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Glacier monitoring stations use satellite imagery and ground-based sensors to —tracktrackedtrackingtracks the rate at which ice masses are retreating. Scientists place stakes directly into the ice to —measuremeasuringmeasuredmeasurement melt at fixed points throughout the year. Because glacial meltwater feeds rivers relied upon by millions, any sustained —declinerisedecliningdeclined in ice volume raises concerns about future water —scarcityscarcescarcelyabundance.