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Cometary activity may be driven by ices with very low sublimationtemperatures, such as carbon monoxide ice, which can sublimate at distanceswell beyond 20 au. This point is emphasized by the discovery of Oort cloudcomet C/2014 UN$_{271}$ (Bernardinelli-Bernstein), and its observed activityout to $\sim$26 au. Through observations of this comet's optical brightness andbehavior, we can potentially discern the drivers of activity in the outer solarsystem. We present a study of the activity of comet Bernardinelli-Bernsteinwith broad-band optical photometry taken at 19-20 au from the Sun (2021 June to2022 February) as part of the LCO Outbursting Objects Key (LOOK) Project. Ouranalysis shows that the comet's optical brightness during this period wasinitially dominated by cometary outbursts, stochastic events that ejected$\sim10^7$ to $\sim10^8$ kg of material on short (< 1 day) timescales. Wepresent evidence for three such outbursts occurring in 2021 June and September.The nominal nuclear volumes excavated by these events are similar to the 10-100m pit-shaped voids on the surfaces of short-period comet nuclei, as imaged byspacecraft. Two out of three Oort cloud comets observed at large pre-periheliondistances exhibit outburst behavior near 20 au, suggesting such events may becommon in this population. In addition, quiescent CO-driven activity mayaccount for the brightness of the comet in 2022 January to February, but thatvariations in the cometary active area (i.e., the amount of sublimating ice)with heliocentric distance are also possible.

A LOOK at Outbursts of Comet C/2014 UN$_{271}$ (Bernardinelli-Bernstein) Near 20 au