V. Ch. Khon

Connection between Eurasian and North Atlantic climate anomalies and natural variations in the Atlantic thermohaline circulation based on long-term model calculations

We obtained estimates of the correlation between regional characteristics of the climate in Eurasia and the North Atlantic and the Atlantic thermohaline circulation (ATHC) based on the results of calculations using the ocean‐atmosphere global climate model (OAGCM) without external forcing (reference numerical experiment) for the period of 500 yr. The regions of statistically significant correlation between the ATHC variations in a few decades with the anomalies of surface air temperature, pressure at sea level, and precipitation in different seasons were distinguished. The most significant correlation was found in the winter period. A correlation was also found between the ATHC and the intensity of the Iceland minimum of the atmospheric action center (AC) [1], which has a strong influence on the weather conditions in Europe. The Atlantic thermohaline circulation, which shows a large-scale North Atlantic meridional overturning circulation (NAMOC) and represents a part of the global 3D oceanic current (conveyor belt) [2, 3], plays an important role in heat transfer to high latitudes of the Northern Hemisphere. The intensity of the ATHC shows strong long-period fluctuations accompanied by anomalies in the ocean surface temperature (OST) in the North Atlantic [4] and variations in the area of the Arctic ice cover [5]. This fact evidences the existence of

The hydrological regime of large river basins in Northern Eurasia in the XX–XXI centuries

The ability of present-day climate models to reproduce the mean annual regime of river runoff and its within-year distribution is evaluated for major Eurasian basins, including the basins of the Volga and Amur and the major Siberian rivers: the Ob, Yenisei, and Lena. Estimates are made for possible variations in seasonal runoff and characteristics of daily precipitation (the amount, rate, and probability) in drainage areas for the late XXI century. The analysis involved the use of the results of calculations by climatic general circulation models carried out under international Coupled Model Intercomparison Project.

Arctic climate changes and possible conditions of Arctic navigation in the 21st century

Assessments of current and expected climatic changes in the Arctic Basin are obtained, including ice-cover characteristics influencing the duration of the navigation season on the Northern Sea Route (NSR) along Eurasia and the Northwest Passage (NWP) along North America. The ability of modern climate models to simulate the average duration of the navigation season and its changes over recent decades is estimated. The duration of the navigation season for the NSR and NWP in the 21st century is estimated using an ensemble of climate models. The assessments differ significantly for the NSR and NWP. Unlike the NSR, the NWP reveals no large changes in the navigation season in the first 30 years of the 21st century. From the multimodel simulations, the expected duration of the navigation period by the late 21st century will be approximately 3 to 6 months for the NSR and 2 to 4 months for the NWP under the moderate anthropogenic SRES-A1B scenario.

Model estimates for the sensitivity of atmospheric centers of action to global climate changes

The sensitivity of the characteristics of atmospheric centers of action (ACAs) in the Northern Hemisphere to global climate changes is analyzed on the basis of models of different complexity, including the climate model of intermediate complexity of the Institute of Atmospheric Physics, Russian Academy of Sciences and the ECHAM4/OPYC3 and HadCM3 general circulation models of the atmosphere and ocean. The emphasis is on the analysis of trends of the change in ACA characteristics in winter, when the long-term global warming is most considerable. The global climate models are shown to be able to describe not only the intermediate regimes of ACAs but also their dynamics. In particular, ECHAM4/OPYC3 is capable of reproducing the statistically significant connection of the characteristics of the North Pacific centers of action with El Niño/La Niña events, revealed from observational data. With the use of the results of the global climate models, the possible changes in the characteristics of centers of action in the 21st century are estimated for an increased content of greenhouse gases in the atmosphere.

Possible regional changes in precipitation regimes in northern Eurasia in the 21st century

Possible changes in various characteristics of precipitation (its amount, intensity, probability of days with precipitation, and its extreme regimes) in the regions of northern Eurasia in the 21st century are assessed. The data for the analysis were obtained from simulations using global climatic models: atmosphere-ocean general circulation model ECHAM5/MPI-OM and an intermediate-complexity model developed in the Institute of Atmospheric Physics, RAS. The simulations were performed for the SRES-A2 and SRES-B1 scenarios of anthropogenic emission of greenhouse gases into the atmosphere. The results obtained from models of two generations, i.e., ECHAM5/MPI-OM and ECHAM4/OPYC3, models were compared. Detailed analysis was performed for the basins of largest Siberian rivers, the Volga River, and the Caucasian region.

Estimating changes of wind-wave activity in the arctic ocean in the 21st century using the regional climate model

The present communication deals with analysis of possible changes in windandwave activity of the Arc� tic Basin in the 21st century using the wind wave model and calculations of climatic changes, with anthropogenic effects taken into account. Estimates of the possible increase in extreme sea waves in different water areas, against the background of general intensi� fication of sea swell in the Arctic Basin, are obtained (1). The comparative estimates of the role played by reduction of sea ice areas, with respective increase in the fetch and change of nearsurface wind, in the for� mation of changes of the sea swell in Arctic seas are given.

New model estimates of changes in the duration of the navigation period for the Northern Sea Route in the 21st century

New estimates of changes in the duration of the navigation period for the Northern Sea Route (NSR) are obtained based on calculations with the current generation of global climate models under moderate anthropogenic impacts in the 21st century. In order to obtain more reliable estimates, it was analyzed whether or not the present climate models can simulate both the average conditions of sea ice and their interannual variation and tendencies to change in the Arctic basin, in particular on the NSR, as compared to the satellite data for recent decades.

Ladoga and Onega Hydrological Regimes and Their Variations

The characteristics of the Ladoga and Onega hydrological regimes were analyzed, and the features of the annual and long-term variations in their water balance components were determined. The statistically significant positive trends of the average annual precipitation and evaporation in the Ladoga water area and the water inflow for the period of 1932–1995 were determined. The relative effect of the Ladoga water balance components on the formation of its level was studied. Spectral analysis of the components of this balance revealed, in particular, characteristic periods of about four years in the last decades. Based on the analysis, including wavelet, of the longer series of long-term variations in the Ladoga water level, it was found that the spectral structure pronouncedly changed in the period from 1859 to 1995.

Variations in the Duration of the Navigation Period along the Northern Sea Route in the 21st Century Based on Simulations with an Ensemble of Climatic Models: Bayesian Estimates

As global warming continues in the 21st century, one can expect a significant increase in the duration of the navigation period along the Northern Sea Route. In this study we found that, according to the representative concentration pathways 4.5 and 8.5 scenarios of the anthropogenic impact, the expected duration of the navigation period along the Northern Sea Route in the middle of the 21st century would be two to three months and three to six months by the end of the century.

Variations of temperature and hydrologic regimes of the region of Ladoga Lake catchment basin in the 20th and 21st centuries according to data of modern climate models

In the region of the Ladoga Lake catchment basin, we perform data analysis on a set of different modern climate models with different Intergovernmental Panel on Climate Change (IPCC) scenarios in the 20th and 21st centuries; this set includes global models such as ECHAM4/OPYC3 (Max Planck Institute for Meteorology, Germany), HadCM3 (Hadley Centre Coupled Model, England), and RCAO (Rossby Centre Regional Atmosphere-Ocean) models. Two variants of the boundary conditions for these climate models (Rossby Center of Swedish Meteorological and Hydrological Institute, SMHI) are used. We present the results of a diagnosis of the model-predicted near-surface temperature (T), precipitation (P), evaporation (E), and water budget (P-E) in the Ladoga Lake catchment based on their comparison with empirical data in twentieth century. We obtain scenario estimates of the variations of temperature and hydrologic regimes of Ladoga Lake catchment when IPCC IS92a, A2, and B2 scenarios are fulfilled, describing the prognostic growth of anthropogenic emissions of greenhouse gases and aerosol to the atmosphere, and discuss the recommendations for their use.