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CHAPTER 13 • Climate During and Since the Last Deglaciation 235

substantial amount of their mass early in the deglacia- records near the subpolar North Atlantic Ocean. Tem-
tion by calving icebergs to the ocean. peratures in this region had warmed part of the way
Mid-Deglacial Cooling: The Younger Dryas The toward interglacial levels, but this reversal brought back
mid-deglacial pause in ice melting was accompanied by almost full glacial cold (Figure 13–6). The first evidence
a brief climatic oscillation that is especially evident in for this event came from pollen records in Europe.

Younger Dryas
Postglacial
moraines

Younger Dryas

Glacial polar front

North Atlantic Scotland England
Polar foraminifera Tree pollen Estimated summer temp
(%) (%) (°C)
100 80 60 40 20 0 0 50 100 10° 15° 20°
400 10,000
140 (interglacial)
Trees

160
Depth in core (cm) 200 Younger Dryas Depth in core (cm) 500 Younger Years ago 12,000 Younger
Dryas
180
Dryas
14,000
Late
220 Late glacial B glacial
Late
glacial
240 16,000
C
A
FIGURE 13-6 The Younger Dryas cold reversal Evidence of a cold episode that interrupted
the general deglacial warming comes from (A) a southward readvance of polar water in the
North Atlantic, (B) a reversal toward Arctic vegetation in Europe, and (C) a return to cooler
temperatures indicated by fossil insect populations in Britain. (Top: Adapted from W. F. Ruddiman
and A. McIntyre, “The North Atlantic Ocean During the Last Deglaciation,” Palaeogeography,
Palaeoclimatology, Palaeoecology 35 [1981]: 145–214. A: Adapted from W. F. Ruddiman, C. D.
Sancetta, and A. McIntyre, “Glacial/Interglacial Response Rate of Subpolar North Atlantic
Waters to Climatic Change: The Record in Oceanic Sediments,” Philosophical Transactions of the
Royal Society of London B 280 [1977]: 119–42. B: Adapted from G. R. Coope and G. Lemdahl,
“Regional Differences in the Late Glacial Climate of Northern Europe,” Journal of Quaternary
Science 10 [1995]: 391–95. C: Adapted from T. C. Atkinson et al., “Seasonal Temperatures in
Britain During the Past 20,000 Years, Reconstructed Using Beetle Remains,” Nature 325
[1987]: 587–92.)