Modelling this, like modeling the rate of future glacial melt, may be close to impossible and when it's written about, it can sound more alarmist than science, so it's a subject that has 2 key problems, difficult to predict (even in the hard to predict climate change models the effect of salinity changes on ocean currents are especially tricky), and it's the kind of thing that might invite shouts from the other side, like Wiesław Masłowski's infamous study that suggested the arctic might be ice-free by 2013. He was a graduate student, not a climate scientist and his was a good study and preliminary. It should have been subject to peer review, instead, (in part because Al Gore used his study in a speech), it became a famous example to alarmism and was subject to much ridicule that persists to this day.
Scientists are certainly aware of the possible effects of salinity changes and the effect that might have on ocean currents, but it's very difficult to model and mostly written about observed effects in the present, and mostly not written regarding future forecasts. The difficulty Predictions like "the Atlantic current could shut down" may be based in makingscience, but low probability predictions like that kind of forecast and the other side shouting "wrong" at you are likely two reasons why this effect is mostly studied in the present where it's based entirely on observation not forecasttend to invite criticism.
It's talked aboutFresh water/ice melt is discussed in Wikipedia here and here's an article where the opposite is happening. As arctic sea ice receedsrecedes, the lighter, less salty water on top isn't present as much as it used to be and the arctic-ocean stratification is going away. Article on that here.
It's also worth noting that glacier fed rivers will affect the ecosystem down-river, putting less or more water into the environment leading to less or more greening and less or more water evaporating off the river into the atmosphere. It's more common for rivers to be fed by snow melt than glacial melt, but the glacial melt should be studied too. Changes in greening down-river and in atmospheric water vapor also effect climate, so, as someone said in the comments, there are a whole lot of moving parts to the climate picture. Generally
Generally speaking, the scientists are aware of all of this and as much as possible, study it and include it in models.