Evolution of northern wetlands since the Last Glacial MaximumPirita Oksanen, University of Bristol, School of Geographical Sciences

Contact p.oksanen@bristol.ac.uk. Wetland data synthesis web site http://www.bridge.bris.ac.uk/projects/deglaciation/wetlands.html

17000 cal BP

16000 cal BP

15000 cal BP

14000 cal BP

13000 cal BP

12000 cal BP

11000 cal BP

10000 cal BP

9000 cal BP

8000 cal BP

7000 cal BP

Fennoscandia - Baltia, 638 dates altitude known 39%, average 193 m

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-90

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Central Europe, 137 dates altitude known 49%, average 350 m

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Britain, 55 dates altitude known 81%, average 109 m

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21K

-60

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East Siberia, 111 dates altitude known 59%, average 70 m

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-1

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Alaska, 213 dates altitude known 20%, average 366 m

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-12

-10

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Western North America, 399 dates altitude known 24%, average 810 m

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-70

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Eastern North America, 423 dates altitude known 25%, average 134 m

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-70

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Hudson Bay, 100 dates altitude known 16%, average 130 m

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-80

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World above 39N, 2515 dates altitude known 30%, average 296 m

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-30

-25

-20

-15

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-5

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Introduction

Information from ca. 3000 late-Quaternary peat cores at above 39 N has been collected in a global wetland

database within the QUEST-Deglaciation project. The data, including modern wetland type and area as well as

peat stratigraphy and dating, are still incomplete, but most cores comprise at least the basal date indicating

the time of wetland initiation.

The synthesis is carried out in order to document the evolution of wetlands since the Last Glacial Maximum, to better understand the patterns of wetland initiation and the role of wetlands in the terrestrial carbon cycle

during the last Ice Age and deglaciation, and to identify gaps in the existing wetland research. The data set will

also be used to validate Earth System model simulations.

Based on the collected data, a set of maps and time series is created, showing the change in peatland

initiation and extent through time. All dates are calibrated to calendar years BP using OxCal calibration programme. The study area is divided into regions that show differences in the pattern of peatland evolution. Analyses on different characteristics are underway.

AcknowledgementsEarlier databases by Gorham et al. (2005) and McDonald et al. (2006) are incorporated into this database. The ice sheets reconstructions are based on ICE-5G by Peltier (2004). Continental outlines are compiled by P. Bartlein.

Results

There was no significant peat accumulation in the high-latitudes of the northern hemisphere during the Last Glacial Maximum. Deglaciation started in America at ca. 16,000 cal BP, and first peatlands appeared at the same time. In Europe, deglaciation started earlier, at about 18,000 cal BP, but first peatlands are recorded at around 14,500 cal BP. Most of the early peatlands in America are now

buried. In non-glaciated Alaska the formation started at ca. 17,500 cal BP, but in Siberia considerably later, at ca. 14,000 cal BP. At its most active peatland initiation was between 11,000 and 9000 cal BP: the highest peak in America occurred at ca. 10,500 and across Eurasia at ca.

9000 cal BP. Half of the glaciers had melted from Europe by ca. 15,000 cal BP, and by ca. 10,000 cal BP from America. For peatlands, the half point was reached at 8000 and 9000 cal BP,

respectively, and in Siberia, at 8500 cal BP. By around 7000 cal BP, when 60% of the modern peatlands existed, the distribution pattern was similar to today. The biggest relative troughs in the initiation curves occur at ca. 12,000 cal BP in Europe and eastern North America, 11,500 cal BP in Alaska, ca. 8500 cal BP in western North America, 7500 cal BP in eastern Siberia and 7000 cal BP

in western Siberia. None of these troughs extend below the standard deviation. Region together with mire type predicts best the age of a peatland or peat layer, but the variability is

still large. Bogs show generally more constant accumulation rates than fens. Altitude makes little difference; most peatlands are located at lowlands, but peat of all ages is found at high altitudes too.

All sites currently in the database, and division into regions.

Extent of glaciers and distribution of peatlands through time

Peatland initiation start and rates compared for the regions

bogs

R2 = 0.3736

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cases

cal

BP

fens and swamps

R2 = 0.1069

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casesca

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Peatland initiation dates and area covered by glaciers, for the world above 39 N and the regions

Age-depth comparison of European bogs and fens

European Russia, 63 dates altitude known 48%, average 107 m

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-18-16-14-12-10-8-6-4-20

Western Siberia, 286 dates altitude known 15%, average 115 m

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35

-0.45

-0.4

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0 10 205 15

W SiberiaE Siberia

Fennosc/RussiaC-W Europe

Alaska

HudsonE America

W America

World 39N

Peatland initiation

peak (above SD) trough (below SD)

cal BP

start (1%)highest