Links between central Greenland stable isotopes, blocking and extreme climate variability over Europe at decadal to multidecadal time scales

The link between central Greenland stable oxygen isotopes, atmospheric blocking frequency and cold temperature extremes at decadal to multidecadal time scales is investigated using observed and proxy data as well as model experiments. A composite analysis reveals that positive stable isotope anomalies in central Greenland are associated with enhanced blocking activity in the Atlantic European region. Several indices of blocking activity in the Atlantic European region are higher correlated with central Greenland stable isotope time series than with the North Atlantic Oscillation indices both in observations and model simulation. Furthermore, the blocking frequency anomaly pattern associated with central Greenland stable isotope variability is similar to the blocking anomaly pattern associated with the Atlantic Multidecadal Oscillation. A composite analysis reveals that stable isotope variations in central Greenland are related to a large-scale pattern in the frequency of extreme low temperature events with significant positive anomalies over Europe and a southwest to northeast dipolar pattern over Asia. During observational period central Greenland isotope records, blocking and extreme temperature indices over Europe show enhanced variability 10–30 and 50–70 years. Similar quasi-periodicities dominate the spectrum of central Greenland isotope variability during the last millennium. We argue that long-term variations of climate extreme indices over Europe and Asia, as derived from observational data, can be put into a long-term perspective using central Greenland stable isotope ice core records

Spatiotemporal trend analysis of climate indices for the European continent

The objective of this study is to analyze and visualize the spatial distribution of trends for 74 climate indices on a monthly time-scale in direction, magnitude, and significance level at a resolution of 0.1° during the period of 1950–2021 over the European region. The Mann–Kendall and Sen’s slope estimators reveal that growing degree days with mean air temperature >4 °C (gd4) and heating degree days with mean air temperature <17 °C (hd17) show the largest increase (0.93 °C August) and decrease (1.03 °C July), respectively. The universal thermal climate index (utci), relative humidity (rh), wind chill index (wci), global radiation (bio20), and potential evapotranspiration (pet) are of significant importance due to higher correlation and magnitude of change. Country-specific zoning shows the highest warmer days during August experienced by Bosnia and Herzegovina (southeastern Europe) and lower colder days during January by Belarus (eastern Europe). High wind and high utci were experienced by Liechtenstein (southeastern Europe) region during July. The highest wci was experienced by San Marino (southern Europe) in June and Portugal (southern Europe) in March. Bio20 and rh decline were experienced by Russia (eastern Europe) and Moldova (southeastern Europe) in May and September, respectively. Results are useful to mitigate the risk associated with each of the climate indices for specific European regions

Climate signature of solar irradiance variations: Analysis of long-term instrumental, historical, and proxy data

The signature of solar irradiance variations on decadal-to-centennial climate variability is analyzed by means of statistical analysis of long-term instrumental, historical and proxy data sets. Solar variations associated with the Schwabe, Hale, and Gleissberg cycles are detected by their spatial patterns in sea surface temperature and seal level pressure. Different statistical methods of instrumental and proxy data show that the mode related to solar irradiance fluctuations on multidecadal timescales (Gleissberg cycle) is distinct from the Atlantic multidecadal mode associated to ocean circulation changes. From this, one can infer the degree to which solar variability has contributed to long-term temperature variations during the instrumental and pre-instrumental era

Shift in ENSO teleconnections recorded by a Red Sea coral

El Nino-Southern Oscillation (ENSO) teleconnections over Europe and the Middle East are evaluated using an oxygen isotope coral time series from the northern Red Sea and various instrumental data sets. We detect a shift in the correlation between the Nino3 index and the Red Sea coral record in 1970s and we show that this shift can be attributed to non-stationary circulation regimes and related ENSO teleconnections. We find that positive anomalies of oxygen isotope in the Red Sea coral record from mid-1930s to late 1960s are associated with a strong Pacific-North Atlantic teleconnection accompanied by a weak Aleutian Low, a more zonal flow at mid-latitudes, and La Nina conditions in tropical Pacific. In contrast, positive anomalous of oxygen isotopes in the Red Sea coral after 1970s are related to El Nino conditions and weaker Pan-Pacific-Atlantic circulation regimes. Using the window correlation of the northern Red Sea coral record with two coral records from the tropical and subtropical Pacific, we find non-stationary relationships between the tropical Pacific and the European/Middle Eastern climate during the pre-instrumental period. Our results imply that the modulation of teleconnections at interdecadal time scales provides a limitation in the prediction and reconstruction of remote climate phenomena such as the ENSO impact over Europe

Interannual to multidecadal Euro-Atlantic blocking variability during winter and its relationship with extreme low temperatures in Europe

The dominant modes of blocking frequency variability in the Atlantic-European region are evaluated for the 1871–2010 period. An Empirical Orthogonal Function (EOF) analysis of a two-dimensional blocking indicator field reveals three dominant EOFs, describing about 35% of interannual to multidecadal blocking variability. The first EOF captures an out-of-phase blocking frequency anomaly over Greenland and Western Europe regions. The corresponding principal component time series is strongly correlated with the North Atlantic Oscillation index, but shows also significant correlations with indices of the East Atlantic, Scandinavian and East Atlantic-Western Russia patterns. The second EOF shows a dominant center over the North Sea region as well as a less pronounced center with anomalies of the same sign over southeastern Greenland. The multidecadal variations of this mode of blocking variability are related with a basin wide North Atlantic sea surface temperature anomaly which projects partly on the Atlantic Multidecadal Oscillation (AMO). The third mode is an east–west dipole of blocking frequency anomalies from Scandinavian and southern Greenland regions and shows enhanced variability at ~20 year time scales. The coherent variations of the time coefficients of this pattern with open solar flux suggest a possible solar influence on blocking variability at these time scales. Furthermore the dominant patterns of blocking variability are related with distinct anomaly patterns in the occurrence of extreme low temperature events over Europe at interannual to multidecadal time-scales. AMO as well as the solar signals were detected also in the corresponding extreme low temperature blocking patterns. We argue that multivariate analysis of blocking indicators gives additional information about blocking and related extreme climate phenomena variability and predictability comparative with classical sectorial approach

A Synoptic Scale Perspective on Greenland Ice Core d18O Variability and Related Teleconnection Patterns

The variability of stable oxygen isotope ratios (δ18O) from Greenland ice cores is commonly linked to changes in local climate and associated teleconnection patterns. In this respect, in this study we investigate ice core δ18O variability from a synoptic scale perspective to assess the potential of such records as proxies for extreme climate variability and associated weather patterns. We show that positive (negative) δ18O anomalies in three southern and central Greenland ice cores are associated with relatively high (low) Rossby Wave Breaking (RWB) activity in the North Atlantic region. Both cyclonic and anticyclonic RWB patterns associated with high δ18O show filaments of strong moisture transport from the Atlantic Ocean towards Greenland. During such events, warm and wet conditions are recorded over southern, western and central part of Greenland. In the same time the cyclonic and anticyclonic RWB patterns show enhanced southward advection of cold polar air masses on their eastern side, leading to extreme cold conditions over Europe. The association between high δ18O winters in Greenland ice cores and extremely cold winters over Europe is partly explained by the modulation of the RWB frequency by the tropical Atlantic sea surface temperature forcing, as shown in recent modeling studies. We argue that δ18O from Greenland ice cores can be used as a proxy for RWB activity in the Atlantic European region and associated extreme weather and climate anomalies

Arctic Oscillation signature in a Red Sea coral

We show that the winter time series of the Ras Umm Sidd coral oxygen isotope record from the northern Red Sea (approximately 28 N) is linked to the Arctic Oscillation phenomenon, the Northern Hemisphere's dominant mode of atmospheric variability. Until now, the detection of this mode, which is most prominent in winter, in proxy climate records was difficult due to the lack of a clear seasonality in most paleoclimatic archives. The results suggest that northern Red Sea corals can provide information about the low-frequency variability of the Northern Hemisphere winter circulation during the pre-instrumental period