Ivan E. Frolov

One more step toward a warmer Arctic

This study was motivated by a strong warming signal seen in mooring-based and oceanographic survey data collected in 2004 in the Eurasian Basin of the Arctic Ocean. The source of this and earlier Arctic Ocean changes lies in interactions between polar and sub-polar basins. Evidence suggests such changes are abrupt, or pulse-like, taking the form of propagating anomalies that can be traced to higher-latitudes. For example, an anomaly found in 2004 in the eastern Eurasian Basin took ∼1.5 years to propagate from the Norwegian Sea to the Fram Strait region, and additional ∼4.5–5 years to reach the Laptev Sea slope. While the causes of the observed changes will require further investigation, our conclusions are consistent with prevailing ideas suggesting the Arctic Ocean is in transition towards a new, warmer state.

Arctic Ocean Warming Contributes to Reduced Polar Ice Cap

Analysis of modern and historical observations demonstrates that the temperature of the intermediate-depth (150–900 m) Atlantic water (AW) of the Arctic Ocean has increased in recent decades. The AW warming has been uneven in time; a local 1°C maximum was observed in the mid-1990s, followed by an intervening minimum and an additional warming that culminated in 2007 with temperatures higher than in the 1990s by 0.24°C. Relative to climatology from all data prior to 1999, the most extreme 2007 temperature anomalies of up to 1°C and higher were observed in the Eurasian and Makarov Basins. The AW warming was associated with a substantial (up to 75–90 m) shoaling of the upper AW boundary in the central Arctic Ocean and weakening of the Eurasian Basin upper-ocean stratification. Taken together, these observations suggest that the changes in the Eurasian Basin facilitated greater upward transfer of AW heat to the ocean surface layer. Available limited observations and results from a 1D ocean column model support this surmised upward spread of AW heat through the Eurasian Basin halocline. Experiments with a 3D coupled ice–ocean model in turn suggest a loss of 28–35 cm of ice thickness after 50 yr in response to the 0.5 W m−2 increase in AW ocean heat flux suggested by the 1D model. This amount of thinning is comparable to the 29 cm of ice thickness loss due to local atmospheric thermodynamic forcing estimated from observations of fast-ice thickness decline. The implication is that AW warming helped precondition the polar ice cap for the extreme ice loss observed in recent years.

Toward a warmer Arctic Ocean: Spreading of the early 21st century Atlantic Water warm anomaly along the Eurasian Basin margins

We document through the analysis of 2002–2005 observational data the recent Atlantic Water (AW) warming along the Siberian continental margin due to several AW warm impulses that penetrated into the Arctic Ocean through Fram Strait in 1999–2000. The AW temperature record from our long-term monitoring site in the northern Laptev Sea shows several events of rapid AW temperature increase totaling 0.8°C in February–August 2004. We hypothesize the along-margin spreading of this warmer anomaly has disrupted the downstream thermal equilibrium of the late 1990s to earlier 2000s. The anomaly mean velocity of 2.4–2.5 ± 0.2 cm/s was obtained on the basis of travel time required between the northern Laptev Sea and two anomaly fronts delineated over the Eurasian flank of the Lomonosov Ridge by comparing the 2005 snapshot along-margin data with the AW pre-1990 mean. The magnitude of delineated anomalies exceeds the level of pre-1990 mean along-margin cooling and rises above the level of noise attributed to shifting of the AW jet across the basin margins. The anomaly mean velocity estimation is confirmed by comparing mooring-derived AW temperature time series from 2002 to 2005 with the downstream along-margin AW temperature distribution from 2005. Our mooring current meter data corroborate these estimations.

Anomalous variations in the thermohaline structure of the Arctic Ocean

Introduction: In the last two decades, significant changes have occurred in the Arctic Ocean as well as in the entire Arctic region. The ice cover of Arctic seas, which was gradually (linearly) decreasing from the beginning of the 20th century to the end of it [1], began to shrink rapidly in the 1990s and in the 21st century [2]. Salinity variations in the upper layer changed sign in different regions [3]. The temperature of Atlantic waters in the Arctic basin started to increase. At the end of the 1990s, stabilization of Atlantic water transport to the Arctic Basin was observed [4], but starting from 2004, the temperature of Atlantic waters in the Eurasian sub-basin increased even more and reached values that had not been observed here previously [5]. In 2007, extreme summer processes in the Arctic that followed this increase and anomalous state of the ice cover and upper layer of the ocean that were formed by the beginning of autumn put forward a pressing problem to evaluate the variation in the thermohaline structure of the Arctic Ocean as a whole.

[the Arctic] Ocean temperature and salinity [in: State of the Climate in 2012]

Special supplement to the Bulletin of the American Meteorological Society vol.94, No. 8, August 2013

Russian-German collaboration in the arctic environmental research

The overview of the 20-years joint Russian-German multidisciplinary researches in the Arctic are represented in this article. Data were obtained during numerous marine and terrestrial expeditions, all-year-round measurements and observations. On the basis of modern research methods including satellite observation, radiocarbon (AMS 14C) dating of the Arctic sea sediments, isotope, biochemical and other methods, the new unique records were obtained. Special emphasis devoted to the latest data concerning modern sea-ice, ocean and sedimentation processes, evolution of the permafrost and paleoenvironments in the Laptev Sea System.

Possible causes of changes in climate and in Arctic Seas ice extent

Understanding the causes of climate change at different time scales is still at the stage of framing scientific hypotheses, and hence requires further detailed investigation. Unfortunately, since climate change is by definition, a long-term phenomenon, it is very difficult to prove or disprove hypotheses. We have an abundance of hypotheses and a dearth of detailed long-term data. Nevertheless, where data exist, we should prefer data to computer models. Most cyclic and secular variations in sea ice conditions are rooted in atmospheric and oceanic processes that are influenced by both external and internal factors. The external factors include such helio-and geophysical impacts as solar activity, tidal and nutation phenomena, Earth’s rotation speed, fluctuations in the solar constant due to changes in distance between the Earth and the Sun, fluxes of energy and charged particles from space, and other astronomical factors. Internal factors encompass natural hydrometeorological, geological, and biological processes and self-oscillation phenomena related to interactions in the lithosphere-ocean-sea ice-atmosphere-land system, with the latter including glaciers, rivers, etc. Anthropogenic factors or impacts that may augment internal system variables are associated with increased concentrations of greenhouse gases in the atmosphere and generation of black carbon soot and sulfate aerosols, due to human activities and their putative impact on climate.

Consistency among sea ice extent and atmospheric and hydrospheric processes

The variability and state of the Arctic sea ice cover strongly depend on atmospheric conditions as well as ocean dynamic and thermodynamic processes (Alekseev, 1976; Appel and Gudkovich, 1992; Gudkovich et al., 1972; Doronin, 1969; Doronin and Kheisin, 1975; Zakharov, 1981; Zubov, 1938, 1944; Shuleikin, 1953; Wadhams, 1994). A number of parameters influence the direction and intensity of these processes. The most significant are: the surface air temperature, wind, oceanic boundary layers and their stratification, and ocean circulation.

Variability of sea ice thickness and concentration in the twentieth century

Regular measurements of Arctic ice thickness began approximately in the middle of the 1930s in the vicinity of a number of polar stations, some of which were closed in the 1990s. To investigate the changes in landfast ice thickness for this study, we chose 11 stations with approximately equal lengths of observational time series. Five of these stations were located in the Kara Sea (Beliy Island, Dikson Island, Uyedineniya Island, Cape Sterlegov, and Cape Cheluskin), and the others in the Laptev Sea (Tiksi Bay, Kotel’ny Island, Sannikov Island), East-Siberian Sea (Cape Shalaurov, Chetyrekhstolbovoy Island) and in the Chukchi Sea (Wrangel Island).

Long-term changes in Arctic Seas ice extent during the twentieth century

In general, the geographical terminology used in this book follows the Russian definitions published in Anon. (O). Treshnikov et al. (1967) define the Arctic Basin as a “near-pole abyssal basin, restricted by the continental slope.” The Beaufort and Lincoln Seas are the marginal zones of the Arctic Basin. The North European Basin encompasses the Greenland, Norwegian, Barents, and White Seas as well as the Arctic Seas of Siberia (the Kara, Laptev, East Siberian, and Chukchi Seas). Baffin Bay, Davis and Smith Straits, Hudson Bay, and the straits of the Canadian Arctic archipelago compose the East Canadian region of the Arctic Ocean (e.g., Zakharov, 1996; Smirnov, 1974). Based on the major characteristics of the area’s ice regime, the Greenland, Iceland, Norwegian, Barents, and Kara Seas are collectively known as the Nordic Seas, as proposed by Vinje (1998).