ISN2004 height - EPSG:8089

WKT

VERTCS["ISH2004_height", 
	VDATUM["Landshaedarkerfi_Islands_2004"], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", 1.0], 
	UNIT["Meter", 1.0]]

WKT2

VERTCRS["ISH2004_height", 
	VDATUM["Landshaedarkerfi_Islands_2004"], 
	CS[vertical, 1], 
	AXIS["Gravity-related height (H)", up, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["EPSG", "8089"]]

Data from @esri/proj-codes

{
  "wkid": 8089,
  "latestWkid": 8089,
  "macro": "PE_VCS_ISH2004_HT",
  "name": "ISH2004_height",
  "wkt": "VERTCS[\"ISH2004_height\",VDATUM[\"Landshaedarkerfi_Islands_2004\"],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"ISH2004_height\",VDATUM[\"Landshaedarkerfi_Islands_2004\"],CS[vertical,1],AXIS[\"Gravity-related height (H)\",up,LENGTHUNIT[\"Meter\",1.0]],ID[\"EPSG\",\"8089\"]]",
  "description": "ISN2004 height",
  "authority": "EPSG",
  "version": "9.1(10.6.0)",
  "deprecated": "no",
  "areaname": "Iceland - onshore",
  "extent": {
    "slat": 63.24,
    "nlat": 66.62,
    "llon": -24.66,
    "rlon": -13.38
  }
}