The Early Twentieth-Century Warming in the Arctic—A Possible Mechanism

The huge warming of the Arctic that started in the early 1920s and lasted for almost two decades is one of the most spectacular climate events of the twentieth century. During the peak period 1930–40, the annually averaged temperature anomaly for the area 60°–90°N amounted to some 1.7°C. Whether this event is an example of an internal climate mode or is externally forced, such as by enhanced solar effects, is presently under debate. This study suggests that natural variability is a likely cause, with reduced sea ice cover being crucial for the warming. A robust sea ice–air temperature relationship was demonstrated by a set of four simulations with the atmospheric ECHAM model forced with observed SST and sea ice concentrations. An analysis of the spatial characteristics of the observed early twentieth-century surface air temperature anomaly revealed that it was associated with similar sea ice variations. Further investigation of the variability of Arctic surface temperature and sea ice cover was performed by analyzing data from a coupled ocean–atmosphere model. By analyzing climate anomalies in the model that are similar to those that occurred in the early twentieth century, it was found that the simulated temperature increase in the Arctic was related to enhanced wind-driven oceanic inflow into the Barents Sea with an associated sea ice retreat. The magnitude of the inflow is linked to the strength of westerlies into the Barents Sea. This study proposes a mechanism sustaining the enhanced westerly winds by a cyclonic atmospheric circulation in the Barents Sea region created by a strong surface heat flux over the ice-free areas. Observational data suggest a similar series of events during the early twentieth-century Arctic warming, including increasing westerly winds between Spitsbergen and Norway, reduced sea ice, and enhanced cyclonic circulation over the Barents Sea. At the same time, the North Atlantic Oscillation was weakening.

[1]  George C. Reid,et al.  Solar total irradiance variations and the global sea surface temperature record , 1991 .

[2]  J. Räisänen.  CO2-Induced Changes in Interannual Temperature and Precipitation Variability in 19 CMIP2 Experiments , 2002 .

[3]  E. Friis-christensen,et al.  Length of the Solar Cycle: An Indicator of Solar Activity Closely Associated with Climate , 1991, Science.

[4]  F. Joos,et al.  Long‐term variability of the terrestrial and oceanic carbon sinks and the budgets of the carbon isotopes 13C and 14C , 1998 .

[5]  J. Hurrell,et al.  The Arctic Ocean Response to the North Atlantic Oscillation , 2000 .

[6]  T. Delworth,et al.  Simulation of early 20th century global warming , 2000, Science.

[7]  Douglas V. Hoyt,et al.  A discussion of plausible solar irradiance variations, 1700-1992 , 1993 .

[8]  Cecilia M. Bitz,et al.  Dynamics of Recent Climate Change in the Arctic , 2002, Science.

[9]  J. Kahl,et al.  Absence of evidence for greenhouse warming over the Arctic Ocean in the past 40 years , 1993, Nature.

[10]  L. Bengtsson,et al.  Forcing of Northern Hemisphere Climate Trends , 2003 .

[11]  J. Hurrell.  Influence of variations in extratropical wintertime teleconnections on northern hemisphere temperature , 1996 .

[12]  U. Cubasch,et al.  Simulation of the influence of solar radiation variations on the global climate with an ocean-atmosphere general circulation model , 1997 .

[13]  L. Bengtsson.  Uncertainties of Global Climate Predictions , 2001 .

[14]  M. Hoerling,et al.  Tropical Origins for Recent North Atlantic Climate Change , 2001, Science.

[15]  Paul Skeie,et al.  Meridional flow variability over the Nordic Seas in the Arctic oscillation framework , 2000 .

[16]  J. Walsh,et al.  An Analysis of Arctic Sea Ice Fluctuations, 1953–77 , 1979 .

[17]  J. Beer,et al.  The role of the sun in climate forcing , 2000 .

[18]  L. Mysak,et al.  Decadal climate oscillations in the Arctic: A new feedback loop for atmosphere‐ice‐ocean interactions , 1998 .

[19]  Klaus Hasselmann,et al.  Multi-pattern fingerprint method for detection and attribution of climate change , 1997 .

[20]  Seelye Martin,et al.  Variations in Surface Air Temperature Observations in the Arctic, 1979-97. , 2000 .

[21]  Claus Fröhlich,et al.  The Sun's total irradiance: Cycles, trends and related climate change uncertainties since 1976 , 1998 .

[22]  T. Furevik.  Annual and interannual variability of Atlantic Water temperatures in the Norwegian and Barents Seas : 1980-1996 , 2001 .

[23]  Carl Wunsch,et al.  The Interpretation of Short Climate Records, with Comments on the North Atlantic and Southern Oscillations , 1999 .

[24]  P. Jones,et al.  Variations in Surface Air Temperatures: Part 2. Arctic Regions, 1881–1980 , 1982 .

[25]  Rajmund Przybylak,et al.  Temporal and spatial variation of surface air temperature over the period of instrumental observations in the Arctic , 2000 .

[26]  I. Polyakov,et al.  Atmospheric patterns forcing two regimes of arctic circulation: A return to anticyclonic conditions? , 1999 .

[27]  K. Hasselmann,et al.  Arctic climate change – observed and modeled temperature and sea ice , 2004 .

[28]  J. Hansen,et al.  Radiative forcing and climate response , 1997 .

[29]  K. Trenberth,et al.  The Northern Hemisphere Sea-Level Pressure Data Set: Trends, Errors and Discontinuities , 1980 .

[30]  N. Rayner,et al.  Version 2.2 of the Global sea-Ice and Sea Surface Temperature Data Set , 1996 .

[31]  John E. Walsh,et al.  Arctic Sea Ice Variability in the Context of Recent Atmospheric Circulation Trends , 2000 .

[32]  B. Ådlandsvik,et al.  Water fluxes through the Barents Sea , 1997 .

[33]  U. Cubasch,et al.  The Influence of Total Solar Irradiance on Climate , 2000 .

[34]  R. Toresen,et al.  Variation in abundance of Norwegian spring‐spawning herring (Clupea harengus, Clupeidae) throughout the 20th century and the influence of climatic fluctuations , 2000 .

[35]  John F. B. Mitchell,et al.  Causes of twentieth-century temperature change near the Earth's surface , 1999, Nature.

[36]  I. Polyakov,et al.  Variability and Trends of Air Temperature and Pressure in the Maritime Arctic, 1875–2000 , 2003 .

[37]  I. Polyakov,et al.  Arctic decadal and interdecadal variability , 2000 .

[38]  Konrad A Hughen,et al.  Arctic Environmental Change of the Last Four Centuries , 1997 .

[39]  K. Hasselmann,et al.  Arctic climate change: observed and modelled temperature and sea-ice variability , 2004 .

[40]  L. Bengtsson,et al.  Modes of the wintertime Arctic temperature variability , 2003 .

[41]  David Rind,et al.  Climate Forcing by Changing Solar Radiation , 1998 .

[42]  I. Polyakov,et al.  Long-Term Ice Variability in Arctic Marginal Seas , 2003 .

[43]  M. Ikeda.  Decadal oscillations of the air‐ice‐ocean system in the Northern Hemisphere , 1990 .

[44]  L. Mysak.  Patterns of Arctic Circulation , 2001, Science.

[45]  P. Haugan,et al.  Heat budgets of the Arctic Mediterranean and sea surface heat flux parameterizations for the Nordic Seas , 1996 .

[46]  Donald J. Cavalieri,et al.  Arctic sea ice extents, areas, and trends, 1978-1996 , 1999 .

[47]  A. Robock.  Volcanic eruptions and climate , 2000 .

[48]  Lennart Bengtsson,et al.  Transient Climate Change Simulations with a Coupled Atmosphere–Ocean GCM Including the Tropospheric Sulfur Cycle , 1999 .

[49]  V. F. Zakharov.  SEA ICE IN THE CLIMATE SYSTEM , 2003 .

[50]  I. Polyakov,et al.  Observationally based assessment of polar amplification of global warming , 2002 .

[51]  J. Wang,et al.  Hypersensitive decadal oscillations in the Arctic/Subarctic climate , 2001 .

[52]  L. Mysak,et al.  Sea-ice anomalies observed in the Greenland and Labrador seas during 1901–1984 and their relation to an interdecadal Arctic climate cycle , 1990 .

[53]  John E. Walsh,et al.  Recent Variations of Sea Ice and Air Temperature in High Latitudes , 1993 .

[54]  M. Claussen,et al.  The atmospheric general circulation model ECHAM-4: Model description and simulation of present-day climate , 1996 .

[55]  W. Oechel,et al.  Observational Evidence of Recent Change in the Northern High-Latitude Environment , 2000 .

[56]  R. Curry,et al.  Ocean Gyre Circulation Changes Associated with the North Atlantic Oscillation , 2001 .

[57]  H. Goosse,et al.  A mechanism of decadal variability of the sea-ice volume in the Northern Hemisphere , 2002 .

[58]  R. Voss,et al.  Multi-fingerprint detection and attribution analysis of greenhouse gas, greenhouse gas-plus-aerosol and solar forced climate change , 1997 .

[59]  Makiko Sato,et al.  GISS analysis of surface temperature change , 1999 .

[60]  J. Lean,et al.  Reconstruction of solar irradiance since 1610: Implications for climate change , 1995 .

[61]  Lennart Bengtsson,et al.  Why is the global warming proceeding much slower than expected , 1999 .

[62]  P. Stott,et al.  External control of 20th century temperature by natural and anthropogenic forcings. , 2000, Science.

[63]  Michael E. Mann,et al.  Observed and Simulated Multidecadal Variability in the Northern Hemisphere , 1999 .

[64]  Seelye Martin,et al.  Recent observations of a spring‐summer surface warming over the Arctic Ocean , 1997 .

[65]  L. Mysak,et al.  Is There a Dominant Timescale of Natural Climate Variability in the Arctic , 2000 .

[66]  Mark New,et al.  Surface air temperature and its changes over the past 150 years , 1999 .

[67]  J. Hurrell.  Decadal Trends in the North Atlantic Oscillation: Regional Temperatures and Precipitation , 1995, Science.