Period 1011 ka 1 ka BP

The start of the Holocene is estimated most often between 10 and 11 ka before present (years BP, the present being defined as 1950 A.D.). However, glaciological proxy data show that this date should be shifted to about 11.6 ka

(see e.g. Johnsen et al. 1992 or O'Brien et al. 1995). As can be seen from Figure 10.1, there is a dramatic change of climate at about this time. At the Summit and Dye 3 8lsO profdes, the change is equal to 3~4%o (it gives about a 5 7°C rise in temperature). Most of the transition between the Younger Dryas and the Holocene occurred in a few decades, according to GISP2 (Greenland Ice Sheet Project) oxygen isotope (5irO) ice record (Taylor et al. 1997). Then the wanning was significantly less and the typical Holocene values reached about 10.2 ka BP.

Oxygen Isotopes Greenland

Figure 10.1. Continuous 8lfiO profiles along sections of four Greenland ice cores from Summit (Central), Dye 3 (Southeast), Camp Century (Northwest) and Renland (East Greenland), spanning nearly the same time interval. The four records are all plotted on linear depth scales, of which only the Summit depth scale is shown to the left along with a Summit timescale. The heavy and thin vertical lines indicate estimated 5 levels characteristic of late-glacial cold and mild stages respectively. The figures close to these lines define a suggested numbering of significant mid- and late-glacial interstadials (after Johnsen et al. 1992).

1,800

Figure 10.1. Continuous 8lfiO profiles along sections of four Greenland ice cores from Summit (Central), Dye 3 (Southeast), Camp Century (Northwest) and Renland (East Greenland), spanning nearly the same time interval. The four records are all plotted on linear depth scales, of which only the Summit depth scale is shown to the left along with a Summit timescale. The heavy and thin vertical lines indicate estimated 5 levels characteristic of late-glacial cold and mild stages respectively. The figures close to these lines define a suggested numbering of significant mid- and late-glacial interstadials (after Johnsen et al. 1992).

In this period a substantial increase in the annual layer accumulation was also noted (Figure 10.2) in the GISP2 deep core. Distinct changes in chemical flux values (marine and terrestrial Na, CI, Mg, K, and Ca), which represent changes in the atmospheric composition over the Greenland Summit, are also evident (see Figure 10.3 and O'Brien et al. 1995; Taylor et al. 1997). As can be seen in Figure 10.1 it is also evident that the Holocene is a period of a relatively stable climate with mean 5IS0 values of -34.7 %o and -34.9 %o for GISP2 and GRIP (Greenland Ice-core Project), respectively (Grootes et al. 1993). However, the small Holocene 8lilO fluctuations of 1-2 %o occur very often and are sufficient to detect changes in temperature conditions. The Holocene climate of the Arctic will be characterised here mainly according to the data from Greenland, Canadian high Arctic, and the Eurasian Arctic islands.

Precipitation Holocene Eurasia

Cal BP

Figure 10.2. Record of 100-year smoothed accumulation and oxygen isotope profiles from the GISP2 core from 12,000 years BP to the present. Reprinted with the permission from Meese

D. A., Gow A. J., Grootes P., Mayewski P. A.. Ram M„ Stuiver M„ Taylor K. C„ Waddington

E. D. and Zielinski G. A., 'The accumulation record from the GISP2 core as an indicator of climate change throughout the Holocene', Science, 266, 1680-1682. Copyright 1994 American Association for the Advancement of Science.

Cal BP

Figure 10.2. Record of 100-year smoothed accumulation and oxygen isotope profiles from the GISP2 core from 12,000 years BP to the present. Reprinted with the permission from Meese

D. A., Gow A. J., Grootes P., Mayewski P. A.. Ram M„ Stuiver M„ Taylor K. C„ Waddington

E. D. and Zielinski G. A., 'The accumulation record from the GISP2 core as an indicator of climate change throughout the Holocene', Science, 266, 1680-1682. Copyright 1994 American Association for the Advancement of Science.

Figure 10.3. Profiles of the GISP estimated ss and nss species for the Holocene and potential climate-forcing factors. All profiles are smoothed with a robust spline {equivalent to a 100-year smooth) to be consistent with previously published GISP2 data (Mayewski et at. 1994). The ssNa profile represents the behaviour of all ss speeies and is illustrated through the YD and part of the Bolling-Allerod (B/A) events to reference the relatively low Holocene glaciochcmical concentrations. Increases in concentration are marked by arrows. Episodes of triple oscillations defined as 5I4C intervals which have Maunder- and Sporer-type patterns occurring in sets of three are also indicated (T). The most recent triple event corresponds to the Maunder. Sporer, and Wolf solar activity minima. Reprinted with permission from O'Brien S. R.. Mayewski P. A., Meeker L. D., Meese D. A., Twickler M. S. and Whitlow S. L, "Complexity of Holocene climate as reconstructed from a Greenland ice core'. Science, 270. 1962-1964. Copyright 1995 American Association for the Advancement of Science.

June insolation 60*N (W cm^year1)

nSS Na flu*

Sea level elevation (m)

Bolling Allered

Figure 10.3. Profiles of the GISP estimated ss and nss species for the Holocene and potential climate-forcing factors. All profiles are smoothed with a robust spline {equivalent to a 100-year smooth) to be consistent with previously published GISP2 data (Mayewski et at. 1994). The ssNa profile represents the behaviour of all ss speeies and is illustrated through the YD and part of the Bolling-Allerod (B/A) events to reference the relatively low Holocene glaciochcmical concentrations. Increases in concentration are marked by arrows. Episodes of triple oscillations defined as 5I4C intervals which have Maunder- and Sporer-type patterns occurring in sets of three are also indicated (T). The most recent triple event corresponds to the Maunder. Sporer, and Wolf solar activity minima. Reprinted with permission from O'Brien S. R.. Mayewski P. A., Meeker L. D., Meese D. A., Twickler M. S. and Whitlow S. L, "Complexity of Holocene climate as reconstructed from a Greenland ice core'. Science, 270. 1962-1964. Copyright 1995 American Association for the Advancement of Science.

December E0F1 res Mg dm nsoHion 60"N (Hgton iysar')

ssNaflux (kgmrr-'yaaf1)

Land tea (Percent of volume from 18.000 years B.P]

December E0F1 res Mg dm nsoHion 60"N (Hgton iysar')

ssNaflux (kgmrr-'yaaf1)

June insolation 60*N (W cm^year1)

nSS Na flu*

Land tea (Percent of volume from 18.000 years B.P]

Sea level elevation (m)

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