Arctic–Subarctic Ocean Fluxes: Defining the Role of the Northern Seas in Climate

727 Pages·2008·69.62 MB·English

by  Bob Dickson

Arctic–Subarctic Ocean Fluxes
Arctic–Subarctic Ocean
Fluxes
Defi ning the Role of the Northern Seas
in Climate
Edited by
Robert R. Dickson
Centre for Environment, Fisheries and Aquaculture Science,
Lowestoft, UK
Jens Meincke
Institute für Meereskunde, University of Hamburg, Germany
and
Peter Rhines
Oceanography and Atmospheric Sciences Departments,
University of Washington, Seattle, WA, USA
Library of Congress Control Number: 2007940853
ISBN 978-1-4020-6773-0 (HB)
ISBN 978-1-4020-6774-7 (e-book)
Published by Springer,
P.O. Box 17, 3300 AA Dordrecht, The Netherlands.
www.springer.com
Cover illustration: Greenland. Photo by Tom Haine, John Hopkins University.
Printed on acid-free paper
All Rights Reserved for Chapters 12 and 15
© 2008 Springer Science + Business Media B.V.
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Foreword
The Ocean-Atmosphere-Cryosphere sys-
tem of the Arctic is of unique importance
to the World, its climate and its peoples
and is changing rapidly; it is no accident
that the Arctic Climate Impact Assessment
(ACIA) was the first comprehensive
regional assessment of climate-impact to
be conducted. Reporting in 2005, ACIA
concluded that changes in climate and in
ozone and UV radiation levels were
likely to affect every aspect of life in the
Arctic. In effect, the ACIA process was
essentially one of prediction: projecting
that large climatic changes are likely to
occur over the 21st century and documenting what might be their projected
impacts.
Although the ACIA Report was based on the most modern synthesis of observa-
tions, modelling and analysis by hundreds of Arctic scientists, it notes with clarity
that its conclusions are only a first step in what must be a continuing process.
Reporting in November 2007, the 2nd International Conference on Arctic Research
Planning (ICARP II) has recently made much the same point. To make its projec-
tions with higher confidence, --- to take the crucial second step in other words, ----
both reports plainly state the need for a more complete and detailed understanding
of the complex processes, interactions, and feedbacks that drive and underlie
‘change’ at high northern latitudes, including particularly the long-term processes
of circulation and exchange in our northern seas where much of the decadal ‘mem-
ory’ for Arctic change must reside.
In this volume, assembled for the first time, we find a detailed description of
much of what we believe is essential to take that crucial second step. Here, for
example, are described the controls, ‘near and remote, short-term as well as long-
term’ that have been involved in providing the polar basin in recent years with a
steady supply of increasingly warmer water through subarctic seas. We find, more-
v
vi Foreword
over, a detailed description of the interplay between the storage and release of
freshwater from the Central Arctic and its likely impact on the ‘workings’ of the
Ocean’s thermohaline ‘conveyor’. And throughout the book, we are given a mod-
ern account of how well we can simulate the important elements of Arctic-subarctic
exchange ---– in some cases very well indeed.
In the future there will, of course, be new stages of understanding and observa-
tions, better models and perhaps even a different set of ‘driving questions’ before
society eventually learns to project, adapt and respond to Arctic change. This
volume spells out what we now perceive are the driving questions to be addressed
if we are to move our skills in prediction to a higher level.
The release of this publication coincides with the [4th] International Polar Year,
a comprehensive, international effort in polar science and climate change. As the
global scientific community conducts its latest polar study, the reader should be
assured that the benchmarks this volume represents are a necessary and a consider-
able step towards understanding the critical role that the Arctic and subarctic seas
play in the global climate system and hence, their importance to humanity
everywhere.
Dr Robert W. Corell, Chair,
Arctic Climate Impact Assessment (ACIA),
Chair, International Conference on Arctic Research Planning (ICARP II) and
Director, Global Change Program at the H. John Heinz III
Center for Science, Economics and the Environment.
Contents
Foreword ......................................................................................................... v
Arctic–Subarctic Ocean Fluxes: Defining the Role
of the Northern Seas in Climate. A General Introduction ................ 1
Bob Dickson, Jens Meincke, and Peter Rhines
1 The Inflow of Atlantic Water, Heat, and Salt to the Nordic
Seas Across the Greenland–Scotland Ridge........................................ 15
Bogi Hansen, Svein Østerhus, William R. Turrell,
Steingrímur Jónsson, Héðinn Valdimarsson, Hjálmar Hátún,
and Steffen Malskær Olsen
2 Volume and Heat Transports to the Arctic Ocean Via
the Norwegian and Barents Seas .......................................................... 45
Øystein Skagseth, Tore Furevik, Randi Ingvaldsen,
Harald Loeng, Kjell Arne Mork, Kjell Arild Orvik,
and Vladimir Ozhigin
3 Variation of Measured Heat Flow Through the Fram
Strait Between 1997 and 2006 .............................................................. 65
Ursula Schauer, Agnieszka Beszczynska-Möller,
Waldemar Walczowski, Eberhard Fahrbach, Jan Piechura,
and Edmond Hansen
4 Is Oceanic Heat Transport Significant
in the Climate System? .......................................................................... 87
Peter Rhines, Sirpa Häkkinen, and Simon A. Josey
5 Long-Term Variability of Atlantic Water Inflow
to the Northern Seas: Insights from Model Experiments .................. 111
Michael Karcher, Ruediger Gerdes, and Frank Kauker
vii
viii Contents
6 Climatic Importance of Large-Scale and Mesoscale
Circulation in the Lofoten Basin Deduced
from Lagrangian Observations ............................................................ 131
Jean-Claude Gascard and Kjell Arne Mork
7 Freshwater Storage in the Northern Ocean
and the Special Role of the Beaufort Gyre .......................................... 145
Eddy Carmack, Fiona McLaughlin, Michiyo
Yamamoto-Kawai, Motoyo Itoh, Koji Shimada, Richard Krishfield,
and Andrey Proshutinsky
8 Modelling the Sea Ice Export Through Fram Strait .......................... 171
Torben Koenigk, Uwe Mikolajewicz, Helmuth Haak,
and Johann Jungclaus
9 Fresh-Water Fluxes via Pacific and Arctic Outflows
Across the Canadian Polar Shelf.......................................................... 193
Humfrey Melling, Tom A. Agnew, Kelly K. Falkner,
David A. Greenberg, Craig M. Lee, Andreas Münchow,
Brian Petrie, Simon J. Prinsenberg, Roger M. Samelson,
and Rebecca A. Woodgate
10 The Arctic–Subarctic Exchange Through
Hudson Strait ......................................................................................... 249
Fiammetta Straneo and François J. Saucier
11 Freshwater Fluxes East of Greenland ................................................. 263
Jürgen Holfort, Edmond Hansen, Svein Østerhus,
Stephen Dye, Steingrimur Jonsson, Jens Meincke,
John Mortensen, and Michael Meredith
12 The Changing View on How Freshwater Impacts
the Atlantic Meridional Overturning Circulation .............................. 289
Michael Vellinga, Bob Dickson, and Ruth Curry
13 Constraints on Estimating Mass, Heat and Freshwater
Transports in the Arctic Ocean: An Exercise ..................................... 315
Bert Rudels, Marika Marnela, and Patrick Eriksson
14 Variability and Change in the Atmospheric Branch
of the Arctic Hydrologic Cycle ............................................................. 343
Mark C. Serreze, Andrew P. Barrett, and Andrew G. Slater
Contents ix
15 Simulating the Terms in the Arctic
Hydrological Budget .............................................................................. 363
Peili Wu, Helmuth Haak, Richard Wood,
Johann H. Jungclaus, and Tore Furevik
16 Is the Global Conveyor Belt Threatened by Arctic
Ocean Fresh Water Outflow? ............................................................... 385
E. Peter Jones and Leif G. Anderson
17 Simulating the Long-Term Variability of Liquid
Freshwater Export from the Arctic Ocean ......................................... 405
Rüdiger Gerdes, Michael Karcher, Cornelia Köberle,
and Kerstin Fieg
18 The Overflow Transport East of Iceland ............................................ 427
Svein Østerhus, Toby Sherwin, Detlef Quadfasel,
and Bogi Hansen
19 The Overflow Flux West of Iceland: Variability,
Origins and Forcing ............................................................................... 443
Bob Dickson, Stephen Dye, Steingrímur Jónsson,
Armin Köhl, Andreas Macrander, Marika Marnela,
Jens Meincke, Steffen Olsen, Bert Rudels,
Héðinn Valdimarsson, and Gunnar Voet
20 Tracer Evidence of the Origin and Variability
of Denmark Strait Overflow Water ..................................................... 475
Toste Tanhua, K. Anders Olsson, and Emil Jeansson
21 Transformation and Fate of Overflows in the Northern
North Atlantic ........................................................................................ 505
Igor Yashayaev and Bob Dickson
22 Modelling the Overflows Across
the Greenland–Scotland Ridge ............................................................. 527
Johann H. Jungclaus, Andreas Macrander, and Rolf H. Käse
23 Satellite Evidence of Change in the Northern Gyre ........................... 551
Sirpa Häkkinen, Hjálmar Hátún, and Peter Rhines
24 The History of the Labrador Sea Water: Production,
Spreading, Transformation and Loss .................................................. 569
Igor Yashayaev, N. Penny Holliday, Manfred Bersch,
and Hendrik M. van Aken
x Contents
25 Convective to Gyre-Scale Dynamics: Seaglider Campaigns
in the Labrador Sea 2003–2005 ............................................................ 613
Charles C. Eriksen and Peter B. Rhines
26 Convection in the Western North Atlantic Sub-Polar Gyre:
Do Small-Scale Wind Events Matter? ................................................. 629
Robert S. Pickart, Kjetil Våge, G.W.K. Moore,
Ian A. Renfrew, Mads Hvid Ribergaard, and Huw C. Davies
27 North Atlantic Deep Water Formation
in the Labrador Sea, Recirculation Through
the Subpolar Gyre, and Discharge
to the Subtropics .................................................................................... 653
Thomas Haine, Claus Böning, Peter Brandt,
Jürgen Fischer, Andreas Funk, Dagmar Kieke,
Erik Kvaleberg, Monika Rhein, and Martin Visbeck
28 Accessing the Inaccessible: Buoyancy-Driven Coastal
Currents on the Shelves of Greenland
and Eastern Canada .............................................................................. 703
Sheldon Bacon, Paul G. Myers, Bert Rudels,
and David A. Sutherland
List of Contributors ....................................................................................... 723
Index ................................................................................................................ 731
Arctic–Subarctic Ocean Fluxes: Defining
the Role of the Northern Seas in Climate
A General Introduction
Bob Dickson1, Jens Meincke2, and Peter Rhines3
1 Background
Almost 100 years ago, Helland-Hansen and Nansen (1909) produced the first com-
plete description of the pattern of oceanic exchanges that connect the North Atlantic
with the Arctic Ocean through subarctic seas. At a stroke, they placed the science
of the Nordic seas on an astonishingly modern footing; as Blindheim and Østerhus
(2005) put it, ‘Their work described the sea in such detail and to such precision
that investigations during succeeding years could add little to their findings’.
Nonetheless, in the century that followed, oceanographers have gradually persisted
in the two tasks that were largely inaccessible to the early pioneers – quantifying
the exchanges of heat, salt and mass through subarctic seas and, piecing-together
evidence for the longer-term (decade to century) variability of the system.
Evidence of variability was not long in coming. As hydrographic time series
lengthened into the middle decades of the 20th century, they began to capture
evidence of one of the largest and most widespread regime shifts that has ever
affected our waters. For these were the decades of “the warming in the north”,
when the salinity of North Atlantic Water passing through the Faroe–Shetland
Channel reached a century-long high (Dooley et al. 1984), when salinities were so
high off Cape Farewell that they were thrown out as erroneous (Harvey 1962),
when a precipitous warming of more than 2 °C in the 5-year mean pervaded the
West Greenland banks, and when the northward dislocations of biogeographical
boundaries for a wide range of species from plankton to commercially important
fish, terrestrial mammals and birds were at their most extreme in the 20th century
(reviewed in Dickson 2002).
1 Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, Suffolk NR33 0HT UK
2 University of Hamburg, Centre of Marine and Climate Research, D-20146 Hamburg, Germany
3 Department of Oceanography and Atmospheric Sciences, University of Washington, Seattle,
WA 98195, USA
R.R. Dickson et al. (eds.), Arctic–Subarctic Ocean Fluxes, 1–13 1
© Springer Science + Business Media B.V. 2008