Abstract
Abstract. The Arctic Ocean 2018 (AO2018) took place in the central Arctic Ocean in August and September 2018 on the Swedish icebreaker Oden. An extensive suite of instrumentation provided detailed measurements of surface water chemistry and biology, sea ice and ocean physical and biogeochemical properties, surface exchange processes, aerosols, clouds, and the state of the atmosphere. The measurements provide important information on the coupling of the ocean and ice surface to the atmosphere and in particular to clouds. This paper provides (i) an overview of the synoptic-scale atmospheric conditions and their climatological anomaly to help interpret the process studies and put the detailed observations from AO2018 into a larger context, both spatially and temporally; (ii) a statistical analysis of the thermodynamic and near-surface meteorological conditions, boundary layer, cloud, and fog characteristics; and (iii) a comparison of the results to observations from earlier Arctic Ocean expeditions – in particular AOE1996 (Arctic Ocean Expedition 1996), SHEBA (Surface Heat Budget of the Arctic Ocean), AOE2001 (Arctic Ocean Experiment 2001), ASCOS (Arctic Summer Cloud Ocean Study), ACSE (Arctic Clouds in Summer Experiment), and AO2016 (Arctic Ocean 2016) – to provide an assessment of the representativeness of the measurements. The results show that near-surface conditions were broadly comparable to earlier experiments; however the thermodynamic vertical structure was quite different. An unusually high frequency of well-mixed boundary layers up to about 1 km depth occurred, and only a few cases of the “prototypical” Arctic summer single-layer stratocumulus deck were observed. Instead, an unexpectedly high amount of multiple cloud layers and mid-level clouds were present throughout the campaign. These differences from previous studies are related to the high frequency of cyclonic activity in the central Arctic in 2018.
Highlights
The climate in the Arctic is changing rapidly (Richter-Menge et al, 2018)
The Coupled Model Intercomparison Project 3 (CMIP3) (IPCC, 2007) and CMIP5 (IPCC, 2013) climate models agree on the warming trend in the Arctic; the model spread in surface temperature increase is much larger for the Arctic region than for other regions (Pithan and Mauritsen, 2014)
This paper summarises the meteorological conditions during Arctic Ocean 2018 (AO2018) and puts the measurements into the contexts of both the synoptic setting and the measurements from previous expeditions
Summary
The climate in the Arctic is changing rapidly (Richter-Menge et al, 2018). Arctic near-surface temperature has continuously increased over recent decades, and the warming is 2–3 times larger than the global mean (Serreze and Barry, 2011; Hartfield et al, 2018; IPCC, 2018). The Coupled Model Intercomparison Project 3 (CMIP3) (IPCC, 2007) and CMIP5 (IPCC, 2013) climate models agree on the warming trend in the Arctic; the model spread in surface temperature increase is much larger for the Arctic region than for other regions (Pithan and Mauritsen, 2014). Several intimately coupled processes are involved in creating this resilient mixed-phase cloud system: radiative cooling, turbulent mixing, ice and cloud droplet formation and growth, entrainment, and turbulent surface fluxes (Morrison et al, 2012). These clouds modulate the surface energy budget considerably (e.g. Intrieri et al, 2002; Shupe and Intrieri, 2004).
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