MIS 5e to MIS 4 Inter/Glacial reconstructions
Endeavours to reconstruct the climatic/glacial conditions and chronologies from the onset of the Eemain interglacial period [MIS 5e:ca129-177?Ka ago] to the termination of the MIS 4 glacial era [ca70-55?Ka ago] are subject to a number of restrictions, which can compromise the final results.
Ice cores from numerous Antarctic, Greenland and intermediate core sites have added a new dimension to climate/chronological analyses. Ice cores can be dated by counting annual layers. These could be correlated with approximate time markers [e.g. volcanic eruptions and/or by synchronizing with variations in the earths orbital parameters]. Low ice accumulation [e.g. east central Antarctica] has the potential to inhibit accurate annual layer counting. There is minimal ice for the ca140-130Ka period in the GRIP ice core [Korerner, 1988]. It probably melted during the ensuing MIS 5e interglacial event. There are lags between the Arctic and Antarctic polar regions, which complicate correlations between northern and southern hemisphere ice cores. Landois [2003] contends the Eemain interglacial began ca135+/-2.5Ka in Antarctica, which is earlier than on Greenland. Supplementary studies tend to lend credence to his premise. This problem is compounded by variations in the volumes and types of gases, which generated on the two polar ice caps [e.g. in situ CO2 production on Greenland ice: Anklin, 1995].
The Greenland GSIP2 ice core scale was established by counting layers. For core depths in excess of 40Ka the degree of error is estimated to range from 5-10% [ca45Ka ice accumulation was relatively slow and C14 concentrations exhibit rapid change]. The MIS 5e interglacial era falls within this range of error and therefore the accuracy of the chronological estimates for this event could be tenuous. The Greenland GRIP and GISP2 ice core sites are only about 28km apart. The divergence rate between the two, for ages in excess of 40Ka exceeds 5.0%. The data for ice cores a greater distant apart might be more difficult to reconcile.
Deglaciation and glacial activities during MIS 2 [the last glacial maximum; ca25-18Ka] have destroyed many of the land forms, which are relevant to prior glacial and interglacial eras. Ice sheet build ups diminished in northern Siberia between the glacial periods MIS 6 ad MIS 2 and intensified in Canada and Scandinavia/the Baltic Depression. There appears to have been a 1500-2500km separation between the Rocky Mountain glaciers and the two eastern Canadian ice sheets during the MIS 5b cold period. In Canada the Quebec accumulated large volumes of ice during the MIS 4 glacial era, with the rate of buildup in the west appearing to be slower. The eastern and western Canadian ice sheets coalesced during the last glacial maximum. Projects to reconstruct climatic/glacial conditions during MIS 5e and MIS 4 will probably be more successful in northern Siberia and eastern Europe, where there is greater potential for preservation of the relevant land forms than there is in Canada and Scandinavia. Loess deposits in Europe can be traced to the cold, dry MIS 5d and MIS 5b dust storms. They may have originated from polar air outbreaks between Scandinavia and the Alps [speculation].
During MIS 5e the sea-ice limit in the Bering Strait was approximately 800km north of its 1995 location and the Alaskan tree line was about 600km further north than now. A realistic estimate of Eemain sea level ca124ka ago would be that it was approximately 2.6m higher than it is today and the temperatures were probably 3-5 degrees C warmer than now. Investigations of mineral crusts by J Dorale [2010] in coastal Majorca caves indicated that Mediterranean sea level was 1.25-1.16m higher during the ca82-80Ka warm MIS 5a event than it is now prior to an appreciable decline post ca79Ka. The volume and extent of ice sheets can vary by a significant margin over a relatively short time frame. M Miller's research of the Alaskan Ice Fields over a 25 year period recorded that 63% of 200 glaciers have retreated since 1950 ADE, 7% have advanced and 30% were static. The few that made long term advances contained more ice than all of the other glaciers combined. They were feed by exceptionally high snow fall in the upper peaks. These short duration variations indicate the complexities, which are associated with the reconstruction of ancient glacial patterns from a sparse database.
Similar problems have been encountered with sea level estimates. Isostatic [glacial] rebound after MIS 2 on the east coast of Sweden north of Stockholm can range up to 800m and is still in progress. Shorelines, which were occupied by the Vikings are currently about 8m above sea level. Ca12.5Ka ago an extensive portion of the Baltic Sea was covered by a glacial lake. Post 11.75Ka the ice dam was breeched and water cascaded into the North Sea. This process was repeated and as the northern shoreline rebounded from the weight of the ice sheets, the low southern coast, which had been covered by appreciably less ice, was partially inundated. Since the end of the last ice age parts of eastern Canada have been elevated by up to 900m, after the 2km thin ice sheets melted. Isostatic rebound and eustatic sea level change along the western Canada/Alaska coast, after the last glacial maximum generated a complex relative sea level change pattern. Regions close to the mainland and within the isostatic depression range of the Cordilleran ice sheets had sea levels higher than now as the ice receded. On the east coast of the Alexander Archipelago offshore from SW Alaska ca12.5Ka ago sea level is estimated to have been 60-80m higher than it is at the present time. Isostatic movements between regions overlain by thick coastal ice build ups and thinly glaciated offshore islands were highly variable, resulting in significantly divergent sea level trends over relatively short east-west distances. J Claque [1989] reported that marine deposits dating to ca12.4+/-0.8Ka on Kuprean Island are now 62m above sea level. Along this eastern Pacific Ocean coastline, tectonic activity has uplifted and downthrown sediments over the past 15ka, which further complicates endeavours to estimate ancient, sea levels. As sea levels rose from the glacial melt, the additional weight of water depressed some sea bottoms. These factors also impacted on the areas, which were covered by thick layers of ice in NW Europe. The above factors can distort the magnitude of relative sea level measurements, especially for the MIS 5e-MIS 4 period, because there is a dearth of pertinent data.
The transition from MIS 5a interglacial era to the MIS4 ice age in Europe has been investigated by the Helmholts Centre [2008]. Analyses of a number of lacustrine sedimentary cores from locales between Grobern, Saxony, and Ples by the Volga River revealed that the vegetation trends inferred a number of sporadic warming events, during an overall decline in temperatures.
There are prominent acidic spikes on the Greenland GRIP and Antarctic EDML ice cores ca74.0+/-2.0Ka, which might relate to the massive Toba volcanic eruption or eruptions [?] on the Indonesian Archipelago [A Svensson, 2013]. There was a coeval warming episode in Antarctica and a cooling event on Greenland, which might be related to a lowering Atlantic Meridional Overturning Circulation? The Toba volcanic eruption did not initiate the MIS 4 ice age.
Collation of the above comments indicates that reconstruction of the climate, glacial activity, sea level changes and chronology from the onset of the interglacial period MIS 5e [ca128.6?Ka] until the end of the MIS 4 glacial era [ca55?Ka]can be prone to error. This is especially applicable to Canada and Scandinavia/the Baltic Depression, where intense glacial and deglaciation activity have partially or totally eradicated evidence of earlier interglacial and glacial events. The current status of some MIS 5e and MIS 4 studies can probably be classified as realistic approximations, because can sometimes vary temporally over relatively short distances.
Ice cores from numerous Antarctic, Greenland and intermediate core sites have added a new dimension to climate/chronological analyses. Ice cores can be dated by counting annual layers. These could be correlated with approximate time markers [e.g. volcanic eruptions and/or by synchronizing with variations in the earths orbital parameters]. Low ice accumulation [e.g. east central Antarctica] has the potential to inhibit accurate annual layer counting. There is minimal ice for the ca140-130Ka period in the GRIP ice core [Korerner, 1988]. It probably melted during the ensuing MIS 5e interglacial event. There are lags between the Arctic and Antarctic polar regions, which complicate correlations between northern and southern hemisphere ice cores. Landois [2003] contends the Eemain interglacial began ca135+/-2.5Ka in Antarctica, which is earlier than on Greenland. Supplementary studies tend to lend credence to his premise. This problem is compounded by variations in the volumes and types of gases, which generated on the two polar ice caps [e.g. in situ CO2 production on Greenland ice: Anklin, 1995].
The Greenland GSIP2 ice core scale was established by counting layers. For core depths in excess of 40Ka the degree of error is estimated to range from 5-10% [ca45Ka ice accumulation was relatively slow and C14 concentrations exhibit rapid change]. The MIS 5e interglacial era falls within this range of error and therefore the accuracy of the chronological estimates for this event could be tenuous. The Greenland GRIP and GISP2 ice core sites are only about 28km apart. The divergence rate between the two, for ages in excess of 40Ka exceeds 5.0%. The data for ice cores a greater distant apart might be more difficult to reconcile.
Deglaciation and glacial activities during MIS 2 [the last glacial maximum; ca25-18Ka] have destroyed many of the land forms, which are relevant to prior glacial and interglacial eras. Ice sheet build ups diminished in northern Siberia between the glacial periods MIS 6 ad MIS 2 and intensified in Canada and Scandinavia/the Baltic Depression. There appears to have been a 1500-2500km separation between the Rocky Mountain glaciers and the two eastern Canadian ice sheets during the MIS 5b cold period. In Canada the Quebec accumulated large volumes of ice during the MIS 4 glacial era, with the rate of buildup in the west appearing to be slower. The eastern and western Canadian ice sheets coalesced during the last glacial maximum. Projects to reconstruct climatic/glacial conditions during MIS 5e and MIS 4 will probably be more successful in northern Siberia and eastern Europe, where there is greater potential for preservation of the relevant land forms than there is in Canada and Scandinavia. Loess deposits in Europe can be traced to the cold, dry MIS 5d and MIS 5b dust storms. They may have originated from polar air outbreaks between Scandinavia and the Alps [speculation].
During MIS 5e the sea-ice limit in the Bering Strait was approximately 800km north of its 1995 location and the Alaskan tree line was about 600km further north than now. A realistic estimate of Eemain sea level ca124ka ago would be that it was approximately 2.6m higher than it is today and the temperatures were probably 3-5 degrees C warmer than now. Investigations of mineral crusts by J Dorale [2010] in coastal Majorca caves indicated that Mediterranean sea level was 1.25-1.16m higher during the ca82-80Ka warm MIS 5a event than it is now prior to an appreciable decline post ca79Ka. The volume and extent of ice sheets can vary by a significant margin over a relatively short time frame. M Miller's research of the Alaskan Ice Fields over a 25 year period recorded that 63% of 200 glaciers have retreated since 1950 ADE, 7% have advanced and 30% were static. The few that made long term advances contained more ice than all of the other glaciers combined. They were feed by exceptionally high snow fall in the upper peaks. These short duration variations indicate the complexities, which are associated with the reconstruction of ancient glacial patterns from a sparse database.
Similar problems have been encountered with sea level estimates. Isostatic [glacial] rebound after MIS 2 on the east coast of Sweden north of Stockholm can range up to 800m and is still in progress. Shorelines, which were occupied by the Vikings are currently about 8m above sea level. Ca12.5Ka ago an extensive portion of the Baltic Sea was covered by a glacial lake. Post 11.75Ka the ice dam was breeched and water cascaded into the North Sea. This process was repeated and as the northern shoreline rebounded from the weight of the ice sheets, the low southern coast, which had been covered by appreciably less ice, was partially inundated. Since the end of the last ice age parts of eastern Canada have been elevated by up to 900m, after the 2km thin ice sheets melted. Isostatic rebound and eustatic sea level change along the western Canada/Alaska coast, after the last glacial maximum generated a complex relative sea level change pattern. Regions close to the mainland and within the isostatic depression range of the Cordilleran ice sheets had sea levels higher than now as the ice receded. On the east coast of the Alexander Archipelago offshore from SW Alaska ca12.5Ka ago sea level is estimated to have been 60-80m higher than it is at the present time. Isostatic movements between regions overlain by thick coastal ice build ups and thinly glaciated offshore islands were highly variable, resulting in significantly divergent sea level trends over relatively short east-west distances. J Claque [1989] reported that marine deposits dating to ca12.4+/-0.8Ka on Kuprean Island are now 62m above sea level. Along this eastern Pacific Ocean coastline, tectonic activity has uplifted and downthrown sediments over the past 15ka, which further complicates endeavours to estimate ancient, sea levels. As sea levels rose from the glacial melt, the additional weight of water depressed some sea bottoms. These factors also impacted on the areas, which were covered by thick layers of ice in NW Europe. The above factors can distort the magnitude of relative sea level measurements, especially for the MIS 5e-MIS 4 period, because there is a dearth of pertinent data.
The transition from MIS 5a interglacial era to the MIS4 ice age in Europe has been investigated by the Helmholts Centre [2008]. Analyses of a number of lacustrine sedimentary cores from locales between Grobern, Saxony, and Ples by the Volga River revealed that the vegetation trends inferred a number of sporadic warming events, during an overall decline in temperatures.
There are prominent acidic spikes on the Greenland GRIP and Antarctic EDML ice cores ca74.0+/-2.0Ka, which might relate to the massive Toba volcanic eruption or eruptions [?] on the Indonesian Archipelago [A Svensson, 2013]. There was a coeval warming episode in Antarctica and a cooling event on Greenland, which might be related to a lowering Atlantic Meridional Overturning Circulation? The Toba volcanic eruption did not initiate the MIS 4 ice age.
Collation of the above comments indicates that reconstruction of the climate, glacial activity, sea level changes and chronology from the onset of the interglacial period MIS 5e [ca128.6?Ka] until the end of the MIS 4 glacial era [ca55?Ka]can be prone to error. This is especially applicable to Canada and Scandinavia/the Baltic Depression, where intense glacial and deglaciation activity have partially or totally eradicated evidence of earlier interglacial and glacial events. The current status of some MIS 5e and MIS 4 studies can probably be classified as realistic approximations, because can sometimes vary temporally over relatively short distances.
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