Past Climate Variability and Change in the Arctic and at High Latitudes

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4 The U.S. Climate Change Science Program Executive Summary RECOMMENDATIONS • Paleoclimatic data on the Arctic are generated by numerous international investigators who study a great range of archives throughout the vast reaches of the Arctic. The value of this diversity is evident in this report. Many of the key results of this report rest especially on the outcomes of community-based syntheses, including the CAPE Project, and multiply replicated, heavily sampled archives such as the central Greenland deep ice cores. Results from the ACEX deep coring in Arctic Ocean sediments were appearing as this report was being written. These results are quite valuable and will become more so with synthesis and replication, including comparison with land-based and marine records. The number of questions answered, and raised, by this one new data set shows how sparse the data are on many aspects of Arctic paleoclimatic change. Future research should maintain and expand the diversity of investigators, techniques, archives, and geographic locations, while promoting development of community-based syntheses and multiply replicated, heavily sampled archives. Only through breadth and depth can the remaining uncertainties be reduced while confidence in the results is improved. • The questions asked of this study by the CCSP are relevant to public policy and require answers. The answers provided here are, we hope, useful and informative. However, we recognize that despite the contributions of many community members to this report, in many cases a basis was not available in the refereed scientific literature to provide answers with the accuracy and precision desired by policy-makers. Future research activities in Arctic paleoclimate should address in greater detail the policy-relevant questions motivating this report. • Paleoclimatic data provide very clear evidence of past changes in important aspects of the Arctic climate system. The ice of the Greenland Ice Sheet, smaller glaciers and ice caps, the Arctic Ocean, and in soils is shown to be vulnerable to warming, and Arctic ecosystems are strongly affected by changing ice and climate. National and international studies generally project rapid warming in the future. If this warming occurs, the paleoclimatic data indicate that ice will melt and associated impacts will follow, with implications for ecosystems and economies. The results presented here should be utilized by science managers in the design of monitoring, process, and model-projection studies of Arctic change and linked global responses.
1 CHAPTER INTRODUCTION Past Climate Variability and Change in the Arctic and at High Latitudes Preface—Why and How to Use This Synthesis and Assessment Report Lead Author: Joan Fitzpatrick, U.S. Geological Survey, Denver, CO Contributing Authors: Richard B. Alley*, Pennsylvania State University, University Park, PA; Julie Brigham-Grette*, University of Massachusetts, Amherst, MA; Gifford H. Miller*, University of Colorado, Boulder, CO; Leonid Polyak*, Ohio State University, Columbus, OH; Mark Serreze, University of Colorado, Boulder, CO * SAP 1.2 Federal Advisory Committee Member The U.S. Climate Change Science Program (CCSP), a consortium of Federal agencies that investigates climate, has established a Synthesis and Assessment Program as part of its Strategic Plan. A primary objective of the CCSP is to provide the best science-based knowledge possible to support public discussion and government- and private-sector decisions about the risks and opportunities associated with changes in climate and in related environmental systems (U.S. Climate Change Science Program, 2007). The CCSP has identified an initial set of 21 Synthesis and Assessment Products (SAPs) that address the highest-priority research, observation, and information needed to support decisions about issues related to climate change. This assessment, SAP 1.2, focuses on the evidence for and record of past climate change in the Arctic. This SAP is one of three reports that addresses the climate-variability-and-change research element and Goal 1 of the CCSP Strategic Plan to improve knowledge of Earth’s past and present climate and environment, including its natural variability, and improve understanding of the causes of observed variability and change. The development of an improved understanding of natural, long-term cycles in climate is one of the primary goals of the climate research element and Goal 1 of the CCSP (U.S. Climate Change Science Program, 2007). The Arctic region of Earth, by virtue of its sensitivity to the effects of climate change through strong climate feedback mechanisms, has a particularly informative paleoclimate record. Because mechanisms operating in the Arctic and at high northern latitudes are also linked to global climate mechanisms, an examination of how Arctic climate has changed in the past is also globally informative. 5
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CHAPTER 6 ABSTRACT Past Climate Var
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second, and the Transpolar Drift, t
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EXTENT, IN MILLION SQUARE KILOMETER
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Until recently, and for logistical
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1990; Fyles et al., 1994), the nort
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FREQUENCY 50 45 40 35 30 25 20 15 1
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Seas around icelAnd provide a rare
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at least 14 Ma (Darby, 2008). Sever
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T. quinqueloba, IN SPECIMENS PER GR
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7 6 5 4 3 2 1 Past Climate Variabil
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SEA-ICE COVERAGE, IN NUMBER OF MONT
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QUARTZ WEIGHT, IN PERCENT 6 5 4 3 2
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6.5 SUMMARY Geological data indicat
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GLOSSARY GLOSSARY 8 ka cold event A
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CAPE Project Circum-Arctic PaleoEnv
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Eccentricity Out of roundness (elli
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Innuitian sector The ice sheet that
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Moraine Landforms (typically ridges
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Positive feedback In climate studie
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Trough-mouth fans Undersea deposits
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