Exploring the role of hydrological pathways in modulating North Atlantic Oscillation (NAO) teleconnection periodicities from UK rainfall to streamflow

Abstract

Abstract. An understanding of multi-annual behaviour in streamflow allows for better estimation of the risks associated with hydrological extremes. This is can enable improved preparedness for streamflow-dependant services such as freshwater ecology, drinking water supply and agriculture. Recently, efforts have focused on detecting relationships between long-term hydrological behaviour and oscillatory climate systems (such as the NAO). For instance, the approximate 7-year periodicity of the NAO has been detected in groundwater level records in the North Atlantic region, providing a degree of forecasting for future water resource extremes due to their repeating, periodic nature. However, the extent to which these 7-year NAO-like signals are propagated to streamflow, and the catchment processes that modulate this propagation, are currently unknown. Here, we show statistically significant evidence that these 7-year periodicities are present in streamflow (and associated catchment rainfall), by applying multi-resolution analysis to a large dataset of streamflow and associated catchment rainfall across the UK. Our results provide new evidence for spatial patterns of NAO periodicities in UK rainfall with areas of greatest NAO signal found in south west England, South Wales, Northern Ireland and central Scotland, and that NAO-like periodicities account for a greater proportion of streamflow variability in these areas. Furthermore, we show that subsurface pathway contribution, as characterised by the Baseflow Index (BFI), and the response times of subsurface pathways, as characterised by Groundwater response Time (GRT), are influential factors for streamflow sensitivity to these NAO-like cycles. Our results provide critical process understanding for the screening and use of streamflow teleconnections for the improving the practice and policy of long-term streamflow resource management.

Monthly Rainfall Signatures of the North Atlantic Oscillation and East Atlantic Pattern in Great Britain

“…Although it should be noted that NAOI-rainfall correlations can be sensitive to the method of NAOI calculation, notably the choice between indices derived from station-measured or modelled SLP data [14]. Additionally, studies have explored how these NAO-rainfall deviations variably propagate through catchments to influence streamflow [6,[15][16][17], groundwater [18,19] and fluvial water temperatures [20].…”

Non‐stationary control of the NAO on European rainfall and its implications for water resource management

“…Many studies have investigated the relationship between the NAO Index (NAOI) and recorded hydrological variables in Europe, including river flow (Burt & Howden, 2013), groundwater (Lavers et al, 2015), and seasonal rainfall (West et al, 2019), or calculated water resource variables such as the standardized precipitation index (Moreira et al, 2016). Furthermore, a growing number of studies have detected multi-annual periodicities in hydrological variables river flow and rainfall (Rust et al, 2020), and groundwater level (Neves et al, 2019) that align with weak periodicities detected in the NAOI (Hurrell & Loon, 1997), suggesting that multi-annual cycles in the NAO may affect the occurrence of floods and droughts in Western Europe.…”

The importance of non-stationary multiannual periodicities in the NAO index for forecasting water resource extremes

“…Furthermore, Liesch and Wunsch (2019) found significant coherence between NAOI and groundwater level at approximately 6-to 16-year periodicities across the UK, Germany, Netherlands and Denmark. Rust et al (2019;2021a) identified a similar significant 6-to 9-year cycle across a large dataset of groundwater level (59 boreholes) and streamflow (705 gauges) in the UK, which was associated with the principal periodicity of the NAO (of a similar length (Hurrell et al, 2003;Zhang et al, 2011)).…”

“…al, 2019; Uvo et al, 2021), than at an annual scale. This is particularly apparent where longer hydrological response times predominate (Rust et al 2021a). For instance, Neves et al (2019) identified significant relationships between the NAOI and groundwater level in Portuguese aquifers and at approximately 6-and 10-year periodicities, with associations to episodes of recorded groundwater drought.…”