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<p>Icelandic dust can impact the radiative budget in high-latitude regions directly by affecting light absorption and scattering and indirectly by changing the surface albedo after dust deposition. This tends to produce a positive radiative forcing. However, the limited knowledge of the spectral optical properties of Icelandic dust prevents an accurate assessment of these radiative effects. Here, the spectral single scattering albedo (SSA) and the complex refractive index (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>m</mi><mo>=</mo><mi>n</mi><mo>-</mo><mi>i</mi><mi>k</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="52pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="711d80c250952db8974b40d825581611"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-7975-2023-ie00001.svg" width="52pt" height="10pt" src="acp-23-7975-2023-ie00001.png"/></svg:svg></span></span>) of Icelandic dust from five major emission hotspots were retrieved between 370–950 <span class="inline-formula">nm</span> using online measurements of size distribution and spectral absorption (<span class="inline-formula"><i>β</i>_abs</span>) and scattering (<span class="inline-formula"><i>β</i>_sca</span>) coefficients of particles suspended in a large-scale atmospheric simulation chamber. The <span class="inline-formula">SSA(<i>λ</i>)</span> estimated from the measured <span class="inline-formula"><i>β</i>_abs</span> and <span class="inline-formula"><i>β</i>_sca</span> increased from 0.90–0.94 at 370 <span class="inline-formula">nm</span> to 0.94–0.96 at 950 <span class="inline-formula">nm</span> in Icelandic dust from the different hotspots, which falls within the range of mineral dust from northern Africa and eastern Asia. The spectral complex refractive index was retrieved by minimizing the differences between the measured <span class="inline-formula"><i>β</i>_abs</span> and <span class="inline-formula"><i>β</i>_sca</span> and those computed using the Mie theory for spherical and internally homogeneous particles, using the size distribution data as input. The real part of the complex refractive index (<span class="inline-formula"><i>n</i>(<i>λ</i>)</span>) was found to be 1.60–1.61 in the different samples and be independent of wavelength. The imaginary part (<span class="inline-formula"><i>k</i>(<i>λ</i>)</span>) was almost constant with wavelength and was found to be around 0.004 at 370 <span class="inline-formula">nm</span> and 0.002–0.003 at 950 <span class="inline-formula">nm</span>. The estimated complex refractive index was close to the initial estimates based on the mineralogical composition, also suggesting that the high magnetite content observed in Icelandic dust may contribute to its high absorption capacity in the shortwave part of the spectrum. The <span class="inline-formula"><i>k</i>(<i>λ</i>)</span> values retrieved for Icelandic dust are at the upper end of the reported range for low-latitude dust (e.g., from the Sahel). Furthermore, Icelandic dust tends to be more absorbing towards the near-infrared. In Icelandic dust, <span class="inline-formula"><i>k</i>(<i>λ</i>)</span> between 660–950 <span class="inline-formula">nm</span> was 2–8 times higher than most of the dust samples sourced in northern Africa and eastern Asia. This suggests that Icelandic dust may have a stronger positive direct radiative forcing on climate that has not been accounted for in climate predictions.</p>