July 2024:
new publication:

Bayr, T., Lübbecke, J. F., & Fiedler, S. (2024). Is El Niño-Southern Oscillation a tipping element in the climate system? Geophysical Research Letters, 51, e2023GL107848. https://doi.org/10.1029/2023GL107848

Abstract:
El Niño-Southern Oscillation (ENSO) is the dominant mode of climate variability with far-reaching impacts. El Niños, the warm events, occur in different flavors. In particular extreme Eastern Pacific (EP) El Niño events are associated with heavy precipitation events and extreme droughts, thus cause large socio-economic impacts in the Pacific region and beyond. In the observational record, they are quite rare so far. Here we present experiments of one climate model, which suggests that in a warmer climate ENSO may lock-in in a different state, in which nearly each El Niño is an extreme EP El Niño. On the other hand in a colder climate ENSO may lock-in in a state with nearly no extreme EP El Niños. In both climates this would have huge consequences for the socio-economic impacts of ENSO. Against this background we raise the discussion if ENSO may be a tipping element in the climate system.

June 2024:
new publication:

Latif, M., Martin, T., & Bielke, I. (2024). Regional variation in extratropical North Atlantic air-sea interaction 1960–2020. Geophysical Research Letters, 51, e2024GL108174. https://doi.org/10.1029/2024GL108174

Abstract:
The relationship between the sea-surface temperature (SST) and air-sea heat exchange, is studied over the extratropical North Atlantic (NA) for late boreal winter during 1960–2020. This relationship provides information about the roles of atmospheric and oceanic processes in driving SST variations. We consider two regions, the central-midlatitude (35°N–50°N) and subpolar (50°N–60°N) NA. Over both regions, the atmosphere tends to drive the variations on the short interannual timescales. On the longer decadal timescales and over the central-midlatitude NA, oceanic processes tend to drive the SST anomalies that in turn influence the air-sea heat exchange. Air-sea heat exchange over the subpolar NA is mostly driven by the North Atlantic Oscillation on interannual and decadal timescales, which is the leading mode of internal atmospheric variability in winter. This study suggests that the atmosphere is more sensitive to SST over the central-midlatitude than subpolar NA.