Carbon seal assembly

An engine comprising:

• a structure;
• a shaft operatingly mounted to the structure to rotate relative to the structure;
• a carbon seal assembly comprising:
• an annular member secured to the structure;
• an annular seal runner sealingly mounted to the shaft to rotate therewith, with the seal runner being made of a material complementary to that of the annular member for magnetic attraction therebetween;
• and
• an annular carbon seal element mounted to the annular seal runner to rotate therewith and positioned in a gap between the annular member and the annular seal runner, the annular carbon seal element having an annular wear surface abutting against a face of the annular member, a cross-sectional area of the annular carbon seal element increasing as the axial dimension of the annular seal runner decreases for at least a part of the seal.