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Abstract. We present a framework for estimating concentrations of episodicallyelevated high-temperature marine ice nucleating particles (INPs) in the seasurface microlayer and their subsequent emission into the atmosphericboundary layer. These episodic INPs have been observed in multipleship-based and coastal field campaigns, but the processes controlling theirocean concentrations and transfer to the atmosphere are not yet fullyunderstood. We use a combination of empirical constraints and simulationoutputs from an Earth system model to explore different hypotheses forexplaining the variability of INP concentrations, and the occurrence ofepisodic INPs, in the marine atmosphere. In our calculations, we examine the following two proposed oceanic sources of high-temperature INPs: heterotrophic bacteria and marine biopolymer aggregates (MBPAs). Furthermore, we assume that the emission of these INPs is determined by the production of supermicron sea spray aerosol formed from jet drops, with an entrainment probability that is described by Poisson statistics. The concentration of jet drops is derived from the number concentration of supermicron sea spray aerosol calculated from model runs. We then derive the resulting number concentrations of marine high-temperature INPs (at 253 K) in the atmospheric boundary layer and compare their variability to atmospheric observations of INP variability. Specifically, we compare against concentrations of episodically occurring high-temperature INPs observed during field campaigns in the Southern Ocean, the Equatorial Pacific, and the North Atlantic. In this case study, we evaluate our framework at 253 K because reliable observational data at this temperature are available across three different ocean regions, but suitable data are sparse at higher temperatures. We find that heterotrophic bacteria and MBPAs acting as INPs provide only apartial explanation for the observed high INP concentrations. We note,however, that there are still substantial knowledge gaps, particularlyconcerning the identity of the oceanic INPs contributing most frequently toepisodic high-temperature INPs, their specific ice nucleation activity, andthe enrichment of their concentrations during the sea–air transfer process. Therefore, targeted measurements investigating the composition of these marine INPs and drivers for their emissions are needed, ideally incombination with modeling studies focused on the potential cloud impacts ofthese high-temperature INPs. 

Abstract. Accurate estimates of calving fluxes are essential inunderstanding small-scale glacier dynamics and quantifying the contribution ofmarine-terminating glaciers to both eustatic sea-level rise (SLR) and thefreshwater budget of polar regions. Here we investigate the application ofacoustical oceanography to measure calving flux using the underwater soundsof iceberg–water impact. A combination of time-lapse photography and passiveacoustics is used to determine the relationship between the mass and impactnoise of 169 icebergs generated by subaerial calving events from Hansbreen,Svalbard. The analysis includes three major factors affecting the observednoise: (1) time dependency of the thermohaline structure, (2) variability inthe ocean depth along the waveguide and (3) reflection of impact noise fromthe glacier terminus. A correlation of 0.76 is found between the(log-transformed) kinetic energy of the falling iceberg and thecorresponding measured acoustic energy corrected for these three factors. Anerror-in-variables linear regression is applied to estimate the coefficientsof this relationship. Energy conversion coefficients for non-transformedvariables are 8×10-7 and 0.92, respectively, for themultiplication factor and exponent of the power law. This simple model canbe used to measure solid ice discharge from Hansbreen. Uncertainty in theestimate is a function of the number of calving events observed; 50 %uncertainty is expected for eight blocks dropping to 20 % and 10 %,respectively, for 40 and 135 calving events. It may be possible to lowerthese errors if the influence of different calving styles on the receivednoise spectra can be determined.