Stratospheric Aerosol Injection Can Reduce Risks to Antarctic Ice Loss Depending on Injection Location and Amount.

Owing to increasing greenhouse gas emissions, the Antarctic Ice Sheet is vulnerable to rapid ice loss in the upcoming decades and centuries. This study examines the effectiveness of using stratospheric aerosol injection (SAI) that minimizes global mean temperature (GMT) change to slow projected 21st century Antarctic ice loss. We simulate 11 different SAI cases which vary by the latitudinal location(s) and the amount(s) of the injection(s) to examine the climatic response near Antarctica in each case as compared to the reference climate at the turn of the last century. We demonstrate that injecting at a single latitude in the northern hemisphere or at the Equator increases Antarctic shelf ocean temperatures pertinent to ice shelf basal melt, while injecting only in the southern hemisphere minimizes this temperature change. We use these results to analyze the results of more complex multi‐latitude injection strategies that maintain GMT at or below 1.5°C above the pre‐industrial. All these multi‐latitude cases will slow Antarctic ice loss relative to the mid‐to‐late 21st century SSP2‐4.5 emissions pathway. Yet, to avoid a GMT threshold estimated by previous studies pertaining to rapid West Antarctic ice loss (1.5°C above the pre‐industrial GMT, though large uncertainty), our study suggests SAI would need to cool about 1.0°C below this threshold and predominately inject at low southern hemisphere latitudes (∼15°S ‐ 30°S). These results highlight the complexity of factors impacting the Antarctic response to SAI and the critical role of the injection strategy in preventing future ice loss. Plain Language Summary: Large portions of the Antarctic ice sheet are imminently vulnerable to melting as global temperatures rise over the 21st century. This melt would lead to consequential sea level rise intensifying coastal flooding and causing large economic and ecological costs. One idea to slow global warming and limit such climate risks, is to deliberately cool the planet by placing reflective particles in the atmosphere to deflect sunlight before it warms the Earth's surface. This idea is called stratospheric aerosol injection (SAI). Here, our computer simulations show that Antarctic ice loss can be slowed by using SAI, however, the results depend on the location of the aerosol injection (Equator, tropics, or high latitudes). We show that putting the particles between 30°N and 30°S with the majority placed in the southern hemisphere has the best potential to slow 21st century Antarctic ice loss in our computer simulations. This study is an example of how various SAI strategies (such as, where to put these particles) can lead to very different regional climate impacts—a result that decision makers must thoroughly consider. Key Points: Antarctic atmospheric circulation responds differently to stratospheric aerosol injections that vary by amount and injection latitude(s)Changes to the coastal winds impacts surface ice accumulation and shelf ocean temperatures near ice shelvesSpecific injection strategies can slow 21st century ice loss and avoid identified thresholds pertaining to Antarctic tipping points [ABSTRACT FROM AUTHOR]