated by placoliths, mostly Emiliania huxleyi, while, at least in the Sicily Channel sediments, Florisphaera profunda was an important part of the coccolithophore community. The paleoenvironmental reconstruction, based on ecological preference of species and groups, suggests that the Tyrrhenian core C90-1M maintained higher productivity levels over recent centuries, with respect to the Sicily Channel sites, possibly because of more pronounced winter phytoplankton blooms, in agreement with modern primary productivity variations over the last ten years. The lowermost part of the record of one of the cores from the Sicily Channel, Station 407, which extends down to 1650 AD, is characterized by drastic changes in productivity. Specifically, below 1850 AD, the decrease in abundance of F. profunda and the increase of placoliths, suggest increased productivity. The chronology of this change is related to the main phase of the Little Ice Age, which might have impacted the hydrography of the southern coast of Sicily and promoted vertical mixing in the water column. The comparison with climatic forcings points out the importance of stronger and prolonged northerlies, together with decreased solar irradiance. The identification of the LIA in the northern Sicily Channel cover the Bond cycle BO that was missing in a previous study of Holocene climatic anomalies in the Sicily Channel. Finally, we suggest that major abundance changes in reworked nannofossil specimens, recorded in the Tyrrhenian core C90-1M, might be linked to variations in terrigenous supply from land. Paradoxically, higher amounts of reworking correspond to dry periods. We argue that soil and rock vulnerability is enhanced during times of prolonged drought and vegetation cover loss.

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Glacier dynamics at Helheim and Kangerdlugssuaq glaciers, southeast Greenland, since the Little Ice Age

The Cryosphere ◽

10.5194/tc-8-1497-2014 ◽

2014 ◽

Vol 8 (4) ◽

pp. 1497-1507 ◽

Cited By ~ 25

Author(s):

S. A. Khan ◽

K. K. Kjeldsen ◽

K. H. Kjær ◽

S. Bevan ◽

A. Luckman ◽

...

Keyword(s):

Mass Balance ◽

Little Ice Age ◽

Ice Age ◽

Short Term ◽

Velocity Change ◽

Outlet Glacier ◽

Episodic Events ◽

Highly Sensitive ◽

Decadal Scale ◽

Speed Up

Abstract. Observations over the past decade show significant ice loss associated with the speed-up of glaciers in southeast Greenland from 2003, followed by a deceleration from 2006. These short-term, episodic, dynamic perturbations have a major impact on the mass balance on the decadal scale. To improve the projection of future sea level rise, a long-term data record that reveals the mass balance beyond such episodic events is required. Here, we extend the observational record of marginal thinning of Helheim and Kangerdlugssuaq glaciers from 10 to more than 80 years. We show that, although the frontal portion of Helheim Glacier thinned by more than 100 m between 2003 and 2006, it thickened by more than 50 m during the previous two decades. In contrast, Kangerdlugssuaq Glacier underwent minor thinning of 40–50 m from 1981 to 1998 and major thinning of more than 100 m after 2003. Extending the record back to the end of the Little Ice Age (prior to 1930) shows no thinning of Helheim Glacier from its maximum extent during the Little Ice Age to 1981, while Kangerdlugssuaq Glacier underwent substantial thinning of 230 to 265 m. Comparison of sub-surface water temperature anomalies and variations in air temperature to records of thickness and velocity change suggest that both glaciers are highly sensitive to short-term atmospheric and ocean forcing, and respond very quickly to small fluctuations. On century timescales, however, multiple external parameters (e.g. outlet glacier shape) may dominate the mass change. These findings suggest that special care must be taken in the projection of future dynamic ice loss.

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Numerical simulation and decomposition of kinetic energy in the Central Mediterranean: insight on mesoscale circulation and energy conversion

Ocean Science ◽

10.5194/os-7-503-2011 ◽

2011 ◽

Vol 7 (4) ◽

pp. 503-519 ◽

Cited By ~ 51

Author(s):

R. Sorgente ◽

A. Olita ◽

P. Oddo ◽

L. Fazioli ◽

A. Ribotti

Keyword(s):

Numerical Simulation ◽

Kinetic Energy ◽

Energy Conversion ◽

Ocean Model ◽

Eddy Kinetic Energy ◽

Tyrrhenian Sea ◽

Central Mediterranean ◽

Baroclinic Energy Conversion ◽

Sicily Channel ◽

Mean Kinetic Energy

Abstract. The spatial and temporal variability of eddy and mean kinetic energy of the Central Mediterranean region has been investigated, from January 2008 to December 2010, by mean of a numerical simulation mainly to quantify the mesoscale dynamics and their relationships with physical forcing. In order to understand the energy redistribution processes, the baroclinic energy conversion has been analysed, suggesting hypotheses about the drivers of the mesoscale activity in this area. The ocean model used is based on the Princeton Ocean Model implemented at 1/32° horizontal resolution. Surface momentum and buoyancy fluxes are interactively computed by mean of standard bulk formulae using predicted model Sea Surface Temperature and atmospheric variables provided by the European Centre for Medium Range Weather Forecast operational analyses. At its lateral boundaries the model is one-way nested within the Mediterranean Forecasting System operational products. The model domain has been subdivided in four sub-regions: Sardinia channel and southern Tyrrhenian Sea, Sicily channel, eastern Tunisian shelf and Libyan Sea. Temporal evolution of eddy and mean kinetic energy has been analysed, on each of the four sub-regions, showing different behaviours. On annual scales and within the first 5 m depth, the eddy kinetic energy represents approximately the 60 % of the total kinetic energy over the whole domain, confirming the strong mesoscale nature of the surface current flows in this area. The analyses show that the model well reproduces the path and the temporal behaviour of the main known sub-basin circulation features. New mesoscale structures have been also identified, from numerical results and direct observations, for the first time as the Pantelleria Vortex and the Medina Gyre. The classical kinetic energy decomposition (eddy and mean) allowed to depict and to quantify the permanent and fluctuating parts of the circulation in the region, and to differentiate the four sub-regions as function of relative and absolute strength of the mesoscale activity. Furthermore the Baroclinic Energy Conversion term shows that in the Sardinia Channel the mesoscale activity, due to baroclinic instabilities, is significantly larger than in the other sub-regions, while a negative sign of the energy conversion, meaning a transfer of energy from the Eddy Kinetic Energy to the Eddy Available Potential Energy, has been recorded only for the surface layers of the Sicily Channel during summer.

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Simulated retreat of Jakobshavn Isbræ since the Little Ice Age controlled by geometry

The Cryosphere ◽

10.5194/tc-12-2249-2018 ◽

2018 ◽

Vol 12 (7) ◽

pp. 2249-2266 ◽

Cited By ~ 9

Author(s):

Nadine Steiger ◽

Kerim H. Nisancioglu ◽

Henning Åkesson ◽

Basile de Fleurian ◽

Faezeh M. Nick

Keyword(s):

Little Ice Age ◽

Ice Age ◽

Climate Forcing ◽

Relative Role ◽

Regional Warming ◽

History Of ◽

The Impact ◽

Term Response

Abstract. Rapid retreat of Greenland's marine-terminating glaciers coincides with regional warming trends, which have broadly been used to explain these rapid changes. However, outlet glaciers within similar climate regimes experience widely contrasting retreat patterns, suggesting that the local fjord geometry could be an important additional factor. To assess the relative role of climate and fjord geometry, we use the retreat history of Jakobshavn Isbræ, West Greenland, since the Little Ice Age (LIA) maximum in 1850 as a baseline for the parameterization of a depth- and width-integrated ice flow model. The impact of fjord geometry is isolated by using a linearly increasing climate forcing since the LIA and testing a range of simplified geometries. We find that the total length of retreat is determined by external factors – such as hydrofracturing, submarine melt and buttressing by sea ice – whereas the retreat pattern is governed by the fjord geometry. Narrow and shallow areas provide pinning points and cause delayed but rapid retreat without additional climate warming, after decades of grounding line stability. We suggest that these geometric pinning points may be used to locate potential sites for moraine formation and to predict the long-term response of the glacier. As a consequence, to assess the impact of climate on the retreat history of a glacier, each system has to be analyzed with knowledge of its historic retreat and the local fjord geometry.

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Pattern and Forcing of Northern Hemisphere Glacier Variations During the Last Millennium

Quaternary Research ◽

10.1016/0033-5894(86)90082-7 ◽

1986 ◽

Vol 26 (1) ◽

pp. 27-48 ◽

Cited By ~ 160

Author(s):

Stephen C. Porter

Keyword(s):

Northern Hemisphere ◽

Little Ice Age ◽

Ice Core ◽

Volcanic Eruptions ◽

Ice Age ◽

Phase Lag ◽

Mountain Glacier ◽

Radiocarbon Dates ◽

Glacier Fluctuations ◽

Decadal Scale

Time series depicting mountain glacier fluctuations in the Alps display generally similar patterns over the last two centuries, as do chronologies of glacier variations for the same interval from elsewhere in the Northern Hemisphere. Episodes of glacier advance consistently are associated with intervals of high average volcanic aerosol production, as inferred from acidity variations in a Greenland ice core. Advances occur whenever acidity levels rise sharply from background values to reach concentrations ≥1.2 μequiv H+/kg above background. A phase lag of about 10–15 yr, equivalent to reported response lags of Alpine glacier termini, separates the beginning of acidity increases from the beginning of subsequent ice advances. A similar relationship, but based on limited and less-reliable historical data and on lichenometric ages, is found for the preceding 2 centuries. Calibrated radiocarbon dates related to advances of non-calving and non-surging glaciers during the earlier part of the Little Ice Age display a comparable consistent pattern. An interval of reduced acidity values between about 1090 and 1230 A.D. correlates with a time of inferred glacier contraction during the Medieval Optimum. The observed close relation between Noothern Hemisphere glacier fluctuations and variations in Greenland ice-core acidity suggests that sulfur-rich aerosols generated by volcanic eruptions are a primary forcing mechanism of glacier fluctuations, and therefore of climate, on a decadal scale. The amount of surface cooling attributable to individual large eruptions or to episodes of eruptions is simlar to the probable average temperature reduction during culminations of Little Ice Age alacier advances (ca. 0.5°–1.2°C), as inferred from depression of equilibrium-line altitudes.

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Glacier dynamics at Helheim and Kangerdlugssuaq glaciers, southeast Greenland, since the Little Ice Age

The Cryosphere Discussions ◽

10.5194/tcd-8-1257-2014 ◽

2014 ◽

Vol 8 (1) ◽

pp. 1257-1278

Author(s):

S. A. Khan ◽

K. K. Kjeldsen ◽

K. H. Kjær ◽

S. Bevan ◽

A. Luckman ◽

...

Keyword(s):

Mass Balance ◽

Little Ice Age ◽

Initial Conditions ◽

Ice Age ◽

Short Term ◽

Episodic Events ◽

Highly Sensitive ◽

Decadal Scale ◽

Speed Up

Abstract. Observations over the past decade show significant ice loss associated with the speed-up of glaciers in southeast Greenland from 2003, followed by a deceleration from 2006. These short-term, episodic, dynamic perturbations have a major impact on the mass balance at the decadal scale. To improve the projection of future sea level rise, a long-term data record that reveals the mass balance beyond such episodic events is required. Here, we extend the observational record of marginal thinning of Helheim glacier (HG) and Kangerdlugssuaq glacier (KG) from 10 to more than 150 yr. We show that although the frontal portion of HG thinned by more than 100 m between 2003 and 2006, it thickened by more than 50 m during the previous two decades. In contrast, KG was stable from 1981 to 1998 and experienced major thinning only after 2003. Extending the record back to the end of the Little Ice Age (ca. 1850) shows no significant thinning of HG from 1850 to 1981, while KG underwent substantial thinning of ~265 m. Analyses of their sensitivity to sub-surface water temperature anomalies and variations in air temperature suggest that both HG and KG are highly sensitive to short-term atmospheric and ocean forcing, and respond very quickly to small fluctuations. At century time-scales, however, multiple external parameters (e.g. outlet shape) dominate the mass change. These findings undermine attempts to use measurements over the last decade as initial conditions to project future dynamic ice loss.

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Paleoclimatic reconstruction during the Little Ice Age in the Llanganuco basin, Cordillera Blanca (Peru)

10.5194/egusphere-egu2020-1726 ◽

2020 ◽

Author(s):

Joshua Er Addi Iparraguirre Ayala ◽

Jose Úbeda Palenque ◽

Ronald Fernando Concha Niño de Guzmán ◽

Ramón Pellitero Ondicol ◽

Francisco Javier De Marcos García-Blanco ◽

...

Keyword(s):

3D Reconstruction ◽

Air Temperature ◽

Little Ice Age ◽

Ice Age ◽

Lapse Rate ◽

Ratio Method ◽

Equilibrium Line Altitude ◽

Paleoclimatic Reconstruction ◽

High Resolution Satellite Images ◽

The Impact

The Equilibrium Line Altitude (ELA, m) is a good indicator for the impact of climate change on tropical glaciers , because it varies in time and space depending on changes in temperature and/or precipitation.The estimation of the ELA and paleoELA using the Area x Altitude Balance Ratio method (AABR; Osmaston, 2005) requires knowing the surface and hypsometry of glaciers or paleoglaciers (Benn et al. 2005) and the Balance Ratio (BR) correct (Rea, 2009).In the Llanganuco basin (~ 9&#176;3&#180;S; 77&#176;37&#180;W) there are very well preserved moraines near the current glaciers front. These deposits provide information to reconstruct the extent of paleoglaciers since the Little Ice Age (LIA) and deduce some paleo-climatic variables.The goal of this work has been to reconstruct the paleotemperature (&#176;C) during LIA, deduced from the difference between ELA AABR2016 and paleoELA AABRLIA.The paleoclimatic reconstruction was carried out in 6 phases: Phase 1) Development of a detailed geomorphological map (scale 1/10,000), in order to&#160; identify glacial landforms (advance moraines and polished rocks) which, due to their geomorphological context, can be considered of LIA, so palaeoglaciers can be delimited. Current glacial extension was done using dry season, high resolution satellite images. Phase 2) Glacial bedrock Reconstruction from glacier surface following the GLABTOP methodology (Linsbauer et al 2009). Phase 3) 3D reconstruction of paleoglacial surface using GLARE tool, based on bed topography and flow lines for each defined paleoglacial (Pellitero et al., 2016). As perfect plasticity model does not reflect the tension generated by the side walls of the valley, form factors were calculated based on the glacier thickness, lateral moraines and the geometry of the valley following the equation proposed by Nye (1952), adjusting the thicknesses generated in the paleoglacial front. Phase 4) Calculation of BR in a reference glacier (Artesonraju; 8&#176; 56&#8217;S; 77&#186;38&#8217;W), near to the study area, using the product BR = b &#8226; z &#8226; s, where BR= Balance Ratio; b= mass balance measured in fieldwork 2004-2014 (m); z= average altitude (meters) and s= surface (m2) of each altitude band of the glacier (with intervals of 100 m altitude). A value BR = 2.3 was estimated. Phase 5) Automatic reconstruction of the ELA &#160;AABR2016 and paleoELA AABRLIA using ELA Calculation tool (Pellitero et al. 2015) after 3D reconstruction of the glacial and paleoglacial surface in phases 2 and 3. Phase 6) Estimation of paleotemperature during LIA by solving the equation of Porter et al. (1995): &#8710;T (&#176;C)= &#8710;ELA &#8226; ATLR, where &#8710;T= air temperature depression (&#186;C); &#8710;ELA = variation of ELA AABR 2016-LIA and ATLR = Air Temperature Lapse Rate, using the average global value of the Earth (0.0065 &#176;C/m), considered valid for tropics.The results obtained were: ELA AABR2016= 5260m, paleoELA AABRLIA= 5084m, and &#8710;T = 1.1 &#176;C. The reconstruction of air paleotemperature is consistent with different studies that have estimated values between 1&#8211;2 &#176;C colder than the present, with intense rainfall (Matthews & Briffa, 2005; Malone et al., 2015).

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The impact of past climate change on genetic variation and population connectivity in the Icelandic arctic fox

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2012.1796 ◽

2012 ◽

Vol 279 (1747) ◽

pp. 4568-4573 ◽

Cited By ~ 8

Author(s):

Andrew Mellows ◽

Ross Barnett ◽

Love Dalén ◽

Edson Sandoval-Castellanos ◽

Anna Linderholm ◽

...

Keyword(s):

Genetic Variation ◽

Sea Ice ◽

Little Ice Age ◽

Haplotype Diversity ◽

Mitochondrial Control Region ◽

Population Connectivity ◽

Ice Age ◽

Arctic Fox ◽

Late Ninth Century ◽

The Impact

Previous studies have suggested that the presence of sea ice is an important factor in facilitating migration and determining the degree of genetic isolation among contemporary arctic fox populations. Because the extent of sea ice is dependent upon global temperatures, periods of significant cooling would have had a major impact on fox population connectivity and genetic variation. We tested this hypothesis by extracting and sequencing mitochondrial control region sequences from 17 arctic foxes excavated from two late-ninth-century to twelfth-century AD archaeological sites in northeast Iceland, both of which predate the Little Ice Age (approx. sixteenth to nineteenth century). Despite the fact that five haplotypes have been observed in modern Icelandic foxes, a single haplotype was shared among all of the ancient individuals. Results from simulations within an approximate Bayesian computation framework suggest that the rapid increase in Icelandic arctic fox haplotype diversity can only be explained by sea-ice-mediated fox immigration facilitated by the Little Ice Age.

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The impact of Little Ice Age cooling on mountain hemlock (Tsuga mertensiana) distribution in southcentral, Alaska

Quaternary International ◽

10.1016/j.quaint.2013.07.058 ◽

2013 ◽

Vol 310 ◽

pp. 228

Author(s):

R. Scott Anderson ◽

Darrell S. Kaufman ◽

Caleb Schiff ◽

Tom Daigle ◽

Edward Berg

Keyword(s):

Little Ice Age ◽

Ice Age ◽

Southcentral Alaska ◽

Tsuga Mertensiana ◽

The Impact

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Geodynamics of the Central Mediterranean (GEOMED) inferred from ambient seismic noise

10.5194/egusphere-egu21-6028 ◽

2021 ◽

Author(s):

Matthew Agius ◽

Fabrizio Magrini ◽

Giovanni Diaferia ◽

Fabio Cammarano ◽

Claudio Faccenna ◽

...

Keyword(s):

Seismic Noise ◽

Rift Zone ◽

Ambient Seismic Noise ◽

Special Focus ◽

Tyrrhenian Sea ◽

The European Union ◽

Central Mediterranean ◽

Phase Velocity Dispersion ◽

Radial Anisotropy ◽

Sicily Channel

The Central Mediterranean, the area encompassing Italy, Sardinia, Tunisia and Libya, is characterised by multiple tectonic processes (plate convergence, subduction, and backarc extension). The evolution and interaction of the plate margins within this relatively small area are still being unravelled particularly at the adjacent region known as the Sicily Channel located between Sicily, Tunisia, Libya and Malta. This Channel is characterised by a seismically and volcanically active rift zone. Much of the observations we have today for the southern parts of the Calabrian arc are either limited to the surface and the upper crust, or are broader and deeper from regional seismic tomography, missing important details about the lithospheric structure and dynamics. The project GEOMED (https://geomed-msca.eu) addresses this issue by processing all the seismic data available in the region in order to understand better the geodynamics of the Central Mediterranean.We measure Rayleigh- and Love-wave phase velocities from ambient seismic noise recordings to infer the structures of the Central Mediterranean, from the Central Apennines to the African foreland, with a special focus on the Sicily Channel Rift Zone (SCRZ). The phase-velocity dispersion curves have periods ranging from 5 to 100 seconds and sample through the entire lithosphere. We invert the dispersion data for isotropic and polarised shear velocities with depth and infer crustal thickness and patterns of radial anisotropy. We find that continental blocks have thick crust (30-50 km), whereas beneath the SCRZ the crust is thin (<25 km), and thinner beneath the Tyrrhenian Sea. Beneath the SCRZ and the Tyrrhenian Sea, the crustal shear velocities are characterised by positive radial anisotropy (VSH>VSV) indicative of horizontal flow or extension, whereas the uppermost mantle is characterised by slow shear velocities indicative of warmer temperatures and strong negative radial anisotropy (VSH>VSV) indicative of vertical flow. We discuss the relevance of these findings together with other geophysical studies such as the regional seismicity and GPS velocity vectors to identify the rifting process type of the SCRZ.This project has received funding from the European Union&#8217;s Horizon 2020 research and innovation programme under the Marie Sk&#322;odowska-Curie grant agreement No 843696.

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