Lagrangian detection of precipitation moisture sources for an arid region in northeast Greenland: relations to the North Atlantic Oscillation, sea ice cover and temporal trend from 1979 to 2017

The Arctic and specifically northeast Greenland are known to be highly sensitive to changes in climate as a result of Arctic amplification, a process in which positive feedbacks act to amplify changes compared to the rest of the Northern Hemisphere. Due to the anthropogenic climate change, winter surface temperature in northeast Greenland have already risen by as much as 4 to 5 °C over the last 50 years. Associated with this temperature rise, precipitation is expected to increase up to 50 % in the RCP8.5 scenario because of increased evaporation from a warmer and ice-free Arctic Ocean.

In recent years, numerous palaeoclimate projects have begun working in the region with the aim of improving our understanding of how this highly sensitive region responds to a warmer world. Among others, Gina Moseley from the Institute of Geology is leading an FWF START research project aiming at constructing the first cave-based climate records for Greenland, improving our understanding of climate change during times that are beyond the limit of ice cores (Greenland caves project). However, a lack of meteorological stations within the area makes it difficult to place the palaeoclimate records in the context of present-day climate.

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Figure 1: Average of yearly ERA-Interim precipitation (1979-2018). The study region is depicted with the nine grid points located between 22.5 and 21° W and between 79.5 and 81° N. The exact location of the studied caves is (80.3745° N, 21.7419° W). Average precipitation in the study region is 207 mm per yr (95 % confidence interval of [192, 224] mm per yr).

This study aims to improve our understanding of precipitation and moisture source dynamics over a small arid region located at 80° N in northeast Greenland (Fig. 1). The origin of water vapour for precipitation over the study region is detected by a Lagrangian moisture source diagnostic, which is applied to reanalysis data from the European Centre for Medium-Range Weather Forecasts (ERA-Interim) from 1979 to 2017. While precipitation amounts are relatively constant during the year, the regional moisture sources display a strong seasonality. The most dominant winter moisture sources are the North Atlantic above 45° N and the ice-free Atlantic sector of the Arctic Ocean, while in summer the patterns shift towards local and north Eurasian continental sources. By using the K-means clustering algorithm, we classified regions according to their seasonal contribution to precipitation (Fig. 2).

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Figure 2: K-means clustering with additional manual separation. The annual cycle of moisture sources contributing to precipitation in the study region is plotted for each cluster as absolute number. The ocean (with sea ice) regions are separated from the land regions, and land regions have more transparent colours. We use two graphs for the ocean regions for readability; grey lines correspond to the missing ocean regions for comparison. Shaded areas represent the 95 % confidence interval of the mean.

During the positive phases of the North Atlantic Oscillation (NAO), evaporation and moisture transport from the Norwegian Sea are stronger, resulting in larger and more variable precipitation amounts. Testing the hypothesis that retreating sea ice will lead to an increase in moisture supply remains challenging based on our data. However, we found that moisture sources are increasing in the case of retreating sea ice for some regions, in particular in October to December. Although the annual mean surface temperature in the study region has increased by 0.7 °C per decade (95 % confidence interval [0.4, 1.0] °C per decade) according to ERA-Interim data, we do not detect any change in the amount of precipitation with the exception of autumn where precipitation increases by 8.2 [0.8, 15.5] mm per decade over the period. This increase is consistent with future predicted Arctic precipitation change. Moisture source trends for other months and regions were non-existent or small.

This interdisciplinary study has been a joint project between the Department of Atmospheric and Cryospheric Sciences and the Institute of Geology and was funded with start-up funding from the University of Innsbruck Research Centre for Climate – Cryosphere and Atmosphere and by the Austrian Science Fund (Austria) (grant no. Y 1162-N3), both to Gina E. Moseley. Lilian Schuster has also received funding from the University of Innsbruck's “Exzellenzstipendien für Doktoratskollegs” fellowship programme (grant no. 2020/GEO-37).

 

Schuster, L., Maussion, F., Langhamer, L., and Moseley, G. E.: Lagrangian detection of precipitation moisture sources for an arid region in northeast Greenland: relations to the North Atlantic Oscillation, sea ice cover, and temporal trends from 1979 to 2017, Weather Clim. Dynam., 2, 1–17, https://doi.org/10.5194/wcd-2-1-2021, 2021.


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