The impact of climate oscillations on the surface energy budget over the Greenland Ice Sheet in a changing climate

Climate change is particularly strong in Greenland primarily as a result of changes in advection of heat and moisture fluxes from lower latitudes. The atmospheric structures involved influence the surface mass balance and their pattern are largely explained by climate oscillations which describe the internal climate variability. Based on a clustering method, we combine the Greenland Blocking Index and the North Atlantic Oscillation index with the vertically integrated water vapor to analyze inter-seasonal and regional impacts of the North Atlantic influence on the surface energy components over the Greenland Ice Sheet. In comparison to the reference period (1959–1990), the atmosphere has become warmer and moister during recent decades (1991–2020) for contrasting atmospheric circulation patterns. Particularly in the northern regions, increases in tropospheric water vapor enhance incoming longwave radiation and thus contribute to surface warming. Surface warming is most evident in winter, although its magnitude and spatial extent depend on the prevailing atmospheric configuration. Relative to the reference period, increases in sensible heat flux in the summer ablation zone are found irrespective of the atmospheric circulation pattern. Especially in the northern ablation zone, these are explained by the stronger katabatic winds which are partly driven by the larger surface pressure gradients between the ice/snow-covered surface and adjacent seas, and by the larger temperature gradient between near-surface air and the air above. Increases in net shortwave radiation are mainly connected to high-pressure systems. Whereas in the southern part of Greenland the atmosphere has gotten optical thinner, thus allowing more incoming shortwave radiation to reach the surface, in the northern part the incoming shortwave radiation flux has changed little with respect to the reference period, but the surface albedo decreased due to the expansion of the bare ice area.

Influence of Weather Conditions and Climate Oscillations on the Pine Looper Bupalus piniaria (L.) Outbreaks in the Forest-Steppe of the West Siberian Plain

The pine looper Bupalus piniaria (L.) is one of the most common pests feeding on the Scots pine Pinus sylvestris L. Pine looper outbreaks show a feature of periodicity and have significant ecological and economic impacts. Climate and weather factors play an important role in pine looper outbreak occurrence. We tried to determine what weather conditions precede B. piniaria outbreaks in the southeast of the West Siberian Plain and what climate oscillations cause them. Due to the insufficient duration and incompleteness of documented observations on outbreaks, we used the history of pine looper outbreaks reconstructed using dendrochronological data. Using logistic regression, we found that the factor influencing an outbreak the most is the weather four years before it. A combination of warm spring, dry summer, and cool autumn triggers population growth. Summer weather two years before an outbreak is also critical: humidity higher than the average annual value in summer is favorable for the pine looper. The logistic regression model predicted six out of seven outbreaks that occurred during the period for which weather data are available. We discovered a link between outbreaks and climatic oscillations (mainly for the North Atlantic oscillation, Pacific/North America index, East Atlantic/Western Russia, West Pacific, and Scandinavian patterns). However, outbreak predictions based on the teleconnection patterns turned out to be unreliable. We believe that the complexity of the interaction between large-scale atmospheric processes makes the direct influence of individual oscillations on weather conditions relatively small. Furthermore, climate changes in recent decades modulated atmospheric processes changing the pattern predicting pine looper outbreaks: Autumn became warmer four years before an outbreak, and summer two years before became drier.

What Goes Up Must Come Down: The Influence of Climate on Caribou Populations

Wildlife populations naturally go up and down. Oscillation is the term used for this pattern of highs (when there are many animals) and lows (when there are few). When the number of births is greater than the number of deaths, then populations grow. If deaths exceed births, populations decline. Caribou in the Arctic have dramatic population oscillations. The number of caribou can grow very high and also decrease to very few. Large-scale, long-lasting weather oscillations are one reason for this pattern. Knowledge of the connection between wildlife populations and climate oscillations is important to help conserve species like caribou and to better understand how climate change will impact wildlife.

Methane emissions from lake Onego sediments

We studied the methane content in Lake Onego bottom sediments and bottom water and revealed a wide variation of its concentrations among different parts of the lake. Methane concentrations were the highest in the pockmarked area of Petrozavodsk Bay, where hydrocarbon gases rise to the lake bed surface from the depth. Methane emissions from Lake Onego sediments were estimated. We show that in addition to the geological and geomorphological characteristics of the basin, the flux rate depends on how the lake sediments are forming under the uneven human pressure and climate oscillations of today.

Decadal Climate Oscillations, Synoptic Variability, and Ice Core Climate Proxy Records in the Ross Sea Region, Antarctica

<p>This thesis investigates synoptic variability in the Ross Sea region, Antarctica and develops geochemical proxies of this variability from an ice core record in Southern Victoria Land. Particular focus is given to the influence of decadal climate oscillations on synoptic conditions and potential records of these oscillations in ice core proxy records as long-­‐term records of these oscillations are important for understanding future climate change. I present an investigation of the joint influence of the El Niño Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) on variability in the Amundsen Sea Low (ASL), a dominant climatological feature that strongly influences the weather in the Ross Sea region. It is shown that the positive phase of each oscillation is associated with significant strengthening of the ASL, while negative phases are associated with a weakening. Through regression analysis I show that a simple linear combination of indices representing these oscillations can explain more than 40% of the geopotential height variance in the AS region at a seasonal scale and over 70% of the variance at an annual scale. These results are consistent with the known mechanisms of ENSO and SAM interaction in the region and show that while SAM is dominant hemispherically, ENSO is only influential in the Pacific Sector. Finally it is demonstrated that a simple model of linear reinforcement and interference between the oscillations describes their influence on the variability in the ASL better than models incorporating more complex interactions. Atmospheric back-­‐trajectory modeling and cluster analysis are used to investigate synoptic variability at the Gawn Ice Piedmont (GIP) ice core site in the Ross Sea Region, Antarctica. I identify two dominant air-­‐mass trajectory clusters: oceanic – cyclonic and continental trajectories. My analysis shows that oceanic – cyclonic trajectories peak during April (southern hemisphere winter), while continental trajectories reach their maximum during December (summer). A causal association is demonstrated between ENSO and the frequency of oceanic – cyclonic trajectories originating from the Ross Sea region. In contrast, it is shown that the Southern Annular Mode has little influence on the frequency of cyclonic clusters. I then develop proxy records for the synoptic variability using a shallow firn core from the GIP site containing 8 years of geochemical record. Continental trajectories correlate with concentrations of nitrate (NO3), which is sourced from stratospheric air-­‐masses descending over the Antarctic interior. Oceanic – cyclonic trajectory clusters strongly correlate with deuterium excess at seasonal and inter-­‐annual scales, a proxy sensitive to changes in relative humidity and sea surface temperature (SST) in the in the Ross and Amundsen Seas. Decadal variability in the frequency of oceanic – cyclonic trajectories is discussed with respect to ENSO, SAM, and changes in SST and sea ice extent.</p>

Decadal Climate Oscillations, Synoptic Variability, and Ice Core Climate Proxy Records in the Ross Sea Region, Antarctica

<p>This thesis investigates synoptic variability in the Ross Sea region, Antarctica and develops geochemical proxies of this variability from an ice core record in Southern Victoria Land. Particular focus is given to the influence of decadal climate oscillations on synoptic conditions and potential records of these oscillations in ice core proxy records as long-­‐term records of these oscillations are important for understanding future climate change. I present an investigation of the joint influence of the El Niño Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) on variability in the Amundsen Sea Low (ASL), a dominant climatological feature that strongly influences the weather in the Ross Sea region. It is shown that the positive phase of each oscillation is associated with significant strengthening of the ASL, while negative phases are associated with a weakening. Through regression analysis I show that a simple linear combination of indices representing these oscillations can explain more than 40% of the geopotential height variance in the AS region at a seasonal scale and over 70% of the variance at an annual scale. These results are consistent with the known mechanisms of ENSO and SAM interaction in the region and show that while SAM is dominant hemispherically, ENSO is only influential in the Pacific Sector. Finally it is demonstrated that a simple model of linear reinforcement and interference between the oscillations describes their influence on the variability in the ASL better than models incorporating more complex interactions. Atmospheric back-­‐trajectory modeling and cluster analysis are used to investigate synoptic variability at the Gawn Ice Piedmont (GIP) ice core site in the Ross Sea Region, Antarctica. I identify two dominant air-­‐mass trajectory clusters: oceanic – cyclonic and continental trajectories. My analysis shows that oceanic – cyclonic trajectories peak during April (southern hemisphere winter), while continental trajectories reach their maximum during December (summer). A causal association is demonstrated between ENSO and the frequency of oceanic – cyclonic trajectories originating from the Ross Sea region. In contrast, it is shown that the Southern Annular Mode has little influence on the frequency of cyclonic clusters. I then develop proxy records for the synoptic variability using a shallow firn core from the GIP site containing 8 years of geochemical record. Continental trajectories correlate with concentrations of nitrate (NO3), which is sourced from stratospheric air-­‐masses descending over the Antarctic interior. Oceanic – cyclonic trajectory clusters strongly correlate with deuterium excess at seasonal and inter-­‐annual scales, a proxy sensitive to changes in relative humidity and sea surface temperature (SST) in the in the Ross and Amundsen Seas. Decadal variability in the frequency of oceanic – cyclonic trajectories is discussed with respect to ENSO, SAM, and changes in SST and sea ice extent.</p>