diff --git a/.cirrus.yml b/.cirrus.yml
deleted file mode 100644
index cbc8a146ef..0000000000
--- a/.cirrus.yml
+++ /dev/null
@@ -1,198 +0,0 @@
-# Reference:
-#   - https://cirrus-ci.org/guide/writing-tasks/
-#   - https://cirrus-ci.org/guide/writing-tasks/#environment-variables
-#   - https://cirrus-ci.org/guide/tips-and-tricks/#sharing-configuration-between-tasks
-#   - https://cirrus-ci.org/guide/linux/
-#   - https://hub.docker.com/_/gcc/
-#   - https://hub.docker.com/_/python/
-
-#
-# Global defaults.
-#
-container:
-  image: gcc:latest
-  cpu: 2
-  memory: 4G
-
-
-env:
-  # Skip specific tasks by name. Set to a non-empty string to skip.
-  SKIP_LINT_TASK: ""
-  SKIP_TEST_TASK: ""
-  SKIP_DOCTEST_TASK: ""
-  SKIP_LINKCHECK_TASK: ""
-  # Skip task groups by type. Set to a non-empty string to skip.
-  SKIP_ALL_DOC_TASKS: ""
-  # Maximum cache period (in weeks) before forcing a new cache upload.
-  CACHE_PERIOD: "2"
-  # Increment the build number to force new cartopy cache upload.
-  CARTOPY_CACHE_BUILD: "3"
-  # Increment the build number to force new conda cache upload.
-  CONDA_CACHE_BUILD: "0"
-  # Increment the build number to force new nox cache upload.
-  NOX_CACHE_BUILD: "2"
-  # Increment the build number to force new pip cache upload.
-  PIP_CACHE_BUILD: "0"
-  # Pip packages to be upgraded/installed.
-  PIP_CACHE_PACKAGES: "nox pip pyyaml setuptools wheel"
-  # Conda packages to be installed.
-  CONDA_CACHE_PACKAGES: "nox pip"
-  # Git commit hash for iris test data.
-  IRIS_TEST_DATA_VERSION: "2.9"
-  # Base directory for the iris-test-data.
-  IRIS_TEST_DATA_DIR: ${HOME}/iris-test-data
-
-
-#
-# YAML alias for common linux test infra-structure.
-#
-linux_task_template: &LINUX_TASK_TEMPLATE
-  auto_cancellation: true
-  env:
-    PATH: ${HOME}/miniconda/bin:${PATH}
-    SITE_CFG: ${CIRRUS_WORKING_DIR}/lib/iris/etc/site.cfg
-  conda_cache:
-    folder: ${HOME}/miniconda
-    fingerprint_script:
-      - wget --quiet https://repo.continuum.io/miniconda/Miniconda3-latest-Linux-x86_64.sh -O miniconda.sh
-      - echo "${CIRRUS_OS} $(sha256sum miniconda.sh)"
-      - echo "${CONDA_CACHE_PACKAGES}"
-      - echo "$(date +%Y).$(expr $(date +%U) / ${CACHE_PERIOD}):${CONDA_CACHE_BUILD}"
-      - uname -r
-    populate_script:
-      - bash miniconda.sh -b -p ${HOME}/miniconda
-      - conda config --set always_yes yes --set changeps1 no
-      - conda config --set show_channel_urls True
-      - conda config --add channels conda-forge
-      - conda update --quiet --name base conda
-      - conda install --quiet --name base ${CONDA_CACHE_PACKAGES}
-  cartopy_cache:
-    folder: ${HOME}/.local/share/cartopy
-    fingerprint_script:
-      - echo "${CIRRUS_OS}"
-      - echo "$(date +%Y).$(expr $(date +%U) / ${CACHE_PERIOD}):${CARTOPY_CACHE_BUILD}"
-    populate_script:
-      - conda create --quiet --name cartopy-cache cartopy
-      - source ${HOME}/miniconda/etc/profile.d/conda.sh >/dev/null 2>&1
-      - conda activate cartopy-cache >/dev/null 2>&1
-      - cd $(mktemp -d)
-      - wget --quiet https://raw.githubusercontent.com/SciTools/cartopy/v0.20.0/tools/cartopy_feature_download.py
-      - python cartopy_feature_download.py physical --output ${HOME}/.local/share/cartopy --no-warn
-      - conda deactivate >/dev/null 2>&1
-  nox_cache:
-    folder: ${CIRRUS_WORKING_DIR}/.nox
-    reupload_on_changes: true
-    fingerprint_script:
-      - echo "${CIRRUS_TASK_NAME}"
-      - echo "${NOX_CACHE_BUILD}"
-
-
-#
-# YAML alias for compute credits.
-#
-compute_credits_template: &CREDITS_TEMPLATE
-  # Restrict where compute credits are used.
-  use_compute_credits: ${CIRRUS_REPO_FULL_NAME} == "SciTools/iris" && ${CIRRUS_USER_COLLABORATOR} == "true" && ${CIRRUS_PR_DRAFT} == "false" && ${CIRRUS_PR} != ""
-
-
-#
-# YAML alias for the iris-test-data cache.
-#
-iris_test_data_template: &IRIS_TEST_DATA_TEMPLATE
-  data_cache:
-    folder: ${IRIS_TEST_DATA_DIR}
-    fingerprint_script:
-      - echo "iris-test-data v${IRIS_TEST_DATA_VERSION}"
-    populate_script:
-      - wget --quiet https://github.com/SciTools/iris-test-data/archive/v${IRIS_TEST_DATA_VERSION}.zip -O iris-test-data.zip
-      - unzip -q iris-test-data.zip
-      - mv iris-test-data-${IRIS_TEST_DATA_VERSION} ${IRIS_TEST_DATA_DIR}
-
-
-#
-# Linting
-#
-task:
-  only_if: ${SKIP_LINT_TASK} == ""
-  << : *CREDITS_TEMPLATE
-  auto_cancellation: true
-  container:
-    image: python:3.8
-    cpu: 2
-    memory: 4G
-  name: "${CIRRUS_OS}: pre-commit hooks"
-  pip_cache:
-    folder: ~/.cache/pip
-    fingerprint_script:
-      - echo "${CIRRUS_TASK_NAME} py${PYTHON_VERSION}"
-      - echo "$(date +%Y).$(expr $(date +%U) / ${CACHE_PERIOD}):${PIP_CACHE_BUILD} ${PIP_CACHE_PACKAGES}"
-  precommit_script:
-    - pip list
-    - python -m pip install --retries 3 --upgrade ${PIP_CACHE_PACKAGES}
-    - pip list
-    - nox --session precommit
-
-
-#
-# Testing (Linux)
-#
-task:
-  only_if: ${SKIP_TEST_TASK} == ""
-  << : *CREDITS_TEMPLATE
-  matrix:
-    env:
-      PY_VER: 3.8
-  name: "${CIRRUS_OS}: py${PY_VER} tests"
-  container:
-    image: gcc:latest
-    cpu: 6
-    memory: 8G
-  << : *IRIS_TEST_DATA_TEMPLATE
-  << : *LINUX_TASK_TEMPLATE
-  tests_script:
-    - echo "[Resources]" > ${SITE_CFG}
-    - echo "test_data_dir = ${IRIS_TEST_DATA_DIR}/test_data" >> ${SITE_CFG}
-    - echo "doc_dir = ${CIRRUS_WORKING_DIR}/docs" >> ${SITE_CFG}
-    - nox --session tests -- --verbose
-
-
-#
-# Documentation Testing and Gallery (Linux)
-#
-task:
-  only_if: ${SKIP_DOCTEST_TASK} == "" && ${SKIP_ALL_DOC_TASKS} == ""
-  << : *CREDITS_TEMPLATE
-  env:
-    PY_VER: 3.8
-    MPL_RC_DIR: ${HOME}/.config/matplotlib
-    MPL_RC_FILE: ${HOME}/.config/matplotlib/matplotlibrc
-  name: "${CIRRUS_OS}: py${PY_VER} doctests and gallery"
-  << : *IRIS_TEST_DATA_TEMPLATE
-  << : *LINUX_TASK_TEMPLATE
-  tests_script:
-    - echo "[Resources]" > ${SITE_CFG}
-    - echo "test_data_dir = ${IRIS_TEST_DATA_DIR}/test_data" >> ${SITE_CFG}
-    - echo "doc_dir = ${CIRRUS_WORKING_DIR}/docs" >> ${SITE_CFG}
-    - mkdir -p ${MPL_RC_DIR}
-    - echo "backend : agg" > ${MPL_RC_FILE}
-    - echo "image.cmap : viridis" >> ${MPL_RC_FILE}
-    - nox --session doctest -- --verbose
-
-
-#
-# Documentation Link Check (Linux)
-#
-task:
-  only_if: ${SKIP_LINKCHECK_TASK} == "" && ${SKIP_ALL_DOC_TASKS} == ""
-  << : *CREDITS_TEMPLATE
-  env:
-    PY_VER: 3.8
-    MPL_RC_DIR: ${HOME}/.config/matplotlib
-    MPL_RC_FILE: ${HOME}/.config/matplotlib/matplotlibrc
-  name: "${CIRRUS_OS}: py${PY_VER} link check"
-  << : *LINUX_TASK_TEMPLATE
-  tests_script:
-    - mkdir -p ${MPL_RC_DIR}
-    - echo "backend : agg" > ${MPL_RC_FILE}
-    - echo "image.cmap : viridis" >> ${MPL_RC_FILE}
-    - nox --session linkcheck -- --verbose
diff --git a/.github/workflows/ci-docs-linkcheck.yml b/.github/workflows/ci-docs-linkcheck.yml
new file mode 100644
index 0000000000..cf67e99129
--- /dev/null
+++ b/.github/workflows/ci-docs-linkcheck.yml
@@ -0,0 +1,94 @@
+# reference:
+#   - https://github.com/actions/cache
+#   - https://github.com/actions/checkout
+#   - https://github.com/marketplace/actions/setup-miniconda
+
+name: ci-docs-linkcheck
+
+on:
+  push:
+    branches:
+      - "main"
+      - "v*x"
+    tags:
+      - "v*"
+  pull_request:
+    branches:
+      - "*"
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  tests:
+    name: "linkcheck ${{ matrix.os }} ${{ matrix.python-version }}"
+
+    runs-on: ${{ matrix.os }}
+
+    defaults:
+      run:
+        shell: bash -l {0}
+
+    strategy:
+      matrix:
+        os: ["ubuntu-latest"]
+        python-version: ["3.8"]
+
+    env:
+      ENV_NAME: "ci-docs-linkcheck"
+
+    steps:
+      - name: "checkout"
+        uses: actions/checkout@v3
+
+      - name: "environment configure"
+        env:
+          # Maximum cache period (in weeks) before forcing a cache refresh.
+          CACHE_WEEKS: 2
+        run: |
+          echo "CACHE_PERIOD=$(date +%Y).$(expr $(date +%U) / ${CACHE_WEEKS})" >> ${GITHUB_ENV}
+          echo "LOCK_FILE=requirements/ci/nox.lock/py$(echo ${{ matrix.python-version }} | tr -d '.')-linux-64.lock" >> ${GITHUB_ENV}
+
+      - name: "conda package cache"
+        uses: ./.github/workflows/composite/conda-pkg-cache
+        with:
+          cache_build: 0
+          cache_period: ${{ env.CACHE_PERIOD }}
+          env_name: ${{ env.ENV_NAME }}
+
+      - name: "conda install"
+        uses: conda-incubator/setup-miniconda@v2
+        with:
+          miniforge-version: latest
+          channels: conda-forge,defaults
+          activate-environment: ${{ env.ENV_NAME }}
+          auto-update-conda: false
+          use-only-tar-bz2: true
+
+      - name: "conda environment cache"
+        uses: ./.github/workflows/composite/conda-env-cache
+        with:
+          cache_build: 0
+          cache_period: ${{ env.CACHE_PERIOD }}
+          env_name: ${{ env.ENV_NAME }}
+          install_packages: "nox pip"
+
+      - name: "conda info"
+        run: |
+          conda info
+          conda list
+
+      - name: "nox cache"
+        uses: ./.github/workflows/composite/nox-cache
+        with:
+          cache_build: 0
+          env_name: ${{ env.ENV_NAME }}
+          lock_file: ${{ env.LOCK_FILE }}
+
+      - name: "iris linkcheck"
+        env:
+          PY_VER: ${{ matrix.python-version }}
+        run: |
+          nox --session linkcheck -- --verbose
diff --git a/.github/workflows/ci-docs-tests.yml b/.github/workflows/ci-docs-tests.yml
new file mode 100644
index 0000000000..faadf56204
--- /dev/null
+++ b/.github/workflows/ci-docs-tests.yml
@@ -0,0 +1,127 @@
+# reference:
+#   - https://github.com/actions/cache
+#   - https://github.com/actions/checkout
+#   - https://github.com/marketplace/actions/setup-miniconda
+
+name: ci-docs-tests
+
+on:
+  push:
+    branches:
+      - "main"
+      - "v*x"
+    tags:
+      - "v*"
+  pull_request:
+    branches:
+      - "*"
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  tests:
+    name: "doctests ${{ matrix.os }} ${{ matrix.python-version }}"
+
+    runs-on: ${{ matrix.os }}
+
+    defaults:
+      run:
+        shell: bash -l {0}
+
+    strategy:
+      matrix:
+        os: ["ubuntu-latest"]
+        python-version: ["3.8"]
+
+    env:
+      IRIS_TEST_DATA_VERSION: "2.9"
+      ENV_NAME: "ci-docs-tests"
+
+    steps:
+      - name: "checkout"
+        uses: actions/checkout@v3
+
+      - name: "environment configure"
+        env:
+          # Maximum cache period (in weeks) before forcing a cache refresh.
+          CACHE_WEEKS: 2
+        run: |
+          echo "CACHE_PERIOD=$(date +%Y).$(expr $(date +%U) / ${CACHE_WEEKS})" >> ${GITHUB_ENV}
+          echo "LOCK_FILE=requirements/ci/nox.lock/py$(echo ${{ matrix.python-version }} | tr -d '.')-linux-64.lock" >> ${GITHUB_ENV}
+
+      - name: "data cache"
+        uses: ./.github/workflows/composite/iris-data-cache
+        with:
+          cache_build: 0
+          env_name: ${{ env.ENV_NAME }}
+          version: ${{ env.IRIS_TEST_DATA_VERSION }}
+
+      - name: "conda package cache"
+        uses: ./.github/workflows/composite/conda-pkg-cache
+        with:
+          cache_build: 0
+          cache_period: ${{ env.CACHE_PERIOD }}
+          env_name: ${{ env.ENV_NAME }}
+
+      - name: "conda install"
+        uses: conda-incubator/setup-miniconda@v2
+        with:
+          miniforge-version: latest
+          channels: conda-forge,defaults
+          activate-environment: ${{ env.ENV_NAME }}
+          auto-update-conda: false
+          use-only-tar-bz2: true
+
+      - name: "conda environment cache"
+        uses: ./.github/workflows/composite/conda-env-cache
+        with:
+          cache_build: 0
+          cache_period: ${{ env.CACHE_PERIOD }}
+          env_name: ${{ env.ENV_NAME }}
+          install_packages: "cartopy nox pip"
+
+      - name: "conda info"
+        run: |
+          conda info
+          conda list
+
+      - name: "cartopy cache"
+        uses: ./.github/workflows/composite/cartopy-cache
+        with:
+          cache_build: 0
+          cache_period: ${{ env.CACHE_PERIOD }}
+          env_name: ${{ env.ENV_NAME }}
+
+      - name: "nox cache"
+        uses: ./.github/workflows/composite/nox-cache
+        with:
+          cache_build: 0
+          env_name: ${{ env.ENV_NAME }}
+          lock_file: ${{ env.LOCK_FILE }}
+
+      # TODO: drop use of site.cfg and explicit use of mplrc
+      - name: "iris configure"
+        env:
+          SITE_CFG: lib/iris/etc/site.cfg
+          MPL_RC: ${HOME}/.config/matplotlib/matplotlibrc
+        run: |
+          mkdir -p $(dirname ${SITE_CFG})
+          echo ${SITE_CFG}
+          echo "[Resources]" >> ${SITE_CFG}
+          echo "test_data_dir = ${HOME}/iris-test-data/test_data" >> ${SITE_CFG}
+          echo "doc_dir = ${GITHUB_WORKSPACE}/docs" >> ${SITE_CFG}
+          cat ${SITE_CFG}
+          mkdir -p $(dirname ${MPL_RC})
+          echo ${MPL_RC}
+          echo "backend : agg" >> ${MPL_RC}
+          echo "image.cmap : viridis" >> ${MPL_RC} 
+          cat ${MPL_RC}
+
+      - name: "iris doctests and gallery"
+        env:
+          PY_VER: ${{ matrix.python-version }}
+        run: |
+          nox --session doctest -- --verbose
diff --git a/.github/workflows/ci-tests.yml b/.github/workflows/ci-tests.yml
new file mode 100644
index 0000000000..fbe738067c
--- /dev/null
+++ b/.github/workflows/ci-tests.yml
@@ -0,0 +1,122 @@
+# reference:
+#   - https://github.com/actions/cache
+#   - https://github.com/actions/checkout
+#   - https://github.com/marketplace/actions/setup-miniconda
+
+name: ci-tests 
+
+on:
+  push:
+    branches:
+      - "main"
+      - "v*x"
+    tags:
+      - "v*"
+  pull_request:
+    branches:
+      - "*"
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  tests:
+    name: "tests ${{ matrix.os }} ${{ matrix.python-version }}"
+
+    runs-on: ${{ matrix.os }}
+
+    defaults:
+      run:
+        shell: bash -l {0}
+
+    strategy:
+      fail-fast: false
+      matrix:
+        os: ["ubuntu-latest"]
+        python-version: ["3.8"]
+
+    env:
+      IRIS_TEST_DATA_VERSION: "2.9"
+      ENV_NAME: "ci-tests"
+
+    steps:
+      - name: "checkout"
+        uses: actions/checkout@v3
+
+      - name: "environment configure"
+        env:
+          # Maximum cache period (in weeks) before forcing a cache refresh.
+          CACHE_WEEKS: 2
+        run: |
+          echo "CACHE_PERIOD=$(date +%Y).$(expr $(date +%U) / ${CACHE_WEEKS})" >> ${GITHUB_ENV}
+          echo "LOCK_FILE=requirements/ci/nox.lock/py$(echo ${{ matrix.python-version }} | tr -d '.')-linux-64.lock" >> ${GITHUB_ENV}
+
+      - name: "data cache"
+        uses: ./.github/workflows/composite/iris-data-cache
+        with:
+          cache_build: 0
+          env_name: ${{ env.ENV_NAME }}
+          version: ${{ env.IRIS_TEST_DATA_VERSION }}
+
+      - name: "conda package cache"
+        uses: ./.github/workflows/composite/conda-pkg-cache
+        with:
+          cache_build: 0
+          cache_period: ${{ env.CACHE_PERIOD }}
+          env_name: ${{ env.ENV_NAME }}
+
+      - name: "conda install"
+        uses: conda-incubator/setup-miniconda@v2
+        with:
+          miniforge-version: latest
+          channels: conda-forge,defaults
+          activate-environment: ${{ env.ENV_NAME }}
+          auto-update-conda: false
+          use-only-tar-bz2: true
+
+      - name: "conda environment cache"
+        uses: ./.github/workflows/composite/conda-env-cache
+        with:
+          cache_build: 0
+          cache_period: ${{ env.CACHE_PERIOD }}
+          env_name: ${{ env.ENV_NAME }}
+          install_packages: "cartopy nox pip"
+
+      - name: "conda info"
+        run: |
+          conda info
+          conda list
+
+      - name: "cartopy cache"
+        uses: ./.github/workflows/composite/cartopy-cache
+        with:
+          cache_build: 0
+          cache_period: ${{ env.CACHE_PERIOD }}
+          env_name: ${{ env.ENV_NAME }}
+
+      - name: "nox cache"
+        uses: ./.github/workflows/composite/nox-cache
+        with:
+          cache_build: 0
+          env_name: ${{ env.ENV_NAME }}
+          lock_file: ${{ env.LOCK_FILE }}
+
+      # TODO: drop use of site.cfg and explicit use of mplrc
+      - name: "iris configure"
+        env:
+          SITE_CFG: lib/iris/etc/site.cfg
+        run: |
+          mkdir -p $(dirname ${SITE_CFG})
+          echo ${SITE_CFG}
+          echo "[Resources]" >> ${SITE_CFG}
+          echo "test_data_dir = ${HOME}/iris-test-data/test_data" >> ${SITE_CFG}
+          echo "doc_dir = ${GITHUB_WORKSPACE}/docs" >> ${SITE_CFG}
+          cat ${SITE_CFG}
+
+      - name: "iris tests"
+        env:
+          PY_VER: ${{ matrix.python-version }}
+        run: |
+          nox --session tests -- --verbose
diff --git a/.github/workflows/composite/cartopy-cache/action.yml b/.github/workflows/composite/cartopy-cache/action.yml
new file mode 100644
index 0000000000..35a90736bc
--- /dev/null
+++ b/.github/workflows/composite/cartopy-cache/action.yml
@@ -0,0 +1,34 @@
+name: "cartopy-cache"
+description: "create and cache cartopy assets"
+
+inputs:
+  cache_build:
+    description: "conda environment cache build number"
+    required: false
+    default: "0"
+  cache_period:
+    description: "conda environment cache timestamp"
+    required: true
+  env_name:
+    description: "environment name"
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - uses: actions/cache@v3
+      id: cartopy-cache
+      with:
+        path: ~/.local/share/cartopy
+        key: ${{ runner.os }}-cartopy-${{ inputs.env_name }}-p${{ inputs.cache_period }}-b${{ inputs.cache_build }}
+
+    - if: steps.cartopy-cache.outputs.cache-hit != 'true'
+      env:
+        CARTOPY_SHARE_DIR: ~/.local/share/cartopy
+        CARTOPY_FEATURE: https://raw.githubusercontent.com/SciTools/cartopy/v0.20.0/tools/cartopy_feature_download.py
+      shell: bash
+      run: |
+        wget --quiet ${CARTOPY_FEATURE}
+        mkdir -p ${CARTOPY_SHARE_DIR}
+        # Requires a pre-installed version of cartopy within the environment.
+        python cartopy_feature_download.py physical --output ${CARTOPY_SHARE_DIR} --no-warn
diff --git a/.github/workflows/composite/conda-env-cache/action.yml b/.github/workflows/composite/conda-env-cache/action.yml
new file mode 100644
index 0000000000..6bfd6fff90
--- /dev/null
+++ b/.github/workflows/composite/conda-env-cache/action.yml
@@ -0,0 +1,35 @@
+name: "conda-env-cache"
+description: "create and cache the conda environment"
+
+#
+# Assumes the environment contains the following variables:
+#   - CONDA
+#
+inputs:
+  cache_build:
+    description: "conda environment cache build number"
+    required: false
+    default: "0"
+  cache_period:
+    description: "conda environment cache timestamp"
+    required: true
+  env_name:
+    description: "environment name"
+    required: true
+  install_packages:
+    description: "conda packages to install into environment"
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - uses: actions/cache@v3
+      id: conda-env-cache
+      with:
+        path: ${{ env.CONDA }}/envs/${{ inputs.env_name }}
+        key: ${{ runner.os }}-conda-env-${{ inputs.env_name }}-p${{ inputs.cache_period }}-b${{ inputs.cache_build }}
+
+    - if: steps.conda-env-cache.outputs.cache-hit != 'true'
+      shell: bash
+      run: |
+        conda install --quiet --name ${{ inputs.env_name }} ${{ inputs.install_packages }}
diff --git a/.github/workflows/composite/conda-pkg-cache/action.yml b/.github/workflows/composite/conda-pkg-cache/action.yml
new file mode 100644
index 0000000000..4472d7e415
--- /dev/null
+++ b/.github/workflows/composite/conda-pkg-cache/action.yml
@@ -0,0 +1,22 @@
+name: "conda-pkg-cache"
+description: "cache the conda environment packages"
+
+inputs:
+  cache_build:
+    description: "conda environment cache build number"
+    required: false
+    default: "0"
+  cache_period:
+    description: "conda environment cache timestamp"
+    required: true
+  env_name:
+    description: "environment name"
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - uses: actions/cache@v3
+      with:
+        path: ~/conda_pkgs_dir
+        key: ${{ runner.os }}-conda-pkgs-${{ inputs.env_name }}-p${{ inputs.cache_period }}-b${{ inputs.cache_build }}
diff --git a/.github/workflows/composite/iris-data-cache/action.yml b/.github/workflows/composite/iris-data-cache/action.yml
new file mode 100644
index 0000000000..7bf72fae8b
--- /dev/null
+++ b/.github/workflows/composite/iris-data-cache/action.yml
@@ -0,0 +1,30 @@
+name: "iris-data-cache"
+description: "create and cache the iris test data"
+
+inputs:
+  cache_build:
+    description: "data cache build number"
+    required: false
+    default: "0"
+  env_name:
+    description: "environment name"
+    required: true
+  version:
+    description: "iris test data version"
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - uses: actions/cache@v3
+      id: data-cache
+      with:
+        path: ~/iris-test-data
+        key: ${{ runner.os }}-iris-test-data-${{ inputs.env_name }}-v${{ inputs.version }}-b${{ inputs.cache_build }}
+
+    - if: steps.data-cache.outputs.cache-hit != 'true'
+      shell: bash
+      run: |
+        wget --quiet https://github.com/SciTools/iris-test-data/archive/v${{ inputs.version }}.zip -O iris-test-data.zip
+        unzip -q iris-test-data.zip
+        mv iris-test-data-${{ inputs.version }} ~/iris-test-data
diff --git a/.github/workflows/composite/nox-cache/action.yml b/.github/workflows/composite/nox-cache/action.yml
new file mode 100644
index 0000000000..9d92ad7226
--- /dev/null
+++ b/.github/workflows/composite/nox-cache/action.yml
@@ -0,0 +1,22 @@
+name: "nox cache"
+description: "cache the nox test environments"
+
+inputs:
+  cache_build:
+    description: "nox cache build number"
+    required: false
+    default: "0"
+  env_name:
+    description: "environment name"
+    required: true
+  lock_file:
+    description: "conda-lock environment requirements filename"
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - uses: actions/cache@v3
+      with:
+        path: ${{ github.workspace }}/.nox
+        key: ${{ runner.os }}-nox-${{ inputs.env_name }}-py${{ matrix.python-version }}-b${{ inputs.cache_build }}-${{ hashFiles(inputs.lock_file) }}
diff --git a/.github/workflows/refresh-lockfiles.yml b/.github/workflows/refresh-lockfiles.yml
index 1f41c8c265..f93858e03d 100644
--- a/.github/workflows/refresh-lockfiles.yml
+++ b/.github/workflows/refresh-lockfiles.yml
@@ -93,7 +93,11 @@ jobs:
           body: |
             Lockfiles updated to the latest resolvable environment.
 
-            If the CI test suite fails, create a new branch based of this pull request and add the required fixes to that branch.
+            ### If the CI tasks fail, create a new branch based on this PR and add the required fixes to that branch.
+
+            ### If the PR CI tasks have not run, please close and re-open this PR to trigger them.
+
+            Reference: create-pull-request GHA [triggering further workflow runs](https://github.com/peter-evans/create-pull-request/blob/main/docs/concepts-guidelines.md#triggering-further-workflow-runs)
           labels: |
             New: Pull Request
             Bot
diff --git a/docs/src/whatsnew/latest.rst b/docs/src/whatsnew/latest.rst
index e7edafb58d..ff737d104a 100644
--- a/docs/src/whatsnew/latest.rst
+++ b/docs/src/whatsnew/latest.rst
@@ -210,6 +210,9 @@ This document explains the changes made to Iris for this release
 #. `@wjbenfold`_ made :func:`iris.tests.stock.simple_1d` respect the
    ``with_bounds`` argument. (:pull:`4658`)
 
+#. `@bjlittle`_ migrated to GitHub Actions for Continuous-Integration.
+   (:pull:`4503`)
+
 
 .. comment
     Whatsnew author names (@github name) in alphabetical order. Note that,
@@ -222,4 +225,4 @@ This document explains the changes made to Iris for this release
     Whatsnew resources in alphabetical order:
 
 .. _Cell Boundaries: https://cfconventions.org/Data/cf-conventions/cf-conventions-1.9/cf-conventions.html#cell-boundaries
-.. _PyData Sphinx Theme: https://pydata-sphinx-theme.readthedocs.io/en/stable/index.html
\ No newline at end of file
+.. _PyData Sphinx Theme: https://pydata-sphinx-theme.readthedocs.io/en/stable/index.html
diff --git a/noxfile.py b/noxfile.py
index 7919dfdfde..0de7b3a63c 100755
--- a/noxfile.py
+++ b/noxfile.py
@@ -173,41 +173,6 @@ def prepare_venv(session: nox.sessions.Session) -> None:
         )
 
 
-@nox.session
-def precommit(session: nox.sessions.Session):
-    """
-    Perform pre-commit hooks of iris codebase.
-
-    Parameters
-    ----------
-    session: object
-        A `nox.sessions.Session` object.
-
-    """
-    import yaml
-
-    # Pip install the session requirements.
-    session.install("pre-commit")
-
-    # Load the pre-commit configuration YAML file.
-    with open(".pre-commit-config.yaml", "r") as fi:
-        config = yaml.load(fi, Loader=yaml.FullLoader)
-
-    # List of pre-commit hook ids that we don't want to run.
-    excluded = ["no-commit-to-branch"]
-
-    # Enumerate the ids of pre-commit hooks we do want to run.
-    ids = [
-        hook["id"]
-        for entry in config["repos"]
-        for hook in entry["hooks"]
-        if hook["id"] not in excluded
-    ]
-
-    # Execute the pre-commit hooks.
-    [session.run("pre-commit", "run", "--all-files", id) for id in ids]
-
-
 @nox.session(python=PY_VER, venv_backend="conda")
 def tests(session: nox.sessions.Session):
     """